Toxic wavelength of blue light changes as insects grow.

PubMed

Shibuya, Kazuki; Onodera, Shun; Hori, Masatoshi

2018-01-01

Short-wavelength visible light (blue light: 400-500 nm) has lethal effects on various insects, such as fruit flies, mosquitoes, and flour beetles. However, the most toxic wavelengths of blue light might differ across developmental stages. Here, we investigate how the toxicity of blue light changes with the developmental stages of an insect by irradiating Drosophila melanogaster with different wavelengths of blue light. Specifically, the lethal effect on eggs increased at shorter light wavelengths (i.e., toward 405 nm). In contrast, wavelengths from 405 to 466 nm had similar lethal effects on larvae. A wavelength of 466 nm had the strongest lethal effect on pupae; however, mortality declined as pupae grew. A wavelength of 417 nm was the most harmful to adults at low photon flux density, while 466 nm was the most harmful to adults at high photon flux density. These findings suggest that, as the morphology of D. melanogaster changes with growth, the most harmful wavelength also changes. In addition, our results indicated that reactive oxygen species influence the lethal effect of blue light. Our findings show that blue light irradiation could be used as an effective pest control method by adjusting the wavelength to target specific developmental stages.

Effective suppression of stray light in rotational coherent anti-stokes Raman spectroscopy using an angle-tuned short-wave-pass filter.

PubMed

Bohlin, Alexis; Bengtsson, Per-Erik

2010-08-01

Stray light interference is a common problem in spontaneous rotational Raman spectroscopy and rotational coherent anti-Stokes Raman spectropscopy (CARS). The reason is that the detected spectrum appears in the spectral vicinity of the probe beam wavelength, and stray light at this wavelength from optics and surfaces is hard to suppress. In this Note, efficient suppression of stray light is demonstrated for rotational CARS measurements using a commercially available short-wave-pass filter. By angle-tuning this filter with a specified cut-off wavelength at 561 nm, the cut-off wavelength could be tuned to a desired spectral position so that more than 80% transmission is achieved as close as 15 cm(-1) (approximately 0.4 nm) from the probe beam wavelength of 532.0 nm, while the intensity at this wavelength is suppressed by two orders of magnitude.

Lethal effects of short-wavelength visible light on insects.

PubMed

Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

2014-12-09

We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light.

Lethal effects of short-wavelength visible light on insects

NASA Astrophysics Data System (ADS)

Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

2014-12-01

We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light.

In vivo high-resolution cortical imaging with extended-focus optical coherence microscopy in the visible-NIR wavelength range

NASA Astrophysics Data System (ADS)

Marchand, Paul J.; Szlag, Daniel; Bouwens, Arno; Lasser, Theo

2018-03-01

Visible light optical coherence tomography has shown great interest in recent years for spectroscopic and high-resolution retinal and cerebral imaging. Here, we present an extended-focus optical coherence microscopy system operating from the visible to the near-infrared wavelength range for high axial and lateral resolution imaging of cortical structures in vivo. The system exploits an ultrabroad illumination spectrum centered in the visible wavelength range (λc = 650 nm, Δλ ˜ 250 nm) offering a submicron axial resolution (˜0.85 μm in water) and an extended-focus configuration providing a high lateral resolution of ˜1.4 μm maintained over ˜150 μm in depth in water. The system's axial and lateral resolution are first characterized using phantoms, and its imaging performance is then demonstrated by imaging the vasculature, myelinated axons, and neuronal cells in the first layers of the somatosensory cortex of mice in vivo.

Qubit transfer between photons at telecom and visible wavelengths in a slow-light atomic medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gogyan, A.

We propose a method that enables efficient conversion of the quantum information frequency between different regions of a spectrum of light based on recently demonstrated strong parametric coupling between two narrow-band single-photon pulses propagating in a slow-light atomic medium [N. Sisakyan and Yu. Malakyan, Phys. Rev. A, 75, 063831 (2007)]. We show that an input qubit at telecom wavelength is transformed into another at a visible domain in a lossless and shape-conserving manner while keeping the initial quantum coherence and entanglement. These transformations can be realized with a quantum efficiency close to its maximum value.

Elimination of coherent noise in a coherent light imaging system

NASA Technical Reports Server (NTRS)

Grebowsky, G. J.; Hermann, R. L.; Paull, H. B.; Shulman, A. R.

1970-01-01

Optical imaging systems using coherent light introduce objectionable noise into the output image plane. Dust and bubbles on and in lenses cause most of the noise in the output image. This noise usually appears as bull's-eye diffraction patterns in the image. By rotating the lens about the optical axis these diffraction patterns can be essentially eliminated. The technique does not destroy the spatial coherence of the light and permits spatial filtering of the input plane.

Wavelength-division-multiplexing method of polarized low-coherence interferometry for fiber Fabry-Perot interferometric sensors.

PubMed

Yin, Jinde; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Wang, Shuang; Wu, Fan; Ding, Zhenyang

2013-10-01

We propose a new wavelength-division-multiplexing method for extrinsic fiber Fabry-Perot interferometric (EFPI) sensing in a polarized low-coherence interferometer configuration. In the proposed method, multiple LED sources are used with different center wavelengths, and each LED is used by a specific sensing channel, and therefore the spatial frequency of the low-coherence interferogram of each channel can be separated. A bandpass filter is used to extract the low-coherence interferogram of each EFPI channel, and thus the cavity length of each EFPI channel can be identified through demultiplexing. We successfully demonstrate the simultaneous demodulation of EFPI sensors with same nominal cavity length while maintaining high measurement precision.

Coherent nonlinear coupling between a long-wavelength mode and small-scale turbulence in the TEXT tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsui, H.Y.W.; Rypdal, K.; Ritz, C.P.

1993-04-26

Bispectral analysis of Langmuir probe data indicates that coherent nonlinear coupling, in addition to the noncoherent turbulent interactions, exists in the edge plasma of the tokamak TEXT. Not all the modes involved reside within the spectral region of the usual broadband turbulence. At a major resonant surface the small-scale turbulent activity interacts [ital coherently] with a localized long-wavelength mode; a signature of regular or coherent structure. By the observed coupling to the transport related turbulence, the long-wavelength mode can influence plasma confinement indirectly. These observations signify the influence of low-order resonant surfaces on the edge turbulence in tokamaks.

Wavelength calibration of dispersive near-infrared spectrometer using relative k-space distribution with low coherence interferometer

NASA Astrophysics Data System (ADS)

Kim, Ji-hyun; Han, Jae-Ho; Jeong, Jichai

2016-05-01

The commonly employed calibration methods for laboratory-made spectrometers have several disadvantages, including poor calibration when the number of characteristic spectral peaks is low. Therefore, we present a wavelength calibration method using relative k-space distribution with low coherence interferometer. The proposed method utilizes an interferogram with a perfect sinusoidal pattern in k-space for calibration. Zero-crossing detection extracts the k-space distribution of a spectrometer from the interferogram in the wavelength domain, and a calibration lamp provides information about absolute wavenumbers. To assign wavenumbers, wavelength-to-k-space conversion is required for the characteristic spectrum of the calibration lamp with the extracted k-space distribution. Then, the wavelength calibration is completed by inverse conversion of the k-space into wavelength domain. The calibration performance of the proposed method was demonstrated with two experimental conditions of four and eight characteristic spectral peaks. The proposed method elicited reliable calibration results in both cases, whereas the conventional method of third-order polynomial curve fitting failed to determine wavelengths in the case of four characteristic peaks. Moreover, for optical coherence tomography imaging, the proposed method could improve axial resolution due to higher suppression of sidelobes in point spread function than the conventional method. We believe that our findings can improve not only wavelength calibration accuracy but also resolution for optical coherence tomography.

Shedding light on moths: shorter wavelengths attract noctuids more than geometrids

PubMed Central

Somers-Yeates, Robin; Hodgson, David; McGregor, Peter K.; Spalding, Adrian; ffrench-Constant, Richard H.

2013-01-01

With moth declines reported across Europe, and parallel changes in the amount and spectra of street lighting, it is important to understand exactly how artificial lights affect moth populations. We therefore compared the relative attractiveness of shorter wavelength (SW) and longer wavelength (LW) lighting to macromoths. SW light attracted significantly more individuals and species of moth, either when used alone or in competition with LW lighting. We also found striking differences in the relative attractiveness of different wavelengths to different moth groups. SW lighting attracted significantly more Noctuidae than LW, whereas both wavelengths were equally attractive to Geometridae. Understanding the extent to which different groups of moth are attracted to different wavelengths of light will be useful in determining the impact of artificial light on moth populations. PMID:23720524

Real-time and sub-wavelength ultrafast coherent diffraction imaging in the extreme ultraviolet.

PubMed

Zürch, M; Rothhardt, J; Hädrich, S; Demmler, S; Krebs, M; Limpert, J; Tünnermann, A; Guggenmos, A; Kleineberg, U; Spielmann, C

2014-12-08

Coherent Diffraction Imaging is a technique to study matter with nanometer-scale spatial resolution based on coherent illumination of the sample with hard X-ray, soft X-ray or extreme ultraviolet light delivered from synchrotrons or more recently X-ray Free-Electron Lasers. This robust technique simultaneously allows quantitative amplitude and phase contrast imaging. Laser-driven high harmonic generation XUV-sources allow table-top realizations. However, the low conversion efficiency of lab-based sources imposes either a large scale laser system or long exposure times, preventing many applications. Here we present a lensless imaging experiment combining a high numerical aperture (NA = 0.8) setup with a high average power fibre laser driven high harmonic source. The high flux and narrow-band harmonic line at 33.2 nm enables either sub-wavelength spatial resolution close to the Abbe limit (Δr = 0.8λ) for long exposure time, or sub-70 nm imaging in less than one second. The unprecedented high spatial resolution, compactness of the setup together with the real-time capability paves the way for a plethora of applications in fundamental and life sciences.

Influence of skin type and wavelength on light wave reflectance.

PubMed

Fallow, Bennett A; Tarumi, Takashi; Tanaka, Hirofumi

2013-06-01

A new application of photoplethysmography (PPG) has emerged recently to provide the possibility of heart rate monitoring without a telemetric chest strap. The aim of this study was to determine if a new device could detect pulsation over a broad range of skin types, and what light wavelength would be most suitable for detecting the signals. A light emitting diode-based PPG system was used to detect changes in pulsatile blood flow on 23 apparently healthy individuals (11 male and 12 female, 20-59 years old) of varying skin types classified according to a questionnaire in combination with digital photographs with a skin type chart. Four different light wavelengths (470, 520, 630, and 880 nm) were tested. Normalized modulation level is calculated as the AC/DC component ratio and represents the change in flow over the underlying constant state of flow or perfusion. In the resting condition, green light wavelength (520 nm) displayed greater modulation (p < 0.001) than all the other wavelengths analyzed regardless of skin types. Type V (dark brown) skin type was significantly lower in modulation than all other skin types. In the exercise condition, both blue (470 nm) and green (520 nm) light wavelengths displayed greater signal-to-noise ratios than red (630 nm) or infrared (880 nm) light wavelengths (p < 0.001). We concluded that a PPG-based device can detect pulsation across all skin types and that a greater resolution was obtained using a green light wavelength at rest and a green or blue light wavelength during exercise.

Flexible and scalable wavelength multicast of coherent optical OFDM with tolerance against pump phase-noise using reconfigurable coherent multi-carrier pumping.

PubMed

Lu, Guo-Wei; Bo, Tianwai; Sakamoto, Takahide; Yamamoto, Naokatsu; Chan, Calvin Chun-Kit

2016-10-03

Recently the ever-growing demand for dynamic and high-capacity services in optical networks has resulted in new challenges that require improved network agility and flexibility in order for network resources to become more "consumable" and dynamic, or elastic, in response to requests from higher network layers. Flexible and scalable wavelength conversion or multicast is one of the most important technologies needed for developing agility in the physical layer. This paper will investigate how, using a reconfigurable coherent multi-carrier as a pump, the multicast scalability and the flexibility in wavelength allocation of the converted signals can be effectively improved. Moreover, the coherence in the multiple carriers prevents the phase noise transformation from the local pump to the converted signals, which is imperative for the phase-noise-sensitive multi-level single- or multi-carrier modulated signal. To verify the feasibility of the proposed scheme, we experimentally demonstrate the wavelength multicast of coherent optical orthogonal frequency division multiplexing (CO-OFDM) signals using a reconfigurable coherent multi-carrier pump, showing flexibility in wavelength allocation, scalability in multicast, and tolerance against pump phase noise. Less than 0.5 dB and 1.8 dB power penalties at a bit-error rate (BER) of 10^-3 are obtained for the converted CO-OFDM-quadrature phase-shift keying (QPSK) and CO-OFDM-16-ary quadrature amplitude modulation (16QAM) signals, respectively, even when using a distributed feedback laser (DFB) as a pump source. In contrast, with a free-running pumping scheme, the phase noise from DFB pumps severely deteriorates the CO-OFDM signals, resulting in a visible error-floor at a BER of 10^-2 in the converted CO-OFDM-16QAM signals.

Tunable Emission Wavelength Stacked InAs/GaAs Quantum Dots by Chemical Beam Epitaxy for Optical Coherence Tomography

PubMed Central

Ilahi, Bouraoui; Zribi, Jihene; Guillotte, Maxime; Arès, Richard; Aimez, Vincent; Morris, Denis

2016-01-01

We report on Chemical Beam Epitaxy (CBE) growth of wavelength tunable InAs/GaAs quantum dots (QD) based superluminescent diode’s active layer suitable for Optical Coherence Tomography (OCT). The In-flush technique has been employed to fabricate QD with controllable heights, from 5 nm down to 2 nm, allowing a tunable emission band over 160 nm. The emission wavelength blueshift has been ensured by reducing both dots’ height and composition. A structure containing four vertically stacked height-engineered QDs have been fabricated, showing a room temperature broad emission band centered at 1.1 µm. The buried QD layers remain insensitive to the In-flush process of the subsequent layers, testifying the reliability of the process for broadband light sources required for high axial resolution OCT imaging. PMID:28773633

Aqueous glucose measurement using differential absorption-based frequency domain optical coherence tomography at wavelengths of 1310 nm and 1625 nm

NASA Astrophysics Data System (ADS)

John, Pauline; Manoj, Murali; Sujatha, N.; Vasa, Nilesh J.; Rao, Suresh R.

2015-07-01

This work presents a combination of differential absorption technique and frequency domain optical coherence tomography for detection of glucose, which is an important analyte in medical diagnosis of diabetes. Differential absorption technique is used to detect glucose selectively in the presence of interfering species especially water and frequency domain optical coherence tomography (FDOCT) helps to obtain faster acquisition of depth information. Two broadband super-luminescent diode (SLED) sources with centre wavelengths 1586 nm (wavelength range of 1540 to 1640 nm) and 1312 nm (wavelength range of 1240 to 1380 nm) and a spectral width of ≍ 60 nm (FWHM) are used. Preliminary studies on absorption spectroscopy using various concentrations of aqueous glucose solution gave promising results to distinguish the absorption characteristics of glucose at two wavelengths 1310 nm (outside the absorption band of glucose) and 1625 nm (within the absorption band of glucose). In order to mimic the optical properties of biological skin tissue, 2% and 10% of 20% intralipid with various concentrations of glucose (0 to 4000 mg/dL) was prepared and used as sample. Using OCT technique, interference spectra were obtained using an optical spectrum analyzer with a resolution of 0.5 nm. Further processing of the interference spectra provided information on reflections from the surfaces of the cuvette containing the aqueous glucose sample. Due to the absorption of glucose in the wavelength range of 1540 nm to 1640 nm, a trend of reduction in the intensity of the back reflected light was observed with increase in the concentration of glucose.

Multiple coherent light scattering in ultracold rubidium

NASA Astrophysics Data System (ADS)

Kulatunga, P.; Sukenik, C. I.; Havey, M. D.; Kupriyanov, D. V.; Sokolov, I. M.

2001-11-01

We report investigation of multiple coherent light scattering from ^85Rb atoms confined in a magneto-optic trap. In a theoretical study of intensity enhancement of near-resonant backscattered light from cold ^85,87Rb atoms, we consider the dominant mode of double scattering only. Enhancement factors are calculated for all D1 and D2 hyperfine components and for both isotopes. In experimental studies, measurements are made of coherent backscattering of a low-intensity probe beam tuned near the F = 3 - F' = 4 transition in ^85Rb atoms. Polarization of backscattered light is determined by a backscattering polarimeter; the spatial distribution of light intensity is measured by a liquid-nitrogen cooled CCD camera set in the focal plane of the analyzing optics. The instrument has angular resolution of about 100 micro-radians, and a polarization analyzing power of roughly 1000. In this paper we describe the instrument details, including calibration procedures, and progress towards observation of atomic coherent backscattering.

Multiple coherent light scattering in ultracold rubidium

NASA Astrophysics Data System (ADS)

Havey, M. D.; Sukenik, C. I.; Kulatunga, P.; Kupriyanov, D. V.; Sokolov, I. M.

2001-05-01

We report investigation of multiple coherent light scattering from ^85Rb atoms confined in a magneto-optic trap. In a theoretical study of intensity enhancement of near-resonant backscattered light from cold ^85,87Rb atoms, we consider the dominant mode of double scattering only. Enhancement factors are calculated for all D1 and D2 hyperfine components and for both isotopes. In experimental studies, measurements are made of coherent backscattering of a low-intensity probe beam tuned near the F = 3 - F' = 4 transition in ^85Rb atoms. Polarization of backscattered light is determined by a backscattering polarimeter; the spatial distribution of light intensity is measured by a liquid-nitrogen cooled CCD camera set in the focal plane of the analyzing optics. The instrument has angular resolution of about 100 micro-radians, and a polarization analyzing power of roughly 1000. In this paper we describe the instrument details, including calibration procedures, and progress towards observation of atomic coherent backscattering.

Using a pseudo-thermal light source to teach spatial coherence

NASA Astrophysics Data System (ADS)

Pieper, K.; Bergmann, A.; Dengler, R.; Rockstuhl, C.

2018-07-01

Teaching students spatial coherence constitutes a challenge. On the one hand, discussing it theoretically requires a quite demanding mathematical breadth. On the other hand, discussing it experimentally is hardly possible as coherence usually cannot be directly observed. To solve this problem, we show, by studying the contrast of interference patterns of a double slit, that speckles of a pseudo-thermal light source, consisting of a laser and a rotating diffuser disc, are equivalent to the spatial extent of coherent areas of a thermal light source. Coherent areas are spatial regions within which light can be considered as coherent. The unique advantage of such pseudo-thermal light source is the opportunity to directly observe the spatial extent of the coherent areas. This renders the phenomena perceptible and accessible by various experiments, as described in this contribution. This opens modern paths to teach spatial coherence to students with a notably reduced order of abstraction.

Invariant polarimetric contrast parameters of coherent light.

PubMed

Réfrégier, Philippe; Goudail, François

2002-06-01

Many applications use an active coherent illumination and analyze the variation of the polarization state of optical signals. However, as a result of the use of coherent light, these signals are generally strongly perturbed with speckle noise. This is the case, for example, for active polarimetric imaging systems that are useful for enhancing contrast between different elements in a scene. We propose a rigorous definition of the minimal set of parameters that characterize the difference between two coherent and partially polarized states. Indeed, two states of partially polarized light are a priori defined by eight parameters, for example, their two Stokes vectors. We demonstrate that the processing performance for such signal processing tasks as detection, localization, or segmentation of spatial or temporal polarization variations is uniquely determined by two scalar functions of these eight parameters. These two scalar functions are the invariant parameters that define the polarimetric contrast between two polarized states of coherent light. Different polarization configurations with the same invariant contrast parameters will necessarily lead to the same performance for a given task, which is a desirable quality for a rigorous contrast measure. The definition of these polarimetric contrast parameters simplifies the analysis and the specification of processing techniques for coherent polarimetric signals.

Coherent optical processing using noncoherent light after source masking.

PubMed

Boopathi, V; Vasu, R M

1992-01-10

Coherent optical processing starting with spatially noncoherent illumination is described. Good spatial coherence is introduced in the far field by modulating a noncoherent source when masks with sharp autocorrelation are used. The far-field mutual coherence function of light is measured and it is seen that, for the masks and the source size used here, we get a fairly large area over which the mutual coherence function is high and flat. We demonstrate traditional coherent processing operations such as Fourier transformation and image deblurring when coherent light that is produced in the above fashion is used. A coherence-redundancy merit function is defined for this type of processing system. It is experimentally demonstrated that the processing system introduced here has superior blemish tolerance compared with a traditional processor that uses coherent illumination.

The Linac Coherent Light Source

DOE PAGES

White, William E.; Robert, Aymeric; Dunne, Mike

2015-05-01

The Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory was the first hard X-ray free-electron laser (FEL) to operate as a user facility. After five years of operation, LCLS is now a mature FEL user facility. Our personal views about opportunities and challenges inherent to these unique light sources are discussed.

Coherence solution for bidirectional reflectance distributions of surfaces with wavelength-scale statistics.

PubMed

Hoover, Brian G; Gamiz, Victor L

2006-02-01

The scalar bidirectional reflectance distribution function (BRDF) due to a perfectly conducting surface with roughness and autocorrelation width comparable with the illumination wavelength is derived from coherence theory on the assumption of a random reflective phase screen and an expansion valid for large effective roughness. A general quadratic expansion of the two-dimensional isotropic surface autocorrelation function near the origin yields representative Cauchy and Gaussian BRDF solutions and an intermediate general solution as the sum of an incoherent component and a nonspecular coherent component proportional to an integral of the plasma dispersion function in the complex plane. Plots illustrate agreement of the derived general solution with original bistatic BRDF data due to a machined aluminum surface, and comparisons are drawn with previously published data in the examination of variations with incident angle, roughness, illumination wavelength, and autocorrelation coefficients in the bistatic and monostatic geometries. The general quadratic autocorrelation expansion provides a BRDF solution that smoothly interpolates between the well-known results of the linear and parabolic approximations.

Coherent Multiple Light Scattering in Ultracold Atomic Rb

NASA Astrophysics Data System (ADS)

Kulatunga, Pasad; Sukenik, C. I.; Balik, Salim; Havey, M. D.; Kupriyanov, D. V.; Sokolov, I. M.

2003-05-01

Wave transport in mesoscopic systems can be strongly influenced by coherent multiple scattering,which can lead to novel magneto-optic, transmission, and backscattering effects of light in atomic vapors. Although related to traditional studies of radiation trapping, in ultracold vapors negligible frequency or phase redistribution takes place in the scattering, and high-order coherent light scattering occurs. Among other things, this leads to enhancement of the influence of otherwise small non-resonant terms in the scattering amplitudes. We report investigation of multiple coherent light scattering from ultracold Rb atoms confined in a magneto-optic trap (MOT). In experimental studies, measurements are made of the angular, spectral, and polarization-dependent coherent backscattering profile of a low-intensity probe beam tuned near the F = 3 - F' = 4 hyperfine transition. The influence of higher probe beam intensity is also studied. In a theoretical study of angular intensity enhancement of backscattered light, we consider scattering orders up to 10 and a realistic and asymmetric Gaussian atom distribution in the MOT. Supported by NSF, NATO, and RFBR.

Light-Irradiation Wavelength and Intensity Changes Influence Aflatoxin Synthesis in Fungi

PubMed Central

Suzuki, Tadahiro

2018-01-01

Fungi respond to light irradiation by forming conidia and occasionally synthesizing mycotoxins. Several light wavelengths, such as blue and red, affect the latter. However, the relationship between light irradiation and mycotoxin synthesis varies depending on the fungal species or strain. This study focused on aflatoxin (AF), which is a mycotoxin, and the types of light irradiation that increase AF synthesis. Light-irradiation tests using the visible region indicated that blue wavelengths in the lower 500 nm region promoted AF synthesis. In contrast, red wavelengths of 660 nm resulted in limited significant changes compared with dark conditions. Irradiation tests with different intensity levels indicated that a low light intensity increased AF synthesis. For one fungal strain, light irradiation decreased the AF synthesis under all wavelength conditions. However, the decrease was mitigated by 525 nm low intensity irradiation. Thus, blue-green low intensity irradiation may increase AF synthesis in fungi. PMID:29304012

Multi-wavelength aerosol light absorption measurements in the Amazon rainforest

NASA Astrophysics Data System (ADS)

Saturno, Jorge; Chi, Xuguang; Pöhlker, Christopher; Morán, Daniel; Ditas, Florian; Massabò, Dario; Prati, Paolo; Rizzo, Luciana; Artaxo, Paulo; Andreae, Meinrat

2015-04-01

The most important light-absorbing aerosol is black carbon (BC), which is emitted by incomplete combustion of fossil fuels and biomass. BC is considered the second anthropogenic contributor to global warming. Beyond BC, other aerosols like some organics, dust, and primary biological aerosol particles are able to absorb radiation. In contrast to BC, the light absorption coefficient of these aerosols is wavelength dependent. Therefore, multi-wavelength measurements become important in environments where BC is not the predominant light-absorbing aerosol like in the Amazon. The Amazon Tall Tower Observatory (ATTO) site is located in the remote Amazon rainforest, one of the most pristine continental sites in the world during the wet season. In the dry season, winds coming from the southern hemisphere are loaded with biomass burning aerosol particles originated by farming-related deforestation. BC and aerosol number concentration data from the last two years indicate this is the most polluted period. Two different techniques have been implemented to measure the light absorption at different wavelengths; one of them is the 7-wavelengths Aethalometer, model AE30, an instrument that measures the light attenuation on a filter substrate and requires multiple scattering and filter-loading corrections to retrieve the light absorption coefficient. The other method is an offline technique, the Multi-Wavelength Absorbance Analysis (MWAA), which is able to measure reflectance and absorbance by aerosols collected on a filter and, by means of a radiative model, can retrieve the light absorption coefficient. Filters collected during May-September 2014, comprehending wet-to-dry transition and most of the dry season, were analyzed. The results indicate that the Absorption Ångström Exponent (AAE), a parameter that is directly proportional to the wavelength dependence of the aerosol light absorption, is close to 1.0 during the transition period and slightly decreases in the beginning of

Coherent dynamics of a telecom-wavelength entangled photon source.

PubMed

Ward, M B; Dean, M C; Stevenson, R M; Bennett, A J; Ellis, D J P; Cooper, K; Farrer, I; Nicoll, C A; Ritchie, D A; Shields, A J

2014-01-01

Quantum networks can interconnect remote quantum information processors, allowing interaction between different architectures and increasing net computational power. Fibre-optic telecommunications technology offers a practical platform for routing weakly interacting photonic qubits, allowing quantum correlations and entanglement to be established between distant nodes. Although entangled photons have been produced at telecommunications wavelengths using spontaneous parametric downconversion in nonlinear media, as system complexity increases their inherent excess photon generation will become limiting. Here we demonstrate entangled photon pair generation from a semiconductor quantum dot at a telecommunications wavelength. Emitted photons are intrinsically anti-bunched and violate Bell's inequality by 17 standard deviations High-visibility oscillations of the biphoton polarization reveal the time evolution of the emitted state with exceptional clarity, exposing long coherence times. Furthermore, we introduce a method to evaluate the fidelity to a time-evolving Bell state, revealing entanglement between photons emitted up to 5 ns apart, exceeding the exciton lifetime.

Self-imaging of partially coherent light in graded-index media.

PubMed

Ponomarenko, Sergey A

2015-02-15

We demonstrate that partially coherent light beams of arbitrary intensity and spectral degree of coherence profiles can self-image in linear graded-index media. The results can be applicable to imaging with noisy spatial or temporal light sources.

Coherent light squeezing states within a modified microring system

NASA Astrophysics Data System (ADS)

Ali, J.; Pornsuwancharoen, N.; Youplao, P.; Aziz, M. S.; Amiri, I. S.; Chaiwong, K.; Chiangga, S.; Singh, G.; Yupapin, P.

2018-06-01

We have proposed the simple method of the squeezed light generation in the modified microring resonator, which is known as the microring conjugate mirror (MCM). When the monochromatic light is input into the MCM, the general form of the squeezed coherent states for a quantum harmonic oscillator can be generated by controlling the additional two side rings, which are the phase modulators. By using the graphical method called the Optiwave program, the coherent squeezed states of coherent light within an MCM can be obtained and interpreted as the amplitude, phase, quadrature and photon number-squeezed states. This method has shown potentials for microring related device design, which can be used before practical applications.

Coherent imaging with incoherent light in digital holographic microscopy

NASA Astrophysics Data System (ADS)

Chmelik, Radim

2012-01-01

Digital holographic microscope (DHM) allows for imaging with a quantitative phase contrast. In this way it becomes an important instrument, a completely non-invasive tool for a contrast intravital observation of living cells and a cell drymass density distribution measurement. A serious drawback of current DHMs is highly coherent illumination which makes the lateral resolution worse and impairs the image quality by a coherence noise and a parasitic interference. An uncompromising solution to this problem can be found in the Leith concept of incoherent holography. An off-axis hologram can be formed with arbitrary degree of light coherence in systems equipped with an achromatic interferometer and thus the resolution and the image quality typical for an incoherent-light wide-field microscopy can be achieved. In addition, advanced imaging modes based on limited coherence can be utilized. The typical example is a coherence-gating effect which provides a finite axial resolution and makes DHM image similar to that of a confocal microscope. These possibilities were described theoretically using the formalism of three-dimensional coherent transfer functions and proved experimentally by the coherence-controlled holographic microscope which is DHM based on the Leith achromatic interferometer. Quantitative-phase-contrast imaging is demonstrated with incoherent light by the living cancer cells observation and their motility evaluation. The coherence-gating effect was proved by imaging of model samples through a scattering layer and living cells inside an opalescent medium.

Highly coherent red-shifted dispersive wave generation around 1.3 μm for efficient wavelength conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xia; Bi, Wanjun; University of Chinese Academy of Sciences, Beijing 100039

2015-03-14

This research investigates the mechanism of the optical dispersive wave (DW) and proposes a scheme that can realize an efficient wavelength conversion. In an elaborately designed photonic crystal fiber, a readily available ytterbium laser operating at ∼1 μm can be transferred to the valuable 1.3 μm wavelength range. A low-order soliton is produced to concentrate the energy of the DW into the target wavelength range and improve the degree of coherence. The input chirp is demonstrated to be a factor that enhances the wavelength conversion efficiency. With a positive initial chirp, 76.6% of the pump energy in the fiber can be transferredmore » into a spectral range between 1.24 and 1.4 μm. With the use of a grating compressor, it is possible to compress the generated coherent DW of several picoseconds into less than 90 fs.« less

Coherent light scattering of heterogeneous randomly rough films and effective medium in the theory of electromagnetic wave multiple scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berginc, G

2013-11-30

We have developed a general formalism based on Green's functions to calculate the coherent electromagnetic field scattered by a random medium with rough boundaries. The approximate expression derived makes it possible to determine the effective permittivity, which is generalised for a layer of an inhomogeneous random medium with different types of particles and bounded with randomly rough interfaces. This effective permittivity describes the coherent propagation of an electromagnetic wave in a random medium with randomly rough boundaries. We have obtained an expression, which contains the Maxwell – Garnett formula at the low-frequency limit, and the Keller formula; the latter hasmore » been proved to be in good agreement with experiments for particles whose dimensions are larger than a wavelength. (coherent light scattering)« less

Goos-Hänchen shift of partially coherent light fields in epsilon-near-zero metamaterials

NASA Astrophysics Data System (ADS)

Ziauddin; Chuang, You-Lin; Qamar, Sajid; Lee, Ray-Kuang

2016-05-01

The Goos-Hänchen (GH) shifts in the reflected light are investigated both for p and s polarized partial coherent light beams incident on epsilon-near-zero (ENZ) metamaterials. In contrary to the coherent counterparts, the magnitude of GH shift becomes non-zero for p polarized partial coherent light beam; while GH shift can be relatively large with a small degree of spatial coherence for s polarized partial coherent beam. Dependence on the beam width and the permittivity of ENZ metamaterials is also revealed for partial coherent light fields. Our results on the GH shifts provide a direction on the applications for partial coherent light sources in ENZ metamaterials.

Visible light spectral domain optical coherence microscopy system for ex vivo imaging

NASA Astrophysics Data System (ADS)

Lichtenegger, Antonia; Harper, Danielle J.; Augustin, Marco; Eugui, Pablo; Fialová, Stanislava; Woehrer, Adelheid; Hitzenberger, Christoph K.; Baumann, Bernhard

2017-02-01

A visible light spectral domain optical coherence microscopy system operating in the wavelength range of 450-680 nm was developed. The resulting large wavelength range of 230 nm enabled an ultrahigh axial resolution of 0.88μm in tissue. The setup consisted of a Michelson interferometer combined with a homemade spectrometer with a spectral resolution of 0.03 nm. Scanning of 1 x 1 mm2 and 0.5 x 0.5 mm2 areas was performed by an integrated microelectromechanical mirror. After scanning the light beam is focused onto the tissue by a commercial objective with a 10 x magnification, resulting in a transverse resolution of 2 μm . Specification measurements showed that a -89 dB sensitivity with a 24 dB/mm roll-off could be achieved with the system. First of all the capabilities of the system were tested by investigating millimeter paper, tape and the USAF (US Air Force) 1951 resolution test target. Finally cerebral tissues from non-pathological and Alzheimer's disease affected brains were investigated. The results showed that structures, such as white and gray matter, could be distinguished. Furthermore a first effort was made to differentiate Alzheimer's disease from healthy brain tissue.

Coherent scattering of near-resonant light by a dense, microscopic cloud of cold two-level atoms: Experiment versus theory

NASA Astrophysics Data System (ADS)

Jennewein, Stephan; Brossard, Ludovic; Sortais, Yvan R. P.; Browaeys, Antoine; Cheinet, Patrick; Robert, Jacques; Pillet, Pierre

2018-05-01

We measure the coherent scattering of low-intensity, near-resonant light by a cloud of laser-cooled two-level rubidium atoms with a size comparable to the wavelength of light. We isolate a two-level atomic structure by applying a 300-G magnetic field. We measure both the temporal and the steady-state coherent optical response of the cloud for various detunings of the laser and for atom numbers ranging from 5 to 100. We compare our results to a microscopic coupled-dipole model and to a multimode, paraxial Maxwell-Bloch model. In the low-intensity regime, both models are in excellent agreement, thus validating the Maxwell-Bloch model. Comparing to the data, the models are found in very good agreement for relatively low densities (n /k3≲0.1 ), while significant deviations start to occur at higher density. This disagreement indicates that light scattering in dense, cold atomic ensembles is still not quantitatively understood, even in pristine experimental conditions.

Spectroscopic Doppler analysis for visible-light optical coherence tomography

NASA Astrophysics Data System (ADS)

Shu, Xiao; Liu, Wenzhong; Duan, Lian; Zhang, Hao F.

2017-12-01

Retinal oxygen metabolic rate can be effectively measured by visible-light optical coherence tomography (vis-OCT), which simultaneously quantifies oxygen saturation and blood flow rate in retinal vessels through spectroscopic analysis and Doppler measurement, respectively. Doppler OCT relates phase variation between sequential A-lines to the axial flow velocity of the scattering medium. The detectable phase shift is between -π and π due to its periodicity, which limits the maximum measurable unambiguous velocity without phase unwrapping. Using shorter wavelengths, vis-OCT is more vulnerable to phase ambiguity since flow induced phase variation is linearly related to the center wavenumber of the probing light. We eliminated the need for phase unwrapping using spectroscopic Doppler analysis. We split the whole vis-OCT spectrum into a series of narrow subbands and reconstructed vis-OCT images to extract corresponding Doppler phase shifts in all the subbands. Then, we quantified flow velocity by analyzing subband-dependent phase shift using linear regression. In the phantom experiment, we showed that spectroscopic Doppler analysis extended the measurable absolute phase shift range without conducting phase unwrapping. We also tested this method to quantify retinal blood flow in rodents in vivo.

Multi-wavelength mid-IR light source for gas sensing

NASA Astrophysics Data System (ADS)

Karioja, Pentti; Alajoki, Teemu; Cherchi, Matteo; Ollila, Jyrki; Harjanne, Mikko; Heinilehto, Noora; Suomalainen, Soile; Viheriälä, Jukka; Zia, Nouman; Guina, Mircea; Buczyński, Ryszard; Kasztelanic, Rafał; Kujawa, Ireneusz; Salo, Tomi; Virtanen, Sami; Kluczyński, Paweł; Sagberg, Hâkon; Ratajczyk, Marcin; Kalinowski, Przemyslaw

2017-02-01

Cost effective multi-wavelength light sources are key enablers for wide-scale penetration of gas sensors at Mid-IR wavelength range. Utilizing novel Mid-IR Si-based photonic integrated circuits (PICs) filter and wide-band Mid-IR Super Luminescent Light Emitting Diodes (SLEDs), we show the concept of a light source that covers 2.5…3.5 μm wavelength range with a resolution of <1nm. The spectral bands are switchable and tunable and they can be modulated. The source allows for the fabrication of an affordable multi-band gas sensor with good selectivity and sensitivity. The unit price can be lowered in high volumes by utilizing tailored molded IR lens technology and automated packaging and assembling technologies. The status of the development of the key components of the light source are reported. The PIC is based on the use of micron-scale SOI technology, SLED is based on AlGaInAsSb materials and the lenses are tailored heavy metal oxide glasses fabricated by the use of hot-embossing. The packaging concept utilizing automated assembly tools is depicted. In safety and security applications, the Mid-IR wavelength range covered by the novel light source allows for detecting several harmful gas components with a single sensor. At the moment, affordable sources are not available. The market impact is expected to be disruptive, since the devices currently in the market are either complicated, expensive and heavy instruments, or the applied measurement principles are inadequate in terms of stability and selectivity.

Lack of short-wavelength light during the school day delays dim light melatonin onset (DLMO) in middle school students.

PubMed

Figueiro, Mariana G; Rea, Mark S

2010-01-01

Circadian timing affects sleep onset. Delayed sleep onset can reduce sleep duration in adolescents required to awake early for a fixed school schedule. The absence of short-wavelength ("blue") morning light, which helps entrain the circadian system, can hypothetically delay sleep onset and decrease sleep duration in adolescents. The goal of this study was to investigate whether removal of short-wavelength light during the morning hours delayed the onset of melatonin in young adults. Dim light melatonin onset (DLMO) was measured in eleven 8th-grade students before and after wearing orange glasses, which removed short-wavelength light, for a five-day school week. DLMO was significantly delayed (30 minutes) after the five-day intervention, demonstrating that short-wavelength light exposure during the day can be important for advancing circadian rhythms in students. Lack of short-wavelength light in the morning has been shown to delay the circadian clock in controlled laboratory conditions. The results presented here are the first to show, outside laboratory conditions, that removal of short-wavelength light in the morning hours can delay DLMO in 8th-grade students. These field data, consistent with results from controlled laboratory studies, are directly relevant to lighting practice in schools.

Cell response to quasi-monochromatic light with different coherence

NASA Astrophysics Data System (ADS)

Budagovsky, A. V.; Solovykh, N. V.; Budagovskaya, O. N.; Budagovsky, I. A.

2015-04-01

The problem of the light coherence effect on the magnitude of the photoinduced cell response is discussed. The origins of ambiguous interpretation of the known experimental results are considered. Using the biological models, essentially differing in anatomy, morphology and biological functions (acrospires of radish, blackberry microsprouts cultivated in vitro, plum pollen), the effect of statistical properties of quasi-monochromatic light (λmax = 633 nm) on the magnitude of the photoinduced cell response is shown. It is found that for relatively low spatial coherence, the cell functional activity changes insignificantly. The maximal enhancement of growing processes (stimulating effect) is observed when the coherence length Lcoh and the correlation radius rcor are greater than the cell size, i.e., the entire cell fits into the field coherence volume. In this case, the representative indicators (germination of seeds and pollen, the spears length) exceeds those of non-irradiated objects by 1.7 - 3.9 times. For more correct assessment of the effect of light statistical properties on photocontrol processes, it is proposed to replace the qualitative description (coherent - incoherent) with the quantitative one, using the determination of spatial and temporal correlation functions and comparing them with the characteristic dimensions of the biological structures, e.g., the cell size.

Wavelength-tunable light shaping with cholesteric liquid crystal microlenses.

PubMed

Bayon, Chloé; Agez, Gonzague; Mitov, Michel

2014-06-21

The ability to guide light on the mesoscopic scale is important both scientifically and technologically. Especially relevant is the development of wavelength-tunable light-shaping microdevices. Here we demonstrate the use of cholesteric liquid crystal polygonal textures organized as an array of microlenses for this purpose. The beam shaping is controlled by tuning the wavelength of the incident light in the visible spectrum. By taking advantage of the self-organization property of liquid crystals, the structure of the lens and its optical response are tailored by changing the annealing time of the single layer material during a completely integrated one-step process. The intrinsic helical organization of the layer is the cause of the light shaping and not the shape of the surface as for conventional lenses. A new concept of light manipulation using the structure chirality of liquid crystals is demonstrated, which concerns soft matter photonic circuits to mould the light.

Nocturnal light exposure impairs affective responses in a wavelength-dependent manner.

PubMed

Bedrosian, Tracy A; Vaughn, Celynn A; Galan, Anabel; Daye, Ghassan; Weil, Zachary M; Nelson, Randy J

2013-08-07

Life on earth is entrained to a 24 h solar cycle that synchronizes circadian rhythms in physiology and behavior; light is the most potent entraining cue. In mammals, light is detected by (1) rods and cones, which mediate visual function, and (2) intrinsically photosensitive retinal ganglion cells (ipRGCs), which primarily project to the suprachiasmatic nucleus (SCN) in the hypothalamus to regulate circadian rhythms. Recent evidence, however, demonstrates that ipRGCs also project to limbic brain regions, suggesting that, through this pathway, light may have a role in cognition and mood. Therefore, it follows that unnatural exposure to light may have negative consequences for mood or behavior. Modern environmental lighting conditions have led to excessive exposure to light at night (LAN), and particularly to blue wavelength lights. We hypothesized that nocturnal light exposure (i.e., dim LAN) would induce depressive responses and alter neuronal structure in hamsters (Phodopus sungorus). If this effect is mediated by ipRGCs, which have reduced sensitivity to red wavelength light, then we predicted that red LAN would have limited effects on brain and behavior compared with shorter wavelengths. Additionally, red LAN would not induce c-Fos activation in the SCN. Our results demonstrate that exposure to LAN influences behavior and neuronal plasticity and that this effect is likely mediated by ipRGCs. Modern sources of LAN that contain blue wavelengths may be particularly disruptive to the circadian system, potentially contributing to altered mood regulation.

Near optimal discrimination of binary coherent signals via atom–light interaction

NASA Astrophysics Data System (ADS)

Han, Rui; Bergou, János A.; Leuchs, Gerd

2018-04-01

We study the discrimination of weak coherent states of light with significant overlaps by nondestructive measurements on the light states through measuring atomic states that are entangled to the coherent states via dipole coupling. In this way, the problem of measuring and discriminating coherent light states is shifted to finding the appropriate atom–light interaction and atomic measurements. We show that this scheme allows us to attain a probability of error extremely close to the Helstrom bound, the ultimate quantum limit for discriminating binary quantum states, through the simple Jaynes–Cummings interaction between the field and ancilla with optimized light–atom coupling and projective measurements on the atomic states. Moreover, since the measurement is nondestructive on the light state, information that is not detected by one measurement can be extracted from the post-measurement light states through subsequent measurements.

A linearly frequency-swept high-speed-rate multi-wavelength laser for optical coherence tomography

NASA Astrophysics Data System (ADS)

Wang, Qiyu; Wang, Zhaoying; Yuan, Quan; Ma, Rui; Du, Tao; Yang, Tianxin

2017-02-01

We proposed and demonstrated a linearly frequency-swept multi-wavelength laser source for optical coherence tomography (OCT) eliminating the need of wavenumber space resampling in the postprocessing progress. The source consists of a multi-wavelength fiber laser source (MFS) and an optical sweeping loop. In this novel laser source, an equally spaced multi-wavelength laser is swept simultaneously by a certain step each time in the frequency domain in the optical sweeping loop. The sweeping step is determined by radio frequency (RF) signal which can be precisely controlled. Thus the sweeping behavior strictly maintains a linear relationship between time and frequency. We experimentally achieved linear time-frequency sweeping at a sweeping rate of 400 kHz with our laser source.

Coherent Soft X-ray Diffraction Imaging of Coliphage PR772 at the Linac Coherent Light Source

DOE Data Explorer

Reddy, Hemanth, K.N.

2017-01-05

A dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source.

Cell response to quasi-monochromatic light with different coherence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budagovsky, A V; Solovykh, N V; Budagovskaya, O N

The problem of the light coherence effect on the magnitude of the photoinduced cell response is discussed. The origins of ambiguous interpretation of the known experimental results are considered. Using the biological models, essentially differing in anatomy, morphology and biological functions (acrospires of radish, blackberry microsprouts cultivated in vitro, plum pollen), the effect of statistical properties of quasi-monochromatic light (λ{sub max} = 633 nm) on the magnitude of the photoinduced cell response is shown. It is found that for relatively low spatial coherence, the cell functional activity changes insignificantly. The maximal enhancement of growing processes (stimulating effect) is observed whenmore » the coherence length L{sub coh} and the correlation radius r{sub cor} are greater than the cell size, i.e., the entire cell fits into the field coherence volume. In this case, the representative indicators (germination of seeds and pollen, the spears length) exceeds those of non-irradiated objects by 1.7 – 3.9 times. For more correct assessment of the effect of light statistical properties on photocontrol processes, it is proposed to replace the qualitative description (coherent – incoherent) with the quantitative one, using the determination of spatial and temporal correlation functions and comparing them with the characteristic dimensions of the biological structures, e.g., the cell size. (biophotonics)« less

Simulation of partially coherent light propagation using parallel computing devices

NASA Astrophysics Data System (ADS)

Magalhães, Tiago C.; Rebordão, José M.

2017-08-01

Light acquires or loses coherence and coherence is one of the few optical observables. Spectra can be derived from coherence functions and understanding any interferometric experiment is also relying upon coherence functions. Beyond the two limiting cases (full coherence or incoherence) the coherence of light is always partial and it changes with propagation. We have implemented a code to compute the propagation of partially coherent light from the source plane to the observation plane using parallel computing devices (PCDs). In this paper, we restrict the propagation in free space only. To this end, we used the Open Computing Language (OpenCL) and the open-source toolkit PyOpenCL, which gives access to OpenCL parallel computation through Python. To test our code, we chose two coherence source models: an incoherent source and a Gaussian Schell-model source. In the former case, we divided into two different source shapes: circular and rectangular. The results were compared to the theoretical values. Our implemented code allows one to choose between the PyOpenCL implementation and a standard one, i.e using the CPU only. To test the computation time for each implementation (PyOpenCL and standard), we used several computer systems with different CPUs and GPUs. We used powers of two for the dimensions of the cross-spectral density matrix (e.g. 324, 644) and a significant speed increase is observed in the PyOpenCL implementation when compared to the standard one. This can be an important tool for studying new source models.

Modulating the amplitude and phase of the complex spectral degree of coherence with plasmonic interferometry

NASA Astrophysics Data System (ADS)

Li, Dongfang; Pacifici, Domenico

The spectral degree of coherence describes the correlation of electromagnetic fields, which plays a key role in many applications, including free-space optical communications and speckle-free bioimaging. Recently, plasmonic interferometry, i.e. optical interferometry that employs surface plasmon polaritons (SPPs), has enabled enhanced light transmission and high-sensitivity biosensing, among other applications. It offers new ways to characterize and engineer electromagnetic fields using nano-structured thin metal films. Here, we employ plasmonic interferometry to demonstrate full control of spatial coherence at length scales comparable to the wavelength of the incident light. Specifically, by measuring the diffraction pattern of several double-slit plasmonic structures etched on a metal film, the amplitude and phase of the degree of spatial coherence is determined as a function of slit-slit separation distance and incident wavelength. When the SPP contribution is turned on (i.e., by changing the polarization of the incident light from TE to TM illumination mode), strong modulation of both amplitude and phase of the spatial coherence is observed. These findings may help design compact modulators of optical spatial coherence and other optical elements to shape the light intensity in the far-field.

Design, development and use of the spectrometer for investigating coherent THz radiation produced by micro-bunching instabilities at Diamond Light Source

NASA Astrophysics Data System (ADS)

Finn, Aiveen; Karataev, Pavel; Rehm, Guenther

2016-07-01

Schottky barrier diodes (SBDs) are known for their low noise, ultra-fast response and excellent sensitivity. They are often implemented as detectors in the millimetre wavelength regime. Micro-bunch instabilities (MBI) have been detected at many light sources around the world including the Diamond Light Source, UK. These MBI can result in bursts of coherent synchrotron radiation (CSR) with millimetre wavelengths. More research needs to be carried out with regards to the dynamics of MBI in order to confirm the simulations and to eventually harness the power of the CSR bursts. A single shot spectrometer has been designed and is under operation at the Diamond Light Source (DLS). It is composed of eight SBDs ranging from 33-1000 GHz. Unlike previous measurements carried out, each of the SBDs has been individually characterised thus making the results obtained comparable to simulations. In this paper, we present the assessment of each SBD in the spectrometer and the first results of the spectrometer's use in the beam.

Conditions for space invariance in optical data processors used with coherent or noncoherent light.

PubMed

Arsenault, H R

1972-10-01

The conditions for space invariance in coherent and noncoherent optical processors are considered. All linear optical processors are shown to belong to one of two types. The conditions for space invariance are more stringent for noncoherent processors than for coherent processors, so that a system that is linear in coherent light may be nonlinear in noncoherent light. However, any processor that is linear in noncoherent light is also linear in the coherent limit.

Observation of coherent backscattering of light in ultracold ^85Rb

NASA Astrophysics Data System (ADS)

Kulatunga, P.; Sukenik, C. I.; Havey, M. D.; Kupriyanov, D. V.; Sokolov, I. M.

2002-05-01

We report investigation of multiple coherent light scattering from ^85Rb atoms confined in a magneto-optic trap. In experimental studies, measurements are made of coherent backscattering of a low-intensity probe beam tuned near the F = 3 - F' = 4 transition in ^85Rb atoms. Polarization of backscattered light is determined by a backscattering polarimeter; the spatial distribution of light intensity is measured by a liquid-nitrogen cooled CCD camera set in the focal plane of the analyzing optics. The instrument has angular resolution of about 100 micro-radians, and a polarization analyzing power of roughly 1000. In this paper we describe the instrument details, including calibration procedures, and our measurements of atomic coherent backscattering. In a theoretical study of intensity enhancement of near-resonant backscattered light from cold ^85,87Rb atoms, we consider scattering orders up to 8 and a Gaussian atom distribution in the MOT. Enhancement factors are calculated for all D1 and D2 hyperfine components and for both isotopes.

Wavelength-Selective Light-Responsive DASA-Functionalized Polymersome Nanoreactors.

PubMed

Rifaie-Graham, Omar; Ulrich, Sebastian; Galensowske, Nikolas F B; Balog, Sandor; Chami, Mohamed; Rentsch, Daniel; Hemmer, James R; Read de Alaniz, Javier; Boesel, Luciano F; Bruns, Nico

2018-06-27

Transient activation of biochemical reactions by visible light and subsequent return to the inactive state in the absence of light is an essential feature of the biochemical processes in photoreceptor cells. To mimic such light-responsiveness with artificial nanosystems, polymersome nanoreactors were developed that can be switched on by visible light and self-revert fast in the dark at room temperature to their inactive state. Donor-acceptor Stenhouse adducts (DASAs), with their ability to isomerize upon irradiation with visible light, were employed to change the permeability of polymersome membranes by switching polarity from a nonpolar triene-enol form to a cyclopentenone with increased polarity. To this end, amphiphilic block copolymers containing poly(pentafluorophenyl methacrylate) in their hydrophobic block were synthesized by reversible addition-fragmentation chain-transfer (RAFT) radical polymerization and functionalized either with a DASA that is based on Meldrum's acid or with a novel fast-switching pyrazolone-based DASA. These polymers were self-assembled into vesicles. Release of hydrophilic payload could be triggered by light and stopped as soon as the light was turned off. The encapsulation of enzymes yielded photoresponsive nanoreactors that catalyzed reactions only if they were irradiated with light. A mixture of polymersome nanoreactors, one that switches in green light, the other switching in red light, permitted specific control of the individual reactions of a reaction cascade in one pot by irradiation with varied wavelengths, thus enabling light-controlled wavelength-selective catalysis. The DASA-based nanoreactors demonstrate the potential of DASAs to switch permeability of membranes and could find application to switch reactions on and off, on demand, e.g., in microfluidics or in drug delivery.

Multiplexed single-mode wavelength-to-time mapping of multimode light

PubMed Central

Chandrasekharan, Harikumar K; Izdebski, Frauke; Gris-Sánchez, Itandehui; Krstajić, Nikola; Walker, Richard; Bridle, Helen L.; Dalgarno, Paul A.; MacPherson, William N.; Henderson, Robert K.; Birks, Tim A.; Thomson, Robert R.

2017-01-01

When an optical pulse propagates along an optical fibre, different wavelengths travel at different group velocities. As a result, wavelength information is converted into arrival-time information, a process known as wavelength-to-time mapping. This phenomenon is most cleanly observed using a single-mode fibre transmission line, where spatial mode dispersion is not present, but the use of such fibres restricts possible applications. Here we demonstrate that photonic lanterns based on tapered single-mode multicore fibres provide an efficient way to couple multimode light to an array of single-photon avalanche detectors, each of which has its own time-to-digital converter for time-correlated single-photon counting. Exploiting this capability, we demonstrate the multiplexed single-mode wavelength-to-time mapping of multimode light using a multicore fibre photonic lantern with 121 single-mode cores, coupled to 121 detectors on a 32 × 32 detector array. This work paves the way to efficient multimode wavelength-to-time mapping systems with the spectral performance of single-mode systems. PMID:28120822

Coherent direct sequence optical code multiple access encoding-decoding efficiency versus wavelength detuning.

PubMed

Pastor, D; Amaya, W; García-Olcina, R; Sales, S

2007-07-01

We present a simple theoretical model of and the experimental verification for vanishing of the autocorrelation peak due to wavelength detuning on the coding-decoding process of coherent direct sequence optical code multiple access systems based on a superstructured fiber Bragg grating. Moreover, the detuning vanishing effect has been explored to take advantage of this effect and to provide an additional degree of multiplexing and/or optical code tuning.

Plant lighting system with five wavelength-band light-emitting diodes providing photon flux density and mixing ratio control

PubMed Central

2012-01-01

Background Plant growth and development depend on the availability of light. Lighting systems therefore play crucial roles in plant studies. Recent advancements of light-emitting diode (LED) technologies provide abundant opportunities to study various plant light responses. The LED merits include solidity, longevity, small element volume, radiant flux controllability, and monochromaticity. To apply these merits in plant light response studies, a lighting system must provide precisely controlled light spectra that are useful for inducing various plant responses. Results We have developed a plant lighting system that irradiated a 0.18 m2 area with a highly uniform distribution of photon flux density (PFD). The average photosynthetic PFD (PPFD) in the irradiated area was 438 micro-mol m–2 s–1 (coefficient of variation 9.6%), which is appropriate for growing leafy vegetables. The irradiated light includes violet, blue, orange-red, red, and far-red wavelength bands created by LEDs of five types. The PFD and mixing ratio of the five wavelength-band lights are controllable using a computer and drive circuits. The phototropic response of oat coleoptiles was investigated to evaluate plant sensitivity to the light control quality of the lighting system. Oat coleoptiles irradiated for 23 h with a uniformly distributed spectral PFD (SPFD) of 1 micro-mol m–2 s–1 nm–1 at every peak wavelength (405, 460, 630, 660, and 735 nm) grew almost straight upwards. When they were irradiated with an SPFD gradient of blue light (460 nm peak wavelength), the coleoptiles showed a phototropic curvature in the direction of the greater SPFD of blue light. The greater SPFD gradient induced the greater curvature of coleoptiles. The relation between the phototropic curvature (deg) and the blue-light SPFD gradient (micro-mol m–2 s–1 nm–1 m–1) was 2 deg per 1 micro-mol m–2 s–1 nm–1 m–1. Conclusions The plant lighting system, with a computer with a graphical user interface

High-resolution three-dimensional partially coherent diffraction imaging.

PubMed

Clark, J N; Huang, X; Harder, R; Robinson, I K

2012-01-01

The wave properties of light, particularly its coherence, are responsible for interference effects, which can be exploited in powerful imaging applications. Coherent diffractive imaging relies heavily on coherence and has recently experienced rapid growth. Coherent diffractive imaging recovers an object from its diffraction pattern by computational phasing with the potential of wavelength-limited resolution. Diminished coherence results in reconstructions that suffer from artefacts or fail completely. Here we demonstrate ab initio phasing of partially coherent diffraction patterns in three dimensions, while simultaneously determining the coherence properties of the illuminating wavefield. Both the dramatic improvements in image interpretability and the three-dimensional evaluation of the coherence will have broad implications for quantitative imaging of nanostructures and wavefield characterization with X-rays and electrons.

Miniaturized optical wavelength sensors

NASA Astrophysics Data System (ADS)

Kung, Helen Ling-Ning

Recently semiconductor processing technology has been applied to the miniaturization of optical wavelength sensors. Compact sensors enable new applications such as integrated diode-laser wavelength monitors and frequency lockers, portable chemical and biological detection, and portable and adaptive hyperspectral imaging arrays. Small sensing systems have trade-offs between resolution, operating range, throughput, multiplexing and complexity. We have developed a new wavelength sensing architecture that balances these parameters for applications involving hyperspectral imaging spectrometer arrays. In this thesis we discuss and demonstrate two new wavelength-sensing architectures whose single-pixel designs can easily be extended into spectrometer arrays. The first class of devices is based on sampling a standing wave. These devices are based on measuring the wavelength-dependent period of optical standing waves formed by the interference of forward and reflected waves at a mirror. We fabricated two different devices based on this principle. The first device is a wavelength monitor, which measures the wavelength and power of a monochromatic source. The second device is a spectrometer that can also act as a selective spectral coherence sensor. The spectrometer contains a large displacement piston-motion MEMS mirror and a thin GaAs photodiode flip-chip bonded to a quartz substrate. The performance of this spectrometer is similar to that of a Michelson in resolution, operating range, throughput and multiplexing but with the added advantages of fewer components and one-dimensional architecture. The second class of devices is based on the Talbot self-imaging effect. The Talbot effect occurs when a periodic object is illuminated with a spatially coherent wave. Periodically spaced self-images are formed behind the object. The spacing of the self-images is proportional to wavelength of the incident light. We discuss and demonstrate how this effect can be used for spectroscopy

Remote-sensing vibrometry at 1550 nm wavelength

NASA Astrophysics Data System (ADS)

Dräbenstedt, A.; Sauer, J.; Rembe, C.

2012-06-01

Laser-Doppler vibrometry (LDV) is a proven technique for vibration analysis of mechanical structures. A wavelength of 633 nm is usually employed because of the availability of the relatively inexpensive Helium-Neon laser source which has a good coherence behavior. However, coherence break-down through the beat of multiple longitudinal modes and the limited detector carrier-to-noise-ratio (CNR) at a measurement laser power of 1 mW have prevented a wide use of LDV in remote sensing applications. Such applications in civil engineering are bridges, towers or wind turbines. The lower photon energy of IR light at 1550 nm wavelength increases the CNR by a factor 2.4. This helps especially in the condition where the carrier power decreases below the FM threshold. We have designed a heterodyne interferometer which allows the shot noise limited detection at 1550 nm wavelength close to the theoretical possible CNR. We present calculations of the fundamental noise contributions in interferometric light detection for a comparison of the achievable CNR between common HeNe vibrometers and IR vibrometers. The calculations are backed by measurements that show the devices working close to the theoretical limits. The achievable noise level of the demodulated velocity signal is shown in dependence from the standoff distance. Our novel heterodyne interferometer has been transferred to the Polytec product RSV-150. An application example of this new sensor will be demonstrated.

Comparison of light absorption levels with different skin phantoms and the Monte Carlo simulation using Fourier-domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Jo, Hang Chan; Kim, Jae Hun; Kim, Dae Yu

2018-02-01

Dermatologic patients have various skin characteristics such as skin tone and pigmentation color. However most studies on laser ablation and treatment only considered laser operating conditions like wavelength, output power and pulse duration. The laser ablation arises from photothermal effect by photon energy absorption. Chromophores like melanin exist as the absorber in the skin. In this study, we painted color to mimic chromophores on in-vivo and in-vitro skin models to demonstrate influence on the laser ablation by skin color. Water-based pens were used to paint color. Cross sectional images of the laser ablation were acquired by Fourier-domain optical coherence tomography (Fd-OCT). Light source to make ablation was a Q-switch diode-pumped Nd:YVO4 nanosecond laser (532nm central wavelength). Irradiated light energy dose of the laser could not make ablation craters in the control group. However experimental groups showed craters with same irradiation light energy dose. These results show painting on skin increased tissue damage by absorption in painted color without dyeing cells or tissues.

Laser warning receiver to identify the wavelength and angle of arrival of incident laser light

DOEpatents

Sinclair; Michael B.; Sweatt, William C.

2010-03-23

A laser warning receiver is disclosed which has up to hundreds of individual optical channels each optically oriented to receive laser light from a different angle of arrival. Each optical channel has an optical wedge to define the angle of arrival, and a lens to focus the laser light onto a multi-wavelength photodetector for that channel. Each multi-wavelength photodetector has a number of semiconductor layers which are located in a multi-dielectric stack that concentrates the laser light into one of the semiconductor layers according to wavelength. An electrical signal from the multi-wavelength photodetector can be processed to determine both the angle of arrival and the wavelength of the laser light.

Visible-light optical coherence tomography: a review

NASA Astrophysics Data System (ADS)

Shu, Xiao; Beckmann, Lisa; Zhang, Hao F.

2017-12-01

Visible-light optical coherence tomography (vis-OCT) is an emerging imaging modality, providing new capabilities in both anatomical and functional imaging of biological tissue. It relies on visible light illumination, whereas most commercial and investigational OCTs use near-infrared light. As a result, vis-OCT requires different considerations in engineering design and implementation but brings unique potential benefits to both fundamental research and clinical care of several diseases. Here, we intend to provide a summary of the development of vis-OCT and its demonstrated applications. We also provide perspectives on future technology improvement and applications.

Long-wavelength optical coherence tomography at 1.7 µm for enhanced imaging depth

PubMed Central

Sharma, Utkarsh; Chang, Ernest W.; Yun, Seok H.

2009-01-01

Multiple scattering in a sample presents a significant limitation to achieve meaningful structural information at deeper penetration depths in optical coherence tomography (OCT). Previous studies suggest that the spectral region around 1.7 µm may exhibit reduced scattering coefficients in biological tissues compared to the widely used wavelengths around 1.3 µm. To investigate this long-wavelength region, we developed a wavelength-swept laser at 1.7 µm wavelength and conducted OCT or optical frequency domain imaging (OFDI) for the first time in this spectral range. The constructed laser is capable of providing a wide tuning range from 1.59 to 1.75 µm over 160 nm. When the laser was operated with a reduced tuning range over 95 nm at a repetition rate of 10.9 kHz and an average output power of 12.3 mW, the OFDI imaging system exhibited a sensitivity of about 100 dB and axial and lateral resolution of 24 µm and 14 µm, respectively. We imaged several phantom and biological samples using 1.3 µm and 1.7 µm OFDI systems and found that the depth-dependent signal decay rate is substantially lower at 1.7 µm wavelength in most, if not all samples. Our results suggest that this imaging window may offer an advantage over shorter wavelengths by increasing the penetration depths as well as enhancing image contrast at deeper penetration depths where otherwise multiple scattered photons dominate over ballistic photons. PMID:19030057

Short-Wavelength Light Enhances Cortisol Awakening Response in Sleep-Restricted Adolescents

PubMed Central

Figueiro, Mariana G.; Rea, Mark S.

2012-01-01

Levels of cortisol, a hormone produced by the adrenal gland, follow a daily, 24-hour rhythm with concentrations reaching a minimum in the evening and a peak near rising time. In addition, cortisol levels exhibit a sharp peak in concentration within the first hour after waking; this is known as the cortisol awakening response (CAR). The present study is a secondary analysis of a larger study investigating the impact of short-wavelength (λ max ≈ 470 nm) light on CAR in adolescents who were sleep restricted. The study ran over the course of three overnight sessions, at least one week apart. The experimental sessions differed in terms of the light exposure scenarios experienced during the evening prior to sleeping in the laboratory and during the morning after waking from a 4.5-hour sleep opportunity. Eighteen adolescents aged 12–17 years were exposed to dim light or to 40 lux (0.401 W/m2) of 470-nm peaking light for 80 minutes after awakening. Saliva samples were collected every 20 minutes to assess CAR. Exposure to short-wavelength light in the morning significantly enhanced CAR compared to dim light. Morning exposure to short-wavelength light may be a simple, yet practical way to better prepare adolescents for an active day. PMID:22899916

Magic wavelengths of the Ca+ ion for circularly polarized light

NASA Astrophysics Data System (ADS)

Jiang, Jun; Jiang, Li; Wang, Xia; Zhang, Deng-Hong; Xie, Lu-You; Dong, Chen-Zhong

2017-10-01

The dynamic dipole polarizabilities of low-lying states of Ca+ ions for circularly polarized light are calculated by using the relativistic configuration interaction plus core polarization approach. The magic wavelengths are determined for the magnetic sublevel transitions 4 s1/2 ,m→4 pj',m' and 4 s1/2 ,m→3 dj',m' with total angular momentum j' and its components m'. In contrast to the case of linearly polarized light, several additional magic wavelengths are found for these transitions. We suggest that accurate measurements on the magic wavelengths near 851 nm for the 4 s1/2 ,m→4 p3/2 ,m' transitions can be used to determine the ratio of the oscillator strengths for the 4 p3/2→3 d3/2 and 4 p3/2→3 d5/2 transitions.

A new real-time non-coherent to coherent light image converter - The hybrid field effect liquid crystal light valve

NASA Technical Reports Server (NTRS)

Grinberg, J.; Jacobson, A.; Bleha, W.; Miller, L.; Fraas, L.; Boswell, D.; Myer, G.

1975-01-01

A new, high-performance device has been developed for application to real-time coherent optical data processing. The new device embodies a CdS photoconductor, a CdTe light-absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The noncoherent image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the ac voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state and the optical birefringence effect to create the bright on-state. The liquid crystal modulates the polarization of the coherent read-out light so an analyzer must be used to create an intensity modulated output beam.

Coherent fiber supercontinuum for biophotonics

PubMed Central

Tu, Haohua; Boppart, Stephen A.

2013-01-01

Biophotonics and nonlinear fiber optics have traditionally been two independent fields. Since the discovery of fiber-based supercontinuum generation in 1999, biophotonics applications employing incoherent light have experienced a large impact from nonlinear fiber optics, primarily because of the access to a wide range of wavelengths and a uniform spatial profile afforded by fiber supercontinuum. However, biophotonics applications employing coherent light have not benefited from the most well-known techniques of supercontinuum generation for reasons such as poor coherence (or high noise), insufficient controllability, and inadequate portability. Fortunately, a few key techniques involving nonlinear fiber optics and femtosecond laser development have emerged to overcome these critical limitations. Despite their relative independence, these techniques are the focus of this review, because they can be integrated into a low-cost portable biophotonics source platform. This platform can be shared across many different areas of research in biophotonics, enabling new applications such as point-of-care coherent optical biomedical imaging. PMID:24358056

Effect of spatial coherence of light on the photoregulation processes in cells

NASA Astrophysics Data System (ADS)

Budagovsky, A. V.; Solovykh, N. V.; Yankovskaya, M. B.; Maslova, M. V.; Budagovskaya, O. N.; Budagovsky, I. A.

2016-07-01

The effect of the statistical properties of light on the value of the photoinduced reaction of the biological objects, which differ in the morphological and physiological characteristics, the optical properties, and the size of cells, was studied. The fruit of apple trees, the pollen of cherries, the microcuttings of blackberries in vitro, and the spores and the mycelium of fungi were irradiated by quasimonochromatic light fluxes with identical energy parameters but different values of coherence length and radius of correlation. In all cases, the greatest stimulation effect occurred when the cells completely fit in the volume of the coherence of the field, while both temporal and spatial coherence have a significant and mathematically certain impact on the physiological activity of cells. It was concluded that not only the spectral, but also the statistical (coherent) properties of the acting light play an important role in the photoregulation process.

Coherent THz Repetitive Pulse Generation in a GaSe Crystal by Dual-wavelength Nd:YLF Laser

NASA Astrophysics Data System (ADS)

Bezotosnyi, V. V.; Cheshev, E. A.; Gorbunkov, M. V.; Koromyslov, A. L.; Krokhin, O. N.; Mityagin, Yu. A.; Popov, Yu. M.; Savinov, S. A.; Tunkin, V. G.

We present modification of difference frequency generator of coherent THz radiation in a nonlinear GaSe crystal using dual-wavelength diode-pumped solid-state Nd:YLF laser. Generation at the two wavelengths (1.047 and 1.053 μm) was carried out by equalization of the gains at these wavelengths near the frequency degeneracy of the transverse modes in resonator cavity, Q-switched by acousto-optical modulator. The main parameters of the device were measured: angular synchronism (width 0.6 degrees), polarization ratio (1:100), conversion efficiency (10-7), pulse power (0.8 mW), frequency and width (53,8 сm-1, 0,6 сm-1), pulse width and repetition rate (10 ns,7 kHz). The method is promising for practical purposes.

Effect of light with different wavelengths on Nostoc flagelliforme cells in liquid culture.

PubMed

Dai, Yu-Jie; Li, Jing; Wei, Shu-Mei; Chen, Nan; Xiao, Yu-Peng; Tan, Zhi-Lei; Jia, Shi-Ru; Yuan, Nan-Nan; Tan, Ning; Song, Yi-Jie

2013-04-01

The effects of lights with different wavelengths on the growth and the yield of extracellular polysaccharides of Nostoc flagelliforme cells were investigated in a liquid cultivation. N. flagelliforme cells were cultured for 16 days in 500 ml conical flasks containing BG11 culture medium under 27 micromol·m-2·s-1 of light intensity and 25 degrees C on a rotary shaker (140 rpm). The chlorophyll a, phycocyanin, allophycocyanin, and phycoerythrin contents in N. flagelliforme cells under the lights of different wavelengths were also measured. It was found that the cell biomass and the yield of polysaccharide changed with different wavelengths of light. The biomass and the yield of extracellular polysaccharides under the red or violet light were higher than those under other light colors. Chlorophyll a, phycocyanin, and allophycocyanin are the main pigments in N. flagelliforme cells. The results showed that N. flagelliforme, like other cyanobacteria, has the ability of adjusting the contents and relative ratio of its pigments with the light quality. As a conclusion, N. flagelliforme cells favor red and violet lights and perform the complementary chromatic adaptation ability to acclimate to the changes of the light quality in the environment.

Coherent white light amplification

DOEpatents

Jovanovic, Igor; Barty, Christopher P.

2004-05-25

A system for coherent simultaneous amplification of a broad spectral range of light that includes an optical parametric amplifier and a source of a seed pulse is described. A first angular dispersive element is operatively connected to the source of a seed pulse. A first imaging telescope is operatively connected to the first angular dispersive element and operatively connected to the optical parametric amplifier. A source of a pump pulse is operatively connected to the optical parametric amplifier. A second imaging telescope is operatively connected to the optical parametric amplifier and a second angular dispersive element is operatively connected to the second imaging telescope.

Light detection and the wavelength shifter deposition in DEAP-3600

NASA Astrophysics Data System (ADS)

Broerman, B.; Retière, F.

2016-02-01

The Dark matter Experiment using Argon Pulse-shape discrimination (DEAP) uses liquid argon as a target medium to perform a direct-detection dark matter search. The 3600 kg liquid argon target volume is housed in a spherical acrylic vessel and viewed by a surrounding array of photomultiplier tubes. Ionizing particles in the argon volume produce scintillation light which must be wavelength shifted to be detected by the photomultiplier tubes. Argon scintillation and wavelength shifting, along with details on the application of the wavelength shifter to the inner surface of the acrylic vessel are presented.

Ultra-broad band, low power, highly efficient coherent wavelength conversion in quantum dot SOA.

PubMed

Contestabile, G; Yoshida, Y; Maruta, A; Kitayama, K

2012-12-03

We report broadband, all-optical wavelength conversion over 100 nm span, in full S- and C-band, with positive conversion efficiency with low optical input power exploiting dual pump Four-Wave-Mixing in a Quantum Dot Semiconductor Optical Amplifier (QD-SOA). We also demonstrate by Error Vector Magnitude analysis the full transparency of the conversion scheme for coherent modulation formats (QPSK, 8-PSK, 16-QAM, OFDM-16QAM) in the whole C-band.

Coherent active polarization control without loss

NASA Astrophysics Data System (ADS)

Ye, Yuqian; Hay, Darrick; Shi, Zhimin

2017-11-01

We propose a lossless active polarization control mechanism utilizing an anisotropic dielectric medium with two coherent inputs. Using scattering matrix analysis, we derive analytically the required optical properties of the anisotropic medium that can behave as a switchable polarizing beam splitter. We also show that such a designed anisotropic medium can produce linearly polarized light at any azimuthal direction through coherent control of two inputs with a specific polarization state. Furthermore, we present a straightforward design-on-demand procedure of a subwavelength-thick metastructure that can possess the desired optical anisotropy at a flexible working wavelength. Our lossless coherent polarization control technique may lead to fast, broadband and integrated polarization control elements for applications in imaging, spectroscopy, and telecommunication.

Frequency conversion of structured light.

PubMed

Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Torres, Juan P

2016-02-15

Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803 nm) to the visible (527 nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging.

Wavelength dependence of coherent and incoherent satellite-based lidar measurements of wind velocity and aerosol backscatter

NASA Technical Reports Server (NTRS)

Kavaya, M. J.; Huffaker, R. M.

1986-01-01

The results are presented of a capability study of Earth orbiting lidar systems, at various wavelengths from 1.06 to 10.6 microns, for the measurement of wind velocity and aerosol backscatter, and for the detection of clouds. Both coherent and incoherent lidar systems were modeled and compared for the aerosol backscatter and cloud detection applications.

Visual resolution in incoherent and coherent light: preliminary investigation

NASA Astrophysics Data System (ADS)

Sarnowska-Habrat, Katarzyna; Dubik, Boguslawa; Zajac, Marek

2001-05-01

In ophthalmology and optometry a number of measures are used for describing quality of human vision such as resolution, visual acuity, contrast sensitivity function, etc. In this paper we will concentrate on the vision quality understood as a resolution of periodic object being a set of equidistant parallel lines of given spacing and direction. The measurement procedure is based on presenting the test to the investigated person and determining the highest spatial frequency he/she can still resolve. In this paper we describe a number of experiments in which we use test tables illuminated with light both coherent and incoherent of different spectral characteristics. Our experiments suggest that while considering incoherent polychromatic illumination the resolution in blue light is substantially worse than in white light. In coherent illumination speckling effect causes worsening of resolution. While using laser light it is easy to generate a sinusoidal interference pattern which can serve as test object. In the paper we compare the results of resolution measurements with test tables and interference fringes.

Dual wavelength multiple-angle light scattering system for cryptosporidium detection

NASA Astrophysics Data System (ADS)

Buaprathoom, S.; Pedley, S.; Sweeney, S. J.

2012-06-01

A simple, dual wavelength, multiple-angle, light scattering system has been developed for detecting cryptosporidium suspended in water. Cryptosporidium is a coccidial protozoan parasite causing cryptosporidiosis; a diarrheal disease of varying severity. The parasite is transmitted by ingestion of contaminated water, particularly drinking-water, but also accidental ingestion of bathing-water, including swimming pools. It is therefore important to be able to detect these parasites quickly, so that remedial action can be taken to reduce the risk of infection. The proposed system combines multiple-angle scattering detection of a single and two wavelengths, to collect relative wavelength angle-resolved scattering phase functions from tested suspension, and multivariate data analysis techniques to obtain characterizing information of samples under investigation. The system was designed to be simple, portable and inexpensive. It employs two diode lasers (violet InGaN-based and red AlGaInP-based) as light sources and silicon photodiodes as detectors and optical components, all of which are readily available. The measured scattering patterns using the dual wavelength system showed that the relative wavelength angle-resolved scattering pattern of cryptosporidium oocysts was significantly different from other particles (e.g. polystyrene latex sphere, E.coli). The single wavelength set up was applied for cryptosporidium oocysts'size and relative refractive index measurement and differential measurement of the concentration of cryptosporidium oocysts suspended in water and mixed polystyrene latex sphere suspension. The measurement results showed good agreement with the control reference values. These results indicate that the proposed method could potentially be applied to online detection in a water quality control system.

Enhancing light-harvesting power with coherent vibrational interactions: A quantum heat engine picture

NASA Astrophysics Data System (ADS)

Killoran, N.; Huelga, S. F.; Plenio, M. B.

2015-10-01

Recent evidence suggests that quantum effects may have functional importance in biological light-harvesting systems. Along with delocalized electronic excitations, it is now suspected that quantum coherent interactions with certain near-resonant vibrations may contribute to light-harvesting performance. However, the actual quantum advantage offered by such coherent vibrational interactions has not yet been established. We investigate a quantum design principle, whereby coherent exchange of single energy quanta between electronic and vibrational degrees of freedom can enhance a light-harvesting system's power above what is possible by thermal mechanisms alone. We present a prototype quantum heat engine which cleanly illustrates this quantum design principle and quantifies its quantum advantage using thermodynamic measures of performance. We also demonstrate the principle's relevance in parameter regimes connected to natural light-harvesting structures.

Wavelength adjustability of frequency conversion light of Yb-doped fiber laser based on FBGs

NASA Astrophysics Data System (ADS)

Dobashi, Kazuma; Tomihari, Yasuhiro; Imai, Koichi; Hirohashi, Junji; Makio, Satoshi

2018-02-01

We focused on wavelength conversion of simple and compact CW Yb-Doped fiber laser based on FBGs with wavelength adjustable function. By controlling temperatures of FBGs in fiber laser, it was possible to tune oscillated wavelength from 1064.101 nm to 1064.414 nm with more than 20 W in CW operation mode. Based on this fundamental light, frequency converted light (SHG and THG) were generated by utilizing two PP:Mg-SLT devises. We obtained more than 3 W of SHG light with tuning range of 150 pm and more than 35 mW of THG with tuning range of 100 pm. By selecting FBG grating and QPM grating properly, we can realize adjustable wavelength laser with the same scheme from 1040 nm to 1090 nm and their SHG/THG. With this combination of FBG based fiber laser and QPM devices, it is possible to tune the wavelength just by temperature tuning without any changes of beam shape and beam pointing.

Numerical dispersion compensation for Partial Coherence Interferometry and Optical Coherence Tomography.

PubMed

Fercher, A; Hitzenberger, C; Sticker, M; Zawadzki, R; Karamata, B; Lasser, T

2001-12-03

Dispersive samples introduce a wavelength dependent phase distortion to the probe beam. This leads to a noticeable loss of depth resolution in high resolution OCT using broadband light sources. The standard technique to avoid this consequence is to balance the dispersion of the sample byarrangingadispersive materialinthereference arm. However, the impact of dispersion is depth dependent. A corresponding depth dependent dispersion balancing technique is diffcult to implement. Here we present a numerical dispersion compensation technique for Partial Coherence Interferometry (PCI) and Optical Coherence Tomography (OCT) based on numerical correlation of the depth scan signal with a depth variant kernel. It can be used a posteriori and provides depth dependent dispersion compensation. Examples of dispersion compensated depth scan signals obtained from microscope cover glasses are presented.

Fusion pumped light source

DOEpatents

Pappas, Daniel S.

1989-01-01

Apparatus is provided for generating energy in the form of light radiation. A fusion reactor is provided for generating a long, or continuous, pulse of high-energy neutrons. The neutron flux is coupled directly with the lasing medium. The lasing medium includes a first component selected from Group O of the periodic table of the elements and having a high inelastic scattering cross section. Gamma radiation from the inelastic scattering reactions interacts with the first component to excite the first component, which decays by photon emission at a first output wavelength. The first output wavelength may be shifted to a second output wavelength using a second liquid component responsive to the first output wavelength. The light outputs may be converted to a coherent laser output by incorporating conventional optics adjacent the laser medium.

Large-aperture ground glass surface profile measurement using coherence scanning interferometry.

PubMed

Bae, Eundeok; Kim, Yunseok; Park, Sanguk; Kim, Seung-Woo

2017-01-23

We present a coherence scanning interferometer configured to deal with rough glass surfaces exhibiting very low reflectance due to severe sub-surface light scattering. A compound light source is prepared by combining a superluminescent light-emitting diode with an ytterbium-doped fiber amplifier. The light source is attuned to offer a short temporal coherence length of 15 μm but with high spatial coherence to secure an adequate correlogram contrast by delivering strongly unbalanced optical power to the low reflectance target. In addition, the infrared spectral range of the light source is shifted close to the visible side at a 1,038 nm center wavelength, so a digital camera of multi-mega pixels available for industrial machine vision can be used to improve the correlogram contrast further with better lateral image resolutions. Experimental results obtained from a ground Zerodur mirror of 200 mm aperture size and 0.9 μm rms roughness are discussed to validate the proposed interferometer system.

Encrypted optical storage with wavelength-key and random phase codes.

PubMed

Matoba, O; Javidi, B

1999-11-10

An encrypted optical memory system that uses a wavelength code as well as input and Fourier-plane random phase codes is proposed. Original data are illuminated by a coherent light source with a specified wavelength and are then encrypted with two random phase codes before being stored holographically in a photorefractive material. Successful decryption requires the use of a readout beam with the same wavelength as that used in the recording, in addition to the correct phase key in the Fourier plane. The wavelength selectivity of the proposed system is evaluated numerically. We show that the number of available wavelength keys depends on the correlation length of the phase key in the Fourier plane. Preliminary experiments of encryption and decryption of optical memory in a LiNbO(3):Fe photorefractive crystal are demonstrated.

Modeling the role of mid-wavelength cones in circadian responses to light

PubMed Central

Dkhissi-Benyahya, Ouria; Gronfier, Claude; De Vanssay, Wena; Flamant, Frédéric; Cooper, Howard M.

2007-01-01

Summary Non-visual responses to light, such as photic entrainment of the circadian clock, involve intrinsically light sensitive melanopsin-expressing ganglion cells as well as rod and cone photoreceptors. However, previous studies have been unable to demonstrate a specific contribution of cones in the photic control of circadian responses to light. Using a mouse model that specifically lacks mid-wavelength (MW) cones we show that these photoreceptors play a significant role in light entrainment and in phase shifting of the circadian oscillator. The contribution of MW cones is mainly observed for light exposures of short duration and towards the longer wavelength region of the spectrum, consistent with the known properties of this opsin. Modelling the contributions of the various photoreceptors stresses the importance of considering the particular spectral, temporal and irradiance response domains of the photopigments when assessing their role and contribution in circadian responses to light. PMID:17329208

Role of light wavelengths in synchronization of circadian physiology in songbirds.

PubMed

Yadav, G; Malik, S; Rani, S; Kumar, V

2015-03-01

This study investigated whether at identical duration and equal energy level birds presented with short (450nm; blue, B) and long (640nm; red, R) light wavelengths would differentially interpret them and exhibit wavelength-dependent circadian behavioral and physiological responses, despite the difference in their breeding latitudes. Temperate migratory blackheaded buntings (Emberiza melanocephala) and subtropical non-migratory Indian weaverbirds (Ploceus philippinus) initially entrained to 12h light:12h darkness (12L:12D; L=0.33μM/m(2)/s, D=0μM/m(2)/s) in two groups of each, groups 1 and 2, were subjected to constant light (LL, 0.33μM/m(2)/s), which rendered them arrhythmic in the activity behavior. They were then exposed for about two weeks each to 12B:12R and 12R:12B (group 1) or 12R:12B and 12B:12R (group 2) at 0.33μM/m(2)/s light energy level. Blue and red light periods were interpreted as the day and night, respectively, with activity and no-activity in non-migratory weaverbirds or activity and intense activity (Zugunruhe, migratory night restlessness) in the migratory buntings. Consistent with this, plasma melatonin levels under B:R, not R:B, light cycle were low and high in blue and red light periods, respectively. A similar diurnal pattern was absent in the cortisol levels, however. These results show an important role of light wavelengths in synchronization of the circadian clock governed behavior and physiology to the photoperiodic environment, and suggest that photoperiodic timing might be a conserved physiological adaptation in many more birds, regardless of the difference in breeding latitudes, than has been generally envisaged. Copyright © 2014 Elsevier Inc. All rights reserved.

Enhancing light-harvesting power with coherent vibrational interactions: A quantum heat engine picture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Killoran, N.; Huelga, S. F.; Plenio, M. B.

Recent evidence suggests that quantum effects may have functional importance in biological light-harvesting systems. Along with delocalized electronic excitations, it is now suspected that quantum coherent interactions with certain near-resonant vibrations may contribute to light-harvesting performance. However, the actual quantum advantage offered by such coherent vibrational interactions has not yet been established. We investigate a quantum design principle, whereby coherent exchange of single energy quanta between electronic and vibrational degrees of freedom can enhance a light-harvesting system’s power above what is possible by thermal mechanisms alone. We present a prototype quantum heat engine which cleanly illustrates this quantum design principlemore » and quantifies its quantum advantage using thermodynamic measures of performance. We also demonstrate the principle’s relevance in parameter regimes connected to natural light-harvesting structures.« less

Coupled-mode propagation in multicore fibers characterized by optical low-coherence reflectometry.

PubMed

Salathé, R P; Gilgen, H; Bodmer, G

1996-07-01

A fiber-optical low-coherence ref lectometer has been used to probe a multicore fiber locally at a wavelength of 1.3 microm. This technique allows one to determine the group index of refraction of the modes in the multicore fiber with high accuracy. Light propagation that is due to noncoherent coupling of energy from one fiber core to adjacent cores through cladding modes can be distinguished quantitatively from light propagating in coherently coupled modes. Intercore coupling constants in the range of 0.6-2 mm(-1) have been evaluated for the coupled modes.

Liquid argon scintillation detection utilizing wavelength-shifting plates and light guides

NASA Astrophysics Data System (ADS)

Howard, B.

2018-02-01

In DUNE, the event timing provided by the detection of the relatively prompt scintillation photons will improve spatial resolution in the drift direction of the time-projection chamber (TPC) and is especially useful for non-beam physics topics such as supernova neutrinos and nucleon decay. The baseline design for the first 10kt single phase TPC fits the photon detector system in the natural gap between the wire planes of adjacent TPC volumes. A prototype photon detector design utilizes wavelength-shifter coated plates to convert the vacuum ultraviolet scintillation light to the optical and commercially-produced wavelength-shifting light guides to trap some of this light and transport it to an array of silicon photomultipliers at the end. This system and the testing performed to characterize the system and determine the efficiency are discussed.

Long Wavelength Electromagnetic Light Bullets Generated by a 10.6 micron CO2 Ultrashort Pulsed Source

DTIC Science & Technology

2016-11-29

AFRL-AFOSR-VA-TR-2016-0365 Long Wavelength Electromagnetic Light Bullets Generated by a 10.6 micron CO2 Ultrashort Pulsed Source Jerome Moloney...SUBTITLE "Long Wavelength Electromagnetic Light Bullets Generated by a 10.6 micron CO2 Ultrashort Pulsed Source 5a. CONTRACT NUMBER FA9550-15-1-0272 5b...afosr.reports.sgizmo.com/s3/> Subject: Final Report to Dr. Arje Nachman Contract/Grant Title: Long Wavelength Electromagnetic Light Bullets Generated by a 10.6

Artificial light pollution: Shifting spectral wavelengths to mitigate physiological and health consequences in a nocturnal marsupial mammal.

PubMed

Dimovski, Alicia M; Robert, Kylie A

2018-05-02

The focus of sustainable lighting tends to be on reduced CO 2 emissions and cost savings, but not on the wider environmental effects. Ironically, the introduction of energy-efficient lighting, such as light emitting diodes (LEDs), may be having a great impact on the health of wildlife. These white LEDs are generated with a high content of short-wavelength 'blue' light. While light of any kind can suppress melatonin and the physiological processes it regulates, these short wavelengths are potent suppressors of melatonin. Here, we manipulated the spectral composition of LED lights and tested their capacity to mitigate the physiological and health consequences associated with their use. We experimentally investigated the impact of white LEDs (peak wavelength 448 nm; mean irradiance 2.87 W/m 2 ), long-wavelength shifted amber LEDs (peak wavelength 605 nm; mean irradiance 2.00 W/m 2 ), and no lighting (irradiance from sky glow < 0.37 × 10 -3 W/m 2 ), on melatonin production, lipid peroxidation, and circulating antioxidant capacity in the tammar wallaby (Macropus eugenii). Night-time melatonin and oxidative status were determined at baseline and again following 10 weeks exposure to light treatments. White LED exposed wallabies had significantly suppressed nocturnal melatonin compared to no light and amber LED exposed wallabies, while there was no difference in lipid peroxidation. Antioxidant capacity declined from baseline to week 10 under all treatments. These results provide further evidence that short-wavelength light at night is a potent suppressor of nocturnal melatonin. Importantly, we also illustrate that shifting the spectral output to longer wavelengths could mitigate these negative physiological impacts. © 2018 Wiley Periodicals, Inc.

Goos-Hänchen shifts of partially coherent light beams from a cavity with a four-level Raman gain medium

NASA Astrophysics Data System (ADS)

Ziauddin; Lee, Ray-Kuang; Qamar, Sajid

2016-09-01

We theoretically investigate spatial and angular Goos-Hänchen (GH) shifts (both negative and positive) in the reflected light for a partial coherent light incident on a cavity. A four-level Raman gain atomic medium is considered in a cavity. The effects of spatial coherence, beam width, and mode index of partial coherent light fields on spatial and angular GH shifts are studied. Our results reveal that a large magnitude of negative and positive GH shifts in the reflected light is achievable with the introduction of partial coherent light fields. Furthermore, the amplitude of spatial (negative and positive) GH shifts are sharply affected by the partial coherent light beam as compared to angular (negative and positive) GH shifts in the reflected light.

Coherent control of optical polarization effects in metamaterials

PubMed Central

Mousavi, Seyedmohammad A.; Plum, Eric; Shi, Jinhui; Zheludev, Nikolay I.

2015-01-01

Processing of photonic information usually relies on electronics. Aiming to avoid the conversion between photonic and electronic signals, modulation of light with light based on optical nonlinearity has become a major research field and coherent optical effects on the nanoscale are emerging as new means of handling and distributing signals. Here we demonstrate that in slabs of linear material of sub-wavelength thickness optical manifestations of birefringence and optical activity (linear and circular birefringence and dichroism) can be controlled by a wave coherent with the wave probing the polarization effect. We demonstrate this in proof-of-principle experiments for chiral and anisotropic microwave metamaterials, where we show that the large parameter space of polarization characteristics may be accessed at will by coherent control. Such control can be exerted at arbitrarily low intensities, thus arguably allowing for fast handling of electromagnetic signals without facing thermal management and energy challenges. PMID:25755071

Time-dependent scattering of incident light of various wavelengths in ferrofluids under external magnetic field

NASA Astrophysics Data System (ADS)

Jin, Jingyu; Song, Dongxing; Geng, Jiafeng; Jing, Dengwei

2018-02-01

Ferrofluids can exhibit the anisotropic thermodynamic properties under magnetic fields. The dynamic optical properties of ferrofluids in the presence of magnetic fields are of particular interest due to their potential application as various optical devices. Although time-dependent light scattering by ferrofluids have been extensively studied, the effect of wavelength of incident light have been rarely considered. Here, for the first time, we investigated both the time- and wavelength-dependent light scattering in water based ferrofluids containing Fe3O4 nanoparticles under an external magnetic field. The field-induced response behavior of the prepared ferrofluid samples was determined and verified first by thermal conductivity measurement and numerical simulation. Double-beam UV-Vis spectrophotometer was employed to record the temporal evolution of transmitted intensity of incident light of various wavelengths passing through the ferrofluid sample and propagating parallel to the applied field. As expected, the light intensity decreases to a certain value right after the field is turned on due to the thermal fluctuation induced disorder inside the flexible particle chains. Then the light intensity further decreases with time until the appearance of a minimum at time τ0 followed by an inversed increase before finally reaches equilibrium at a particular time. More importantly, the characteristic inversion time τ0 was found to follow a power law increase with the wavelength of incident light (τ0 ∼ λα, where α = 2.07). A quantitative explanation for the wavelength dependence of characteristic time was proposed based on the finite-difference time-domain (FDTD) method. The simulation results are in good agreement with our experimental observations. The time-dependent light scattering in ferrofluids under different incident wavelengths was rationalized by considering both the coarsening process of the particle chains and the occurrence of resonance within the

Effects of light wavelengths on extracellular and capsular polysaccharide production by Nostoc flagelliforme.

PubMed

Han, Pei-pei; Sun, Ying; Jia, Shi-ru; Zhong, Cheng; Tan, Zhi-lei

2014-05-25

The influences of different wavelengths of light (red 660nm, yellow 590nm, green 520nm, blue 460nm, purple 400nm) and white light on extracellular polysaccharide (EPS) and capsular polysaccharide (CPS) production by Nostoc flagelliforme in liquid culture were demonstrated in this study. The results showed that, compared with white light, red and blue lights significantly increased both EPS and CPS production while yellow light reduced their production; purple and green lights stimulated EPS production but inhibited CPS formation. Nine constituent monosaccharides and one uronic acid were detected in both EPS and CPS, and their ratios showed significant differences among treatment with different light wavelengths. However, the advanced structure of EPS and CPS from various light conditions did not present obvious difference through Fourier transform infrared spectroscopy and X-ray diffraction characterization. These findings establish a basis for development of high-yielding polysaccharide production process and understanding their regulation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Low-Level Light Stimulates Excisional Wound Healing in Mice

PubMed Central

Demidova-Rice, Tatiana N.; Salomatina, Elena V.; Yaroslavsky, Anna N.; Herman, Ira M.; Hamblin, Michael R.

2010-01-01

Background Low levels of laser or non-coherent light, termed low-level light therapy (LLLT) have been reported to accelerate some phases of wound healing, but its clinical use remains controversial. Methods A full thickness dorsal excisional wound in mice was treated with a single exposure to light of various wavelengths and fluences 30 minutes after wounding. Wound areas were measured until complete healing and immunofluorescence staining of tissue samples was carried out. Results Wound healing was significantly stimulated in BALB/c and SKH1 hairless mice but not in C57BL/6 mice. Illuminated wounds started to contract while control wounds initially expanded for the first 24 hours. We found a biphasic dose–response curve for fluence of 635-nm light with a maximum positive effect at 2 J/cm2. Eight hundred twenty nanometer was found to be the best wavelength tested compared to 635, 670, and 720 nm. We found no difference between non-coherent 635 ± 15-nm light from a lamp and coherent 633-nm light from a He/Ne laser. LLLT increased the number of α-smooth muscle actin (SMA)-positive cells at the wound edge. Conclusion LLLT stimulates wound contraction in susceptible mouse strains but the mechanism remains uncertain. PMID:17960752

Characterization of single particle aerosols by elastic light scattering at multiple wavelengths

NASA Astrophysics Data System (ADS)

Lane, P. A.; Hart, M. B.; Jain, V.; Tucker, J. E.; Eversole, J. D.

2018-03-01

We describe a system to characterize individual aerosol particles using stable and repeatable measurement of elastic light scattering. The method employs a linear electrodynamic quadrupole (LEQ) particle trap. Charged particles, continuously injected by electrospray into this system, are confined to move vertically along the stability line in the center of the LEQ past a point where they are optically interrogated. Light scattered in the near forward direction was measured at three different wavelengths using time-division multiplexed collinear laser beams. We validated our method by comparing measured silica microsphere data for four selected diameters (0.7, 1.0, 1.5 and 2.0 μm) to a model of collected scattered light intensities based upon Lorenz-Mie scattering theory. Scattered light measurements at the different wavelengths are correlated, allowing us to distinguish and classify inhomogeneous particles.

Multispectral cross-polarization reflectance measurements suggest high contrast of demineralization on tooth surfaces at wavelengths beyond 1300 nm due to reduced light scattering in sound enamel.

PubMed

Chan, Kenneth H; Fried, Daniel

2018-06-01

The enamel scattering coefficient decreases markedly with increasing wavelength from the visible to the near-infrared (NIR). However, beyond 1300 nm, the scattering coefficient is difficult to measure, and it is not known whether light scattering continues to decrease significantly at longer wavelengths. It is hypothesized that water absorption is a major contributor to the contrast between sound and demineralized enamel beyond 1300 nm since deeply penetrating photons in sound enamel are likely absorbed by water. Reflectance images of demineralization on tooth surfaces were acquired at wavelengths near 1450, 1860, 1880, and 1950 nm. The magnitude of water absorption is similar at 1450 and 1880 nm but varies markedly between 1860, 1880, and 1950 nm. Multispectral comparisons of lesion contrast provide insight into the mechanism responsible for higher contrast at longer NIR wavelengths. The highest contrast was at 1950 nm; however, the markedly higher contrast at 1880 compared to 1450 nm and similar contrast between 1860 and 1880 nm suggests that the enamel scattering coefficient continues to decrease beyond 1300 nm, and that reduced light scattering in sound enamel is most responsible for the higher lesion contrast at longer NIR wavelengths. This has important implications for the choice of wavelengths for caries detection and diagnostic devices, including the performance of optical coherence tomography beyond 1300 nm. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Coherent ultra dense wavelength division multiplexing passive optical networks

NASA Astrophysics Data System (ADS)

Shahpari, Ali; Ferreira, Ricardo; Ribeiro, Vitor; Sousa, Artur; Ziaie, Somayeh; Tavares, Ana; Vujicic, Zoran; Guiomar, Fernando P.; Reis, Jacklyn D.; Pinto, Armando N.; Teixeira, António

2015-12-01

In this paper, we firstly review the progress in ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON), by making use of the key attributes of this technology in the context of optical access and metro networks. Besides the inherit properties of coherent technology, we explore different modulation formats and pulse shaping. The performance is experimentally demonstrated through a 12 × 10 Gb/s bidirectional UDWDM-PON over hybrid 80 km standard single mode fiber (SSMF) and optical wireless link. High density, 6.25 GHz grid, Nyquist shaped 16-ary quadrature amplitude modulation (16QAM) and digital frequency shifting are some of the properties exploited together in the tests. Also, bidirectional transmission in fiber, relevant in the context, is analyzed in terms of nonlinear and back-reflection effects on receiver sensitivity. In addition, as a basis for the discussion on market readiness, we experimentally demonstrate real-time detection of a Nyquist-shaped quaternary phase-shift keying (QPSK) signal using simple 8-bit digital signal processing (DSP) on a field-programmable gate array (FPGA).

Overlapped optics induced perfect coherent effects.

PubMed

Li, Jian Jie; Zang, Xiao Fei; Mao, Jun Fa; Tang, Min; Zhu, Yi Ming; Zhuang, Song Lin

2013-12-20

For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.

Upconverting device for enhanced recogntion of certain wavelengths of light

DOEpatents

Kross, Brian; McKIsson, John E; McKisson, John; Weisenberger, Andrew; Xi, Wenze; Zorn, Carl

2013-05-21

An upconverting device for enhanced recognition of selected wavelengths is provided. The device comprises a transparent light transmitter in combination with a plurality of upconverting nanoparticles. The device may a lens in eyewear or alternatively a transparent panel such as a window in an instrument or machine. In use the upconverting device is positioned between a light source and the eye(s) of the user of the upconverting device.

Development of ultraviolet- and visible-light one-shot spectral domain optical coherence tomography and in situ measurements of human skin

NASA Astrophysics Data System (ADS)

Hirayama, Heijiro; Nakamura, Sohichiro

2015-07-01

We have developed ultraviolet (UV)- and visible-light one-shot spectral domain (SD) optical coherence tomography (OCT) that enables in situ imaging of human skin with an arbitrary wavelength in the UV-visible-light region (370-800 nm). We alleviated the computational burden for each color OCT image by physically dispersing the irradiating light with a color filter. The system consists of SD-OCT with multicylindrical lenses; thus, mechanical scanning of the mirror or stage is unnecessary to obtain an OCT image. Therefore, only a few dozens of milliseconds are necessary to obtain single-image data. We acquired OCT images of one subject's skin in vivo and of a skin excision ex vivo for red (R, 650±20 nm), green (G, 550±20 nm), blue (B, 450±20 nm), and UV (397±5 nm) light. In the visible-light spectrum, R light penetrated the skin and was reflected at a lower depth than G or B light. On the skin excision, we demonstrated that UV light reached the dermal layer. We anticipated that basic knowledge about the spectral properties of human skin in the depth direction could be acquired with this system.

Development of ultraviolet- and visible-light one-shot spectral domain optical coherence tomography and in situ measurements of human skin.

PubMed

Hirayama, Heijiro; Nakamura, Sohichiro

2015-07-01

We have developed ultraviolet (UV)- and visible-light one-shot spectral domain (SD) optical coherence tomography (OCT) that enables in situ imaging of human skin with an arbitrary wavelength in the UV-visible-light region (370-800 nm). We alleviated the computational burden for each color OCT image by physically dispersing the irradiating light with a color filter. The system consists of SD-OCT with multicylindrical lenses; thus, mechanical scanning of the mirror or stage is unnecessary to obtain an OCT image. Therefore, only a few dozens of milliseconds are necessary to obtain single-image data. We acquired OCT images of one subject's skin in vivo and of a skin excision ex vivo for red (R, 650 ± 20 nm), green (G, 550 ± 20 nm), blue (B, 450 ± 20 nm), and UV (397 ± 5 nm) light. In the visible-light spectrum, R light penetrated the skin and was reflected at a lower depth than G or B light. On the skin excision, we demonstrated that UV light reached the dermal layer. We anticipated that basic knowledge about the spectral properties of human skin in the depth direction could be acquired with this system.

Experimental demonstration of quantum digital signatures using phase-encoded coherent states of light

PubMed Central

Clarke, Patrick J.; Collins, Robert J.; Dunjko, Vedran; Andersson, Erika; Jeffers, John; Buller, Gerald S.

2012-01-01

Digital signatures are frequently used in data transfer to prevent impersonation, repudiation and message tampering. Currently used classical digital signature schemes rely on public key encryption techniques, where the complexity of so-called ‘one-way' mathematical functions is used to provide security over sufficiently long timescales. No mathematical proofs are known for the long-term security of such techniques. Quantum digital signatures offer a means of sending a message, which cannot be forged or repudiated, with security verified by information-theoretical limits and quantum mechanics. Here we demonstrate an experimental system, which distributes quantum signatures from one sender to two receivers and enables message sending ensured against forging and repudiation. Additionally, we analyse the security of the system in some typical scenarios. Our system is based on the interference of phase-encoded coherent states of light and our implementation utilizes polarization-maintaining optical fibre and photons with a wavelength of 850 nm. PMID:23132024

Investigating the contribution of short wavelengths in the alerting effect of bright light.

PubMed

Sasseville, Alexandre; Martin, Jeanne Sophie; Houle, Jérôme; Hébert, Marc

2015-11-01

Short-wavelengths can have an acute impact on alertness, which is allegedly due to their action on intrinsically photosensitive retinal ganglion cells. Classical photoreceptors cannot, however, be excluded at this point in time as contributors to the alerting effect of light. The objective of this study was to compare the alerting effect at night of a white LED light source while wearing blue-blockers or not, in order to establish the contribution of short-wavelengths. 20 participants stayed awake under dim light (< 5 lx) from 23:00 h to 04:00 h on two consecutive nights. On the second night, participants were randomly assigned to one light condition for 30 min starting at 3:00 h. Group A (5M/5F) was exposed to 500 μW/cm(2) of unfiltered LED light, while group B (4M/6F) was required to wear blue-blocking glasses, while exposed to 1500 μW/cm(2) from the same light device in order to achieve 500 μW/cm(2) at eye level (as measured behind the glasses). Subjective alertness, energy, mood and anxiety were assessed for both nights at 23:30 h, 01:30 h and 03:30 h using a visual analog scale (VAS). Subjective sleepiness was assessed with the Stanford Sleepiness Scale (SSS). Subjects also performed the Conners' Continuous Performance Test II (CPT-II) in order to assess objective alertness. Mixed model analysis was used to compare VAS, SSS and CPT-II parameters. No difference between group A and group B was observed for subjective alertness, energy, mood, anxiety and sleepiness, as well as CPT-II parameters. Subjective alertness (p < 0.001), energy (p < 0.001) and sleepiness (p < 0.05) were, however improved after light exposure on the second night independently of the light condition. The current study shows that when sleepiness is high, the alerting effect of light can still be triggered at night in the absence of short-wavelengths with a 30 minute light pulse of 500 μW/cm(2). This suggests that the underlying mechanism by which a brief polychromatic light exposure

Laser-assisted decontamination—A wavelength dependent study

NASA Astrophysics Data System (ADS)

Nilaya, J. Padma; Raote, Pallavi; Kumar, Aniruddha; Biswas, Dhruba J.

2008-09-01

We present here the experimental results on cleaning of radioactive dielectric particulates, loosely deposited on stainless steel, by coherent light of 1064 nm wavelength and its three harmonics occurring at 532 nm, 355 nm and 266 nm, derived from an Nd-YAG laser. For the initial few exposures, the decontamination factor has been found to be highest when exposed to 1064 nm radiation. With increasing number of exposures, however, the radiation with reducing wavelength assumes a more important role as a cleaning agent. The observation of almost no cleaning with 1064 nm and much reduced cleaning with its harmonics when the contamination is deposited on a transparent substrate confirms the dominant role played by metal substrate towards expelling the loose particulates from its surface.

Control of cell interaction using quasi-monochromatic light with varying spatiotemporal coherence

NASA Astrophysics Data System (ADS)

Budagovsky, A. V.; Maslova, M. V.; Budagovskaya, O. N.; Budagovsky, I. A.

2017-02-01

By the example of plants, fungi and bacteria, we consider the possibility of controlling the interaction of cells, being in competitive, antagonistic, or parasitic relations. For this aim we used short-time irradiation (a few seconds or minutes) with the red (633 nm) quasi-monochromatic light having different spatiotemporal coherence. It is shown that the functional activity is mostly increased in the cells whose size does not exceed the coherence length and the correlation radius of the light field. Thus, in the case of cells essentially differing in size, it is possible to increase the activity of smaller cells, avoiding the stimulation of larger ones. For example, the radiation having relatively low coherence (Lcoh, rcor <= 10 μm) facilitates mainly the damage of large-size plant cells by pathogen fungi, while the exposure to light with less statistical regularity (Lcoh = 4 μm, rcor = 5 μm) inhibits the growth of the Fusarium microcera fungus, infected by the bacterium of the Pseudomonas species. The quasi-monochromatic radiation with sufficiently high spatiotemporal coherence stimulated all interacting species (bacteria, fungi, plants). In the considered biocenosis, the equilibrium was shifted towards the favour of organisms having the highest rate of cell division or the ones better using their adaptation potential.

Mesoscopic coherence in light scattering from cold, optically dense and disordered atomic systems

NASA Astrophysics Data System (ADS)

Kupriyanov, D. V.; Sokolov, I. M.; Havey, M. D.

2017-02-01

Coherent effects manifested in light scattering from cold, optically dense and disordered atomic systems are reviewed from a primarily theoretical point of view. Development of the basic theoretical tools is then elaborated through several physical atomic physics based processes which have been at least partly explored experimentally. These include illustrations drawn from the coherent backscattering effect, random lasing in atomic gases, quantum memories and light-atoms interface assisted by the light trapping mechanism. Current understanding and challenges associated with the transition to high atomic densities and cooperativity in the scattering process are also discussed in some detail.

Coherence Length and Vibrations of the Coherence Beamline I13 at the Diamond Light Source

NASA Astrophysics Data System (ADS)

Wagner, U. H.; Parson, A.; Rau, C.

2017-06-01

I13 is a 250 m long hard x-ray beamline for imaging and coherent diffraction at the Diamond Light Source. The beamline (6 keV to 35 keV) comprises two independent experimental endstations: one for imaging in direct space using x-ray microscopy and one for imaging in reciprocal space using coherent diffraction based imaging techniques [1]. In particular the coherence experiments pose very high demands on the performance on the beamline instrumentation, requiring extensive testing and optimisation of each component, even during the assembly phase. Various aspects like the quality of optical components, the mechanical design concept, vibrations, drifts, thermal influences and the performance of motion systems are of particular importance. In this paper we study the impact of the front-end slit size (FE slit size), which determines the horizontal source size, onto the coherence length and the detrimental impact of monochromator vibrations using in-situ x-ray metrology in conjunction with fringe visibility measurements and vibration measurements, based on centroid tracking of an x-ray pencil beam with a photon-counting detector.

Effect of multi-wavelength irradiation on color characterization with light-emitting diodes (LEDs)

NASA Astrophysics Data System (ADS)

Park, Hyeong Ju; Song, Woosub; Lee, Byeong-Il; Kim, Hyejin; Kang, Hyun Wook

2017-06-01

In the current study, a multi-wavelength light-emitting diode (LED)-integrated CMOS imaging device was developed to investigate the effect of various wavelengths on multiple color characterization. Various color pigments (black, red, green, and blue) were applied on both white paper and skin phantom surfaces for quantitative analysis. The artificial skin phantoms were made of polydimethylsiloxane (PDMS) mixed with coffee and TiO2 powder to emulate the optical properties of the human dermis. The customized LED-integrated imaging device acquired images of the applied pigments by sequentially irradiating with the LED lights in the order of white, red, green, and blue. Each color pigment induced a lower contrast during illumination by the light with the equivalent color. However, the illumination by light with the complementary (opposite) color increased the signal-to-noise ratio by up to 11-fold due to the formation of a strong contrast ( i.e., red LED = 1.6 ± 0.3 vs. green LED = 19.0 ± 0.6 for red pigment). Detection of color pigments in conjunction with multi-wavelength LEDs can be a simple and reliable technique to estimate variations in the color pigments quantitatively.

Simulating propagation of coherent light in random media using the Fredholm type integral equation

NASA Astrophysics Data System (ADS)

Kraszewski, Maciej; Pluciński, Jerzy

2017-06-01

Studying propagation of light in random scattering materials is important for both basic and applied research. Such studies often require usage of numerical method for simulating behavior of light beams in random media. However, if such simulations require consideration of coherence properties of light, they may become a complex numerical problems. There are well established methods for simulating multiple scattering of light (e.g. Radiative Transfer Theory and Monte Carlo methods) but they do not treat coherence properties of light directly. Some variations of these methods allows to predict behavior of coherent light but only for an averaged realization of the scattering medium. This limits their application in studying many physical phenomena connected to a specific distribution of scattering particles (e.g. laser speckle). In general, numerical simulation of coherent light propagation in a specific realization of random medium is a time- and memory-consuming problem. The goal of the presented research was to develop new efficient method for solving this problem. The method, presented in our earlier works, is based on solving the Fredholm type integral equation, which describes multiple light scattering process. This equation can be discretized and solved numerically using various algorithms e.g. by direct solving the corresponding linear equations system, as well as by using iterative or Monte Carlo solvers. Here we present recent development of this method including its comparison with well-known analytical results and a finite-difference type simulations. We also present extension of the method for problems of multiple scattering of a polarized light on large spherical particles that joins presented mathematical formalism with Mie theory.

The linac coherent light source single particle imaging road map

PubMed Central

Aquila, A.; Barty, A.; Bostedt, C.; Boutet, S.; Carini, G.; dePonte, D.; Drell, P.; Doniach, S.; Downing, K. H.; Earnest, T.; Elmlund, H.; Elser, V.; Gühr, M.; Hajdu, J.; Hastings, J.; Hau-Riege, S. P.; Huang, Z.; Lattman, E. E.; Maia, F. R. N. C.; Marchesini, S.; Ourmazd, A.; Pellegrini, C.; Santra, R.; Schlichting, I.; Schroer, C.; Spence, J. C. H.; Vartanyants, I. A.; Wakatsuki, S.; Weis, W. I.; Williams, G. J.

2015-01-01

Intense femtosecond x-ray pulses from free-electron laser sources allow the imaging of individual particles in a single shot. Early experiments at the Linac Coherent Light Source (LCLS) have led to rapid progress in the field and, so far, coherent diffractive images have been recorded from biological specimens, aerosols, and quantum systems with a few-tens-of-nanometers resolution. In March 2014, LCLS held a workshop to discuss the scientific and technical challenges for reaching the ultimate goal of atomic resolution with single-shot coherent diffractive imaging. This paper summarizes the workshop findings and presents the roadmap toward reaching atomic resolution, 3D imaging at free-electron laser sources. PMID:26798801

The linac coherent light source single particle imaging road map

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aquila, A.; Barty, A.; Bostedt, C.

Intense femtosecond x-ray pulses from free-electron laser sources allow the imaging of individual particles in a single shot. Early experiments at the Linac Coherent Light Source (LCLS) have led to rapid progress in the field and, so far, coherent diffractive images have been recorded from biological specimens, aerosols, and quantum systems with a few-tens-of-nanometers resolution. In March 2014, LCLS held a workshop to discuss the scientific and technical challenges for reaching the ultimate goal of atomic resolution with single-shot coherent diffractive imaging. This paper summarizes the workshop findings and presents the roadmap toward reaching atomic resolution, 3D imaging at free-electronmore » laser sources.« less

Wavelength-Resolved Photon Fluxes of Indoor Light Sources: Implications for HOx Production

NASA Astrophysics Data System (ADS)

Kowal, S.; Kahan, T.

2017-12-01

Only a handful of studies have considered photolytic reactions indoors because photon fluxes at short wavelengths are generally considered to be negligible. We have measured wavelength resolved photon fluxes from indoor light sources including incandescent, halogen, compact fluorescent (CFL), and light emitting diodes (LED). In addition, fluorescent tubes, used in many offices and industrial buildings, and sunlight through windows were measured. The measured photon fluxes were used to calculate photolysis rate constants for potential indoor hydroxyl and peroxy radical (OH and HO2, "HOx") precursors: acetaldehyde (CH3CHO), formaldehyde (HCHO), hydrogen peroxide (H2O2), nitrous acid (HONO) and ozone (O3). Rate constants in conjunction with typical indoor concentrations were used to predict HOx production rates under various lighting conditions. Our results illustrate that all light sources except LEDs emit light at high enough energy to photolyze HOx precursors. Under typical lighting conditions only fluorescent tubes and sunlight will initiate significant photochemical HOx formation, and HONO and HCHO will be the only molecules that will have a strong influence on HOx levels indoors. Data from our experiments can be used in indoor air models to better predict HOx levels indoors.

A high-power fiber-coupled semiconductor light source with low spatio-temporal coherence

NASA Astrophysics Data System (ADS)

Schittko, Robert; Mazurenko, Anton; Tai, M. Eric; Lukin, Alexander; Rispoli, Matthew; Menke, Tim; Kaufman, Adam M.; Greiner, Markus

2017-04-01

Interference-induced distortions pose a significant challenge to a variety of experimental techniques, ranging from full-field imaging applications in biological research to the creation of optical potentials in quantum gas microscopy. Here, we present a design of a high-power, fiber-coupled semiconductor light source with low spatio-temporal coherence that bears the potential to reduce the impact of such distortions. The device is based on an array of non-lasing semiconductor emitters mounted on a single chip whose optical output is coupled into a multi-mode fiber. By populating a large number of fiber modes, the low spatial coherence of the input light is further reduced due to the differing optical path lengths amongst the modes and the short coherence length of the light. In addition to theoretical calculations showcasing the feasibility of this approach, we present experimental measurements verifying the low degree of spatial coherence achievable with such a source, including a detailed analysis of the speckle contrast at the fiber end. We acknowledge support from the National Science Foundation, the Gordon and Betty Moore Foundation's EPiQS Initiative, an Air Force Office of Scientific Research MURI program and an Army Research Office MURI program.

Semiconductor light source with electrically tunable emission wavelength

DOEpatents

Belenky, Gregory [Port Jefferson, NY; Bruno, John D [Bowie, MD; Kisin, Mikhail V [Centereach, NY; Luryi, Serge [Setauket, NY; Shterengas, Leon [Centereach, NY; Suchalkin, Sergey [Centereach, NY; Tober, Richard L [Elkridge, MD

2011-01-25

A semiconductor light source comprises a substrate, lower and upper claddings, a waveguide region with imbedded active area, and electrical contacts to provide voltage necessary for the wavelength tuning. The active region includes single or several heterojunction periods sandwiched between charge accumulation layers. Each of the active region periods comprises higher and lower affinity semiconductor layers with type-II band alignment. The charge carrier accumulation in the charge accumulation layers results in electric field build-up and leads to the formation of generally triangular electron and hole potential wells in the higher and lower affinity layers. Nonequillibrium carriers can be created in the active region by means of electrical injection or optical pumping. The ground state energy in the triangular wells and the radiation wavelength can be tuned by changing the voltage drop across the active region.

Spectroscopic optical coherence tomography based on wavelength de-multiplexing and smart pixel array detection

NASA Astrophysics Data System (ADS)

Laubscher, Markus; Bourquin, Stéphane; Froehly, Luc; Karamata, Boris; Lasser, Theo

2004-07-01

Current spectroscopic optical coherence tomography (OCT) methods rely on a posteriori numerical calculation. We present an experimental alternative for accessing spectroscopic information in OCT without post-processing based on wavelength de-multiplexing and parallel detection using a diffraction grating and a smart pixel detector array. Both a conventional A-scan with high axial resolution and the spectrally resolved measurement are acquired simultaneously. A proof-of-principle demonstration is given on a dynamically changing absorbing sample. The method's potential for fast spectroscopic OCT imaging is discussed. The spectral measurements obtained with this approach are insensitive to scan non-linearities or sample movements.

Photothermal effects in phase shifted FBG with varied light wavelength and intensity.

PubMed

Ding, Meng; Chen, Dijun; Fang, Zujie; Wang, Di; Zhang, Xi; Wei, Fang; Yang, Fei; Ying, Kang; Cai, Haiwen

2016-10-31

The intensity enhancement effect of a phase-shifted fiber Bragg grating (PSFBG) is investigated theoretically and experimentally in this paper. Due to the effect, both of the FBG reflection bands and the transmission peak show red-shift with the increase of pump light wavelength from the shorter side to the longer side of the Bragg wavelength. The transmission peak shifts in pace with the pump's wavelength, which is much faster than the reflection band. The maximum shift increases with the pump power. In contrast, the red-shift is very small when the pump light deceases from the longer side of the Bragg wavelength. Such asymmetric behavior is checked dynamically by using a frequency modulated laser in a serrated wave, showing push-pull behavior. The effect of the characteristics of thermal dissipation conditions is also measured. The fiber loss coefficient of FBG being tested is estimated from the measured data to be about 0.001 mm^-1, which may be attributed to the H₂-loading and UV exposure in FBG fabrication. The observed phenomena are believed of importance in application where PSFBG is utilized as a narrow linewidth filter.

Slow Light Using Electromagnetically Induced Transparency from Spin Coherence in [110] Strained Quantum Wells

NASA Astrophysics Data System (ADS)

Chang, Shu-Wei; Chang-Hasnain, Connie J.; Wang, Hailin

2005-03-01

The electromagnetically induced transparency from spin coherence has been proposed in [001] quantum wells recently. [1] The spin coherence is a potential candidate to demonstrate semiconductor-based slow light at room temperature. However, the spin coherence time is not long enough to demonstrate a significant slowdown factor in [001] quantum wells. Further, the required transition of light-hole excitons lies in the absorption of heavy-hole continuum states. The extra dephasing and absorption from these continuum states are drawbacks for slow light. Here, we propose to use [110] strained quantum wells instead of [001] quantum wells. The long spin relaxation time in [110] quantum wells at room temperature, and thus more robust spin coherence, [2] as well as the strain-induced separation [3, 4] of the light-hole exciton transition from the heavy-hole continuum absorption can help to slow down light in quantum wells. [1] T. Li, H. Wang, N. H. Kwong, and R. Binder, Opt. Express 11, 3298 (2003). [2] Y. Ohno, R. Terauchi, T. Adachi, F. Matsukura, and H. Ohno, Phys. Rev. Lett. 83, 4196 (1999). [3] C. Y. P. Chao and S. L. Chuang, Phys. Rev. B 46, 4110 (1992). [4] C. Jagannath, E. S. Koteles, J. Lee, Y. J. Chen, B. S. Elman, and J. Y. Chi, Phys. Rev. B 34, 7027 (1986).

Wavelength independent interferometer

NASA Technical Reports Server (NTRS)

Hochberg, Eric B. (Inventor); Page, Norman A. (Inventor)

1991-01-01

A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

Transient quantum coherent effects in the acetylene-filled hollow-core photonic crystal fiber

NASA Astrophysics Data System (ADS)

Stepanov, S.; Rodríguez Casillas, N.; Ocegueda Miramontes, M.; Hernández Hernández, E.

2017-02-01

Low-pressure acetylene in the hollow-core photonic crystal structure fibers is an excellent medium for the room-temperature investigation of the coherent quantum effects in communication wavelength region. Pulsed excitation enables observation of new coherent phenomena like optical nutation or photon echo and evaluation of important temporal characteristics of the light-molecule interactions. We also report original experimental results on the pulsed excitation of the electromagnetically induced transparency in co- and counter-propagation configurations.

Population and coherence dynamics in light harvesting complex II (LH2).

PubMed

Yeh, Shu-Hao; Zhu, Jing; Kais, Sabre

2012-08-28

The electronic excitation population and coherence dynamics in the chromophores of the photosynthetic light harvesting complex 2 (LH2) B850 ring from purple bacteria (Rhodopseudomonas acidophila) have been studied theoretically at both physiological and cryogenic temperatures. Similar to the well-studied Fenna-Matthews-Olson (FMO) protein, oscillations of the excitation population and coherence in the site basis are observed in LH2 by using a scaled hierarchical equation of motion approach. However, this oscillation time (300 fs) is much shorter compared to the FMO protein (650 fs) at cryogenic temperature. Both environment and high temperature are found to enhance the propagation speed of the exciton wave packet yet they shorten the coherence time and suppress the oscillation amplitude of coherence and the population. Our calculations show that a long-lived coherence between chromophore electronic excited states can exist in such a noisy biological environment.

Hilbert and Blaschke phases in the temporal coherence function of stationary broadband light.

PubMed

Fernández-Pousa, Carlos R; Maestre, Haroldo; Torregrosa, Adrián J; Capmany, Juan

2008-10-27

We show that the minimal phase of the temporal coherence function gamma (tau) of stationary light having a partially-coherent symmetric spectral peak can be computed as a relative logarithmic Hilbert transform of its amplitude with respect to its asymptotic behavior. The procedure is applied to experimental data from amplified spontaneous emission broadband sources in the 1.55 microm band with subpicosecond coherence times, providing examples of degrees of coherence with both minimal and non-minimal phase. In the latter case, the Blaschke phase is retrieved and the position of the Blaschke zeros determined.

Coherent storage of temporally multimode light using a spin-wave atomic frequency comb memory

NASA Astrophysics Data System (ADS)

Gündoǧan, M.; Mazzera, M.; Ledingham, P. M.; Cristiani, M.; de Riedmatten, H.

2013-04-01

We report on the coherent and multi-temporal mode storage of light using the full atomic frequency comb memory scheme. The scheme involves the transfer of optical atomic excitations in Pr3+:Y2SiO5 to spin waves in hyperfine levels using strong single-frequency transfer pulses. Using this scheme, a total of five temporal modes are stored and recalled on-demand from the memory. The coherence of the storage and retrieval is characterized using a time-bin interference measurement resulting in visibilities higher than 80%, independent of the storage time. This coherent and multimode spin-wave memory is promising as a quantum memory for light.

Coherence transfer of subhertz-linewidth laser light via an 82-km fiber link

NASA Astrophysics Data System (ADS)

Ma, Chaoqun; Wu, Lifei; Jiang, Yanyi; Yu, Hongfu; Bi, Zhiyi; Ma, Longsheng

2015-12-01

We demonstrate optical coherence transfer of subhertz-linewidth laser light through fiber links by actively compensating random fiber phase noise induced by environmental perturbations. The relative linewidth of laser light after transferring through a 32-km urban fiber link is suppressed within 1 mHz (resolution bandwidth limited), and the absolute linewidth of the transferred laser light is less than 0.36 Hz. For an 82-km fiber link, a repeater station is constructed between a 32-km urban fiber and a 50-km spooled fiber to recover the spectral purity. A relative linewidth of 1 mHz is also demonstrated for light transferring through the 82-km cascaded fiber. Such an optical signal distribution network based on repeater stations allows optical coherence and synchronization available over spatially separated places.

Liquid Argon Scintillation Detection Utilizing Wavelength-Shifting Plates and Light Guides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howard, B.

In DUNE, the event timing provided by the detection of the relatively prompt scintillation photons will improve spatial resolution in the drift direction of the time-projection chamber (TPC) and is especially useful for non-beam physics topics such as supernova neutrinos and nucleon decay. The baseline design for the first 10kt single phase TPC fits the photon detector system in the natural gap between the wire planes of adjacent TPC volumes. A prototype photon detector design utilizes wavelength-shifter coated plates to convert the vacuum ultraviolet scintillation light to the optical and commercially-produced wavelength-shifting light guides to trap some of this lightmore » and transport it to an array of silicon photomultipliers at the end. This system and the testing performed to characterize the system and determine the efficiency are discussed.« less

Reduction of parasitic interferences in digital holographic microscopy by numerically decreased coherence length

NASA Astrophysics Data System (ADS)

Kosmeier, S.; Langehanenberg, P.; von Bally, G.; Kemper, B.

2012-01-01

Due to the large coherence length of laser light, optical path length (OPL) resolution in laser based digital holographic microscopy suffers from parasitic interferences caused by multiple reflections within the experimental setup. Use of partially coherent light reduces this drawback but requires precise and stable matching of object and reference arm's OPLs and limits the spatial frequency of the interference pattern in off-axis holography. Here, we investigate if the noise properties of spectrally broadened light sources can be generated numerically. Therefore, holograms are coherently captured at different laser wavelengths and the corresponding reconstructed wave fields are numerically superimposed utilizing variable weightings. Gaussian and rectangular spectral shapes of the so synthesized field are analyzed with respect to the resulting noise level, which is quantified in OPL distributions of a reflective test target. Utilizing a Gaussian weighting, the noise level is found to be similar to the one obtained with the partially coherent light of a superluminescent diode. With a rectangular shaped synthesized spectrum, noise is reduced more efficient than with a Gaussian one. The applicability of the method in label-free cell analysis is demonstrated by quantitative phase contrast images obtained from living cancer cells.

Role of coherence in microsphere-assisted nanoscopy

NASA Astrophysics Data System (ADS)

Perrin, Stephane; Lecler, Sylvain; Leong-Hoi, Audrey; Montgomery, Paul C.

2017-06-01

The loss of the information, due to the diffraction and the evanescent waves, limits the resolving power of classical optical microscopy. In air, the lateral resolution of an optical microscope can approximated at half of the wavelength using a low-coherence illumination. Recently, several methods have been developed in order to overcome this limitation and, in 2011, a new far-field and full-field imaging technique was proposed where a sub-diffraction-limit resolution has been achieved using a transparent microsphere. In this article, the phenomenon of super-resolution using microsphere-assisted microscopy is analysed through rigorous electro-magnetic simulations. The performances of the imaging technique are estimated as function of optical and geometrical parameters. Furthermore, the role of coherence is introduced through the temporal coherence of the light source and the phase response of the object.

Coherent frequency bridge between visible and telecommunications band for vortex light.

PubMed

Liu, Shi-Long; Liu, Shi-Kai; Li, Yin-Hai; Shi, Shuai; Zhou, Zhi-Yuan; Shi, Bao-Sen

2017-10-02

In quantum communications, vortex photons can encode higher-dimensional quantum states and build high-dimensional communication networks (HDCNs). The interfaces that connect different wavelengths are significant in HDCNs. We construct a coherent orbital angular momentum (OAM) frequency bridge via difference frequency conversion in a nonlinear bulk crystal for HDCNs. Using a single resonant cavity, maximum quantum conversion efficiencies from visible to infrared are 36%, 15%, and 7.8% for topological charges of 0,1, and 2, respectively. The average fidelity obtained using quantum state tomography for the down-converted infrared OAM-state of topological charge 1 is 96.51%. We also prove that the OAM is conserved in this process by measuring visible and infrared interference patterns. This coherent OAM frequency-down conversion bridge represents a basis for an interface between two high-dimensional quantum systems operating with different spectra.

Coherent virtual absorption for discretized light

NASA Astrophysics Data System (ADS)

Longhi, S.

2018-05-01

Coherent virtual absorption (CVA) is a recently-introduced phenomenon for which exponentially growing waves incident onto a conservative optical medium are neither reflected nor transmitted, at least transiently. CVA has been associated to complex zeros of the scattering matrix and can be regarded as the time reversal of the decay process of a quasi-mode sustained by the optical medium. Here we consider CVA for discretized light transport in coupled resonator optical waveguides or waveguide arrays and show that a distinct kind of CVA, which is not related to complex zero excitation of quasi-modes, can be observed. This result suggests that scattering matrix analysis can not fully capture CVA phenomena.

Dependence on fiber Fabry-Pérot tunable filter characteristics in an all-fiber swept-wavelength laser for use in an optical coherence tomography system

NASA Astrophysics Data System (ADS)

Stay, Justin L.; Carr, Dustin; Ferguson, Steve; Haber, Todd; Jenkins, Robert; Mock, Joel

2017-02-01

Optical coherence tomography (OCT) has become a useful and common diagnostic tool within the field of ophthalmology. Although presently a commercial technology, research continues in improving image quality and applying the imaging method to other tissue types. Swept-wavelength lasers based upon fiber ring cavities containing fiber Fabry-Ṕerot tunable filters (FFP-TF), as an intracavity element, provide swept-source optical coherence tomography (SS-OCT) systems with a robust and scalable platform. The FFP-TF can be fabricated within a large range of operating wavelengths, free spectral ranges (FSR), and finesses. To date, FFP-TFs have been fabricated at operating wavelengths from 400 nm to 2.2 µm, FSRs as large as 45 THz, and finesses as high as 30 000. The results in this paper focus on presenting the capability of the FFP-TF as an intracavity element in producing swept-wavelength lasers sources and quantifying the trade off between coherence length and sweep range. We present results within a range of feasible operating conditions. Particular focus is given to the discovery of laser configurations that result in maximization of sweep range and/or power. A novel approach to the electronic drive of the PZT-based FFP-TF is also presented, which eliminates the need for the existence of a mechanical resonance of the optical device. This approach substantially increases the range of drive frequencies with which the filter can be driven and has a positive impact for both the short all-fiber laser cavity (presented in this paper) and long cavity FDML designs as well.

Acute exposure to blue wavelength light during memory consolidation improves verbal memory performance.

PubMed

Alkozei, Anna; Smith, Ryan; Dailey, Natalie S; Bajaj, Sahil; Killgore, William D S

2017-01-01

Acute exposure to light within the blue wavelengths has been shown to enhance alertness and vigilance, and lead to improved speed on reaction time tasks, possibly due to activation of the noradrenergic system. It remains unclear, however, whether the effects of blue light extend beyond simple alertness processes to also enhance other aspects of cognition, such as memory performance. The aim of this study was to investigate the effects of a thirty minute pulse of blue light versus placebo (amber light) exposure in healthy normally rested individuals in the morning during verbal memory consolidation (i.e., 1.5 hours after memory acquisition) using an abbreviated version of the California Verbal Learning Test (CVLT-II). At delayed recall, individuals who received blue light (n = 12) during the consolidation period showed significantly better long-delay verbal recall than individuals who received amber light exposure (n = 18), while controlling for the effects of general intelligence, depressive symptoms and habitual wake time. These findings extend previous work demonstrating the effect of blue light on brain activation and alertness to further demonstrate its effectiveness at facilitating better memory consolidation and subsequent retention of verbal material. Although preliminary, these findings point to a potential application of blue wavelength light to optimize memory performance in healthy populations. It remains to be determined whether blue light exposure may also enhance performance in clinical populations with memory deficits.

Quantum communication with coherent states of light

NASA Astrophysics Data System (ADS)

Khan, Imran; Elser, Dominique; Dirmeier, Thomas; Marquardt, Christoph; Leuchs, Gerd

2017-06-01

Quantum communication offers long-term security especially, but not only, relevant to government and industrial users. It is worth noting that, for the first time in the history of cryptographic encoding, we are currently in the situation that secure communication can be based on the fundamental laws of physics (information theoretical security) rather than on algorithmic security relying on the complexity of algorithms, which is periodically endangered as standard computer technology advances. On a fundamental level, the security of quantum key distribution (QKD) relies on the non-orthogonality of the quantum states used. So even coherent states are well suited for this task, the quantum states that largely describe the light generated by laser systems. Depending on whether one uses detectors resolving single or multiple photon states or detectors measuring the field quadratures, one speaks of, respectively, a discrete- or a continuous-variable description. Continuous-variable QKD with coherent states uses a technology that is very similar to the one employed in classical coherent communication systems, the backbone of today's Internet connections. Here, we review recent developments in this field in two connected regimes: (i) improving QKD equipment by implementing front-end telecom devices and (ii) research into satellite QKD for bridging long distances by building upon existing optical satellite links. This article is part of the themed issue 'Quantum technology for the 21st century'.

Quantum communication with coherent states of light.

PubMed

Khan, Imran; Elser, Dominique; Dirmeier, Thomas; Marquardt, Christoph; Leuchs, Gerd

2017-08-06

Quantum communication offers long-term security especially, but not only, relevant to government and industrial users. It is worth noting that, for the first time in the history of cryptographic encoding, we are currently in the situation that secure communication can be based on the fundamental laws of physics (information theoretical security) rather than on algorithmic security relying on the complexity of algorithms, which is periodically endangered as standard computer technology advances. On a fundamental level, the security of quantum key distribution (QKD) relies on the non-orthogonality of the quantum states used. So even coherent states are well suited for this task, the quantum states that largely describe the light generated by laser systems. Depending on whether one uses detectors resolving single or multiple photon states or detectors measuring the field quadratures, one speaks of, respectively, a discrete- or a continuous-variable description. Continuous-variable QKD with coherent states uses a technology that is very similar to the one employed in classical coherent communication systems, the backbone of today's Internet connections. Here, we review recent developments in this field in two connected regimes: (i) improving QKD equipment by implementing front-end telecom devices and (ii) research into satellite QKD for bridging long distances by building upon existing optical satellite links.This article is part of the themed issue 'Quantum technology for the 21st century'. © 2017 The Author(s).

Effect of light wavelength on hot spring microbial mat biodiversity

PubMed Central

Nishida, Akifumi; Thiel, Vera; Nakagawa, Mayuko; Ayukawa, Shotaro

2018-01-01

Hot spring associated phototrophic microbial mats are purely microbial communities, in which phototrophic bacteria function as primary producers and thus shape the community. The microbial mats at Nakabusa hot springs in Japan harbor diverse photosynthetic bacteria, mainly Thermosynechococcus, Chloroflexus, and Roseiflexus, which use light of different wavelength for energy conversion. The aim of this study was to investigate the effect of the phototrophs on biodiversity and community composition in hot spring microbial mats. For this, we specifically activated the different phototrophs by irradiating the mats with different wavelengths in situ. We used 625, 730, and 890 nm wavelength LEDs alone or in combination and confirmed the hypothesized increase in relative abundance of different phototrophs by 16S rRNA gene sequencing. In addition to the increase of the targeted phototrophs, we studied the effect of the different treatments on chemotrophic members. The specific activation of Thermosynechococcus led to increased abundance of several other bacteria, whereas wavelengths specific to Chloroflexus and Roseiflexus induced a decrease in >50% of the community members as compared to the dark conditions. This suggests that the growth of Thermosynechococcus at the surface layer benefits many community members, whereas less benefit is obtained from an increase in filamentous anoxygenic phototrophs Chloroflexus and Roseiflexus. The increases in relative abundance of chemotrophs under different light conditions suggest a relationship between the two groups. Aerobic chemoheterotrophs such as Thermus sp. and Meiothermus sp. are thought to benefit from aerobic conditions and organic carbon in the form of photosynthates by Thermosynechococcus, while the oxidation of sulfide and production of elemental sulfur by filamentous anoxygenic phototrophs benefit the sulfur-disproportionating Caldimicrobium thiodismutans. In this study, we used an experimental approach under controlled

Effect of light wavelength on hot spring microbial mat biodiversity.

PubMed

Nishida, Akifumi; Thiel, Vera; Nakagawa, Mayuko; Ayukawa, Shotaro; Yamamura, Masayuki

2018-01-01

Hot spring associated phototrophic microbial mats are purely microbial communities, in which phototrophic bacteria function as primary producers and thus shape the community. The microbial mats at Nakabusa hot springs in Japan harbor diverse photosynthetic bacteria, mainly Thermosynechococcus, Chloroflexus, and Roseiflexus, which use light of different wavelength for energy conversion. The aim of this study was to investigate the effect of the phototrophs on biodiversity and community composition in hot spring microbial mats. For this, we specifically activated the different phototrophs by irradiating the mats with different wavelengths in situ. We used 625, 730, and 890 nm wavelength LEDs alone or in combination and confirmed the hypothesized increase in relative abundance of different phototrophs by 16S rRNA gene sequencing. In addition to the increase of the targeted phototrophs, we studied the effect of the different treatments on chemotrophic members. The specific activation of Thermosynechococcus led to increased abundance of several other bacteria, whereas wavelengths specific to Chloroflexus and Roseiflexus induced a decrease in >50% of the community members as compared to the dark conditions. This suggests that the growth of Thermosynechococcus at the surface layer benefits many community members, whereas less benefit is obtained from an increase in filamentous anoxygenic phototrophs Chloroflexus and Roseiflexus. The increases in relative abundance of chemotrophs under different light conditions suggest a relationship between the two groups. Aerobic chemoheterotrophs such as Thermus sp. and Meiothermus sp. are thought to benefit from aerobic conditions and organic carbon in the form of photosynthates by Thermosynechococcus, while the oxidation of sulfide and production of elemental sulfur by filamentous anoxygenic phototrophs benefit the sulfur-disproportionating Caldimicrobium thiodismutans. In this study, we used an experimental approach under controlled

An aluminium nitride light-emitting diode with a wavelength of 210 nanometres.

PubMed

Taniyasu, Yoshitaka; Kasu, Makoto; Makimoto, Toshiki

2006-05-18

Compact high-efficiency ultraviolet solid-state light sources--such as light-emitting diodes (LEDs) and laser diodes--are of considerable technological interest as alternatives to large, toxic, low-efficiency gas lasers and mercury lamps. Microelectronic fabrication technologies and the environmental sciences both require light sources with shorter emission wavelengths: the former for improved resolution in photolithography and the latter for sensors that can detect minute hazardous particles. In addition, ultraviolet solid-state light sources are also attracting attention for potential applications in high-density optical data storage, biomedical research, water and air purification, and sterilization. Wide-bandgap materials, such as diamond and III-V nitride semiconductors (GaN, AlGaN and AlN; refs 3-10), are potential materials for ultraviolet LEDs and laser diodes, but suffer from difficulties in controlling electrical conduction. Here we report the successful control of both n-type and p-type doping in aluminium nitride (AlN), which has a very wide direct bandgap of 6 eV. This doping strategy allows us to develop an AlN PIN (p-type/intrinsic/n-type) homojunction LED with an emission wavelength of 210 nm, which is the shortest reported to date for any kind of LED. The emission is attributed to an exciton transition, and represents an important step towards achieving exciton-related light-emitting devices as well as replacing gas light sources with solid-state light sources.

Coherent diffraction of single Rice Dwarf virus particles using hard X-rays at the Linac Coherent Light Source.

PubMed

Munke, Anna; Andreasson, Jakob; Aquila, Andrew; Awel, Salah; Ayyer, Kartik; Barty, Anton; Bean, Richard J; Berntsen, Peter; Bielecki, Johan; Boutet, Sébastien; Bucher, Maximilian; Chapman, Henry N; Daurer, Benedikt J; DeMirci, Hasan; Elser, Veit; Fromme, Petra; Hajdu, Janos; Hantke, Max F; Higashiura, Akifumi; Hogue, Brenda G; Hosseinizadeh, Ahmad; Kim, Yoonhee; Kirian, Richard A; Reddy, Hemanth K N; Lan, Ti-Yen; Larsson, Daniel S D; Liu, Haiguang; Loh, N Duane; Maia, Filipe R N C; Mancuso, Adrian P; Mühlig, Kerstin; Nakagawa, Atsushi; Nam, Daewoong; Nelson, Garrett; Nettelblad, Carl; Okamoto, Kenta; Ourmazd, Abbas; Rose, Max; van der Schot, Gijs; Schwander, Peter; Seibert, M Marvin; Sellberg, Jonas A; Sierra, Raymond G; Song, Changyong; Svenda, Martin; Timneanu, Nicusor; Vartanyants, Ivan A; Westphal, Daniel; Wiedorn, Max O; Williams, Garth J; Xavier, Paulraj Lourdu; Yoon, Chun Hong; Zook, James

2016-08-01

Single particle diffractive imaging data from Rice Dwarf Virus (RDV) were recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS). RDV was chosen as it is a well-characterized model system, useful for proof-of-principle experiments, system optimization and algorithm development. RDV, an icosahedral virus of about 70 nm in diameter, was aerosolized and injected into the approximately 0.1 μm diameter focused hard X-ray beam at the CXI instrument of LCLS. Diffraction patterns from RDV with signal to 5.9 Ångström were recorded. The diffraction data are available through the Coherent X-ray Imaging Data Bank (CXIDB) as a resource for algorithm development, the contents of which are described here.

Wavelength-Filter Based Spectral Calibrated Wave number - Linearization in 1.3 mm Spectral Domain Optical Coherence.

PubMed

Wijeisnghe, Ruchire Eranga Henry; Cho, Nam Hyun; Park, Kibeom; Shin, Yongseung; Kim, Jeehyun

2013-12-01

In this study, we demonstrate the enhanced spectral calibration method for 1.3 μm spectral-domain optical coherence tomography (SD-OCT). The calibration method using wavelength-filter simplifies the SD-OCT system, and also the axial resolution and the entire speed of the OCT system can be dramatically improved as well. An externally connected wavelength-filter is utilized to obtain the information of the wavenumber and the pixel position. During the calibration process the wavelength-filter is placed after a broadband source by connecting through an optical circulator. The filtered spectrum with a narrow line width of 0.5 nm is detected by using a line-scan camera. The method does not require a filter or a software recalibration algorithm for imaging as it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. One of the main drawbacks of SD-OCT is the broadened point spread functions (PSFs) with increasing imaging depth can be compensated by increasing the wavenumber-linearization order. The sensitivity of our system was measured at 99.8 dB at an imaging depth of 2.1 mm compared with the uncompensated case.

Multi-wavelength analysis of Ellerman Bomb Light Curves

NASA Astrophysics Data System (ADS)

Herlender, M.; Berlicki, A.

We present the results of a multi-wavelength photometric analysis of Ellerman Bomb (EB) observations obtained from the Dutch Open Telescope. In our data we have found 6 EBs located in the super-penumbra of the main spot in the active region NOAA 10781. We present light curves of EB observed in the Hα line centre and wing +0.7 Å, in the Ca II H line centre and wing~+2.35 Å, in the G-band and in the TRACE 1600 Å filter. We have shown that EBs were visible in the G-band and moreover, there was a good correlation between the light curves in the G-band and in the Hα line wings. We also found quasi-periodic oscillations of EBs brightness in the G-band, CaII H line and TRACE 1600 Å filter.

All-silicon-based nano-antennas for wavelength and polarization demultiplexing.

PubMed

Panmai, Mingcheng; Xiang, Jin; Sun, Zhibo; Peng, Yuanyuan; Liu, Hongfeng; Liu, Haiying; Dai, Qiaofeng; Tie, Shaolong; Lan, Sheng

2018-05-14

We propose an all-silicon-based nano-antenna that functions as not only a wavelength demultiplexer but also a polarization one. The nano-antenna is composed of two silicon cuboids with the same length and height but with different widths. The asymmetric structure of the nano-antenna with respect to the electric field of the incident light induced an electric dipole component in the propagation direction of the incident light. The interference between this electric dipole and the magnetic dipole induced by the magnetic field parallel to the long side of the cuboids is exploited to manipulate the radiation direction of the nano-antenna. The radiation direction of the nano-antenna at a certain wavelength depends strongly on the phase difference between the electric and magnetic dipoles interacting coherently, offering us the opportunity to realize wavelength demultiplexing. By varying the polarization of the incident light, the interference of the magnetic dipole induced by the asymmetry of the nano-antenna and the electric dipole induced by the electric field parallel to the long side of the cuboids can also be used to realize polarization demultiplexing in a certain wavelength range. More interestingly, the interference between the dipole and quadrupole modes of the nano-antenna can be utilized to shape the radiation directivity of the nano-antenna. We demonstrate numerically that radiation with adjustable direction and high directivity can be realized in such a nano-antenna which is compatible with the current fabrication technology of silicon chips.

Measuring of nonlinear properties of spatial light modulator with different wavelengths

NASA Astrophysics Data System (ADS)

Khalid, Farah G.; Younis Al-Dabagh, Samar; Ahmed, Sudad S.; Mahmood, Aseel I.; Al-Naimee, Kais

2018-05-01

The non-linear optical properties of Spatial Light Modulator(SLM) represented by Nonlinear Refractive Index (NLR) and nonlinear Absorption coefficient has been measured in this work using highly sensitive method known as Z-scan technique for different wavelengths (red and green). The capability to do instant measurements of different nonlinear optical parameters lead to consider these techniques as a one of the most desired and effective methods that could apply for different materials. The results showed that the NLR were in the same power for the different wavelengths while the nonlinear absorption is higher in case of green laser.

Effect of light wavelength on motility and magnetic sensibility of the magnetotactic multicellular prokaryote 'Candidatus Magnetoglobus multicellularis'.

PubMed

de Azevedo, Lyvia Vidinho; de Barros, Henrique Lins; Keim, Carolina Neumann; Acosta-Avalos, Daniel

2013-09-01

'Candidatus Magnetoglobus multicellularis' is a magnetotactic microorganism composed of several bacterial cells. Presently, it is the best known multicellular magnetotactic prokaryote (MMP). Recently, it has been observed that MMPs present a negative photoresponse to high intensity ultraviolet and violet-blue light. In this work, we studied the movement of 'Candidatus Magnetoglobus multicellularis' under low intensity light of different wavelengths, measuring the average velocity and the time to reorient its trajectory when the external magnetic field changes its direction (U-turn time). Our results show that the mean average velocity is higher for red light (628 nm) and lower for green light (517 nm) as compared to yellow (596 nm) and blue (469 nm) light, and the U-turn time decreased for green light illumination. The light wavelength velocity dependence can be understood as variation in flagella rotation speed, being increased by the red light and decreased by the green light relative to yellow and blue light. It is suggested that the dependence of the U-turn time on light wavelength can be considered a form of light-dependent magnetotaxis, because this time represents the magnetic sensibility of the magnetotactic microorganisms. The cellular and molecular mechanisms for this light-dependent velocity and magnetotaxis are unknown and deserve further studies to understand the biochemical interactions and the ecological roles of the different mechanisms of taxis in MMPs.

Coherent diffraction of single Rice Dwarf virus particles using hard X-rays at the Linac Coherent Light Source

PubMed Central

Munke, Anna; Andreasson, Jakob; Aquila, Andrew; Awel, Salah; Ayyer, Kartik; Barty, Anton; Bean, Richard J.; Berntsen, Peter; Bielecki, Johan; Boutet, Sébastien; Bucher, Maximilian; Chapman, Henry N.; Daurer, Benedikt J.; DeMirci, Hasan; Elser, Veit; Fromme, Petra; Hajdu, Janos; Hantke, Max F.; Higashiura, Akifumi; Hogue, Brenda G.; Hosseinizadeh, Ahmad; Kim, Yoonhee; Kirian, Richard A.; Reddy, Hemanth K.N.; Lan, Ti-Yen; Larsson, Daniel S.D.; Liu, Haiguang; Loh, N. Duane; Maia, Filipe R.N.C.; Mancuso, Adrian P.; Mühlig, Kerstin; Nakagawa, Atsushi; Nam, Daewoong; Nelson, Garrett; Nettelblad, Carl; Okamoto, Kenta; Ourmazd, Abbas; Rose, Max; van der Schot, Gijs; Schwander, Peter; Seibert, M. Marvin; Sellberg, Jonas A.; Sierra, Raymond G.; Song, Changyong; Svenda, Martin; Timneanu, Nicusor; Vartanyants, Ivan A.; Westphal, Daniel; Wiedorn, Max O.; Williams, Garth J.; Xavier, Paulraj Lourdu; Yoon, Chun Hong; Zook, James

2016-01-01

Single particle diffractive imaging data from Rice Dwarf Virus (RDV) were recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS). RDV was chosen as it is a well-characterized model system, useful for proof-of-principle experiments, system optimization and algorithm development. RDV, an icosahedral virus of about 70 nm in diameter, was aerosolized and injected into the approximately 0.1 μm diameter focused hard X-ray beam at the CXI instrument of LCLS. Diffraction patterns from RDV with signal to 5.9 Ångström were recorded. The diffraction data are available through the Coherent X-ray Imaging Data Bank (CXIDB) as a resource for algorithm development, the contents of which are described here. PMID:27478984

Coherent diffraction of single Rice Dwarf virus particles using hard X-rays at the Linac Coherent Light Source

DOE PAGES

Munke, Anna; Andreasson, Jakob; Aquila, Andrew; ...

2016-08-01

Single particle diffractive imaging data from Rice Dwarf Virus (RDV) were recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS). RDV was chosen as it is a well-characterized model system, useful for proof-of-principle experiments, system optimization and algorithm development. RDV, an icosahedral virus of about 70 nm in diameter, was aerosolized and injected into the approximately 0.1 μm diameter focused hard X-ray beam at the CXI instrument of LCLS. Diffraction patterns from RDV with signal to 5.9 Ångström were recorded. Here, the diffraction data are available through the Coherent X-ray Imaging Data Bank (CXIDB)more » as a resource for algorithm development, the contents of which are described here.« less

Phase response of the Arabidopsis thaliana circadian clock to light pulses of different wavelengths.

PubMed

Ohara, Takayuki; Fukuda, Hirokazu; Tokuda, Isao T

2015-04-01

Light is known as one of the most powerful environmental time cues for the circadian system. The quality of light is characterized by its intensity and wavelength. We examined how the phase response of Arabidopsis thaliana depends on the wavelength of the stimulus light and the type of light perturbation. Using transgenic A. thaliana expressing a luciferase gene, we monitored the rhythm of the bioluminescence signal. We stimulated the plants under constant red light using 3 light perturbation treatments: (1) increasing the red light intensity, (2) turning on a blue light while turning off the red light, and (3) turning on a blue light while keeping the red light on. To examine the phase response properties, we generated a phase transition curve (PTC), which plots the phase after the perturbation as a function of the phase before the perturbation. To evaluate the effect of the 3 light perturbation treatments, we simulated PTCs using a mathematical model of the plant circadian clock and fitted the simulated PTCs to the experimentally measured PTCs. Among the 3 treatments, perturbation (3) provided the strongest stimulus. The results indicate that the color of the stimulus light and the type of pulse administration affect the phase response in a complex manner. Moreover, the results suggest the involvement of interaction between red and blue light signaling pathways in resetting of the plant circadian clock. © 2015 The Author(s).

Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy

PubMed Central

Yi, Ji; Chen, Siyu; Shu, Xiao; Fawzi, Amani A.; Zhang, Hao F.

2015-01-01

We achieved human retinal imaging using visible-light optical coherence tomography (vis-OCT) guided by an integrated scanning laser ophthalmoscopy (SLO). We adapted a spectral domain OCT configuration and used a supercontinuum laser as the illumating source. The center wavelength was 564 nm and the bandwidth was 115 nm, which provided a 0.97 µm axial resolution measured in air. We characterized the sensitivity to be 86 dB with 226 µW incidence power on the pupil. We also integrated an SLO that shared the same optical path of the vis-OCT sample arm for alignment purposes. We demonstrated the retinal imaging from both systems centered at the fovea and optic nerve head with 20° × 20° and 10° × 10° field of view. We observed similar anatomical structures in vis-OCT and NIR-OCT. The contrast appeared different from vis-OCT to NIR-OCT, including slightly weaker signal from intra-retinal layers, and increased visibility and contrast of anatomical layers in the outer retina. PMID:26504622

Long range coherence in free electron lasers

NASA Technical Reports Server (NTRS)

Colson, W. B.

1984-01-01

The simple free electron laser (FEL) design uses a static, periodic, transverse magnetic field to undulate relativistic electrons traveling along its axis. This allows coupling to a co-propagating optical wave and results in bunching to produce coherent radiation. The advantages of the FEL are continuous tunability, operation at wavelengths ranging from centimeters to angstroms, and high efficiency resulting from the fact that the interaction region only contains light, relativistic electrons, and a magnetic field. Theoretical concepts and operational principles are discussed.

Growth and development of Arabidopsis thaliana under single-wavelength red and blue laser light.

PubMed

Ooi, Amanda; Wong, Aloysius; Ng, Tien Khee; Marondedze, Claudius; Gehring, Christoph; Ooi, Boon S

2016-09-23

Indoor horticulture offers a sensible solution for sustainable food production and is becoming increasingly widespread. However, it incurs high energy and cost due to the use of artificial lighting such as high-pressure sodium lamps, fluorescent light or increasingly, the light-emitting diodes (LEDs). The energy efficiency and light quality of currently available horticultural lighting is suboptimal, and therefore less than ideal for sustainable and cost-effective large-scale plant production. Here, we demonstrate the use of high-powered single-wavelength lasers for indoor horticulture. They are highly energy-efficient and can be remotely guided to the site of plant growth, thus reducing on-site heat accumulation. Furthermore, laser beams can be tailored to match the absorption profiles of different plant species. We have developed a prototype laser growth chamber and demonstrate that plants grown under laser illumination can complete a full growth cycle from seed to seed with phenotypes resembling those of plants grown under LEDs reported previously. Importantly, the plants have lower expression of proteins diagnostic for light and radiation stress. The phenotypical, biochemical and proteome data show that the single-wavelength laser light is suitable for plant growth and therefore, potentially able to unlock the advantages of this next generation lighting technology for highly energy-efficient horticulture.

Growth and development of Arabidopsis thaliana under single-wavelength red and blue laser light

PubMed Central

Ooi, Amanda; Wong, Aloysius; Ng, Tien Khee; Marondedze, Claudius; Gehring, Christoph; Ooi, Boon S.

2016-01-01

Indoor horticulture offers a sensible solution for sustainable food production and is becoming increasingly widespread. However, it incurs high energy and cost due to the use of artificial lighting such as high-pressure sodium lamps, fluorescent light or increasingly, the light-emitting diodes (LEDs). The energy efficiency and light quality of currently available horticultural lighting is suboptimal, and therefore less than ideal for sustainable and cost-effective large-scale plant production. Here, we demonstrate the use of high-powered single-wavelength lasers for indoor horticulture. They are highly energy-efficient and can be remotely guided to the site of plant growth, thus reducing on-site heat accumulation. Furthermore, laser beams can be tailored to match the absorption profiles of different plant species. We have developed a prototype laser growth chamber and demonstrate that plants grown under laser illumination can complete a full growth cycle from seed to seed with phenotypes resembling those of plants grown under LEDs reported previously. Importantly, the plants have lower expression of proteins diagnostic for light and radiation stress. The phenotypical, biochemical and proteome data show that the single-wavelength laser light is suitable for plant growth and therefore, potentially able to unlock the advantages of this next generation lighting technology for highly energy-efficient horticulture. PMID:27659906

Quantum coherence spectroscopy reveals complex dynamics in bacterial light-harvesting complex 2 (LH2).

PubMed

Harel, Elad; Engel, Gregory S

2012-01-17

Light-harvesting antenna complexes transfer energy from sunlight to photosynthetic reaction centers where charge separation drives cellular metabolism. The process through which pigments transfer excitation energy involves a complex choreography of coherent and incoherent processes mediated by the surrounding protein and solvent environment. The recent discovery of coherent dynamics in photosynthetic light-harvesting antennae has motivated many theoretical models exploring effects of interference in energy transfer phenomena. In this work, we provide experimental evidence of long-lived quantum coherence between the spectrally separated B800 and B850 rings of the light-harvesting complex 2 (LH2) of purple bacteria. Spectrally resolved maps of the detuning, dephasing, and the amplitude of electronic coupling between excitons reveal that different relaxation pathways act in concert for optimal transfer efficiency. Furthermore, maps of the phase of the signal suggest that quantum mechanical interference between different energy transfer pathways may be important even at ambient temperature. Such interference at a product state has already been shown to enhance the quantum efficiency of transfer in theoretical models of closed loop systems such as LH2.

Quantum coherence spectroscopy reveals complex dynamics in bacterial light-harvesting complex 2 (LH2)

PubMed Central

Harel, Elad; Engel, Gregory S.

2012-01-01

Light-harvesting antenna complexes transfer energy from sunlight to photosynthetic reaction centers where charge separation drives cellular metabolism. The process through which pigments transfer excitation energy involves a complex choreography of coherent and incoherent processes mediated by the surrounding protein and solvent environment. The recent discovery of coherent dynamics in photosynthetic light-harvesting antennae has motivated many theoretical models exploring effects of interference in energy transfer phenomena. In this work, we provide experimental evidence of long-lived quantum coherence between the spectrally separated B800 and B850 rings of the light-harvesting complex 2 (LH2) of purple bacteria. Spectrally resolved maps of the detuning, dephasing, and the amplitude of electronic coupling between excitons reveal that different relaxation pathways act in concert for optimal transfer efficiency. Furthermore, maps of the phase of the signal suggest that quantum mechanical interference between different energy transfer pathways may be important even at ambient temperature. Such interference at a product state has already been shown to enhance the quantum efficiency of transfer in theoretical models of closed loop systems such as LH2. PMID:22215585

Timescales of Coherent Dynamics in the Light Harvesting Complex 2 (LH2) of Rhodobacter sphaeroides.

PubMed

Fidler, Andrew F; Singh, Ved P; Long, Phillip D; Dahlberg, Peter D; Engel, Gregory S

2013-05-02

The initial dynamics of energy transfer in the light harvesting complex 2 from Rhodobacter sphaeroides were investigated with polarization controlled two-dimensional spectroscopy. This method allows only the coherent electronic motions to be observed revealing the timescale of dephasing among the excited states. We observe persistent coherence among all states and assign ensemble dephasing rates for the various coherences. A simple model is utilized to connect the spectroscopic transitions to the molecular structure, allowing us to distinguish coherences between the two rings of chromophores and coherences within the rings. We also compare dephasing rates between excited states to dephasing rates between the ground and excited states, revealing that the coherences between excited states dephase on a slower timescale than coherences between the ground and excited states.

Easier detection of invertebrate "identification-key characters" with light of different wavelengths

PubMed Central

2011-01-01

The marine α-taxonomist often encounters two problems. Firstly, the "environmental dirt" that is frequently present on the specimens and secondly the difficulty in distinguishing key-features due to the uniform colours which fixed animals often adopt. Here we show that illuminating animals with deep-blue or ultraviolet light instead of the normal white-light abrogates both difficulties; dirt disappears and important details become clearly visible. This light regime has also two other advantages. It allows easy detection of very small, normally invisible, animals (0.1 μm range). And as these light wavelengths can induce fluorescence, new identification markers may be discovered by this approach. PMID:22040277

Telescope aperture optimization for spacebased coherent wind lidar

NASA Astrophysics Data System (ADS)

Ge, Xian-ying; Zhu, Jun; Cao, Qipeng; Zhang, Yinchao; Yin, Huan; Dong, Xiaojing; Wang, Chao; Zhang, Yongchao; Zhang, Ning

2015-08-01

Many studies have indicated that the optimum measurement approach for winds from space is a pulsed coherent wind lidar, which is an active remote sensing tool with the characteristics that high spatial and temporal resolutions, real-time detection, high mobility, facilitated control and so on. Because of the significant eye safety, efficiency, size, and lifetime advantage, 2μm wavelength solid-state laser lidar systems have attracted much attention in spacebased wind lidar plans. In this paper, the theory of coherent detection is presented and a 2μm wavelength solid-state laser lidar system is introduced, then the ideal aperture is calculated from signal-to-noise(SNR) view at orbit 400km. However, considering real application, even if the lidar hardware is perfectly aligned, the directional jitter of laser beam, the attitude change of the lidar in the long round trip time of the light from the atmosphere and other factors can bring misalignment angle. So the influence of misalignment angle is considered and calculated, and the optimum telescope diameter(0.45m) is obtained as the misalignment angle is 4 μrad. By the analysis of the optimum aperture required for spacebased coherent wind lidar system, we try to present the design guidance for the telescope.

Probing neutrino coupling to a light scalar with coherent neutrino scattering

NASA Astrophysics Data System (ADS)

Farzan, Yasaman; Lindner, Manfred; Rodejohann, Werner; Xu, Xun-Jie

2018-05-01

Large neutrino event numbers in future experiments measuring coherent elastic neutrino nucleus scattering allow precision measurements of standard and new physics. We analyze the current and prospective limits of a light scalar particle coupling to neutrinos and quarks, using COHERENT and CONUS as examples. Both lepton number conserving and violating interactions are considered. It is shown that current (future) experiments can probe for scalar masses of a few MeV couplings down to the level of 10-4 (10-6). Scalars with masses around the neutrino energy allow to determine their mass via a characteristic spectrum shape distortion. Our present and future limits are compared with constraints from supernova evolution, Big Bang nucleosynthesis and neutrinoless double beta decay. We also outline UV-complete underlying models that include a light scalar with coupling to quarks for both lepton number violating and conserving coupling to neutrinos.

Frequency dependence of coherently amplified two-photon emission from hydrogen molecules

NASA Astrophysics Data System (ADS)

Hara, Hideaki; Miyamoto, Yuki; Hiraki, Takahiro; Masuda, Takahiko; Sasao, Noboru; Uetake, Satoshi; Yoshimi, Akihiro; Yoshimura, Koji; Yoshimura, Motohiko

2017-12-01

We investigate how the efficiency of coherently amplified two-photon emission depends on the frequency of one of the two emitted photons, namely the signal photon. This is done over the wavelength range of 5.048-10.21 μ m by using the vibrational transition of parahydrogen. The efficiency increases with the frequency of the signal photon. Considering experimental errors, our results are consistent with the theoretical prediction for the present experimental conditions. This study is an experimental demonstration of the frequency dependence of coherently amplified two-photon emission, and also presents its potential as a light source.

Short wavelength limits of current shot noise suppression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nause, Ariel, E-mail: arielnau@post.tau.ac.il; Dyunin, Egor; Gover, Avraham

Shot noise in electron beam was assumed to be one of the features beyond control of accelerator physics. Current results attained in experiments at Accelerator Test Facility in Brookhaven and Linac Coherent Light Source in Stanford suggest that the control of the shot noise in electron beam (and therefore of spontaneous radiation and Self Amplified Spontaneous Emission of Free Electron Lasers) is feasible at least in the visible range of the spectrum. Here, we present a general linear formulation for collective micro-dynamics of e-beam noise and its control. Specifically, we compare two schemes for current noise suppression: a quarter plasmamore » wavelength drift section and a combined drift/dispersive (transverse magnetic field) section. We examine and compare their limits of applicability at short wavelengths via considerations of electron phase-spread and the related Landau damping effect.« less

Research on the space-borne coherent wind lidar technique and the prototype experiment

NASA Astrophysics Data System (ADS)

Gao, Long; Tao, Yuliang; An, Chao; Yang, Jukui; Du, Guojun; Zheng, Yongchao

2016-10-01

Space-borne coherent wind lidar technique is considered as one of the most promising and appropriate remote Sensing methods for successfully measuring the whole global vector wind profile between the lower atmosphere and the middle atmosphere. Compared with other traditional methods, the space-borne coherent wind lidar has some advantages, such as, the all-day operation; many lidar systems can be integrated into the same satellite because of the light-weight and the small size, eye-safe wavelength, and being insensitive to the background light. Therefore, this coherent lidar could be widely applied into the earth climate research, disaster monitoring, numerical weather forecast, environment protection. In this paper, the 2μm space-borne coherent wind lidar system for measuring the vector wind profile is proposed. And the technical parameters about the sub-system of the coherent wind lidar are simulated and the all sub-system schemes are proposed. For sake of validating the technical parameters of the space-borne coherent wind lidar system and the optical off-axis telescope, the weak laser signal detection technique, etc. The proto-type coherent wind lidar is produced and the experiments for checking the performance of this proto-type coherent wind lidar are finished with the hard-target and the soft target, and the horizontal wind and the vertical wind profile are measured and calibrated, respectively. For this proto-type coherent wind lidar, the wavelength is 1.54μm, the pulse energy 80μJ, the pulse width 300ns, the diameter of the off-axis telescope 120mm, the single wedge for cone scanning with the 40°angle, and the two dualbalanced InGaAs detector modules are used. The experiment results are well consisted with the simulation process, and these results show that the wind profile between the vertical altitude 4km can be measured, the accuracy of the wind velocity and the wind direction are better than 1m/s and +/-10°, respectively.

Wavelength shifting of intra-cavity photons: Adiabatic wavelength tuning in rapidly wavelength-swept lasers

PubMed Central

Jirauschek, Christian; Huber, Robert

2015-01-01

We analyze the physics behind the newest generation of rapidly wavelength tunable sources for optical coherence tomography (OCT), retaining a single longitudinal cavity mode during operation without repeated build up of lasing. In this context, we theoretically investigate the currently existing concepts of rapidly wavelength-swept lasers based on tuning of the cavity length or refractive index, leading to an altered optical path length inside the resonator. Specifically, we consider vertical-cavity surface-emitting lasers (VCSELs) with microelectromechanical system (MEMS) mirrors as well as Fourier domain mode-locked (FDML) and Vernier-tuned distributed Bragg reflector (VT-DBR) lasers. Based on heuristic arguments and exact analytical solutions of Maxwell’s equations for a fundamental laser resonator model, we show that adiabatic wavelength tuning is achieved, i.e., hopping between cavity modes associated with a repeated build up of lasing is avoided, and the photon number is conserved. As a consequence, no fundamental limit exists for the wavelength tuning speed, in principle enabling wide-range wavelength sweeps at arbitrary tuning speeds with narrow instantaneous linewidth. PMID:26203373

Beyond crystallography: Diffractive imaging using coherent x-ray light sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, J.; Ishikawa, T.; Robinson, I. K.

X-ray crystallography has been central to the development of many fields of science over the past century. It has now matured to a point that as long as good-quality crystals are available, their atomic structure can be routinely determined in three dimensions. However, many samples in physics, chemistry, materials science, nanoscience, geology, and biology are noncrystalline, and thus their three-dimensional structures are not accessible by traditional x-ray crystallography. Overcoming this hurdle has required the development of new coherent imaging methods to harness new coherent x-ray light sources. Here we review the revolutionary advances that are transforming x-ray sources and imagingmore » in the 21st century.« less

A chip-integrated coherent photonic-phononic memory.

PubMed

Merklein, Moritz; Stiller, Birgit; Vu, Khu; Madden, Stephen J; Eggleton, Benjamin J

2017-09-18

Controlling and manipulating quanta of coherent acoustic vibrations-phonons-in integrated circuits has recently drawn a lot of attention, since phonons can function as unique links between radiofrequency and optical signals, allow access to quantum regimes and offer advanced signal processing capabilities. Recent approaches based on optomechanical resonators have achieved impressive quality factors allowing for storage of optical signals. However, so far these techniques have been limited in bandwidth and are incompatible with multi-wavelength operation. In this work, we experimentally demonstrate a coherent buffer in an integrated planar optical waveguide by transferring the optical information coherently to an acoustic hypersound wave. Optical information is extracted using the reverse process. These hypersound phonons have similar wavelengths as the optical photons but travel at five orders of magnitude lower velocity. We demonstrate the storage of phase and amplitude of optical information with gigahertz bandwidth and show operation at separate wavelengths with negligible cross-talk.Optical storage implementations based on optomechanical resonator are limited to one wavelength. Here, exploiting stimulated Brillouin scattering, the authors demonstrate a coherent optical memory based on a planar integrated waveguide, which can operate at different wavelengths without cross-talk.

Manipulation of light wavelength at appropriate growth stage to enhance biomass productivity and fatty acid methyl ester yield using Chlorella vulgaris.

PubMed

Kim, Dae Geun; Lee, Changsu; Park, Seung-Moon; Choi, Yoon-E

2014-05-01

LEDs light offer several advantages over the conventional lamps, thereby being considered as the optimal light sources for microalgal cultivation. In this study, various light-emitting diodes (LEDs) especially red and blue color with different light wavelengths were employed to explore the effects of light source on phototrophic cultivation of Chlorella vulgaris. Blue light illumination led to significantly increased cell size, whereas red light resulted in small-sized cell with active divisions. Based on the discovery of the effect of light wavelengths on microalgal biology, we then applied appropriate wavelength at different growth stages; blue light was illuminated first and then shifted to red light. By doing so, biomass and lipid productivity of C. vulgaris could be significantly increased, compared to that in the control. These results will shed light on a novel approach using LED light for microalgal biotechnology. Copyright © 2014 Elsevier Ltd. All rights reserved.

X-ray detectors at the Linac Coherent Light Source.

PubMed

Blaj, Gabriel; Caragiulo, Pietro; Carini, Gabriella; Carron, Sebastian; Dragone, Angelo; Freytag, Dietrich; Haller, Gunther; Hart, Philip; Hasi, Jasmine; Herbst, Ryan; Herrmann, Sven; Kenney, Chris; Markovic, Bojan; Nishimura, Kurtis; Osier, Shawn; Pines, Jack; Reese, Benjamin; Segal, Julie; Tomada, Astrid; Weaver, Matt

2015-05-01

Free-electron lasers (FELs) present new challenges for camera development compared with conventional light sources. At SLAC a variety of technologies are being used to match the demands of the Linac Coherent Light Source (LCLS) and to support a wide range of scientific applications. In this paper an overview of X-ray detector design requirements at FELs is presented and the various cameras in use at SLAC are described for the benefit of users planning experiments or analysts looking at data. Features and operation of the CSPAD camera, which is currently deployed at LCLS, are discussed, and the ePix family, a new generation of cameras under development at SLAC, is introduced.

X-ray detectors at the Linac Coherent Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blaj, Gabriel; Caragiulo, Pietro; Carini, Gabriella

Free-electron lasers (FELs) present new challenges for camera development compared with conventional light sources. At SLAC a variety of technologies are being used to match the demands of the Linac Coherent Light Source (LCLS) and to support a wide range of scientific applications. In this paper an overview of X-ray detector design requirements at FELs is presented and the various cameras in use at SLAC are described for the benefit of users planning experiments or analysts looking at data. Features and operation of the CSPAD camera, which is currently deployed at LCLS, are discussed, and the ePix family, a newmore » generation of cameras under development at SLAC, is introduced.« less

X-ray detectors at the Linac Coherent Light Source

DOE PAGES

Blaj, Gabriel; Caragiulo, Pietro; Carini, Gabriella; ...

2015-04-21

Free-electron lasers (FELs) present new challenges for camera development compared with conventional light sources. At SLAC a variety of technologies are being used to match the demands of the Linac Coherent Light Source (LCLS) and to support a wide range of scientific applications. In this paper an overview of X-ray detector design requirements at FELs is presented and the various cameras in use at SLAC are described for the benefit of users planning experiments or analysts looking at data. Features and operation of the CSPAD camera, which is currently deployed at LCLS, are discussed, and the ePix family, a newmore » generation of cameras under development at SLAC, is introduced.« less

X-ray detectors at the Linac Coherent Light Source

PubMed Central

Blaj, Gabriel; Caragiulo, Pietro; Carini, Gabriella; Carron, Sebastian; Dragone, Angelo; Freytag, Dietrich; Haller, Gunther; Hart, Philip; Hasi, Jasmine; Herbst, Ryan; Herrmann, Sven; Kenney, Chris; Markovic, Bojan; Nishimura, Kurtis; Osier, Shawn; Pines, Jack; Reese, Benjamin; Segal, Julie; Tomada, Astrid; Weaver, Matt

2015-01-01

Free-electron lasers (FELs) present new challenges for camera development compared with conventional light sources. At SLAC a variety of technologies are being used to match the demands of the Linac Coherent Light Source (LCLS) and to support a wide range of scientific applications. In this paper an overview of X-ray detector design requirements at FELs is presented and the various cameras in use at SLAC are described for the benefit of users planning experiments or analysts looking at data. Features and operation of the CSPAD camera, which is currently deployed at LCLS, are discussed, and the ePix family, a new generation of cameras under development at SLAC, is introduced. PMID:25931071

High-speed OCT light sources and systems [Invited

PubMed Central

Klein, Thomas; Huber, Robert

2017-01-01

Imaging speed is one of the most important parameters that define the performance of optical coherence tomography (OCT) systems. During the last two decades, OCT speed has increased by over three orders of magnitude. New developments in wavelength-swept lasers have repeatedly been crucial for this development. In this review, we discuss the historical evolution and current state of the art of high-speed OCT systems, with focus on wavelength swept light sources and swept source OCT systems. PMID:28270988

Long-wavelength (red) light produces hyperopia in juvenile and adolescent tree shrews.

PubMed

Gawne, Timothy J; Ward, Alexander H; Norton, Thomas T

2017-11-01

In infant tree shrews, exposure to narrow-band long-wavelength (red) light, that stimulates long-wavelength sensitive cones almost exclusively, slows axial elongation and produces hyperopia. We asked if red light produces hyperopia in juvenile and adolescent animals, ages when plus lenses are ineffective. Animals were raised in fluorescent colony lighting (100-300 lux) until they began 13days of red-light treatment at 11 (n=5, "infant"), 35 (n=5, "juvenile") or 95 (n=5, "adolescent") days of visual experience (DVE). LEDs provided 527-749 lux on the cage floor. To control for the higher red illuminance, a fluorescent control group (n=5) of juvenile (35 DVE) animals was exposed to ∼975 lux. Refractions were measured daily; ocular component dimensions at the start and end of treatment and end of recovery in colony lighting. These groups were compared with normals (n=7). In red light, the refractive state of both juvenile and adolescent animals became significantly (P<0.05) hyperopic: juvenile 3.9±1.0 diopters (D, mean±SEM) vs. normal 0.8±0.1D; adolescent 1.6±0.2D vs. normal 0.4±0.1D. The fluorescent control group refractions (0.6±0.3D) were normal. In red-treated juveniles the vitreous chamber was significantly smaller than normal (P<0.05): juvenile 2.67±0.03mmvs. normal 2.75±0.02mm. The choroid was also significantly thicker: juvenile 77±4μmvs. normal 57±3μm (P<0.05). Although plus lenses do not restrain eye growth in juvenile tree shrews, the red light-induced slowed growth and hyperopia in juvenile and adolescent tree shrews demonstrates that the emmetropization mechanism is still capable of restraining eye growth at these ages. Copyright © 2017 Elsevier Ltd. All rights reserved.

Beyond crystallography: diffractive imaging using coherent x-ray light sources.

PubMed

Miao, Jianwei; Ishikawa, Tetsuya; Robinson, Ian K; Murnane, Margaret M

2015-05-01

X-ray crystallography has been central to the development of many fields of science over the past century. It has now matured to a point that as long as good-quality crystals are available, their atomic structure can be routinely determined in three dimensions. However, many samples in physics, chemistry, materials science, nanoscience, geology, and biology are noncrystalline, and thus their three-dimensional structures are not accessible by traditional x-ray crystallography. Overcoming this hurdle has required the development of new coherent imaging methods to harness new coherent x-ray light sources. Here we review the revolutionary advances that are transforming x-ray sources and imaging in the 21st century. Copyright © 2015, American Association for the Advancement of Science.

Purifying synthetic high-strength wastewater by microalgae chlorella vulgaris under various light emitting diode wavelengths and intensities

PubMed Central

2013-01-01

The high-strength wastewater is now well known as a threat to the natural water since it is highly possible to arouse water eutrophication or algal blooms. The effects of various light emitting diode wavelengths and intensities on the microalgae biological wastewater treatment system was studied in this research. The various nutrient removals and economic efficiencies represented similar variation trends, and these variations under both high C and N loading treatments were similar too. The order for microalgae C. vulgaris reproduction in terms of dry weight and nutrient removal efficiency both were red > white > yellow > blue, under high carbon and nitrogen loading treatments, indicating that the red light was the optimum light wavelength. Furthermore, considering the optimal light intensity in terms of nutrient removal efficiency was 2500 and 2000 μmol/m2•s, while in terms of economic efficiency was 1000, 1500 and 2000 μmol/m2•s. Therefore, the optimum light intensity was found to be 2000 μmol/m2•s. In addition, the optimal experimental illumination time was determined as 120 h. The Chlorella vulgaris microalgae biological wastewater treatment system utilized in this research was able to purify the high-strength carbon and nitrogen wastewater effectively under optimum light wavelength and intensity. PMID:24499586

Highly photoresponsive and wavelength-selective circularly-polarized-light detector based on metal-oxides hetero-chiral thin film.

PubMed

Lee, Seung Hee; Singh, Dhruv Pratap; Sung, Ji Ho; Jo, Moon-Ho; Kwon, Ki Chang; Kim, Soo Young; Jang, Ho Won; Kim, Jong Kyu

2016-01-22

A highly efficient circularly-polarized-light detector with excellent wavelength selectivity is demonstrated with an elegant and simple microelectronics-compatible way. The circularly-polarized-light detector based on a proper combination of the geometry-controlled TiO2-SnO2 hetero-chiral thin film as an effective chiroptical filter and the Si active layer shows excellent chiroptical response with external quantum efficiency as high as 30% and high helicity selectivity of ~15.8% in an intended wavelength range. Furthermore, we demonstrated the ability of manipulating both bandwidth and responsivity of the detector simultaneously in whole visible wavelength range by a precise control over the geometry and materials constituting hetero-chiral thin film. The high efficiency, wavelength selectivity and compatibility with conventional microelectronics processes enabled by the proposed device can result in remarkable developments in highly integrated photonic platforms utilizing chiroptical responses.

Highly photoresponsive and wavelength-selective circularly-polarized-light detector based on metal-oxides hetero-chiral thin film

NASA Astrophysics Data System (ADS)

Lee, Seung Hee; Singh, Dhruv Pratap; Sung, Ji Ho; Jo, Moon-Ho; Kwon, Ki Chang; Kim, Soo Young; Jang, Ho Won; Kim, Jong Kyu

2016-01-01

A highly efficient circularly-polarized-light detector with excellent wavelength selectivity is demonstrated with an elegant and simple microelectronics-compatible way. The circularly-polarized-light detector based on a proper combination of the geometry-controlled TiO2-SnO2 hetero-chiral thin film as an effective chiroptical filter and the Si active layer shows excellent chiroptical response with external quantum efficiency as high as 30% and high helicity selectivity of ~15.8% in an intended wavelength range. Furthermore, we demonstrated the ability of manipulating both bandwidth and responsivity of the detector simultaneously in whole visible wavelength range by a precise control over the geometry and materials constituting hetero-chiral thin film. The high efficiency, wavelength selectivity and compatibility with conventional microelectronics processes enabled by the proposed device can result in remarkable developments in highly integrated photonic platforms utilizing chiroptical responses.

Low-coherence enhanced backscattering of light: characteristics and applications for colon cancer screening

NASA Astrophysics Data System (ADS)

Kim, Young L.; Pradhan, Prabhakar; Turzhitsky, Vladimir M.; Subramanian, Hariharan; Liu, Yang; Wali, Ramesh K.; Roy, Hemant K.; Backman, Vadim

2007-02-01

The phenomenon of enhanced backscattering (EBS) of light, also known as coherent backscattering (CBS) of light, is a spectacular manifestation of self-interference effects in elastic light scattering, which gives rise to an enhanced scattered intensity in the backward direction. Although EBS has been the object of intensive investigation in non-biological media over the last two decades, there have been only a few attempts to explore EBS for tissue characterization and diagnosis. We have recently made progress in the EBS measurements of biological tissue by taking advantage of lowcoherence (or partially coherent) illumination, which is referred to as low-coherence EBS (LEBS) of light. LEBS possess novel and intriguing properties such as speckle reduction, self-averaging effect, broadening of the EBS width, depth-selectivity, double scattering, and circular polarization memory effect. After we review the current state of research on LEBS, we discuss how these characteristics apply for early cancer detection, especially in colorectal cancer (CRC), which is the second leading cause of cancer mortality in the United States. Although colonoscopy remains the gold standard for CRC screening, resource constraints and potential complications make it impractical to perform colonoscopy on the entire population at risk (age > 50). Thus, identifying patients who are most likely to benefit from colonoscopy is of paramount importance. We demonstrate that LEBS measurements in easily accessible colonoscopically normal mucosa (e.g., in the rectum of the colon) can be used for predicting the risk of CRC, and thus LEBS has the potential to serve as accurate markers of the risk of neoplasia elsewhere in the colon.

Free-space coherent optical communication receivers implemented with photorefractive optical beam combiners

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.

1992-01-01

Performance measurements are reported concerning a coherent optical communication receiver that contained an iron doped indium phosphide photorefractive beam combiner, rather than a conventional optical beam splitter. The system obtained a bit error probability of 10(exp -6) at received signal powers corresponding to less than 100 detected photons per bit. The system used phase modulated Nd:YAG laser light at a wavelength of 1.06 microns.

300 mW of coherent light at 488 nm using a generic approach

NASA Astrophysics Data System (ADS)

Karamehmedović, Emir; Pedersen, Christian; Andersen, Martin T.; Tidemand-Lichtenberg, Peter

2008-02-01

We present a generic approach for efficient generation of CW light with a predetermined wavelength within the visible or UV spectrum. Based on sum-frequency generation (SFG), the circulating intra-cavity field of a high-finesse diode pumped CW solid-state laser (DPSSL) and the output from a tapered, single-frequency external cavity diode laser (ECDL) are mixed inside a 10 mm periodically poled KTP crstal (pp-KTP). The pp-KTP is situated inside the DPSSL cavity to enhance conversion efficiency of the nonlinear mixing process. This approach combines different solid state technologies; the tuneability of ECDLs, the high intra-cavity filed of DPSSLs and flexible quasi phase matching in pp-tapered ECDL with a center wavelength of 766 nm in combination with a high finesse Nd:YVo4 laser at 1342 nm. Up to 308 mW of light at 488nm was measured in our experiments. The conversion of te ECDL beam was up to 47% after it was transmitted through a PM fiber, and up to 32% without fiber coupling. Replacing the seed laser and the nonlinear crystal makes it possible to generate light at virtually any desired wavelength withing the visible spectrum.

Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source

PubMed Central

Reddy, Hemanth K.N.; Yoon, Chun Hong; Aquila, Andrew; Awel, Salah; Ayyer, Kartik; Barty, Anton; Berntsen, Peter; Bielecki, Johan; Bobkov, Sergey; Bucher, Maximilian; Carini, Gabriella A.; Carron, Sebastian; Chapman, Henry; Daurer, Benedikt; DeMirci, Hasan; Ekeberg, Tomas; Fromme, Petra; Hajdu, Janos; Hanke, Max Felix; Hart, Philip; Hogue, Brenda G.; Hosseinizadeh, Ahmad; Kim, Yoonhee; Kirian, Richard A.; Kurta, Ruslan P.; Larsson, Daniel S.D.; Duane Loh, N.; Maia, Filipe R.N.C.; Mancuso, Adrian P.; Mühlig, Kerstin; Munke, Anna; Nam, Daewoong; Nettelblad, Carl; Ourmazd, Abbas; Rose, Max; Schwander, Peter; Seibert, Marvin; Sellberg, Jonas A.; Song, Changyong; Spence, John C.H.; Svenda, Martin; Van der Schot, Gijs; Vartanyants, Ivan A.; Williams, Garth J.; Xavier, P. Lourdu

2017-01-01

Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65–70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. The data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency. PMID:28654088

Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source.

PubMed

Reddy, Hemanth K N; Yoon, Chun Hong; Aquila, Andrew; Awel, Salah; Ayyer, Kartik; Barty, Anton; Berntsen, Peter; Bielecki, Johan; Bobkov, Sergey; Bucher, Maximilian; Carini, Gabriella A; Carron, Sebastian; Chapman, Henry; Daurer, Benedikt; DeMirci, Hasan; Ekeberg, Tomas; Fromme, Petra; Hajdu, Janos; Hanke, Max Felix; Hart, Philip; Hogue, Brenda G; Hosseinizadeh, Ahmad; Kim, Yoonhee; Kirian, Richard A; Kurta, Ruslan P; Larsson, Daniel S D; Duane Loh, N; Maia, Filipe R N C; Mancuso, Adrian P; Mühlig, Kerstin; Munke, Anna; Nam, Daewoong; Nettelblad, Carl; Ourmazd, Abbas; Rose, Max; Schwander, Peter; Seibert, Marvin; Sellberg, Jonas A; Song, Changyong; Spence, John C H; Svenda, Martin; Van der Schot, Gijs; Vartanyants, Ivan A; Williams, Garth J; Xavier, P Lourdu

2017-06-27

Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65-70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. The data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency.

Highly photoresponsive and wavelength-selective circularly-polarized-light detector based on metal-oxides hetero-chiral thin film

PubMed Central

Lee, Seung Hee; Singh, Dhruv Pratap; Sung, Ji Ho; Jo, Moon-Ho; Kwon, Ki Chang; Kim, Soo Young; Jang, Ho Won; Kim, Jong Kyu

2016-01-01

A highly efficient circularly-polarized-light detector with excellent wavelength selectivity is demonstrated with an elegant and simple microelectronics-compatible way. The circularly-polarized-light detector based on a proper combination of the geometry-controlled TiO2-SnO2 hetero-chiral thin film as an effective chiroptical filter and the Si active layer shows excellent chiroptical response with external quantum efficiency as high as 30% and high helicity selectivity of ~15.8% in an intended wavelength range. Furthermore, we demonstrated the ability of manipulating both bandwidth and responsivity of the detector simultaneously in whole visible wavelength range by a precise control over the geometry and materials constituting hetero-chiral thin film. The high efficiency, wavelength selectivity and compatibility with conventional microelectronics processes enabled by the proposed device can result in remarkable developments in highly integrated photonic platforms utilizing chiroptical responses. PMID:26795601

Low-Coherence light source design for ESPI in-plane displacement measurements

NASA Astrophysics Data System (ADS)

Heikkinen, J. J.; Schajer, G. S.

2018-01-01

The ESPI method for surface deformation measurements requires the use of a light source with high coherence length to accommodate the optical path length differences present in the apparatus. Such high-coherence lasers, however, are typically large, delicate and costly. Laser diodes, on the other hand, are compact, mechanically robust and inexpensive, but unfortunately they have short coherence length. The present work aims to enable the use of a laser diode as an illumination source by equalizing the path lengths within an ESPI interferometer. This is done by using a reflection type diffraction grating to compensate for the path length differences. The high optical power efficiency of such diffraction gratings allows the use of much lower optical power than in previous interferometer designs using transmission gratings. The proposed concept was experimentally investigated by doing in-plane ESPI measurements using a high-coherence single longitudinal mode (SLM) laser, a laser diode and then a laser diode with path length optimization. The results demonstrated the limitations of using an uncompensated laser diode. They then showed the effectiveness of adding a reflection type diffraction grating to equalize the interferometer path lengths. This addition enabled the laser diode to produce high measurement quality across the entire field of view, rivaling although not quite equaling the performance of a high-coherence SLM laser source.

Integrated InAs/InP quantum-dot coherence comb lasers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lu, Zhenguo; Liu, Jiaren; Poole, Philip J.; Song, Chun-Ying; Webber, John; Mao, Linda; Chang, Shoude; Ding, Heping; Barrios, Pedro J.; Poitras, Daniel; Janz, Siegfried

2017-02-01

Current communication networks needs to keep up with the exponential growth of today's internet traffic, and telecommunications industry is looking for radically new integrated photonics components for new generation optical networks. We at National Research Council (NRC) Canada have successfully developed nanostructure InAs/InP quantum dot (QD) coherence comb lasers (CCLs) around 1.55 μm. Unlike uniform semiconductor layers in most telecommunication lasers, in these QD CCLs light is emitted and amplified by millions of semiconductor QDs less than 60 nm in diameter. Each QD acts like an isolated light source acting independently of its neighbours, and each QD emits light at its own unique wavelength. The end result is a QD CCL is more stable and has ultra-low timing jitter. But most importantly, a single QD CCL can simultaneously produce 50 or more separate laser beams at distinct wavelengths over the telecommunications C-band. Utilizing those unique properties we have put considerable effort well to design, grow and fabricate InAs/InP QD gain materials. After our integrated packaging and using electrical feedback-loop control systems, we have successfully demonstrated ultra-low intensity and phase noise, frequency-stabilized integrated QD CCLs with the repetition rates from 10 GHz to 100 GHz and the total output power up to 60 mW at room temperature. We have investigated their relative intensity noises, phase noises, RF beating signals and other performance of both filtered individual channel and the whole CCLs. Those highly phase-coherence comb lasers are the promising candidates for flexible bandwidth terabit coherent optical networks and signal processing applications.

Light sensitive memristor with bi-directional and wavelength-dependent conductance control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maier, P.; Hartmann, F., E-mail: fabian.hartmann@physik.uni-wuerzburg.de; Emmerling, M.

2016-07-11

We report the optical control of localized charge on positioned quantum dots in an electro-photo-sensitive memristor. Interband absorption processes in the quantum dot barrier matrix lead to photo-generated electron-hole-pairs that, depending on the applied bias voltage, charge or discharge the quantum dots and hence decrease or increase the conductance. Wavelength-dependent conductance control is observed by illumination with red and infrared light, which leads to charging via interband and discharging via intraband absorption. The presented memristor enables optical conductance control and may thus be considered for sensory applications in artificial neural networks as light-sensitive synapses or optically tunable memories.

Optical laser systems at the Linac Coherent Light Source

DOE PAGES

Minitti, Michael P.; Robinson, Joseph S.; Coffee, Ryan N.; ...

2015-04-22

Ultrafast optical lasers play an essential role in exploiting the unique capabilities of recently commissioned X-ray free-electron laser facilities such as the Linac Coherent Light Source (LCLS). Pump–probe experimental techniques reveal ultrafast dynamics in atomic and molecular processes and reveal new insights in chemistry, biology, material science and high-energy-density physics. This manuscript describes the laser systems and experimental methods that enable cutting-edge optical laser/X-ray pump–probe experiments to be performed at LCLS.

A dual-wavelength light-emitting diode based detector for flow-injection analysis process analysers.

PubMed

Huang, J; Liu, H; Tan, A; Xu, J; Zhao, X

1992-06-01

In this paper, a small dual-wavelength light-emitting diode (LED) based detector for FIA process analysers is designed. The detector's optical parts include a flow cell, a dual-wavelength LED and a photodiode. Neither mirrors nor lenses are used. The optical paths for the different light beams are almost the same, distinguishing it from previously reported LED based detectors. The detector's electronic components, including a signal amplifier, an A/D and D/A converter, and an Intel 8031 single-chip microcomputer, are integrated on one small board. In order to obtain response signals of approximate intensity for the two colours, the D/A converter and a multiplexer are used to adjust the emission intensity of the two colours respectively. Under microcomputer control, light beams are rapidly electronically modulated. Therefore, dark current and intensity of the light beams are measured almost simultaneously; as a result, the effect of drift is negligible. While a solution of absorbance 0.875 was measured repeatedly, an RSD (relative standard deviation) of 0.24% could be reached. Furthermore, such a detector with a red/yellow LED has been coupled with the FIA technique for the determination of 10(-6)M levels of cobalt.

Effects of Long-Wavelength Lighting on Refractive Development in Infant Rhesus Monkeys

PubMed Central

Smith, Earl L.; Hung, Li-Fang; Arumugam, Baskar; Holden, Brien A.; Neitz, Maureen; Neitz, Jay

2015-01-01

Purpose Differences in the spectral composition of lighting between indoor and outdoor scenes may contribute to the higher prevalence of myopia in children who spend low amounts of time outdoors. Our goal was to determine whether environments dominated by long-wavelength light promote the development of myopia. Methods Beginning at 25 ± 2 days of age, infant monkeys were reared with long-wavelength-pass (red) filters in front of one (MRL, n = 6) or both eyes (BRL, n = 7). The filters were worn continuously until 146 ± 7 days of age. Refractive development, corneal power, and vitreous chamber depth were assessed by retinoscopy, keratometry, and ultrasonography, respectively. Control data were obtained from 6 monkeys reared with binocular neutral density (ND) filters and 33 normal monkeys reared with unrestricted vision under typical indoor lighting. Results At the end of the filter-rearing period, the median refractive error for the BRL monkeys (+4.25 diopters [D]) was significantly more hyperopic than that for the ND (+2.22 D; P = 0.003) and normal monkeys (+2.38 D; P = 0.0001). Similarly, the MRL monkeys exhibited hyperopic anisometropias that were larger than those in normal monkeys (+1.70 ± 1.55 vs. −0.013 ± 0.33 D, P < 0.0001). The relative hyperopia in the treated eyes was associated with shorter vitreous chambers. Following filter removal, the filter-reared monkeys recovered from the induced hyperopic errors. Conclusions The observed hyperopic shifts indicate that emmetropization does not necessarily target the focal plane that maximizes luminance contrast and that reducing potential chromatic cues can interfere with emmetropization. There was no evidence that environments dominated by long wavelengths necessarily promote myopia development. PMID:26447984

Spectral fractionation detection of gold nanorod contrast agents using optical coherence tomography

PubMed Central

Jia, Yali; Liu, Gangjun; Gordon, Andrew Y.; Gao, Simon S.; Pechauer, Alex D.; Stoddard, Jonathan; McGill, Trevor J.; Jayagopal, Ashwath; Huang, David

2015-01-01

We demonstrate the proof of concept of a novel Fourier-domain optical coherence tomography contrast mechanism using gold nanorod contrast agents and a spectral fractionation processing technique. The methodology detects the spectral shift of the backscattered light from the nanorods by comparing the ratio between the short and long wavelength halves of the optical coherence tomography signal intensity. Spectral fractionation further divides the halves into sub-bands to improve spectral contrast and suppress speckle noise. Herein, we show that this technique can detect gold nanorods in intralipid tissue phantoms. Furthermore, cellular labeling by gold nanorods was demonstrated using retinal pigment epithelial cells in vitro. PMID:25836459

Coherent soft X-ray diffraction imaging of coliphage PR772 at the Linac coherent light source

DOE PAGES

Reddy, Hemanth K. N.; Yoon, Chun Hong; Aquila, Andrew; ...

2017-06-27

Single-particle diffraction from X-ray Free Electron Lasers offers the potential for molecular structure determination without the need for crystallization. In an effort to further develop the technique, we present a dataset of coherent soft X-ray diffraction images of Coliphage PR772 virus, collected at the Atomic Molecular Optics (AMO) beamline with pnCCD detectors in the LAMP instrument at the Linac Coherent Light Source. The diameter of PR772 ranges from 65–70 nm, which is considerably smaller than the previously reported ~600 nm diameter Mimivirus. This reflects continued progress in XFEL-based single-particle imaging towards the single molecular imaging regime. As a result, themore » data set contains significantly more single particle hits than collected in previous experiments, enabling the development of improved statistical analysis, reconstruction algorithms, and quantitative metrics to determine resolution and self-consistency.« less

Active control on high-order coherence and statistic characterization on random phase fluctuation of two classical point sources.

PubMed

Hong, Peilong; Li, Liming; Liu, Jianji; Zhang, Guoquan

2016-03-29

Young's double-slit or two-beam interference is of fundamental importance to understand various interference effects, in which the stationary phase difference between two beams plays the key role in the first-order coherence. Different from the case of first-order coherence, in the high-order optical coherence the statistic behavior of the optical phase will play the key role. In this article, by employing a fundamental interfering configuration with two classical point sources, we showed that the high- order optical coherence between two classical point sources can be actively designed by controlling the statistic behavior of the relative phase difference between two point sources. Synchronous position Nth-order subwavelength interference with an effective wavelength of λ/M was demonstrated, in which λ is the wavelength of point sources and M is an integer not larger than N. Interestingly, we found that the synchronous position Nth-order interference fringe fingerprints the statistic trace of random phase fluctuation of two classical point sources, therefore, it provides an effective way to characterize the statistic properties of phase fluctuation for incoherent light sources.

Coherent Doppler lidar for automated space vehicle, rendezvous, station-keeping and capture

NASA Technical Reports Server (NTRS)

Dunkin, James A.

1991-01-01

Recent advances in eye-safe, short wavelength solid-state lasers offer real potential for the development of compact, reliable, light-weight, efficient coherent lidar. Laser diode pumping of these devices has been demonstrated, thereby eliminating the need for flash lamp pumping, which has been a major drawback to the use of these lasers in space based applications. Also these lasers now have the frequency stability required to make them useful in coherent lidar, which offers all of the advantages of non-coherent lidar, but with the additional advantage that direct determination of target velocity is possible by measurement of the Doppler shift. By combining the Doppler velocity measurement capability with the inherent high angular resolution and range accuracy of lidar it is possible to construct Doppler images of targets for target motion assessment. A coherent lidar based on a Tm,Ho:YAG 2-micrometer wavelength laser was constructed and successfully field tested on atmospheric targets in 1990. This lidar incorporated an all solid state (laser diode pumped) master oscillator, in conjunction with a flash lamp pumped slave oscillator. Solid-state laser technology is rapidly advancing, and with the advent of high efficiency, high power, semiconductor laser diodes as pump sources, all-solid-state, coherent lidars are a real possibility in the near future. MSFC currently has a feasibility demonstration effort under way which will involve component testing, and preliminary design of an all-solid-state, coherent lidar for automatic rendezvous, and capture. This two year effort, funded by the Director's Discretionary Fund is due for completion in 1992.

Method and apparatus for eliminating coherent noise in a coherent energy imaging system without destroying spatial coherence

NASA Technical Reports Server (NTRS)

Shulman, A. R. (Inventor)

1971-01-01

A method and apparatus for substantially eliminating noise in a coherent energy imaging system, and specifically in a light imaging system of the type having a coherent light source and at least one image lens disposed between an input signal plane and an output image plane are, discussed. The input signal plane is illuminated with the light source by rotating the lens about its optical axis. In this manner, the energy density of coherent noise diffraction patterns as produced by imperfections such as dust and/or bubbles on and/or in the lens is distributed over a ring-shaped area of the output image plane and reduced to a point wherein it can be ignored. The spatial filtering capability of the coherent imaging system is not affected by this noise elimination technique.

Film characteristics pertinent to coherent optical data processing systems.

PubMed

Thomas, C E

1972-08-01

Photographic film is studied quantitatively as the input mechanism for coherent optical data recording and processing systems. The two important film characteristics are the amplitude transmission vs exposure (T(A) - E) curve and the film noise power spectral density. Both functions are measured as a function of the type of film, the type of developer, developer time and temperature, and the exposing and readout light wavelengths. A detailed analysis of a coherent optical spatial frequency analyzer reveals that the optimum do bias point for 649-F film is an amplitude transmission of about 70%. This operating point yields minimum harmonic and intermodulation distortion, whereas the 50% amplitude transmission bias point recommended by holographers yields maximum diffraction efficiency. It is also shown that the effective ac gain or contrast of the film is nearly independent of the development conditions for a given film. Finally, the linear dynamic range of one particular coherent optical spatial frequency analyzer is shown to be about 40-50 dB.

Laser therapy by noncoherent light field of radiation.

PubMed

Djibladze, M I; Melikishvili, Z G; Uchaneishvili, S D

1997-01-01

Conducted researches on study of interaction of radiation with blood have shown, that the interaction is the most effective for light with wavelengths in the range of 600-1000 nm that corresponds to the minimum absorption factor of the whole blood. Calculations show, that at interaction of radiation with blood considerably grows effective (electronic) temperature of biological environment, that results in sharp increase of speed of biochemical reactions. The absence of necessity of application of laser radiation coherence in lasertherapy permits to create high efficient noncoherent sources of light on the basis of the GaALAs(Zn) crystals, radiating with two maxima of wavelengths 675 and 900 nm. The radiation spectrum of GaALAs(Zn) crystals falls in the most favourable area of a blood absorption spectrum.

Path induced coherent energy transfer in light-harvesting complexes in purple bacteria

NASA Astrophysics Data System (ADS)

Sun, Kewei; Ye, Jun; Zhao, Yang

2014-09-01

Features of path dependent energy transfer in a dual-ring light-harvesting (LH2) complexes (B850) system have been examined in detail systematically. The Frenkel-Dirac time dependent variational method with the Davydov D1 Ansatz is employed with detailed evolution of polaron dynamics in real space readily obtained. It is found that the phase of the transmission amplitude through the LH2 complexes plays an important role in constructing the coherent excitonic energy transfer. It is also found that the symmetry breaking caused by the dimerization of bacteriochlorophylls and coherence or correlation between two rings will be conducive in enhancing the exciton transfer efficiency.

Experimental study of near-field light collection efficiency of aperture fiber probe at near-infrared wavelengths.

PubMed

Tsumori, Nobuhiro; Takahashi, Motoki; Sakuma, Yoshiki; Saiki, Toshiharu

2011-10-10

We examined the near-field collection efficiency of near-infrared radiation for an aperture probe. We used InAs quantum dots as ideal point light sources with emission wavelengths ranging from 1.1 to 1.6 μm. We experimentally investigated the wavelength dependence of the collection efficiency and compared the results with computational simulations that modeled the actual probe structure. The observed degradation in the collection efficiency is attributed to the cutoff characteristics of the gold-clad tapered waveguide, which approaches an ideal conductor at near-infrared wavelengths. © 2011 Optical Society of America

Low level light therapy by LED of different wavelength induces angiogenesis and improves ischemic wound healing.

PubMed

Dungel, Peter; Hartinger, Joachim; Chaudary, Sidrah; Slezak, Paul; Hofmann, Anna; Hausner, Thomas; Strassl, Martin; Wintner, Ernst; Redl, Heinz; Mittermayr, Rainer

2014-12-01

Low-level light therapy (LLLT) has been revealed as a potential means to improve wound healing. So far, most studies are being performed with irradiation in the red to near-infrared spectra. Recently, we showed that blue light (470 nm) can significantly influence biological systems such as nitric oxide (NO) metabolism and is able to release NO from nitrosyl-hemoglobin or mitochondrial protein complexes. Therefore, the aim of this study was to evaluate and compare the therapeutic value of blue or red light emitting diodes (LEDs) on wound healing in an ischemia disturbed rodent flap model. An abdominal flap was rendered ischemic by ligation of one epigastric bundle and subjected to LED illumination with a wavelength of 470 nm (blue, n = 8) or 629 nm (red, n = 8) each at 50 mW/cm(2) and compared to a non-treated control group (n = 8). Illumination was performed for 10 minutes on five consecutive days. LED therapy with both wavelengths significantly increased angiogenesis in the sub-epidermal layer and intramuscularly (panniculus carnosus muscle) which was associated with significantly improved tissue perfusion 7 days after the ischemic insult. Accordingly, tissue necrosis was significantly reduced and shrinkage significantly less pronounced in the LED-treated groups of both wavelengths. LED treatment of ischemia challenged tissue improved early wound healing by enhancing angiogenesis irrespective of the wavelength thus delineating this noninvasive means as a potential, cost effective tool in complicated wounds. © 2014 Wiley Periodicals, Inc.

Nanometer resolution optical coherence tomography using broad bandwidth XUV and soft x-ray radiation

DOE PAGES

Fuchs, Silvio; Rödel, Christian; Blinne, Alexander; ...

2016-02-10

Optical coherence tomography (OCT) is a non-invasive technique for cross-sectional imaging. It is particularly advantageous for applications where conventional microscopy is not able to image deeper layers of samples in a reasonable time, e.g. in fast moving, deeper lying structures. However, at infrared and optical wavelengths, which are commonly used, the axial resolution of OCT is limited to about 1 μm, even if the bandwidth of the light covers a wide spectral range. Here, we present extreme ultraviolet coherence tomography (XCT) and thus introduce a new technique for non-invasive cross-sectional imaging of nanometer structures. XCT exploits the nanometerscale coherence lengthsmore » corresponding to the spectral transmission windows of, e.g., silicon samples. The axial resolution of coherence tomography is thus improved from micrometers to a few nanometers. Tomographic imaging with an axial resolution better than 18 nm is demonstrated for layer-type nanostructures buried in a silicon substrate. Using wavelengths in the water transmission window, nanometer-scale layers of platinum are retrieved with a resolution better than 8 nm. As a result, XCT as a nondestructive method for sub-surface tomographic imaging holds promise for several applications in semiconductor metrology and imaging in the water window.« less

Comparing Wavelengths

NASA Image and Video Library

2015-12-12

This side-by-side rendering of the Sun at the same time in two different wavelengths of extreme ultraviolet light helps to visualize the differing features visible in each wavelength (Dec. 10-11, 2015). Most prominently, we can see much finer strands of plasma looping above the surface in the 171 Angstrom wavelength (gold) than in the 304 Angstrom wavelength (red), which captures cooler plasma closer to the Sun's surface. SDO observes the Sun in 10 different wavelengths with each one capturing somewhat different features at various temperatures and elevations above the Sun. http://photojournal.jpl.nasa.gov/catalog/PIA20214

Polarization study of a supercontinuum light source for different wavelengths through a photonic crystal fiber

NASA Astrophysics Data System (ADS)

Valle-Atilano, F. J.; Estudillo-Ayala, J. M.; Filoteo-Razo, J. D.; Hernández-Garcia, J. C.; Lauterio-Cruz, J. P.; Jáuregui-Vázquez, D.; Ibarra-Escamilla, B.; Rojas-Laguna, R.; Pottiez, O.; Kuzin, E. A.

2016-03-01

In this work we show the changes of polarization at different wavelengths in the end of a photonic crystal fiber (PCF) by means bandpass filters in a supercontinuum light source. A linear and circular polarization was introduced in a piece of PCF, showing the changes of the polarization for each wavelength of each one of the filters from 450 to 700nm. We used a microchip laser as pumping source with wavelength of 532nm and short pulses of 650ps with repetition rate of 5kHz. We obtained a continuous spectrum in the visible spectral region, showing a comparison of the polarization state at the fiber input with respect to polarization state in the fiber output for different wavelengths by rotating the axes of the PCF.

Anterior Eye Imaging with Optical Coherence Tomography

NASA Astrophysics Data System (ADS)

Huang, David; Li, Yan; Tang, Maolong

The development of corneal and anterior segment optical coherence tomography (OCT) technology has advanced rapidly in recently years. The scan geometry and imaging wavelength are both important choices to make in designing anterior segment OCT systems. Rectangular scan geometry offers the least image distortion and is now used in most anterior OCT systems. The wavelength of OCT light source affects resolution and penetration. An optimal choice of the OCT imaging wavelength (840, 1,050, or 1,310 nm) depends on the application of interest. Newer generation Fourier-domain OCT technology can provide scan speed 100-1000 times faster than the time-domain technology. Various commercial anterior OCT systems are available on the market. A wide spectrum of diagnostic and surgical applications using anterior segment OCT had been investigated, including mapping of corneal and epithelial thicknesses, keratoconus screening, measuring corneal refractive power, corneal surgery planning and evaluation in LASIK, intracorneal ring implantation, assessment of angle closure glaucoma, anterior chamber biometry and intraocular lens implants, intraocular lens power calculation, and eye bank donor cornea screening.

Impact of long-wavelength UVA and visible light on melanocompetent skin.

PubMed

Mahmoud, Bassel H; Ruvolo, Eduardo; Hexsel, Camile L; Liu, Yang; Owen, Michael R; Kollias, Nikiforos; Lim, Henry W; Hamzavi, Iltefat H

2010-08-01

The purpose of this study was to determine the effect of visible light on the immediate pigmentation and delayed tanning of melanocompetent skin; the results were compared with those induced by long-wavelength UVA (UVA1). Two electromagnetic radiation sources were used to irradiate the lower back of 20 volunteers with skin types IV-VI: UVA1 (340-400 nm) and visible light (400-700 nm). Pigmentation was assessed by visual examination, digital photography with a cross-polarized filter, and diffused reflectance spectroscopy at 7 time points over a 2-week period. Confocal microscopy and skin biopsies for histopathological examination using different stains were carried out. Irradiation was also carried out on skin type II. Results showed that although both UVA1 and visible light can induce pigmentation in skin types IV-VI, pigmentation induced by visible light was darker and more sustained. No pigmentation was observed in skin type II. The quality and quantity of pigment induced by visible light and UVA1 were different. These findings have potential implications on the management of photoaggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

Wavelength, beam size and type dependences of cerebral low-level light therapy: A Monte Carlo study on visible Chinese human

NASA Astrophysics Data System (ADS)

Li, Ting; Zhao, Yue; Duan, Meixue; Sun, Yunlong; Li, Kai

2014-02-01

Low level light therapy (LLLT) has been clinically utilized for many indications in medicine requiring protection from cell/tissue death, stimulation of healing and repair of injuries, pain reduction, swelling and inflammation. Presently, use of LLLT to treat stroke, traumatic brain injury, and cognitive dysfunction is attracting growing interest. Near-infrared light can penetrate into the brain tissue, allowing noninvasive treatment to be carried out with few treatment-related adverse events. Optimization of LLLT treatment effect is one key issue of the field; however, only a few experimental tests on mice for wavelength selection have been reported. We addressed this issue by low-cost, straightforward and quantitative comparisons on light dosage distribution in Visible Chinese human head with Monte Carlo modeling of light propagation. Optimized selection in wavelength, beam type and size were given based on comparisons among frequently-used setups (i.e., wavelengths: 660 nm, 810 nm, 980 nm; beam type: Gaussian and flat beam; beam diameter: 2 cm, 4 cm, 6cm).This study provided an efficient way to guide optimization of LLLT setup and selection on wavelength, beam type and size for clinical brain LLLT.

Coherent Perfect Rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Dawson, Nathan; Andrews, James

2012-04-01

Two classes of conservative, linear, optical rotary effects (optical activity and Faraday rotation) are distinguished by their behavior under time reversal. In analogy with coherent perfect absorption, where counterpropagating light fields are controllably converted into other degrees of freedom, we show that in a linear-conservative medium only time-odd (Faraday) rotation is capable of coherent perfect rotation, by which we mean the complete transfer of counterpropagating coherent light fields into their orthogonal polarization. This highlights the necessity of time reversal odd processes (not just absorption) and coherence in perfect mode conversion and may inform device design.

Effects of a chronic reduction of short-wavelength light input on melatonin and sleep patterns in humans: evidence for adaptation.

PubMed

Giménez, Marina C; Beersma, Domien G M; Bollen, Pauline; van der Linden, Matthijs L; Gordijn, Marijke C M

2014-06-01

Light is an important environmental stimulus for the entrainment of the circadian clock and for increasing alertness. The intrinsically photosensitive ganglion cells in the retina play an important role in transferring this light information to the circadian system and they are elicited in particular by short-wavelength light. Exposure to short wavelengths is reduced, for instance, in elderly people due to yellowing of the ocular lenses. This reduction may be involved in the disrupted circadian rhythms observed in aged subjects. Here, we tested the effects of reduced blue light exposure in young healthy subjects (n = 15) by using soft orange contact lenses (SOCL). We showed (as expected) that a reduction in the melatonin suppressing effect of light is observed when subjects wear the SOCL. However, after chronic exposure to reduced (short wavelength) light for two consecutive weeks we observed an increase in sensitivity of the melatonin suppression response. The response normalized as if it took place under a polychromatic light pulse. No differences were found in the dim light melatonin onset or in the amplitude of the melatonin rhythms after chronic reduced blue light exposure. The effects on sleep parameters were limited. Our results demonstrate that the non-visual light system of healthy young subjects is capable of adapting to changes in the spectral composition of environmental light exposure. The present results emphasize the importance of considering not only the short-term effects of changes in environmental light characteristics.

High-power picosecond fiber source for coherent Raman microscopy

PubMed Central

Kieu, Khanh; Saar, Brian G.; Holtom, Gary R.; Xie, X. Sunney; Wise, Frank W.

2011-01-01

We report a high-power picosecond fiber pump laser system for coherent Raman microscopy (CRM). The fiber laser system generates 3.5 ps pulses with 6 W average power at 1030 nm. Frequency doubling yields more than 2 W of green light, which can be used to pump an optical parametric oscillator to produce the pump and the Stokes beams for CRM. Detailed performance data on the laser and the various wavelength conversion steps are discussed, together with representative CRM images of fresh animal tissue obtained with the new source. PMID:19571996

Effects of melatonin and green-wavelength LED light on the physiological stress and immunity of goldfish, Carassius auratus, exposed to high water temperature.

PubMed

Jung, Seo Jin; Kim, Na Na; Choi, Young Jae; Choi, Ji Yong; Choi, Young-Ung; Heo, Youn Seong; Choi, Cheol Young

2016-10-01

This study investigated the effects of increasing water temperature (22-30 °C) on the physiological stress response and immunity of goldfish, Carassius auratus, and the ability of green light-emitting diode (LED) irradiation or melatonin injections to mitigate this temperature-induced stress. To evaluate the effects of either green-wavelength LED light or melatonin on stress in goldfish, we measured plasma triiodothyronine (T3), thyroxine (T4), and thyroid hormone receptor (TR) mRNA expression; plasma cortisol and glucose; and immunoglobulin M (IgM) and lysozyme mRNA expression. The thyroid hormone activities, TR mRNA expression, and plasma cortisol and glucose were higher in goldfish exposed to high-temperature water, but were lower after exposure to melatonin or green-wavelength LED light. Lysozyme mRNA expression and plasma IgM activity and protein expression were lower after exposure to high water temperatures and higher after melatonin or green-wavelength LED light treatments. Therefore, high water temperature induced stress and decreased immunity; however, green-wavelength LED light and melatonin treatments mitigated the effects of stress and enhanced immunity. The benefits of melatonin decreased with time, whereas those of green-wavelength LED treatment did not.

Doubly differential star-16-QAM for fast wavelength switching coherent optical packet transceiver.

PubMed

Liu, Fan; Lin, Yi; Walsh, Anthony J; Yu, Yonglin; Barry, Liam P

2018-04-02

A coherent optical packet transceiver based on doubly differential star 16-ary quadrature amplitude modulation (DD-star-16-QAM) is presented for spectrally and energy efficient reconfigurable networks. The coding and decoding processes for this new modulation format are presented, simulations and experiments are then performed to investigate the performance of the DD-star-16-QAM in static and dynamic scenarios. The static results show that the influence of frequency offset (FO) can be cancelled out by doubly differential (DD) coding and the correction range is only limited by the electronic bandwidth of the receivers. In the dynamic scenario with a time-varying FO and linewidth, the DD-star-16-QAM can overcome the time-varying FO, and the switching time of around 70 ns is determined by the time it takes the dynamic linewidth to reach the requisite level. This format can thus achieve a shorter waiting time after switching tunable lasers than the commonly used square-16-QAM, in which the transmission performance is limited by the frequency transients after the wavelength switch.

Ultra-high resolution spectral domain optical coherence tomography using supercontinuum light source

NASA Astrophysics Data System (ADS)

Lim, Yiheng; Yatagai, Toyohiko; Otani, Yukitoshi

2016-04-01

An ultra-high resolution spectral domain optical coherence tomography (SD-OCT) was developed using a cost-effective supercontinuum laser. A spectral filter consists of a dispersive prism, a cylindrical lens and a right-angle prism was built to transmit the wavelengths in range 680-940 nm to the OCT system. The SD-OCT has achieved 1.9 μm axial resolution and the sensitivity was estimated to be 91.5 dB. A zero-crossing fringes matching method which maps the wavelengths to the pixel indices of the spectrometer was proposed for the OCT spectral calibration. A double sided foam tape as a static sample and the tip of a middle finger as a biological sample were measured by the OCT. The adhesive and the internal structure of the foam of the tape were successfully visualized in three dimensions. Sweat ducts was clearly observed in the OCT images at very high resolution. To the best of our knowledge, this is the first demonstration of ultra-high resolution visualization of sweat duct by OCT.

Characterization of edge effects in precision low-coherence interferometry using broadband light sources

NASA Astrophysics Data System (ADS)

Taudt, Ch.; Baselt, T.; Nelsen, B.; Assmann, H.; Greiner, A.; Koch, E.; Hartmann, P.

2017-06-01

Within this work an alternative approach to precision surface profilometry based on a low-coherence interferometer is presented. Special emphasis is placed on the characterization of edge effects, which influence the measurement result on sharp edges and steep slopes. In contrast to other works, this examination focuses on the comparison of very broadband light sources such as a supercontinuum white-light source (SC; 380 - 1100 nm) and a laser-driven plasma light source (LDP; 200 - 1100 nm) and their influence on the formation of these effects. The interferometer is equipped with one of these broadband light sources and a defined dispersion over a given spectral range. The spectral width of the light sources in combination with the dispersive element defines the possible measurement range and resolution. Instead of detecting the signals only in a one-dimensional manner, an imaging spectrometer on the basis of a high resolution CMOS-camera is set-up. Through the introduction of a defined dispersion, a controlled phase variation in the spectral domain is created. This phase variation is dependent on the optical path difference between both arms and can therefore be used as a measure for the height of a structure which is present in one arm. The results of measurements on a 100 nm height standard with both selected light sources have been compared. Under consideration of the coherence length of both light sources of 1.58 μm for the SC source and 1.81 m for the LDP source differences could be recorded. Especially at sharp edges, the LDP light source could record height changes with slopes twice as steep as the SC source. Furthermore, it became obvious, that measurements with the SC source tend to show edge effects like batwings due to diffraction. Additional effects on the measured roughness and the flatness of the profile were investigated and discussed.

Coherence and visibility for vectorial light.

PubMed

Luis, Alfredo

2010-08-01

Two-path interference of transversal vectorial waves is embedded within a larger scheme: this is four-path interference between four scalar waves. This comprises previous approaches to coherence between vectorial waves and restores the equivalence between correlation-based coherence and visibility.

Linac Coherent Light Source Undulator RF BPM System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lill, R.M.; Morrison, L.H.; Waldschmidt, G.J.

2007-04-17

The Linac Coherent Light Source (LCLS) will be the world's first x-ray free-electron laser (FEL) when it becomes operational in 2009. The LCLS is currently in the construction phase. The beam position monitor (BPM) system planned for the LCLS undulator will incorporate a high-resolution X-band cavity BPM system described in this paper. The BPM system will provide high-resolution measurements of the electron beam trajectory on a pulse-to-pulse basis and over many shots. The X-band cavity BPM size, simple fabrication, and high resolution make it an ideal choice for LCLS beam position detection. We will discuss the system specifications, design, andmore » prototype test results.« less

Colposcopic imaging using visible-light optical coherence tomography.

PubMed

Duan, Lian; McRaven, Michael D; Liu, Wenzhong; Shu, Xiao; Hu, Jianmin; Sun, Cheng; Veazey, Ronald S; Hope, Thomas J; Zhang, Hao F

2017-05-01

High-resolution colposcopic optical coherence tomography (OCT) provides key anatomical measures, such as thickness and minor traumatic injury of vaginal epithelium, of the female reproductive tract noninvasively. This information can be helpful in both fundamental investigations in animal models and disease screenings in humans. We present a fiber-based visible-light OCT and two probe designs for colposcopic application. One probe conducts circular scanning using a DC motor, and the other probe is capable of three-dimensional imaging over a 4.6 × 4.6 - mm 2 area using a pair of galvo scanners. Using this colposcopic vis-OCT with both probes, we acquired high-resolution images from whole isolated macaque vaginal samples and identified biopsy lesions.

Colposcopic imaging using visible-light optical coherence tomography

NASA Astrophysics Data System (ADS)

Duan, Lian; McRaven, Michael D.; Liu, Wenzhong; Shu, Xiao; Hu, Jianmin; Sun, Cheng; Veazey, Ronald S.; Hope, Thomas J.; Zhang, Hao F.

2017-05-01

High-resolution colposcopic optical coherence tomography (OCT) provides key anatomical measures, such as thickness and minor traumatic injury of vaginal epithelium, of the female reproductive tract noninvasively. This information can be helpful in both fundamental investigations in animal models and disease screenings in humans. We present a fiber-based visible-light OCT and two probe designs for colposcopic application. One probe conducts circular scanning using a DC motor, and the other probe is capable of three-dimensional imaging over a 4.6×4.6-mm2 area using a pair of galvo scanners. Using this colposcopic vis-OCT with both probes, we acquired high-resolution images from whole isolated macaque vaginal samples and identified biopsy lesions.

Wavelength Comparison

NASA Image and Video Library

2016-10-27

The difference in features that are visible in different wavelengths of extreme ultraviolet light can be stunning as we see when we compare very large coronal holes, easily seen in the AIA 171 image (colorized bronze) yet hardly perceptible in the AIA 304 image (colorized red). Both were taken at just about the same time (Oct. 27, 2016). Coronal holes are areas of open magnetic field that carry solar wind out into space. In fact, these holes are currently causing a lot of geomagnetic activity here on Earth. The bronze image wavelength captures material that is much hotter and further up in the corona than the red image. The comparison dramatizes the value of observing the sun in multiple wavelengths of light. Movies are available at http://photojournal.jpl.nasa.gov/catalog/PIA15377

Attosecond Light and Science at the Time-scale of the Electron - Coherent X-Rays from Tabletop Ultrafast Lasers

ScienceCinema

Margaret, Murnane [University of Colorado, Boulder and NIST

2017-12-09

Ever since the invention of the laser 50 years ago and its application in nonlinear optics, scientists have been striving to extend coherent laser beams into the x-ray region of the spectrum. Very recently however, the prospects for tabletop coherent sources at very short wavelengths, even in the hard x-ray region of the spectrum at wavelengths < 1nm, have brightened considerably. This advance is possible by taking nonlinear optics techniques to an extreme - physics that is the direct result of a new ability to manipulate electrons on the fastest, attosecond, time-scales of our natural world. Several applications have already been demonstrated, including making a movie of how electrons rearrange in a chemical bond changes shape as a molecule breaks apart, following how fast a magnetic material can flip orientation, understanding how fast heat flows in a nanocircuit, or building a microscope without lenses. Nature 460, 1088 (2009); Science 317, 775 (2007); Physical Review Letters 103, 257402 (2009); Nature Materials 9, 26 (2010); Nature 463, 214 (2010); Science 322, 1207 (2008).

Dependence of light transmission through human skin on incident beam diameter at different wavelengths

NASA Astrophysics Data System (ADS)

Zhao, ZhongQuan; Fairchild, Paul W.

1998-05-01

For many skin treatments with light, it is important to have deep photon penetration into the skin. Because of absorption and scattering of photons by skin tissue, both the color and the diameter of the incident beam affect the penetration depth of photons. In this study, the dependence of light transmission through human skin tissues (ear lobs and between the fingers) has been measured in-vivo at six wavelengths (532 nm, 632 nm, 675 nm, 810 nm, 911 nm, and 1064 nm). The same measurement was also made on pig skin in-vitro for comparison. It was observed that (1) the photons at 1064 nm penetrate deeper than the other colors studied for a given incident beam diameter; and (2) the transmittance at a particular wavelength increases asymptotically with incident beam diameter. For some skin tissues, the transmittance flattens at about 8 mm for 532 nm photons and approaches saturation at about 12 mm for all other colors. The results on pig skin is similar.

Towards strong light-matter coupling at the single-resonator level with sub-wavelength mid-infrared nano-antennas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malerba, M.; De Angelis, F., E-mail: francesco.deangelis@iit.it; Ongarello, T.

2016-07-11

We report a crucial step towards single-object cavity electrodynamics in the mid-infrared spectral range using resonators that borrow functionalities from antennas. Room-temperature strong light-matter coupling is demonstrated in the mid-infrared between an intersubband transition and an extremely reduced number of sub-wavelength resonators. By exploiting 3D plasmonic nano-antennas featuring an out-of-plane geometry, we observed strong light-matter coupling in a very low number of resonators: only 16, more than 100 times better than what reported to date in this spectral range. The modal volume addressed by each nano-antenna is sub-wavelength-sized and it encompasses only ≈4400 electrons.

The X-ray correlation spectroscopy instrument at the Linac Coherent Light Source

DOE PAGES

Alonso-Mori, Roberto; Caronna, Chiara; Chollet, Matthieu; ...

2015-03-03

The X-ray Correlation Spectroscopy instrument is dedicated to the study of dynamics in condensed matter systems using the unique coherence properties of free-electron lasers. It covers a photon energy range of 4–25 keV. The intrinsic temporal characteristics of the Linac Coherent Light Source, in particular the 120 Hz repetition rate, allow for the investigation of slow dynamics (milliseconds) by means of X-ray photon correlation spectroscopy. Double-pulse schemes could probe dynamics on the picosecond timescale. In addition, a description of the instrument capabilities and recent achievements is presented.

To what extent is coherence lost in tissue?

NASA Astrophysics Data System (ADS)

Hode, Tomas; Jenkins, Peter; Jordison, Stefan; Hode, Lars

2011-03-01

In a series of experiments we investigated the extent to which coherence is preserved in tissue. We investigated whether the decrease in coherence length is dependent upon the coherence length of the illuminating light and possibly also if the light is polarized. We compared highly coherent light from a HeNe laser, and less coherent light from a semiconductor laser, in scattering media such as raw ground beef. We studied the laser speckle contrast after passing through 1 - 2 cm of meat. The conclusion is that the laser light is still coherent enough to form laser speckles after passing through a 2 cm thickness of meat.

Functional optical coherence tomography: principles and progress

NASA Astrophysics Data System (ADS)

Kim, Jina; Brown, William; Maher, Jason R.; Levinson, Howard; Wax, Adam

2015-05-01

In the past decade, several functional extensions of optical coherence tomography (OCT) have emerged, and this review highlights key advances in instrumentation, theoretical analysis, signal processing and clinical application of these extensions. We review five principal extensions: Doppler OCT (DOCT), polarization-sensitive OCT (PS-OCT), optical coherence elastography (OCE), spectroscopic OCT (SOCT), and molecular imaging OCT. The former three have been further developed with studies in both ex vivo and in vivo human tissues. This review emphasizes the newer techniques of SOCT and molecular imaging OCT, which show excellent potential for clinical application but have yet to be well reviewed in the literature. SOCT elucidates tissue characteristics, such as oxygenation and carcinogenesis, by detecting wavelength-dependent absorption and scattering of light in tissues. While SOCT measures endogenous biochemical distributions, molecular imaging OCT detects exogenous molecular contrast agents. These newer advances in functional OCT broaden the potential clinical application of OCT by providing novel ways to understand tissue activity that cannot be accomplished by other current imaging methodologies.

A Possible Application of Coherent Light Scattering on Biological Fluids

NASA Astrophysics Data System (ADS)

Chicea, Dan; Chicea, Liana Maria

2007-04-01

Human urine from both healthy patients and patients with different diseases was used as scattering medium in a coherent light scattering experiment. The time variation of the light intensity in the far field speckle image was acquired using a data acquisition system on a PC and a time series resulted for each sample. The autocorrelation function for each sample was calculated and the autocorrelation time was determined. The same samples were analyzed in a medical laboratory using the standard procedure. We found so far that the autocorrelation time is differently modified by the presence of pus, albumin, urobilin and sediments. The results suggest a fast procedure that can be used as laboratory test to detect the presence not of each individual component in suspensions but of big conglomerates as albumin, cylinders, oxalate crystals.

Fourth Generation Light Sources

NASA Astrophysics Data System (ADS)

Winick, Herman

1997-05-01

Concepts and designs are now being developed at laboratories around the world for light sources with performance levels that exceed present sources, including the very powerful and successful third generation synchrotron radiation sources that have come on line in the past few years. Workshops (M. Cornacchia and H. Winick (eds), Workshop on Fourth Generation Light Sources, Feb. 24-27, 1992, SSRL Report 92/02) (J.-L. Laclare (ed), ICFA Workshop on Fourth Generation Light Sources, Jan. 22-25, 1996, ESRF Report) have been held to review directions for future sources. A main thrust is to increase the brightness and coherence of the radiation using storage rings with lower electron-beam emittance or free-electron lasers (FELs). In the infra-red part of the spectrum very high brightness and coherence is already provided by FEL user facilities driven by linacs and storage rings. It now appears possible to extend FEL operation to the VUV, soft X-ray and even hard X-ray spectral range, to wavelengths down to the angstrom range, using high energy linacs equipped with high-brightness rf photoinjectors and bunch-length compressors. R&D to develop such sources is in progress at BNL, DESY, KEK, SLAC and other laboratories. In the absence of mirrors to form optical cavities, short wavelengths are reached in FEL systems in which a high peak current, low-emittance electron beam becomes bunch-density modulated at the optical wavelength in a single pass through a long undulator by self-amplified spontaneous emission (SASE); i.e.; startup from noise. A proposal to use the last kilometer of the three kilometer SLAC linac (the first two kilometers will be used for injection to the PEP II B-Factory) to provide 15 GeV electron beams to reach 1.5 Angstroms by SASE in a 100 m long undulator is in preparation.

Light polarization management via reflection from arrays of sub-wavelength metallic twisted bands

NASA Astrophysics Data System (ADS)

Nawrot, M.; Haberko, J.; Zinkiewicz, Ł.; Wasylczyk, P.

2017-12-01

With constant progress of nano- and microfabrication technologies, photolithography in particular, a number of sub-wavelength metallic structures have been demonstrated that can be used to manipulate light polarization. Numerical simulations of light propagation hint that helical twisted bands can have interesting polarization properties. We use three-dimensional two-photon photolithography (direct laser writing) to fabricate a few-micrometer-thick arrays of twisted bands and coat them uniformly with metal. We demonstrate that circular polarization can be generated from linear polarization upon reflection from such structures over a broad range of frequencies in the mid infrared.

Detecting Topological Defect Dark Matter Using Coherent Laser Ranging System

PubMed Central

Yang, Wanpeng; Leng, Jianxiao; Zhang, Shuangyou; Zhao, Jianye

2016-01-01

In the last few decades, optical frequency combs with high intensity, broad optical bandwidth, and directly traceable discrete wavelengths have triggered rapid developments in distance metrology. However, optical frequency combs to date have been limited to determine the absolute distance to an object (such as satellite missions). We propose a scheme for the detection of topological defect dark matter using a coherent laser ranging system composed of dual-combs and an optical clock via nongravitational signatures. The dark matter field, which comprises a defect, may interact with standard model particles, including quarks and photons, resulting in the alteration of their masses. Thus, a topological defect may function as a dielectric material with a distinctive frequency-depend index of refraction, which would cause the time delay of a periodic extraterrestrial or terrestrial light. When a topological defect passes through the Earth, the optical path of long-distance vacuum path is altered, this change in optical path can be detected through the coherent laser ranging system. Compared to continuous wavelength(cw) laser interferometry methods, dual-comb interferometry in our scheme excludes systematic misjudgement by measuring the absolute optical path length. PMID:27389642

Light field measurement based on the single-lens coherent diffraction imaging

NASA Astrophysics Data System (ADS)

Shen, Cheng; Tan, Jiubin; Liu, Zhengjun

2018-01-01

Plenoptic camera and holography are popular light field measurement techniques. However, the low resolution or the complex apparatus hinders their widespread application. In this paper, we put forward a new light field measurement scheme. The lens is introduced into coherent diffraction imaging to operate an optical transform, extended fractional Fourier transform. Combined with the multi-image phase retrieval algorithm, the scheme is proved to hold several advantages. It gets rid of the support requirement and is much easier to implement while keeping a high resolution by making full use of the detector plane. Also, it is verified that our scheme has a superiority over the direct lens focusing imaging in amplitude measurement accuracy and phase retrieval ability.

Inverse Doppler shift and control field as coherence generators for the stability in superluminal light

NASA Astrophysics Data System (ADS)

Ghafoor, Fazal; Bacha, Bakht Amin; Khan, Salman

2015-05-01

A gain-based four-level atomic medium for the stability in superluminal light propagation using control field and inverse Doppler shift as coherence generators is studied. In regimes of weak and strong control field, a broadband and multiple controllable transparency windows are, respectively, identified with significantly enhanced group indices. The observed Doppler effect for the class of high atomic velocity of the medium is counterintuitive in comparison to the effect of the class of low atomic velocity. The intensity of each of the two pump fields is kept less than the optimum limit reported in [M. D. Stenner and D. J. Gauthier, Phys. Rev. A 67, 063801 (2003), 10.1103/PhysRevA.67.063801] for stability in the superluminal light pulse. Consequently, superluminal stable domains with the generated coherence are explored.

Quantum coherence effects in natural light-induced processes: cis-trans photoisomerization of model retinal under incoherent excitation.

PubMed

Tscherbul, Timur V; Brumer, Paul

2015-12-14

We present a theoretical study of quantum coherence effects in the primary cis-trans photoisomerization of retinal in rhodopsin induced by incoherent solar light. Using the partial secular Bloch-Redfield quantum master equation approach based on a two-state two-mode linear vibronic coupling model of the retinal chromophore [S. Hahn and G. Stock, J. Phys. Chem. B, 2000, 104, 1146-1149], we show that a sudden turn-on of incoherent pumping can generate substantial Fano coherences among the excited states of retinal. These coherences are the most pronounced in the regime where the matrix elements of the transition dipole moment between the ground and excited eigenstates are parallel to one another. We show that even when the transition dipole moments are perpendicular (implying the absence of light-induced Fano coherence) a small amount of excited-state coherence is still generated due to the coupling to intramolecular vibrational modes and the protein environment, causing depopulation of the excited eigenstates. The overall effect of the coherences on the steady-state population and on the photoproduct quantum yield is shown to be small; however we observe a significant transient effect on the formation of the trans photoproduct, enhancing the photoreaction quantum yield by ∼11% at 200 fs. These calculations suggest that coupling to intramolecular vibrational modes and the protein environment play an important role in photoreaction dynamics, suppressing oscillations in the quantum yield associated with Fano interference.

Ptychographic imaging with partially coherent plasma EUV sources

NASA Astrophysics Data System (ADS)

Bußmann, Jan; Odstrčil, Michal; Teramoto, Yusuke; Juschkin, Larissa

2017-12-01

We report on high-resolution lens-less imaging experiments based on ptychographic scanning coherent diffractive imaging (CDI) method employing compact plasma sources developed for extreme ultraviolet (EUV) lithography applications. Two kinds of discharge sources were used in our experiments: a hollow-cathode-triggered pinch plasma source operated with oxygen and for the first time a laser-assisted discharge EUV source with a liquid tin target. Ptychographic reconstructions of different samples were achieved by applying constraint relaxation to the algorithm. Our ptychography algorithms can handle low spatial coherence and broadband illumination as well as compensate for the residual background due to plasma radiation in the visible spectral range. Image resolution down to 100 nm is demonstrated even for sparse objects, and it is limited presently by the sample structure contrast and the available coherent photon flux. We could extract material properties by the reconstruction of the complex exit-wave field, gaining additional information compared to electron microscopy or CDI with longer-wavelength high harmonic laser sources. Our results show that compact plasma-based EUV light sources of only partial spatial and temporal coherence can be effectively used for lens-less imaging applications. The reported methods may be applied in combination with reflectometry and scatterometry for high-resolution EUV metrology.

Analysis of complex samples using a portable multi-wavelength light emitting diode (LED) fluorescence spectrometer

USDA-ARS?s Scientific Manuscript database

Spectroscopic analysis of chemically complex samples often requires an increase n the dimensionality of the measured response surface. This often involves the measurement of emitted light intensities as functions of both wavelengths of excitation and emission resulting in the generation of an excita...

Device for wavelength-selective imaging

DOEpatents

Frangioni, John V.

2010-09-14

An imaging device captures both a visible light image and a diagnostic image, the diagnostic image corresponding to emissions from an imaging medium within the object. The visible light image (which may be color or grayscale) and the diagnostic image may be superimposed to display regions of diagnostic significance within a visible light image. A number of imaging media may be used according to an intended application for the imaging device, and an imaging medium may have wavelengths above, below, or within the visible light spectrum. The devices described herein may be advantageously packaged within a single integrated device or other solid state device, and/or employed in an integrated, single-camera medical imaging system, as well as many non-medical imaging systems that would benefit from simultaneous capture of visible-light wavelength images along with images at other wavelengths.

Optical sectioning in induced coherence tomography with frequency-entangled photons

NASA Astrophysics Data System (ADS)

Vallés, Adam; Jiménez, Gerard; Salazar-Serrano, Luis José; Torres, Juan P.

2018-02-01

We demonstrate a different scheme to perform optical sectioning of a sample based on the concept of induced coherence [Zou et al., Phys. Rev. Lett. 67, 318 (1991), 10.1103/PhysRevLett.67.318]. This can be viewed as a different type of optical coherence tomography scheme where the varying reflectivity of the sample along the direction of propagation of an optical beam translates into changes of the degree of first-order coherence between two beams. As a practical advantage the scheme allows probing the sample with one wavelength and measuring photons with another wavelength. In a bio-imaging scenario, this would result in a deeper penetration into the sample because of probing with longer wavelengths, while still using the optimum wavelength for detection. The scheme proposed here could achieve submicron axial resolution by making use of nonlinear parametric sources with broad spectral bandwidth emission.

Quantitative phase imaging of biological cells using spatially low and temporally high coherent light source.

PubMed

Ahmad, Azeem; Dubey, Vishesh; Singh, Gyanendra; Singh, Veena; Mehta, Dalip Singh

2016-04-01

In this Letter, we demonstrate quantitative phase imaging of biological samples, such as human red blood cells (RBCs) and onion cells using narrow temporal frequency and wide angular frequency spectrum light source. This type of light source was synthesized by the combined effect of spatial, angular, and temporal diversity of speckle reduction technique. The importance of using low spatial and high temporal coherence light source over the broad band and narrow band light source is that it does not require any dispersion compensation mechanism for biological samples. Further, it avoids the formation of speckle or spurious fringes which arises while using narrow band light source.

The X-ray Correlation Spectroscopy instrument at the Linac Coherent Light Source

PubMed Central

Alonso-Mori, Roberto; Caronna, Chiara; Chollet, Matthieu; Curtis, Robin; Damiani, Daniel S.; Defever, Jim; Feng, Yiping; Flath, Daniel L.; Glownia, James M.; Lee, Sooheyong; Lemke, Henrik T.; Nelson, Silke; Bong, Eric; Sikorski, Marcin; Song, Sanghoon; Srinivasan, Venkat; Stefanescu, Daniel; Zhu, Diling; Robert, Aymeric

2015-01-01

The X-ray Correlation Spectroscopy instrument is dedicated to the study of dynamics in condensed matter systems using the unique coherence properties of free-electron lasers. It covers a photon energy range of 4–25 keV. The intrinsic temporal characteristics of the Linac Coherent Light Source, in particular the 120 Hz repetition rate, allow for the investigation of slow dynamics (milli­seconds) by means of X-ray photon correlation spectroscopy. Double-pulse schemes could probe dynamics on the picosecond timescale. A description of the instrument capabilities and recent achievements is presented. PMID:25931061

Partially coherent polarized atmospheric transmission characteristics and application technology research

NASA Astrophysics Data System (ADS)

Fu, Qiang; Gao, Duorui; Liu, Zhi; Chen, Chunyi; Lou, Yan; Jiang, Huilin

2014-11-01

Based on partially coherent polarized light transmission characteristics of the atmosphere, an intensity expression of completely coherent flashing light is derived from Andrews scale modulation method. According to the generalized Huygens-Fresnel principle and Rytov theory, the phase fluctuation structure function is obtained on condition that the refractive index profile in the atmosphere meet Von Karman spectrum, then get the arrival Angle fluctuation variance. Through the RMS beam width of gaussian beams in turbulent atmosphere, deviation angle formula of fully coherent gaussian beams in turbulence atmosphere is attained, then get the RMS beam width of partially coherent and derivation angle expression of GSM beam in turbulent atmosphere. Combined with transmission properties of radial polarized laser beam, cross spectral density matrix of partially coherent radially polarized light can be gained by using generalized huygens-fresnel principle. And light intensity and polarization after transmission can be known according to the unity of coherence and polarization theory. On the basis of the analysis model and numerical simulation, the simulation results show that: the light spot caused by atmospheric turbulence of partially coherent polarization will be superior to completely polarized light.Taking advantage of this feature, designed a new wireless suppression technology of atmospheric turbulence, that is the optimization criterion of initial degree of coherent light beam. The optimal initial degree of coherent light beam will change along with the change of atmospheric turbulence conditions,make control the beam's initial degree of coherence to realize the initial degree of coherence of light beam in real time and dynamic control. A spatial phase screen before emission aperture of fully coherent light is to generate the partially coherent light, liquid crystal spatial light modulator is is a preferable way to realize the dynamic random phase. Finally look

SPECIAL ISSUE ON OPTICAL PROCESSING OF INFORMATION: Optical information processing with transformation of the spatial coherence of light

NASA Astrophysics Data System (ADS)

Bykovskii, Yurii A.; Markilov, A. A.; Rodin, V. G.; Starikov, S. N.

1995-10-01

A description is given of systems with spatially incoherent illumination, intended for spectral and correlation analysis, and for the recording of Fourier holograms. These systems make use of transformation of the degree of the spatial coherence of light. The results are given of the processing of images and signals, including those transmitted by a bundle of fibre-optic waveguides both as monochromatic light and as quasimonochromatic radiation from a cathode-ray tube. The feasibility of spatial frequency filtering and of correlation analysis of images with a bipolar impulse response is considered for systems with spatially incoherent illumination where these tasks are performed by double transformation of the spatial coherence of light. A description is given of experimental systems and the results of image processing are reported.

Circularly Polarized Light with Sense and Wavelengths To Regulate Azobenzene Supramolecular Chirality in Optofluidic Medium.

PubMed

Wang, Laibing; Yin, Lu; Zhang, Wei; Zhu, Xiulin; Fujiki, Michiya

2017-09-20

Circularly polarized light (CPL) as a massless physical force causes absolute asymmetric photosynthesis, photodestruction, and photoresolution. CPL handedness has long been believed to be the determining factor in the resulting product's chirality. However, product chirality as a function of the CPL handedness, irradiation wavelength, and irradiation time has not yet been studied systematically. Herein, we investigate this topic using achiral polymethacrylate carrying achiral azobenzene as micrometer-size aggregates in an optofluidic medium with a tuned refractive index. Azobenzene chirality with a high degree of dissymmetry ratio (±1.3 × 10 -2 at 313 nm) was generated, inverted, and switched in multiple cycles by irradiation with monochromatic incoherent CPL (313, 365, 405, and 436 nm) for 20 s using a weak incoherent light source (≈ 30 μW·cm -2 ). Moreover, the optical activity was retained for over 1 week in the dark. Photoinduced chirality was swapped by the irradiating wavelength, regardless of whether the CPL sense was the same. This scenario is similar to the so-called Cotton effect, which was first described in 1895. The tandem choice of both CPL sense and its wavelength was crucial for azobenzene chirality. Our experimental proof and theoretical simulation should provide new insight into the chirality of CPL-controlled molecules, supramolecules, and polymers.

Resonantly enhanced method for generation of tunable, coherent vacuum ultraviolet radiation

DOEpatents

Glownia, James H.; Sander, Robert K.

1985-01-01

Carbon Monoxide vapor is used to generate coherent, tunable vacuum ultraviolet radiation by third-harmonic generation using a single tunable dye laser. The presence of a nearby electronic level resonantly enhances the nonlinear susceptibility of this molecule allowing efficient generation of the vuv light at modest pump laser intensities, thereby reducing the importance of a six-photon multiple-photon ionization process which is also resonantly enhanced by the same electronic level but to higher order. By choosing the pump radiation wavelength to be of shorter wavelength than individual vibronic levels used to extend tunability stepwise from 154.4 to 124.6 nm, and the intensity to be low enough, multiple-photon ionization can be eliminated. Excitation spectra of the third-harmonic emission output exhibit shifts to shorter wavelength and broadening with increasing CO pressure due to phase matching effects. Increasing the carbon monoxide pressure, therefore, allows the substantial filling in of gaps arising from the stepwise tuning thereby providing almost continuous tunability over the quoted range of wavelength emitted.

Resonantly enhanced method for generation of tunable, coherent vacuum-ultraviolet radiation

DOEpatents

Glownia, J.H.; Sander, R.K.

1982-06-29

Carbon Monoxide vapor is used to generate coherent, tunable vacuum ultraviolet radiation by third-harmonic generation using a single tunable dye laser. The presence of a nearby electronic level resonantly enhances the nonlinear susceptibility of this molecule allowing efficient generation of the vuv light at modest pump laser intensities, thereby reducing the importance of a six-photon multiple-photon ionization process which is also resonantly enhanced by the same electronic level but no higher order. By choosing the pump radiation wavelength to be of shorter wavelength than individual vibronic levels used to extend tunability stepwise from 154.4 to 124.6 nm, and the intensity to be low enough, multiple-photon ionization can be eliminated. Excitation spectra of the third-harmonic emission output exhibit shifts to shorter wavelength and broadening with increasing CO pressure due to phase matching effects. Increasing the carbon monoxide pressure, therefore, allows the substantial filling in of gaps arising from the stepwise tuning thereby providing almost continuous tunability over the quoted range of wavelength emitted.

Speckle reduction in laser projection displays through angle and wavelength diversity.

PubMed

Tran, Trinh-Thi-Kim; Svensen, Øyvind; Chen, Xuyuan; Akram, Muhammad Nadeem

2016-02-20

Speckle is the main obstacle for the use of laser light sources in projection technology. This paper focuses on speckle suppression by the reduction of temporal coherence which is provided by the broadband laser light. The investigation of the effect of laser spectrum width and multiple lasers on speckle contrast is discussed. A broader spectrum width of the laser light is attained by the use of multiple semiconductor laser diodes of the broad area type. Measurements of speckle contrast with and without angle diversity are performed for two and four laser diodes. The measurement of speckle contrast for a single laser diode is also presented for comparison. The experimental results show that multiple laser diodes provide lower speckle contrast as compared to a single laser diode. In addition, it is also shown in this paper that the wavelength distribution of independent laser diodes has an effect on speckle contrast. Two different types of blue laser diodes, Nichia NUB802T and Nichia NUB801E, which have slightly different central wavelengths, were used for the measurements. Four laser diodes with a combination of two types of laser diodes offer better speckle contrast reduction than four laser diodes of the same type due to an effective broader spectrum. Additional speckle contrast reduction is achieved through the angle diversity by using a dynamic deformable mirror.

Coherent and dynamic beam splitting based on light storage in cold atoms

PubMed Central

Park, Kwang-Kyoon; Zhao, Tian-Ming; Lee, Jong-Chan; Chough, Young-Tak; Kim, Yoon-Ho

2016-01-01

We demonstrate a coherent and dynamic beam splitter based on light storage in cold atoms. An input weak laser pulse is first stored in a cold atom ensemble via electromagnetically-induced transparency (EIT). A set of counter-propagating control fields, applied at a later time, retrieves the stored pulse into two output spatial modes. The high visibility interference between the two output pulses clearly demonstrates that the beam splitting process is coherent. Furthermore, by manipulating the control lasers, it is possible to dynamically control the storage time, the power splitting ratio, the relative phase, and the optical frequencies of the output pulses. With further improvements, the active beam splitter demonstrated in this work might have applications in photonic photonic quantum information and in all-optical information processing. PMID:27677457

Dual-wavelength photothermal optical coherence tomography for blood oxygen saturation measurement

NASA Astrophysics Data System (ADS)

Yin, Biwei; Kuranov, Roman V.; McElroy, Austin B.; Milner, Thomas E.

2013-03-01

We report design and demonstration of a dual wavelength photothermal (DWP) optical coherence tomography (OCT) system for imaging of a phantom microvessel and measurement of hemoglobin oxygen saturation (SO2) level. The DWP-OCT system contains a swept-source (SS) two-beam phase-sensitive (PhS) OCT system (1060 nm) and two intensity modulated photothermal excitation lasers (770 nm and 800 nm). The PhS-OCT probe beam (1060 nm) and photothermal excitation beams are combined into one single-mode optical fiber. A galvanometer based two-dimensional achromatic scanning system is designed to provide 14 μm lateral resolution for the PhS-OCT probe beam (1060 nm) and 13 μm lateral resolution for photothermal excitation beams. DWP-OCT system's sensitivity is 102 dB, axial resolution is 13 μm in tissue and uses a real-time digital dispersion compensation algorithm. Noise floor for optical pathlength measurements is 300 pm in the signal frequency range (380-400 Hz) of photothermal modulation frequencies. Blood SO2 level is calculated from measured optical pathlength (op) signal in a 300 μm diameter microvessel phantom introduced by the two photothermal excitation beams. En-face and B-scan images of a phantom microvessel are recorded, and six blood samples' SO2 levels are measured using DWP-OCT and compared with values provided by a commercial blood oximeter. A mathematical model indicates thermal diffusion introduces a systematic artifact that over-estimates SO2 values and is consistent with measured data.

Wavelength-dependent in-vitro and in-vivo photodynamic effects after sensitization with 5-aminolevulinic acid induced protoporphyrin IX

NASA Astrophysics Data System (ADS)

Szeimies, Rolf-Markus; Abels, Christoph; Fritsch, Clemens; Steinbach, Pia; Baeumler, Wolfgang; Messmann, Helmut; Goetz, Alwin E.; Goerz, Guenter; Landthaler, Michael

1996-01-01

Photodynamic therapy (PDT) with topically applied 5-aminolevulinic acid (ALA) is of growing interest, in particular in dermatology. Due to the fact that PDT with intravenously administered Photofrin is the only clinically approved sensitizer so far and is performed at a wavelength of 630 nm, this wavelength is also used in most experimental and clinical trials with ALA. In this study influence of irradiation with coherent light from a tunable dye laser at different wavelengths ranging from 625 to 649 nm was investigated. In in vitro experiments HaCaT immortalized human keratinocytes were sensitized with 30 (mu) g/ml ALA for 24 hrs. By determination of cell viability with the MTT test, best cell-killing effects were observed following irradiation at 635 nm. In an in vivo setting using an amelanotic melanoma (A-Mel-3) grown subcutaneously in Syrian Golden hamsters, these results were confirmed: tumor growth determined by measuring tumor volume increase after 28 days was less pronounced in animals treated with 100 mg/kg ALA i.v. and irradiated 2.5 hrs. later at 635 nm, as compared to animals receiving an equal dose and irradiated at 630 nm. This observation in vitro is probably due to large amounts of photosensitizing protoporphyrin IX (PP) localized in cell membranes which is visualized by confocal laser scanning microscopy (CLSM) and determined by HPLC analysis. These results suggest that in ALA-PDT when a coherent light source is used probably better results are achieved irradiating at 635 nm.

Coherent scattering noise reduction method with wavelength diversity detection for holographic data storage system

NASA Astrophysics Data System (ADS)

Nakamura, Yusuke; Hoshizawa, Taku; Takashima, Yuzuru

2017-09-01

A new method, wavelength diversity detection (WDD), for improving signal quality is proposed and its effectiveness is numerically confirmed. We consider that WDD is especially effective for high-capacity systems having low hologram diffraction efficiencies. In such systems, the signal quality is primarily limited by coherent scattering noise; thus, effective improvement of the signal quality under a scattering-limited system is of great interest. WDD utilizes a new degree of freedom, the spectrum width, and scattering by molecules to improve the signal quality of the system. We found that WDD improves the quality by counterbalancing the degradation of the quality due to Bragg mismatch. With WDD, a higher-scattering-coefficient medium can improve the quality. The result provides an interesting insight into the requirements for material characteristics, especially for a large-M/# material. In general, a larger-M/# material contains more molecules; thus, the system is subject to more scattering, which actually improves the quality with WDD. We propose a pathway for a future holographic data storage system (HDSS) using WDD, which can record a larger amount of data than a conventional HDSS.

General Strategy for Broadband Coherent Perfect Absorption and Multi-wavelength All-optical Switching Based on Epsilon-Near-Zero Multilayer Films

PubMed Central

Kim, Tae Young; Badsha, Md. Alamgir; Yoon, Junho; Lee, Seon Young; Jun, Young Chul; Hwangbo, Chang Kwon

2016-01-01

We propose a general, easy-to-implement scheme for broadband coherent perfect absorption (CPA) using epsilon-near-zero (ENZ) multilayer films. Specifically, we employ indium tin oxide (ITO) as a tunable ENZ material, and theoretically investigate CPA in the near-infrared region. We first derive general CPA conditions using the scattering matrix and the admittance matching methods. Then, by combining these two methods, we extract analytic expressions for all relevant parameters for CPA. Based on this theoretical framework, we proceed to study ENZ CPA in a single layer ITO film and apply it to all-optical switching. Finally, using an ITO multilayer of different ENZ wavelengths, we implement broadband ENZ CPA structures and investigate multi-wavelength all-optical switching in the technologically important telecommunication window. In our design, the admittance matching diagram was employed to graphically extract not only the structural parameters (the film thicknesses and incident angles), but also the input beam parameters (the irradiance ratio and phase difference between two input beams). We find that the multi-wavelength all-optical switching in our broadband ENZ CPA system can be fully controlled by the phase difference between two input beams. The simple but general design principles and analyses in this work can be widely used in various thin-film devices. PMID:26965195

Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength.

PubMed

Wakui, Kentaro; Eto, Yujiro; Benichi, Hugo; Izumi, Shuro; Yanagida, Tetsufumi; Ema, Kazuhiro; Numata, Takayuki; Fukuda, Daiji; Takeoka, Masahiro; Sasaki, Masahide

2014-04-03

Broadband light sources play essential roles in diverse fields, such as high-capacity optical communications, optical coherence tomography, optical spectroscopy, and spectrograph calibration. Although a nonclassical state from spontaneous parametric down-conversion may serve as a quantum counterpart, its detection and characterization have been a challenging task. Here we demonstrate the direct detection of photon numbers of an ultrabroadband (110 nm FWHM) squeezed state in the telecom band centred at 1535 nm wavelength, using a superconducting transition-edge sensor. The observed photon-number distributions violate Klyshko's criterion for the nonclassicality. From the observed photon-number distribution, we evaluate the second- and third-order correlation functions, and characterize a multimode structure, which implies that several tens of orthonormal modes of squeezing exist in the single optical pulse. Our results and techniques open up a new possibility to generate and characterize frequency-multiplexed nonclassical light sources for quantum info-communications technology.

Optical coherence tomography angiography in age-related macular degeneration: The game changer.

PubMed

Lupidi, Marco; Cerquaglia, Alessio; Chhablani, Jay; Fiore, Tito; Singh, Sumit Randhir; Cardillo Piccolino, Felice; Corbucci, Roberta; Coscas, Florence; Coscas, Gabriel; Cagini, Carlo

2018-04-01

Optical coherence tomography angiography is one of the biggest advances in ophthalmic imaging. It enables a depth-resolved assessment of the retinal and choroidal blood flow, far exceeding the levels of detail commonly obtained with dye angiographies. One of the first applications of optical coherence tomography angiography was in detecting the presence of choroidal neovascularization in age-related macular degeneration and establishing its position in relation to the retinal pigmented epithelium and Bruch's membrane, and thereby classifying the CNV as type 1, type 2, type 3, or mixed lesions. Optical coherence tomography angiograms, due to the longer wavelength used by optical coherence tomography, showed a more distinct choroidal neovascularization vascular pattern than fluorescein angiography, since there is less suffering from light scattering or is less obscured by overlying subretinal hemorrhages or exudation. Qualitative and quantitative assessments of optical coherence tomography angiography findings in exudative and nonexudative age-related macular degeneration have been largely investigated within the past 3 years both in clinical and experimental settings. This review constitutes an up-to-date of all the potential applications of optical coherence tomography angiography in age-related macular degeneration in order to better understand how to translate its theoretical usefulness into the current clinical practice.

Coherent Pound-Drever-Hall technique for high resolution fiber optic strain sensor at very low light power

NASA Astrophysics Data System (ADS)

Wu, Mengxin; Liu, Qingwen; Chen, Jiageng; He, Zuyuan

2017-04-01

Pound-Drever-Hall (PDH) technique has been widely adopted for ultrahigh resolution fiber-optic sensors, but its performance degenerates seriously as the light power drops. To solve this problem, we developed a coherent PDH technique for weak optical signal detection, with which the signal-to-noise ratio (SNR) of demodulated PDH signal is dramatically improved. In the demonstrational experiments, a high resolution fiber-optic sensor using the proposed technique is realized, and n"-order strain resolution at a low light power down to -43 dBm is achieved, which is about 15 dB lower compared with classical PDH technique. The proposed coherent PDH technique has great potentials in longer distance and larger scale sensor networks.

Shock drive capabilities of a 30-Joule laser at the matter in extreme conditions hutch of the Linac Coherent Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Shaughnessy Brennan; Hashim, Akel; Gleason, Arianna

In this paper, we measure the shock drive capabilities of a 30 J, nanosecond, 527 nm laser system at the matter in extreme conditions hutch of the Linac Coherent Light Source. Using a velocity interferometer system for any reflector, we ascertain the maximum instantaneous ablation pressure and characterize its dependence on a drive laser spot size, spatial profile, and temporal profile. We also examine the effects of these parameters on shock spatial and temporal uniformity. Our analysis shows the drive laser capable of generating instantaneous ablation pressures exceeding 160 GPa while maintaining a 1D shock profile. We find that slopemore » pulses provide higher instantaneous ablation pressures than plateau pulses. Our results show instantaneous ablation pressures comparable to those measured at the Omega Laser Facility in Rochester, NY under similar optical drive parameters. In conclusion, we analyze how optical laser ablation pressures are compare with known scaling relations, accounting for variable laser wavelengths.« less

Shock drive capabilities of a 30-Joule laser at the matter in extreme conditions hutch of the Linac Coherent Light Source

DOE PAGES

Brown, Shaughnessy Brennan; Hashim, Akel; Gleason, Arianna; ...

2017-10-23

In this paper, we measure the shock drive capabilities of a 30 J, nanosecond, 527 nm laser system at the matter in extreme conditions hutch of the Linac Coherent Light Source. Using a velocity interferometer system for any reflector, we ascertain the maximum instantaneous ablation pressure and characterize its dependence on a drive laser spot size, spatial profile, and temporal profile. We also examine the effects of these parameters on shock spatial and temporal uniformity. Our analysis shows the drive laser capable of generating instantaneous ablation pressures exceeding 160 GPa while maintaining a 1D shock profile. We find that slopemore » pulses provide higher instantaneous ablation pressures than plateau pulses. Our results show instantaneous ablation pressures comparable to those measured at the Omega Laser Facility in Rochester, NY under similar optical drive parameters. In conclusion, we analyze how optical laser ablation pressures are compare with known scaling relations, accounting for variable laser wavelengths.« less

When holography meets coherent diffraction imaging.

PubMed

Latychevskaia, Tatiana; Longchamp, Jean-Nicolas; Fink, Hans-Werner

2012-12-17

The phase problem is inherent to crystallographic, astronomical and optical imaging where only the intensity of the scattered signal is detected and the phase information is lost and must somehow be recovered to reconstruct the object's structure. Modern imaging techniques at the molecular scale rely on utilizing novel coherent light sources like X-ray free electron lasers for the ultimate goal of visualizing such objects as individual biomolecules rather than crystals. Here, unlike in the case of crystals where structures can be solved by model building and phase refinement, the phase distribution of the wave scattered by an individual molecule must directly be recovered. There are two well-known solutions to the phase problem: holography and coherent diffraction imaging (CDI). Both techniques have their pros and cons. In holography, the reconstruction of the scattered complex-valued object wave is directly provided by a well-defined reference wave that must cover the entire detector area which often is an experimental challenge. CDI provides the highest possible, only wavelength limited, resolution, but the phase recovery is an iterative process which requires some pre-defined information about the object and whose outcome is not always uniquely-defined. Moreover, the diffraction patterns must be recorded under oversampling conditions, a pre-requisite to be able to solve the phase problem. Here, we report how holography and CDI can be merged into one superior technique: holographic coherent diffraction imaging (HCDI). An inline hologram can be recorded by employing a modified CDI experimental scheme. We demonstrate that the amplitude of the Fourier transform of an inline hologram is related to the complex-valued visibility, thus providing information on both, the amplitude and the phase of the scattered wave in the plane of the diffraction pattern. With the phase information available, the condition of oversampling the diffraction patterns can be relaxed, and the

Visible light optical coherence microscopy imaging of the mouse cortex with femtoliter volume resolution

NASA Astrophysics Data System (ADS)

Merkle, Conrad W.; Chong, Shau Poh; Kho, Aaron M.; Zhu, Jun; Kholiqov, Oybek; Dubra, Alfredo; Srinivasan, Vivek J.

2018-02-01

Most flying-spot Optical Coherence Tomography (OCT) and Optical Coherence Microscopy (OCM) systems use a symmetric confocal geometry, where the detection path retraces the illumination path starting from and ending with the spatial mode of a single mode optical fiber. Here, we describe a visible light OCM instrument that breaks this symmetry to improve transverse resolution without sacrificing collection efficiency in scattering tissue. This was achieved by overfilling a 0.3 numerical aperture (NA) water immersion objective on the illumination path, while maintaining a conventional Gaussian mode detection path (1/e2 intensity diameter 0.82 Airy disks), enabling 1.1 μm full-width at half-maximum (FWHM) transverse resolution. At the same time, a 0.9 μm FWHM axial resolution in tissue, achieved by a broadband visible light source, enabled femtoliter volume resolution. We characterized this instrument according to paraxial coherent microscopy theory, and then used it to image the meningeal layers, intravascular red blood cell-free layer, and myelinated axons in the mouse neocortex in vivo through the thinned skull. Finally, by introducing a 0.8 NA water immersion objective, we improved the lateral resolution to 0.44 μm FWHM, which provided a volumetric resolution of 0.2 fL, revealing cell bodies in cortical layer I of the mouse brain with OCM for the first time.

Coherent Light induced in Optical Fiber by a Charged Particle

NASA Astrophysics Data System (ADS)

Artru, Xavier; Ray, Cédric

2016-07-01

Coherent light production in an optical fiber by a charged particle (named PIGL, for particle-induced guided, light) is reviewed. From the microscopic point of view, light is emitted by transient electric dipoles induced in the fiber medium by the Coulomb field of the particle. The phenomenon can also considered as the capture of virtual photons of the particle field by the fiber. Two types of captures are distinguished. Type-I takes place in a uniform part of the fiber; then the photon keeps its longitudinal momentum pz . Type-II takes place near an end or in a non-uniform part of the fiber; then pz is not conserved. Type-I PIGL is not affected by background lights external to the fiber. At grazing incidence it becomes nearly monochromatic. Its circular polarization depends on the angular momentum of the particle about the fiber and on the relative velocity between the particle and the guided wave. A general formula for the yield of Type-II radiation, based on the reciprocity theorem, is proposed. This radiation can be assisted by metallic objects stuck to the fiber, via plasmon excitation. A periodic structure leads to a guided Smith-Purcell radiation. Applications of PIGL in beam diagnostics are considered.

A cost analysis of microalgal biomass and biodiesel production in open raceways treating municipal wastewater and under optimum light wavelength.

PubMed

Kang, Zion; Kim, Byung-Hyuk; Ramanan, Rishiram; Choi, Jong-Eun; Yang, Ji-Won; Oh, Hee-Mock; Kim, Hee-Sik

2015-01-01

Open raceway ponds are cost-efficient for mass cultivation of microalgae compared with photobioreactors. Although low-cost options like wastewater as nutrient source is studied to overcome the commercialization threshold for biodiesel production from microalgae, a cost analysis on the use of wastewater and other incremental increases in productivity has not been elucidated. We determined the effect of using wastewater and wavelength filters on microalgal productivity. Experimental results were then fitted into a model, and cost analysis was performed in comparison with control raceways. Three different microalgal strains, Chlorella vulgaris AG10032, Chlorella sp. JK2, and Scenedesmus sp. JK10, were tested for nutrient removal under different light wavelengths (blue, green, red, and white) using filters in batch cultivation. Blue wavelength showed an average of 27% higher nutrient removal and at least 42% higher chemical oxygen demand removal compared with white light. Naturally, the specific growth rate of microalgae cultivated under blue wavelength was on average 10.8% higher than white wavelength. Similarly, lipid productivity was highest in blue wavelength, at least 46.8% higher than white wavelength, whereas FAME composition revealed a mild increase in oleic and palmitic acid levels. Cost analysis reveals that raceways treating wastewater and using monochromatic wavelength would decrease costs from 2.71 to 0.73 $/kg biomass. We prove that increasing both biomass and lipid productivity is possible through cost-effective approaches, thereby accelerating the commercialization of low-value products from microalgae, like biodiesel.

Linac coherent light source (LCLS) undulator RF BPM system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lill, R.; Waldschmidt, G.; Morrison, L.

2006-01-01

The Linac Coherent Light Source (LCLS) will be the world's first x-ray free-electron laser (FEL) when it becomes operational in 2009. The LCLS is currently in the construction phase. The beam position monitor (BPM) system planned for the LCLS undulator will incorporate a high-resolution X-band cavity BPM system described in this paper. The BPM system will provide high-resolution measurements of the electron beam trajectory on a pulse-to-pulse basis and over many shots. The X-band cavity BPM size, simple fabrication, and high resolution make it an ideal choice for LCLS beam position detection. We will discuss the system specifications, design, andmore » prototype test results.« less

Tunable optical coherence tomography in the infrared range using visible photons

NASA Astrophysics Data System (ADS)

Paterova, Anna V.; Yang, Hongzhi; An, Chengwu; Kalashnikov, Dmitry A.; Krivitsky, Leonid A.

2018-04-01

Optical coherence tomography (OCT) is an appealing technique for bio-imaging, medicine, and material analysis. For many applications, OCT in mid- and far-infrared (IR) leads to significantly more accurate results. Reported mid-IR OCT systems require light sources and photodetectors which operate in mid-IR range. These devices are expensive and need cryogenic cooling. Here, we report a proof-of-concept demonstration of a wavelength tunable IR OCT technique with detection of only visible range photons. Our method is based on the nonlinear interference of frequency correlated photon pairs. The nonlinear crystal, introduced in the Michelson-type interferometer, generates photon pairs with one photon in the visible and another in the IR range. The intensity of detected visible photons depends on the phase and loss of IR photons, which interact with the sample under study. This enables us to characterize sample properties and perform imaging in the IR range by detecting visible photons. The technique possesses broad wavelength tunability and yields a fair axial and lateral resolution, which can be tailored to the specific application. The work contributes to the development of versatile 3D imaging and material characterization systems working in a broad range of IR wavelengths, which do not require the use of IR-range light sources and photodetectors.

Detecting apoptosis using dynamic light scattering with optical coherence tomography

NASA Astrophysics Data System (ADS)

Farhat, Golnaz; Mariampillai, Adrian; Yang, Victor X. D.; Czarnota, Gregory J.; Kolios, Michael C.

2011-07-01

A dynamic light scattering technique is implemented using optical coherence tomography (OCT) to measure the change in intracellular motion as cells undergo apoptosis. Acute myeloid leukemia cells were treated with cisplatin and imaged at a frame rate of 166 Hz using a 1300 nm swept-source OCT system at various times over a period of 48 h. Time correlation analysis of the speckle intensities indicated a significant increase in intracellular motion 24 h after treatment. This rise in intracellular motion correlated with histological findings of irregularly shaped and fragmented cells indicative of cell membrane blebbing and fragmentation.

Dynamic coherent backscattering mirror

NASA Astrophysics Data System (ADS)

Zeylikovich, I.; Xu, M.

2016-02-01

The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.

Structured light generation by magnetic metamaterial half-wave plates at visible wavelength

NASA Astrophysics Data System (ADS)

Zeng, Jinwei; Luk, Ting S.; Gao, Jie; Yang, Xiaodong

2017-12-01

Metamaterial or metasurface unit cells functioning as half-wave plates play an essential role for realizing ideal Pancharatnam-Berry phase optical elements capable of tailoring light phase and polarization as desired. Complex light beam manipulation through these metamaterials or metasurfaces unveils new dimensions of light-matter interactions for many advances in diffraction engineering, beam shaping, structuring light, and holography. However, the realization of metamaterial or metasurface half-wave plates in visible spectrum range is still challenging mainly due to its specific requirements of strong phase anisotropy with amplitude isotropy in subwavelength scale. Here, we propose magnetic metamaterial structures which can simultaneously exploit the electric field and magnetic field of light for achieving the nanoscale half-wave plates at visible wavelength. We design and demonstrate the magnetic metamaterial half-wave plates in linear grating patterns with high polarization conversion purity in a deep subwavelength thickness. Then, we characterize the equivalent magnetic metamaterial half-wave plates in cylindrical coordinate as concentric-ring grating patterns, which act like an azimuthal half-wave plate and accordingly exhibit spatially inhomogeneous polarization and phase manipulations including spin-to-orbital angular momentum conversion and vector beam generation. Our results show potentials for realizing on-chip beam converters, compact holograms, and many other metamaterial devices for structured light beam generation, polarization control, and wavefront manipulation.

Long-lived coherence in carotenoids

NASA Astrophysics Data System (ADS)

Davis, J. A.; Cannon, E.; Van Dao, L.; Hannaford, P.; Quiney, H. M.; Nugent, K. A.

2010-08-01

We use two-colour vibronic coherence spectroscopy to observe long-lived vibrational coherences in the ground electronic state of carotenoid molecules, with decoherence times in excess of 1 ps. Lycopene and spheroidene were studied isolated in solution, and within the LH2 light-harvesting complex extracted from purple bacteria. The vibrational coherence time is shown to increase significantly for the carotenoid in the complex, providing further support to previous assertions that long-lived electronic coherences in light-harvesting complexes are facilitated by in-phase motion of the chromophores and surrounding proteins. Using this technique, we are also able to follow the evolution of excited state coherences and find that for carotenoids in the light-harvesting complex the langS2|S0rang superposition remains coherent for more than 70 fs. In addition to the implications of this long electronic decoherence time, the extended coherence allows us to observe the evolution of the excited state wavepacket. These experiments reveal an enhancement of the vibronic coupling to the first vibrational level of the C-C stretching mode and/or methyl-rocking mode in the ground electronic state 70 fs after the initial excitation. These observations open the door to future experiments and modelling that may be able to resolve the relaxation dynamics of carotenoids in solution and in natural light-harvesting systems.

Light sources based on semiconductor current filaments

DOEpatents

Zutavern, Fred J.; Loubriel, Guillermo M.; Buttram, Malcolm T.; Mar, Alan; Helgeson, Wesley D.; O'Malley, Martin W.; Hjalmarson, Harold P.; Baca, Albert G.; Chow, Weng W.; Vawter, G. Allen

2003-01-01

The present invention provides a new type of semiconductor light source that can produce a high peak power output and is not injection, e-beam, or optically pumped. The present invention is capable of producing high quality coherent or incoherent optical emission. The present invention is based on current filaments, unlike conventional semiconductor lasers that are based on p-n junctions. The present invention provides a light source formed by an electron-hole plasma inside a current filament. The electron-hole plasma can be several hundred microns in diameter and several centimeters long. A current filament can be initiated optically or with an e-beam, but can be pumped electrically across a large insulating region. A current filament can be produced in high gain photoconductive semiconductor switches. The light source provided by the present invention has a potentially large volume and therefore a potentially large energy per pulse or peak power available from a single (coherent) semiconductor laser. Like other semiconductor lasers, these light sources will emit radiation at the wavelength near the bandgap energy (for GaAs 875 nm or near infra red). Immediate potential applications of the present invention include high energy, short pulse, compact, low cost lasers and other incoherent light sources.

Light at night acutely impairs glucose tolerance in a time-, intensity- and wavelength-dependent manner in rats.

PubMed

Opperhuizen, Anne-Loes; Stenvers, Dirk J; Jansen, Remi D; Foppen, Ewout; Fliers, Eric; Kalsbeek, Andries

2017-07-01

Exposure to light at night (LAN) has increased dramatically in recent decades. Animal studies have shown that chronic dim LAN induced obesity and glucose intolerance. Furthermore, several studies in humans have demonstrated that chronic exposure to artificial LAN may have adverse health effects with an increased risk of metabolic disorders, including type 2 diabetes. It is well-known that acute exposure to LAN affects biological clock function, hormone secretion and the activity of the autonomic nervous system, but data on the effects of LAN on glucose homeostasis are lacking. This study aimed to investigate the acute effects of LAN on glucose metabolism. Male Wistar rats were subjected to i.v. glucose or insulin tolerance tests while exposed to 2 h of LAN in the early or late dark phase. In subsequent experiments, different light intensities and wavelengths were used. LAN exposure early in the dark phase at ZT15 caused increased glucose responses during the first 20 min after glucose infusion (p < 0.001), whereas LAN exposure at the end of the dark phase, at ZT21, caused increased insulin responses during the first 10 min (p < 0.01), indicating that LAN immediately induces glucose intolerance in rats. Subsequent experiments demonstrated that the effect of LAN was both intensity- and wavelength-dependent. White light of 50 and 150 lx induced greater glucose responses than 5 and 20 lx, whereas all intensities other than 5 lx reduced locomotor activity. Green light induced glucose intolerance, but red and blue light did not, suggesting the involvement of a specific retina-brain pathway. Together, these data show that exposure to LAN has acute adverse effects on glucose metabolism in a time-, intensity- and wavelength-dependent manner.

Algorithm for protecting light-trees in survivable mesh wavelength-division-multiplexing networks

NASA Astrophysics Data System (ADS)

Luo, Hongbin; Li, Lemin; Yu, Hongfang

2006-12-01

Wavelength-division-multiplexing (WDM) technology is expected to facilitate bandwidth-intensive multicast applications such as high-definition television. A single fiber cut in a WDM mesh network, however, can disrupt the dissemination of information to several destinations on a light-tree based multicast session. Thus it is imperative to protect multicast sessions by reserving redundant resources. We propose a novel and efficient algorithm for protecting light-trees in survivable WDM mesh networks. The algorithm is called segment-based protection with sister node first (SSNF), whose basic idea is to protect a light-tree using a set of backup segments with a higher priority to protect the segments from a branch point to its children (sister nodes). The SSNF algorithm differs from the segment protection scheme proposed in the literature in how the segments are identified and protected. Our objective is to minimize the network resources used for protecting each primary light-tree such that the blocking probability can be minimized. To verify the effectiveness of the SSNF algorithm, we conduct extensive simulation experiments. The simulation results demonstrate that the SSNF algorithm outperforms existing algorithms for the same problem.

Coherent perfect absorbers: linear control of light with light

NASA Astrophysics Data System (ADS)

Baranov, Denis G.; Krasnok, Alex; Shegai, Timur; Alù, Andrea; Chong, Yidong

2017-12-01

The absorption of electromagnetic energy by a material is a phenomenon that underlies many applications, including molecular sensing, photocurrent generation and photodetection. Typically, the incident energy is delivered to the system through a single channel, for example, by a plane wave incident on one side of an absorber. However, absorption can be made much more efficient by exploiting wave interference. A coherent perfect absorber is a system in which the complete absorption of electromagnetic radiation is achieved by controlling the interference of multiple incident waves. Here, we review recent advances in the design and applications of such devices. We present the theoretical principles underlying the phenomenon of coherent perfect absorption and give an overview of the photonic structures in which it can be realized, including planar and guided-mode structures, graphene-based systems, parity-symmetric and time-symmetric structures, 3D structures and quantum-mechanical systems. We then discuss possible applications of coherent perfect absorption in nanophotonics, and, finally, we survey the perspectives for the future of this field.

Wide tuning range wavelength-swept laser with a single SOA at 1020 nm for ultrahigh resolution Fourier-domain optical coherence tomography.

PubMed

Lee, Sang-Won; Song, Hyun-Woo; Jung, Moon-Youn; Kim, Seung-Hwan

2011-10-24

In this study, we demonstrated a wide tuning range wavelength-swept laser with a single semiconductor optical amplifier (SOA) at 1020 nm for ultrahigh resolution, Fourier-domain optical coherence tomography (UHR, FD-OCT). The wavelength-swept laser was constructed with an external line-cavity based on a Littman configuration. An optical wavelength selection filter consisted of a grating, a telescope, and a polygon scanner. Before constructing the optical wavelength selection filter, we observed that the optical power, the spectrum bandwidth, and the center wavelength of the SOA were affected by the temperature of the thermoelectric (TE) cooler in the SOA mount as well as the applied current. Therefore, to obtain a wide wavelength tuning range, we adjusted the temperature of the TE cooler in the SOA mount. When the temperature in the TE cooler was 9 °C, our swept source had a tuning range of 142 nm and a full-width at half-maximum (FWHM) of 121.5 nm at 18 kHz. The measured instantaneous spectral bandwidth (δλ) is 0.085 nm, which was measured by an optical spectrum analyzer with a resolution bandwidth of 0.06 nm. This value corresponds to an imaging depth of 3.1 mm in air. Additionally, the averaged optical power of our swept source was 8.2 mW. In UHR, FD/SS-OCT using our swept laser, the measured axial resolution was 4.0 μm in air corresponding to 2.9 μm in tissue (n = 1.35). The sensitivity was measured to be 93.1 dB at a depth of 100 μm. Finally, we obtained retinal images (macular and optic disk) and a corneal image. © 2011 Optical Society of America

Coherent backscattering of light by complex random media of spherical scatterers: numerical solution

NASA Astrophysics Data System (ADS)

Muinonen, Karri

2004-07-01

Novel Monte Carlo techniques are described for the computation of reflection coefficient matrices for multiple scattering of light in plane-parallel random media of spherical scatterers. The present multiple scattering theory is composed of coherent backscattering and radiative transfer. In the radiative transfer part, the Stokes parameters of light escaping from the medium are updated at each scattering process in predefined angles of emergence. The scattering directions at each process are randomized using probability densities for the polar and azimuthal scattering angles: the former angle is generated using the single-scattering phase function, whereafter the latter follows from Kepler's equation. For spherical scatterers in the Rayleigh regime, randomization proceeds semi-analytically whereas, beyond that regime, cubic spline presentation of the scattering matrix is used for numerical computations. In the coherent backscattering part, the reciprocity of electromagnetic waves in the backscattering direction allows the renormalization of the reversely propagating waves, whereafter the scattering characteristics are computed in other directions. High orders of scattering (~10 000) can be treated because of the peculiar polarization characteristics of the reverse wave: after a number of scatterings, the polarization state of the reverse wave becomes independent of that of the incident wave, that is, it becomes fully dictated by the scatterings at the end of the reverse path. The coherent backscattering part depends on the single-scattering albedo in a non-monotonous way, the most pronounced signatures showing up for absorbing scatterers. The numerical results compare favourably to the literature results for nonabsorbing spherical scatterers both in and beyond the Rayleigh regime.

Coherent radiation of relativistic electrons in dielectric fibers in the millimeter wavelength range

NASA Astrophysics Data System (ADS)

Naumenko, G. A.; Potylitsyn, A. P.; Bleko, V. V.; Soboleva, V. V.

2015-02-01

The generation of visible light by a relativistic electron beam in dielectric fibers was considered in X. Artru and C. Ray, Nucl. Inst. Meth. B 309, 4 (2013), where the characteristics of radiation induced in a fiber by the electromagnetic field of a relativistic charged particle were studied and it was emphasized that they differ from those in the traditional mechanisms of radiation such as transition and diffraction. We have experimentally studied the characteristics of such a radiation in the millimeter wavelength range. It has been shown that radiation can be generated through different mechanisms depending on the geometry of the position of a fiber with respect to the trajectory of the charged particle. Fibers have been shown to be promising for nondestructive diagnostics of accelerator beams.

Effects of melatonin injection or green-wavelength LED light on the antioxidant system in goldfish (Carassius auratus) during thermal stress.

PubMed

Jung, Seo Jin; Choi, Young Jae; Kim, Na Na; Choi, Ji Yong; Kim, Bong-Seok; Choi, Cheol Young

2016-05-01

We tested the mitigating effects of melatonin injections or irradiation from green-wavelength light-emitting diodes (LEDs) on goldfish (Carassius auratus) exposed to thermal stress (high water temperature, 30 °C). The effects of the two treatments were assessed by measuring the expression and activity levels of the antioxidant enzymes, superoxide dismutase and catalase, plasma hydrogen peroxide, lipid hydroperoxide, and lysozyme. In addition, a comet assay was conducted to confirm that high water temperature damaged nuclear DNA. The expression and activity of the antioxidant enzymes, plasma hydrogen peroxide, and lipid hydroperoxide were significantly higher after exposure to high temperature and were significantly lower in fish that received melatonin or LED light than in those that received no mitigating treatment. Plasma lysozyme was significantly lower after exposure to high temperature and was significantly higher after exposure to melatonin or LED light. The comet assay revealed that thermal stress caused a great deal of damage to nuclear DNA; however, treatment with melatonin or green-wavelength LED light prevented a significant portion of this damage from occurring. These results indicate that, although high temperatures induce oxidative stress and reduce immune system strength in goldfish, both melatonin and green-wavelength LED light inhibit oxidative stress and boost the immune system. LED treatment increased the antioxidant and immune system activity more significantly than did melatonin treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Functional Optical Coherence Tomography: Principles and Progress

PubMed Central

Kim, Jina; Brown, William; Maher, Jason R.; Levinson, Howard; Wax, Adam

2015-01-01

In the past decade, several functional extensions of optical coherence tomography (OCT) have emerged, and this review highlights key advances in instrumentation, theoretical analysis, signal processing and clinical application of these extensions. We review five principal extensions: Doppler OCT (DOCT), polarization-sensitive OCT (PS-OCT), optical coherence elastography (OCE), spectroscopic OCT (SOCT), and molecular imaging OCT. The former three have been further developed with studies in both ex vivo and in vivo human tissues. This review emphasizes the newer techniques of SOCT and molecular imaging OCT, which show excellent potential for clinical application but have yet to be well reviewed in the literature. SOCT elucidates tissue characteristics, such as oxygenation and carcinogenesis, by detecting wavelength-dependent absorption and scattering of light in tissues. While SOCT measures endogenous biochemical distributions, molecular imaging OCT detects exogenous molecular contrast agents. These newer advances in functional OCT broaden the potential clinical application of OCT by providing novel ways to understand tissue activity that cannot be accomplished by other current imaging methodologies. PMID:25951836

Multiple wavelength spectral system simulating background light noise environment in satellite laser communications

NASA Astrophysics Data System (ADS)

Lu, Wei; Sun, Jianfeng; Hou, Peipei; Xu, Qian; Xi, Yueli; Zhou, Yu; Zhu, Funan; Liu, Liren

2017-08-01

Performance of satellite laser communications between GEO and LEO satellites can be influenced by background light noise appeared in the field of view due to sunlight or planets and some comets. Such influences should be studied on the ground testing platform before the space application. In this paper, we introduce a simulator that can simulate the real case of background light noise in space environment during the data talking via laser beam between two lonely satellites. This simulator can not only simulate the effect of multi-wavelength spectrum, but also the effects of adjustable angles of field-of-view, large range of adjustable optical power and adjustable deflection speeds of light noise in space environment. We integrate these functions into a device with small and compact size for easily mobile use. Software control function is also achieved via personal computer to adjust these functions arbitrarily. Keywords:

Interplay of coherent and dissipative dynamics in condensates of light

NASA Astrophysics Data System (ADS)

Radonjić, Milan; Kopylov, Wassilij; Balaž, Antun; Pelster, Axel

2018-05-01

Based on the Lindblad master equation approach we obtain a detailed microscopic model of photons in a dye-filled cavity, which features condensation of light. To this end we generalise a recent non-equilibrium approach of Kirton and Keeling such that the dye-mediated contribution to the photon–photon interaction in the light condensate is accessible due to an interplay of coherent and dissipative dynamics. We describe the steady-state properties of the system by analysing the resulting equations of motion of both photonic and matter degrees of freedom. In particular, we discuss the existence of two limiting cases for steady states: photon Bose–Einstein condensate and laser-like. In the former case, we determine the corresponding dimensionless photon–photon interaction strength by relying on realistic experimental data and find a good agreement with previous theoretical estimates. Furthermore, we investigate how the dimensionless interaction strength depends on the respective system parameters. This paper is dedicated to the memory of Tobias Brandes

The Linac Coherent Light Source: Recent Developments and Future Plans

DOE PAGES

Schoenlein, R. W.; Boutet, S.; Minitti, M. P.; ...

2017-08-18

The development of X-ray free-electron lasers (XFELs) has launched a new era in X-ray science by providing ultrafast coherent X-ray pulses with a peak brightness that is approximately one billion times higher than previous X-ray sources. The Linac Coherent Light Source (LCLS) facility at the SLAC National Accelerator Laboratory, the world’s first hard X-ray FEL, has already demonstrated a tremendous scientific impact across broad areas of science. Here in this paper, a few of the more recent representative highlights from LCLS are presented in the areas of atomic, molecular, and optical science; chemistry; condensed matter physics; matter in extreme conditions;more » and biology. This paper also outlines the near term upgrade (LCLS-II) and motivating science opportunities for ultrafast X-rays in the 0.25–5 keV range at repetition rates up to 1 MHz. Future plans to extend the X-ray energy reach to beyond 13 keV (<1 Å) at high repetition rate (LCLS-II-HE) are envisioned, motivated by compelling new science of structural dynamics at the atomic scale.« less

Mapping the opacity of paint layers in paintings with coloured grounds using optical coherence tomography

NASA Astrophysics Data System (ADS)

Liu, Ping; Hall-Aquitania, Moorea; Hermens, Erma; Groves, Roger M.

2017-07-01

Optical diagnostics techniques are becoming important for technical art history (TAH) as well as for heritage conservation. In recent years, optical coherence tomography (OCT) has been increasingly used as a novel technique for the inspection of artwork, revealing the stratigraphy of paintings. It has also shown to be an effective tool for vanish layer inspection. OCT is a contactless and non-destructive technique for microstructural imaging of turbid media, originally developed for medical applications. However current OCT instruments have difficulty in paint layer inspection due to the opacity of most pigments. This paper explores the potential of OCT for the investigation of paintings with coloured grounds. Depth scans were processed to determine the light penetration depth at the optical wavelength based on a 1/e light attenuation calculation. The variation in paint opacity was mapped based on the microstructural images and 3D penetration depth profiles was calculated and related back to the construction of the artwork. By determining the light penetration depth over a range of wavelengths the 3D depth perception of a painting with coloured grounds can be characterized optically.

Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength

PubMed Central

Wakui, Kentaro; Eto, Yujiro; Benichi, Hugo; Izumi, Shuro; Yanagida, Tetsufumi; Ema, Kazuhiro; Numata, Takayuki; Fukuda, Daiji; Takeoka, Masahiro; Sasaki, Masahide

2014-01-01

Broadband light sources play essential roles in diverse fields, such as high-capacity optical communications, optical coherence tomography, optical spectroscopy, and spectrograph calibration. Although a nonclassical state from spontaneous parametric down-conversion may serve as a quantum counterpart, its detection and characterization have been a challenging task. Here we demonstrate the direct detection of photon numbers of an ultrabroadband (110 nm FWHM) squeezed state in the telecom band centred at 1535 nm wavelength, using a superconducting transition-edge sensor. The observed photon-number distributions violate Klyshko's criterion for the nonclassicality. From the observed photon-number distribution, we evaluate the second- and third-order correlation functions, and characterize a multimode structure, which implies that several tens of orthonormal modes of squeezing exist in the single optical pulse. Our results and techniques open up a new possibility to generate and characterize frequency-multiplexed nonclassical light sources for quantum info-communications technology. PMID:24694515

Industrial integration of high coherence tunable VECSEL in the NIR and MIR

NASA Astrophysics Data System (ADS)

Denet, Stéphane; Chomet, Baptiste; Lecocq, Vincent; Ferrières, Laurence; Myara, Mikhaël.; Cerutti, Laurent; Sagnes, Isabelle; Garnache, Arnaud

2016-03-01

Laser technology is finding applications in areas such as high resolution spectroscopy, radar-lidar, velocimetry, or atomic clock where highly coherent tunable high power light sources are required. The Vertical External Cavity Surface Emitting Laser (VECSEL) technology [1] has been identified for years as a good candidate to reach high power, high coherence and broad tunability while covering a wide emission wavelength range exploiting III-V semiconductor technologies. Offering such performances in the Near- and Middle-IR range, GaAs- and Sb-based VECSEL technologies seem to be a well suited path to meet the required specifications of demanding applications. Built up in this field, our expertise allows the realization of compact and low power consumption marketable products, with performances that do not exist on the market today in the 0.8- 1.1 μm and 2-2.5 μm spectral range. Here we demonstrate highly coherent broadly tunable single frequency micro-chip, intracavity element free, patented VECSEL technology, integrated into a compact module with driving electronics. VECSEL devices emitting in the Near and Middle-IR developed in the frame of this work [2] exhibit exciting features compared to diode-pumped solid-state lasers and DFB diode lasers; they combine high power (>100mW) high coherence with a low divergence diffraction limited TEM00 beam, class A dynamics with Relative Intensity Noise as low as -140dB/Hz and at shot noise level above 200MHz RF frequency (up to 160GHz), free running narrow linewidth at sub MHz level (fundamental limit at Hz level) with high spectral purity (SMSR >55dB), linear polarization (50dB suppression ratio), and broadband continuous tunability greater than 400GHz (< 30V piezo voltage, 6kHz cut off frequency) with total tunability up to 3THz. Those performances can all be reached thanks to the high finesse cavity of VECSEL technology, associated to ideal homogeneous QW gain behaviour [3]. In addition, the compact design without any

GHRS Cycle 5 Echelle Wavelength Monitor

NASA Astrophysics Data System (ADS)

Soderblom, David

1995-07-01

This proposal defines the spectral lamp test for Echelle A. It is an internal test which makes measurements of the wavelength lamp SC2. It calibrates the carrousel function, Y deflections, resolving power, sensitivity, and scattered light. The wavelength calibration dispersion constants will be updated in the PODPS calibration data base. This proposal defines the spectral lamp test for Echelle B. It is an internal test which makes measurements of the wavelength lamp SC2. It calibrates the carrousel function, Y deflections, resolving power, sensitivity, and scattered light. The wavelength calibration dispersion constants will be updated in the PODPS calibration data base. It will be run every 4 months. The wavelengths may be out of range according to PEPSI or TRANS. Please ignore the errors.

FRET-Mediated Long-Range Wavelength Transformation by Photoconvertible Fluorescent Proteins as an Efficient Mechanism to Generate Orange-Red Light in Symbiotic Deep Water Corals.

PubMed

Bollati, Elena; Plimmer, Daniel; D'Angelo, Cecilia; Wiedenmann, Jörg

2017-07-04

Photoconvertible fluorescent proteins (pcRFPs) are a group of fluorophores that undergo an irreversible green-to-red shift in emission colour upon irradiation with near-ultraviolet (near-UV) light. Despite their wide application in biotechnology, the high-level expression of pcRFPs in mesophotic and depth-generalist coral species currently lacks a biological explanation. Additionally, reduced penetration of near-UV wavelengths in water poses the question whether light-driven photoconversion is relevant in the mesophotic zone, or whether a different mechanism is involved in the post-translational pigment modification in vivo. Here, we show in a long-term mesocosm experiment that photoconversion in vivo is entirely dependent on near-UV wavelengths. However, a near-UV intensity equivalent to the mesophotic underwater light field at 80 m depth is sufficient to drive the process in vitro, suggesting that photoconversion can occur near the lower distribution limits of these corals. Furthermore, live coral colonies showed evidence of efficient Förster Resonance Energy Transfer (FRET). Our simulated mesophotic light field maintained the pcRFP pool in a partially photoconverted state in vivo, maximising intra-tetrameric FRET and creating a long-range wavelength conversion system with higher quantum yield than other native RFPs. We hypothesise that efficient conversion of blue wavelengths, abundant at depth, into orange-red light could constitute an adaptation of corals to life in light-limited environments.

FRET-Mediated Long-Range Wavelength Transformation by Photoconvertible Fluorescent Proteins as an Efficient Mechanism to Generate Orange-Red Light in Symbiotic Deep Water Corals

PubMed Central

Bollati, Elena; Plimmer, Daniel; D’Angelo, Cecilia; Wiedenmann, Jörg

2017-01-01

Photoconvertible fluorescent proteins (pcRFPs) are a group of fluorophores that undergo an irreversible green-to-red shift in emission colour upon irradiation with near-ultraviolet (near-UV) light. Despite their wide application in biotechnology, the high-level expression of pcRFPs in mesophotic and depth-generalist coral species currently lacks a biological explanation. Additionally, reduced penetration of near-UV wavelengths in water poses the question whether light-driven photoconversion is relevant in the mesophotic zone, or whether a different mechanism is involved in the post-translational pigment modification in vivo. Here, we show in a long-term mesocosm experiment that photoconversion in vivo is entirely dependent on near-UV wavelengths. However, a near-UV intensity equivalent to the mesophotic underwater light field at 80 m depth is sufficient to drive the process in vitro, suggesting that photoconversion can occur near the lower distribution limits of these corals. Furthermore, live coral colonies showed evidence of efficient Förster Resonance Energy Transfer (FRET). Our simulated mesophotic light field maintained the pcRFP pool in a partially photoconverted state in vivo, maximising intra-tetrameric FRET and creating a long-range wavelength conversion system with higher quantum yield than other native RFPs. We hypothesise that efficient conversion of blue wavelengths, abundant at depth, into orange-red light could constitute an adaptation of corals to life in light-limited environments. PMID:28677653

Visible light optical coherence tomography for microvascular oximetry in ocular circulation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Chen, Siyu; Yi, Ji; Zhang, Hao F.

2016-03-01

Visible light optical coherence tomography (vis-OCT) is intrinsically capable of optical determination of blood oxygen saturation (sO2). Thanks to its 3D sectioning ability, confounding factors that plaque multi-wavelength fundus photography can be avoided. We further supplemented it with motion-enhanced angiography (vis-OCTA), which allowed us to resolve retinal micro vessels without losing spectral information. As a result, spectroscopic vis-OCTA can extract microvascular sO2 which are generally inaccessible. Here we extend the theoretical formulation of vis-OCTA oximetry to include optical attenuation, scattering and motion contrast. The model allows robust estimation of sO2, while also promising reduction of illuminating power to 1/3 of current value of ~1 mW. To demonstrate the capability of our approach, we performed oxygen challenge while taking vis-OCTA measurements on rat ocular circulation in vivo. We supplied the experiment animal with the following gas mixture: normal air, 5% CO2 air, pure O2 and 10% O2 air. For each inhalation gas, the OCTA measurements were compared with peripheral capillary sO2 (spO2) provided by a pulse oximeter. The retinal artery sO2 measurements corresponded well with spO2 reading as expected (R2 = 0.87). We found that both retinal and choroidal circulation sO2 moderately increased when we supplied 5% CO2 air. 100% O2 inhalation significantly increased both artery and vein oxygenation. On the contrary, 10% O2 air could deplete the oxygen reservoir in the circulation and lead to low sO2 readings.

A high-speed, eight-wavelength visible light-infrared pyrometer for shock physics experiments

NASA Astrophysics Data System (ADS)

Wang, Rongbo; Li, Shengfu; Zhou, Weijun; Luo, Zhen-Xiong; Meng, Jianhua; Tian, Jianhua; He, Lihua; Cheng, Xianchao

2017-09-01

An eight-channel, high speed pyrometer for precise temperature measurement is designed and realized in this work. The addition of longer-wavelength channels sensitive at lower temperatures highly expands the measured temperature range, which covers the temperature of interest in shock physics from 1500K-10000K. The working wavelength range is 400-1700nm from visible light to near-infrared (NIR). Semiconductor detectors of Si and InGaAs are used as photoelectric devices, whose bandwidths are 50MHz and 150MHz respectively. Benefitting from the high responsivity and high speed of detectors, the time resolution of the pyrometer can be smaller than 10ns. By combining the high-transmittance beam-splitters and narrow-bandwidth filters, the peak spectrum transmissivity of each channel can be higher than 60%. The gray-body temperatures of NaI crystal under shock-loading are successfully measured by this pyrometer.

Dynamic generation and coherent control of beating stationary light pulses by a microwave coupling field in five-level cold atoms

NASA Astrophysics Data System (ADS)

Bao, Qian-Qian; Zhang, Yan; Cui, Cui-Li; Meng, Shao-Ying; Fang, You-Wei; Tian, Xue-Dong

2018-04-01

We propose an efficient scheme for generating and controlling beating stationary light pulses in a five-level atomic sample driven into electromagnetically induced transparency condition. This scheme relies on an asymmetrical procedure of light storage and retrieval tuned by two counter-propagating control fields where an additional coupling field, such as the microwave field, is introduced in the retrieval stage. A quantum probe field, incident upon such an atomic sample, is first transformed into spin coherence excitation of the atoms and then retrieved as beating stationary light pulses exhibiting a series of maxima and minima in intensity due to the alternative constructive and destructive interference. It is convenient to control the beating stationary light pulses just by manipulating the intensity and detuning of the additional microwave field. This interesting phenomenon involves in fact the coherent manipulation of dark-state polaritons and could be explored to achieve the efficient temporal splitting of stationary light pulses and accurate measurement of the microwave intensity.

Dim-light photoreceptor of chub mackerel Scomber japonicus and the photoresponse upon illumination with LEDs of different wavelengths.

PubMed

Jang, Jun-Chul; Choi, Mi-Jin; Yang, Yong-Soo; Lee, Hyung-Been; Yu, Young-Moon; Kim, Jong-Myoung

2016-06-01

To study the absorption characteristics of rhodopsin, a dim-light photoreceptor, in chub mackerel (Scomber japonicus) and the relationship between light wavelengths on the photoresponse, the rod opsin gene was cloned into an expression vector, pMT4. Recombinant opsin was transiently expressed in COS-1 cells and reconstituted with 11-cis-retinal. Cells containing the regenerated rhodopsin were solubilized and subjected to UV/Vis spectroscopic analysis in the dark and upon illumination. Difference spectra from the lysates indicated an absorption maximum of mackerel rhodopsin around 500 nm. Four types of light-emitting diode (LED) modules with different wavelengths (red, peak 627 nm; cyan, 505 nm; blue, 442 nm; white, 447 + 560 nm) were constructed to examine their effects on the photoresponse in chub mackerel. Behavioral responses of the mackerels, including speed and frequencies acclimated in the dark and upon LED illumination, were analyzed using an underwater acoustic camera. Compared to an average speed of 22.25 ± 1.57 cm/s of mackerel movement in the dark, speed increased to 22.97 ± 0.29, 24.66 ± 1.06, 26.28 ± 2.28, and 25.19 ± 1.91 cm/s upon exposure to red, blue, cyan, and white LEDs, respectively. There were increases of 103.48 ± 1.58, 109.37 ± 5.29, 118.48 ± 10.82, and 109.43 ± 3.92 %, respectively, in the relative speed of the fishes upon illumination with red, blue, cyan, and white LEDs compared with that in the dark (set at 100 %). Similar rate of wavelength-dependent responses was observed in a frequency analysis. These results indicate that an LED emitting a peak wavelength close to an absorption maximum of rhodopsin is more effective at eliciting a response to light.

High Power, Millimeter-Wavelength, Coherent Radiation Sources.

DTIC Science & Technology

1986-09-25

J . Murphy, Ph.D. (1982). 5. M. Abdelkarim , Ph.D. (1984). 6. T. Buller, Ph.D. (1985). a 7. B. Johnson, Ph.D. (1985). 8. E. Garate, Ph.D. (1985). 9. R...AD-A174 521 HIGH POWER KILL IMETER-WAVELENGTH COHERENTRAITO 1/ SOURCES(U) DARTMOUTH COLL HANOVER N H DEPT OF PHYSICS AND ASTRONOMY J E WALSH 25 SEP...82 - 1/31/86 -.: AIR F , 2 ..... . . T . ... ...... , 7 Approved for public release;"":" " ’n2. j ;’L’-’ ,- -"!d ,-d 12 l . 7. ... - ’ " + d. Chief

Exposure to blue wavelength light modulates anterior cingulate cortex activation in response to 'uncertain' versus 'certain' anticipation of positive stimuli.

PubMed

Alkozei, Anna; Smith, Ryan; Killgore, William D S

2016-03-11

Blue wavelength light has been used as an effective treatment for some types of mood disorders and circadian rhythm related sleep problems. We hypothesized that acute exposure to blue wavelength light would directly affect the functioning of neurocircuity implicated in emotion regulation (i.e., ventromedial prefrontal cortex, amygdala, insula, and anterior cingulate cortex [ACC]) during 'certain' and 'uncertain' anticipation of negative and positive stimuli. Thirty-five healthy adults were randomized to receive a thirty-minute exposure to either blue (active) or amber (placebo) light, immediately followed by an emotional anticipation task during functional magnetic resonance imaging (fMRI). In contrast to placebo, participants in the blue light group showed significantly reduced activation within the rostral ACC during 'uncertain' anticipation (i.e., uncertainty regarding whether a positive or negative stimulus would be shown) in comparison to 'certain' anticipation of a positive stimulus. These findings may be explicable in terms of interactions between blue light exposure and the influence of specific neuromodulators on ACC-mediated decision-making mechanisms. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Retinal Optical Coherence Tomography Imaging

NASA Astrophysics Data System (ADS)

Drexler, Wolfgang; Fujimoto, James G.

The eye is essentially transparent, transmitting light with only minimal optical attenuation and scattering providing easy optical access to the anterior segment as well as the retina. For this reason, ophthalmic and especially retinal imaging has been not only the first but also most successful clinical application for optical coherence tomography (OCT). This chapter focuses on the development of OCT technology for retinal imaging. OCT has significantly improved the potential for early diagnosis, understanding of retinal disease pathogenesis, as well as monitoring disease progression and response to therapy. Development of ultrabroad bandwidth light sources and high-speed detection techniques has enabled significant improvements in ophthalmic OCT imaging performance, demonstrating the potential of three-dimensional, ultrahigh-resolution OCT (UHR OCT) to perform noninvasive optical biopsy of the living human retina, i.e., the in vivo visualization of microstructural, intraretinal morphology in situ approaching the resolution of conventional histopathology. Significant improvements in axial resolution and speed not only enable three-dimensional rendering of retinal volumes but also high-definition, two-dimensional tomograms, topographic thickness maps of all major intraretinal layers, as well as volumetric quantification of pathologic intraretinal changes. These advances in OCT technology have also been successfully applied in several animal models of retinal pathologies. The development of light sources emitting at alternative wavelengths, e.g., around #1,060 nm, not only enabled three-dimensional OCT imaging with enhanced choroidal visualization but also improved OCT performance in cataract patients due to reduced scattering losses in this wavelength region. Adaptive optics using deformable mirror technology, with unique high stroke to correct higher-order ocular aberrations, with specially designed optics to compensate chromatic aberration of the human eye, in

Modeling of coherent ultrafast magneto-optical experiments: Light-induced molecular mean-field model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hinschberger, Y.; Hervieux, P.-A.

2015-12-28

We present calculations which aim to describe coherent ultrafast magneto-optical effects observed in time-resolved pump-probe experiments. Our approach is based on a nonlinear semi-classical Drude-Voigt model and is used to interpret experiments performed on nickel ferromagnetic thin film. Within this framework, a phenomenological light-induced coherent molecular mean-field depending on the polarizations of the pump and probe pulses is proposed whose microscopic origin is related to a spin-orbit coupling involving the electron spins of the material sample and the electric field of the laser pulses. Theoretical predictions are compared to available experimental data. The model successfully reproduces the observed experimental trendsmore » and gives meaningful insight into the understanding of magneto-optical rotation behavior in the ultrafast regime. Theoretical predictions for further experimental studies are also proposed.« less

Coherent backscattering of light by an inhomogeneous cloud of cold atoms

NASA Astrophysics Data System (ADS)

Labeyrie, Guillaume; Delande, Dominique; Müller, Cord A.; Miniatura, Christian; Kaiser, Robin

2003-03-01

When a quasiresonant laser beam illuminates an optically thick cloud of laser-cooled rubidium atoms, the average diffuse intensity reflected off the sample is enhanced in a narrow angular range around the direction of exact backscattering. This phenomenon is known as coherent backscattering (CBS). By detuning the laser from resonance, we are able to modify the light scattering mean-free path inside the sample and we record accordingly the variations of the CBS cone shape. We then compare the experimental data with theoretical calculations and Monte Carlo simulations including the effect of the light polarization and of the internal structure of the atoms. We confirm that the internal structure strongly affects the enhancement factor of the cone and we show that the unusual shape of the atomic medium—approximately a spherically-symmetric, Gaussian density profile—strongly affects the width and shape of the cone.

Partially coherent isodiffracting pulsed beams

NASA Astrophysics Data System (ADS)

Koivurova, Matias; Ding, Chaoliang; Turunen, Jari; Pan, Liuzhan

2018-02-01

We investigate a class of isodiffracting pulsed beams, which are superpositions of transverse modes supported by spherical-mirror laser resonators. By employing modal weights that, for stationary light, produce a Gaussian Schell-model beam, we extend this standard model to pulsed beams. We first construct the two-frequency cross-spectral density function that characterizes the spatial coherence in the space-frequency domain. By assuming a power-exponential spectral profile, we then employ the generalized Wiener-Khintchine theorem for nonstationary light to derive the two-time mutual coherence function that describes the space-time coherence of the ensuing beams. The isodiffracting nature of the laser resonator modes permits all (paraxial-domain) calculations at any propagation distance to be performed analytically. Significant spatiotemporal coupling is revealed in subcycle, single-cycle, and few-cycle domains, where the partial spatial coherence also leads to reduced temporal coherence even though full spectral coherence is assumed.

Coherent perfect rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Dawson, Nathan J.; Andrews, James H.

2012-09-01

Two classes of conservative, linear, optical rotary effects (optical activity and Faraday rotation) are distinguished by their behavior under time reversal. Faraday rotation, but not optical activity, is capable of coherent perfect rotation, by which we mean the complete transfer of counterpropagating coherent light fields into their orthogonal polarization. Unlike coherent perfect absorption, however, this process is explicitly energy conserving and reversible. Our study highlights the necessity of time-reversal-odd processes (not just absorption) and coherence in perfect mode conversion and thus informs the optimization of active multiport optical devices.

Coherent ultra-violet to near-infrared generation in silica ridge waveguides

PubMed Central

Yoon Oh, Dong; Yang, Ki Youl; Fredrick, Connor; Ycas, Gabriel; Diddams, Scott A.; Vahala, Kerry J.

2017-01-01

Short duration, intense pulses of light can experience dramatic spectral broadening when propagating through lengths of optical fibre. This continuum generation process is caused by a combination of nonlinear optical effects including the formation of dispersive waves. Optical analogues of Cherenkov radiation, these waves allow a pulse to radiate power into a distant spectral region. In this work, efficient and coherent dispersive wave generation of visible to ultraviolet light is demonstrated in silica waveguides on a silicon chip. Unlike fibre broadeners, the arrays provide a wide range of emission wavelength choices on a single, compact chip. This new capability is used to simplify offset frequency measurements of a mode-locked frequency comb. The arrays can also enable mode-locked lasers to attain unprecedented tunable spectral reach for spectroscopy, bioimaging, tomography and metrology. PMID:28067233

Designing optically pumped InGaN quantum wells with long wavelength emission for a phosphor-free device with polarized white-light emission

NASA Astrophysics Data System (ADS)

Kowsz, Stacy J.; Pynn, Christopher D.; Wu, Feng; Farrell, Robert M.; Speck, James S.; DenBaars, Steven P.; Nakamura, Shuji

2016-02-01

We report a semipolar III-nitride device in which an electrically injected blue light emitting diode optically pumps monolithic long wavelength emitting quantum wells (QWs) to create polarized white light. We have demonstrated an initial device with emission peaks at 440 nm and 560 nm from the electrically injected and optically pumped QWs, respectively. By tuning the ratio of blue to yellow, white light was measured with a polarization ratio of 0.40. High indium content InGaN is required for long wavelength emission but is difficult to achieve because it requires low growth temperatures and has a large lattice mismatch with GaN. This device design incorporates optically pumped QWs for long wavelength emission because they offer advantages over using electrically injected QWs. Optically pumped QWs do not have to be confined within a p-n junction, and carrier transport is not a concern. Thus, thick GaN barriers can be incorporated between multiple InGaN QWs to manage stress. Optically pumping long wavelength emitting QWs also eliminates high temperature steps that degrade high indium content InGaN but are required when growing p-GaN for an LED structure. Additionally, by eliminating electrical injection, the doping profile can instead be engineered to affect the emission wavelength. We discuss ongoing work focused on improving polarized white light emission by optimizing the optically pumped QWs. We consider the effects of growth conditions, including: trimethylindium (TMI) flow rate, InGaN growth rate, and growth temperature. We also examine the effects of epitaxial design, including: QW width, number of QWs, and doping.

Coherent generation of symmetry-forbidden phonons by light-induced electron-phonon interactions in magnetite

NASA Astrophysics Data System (ADS)

Borroni, S.; Baldini, E.; Katukuri, V. M.; Mann, A.; Parlinski, K.; Legut, D.; Arrell, C.; van Mourik, F.; Teyssier, J.; Kozlowski, A.; Piekarz, P.; Yazyev, O. V.; Oleś, A. M.; Lorenzana, J.; Carbone, F.

2017-09-01

Symmetry breaking across phase transitions often causes changes in selection rules and emergence of optical modes which can be detected via spectroscopic techniques or generated coherently in pump-probe experiments. In second-order or weakly first-order transitions, fluctuations of the ordering field are present above the ordering temperature, giving rise to intriguing precursor phenomena, such as critical opalescence. Here, we demonstrate that in magnetite (Fe3O4 ) light excitation couples to the critical fluctuations of the charge order and coherently generates structural modes of the ordered phase above the critical temperature of the Verwey transition. Our findings are obtained by detecting coherent oscillations of the optical constants through ultrafast broadband spectroscopy and analyzing their dependence on temperature. To unveil the coupling between the structural modes and the electronic excitations, at the origin of the Verwey transition, we combine our results from pump-probe experiments with spontaneous Raman scattering data and theoretical calculations of both the phonon dispersion curves and the optical constants. Our methodology represents an effective tool to study the real-time dynamics of critical fluctuations across phase transitions.

Influence of multiple light-scattering on TiO2 nanoparticles imbedded into stratum corneum on light transmittance in UV and visible wavelength regions

NASA Astrophysics Data System (ADS)

Popov, Alexey P.; Priezzhev, Alexander V.; Lademann, Jürgen; Myllylä, Risto

2007-05-01

This paper focuses on the simulation of propagation of radiation in UV and visible wavelength regions within a superficial skin layer (stratum corneum, SC) partially filled with titanium dioxide (TiO II) nanoparticles. Volume concentrations of the particles (0.67% - 2.25%) correspond to the maximal concentrations of the considered particles in the frames of independent scattering. Transmittance of 307-, 400-, and 500-nm light through a 20-μm thick SC is calculated. The effect of the TiO II nanoparticles on the contribution of photons undergone different numbers of scattering acts into transmittance is considered. It is shown that administration of the nanoparticles results in the broadening of the distribution of transmitted photons over undergone scattering acts. It also results in the shift of the maximum location of this distribution to larger number of scattering acts for the wavelengths of 400 and 500 nm being the latter the most pronounced. The increase of undergone scattering acts leads to the elongation of photon trajectories within the medium and results in the increase of the diffuse reflected light and the transmittance decrease.

The Cause of the Hot Spot in Vegetation Canopies and Soils: Shadow-Hiding Versus Coherent Backscatter

NASA Technical Reports Server (NTRS)

Hapke, Bruce; DiMucci, Dominick; Nelson, Robert; Smythe, William

1996-01-01

Two different mechanisms, shadow-hiding and coherent backscatter, can cause a hot spot, or opposition effect, in the bidirectional reflectance of vegetation and soils. Because the two mechanisms sample different properties, it is important to know which one is primarily responsible in a given medium. This question can be answered by measuring the bidirectional reflectance in circularly polarized light. If the results of the limited experiments reported here can be extrapolated to a wider range of materials, it appears that the primary cause of the hot spot in most vegetation canopies and in moist, clumpy soils is shadow-hiding. However, in vegetation with large numbers of wavelength-sized structures, such as mosses, and in dry, fine-grained soils, the hot spot is dominated by coherent backscatter.

Nonclassical properties of coherent light in a pair of coupled anharmonic oscillators

NASA Astrophysics Data System (ADS)

Alam, Nasir; Mandal, Swapan

2016-01-01

The Hamiltonian and hence the equations of motion involving the field operators of two anharmonic oscillators coupled through a linear one is framed. It is found that these equations of motion involving the non-commuting field operators are nonlinear and are coupled to each other and hence pose a great problem for getting the solutions. In order to investigate the dynamics and hence the nonclassical properties of the radiation fields, we obtain approximate analytical solutions of these coupled nonlinear differential equations involving the non-commuting field operators up to the second orders in anharmonic and coupling constants. These solutions are found useful for investigating the squeezing of pure and mixed modes, amplitude squared squeezing, principal squeezing, and the photon antibunching of the input coherent radiation field. With the suitable choice of the parameters (photon number in various field modes, anharmonic, and coupling constants, etc.), we calculate the second order variances of field quadratures of various modes and hence the squeezing, amplitude squared, and mixed mode squeezing of the input coherent light. In the absence of anharmonicities, it is found that these nonlinear nonclassical phenomena (squeezing of pure and mixed modes, amplitude squared squeezing and photon antibunching) are completely absent. The percentage of squeezing, mixed mode squeezing, amplitude squared squeezing increase with the increase of photon number and the dimensionless interaction time. The collapse and revival phenomena in squeezing, mixed mode squeezing and amplitude squared squeezing are exhibited. With the increase of the interaction time, the monotonic increasing nature of the squeezing effects reveal the presence of unwanted secular terms. It is established that the mere coupling of two oscillators through a third one does not produces the squeezing effects of input coherent light. However, the pure nonclassical phenomena of antibunching of photons in vacuum

On the use of variable coherence in inverse scattering problems

NASA Astrophysics Data System (ADS)

Baleine, Erwan

Even though most of the properties of optical fields, such as wavelength, polarization, wavefront curvature or angular spectrum, have been commonly manipulated in a variety of remote sensing procedures, controlling the degree of coherence of light did not find wide applications until recently. Since the emergence of optical coherence tomography, a growing number of scattering techniques have relied on temporal coherence gating which provides efficient target selectivity in a way achieved only by bulky short pulse measurements. The spatial counterpart of temporal coherence, however, has barely been exploited in sensing applications. This dissertation examines, in different scattering regimes, a variety of inverse scattering problems based on variable spatial coherence gating. Within the framework of the radiative transfer theory, this dissertation demonstrates that the short range correlation properties of a medium under test can be recovered by varying the size of the coherence volume of an illuminating beam. Nonetheless, the radiative transfer formalism does not account for long range correlations and current methods for retrieving the correlation function of the complex susceptibility require cumbersome cross-spectral density measurements. Instead, a variable coherence tomographic procedure is proposed where spatial coherence gating is used to probe the structural properties of single scattering media over an extended volume and with a very simple detection system. Enhanced backscattering is a coherent phenomenon that survives strong multiple scattering. The variable coherence tomography approach is extended in this context to diffusive media and it is demonstrated that specific photon trajectories can be selected in order to achieve depth-resolved sensing. Probing the scattering properties of shallow and deeper layers is of considerable interest in biological applications such as diagnosis of skin related diseases. The spatial coherence properties of an

Strong spectral variation of biomass smoke light absorption and single scattering albedo observed with a novel dual-wavelength photoacoustic instrument

Treesearch

Kristin Lewis; William P. Arnott; Hans Moosmuller; Cyle E. Wold

2008-01-01

A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany...

Portable atomic frequency standard based on coherent population trapping

NASA Astrophysics Data System (ADS)

Shi, Fan; Yang, Renfu; Nian, Feng; Zhang, Zhenwei; Cui, Yongshun; Zhao, Huan; Wang, Nuanrang; Feng, Keming

2015-05-01

In this work, a portable atomic frequency standard based on coherent population trapping is designed and demonstrated. To achieve a portable prototype, in the system, a single transverse mode 795nm VCSEL modulated by a 3.4GHz RF source is used as a pump laser which generates coherent light fields. The pump beams pass through a vapor cell containing atom gas and buffer gas. This vapor cell is surrounded by a magnetic shield and placed inside a solenoid which applies a longitudinal magnetic field to lift the Zeeman energy levels' degeneracy and to separate the resonance signal, which has no first-order magnetic field dependence, from the field-dependent resonances. The electrical control system comprises two control loops. The first one locks the laser wavelength to the minimum of the absorption spectrum; the second one locks the modulation frequency and output standard frequency. Furthermore, we designed the micro physical package and realized the locking of a coherent population trapping atomic frequency standard portable prototype successfully. The short-term frequency stability of the whole system is measured to be 6×10-11 for averaging times of 1s, and reaches 5×10-12 at an averaging time of 1000s.

Imaging of tissue using a NIR supercontinuum laser light source with wavelengths in the second and third NIR optical windows

NASA Astrophysics Data System (ADS)

Sordillo, Laura A.; Lindwasser, Lukas; Budansky, Yury; Leproux, Philippe; Alfano, R. R.

2015-03-01

Supercontinuum light (SC) at wavelengths in the second (1,100 nm to 1,350 nm) and third (1,600 nm to 1,870 nm) NIR optical windows can be used to improve penetration depths of light through tissue and produce clearer images. Image quality is increased due to a reduction in scattering (inverse wavelength power dependence 1/λn, n≥1). We report on the use of a compact Leukos supercontinuum laser (model STM-2000-IR), which utilizes the spectral range from 700 nm to 2,400 nm and offers between 200 - 500 microwatt/nm power in the second and third NIR windows, with an InGaAs detector to image abnormalities hidden beneath thick tissue.

Research and development toward a 4.5-1.5 Å linac coherent light source (LCLS) at SLAC

NASA Astrophysics Data System (ADS)

Tatchyn, R.; Arthur, J.; Baltay, M.; Bane, K.; Boyce, R.; Cornacchia, M.; Cremer, T.; Fisher, A.; Hahn, S.-J.; Hernandez, M.; Loew, G.; Miller, R.; Nelson, W. R.; Nuhn, H.-D.; Palmer, D.; Paterson, J.; Raubenheimer, T.; Weaver, J.; Wiedemann, H.; Winick, H.; Pellegrini, C.; Travish, G.; Scharlemann, E. T.; Caspi, S.; Fawley, W.; Halbach, K.; Kim, K.-J.; Schlueter, R.; Xie, M.; Meyerhofer, D.; Bonifacio, R.; De Salvo, L.

1996-02-01

In recent years significant studies have been initiated on the feasibility of utilizing a portion of the 3 km S-band accelerator at SLAC to drive a short wavelength (4.5-1.5 Å) Linac Coherent Light Source (LCLS), a Free-Electron Laser (FEL) operating in the Self-Amplified Spontaneous Emission (SASE) regime. Electron beam requirements for single-pass saturation in a minimal time include: 1) a peak current in the 7 kA range, 2) a relative energy spread of <0.05%, and 3) a transverse emittance, ɛ [rad-m], approximating the diffraction-limit condition ɛ = {λ}/{4π}, where λ[m] is the output wavelength. Requirements on the insertion device include field error levels of 0.02% for keeping the electron bunch centered on and in phase with the amplified photons, and a focusing beta of 8 m/rad for inhibiting the dilution of its transverse density. Although much progress has been made in developing individual components and beam-processing techniques necessary for LCLS operation down to ˜20 Å, a substantial amount of research and development is still required in a number of theoretical and experimental areas leading to the construction and operation of a 4.5-1.5 Å LCLS. In this paper we report on a research and development program underway and in planning at SLAC for addressing critical questions in these areas. These include the construction and operation of a linac test stand for developing laser-driven photocathode rf guns with normalized emittances approaching 1 mm-mrad; development of advanced beam compression, stability, and emittance control techniques at multi-GeV energies; the construction and operation of a FEL Amplifier Test Experiment (FATE) for theoretical and experimental studies of SASE at IR wavelengths; an undulator development program to investigate superconducting, hybrid/permanent magnet (hybrid/PM), and pulsed-Cu technologies; theoretical and computational studies of high-gain FEL physics and LCLS component designs; development of X-ray optics and

Channel capacity of OAM based FSO communication systems with partially coherent Bessel-Gaussian beams in anisotropic turbulence

NASA Astrophysics Data System (ADS)

Peng, Juan; Zhang, Li; Zhang, Kecheng; Ma, Junxian

2018-07-01

Based on the Rytov approximation theory, the transmission model of an orbital angular momentum (OAM)-carrying partially coherent Bessel-Gaussian (BG) beams propagating in weak anisotropic turbulence is established. The corresponding analytical expression of channel capacity is presented. Influences of anisotropic turbulence parameters and beam parameters on channel capacity of OAM-based free-space optical (FSO) communication systems are discussed in detail. The results indicate channel capacity increases with increasing of almost all of the parameters except for transmission distance. Raising the values of some parameters such as wavelength, propagation altitude and non-Kolmogorov power spectrum index, would markedly improve the channel capacity. In addition, we evaluate the channel capacity of Laguerre-Gaussian (LG) beams and partially coherent BG beams in anisotropic turbulence. It indicates that partially coherent BG beams are better light sources candidates for mitigating the influences of anisotropic turbulence on channel capacity of OAM-based FSO communication systems.

Surface plasmon resonance enhanced light absorption and wavelength tuneable in gold-coated iron oxide spherical nanoparticle

NASA Astrophysics Data System (ADS)

Dasri, Thananchai; Chingsungnoen, Artit

2018-06-01

Surface plasmon in nano-sized particles, such as gold, silver, copper and their composites, has recently attracted a great deal of attention due to its possible uses in many applications, especially in life sciences. It is desirable for application devices with a tenability of surface plasmon wavelength and optical properties enhancement. This article presents enhanced optical light absorption and tunable wavelength in gold-coated magnetite (Fe3O4@Au core-shell) nanoparticles embedded in water using the theoretical method of discrete dipole approximation (DDA). The absorption spectra in the wavelengths from 350 to 900 nm were found to be the spectra obtained from Fe3O4@Au core-shell nanoparticles, and when compared with pure Fe3O4 nanoparticles, the surface plasmon resonance can be enhanced and tuned over the entire visible spectrum (viz. 350-800 nm) of the electromagnetic spectrum by varying the Au shell thickness (2-5 nm). Similarly, the Faraday rotation spectra can also be obtained.

Coherent Raman scattering with incoherent light for a multiply resonant mixture: Theory

NASA Astrophysics Data System (ADS)

Kirkwood, Jason C.; Ulness, Darin J.; Stimson, Michael J.; Albrecht, A. C.

1998-02-01

The theory for coherent Raman scattering (CRS) with broadband incoherent light is presented for a multiply resonant, multicomponent mixture of molecules that exhibits simultaneous multiple resonances with the frequencies of the driving fields. All possible pairwise hyperpolarizability contributions to the signal intensity are included in the theoretical treatment-(resonant-resonant, resonant-nonresonant, and nonresonant-nonresonant correlations between chromophores) and it is shown how the different types of correlations manifest themselves as differently behaved components of the signal intensity. The Raman resonances are modeled as Lorentzians in the frequency domain, as is the spectral density of the incoherent light. The analytic results for this multiply resonant mixture are presented and applied to a specific binary mixture. These analytic results will be used to recover frequencies and dephasing times in a series of experiments on multiply resonant mixtures.

The Wavelength Dependence of the Lunar Phase Curve as Seen by the LRO LAMP

NASA Astrophysics Data System (ADS)

Liu, Y.; Retherford, K. D.; Greathouse, T. K.; Hendrix, A. R.; Mandt, K.; Gladstone, R.; Cahill, J. T.; Egan, A.; Kaufmann, D. E.; Grava, C.; Pryor, W. R.

2016-12-01

The Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) provides global coverage of both nightside and dayside of the Moon in the far ultraviolet (FUV) wavelengths. The nightside observations use roughly uniform diffuse illumination sources from interplanetary medium Lyman-α sky glow and UV-bright stars so that traditional photometric corrections do not apply. In contrast, the dayside observations use sunlight as its illumination source where bidirectional reflectance is measured. The bidirectional reflectance is dependent on the incident, emission, and phase angles as well as the soil properties. Thus the comparisons of dayside mapping and nightside mapping techniques offer a method for cross-comparing the photometric correction factors because the observations are made under different lighting and viewing conditions. Specifically, the nightside data well constrain the single-scattering coefficient. We'll discuss the wavelength dependence of the lunar phase curve as seen by the LAMP instrument in dayside data. Our preliminary results indicate that the reflectance in the FUV wavelengths decreases with the increasing phase angles from 0° to 90°, similar to the phase curve in the UV-visible wavelengths as studied by Hapke et al. (2012) using LRO wide angle camera (WAC) data, among other visible-wavelength lunar studies. Particularly, we'll report how coherent backscattering and shadow hiding contribute to the opposition surge, given the fact that the albedo at FUV wavelengths is extremely low and thus multiple scattering is significantly less important. Finally, we'll report the derived Hapke parameters at FUV wavelengths for our study areas.

Reduction of patulin in apple juice products by UV light of different wavelengths in the UVC range.

PubMed

Zhu, Yan; Koutchma, Tatiana; Warriner, Keith; Zhou, Ting

2014-06-01

This study evaluated three UVC wavelengths (222, 254, and 282 nm) to degrade patulin introduced into apple juice or apple cider. The average UV fluences of 19.6, 84.3, 55.0, and 36.6 mJ·cm(-2) achieved through exposure to UV lamps at 222-, 254-, and 282-nm wavelengths and the combination of these wavelengths, respectively, resulted in 90% reduction of patulin in apple juice. Therefore, the order of efficiency of the three wavelength lamps was as follows: far UVC (222 nm) > far UVC plus (282 nm) > UVC (254 nm). In terms of color, treatment of apple juice with 222 nm resulted in an increase in the L* (lightness) value but decreases in a* (redness) and b* (yellowness) values, although the changes were insignificantly different from the values for nontreated controls based on a sensory evaluation. The ascorbic acid loss in juice treated at 222 nm to support 90% reduction of patulin was 36.5%, compared with ascorbic acid losses of 45.3 and 36.1% in samples treated at 254 and 282 nm, respectively. The current work demonstrated that the 222-nm wavelength possesses the highest efficiency for patulin reduction in apple juice when compared with the reductions by 254 and 282 nm, with no benefit gained from using a combination of wavelengths.

Dual-Wavelength InGaAsSb/AlGaAsSb Quantum-Well Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Nguyen, Tien Dai; Hwang, Jehwan; Kim, Yeongho; Kim, Eui-Tae; Kim, Jun Oh; Lee, Sang Jun

2018-05-01

We have investigated the structural characteristics and the device performance of three-stack InGaAsSb/AlGaAsSb quantum-well (QW) light-emitting diodes (LEDs) grown by using molecular beam epitaxy. The QW LED structure with an 8-nm well thickness had a single peak emission wavelength of 2.06 μm at an injection current of 0.3 A at room temperature. However, the QWLEDs with three different well thicknesses of 5-, 10-, and 15-nm had double peak emission wavelengths of 1.97 and 2.1 μm at an injection current of 1.1 A, which were associated with the radiative recombination in the QW with a 5-nm well thickness and the overlapped emission from the QWs with 10- and 15-nm well thicknesses, respectively.

A fiber optic, ultraviolet light-emitting diode-based, two wavelength fluorometer for monitoring reactive adsorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Granz, Christopher D.; Whitten, James E., E-mail: James-Whitten@uml.edu; Schindler, Bryan J.

Construction and use of an ultraviolet light-emitting diode-based fluorometer for measuring photoluminescence (PL) from powder samples with a fiber optic probe is described. Fluorescence at two wavelengths is detected by miniature photomultiplier tubes, each equipped with a different band pass filter, whose outputs are analyzed by a microprocessor. Photoluminescent metal oxides and hydroxides, and other semiconducting nanoparticles, often undergo changes in their emission spectra upon exposure to reactive gases, and the ratio of the PL intensities at two wavelengths is diagnostic of adsorption. Use of this instrument for reactive gas sensing and gas filtration applications is illustrated by measuring changesmore » in the PL ratio for zirconium hydroxide and zinc oxide particles upon exposure to air containing low concentrations of sulfur dioxide.« less

Light alters nociceptive effects of magnetic field shielding in mice: intensity and wavelength considerations

PubMed Central

Prato, Frank S; Desjardins-Holmes, Dawn; Keenliside, Lynn D; McKay, Julia C; Robertson, John A; Thomas, Alex W

2008-01-01

Previous experiments with mice have shown that repeated 1 hour daily exposure to an ambient magnetic field-shielded environment induces analgesia (antinociception). The exposures were carried out in the dark (less than 2.0×1016 photons s−1 m−2) during the mid-light phase of the diurnal cycle. However, if the mice were exposed in the presence of visible light (2.0×1018 photons s−1 m−2, 400–750 nm), then the analgesic effects of shielding were eliminated. Here, we show that this effect of light is intensity and wavelength dependent. Introduction of red light (peak at 635 nm) had little or no effect, presumably because mice do not have photoreceptors sensitive to red light above 600 nm in their eyes. By contrast, introduction of ultraviolet light (peak at 405 nm) abolished the effect, presumably because mice do have ultraviolet A receptors. Blue light exposures (peak at 465 nm) of different intensities demonstrate that the effect has an intensity threshold of approximately 12% of the blue light in the housing facility, corresponding to 5×1016 photons s−1 m−2 (integral). This intensity is similar to that associated with photoreceptor-based magnetoreception in birds and in mice stimulates photopic/cone vision. Could the detection mechanism that senses ambient magnetic fields in mice be similar to that in bird navigation? PMID:18583276

Self-spectral calibration for spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Zhang, Xianling; Gao, Wanrong; Bian, Haiyi; Chen, Chaoliang; Liao, Jiuling

2013-06-01

A different real-time self-wavelength calibration method for spectral domain optical coherence tomography is presented in which interference spectra measured from two arbitrary points on the tissue surface are used for calibration. The method takes advantages of two favorable conditions of optical coherence tomography (OCT) signal. First, the signal back-scattered from the tissue surface is generally much stronger than that from positions in the tissue interior, so the spectral component of the surface interference could be extracted from the measured spectrum. Second, the tissue surface is not a plane and a phase difference exists between the light reflected from two different points on the surface. Compared with the zero-crossing automatic method, the introduced method has the advantage of removing the error due to dispersion mismatch or the common phase error. The method is tested experimentally to demonstrate the improved signal-to-noise ratio, higher axial resolution, and slower sensitivity degradation with depth when compared to the use of the zero-crossing method and applied to two-dimensional cross-sectional images of human finger skin.

Characteristics of light reflected from a dense ionization wave with a tunable velocity.

PubMed

Zhidkov, A; Esirkepov, T; Fujii, T; Nemoto, K; Koga, J; Bulanov, S V

2009-11-20

An optically dense ionization wave (IW) produced by two femtosecond (approximately 10/30 fs) laser pulses focused cylindrically and crossing each other may become an efficient coherent x-ray converter in accordance with the Semenova-Lampe theory. The resulting velocity of a quasiplane IW in the vicinity of pulse intersection changes with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing a tuning of the wavelength of x rays and their bunching. The x-ray spectra after scattering of a lower frequency and long coherent light pulse change from the monochromatic to high order harmoniclike with the duration of the ionizing pulses.

Production of plasmas by long-wavelength lasers

DOEpatents

Dawson, J.M.

1973-10-01

A long-wavelength laser system for heating low-density plasma to high temperatures is described. In one embodiment, means are provided for repeatedly receiving and transmitting long-wavelength laser light in successive stages to form a laser-light beam path that repeatedly intersects with the equilibrium axis of a magnetically confined toroidal plasma column for interacting the laser light with the plasma for providing controlled thermonuclear fusion. Embodiments for heating specific linear plasmas are also provided. (Official Gazette)

Generation and Amplification of Coherent Radiation with Optical Orbital Angular Momentum in a Free-Electron Laser

NASA Astrophysics Data System (ADS)

Hemsing, Erik Willard

The object of this work is to examine how coherent light that carries orbital angular momentum (OAM) can be generated and amplified in a single pass, high-gain free-electron laser (FEL) at the fundamental operating frequency. This concept unites two rapidly expanding, but at present largely non-overlapping fields of study: high-order OAM light modes, which interact in new ways with matter, and FELs, in which a relativistically energetic electron beam emits coherent, ultra high-brightness, highly frequency-tunable light. The ability to generate OAM light in an FEL enables new regimes of laser interaction physics to be explored at wavelengths down to hard x-rays. The theoretical portion of this dissertation attempts to provide a new predictive mathematical framework. It builds on existing work, and describes the three-dimensional electromagnetic field of the high-gain FEL as a sum of OAM modes such that the amplification properties of individual modes can be characterized. The effects of uncorrelated energy spread, longitudinal space charge, energy detuning, and transverse emittance in the electron beam are included, as is the diffraction of the laser light. Theoretical predictions are corroborated by detailed numerical Genesis 1.3 simulations. When the theory is extended to frequency harmonics, a novel interaction is uncovered that generates a helical electron beam density distribution. These predictions are also supported by numerical Tredi simulations. This type of highly correlated structure is shown to naturally emit OAM light, and forms the basis of a new high-gain, high-mode generation (HGHMG) scheme proposed in its entirety here. The experimental section examines the helical microbunching concept in a proof-of-principle experiment dubbed HELIX, performed at the UCLA Neptune laboratory. We present detailed measurement of the coherent transition radiation emitted by the 12.5 MeV electron beam that is microbunched in a second harmonic interaction with an input

Ultra-high-speed optical coherence tomography with a stretched pulse supercontinuum source.

PubMed

Moon, Sucbei; Kim, Dug Young

2006-11-27

We introduce a new high-speed Fourier-domain optical coherence tomography (FD-OCT) scheme based on a stretched pulse supercontinuum source. A wide-band short pulse of a supercontinuum source of which output spectrum spanned a wavelength range from 1,200 nm to 1,550 nm was stretched to a long pulse of 70-ns duration by using a dispersive fiber due to the group-velocity dispersion, and it was used directly as frequency-swept light for FD-OCT. The OCT spectral interferogram was acquired in the time domain and converted into the spectral domain by the pre-calibrated time-to-wavelength relation. Using this stretched-pulse OCT (SP-OCT) scheme, we have demonstrated an ultrahigh-speed axial-line scanning rate of 5 MHz. The axial resolution of 8 microm was achieved without re-calibration of the sweep characteristic owing to the passive nature of the frequency-sweeping mechanism.

Pupillary behavior in relation to wavelength and age

PubMed Central

Lobato-Rincón, Luis-Lucio; Cabanillas-Campos, Maria del Carmen; Bonnin-Arias, Cristina; Chamorro-Gutiérrez, Eva; Murciano-Cespedosa, Antonio; Sánchez-Ramos Roda, Celia

2014-01-01

Pupil light reflex can be used as a non-invasive ocular predictor of cephalic autonomic nervous system integrity. Spectral sensitivity of the pupil's response to light has, for some time, been an interesting issue. It has generally, however, only been investigated with the use of white light and studies with monochromatic wavelengths are scarce. This study investigates the effects of wavelength and age within three parameters of the pupil light reflex (amplitude of response, latency, and velocity of constriction) in a large sample of younger and older adults (N = 97), in mesopic conditions. Subjects were exposed to a single light stimulus at four different wavelengths: white (5600°K), blue (450 nm), green (510 nm), and red (600 nm). Data was analyzed appropriately, and, when applicable, using the General Linear Model (GLM), Randomized Complete Block Design (RCBD), Student's t-test and/or ANCOVA. Across all subjects, pupillary response to light had the greatest amplitude and shortest latency in white and green light conditions. In regards to age, older subjects (46–78 years) showed an increased latency in white light and decreased velocity of constriction in green light compared to younger subjects (18–45 years old). This study provides data patterns on parameters of wavelength-dependent pupil reflexes to light in adults and it contributes to the large body of pupillometric research. It is hoped that this study will add to the overall evaluation of cephalic autonomic nervous system integrity. PMID:24795595

Comparison of short-wavelength blue-light autofluorescence and conventional blue-light autofluorescence in geographic atrophy.

PubMed

Borrelli, Enrico; Nittala, Muneeswar Gupta; Abdelfattah, Nizar Saleh; Lei, Jianqin; Hariri, Amir H; Shi, Yue; Fan, Wenying; Cozzi, Mariano; Sarao, Valentina; Lanzetta, Paolo; Staurenghi, Giovanni; Sadda, SriniVas R

2018-06-05

To systematically compare the intermodality and inter-reader agreement for two blue-light confocal fundus autofluorescence (FAF) systems. Thirty eyes (21 patients) with a diagnosis of geographic atrophy (GA) were enrolled. Eyes were imaged using two confocal blue-light FAF devices: (1) Spectralis device with a 488 nm excitation wavelength (488-FAF); (2) EIDON device with 450 nm excitation wavelength and the capability for 'colour' FAF imaging including both the individual red and green components of the emission spectrum. Furthermore, a third imaging modality (450-RF image) isolating and highlighting the red emission fluorescence component (REFC) was obtained and graded. Each image was graded by two readers to assess inter-reader variability and a single image for each modality was used to assess the intermodality variability. The 95% coefficient of repeatability (1.35 mm 2 for the 488-FAF-based grading, 8.13 mm 2 for the 450-FAF-based grading and 1.08 mm 2 for the 450-RF-based grading), the coefficient of variation (1.11 for 488-FAF, 2.05 for 450-FAF, 0.92 for 450-RF) and the intraclass correlation coefficient (0.994 for 488-FAF, 0.711 for 450-FAF, 0.997 for 450-RF) indicated that 450-FAF-based and 450-RF-based grading have the lowest and highest inter-reader agreements, respectively. The GA area was larger for 488-FAF images (median (IQR) 2.1 mm 2  (0.8-6.4 mm 2 )) than for 450-FAF images (median (IQR) 1.0 mm 2  (0.3-4.3 mm 2 ); p<0.0001). There was no significant difference in lesion area measurement between 488-FAF-based and 450-RF-based grading (median (IQR) 2.6 mm 2  (0.8-6.8 mm 2 ); p=1.0). The isolation of the REFC from the 450-FAF images allowed for a reproducible quantification of GA. This assessment had good comparability with that obtained with 488-FAF images. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise

Single-mode 140 nm swept light source realized by using SSG-DBR lasers

NASA Astrophysics Data System (ADS)

Fujiwara, N.; Yoshimura, R.; Kato, K.; Ishii, H.; Kano, F.; Kawaguchi, Y.; Kondo, Y.; Ohbayashi, K.; Oohashi, H.

2008-02-01

We demonstrate a single-mode and fast wavelength swept light source by using Superestrucuture grating distributed Bragg reflector (SSG-DBR) lasers for use in optical frequency-domain reflectometry optical coherence tomography. The SSG-DBR lasers provide single-mode operation resulting in high coherency. Response of the wavelength tuning is very fast; several nanoseconds, but there was an unintentional wavelength drift resulting from a thermal drift due to injecting tuning current. The dri1ft unfortunately requires long time to converge; more than a few milliseconds. For suppressing the wavelength drift, we introduced Thermal Drift Compensation mesa (TDC) parallel to the laser mesa with the spacing of 20 μm. By controlling TDC current to satisfy the total electric power injected into both the laser mesa and the TDC mesa, the thermal drift can be suppressed. In the present work, we fabricated 4 wavelength's kinds of SSG-DBR laser, which covers respective wavelength band; S-band (1496-1529 nm), C-band (1529-1564 nm), L --band (1564-1601 nm), and L +-band (1601-1639). We set the frequency channel of each laser with the spacing 6.25 GHz and 700 channels. The total frequency channel number is 2800 channels (700 ch × 4 lasers). We simultaneously operated the 4 lasers with a time interval of 500 ns/channel. A wavelength tuning range of more than 140 nm was achieved within 350 μs. The output power was controlled to be 10 mW for all channels. A single-mode, accurate, wide, and fast wavelength sweep was demonstrated with the SSG-DBR lasers having TDC mesa structure for the first time.

Multi-kW coherent combining of fiber lasers seeded with pseudo random phase modulated light

NASA Astrophysics Data System (ADS)

Flores, Angel; Ehrehreich, Thomas; Holten, Roger; Anderson, Brian; Dajani, Iyad

2016-03-01

We report efficient coherent beam combining of five kilowatt-class fiber amplifiers with a diffractive optical element (DOE). Based on a master oscillator power amplifier (MOPA) configuration, the amplifiers were seeded with pseudo random phase modulated light. Each non-polarization maintaining fiber amplifier was optically path length matched and provides approximately 1.2 kW of near diffraction-limited output power (measured M2<1.1). Consequently, a low power sample of each laser was utilized for active linear polarization control. A low power sample of the combined beam after the DOE provided an error signal for active phase locking which was performed via Locking of Optical Coherence by Single-Detector Electronic-Frequency Tagging (LOCSET). After phase stabilization, the beams were coherently combined via the 1x5 DOE. A total combined output power of 4.9 kW was achieved with 82% combining efficiency and excellent beam quality (M2<1.1). The intrinsic DOE splitter loss was 5%. Similarly, losses due in part to non-ideal polarization, ASE content, uncorrelated wavefront errors, and misalignment errors contributed to the efficiency reduction.

Coherent control schemes for the photoionization of neon and helium in the Extreme Ultraviolet spectral region.

PubMed

Giannessi, Luca; Allaria, Enrico; Prince, Kevin C; Callegari, Carlo; Sansone, Giuseppe; Ueda, Kiyoshi; Morishita, Toru; Liu, Chien Nan; Grum-Grzhimailo, Alexei N; Gryzlova, Elena V; Douguet, Nicolas; Bartschat, Klaus

2018-05-17

The seeded Free-Electron Laser (FEL) FERMI is the first source of short-wavelength light possessing the full coherence of optical lasers, together with the extreme power available from FELs. FERMI provides longitudinally coherent radiation in the Extreme Ultraviolet and soft x-ray spectral regions, and therefore opens up wide new fields of investigation in physics. We first propose experiments exploiting this property to provide coherent control of the photoionization of neon and helium, carry out numerical calculations to find optimum experimental parameters, and then describe how these experiments may be realized. The approach uses bichromatic illumination of a target and measurement of the products of the interaction, analogous to previous Brumer-Shapiro-type experiments in the optical spectral range. We describe operational schemes for the FERMI FEL, and simulate the conditions necessary to produce light at the fundamental and second or third harmonic frequencies, and to control the phase with respect to the fundamental. We conclude that a quantitative description of the phenomena is extremely challenging for present state-of-the-art theoretical and computational methods, and further development is necessary. Furthermore, the intensity available may already be excessive for the experiments proposed on helium. Perspectives for further development are discussed.

Investigations of soft and hard tissues in oral cavity by spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Madjarova, Violeta Dimitrova; Yasuno, Yoshiaki; Makita, Shuichi; Hori, Yasuaki; Voeffray, Jean-Baptiste; Itoh, Masahide; Yatagai, Toyohiko; Tamura, Masami; Nanbu, Toshiyuki

2006-02-01

Fourier Domain Optical Coherence Tomography (SD-OCT) systems for dental measurements are demonstrated. Two systems have been developed. The first system is fiber based Michelson interferometer with super luminescent diodes at 1310 nm and 100 nm FWHM as a light source. The sensitivity of the system was 106 dB with depth measurement range in air of 2.5 mm. The second systems is a fiber based Mach-Zehnder interferometer with wavelength scanning laser as light source at center wavelength of 1310 nm, wavelength range of 110 nm and scanning rate of 20 KHz. The sensitivity of the system is 112 dB and depth measurement range in air is 6 mm. Both systems can acquire real-time three dimensional (3-D) images in the range of several second. The systems were applied for early caries detection in tooth, for diagnostics of tooth condition after operational tooth treatment, and for diagnostics of the alveolar bone structure. In-vivo measurements were performed on two volunteers. The systems were able to detect discontinuities in tooth and resin filling after tooth treatment. In addition early carries lesion was detected in one of the volunteers. The 3-D profile of the alveolar bone was acquired for first time with non-contact method.

Discrete wavelength-locked external cavity laser

NASA Technical Reports Server (NTRS)

Pilgrim, Jeffrey S. (Inventor); Silver, Joel A. (Inventor)

2005-01-01

An external cavity laser (and method of generating laser light) comprising: a laser light source; means for collimating light output by the laser light source; a diffraction grating receiving collimated light; a cavity feedback mirror reflecting light received from the diffraction grating back to the diffraction grating; and means for reliably tuning the external cavity laser to discrete wavelengths.

The affect of low-coherent light on microbial colony forming ability and morphology of some gram-positive and gram-negative bacteria

NASA Astrophysics Data System (ADS)

Popov, Denis E.; Tuchina, Elena S.; Chernova, Julia A.; Podshibyakin, Dmitry; Rudik, Dmitry V.; Samsonova, Maria; Gromov, Igor; Tuchin, Valery V.

2005-06-01

Gram-negative E. coli, gram-positive facultative anaerobe cocci Staphylococcus lugdensis, Micrococcus halobius, and Stomatococcus mucilaginosus as subjects of study were chosen. LEDs with spectrum maxima at 405 nm (without any exogenous sensitizer) and 660 nm (in conjunction with methylene blue) and power densities of 23 mW/cm2 and 5.7 mW/cm2 accordingly as continuous light sources were chosen. Photosensitized light's affect by methylene blue was studied on E. coli only. The original scheme of experiment set up was developed. It permits one to increase expositions quantity in each experiment for more certain trend's construction over dose curves and decrease parasite flora sowing. As a result of accomplished studies it was established that blue low-coherent light have unalike weak light's dose depending suppressing effect on cocci whereas red low-coherent light have a moderate dose-depended suppressing effect at low irradiation doses and a moderate dose-depended stimulating effect at high irradiation doses on sensitized by MeBlue E. coli. For all ofthis, but Staphylococcus morphology changes were observed.

Large area full-field optical coherence tomography using white light source

NASA Astrophysics Data System (ADS)

Chang, Shoude; Mao, Youxin; Sherif, Sherif; Flueraru, Costel

2007-06-01

Optical coherence tomography (OCT) is an emerging technology for high-resolution cross-sectional imaging of 3D structures. Not only could OCT extract the internal features of an object, but it could acquire the 3D profile of an object as well. Hence it has huge potentials for industrial applications. Owing to non-scanning along the X-Y axis, full-field OCT could be the simplest and most economic imaging system, especially for applications where the speed is critical. For an OCT system, the performance and cost basically depends on the light source being used. The broader the source bandwidth, the finer of the depth resolution that could be reached; the more power of the source, the better signal-to-noise ratio and the deeper of penetration the system achieves. A typical SLD (Superluminescent Diode) light source has a bandwidth of 15 nm and 10 mW optical power at a price around 6,000. However, a Halogen bulb having 50W power and 200nm bandwidth only costs less than 10. The design and implementation of a large-area, full-field OCT system using Halogen white-light source is described in the paper. The experimental results obtained from 3D shaping and multiple-layer tomographies are also presented.

High power CO2 coherent ladar haven't quit the stage of military affairs

NASA Astrophysics Data System (ADS)

Zhang, Heyong

2015-05-01

The invention of the laser in 1960 created the possibility of using a source of coherent light as a transmitter for a laser radar (ladar). Coherent ladar shares many of the basic features of more common microwave radars. However, it is the extremely short operating wavelength of lasers that introduces new military applications, especially in the area of missile identification, space target tracking, remote rang finding, camouflage discrimination and toxic agent detection. Therefore, the most popular application field such as laser imaging and ranging were focused on CO2 laser in the last few decades. But during the development of solid state and fiber laser, some people said that the CO2 laser will be disappeared and will be replaced by the solid and fiber laser in the field of military and industry. The coherent CO2 laser radar will have the same destiny in the field of military affairs. However, to my opinion, the high power CO2 laser will be the most important laser source for laser radar and countermeasure in the future.

Using UVC Light-Emitting Diodes at Wavelengths of 266 to 279 Nanometers To Inactivate Foodborne Pathogens and Pasteurize Sliced Cheese

PubMed Central

Kim, Soo-Ji; Kim, Do-Kyun

2015-01-01

UVC light is a widely used sterilization technology. However, UV lamps have several limitations, including low activity at refrigeration temperatures, a long warm-up time, and risk of mercury exposure. UV-type lamps only emit light at 254 nm, so as an alternative, UV light-emitting diodes (UV-LEDs) which can produce the desired wavelengths have been developed. In this study, we validated the inactivation efficacy of UV-LEDs by wavelength and compared the results to those of conventional UV lamps. Selective media inoculated with Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes were irradiated using UV-LEDs at 266, 270, 275, and 279 nm in the UVC spectrum at 0.1, 0.2, 0.5, and 0.7 mJ/cm2, respectively. The radiation intensity of the UV-LEDs was about 4 μW/cm2, and UV lamps were covered with polypropylene films to adjust the light intensity similar to those of UV-LEDs. In addition, we applied UV-LED to sliced cheese at doses of 1, 2, and 3 mJ/cm2. Our results showed that inactivation rates after UV-LED treatment were significantly different (P < 0.05) from those of UV lamps at a similar intensity. On microbiological media, UV-LED treatments at 266 and 270 nm showed significantly different (P < 0.05) inactivation effects than other wavelength modules. For sliced cheeses, 4- to 5-log reductions occurred after treatment at 3 mJ/cm2 for all three pathogens, with negligible generation of injured cells. PMID:26386061

Demonstration of simultaneous experiments using thin crystal multiplexing at the Linac Coherent Light Source

DOE PAGES

Feng, Y.; Alonso-Mori, R.; Barends, T. R. M.; ...

2015-04-10

Multiplexing of the Linac Coherent Light Source beam was demonstrated for hard X-rays by spectral division using a near-perfect diamond thin-crystal monochromator operating in the Bragg geometry. The wavefront and coherence properties of both the reflected and transmitted beams were well preserved, thus allowing simultaneous measurements at two separate instruments. In this report, the structure determination of a prototypical protein was performed using serial femtosecond crystallography simultaneously with a femtosecond time-resolved XANES studies of photoexcited spin transition dynamics in an iron spin-crossover system. The results of both experiments using the multiplexed beams are similar to those obtained separately, using amore » dedicated beam, with no significant differences in quality.« less

Stationary light pulse in solids with long-lived spin coherence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Xiaojun; Wang Haihua; Wang Lei

We present a detailed analysis of stationary light pulses (SLP's) for the case of inhomogeneous broadening in both optical and spin transitions, which is normally found in solid materials with long-lived spin coherence. By solving the Langevin equations of motion for the density matrix elements under the integral over the entire range of the inhomogeneous broadenings, the necessary conditions for creating the SLP in a solid are obtained. Then the decay and diffusion processes that the SLP undergoes are analyzed. The characteristics of such processes are studied based on the analytic solution of the SLP with a slowly varying envelope.more » The dependence of SLP lifetime on inhomogeneous broadenings of spin and optical transitions, which can be regarded as the laser linewidth in the repump scheme, has been discussed.« less

Lineshape analysis of coherent multidimensional optical spectroscopy using incoherent light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulness, Darin J.; Turner, Daniel B., E-mail: dturner@nyu.edu

2015-06-07

Coherent two-dimensional electronic spectroscopy using incoherent (noisy) light, I{sup (4)} 2D ES, holds intriguing challenges and opportunities. One challenge is to determine how I{sup (4)} 2D ES compares to femtosecond 2D ES. Here, we merge the sophisticated energy-gap Hamiltonian formalism that is often used to model femtosecond 2D ES with the factorized time-correlation formalism that is needed to describe I{sup (4)} 2D ES. The analysis reveals that in certain cases the energy-gap Hamiltonian is insufficient to model the spectroscopic technique correctly. The results using a modified energy-gap Hamiltonian show that I{sup (4)} 2D ES can reveal detailed lineshape information, but,more » contrary to prior reports, does not reveal dynamics during the waiting time.« less

Short-wavelength light beam in situ monitoring growth of InGaN/GaN green LEDs by MOCVD

PubMed Central

2012-01-01

In this paper, five-period InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) were grown by metal organic chemical vapor deposition with 405-nm light beam in situ monitoring system. Based on the signal of 405-nm in situ monitoring system, the related information of growth rate, indium composition and interfacial quality of each InGaN/GaN QW were obtained, and thus, the growth conditions and structural parameters were optimized to grow high-quality InGaN/GaN green LED structure. Finally, a green LED with a wavelength of 509 nm was fabricated under the optimal parameters, which was also proved by ex situ characterization such as high-resolution X-ray diffraction, photoluminescence, and electroluminescence. The results demonstrated that short-wavelength in situ monitoring system was a quick and non-destroyed tool to provide the growth information on InGaN/GaN, which would accelerate the research and development of GaN-based green LEDs. PMID:22650991

Selenium single-wavelength anomalous diffraction de novo phasing using an X-ray-free electron laser

DOE PAGES

Hunter, Mark S.; Yoon, Chun Hong; DeMirci, Hasan; ...

2016-11-04

Structural information about biological macromolecules near the atomic scale provides important insight into the functions of these molecules. To date, X-ray crystallography has been the predominant method used for macromolecular structure determination. However, challenges exist when solving structures with X-rays, including the phase problem and radiation damage. X-ray-free electron lasers (X-ray FELs) have enabled collection of diffraction information before the onset of radiation damage, yet the majority of structures solved at X-ray FELs have been phased using external information via molecular replacement. De novo phasing at X-ray FELs has proven challenging due in part to per-pulse variations in intensity andmore » wavelength. Here we report the solution of a selenobiotinyl-streptavidin structure using phases obtained by the anomalous diffraction of selenium measured at a single wavelength (Se-SAD) at the Linac Coherent Light Source. Finally, our results demonstrate Se-SAD, routinely employed at synchrotrons for novel structure determination, is now possible at X-ray FELs.« less

Fabrication of a nano-cone array on a p-GaN surface for enhanced light extraction efficiency from GaN-based tunable wavelength LEDs.

PubMed

Soh, C B; Wang, B; Chua, S J; Lin, Vivian K X; Tan, Rayson J N; Tripathy, S

2008-10-08

We report on the fabrication of a nano-cone structured p-GaN surface for enhanced light extraction from tunable wavelength light emitting diodes (LEDs). Prior to p-contact metallization, self-assembled colloidal particles are deposited and used as a mask for plasma etching to create nano-cone structures on the p-GaN layer of LEDs. A well-defined periodic nano-cone array, with an average cone diameter of 300 nm and height of 150 nm, is generated on the p-GaN surface. The photoluminescence emission intensity recorded from the regions with the nano-cone array is increased by two times as compared to LEDs without surface patterning. The light output power from the LEDs with surface nano-cones shows significantly higher electroluminescence intensity at an injection current of 70 mA. This is due to the internal multiple scattering of light from the nano-cone sidewalls. Furthermore, we have shown that with an incorporation of InGaN nanostructures in the quantum well, the wavelength of these surface-patterned LEDs can be tuned from 517 to 488 nm with an increase in the injection current. This methodology may serve as a practical approach to increase the light extraction efficiency from wavelength tunable LEDs.

Coherent properties of a tunable low-energy electron-matter-wave source

NASA Astrophysics Data System (ADS)

Pooch, A.; Seidling, M.; Kerker, N.; Röpke, R.; Rembold, A.; Chang, W. T.; Hwang, I. S.; Stibor, A.

2018-01-01

A general challenge in various quantum experiments and applications is to develop suitable sources for coherent particles. In particular, recent progress in microscopy, interferometry, metrology, decoherence measurements, and chip-based applications rely on intensive, tunable, coherent sources for free low-energy electron-matter waves. In most cases, the electrons get field emitted from a metal nanotip, where its radius and geometry toward a counter electrode determines the field distribution and the emission voltage. A higher emission is often connected to faster electrons with smaller de Broglie wavelengths, requiring larger pattern magnification after matter-wave diffraction or interferometry. This can be prevented with a well-known setup consisting of two counter electrodes that allow independent setting of the beam intensity and velocity. However, it needs to be tested if the coherent properties of such a source are preserved after the acceleration and deceleration of the electrons. Here, we study the coherence of the beam in a biprism interferometer with a single atom tip electron field emitter if the particle velocity and wavelength varies after emission. With a Wien filter measurement and a contrast correlation analysis we demonstrate that the intensity of the source at a certain particle wavelength can be enhanced up to a factor of 6.4 without changing the transverse and longitudinal coherence of the electron beam. In addition, the energy width of the single atom tip emitter was measured to be 377 meV, corresponding to a longitudinal coherence length of 82 nm. The design has potential applications in interferometry, microscopy, and sensor technology.

Planarian Phototactic Assay Reveals Differential Behavioral Responses Based on Wavelength.

PubMed

Paskin, Taylor R; Jellies, John; Bacher, Jessica; Beane, Wendy S

2014-01-01

Planarians are free-living aquatic flatworms that possess a well-documented photophobic response to light. With a true central nervous system and simple cerebral eyes (ocelli), planarians are an emerging model for regenerative eye research. However, comparatively little is known about the physiology of their photoreception or how their behavior is affected by various wavelengths. Most phototactic studies have examined planarian behavior using white light. Here, we describe a novel planarian behavioral assay to test responses to small ranges of visible wavelengths (red, blue, green), as well as ultraviolet (UV) and infrared (IR) which have not previously been examined. Our data show that planarians display behavioral responses across a range of wavelengths. These responses occur in a hierarchy, with the shortest wavelengths (UV) causing the most intense photophobic responses while longer wavelengths produce no effect (red) or an apparent attraction (IR). In addition, our data reveals that planarian photophobia is comprised of both a general photophobic response (that drives planarians to escape the light source regardless of wavelength) and wavelength-specific responses that encompass specific behavioral reactions to individual wavelengths. Our results serve to improve the understanding of planarian phototaxis and suggest that behavioral studies performed with white light mask a complex behavioral interaction with the environment.

Propagation of coherent light pulses with PHASE

NASA Astrophysics Data System (ADS)

Bahrdt, J.; Flechsig, U.; Grizzoli, W.; Siewert, F.

2014-09-01

The current status of the software package PHASE for the propagation of coherent light pulses along a synchrotron radiation beamline is presented. PHASE is based on an asymptotic expansion of the Fresnel-Kirchhoff integral (stationary phase approximation) which is usually truncated at the 2nd order. The limits of this approximation as well as possible extensions to higher orders are discussed. The accuracy is benchmarked against a direct integration of the Fresnel-Kirchhoff integral. Long range slope errors of optical elements can be included by means of 8th order polynomials in the optical element coordinates w and l. Only recently, a method for the description of short range slope errors has been implemented. The accuracy of this method is evaluated and examples for realistic slope errors are given. PHASE can be run either from a built-in graphical user interface or from any script language. The latter method provides substantial flexibility. Optical elements including apertures can be combined. Complete wave packages can be propagated, as well. Fourier propagators are included in the package, thus, the user may choose between a variety of propagators. Several means to speed up the computation time were tested - among them are the parallelization in a multi core environment and the parallelization on a cluster.

Can short-wavelength depleted bright light during single simulated night shifts prevent circadian phase shifts?

PubMed

Regente, J; de Zeeuw, J; Bes, F; Nowozin, C; Appelhoff, S; Wahnschaffe, A; Münch, M; Kunz, D

2017-05-01

In single night shifts, extending habitual wake episodes leads to sleep deprivation induced decrements of performance during the shift and re-adaptation effects the next day. We investigated whether short-wavelength depleted (=filtered) bright light (FBL) during a simulated night shift would counteract such effects. Twenty-four participants underwent a simulated night shift in dim light (DL) and in FBL. Reaction times, subjective sleepiness and salivary melatonin concentrations were assessed during both nights. Daytime sleep was recorded after both simulated night shifts. During FBL, we found no melatonin suppression compared to DL, but slightly faster reaction times in the second half of the night. Daytime sleep was not statistically different between both lighting conditions (n = 24) and there was no significant phase shift after FBL (n = 11). To conclude, our results showed positive effects from FBL during simulated single night shifts which need to be further tested with larger groups, in more applied studies and compared to standard lighting. Copyright © 2016 Elsevier Ltd. All rights reserved.

Coherent startup of an infrared free-electron laser

NASA Astrophysics Data System (ADS)

Jaroszynski, D. A.; Bakker, R. J.; van der Meer, A. F. G.; Oepts, D.; van Amersfoort, P. W.

1993-12-01

Coherent enhancement of the spontaneous undulator radiation by several orders of magnitude has been observed in a free-electron laser at wavelengths from 40 to 100 μm. The coherent emission can be explained by details of the electron-beam micropulse structure. Furthermore, it has been found that the phase of the optical micropulses is fixed by the electron pulse structure and that the coherence extends over successive optical micropulses, which gives rise to interference effects as a function of the optical cavity length in a laser oscillator.

The Atomic, Molecular and Optical Science instrument at the Linac Coherent Light Source

DOE PAGES

Ferguson, Ken R.; Bucher, Maximilian; Bozek, John D.; ...

2015-05-01

The Atomic, Molecular and Optical Science (AMO) instrument at the Linac Coherent Light Source (LCLS) provides a tight soft X-ray focus into one of three experimental endstations. The flexible instrument design is optimized for studying a wide variety of phenomena requiring peak intensity. There is a suite of spectrometers and two photon area detectors available. An optional mirror-based split-and-delay unit can be used for X-ray pump–probe experiments. Recent scientific highlights illustrate the imaging, time-resolved spectroscopy and high-power density capabilities of the AMO instrument.

Progress in coherent laser radar

NASA Technical Reports Server (NTRS)

Vaughan, J. M.

1986-01-01

Considerable progress with coherent laser radar has been made over the last few years, most notably perhaps in the available range of high performance devices and components and the confidence with which systems may now be taken into the field for prolonged periods of operation. Some of this increasing maturity was evident at the 3rd Topical Meeting on Coherent Laser Radar: Technology and Applications. Topics included in discussions were: mesoscale wind fields, nocturnal valley drainage and clear air down bursts; airborne Doppler lidar studies and comparison of ground and airborne wind measurement; wind measurement over the sea for comparison with satellite borne microwave sensors; transport of wake vortices at airfield; coherent DIAL methods; a newly assembled Nd-YAG coherent lidar system; backscatter profiles in the atmosphere and wavelength dependence over the 9 to 11 micrometer region; beam propagation; rock and soil classification with an airborne 4-laser system; technology of a global wind profiling system; target calibration; ranging and imaging with coherent pulsed and CW system; signal fluctuations and speckle. Some of these activities are briefly reviewed.

Sub-cycle light transients for attosecond, X-ray, four-dimensional imaging

NASA Astrophysics Data System (ADS)

Fattahi, Hanieh

2016-10-01

This paper reviews the revolutionary development of ultra-short, multi-TW laser pulse generation made possible by current laser technology. The design of the unified laser architecture discussed in this paper, based on the synthesis of ultrabroadband optical parametric chirped-pulse amplifiers, promises to provide powerful light transients with electromagnetic forces engineerable on the electron time scale. By coherent combination of multiple amplifiers operating in different wavelength ranges, pulses with wavelength spectra extending from less than 1 ?m to more than 10 ?m, with sub-cycle duration at unprecedented peak and average power levels can be generated. It is shown theoretically that these light transients enable the efficient generation of attosecond X-ray pulses with photon flux sufficient to image, for the first time, picometre-attosecond trajectories of electrons, by means of X-ray diffraction and record the electron dynamics by attosecond spectroscopy. The proposed system leads to a tool with sub-atomic spatio-temporal resolution for studying different processes deep inside matter.

Automated high resolution full-field spatial coherence tomography for quantitative phase imaging of human red blood cells

NASA Astrophysics Data System (ADS)

Singla, Neeru; Dubey, Kavita; Srivastava, Vishal; Ahmad, Azeem; Mehta, D. S.

2018-02-01

We developed an automated high-resolution full-field spatial coherence tomography (FF-SCT) microscope for quantitative phase imaging that is based on the spatial, rather than the temporal, coherence gating. The Red and Green color laser light was used for finding the quantitative phase images of unstained human red blood cells (RBCs). This study uses morphological parameters of unstained RBCs phase images to distinguish between normal and infected cells. We recorded the single interferogram by a FF-SCT microscope for red and green color wavelength and average the two phase images to further reduced the noise artifacts. In order to characterize anemia infected from normal cells different morphological features were extracted and these features were used to train machine learning ensemble model to classify RBCs with high accuracy.

High-energy, 2µm laser transmitter for coherent wind LIDAR

NASA Astrophysics Data System (ADS)

Singh, Upendra N.; Yu, Jirong; Kavaya, Michael J.; Koch, Grady J.

2017-11-01

A coherent Doppler lidar at 2μm wavelength has been built with higher output energy (300 mJ) than previously available. The laser transmitter is based on the solid-state Ho:Tm:LuLiF, a NASA Langley Research Center invented laser material for higher extraction efficiency. This diode pumped injection seeded MOPA has a transform limited line width and diffraction limited beam quality. NASA Langley Research Center is developing coherent wind lidar transmitter technology at eye-safe wavelength for satellite-based observation of wind on a global scale. The ability to profile wind is a key measurement for understanding and predicting atmospheric dynamics and is a critical measurement for improving weather forecasting and climate modeling. We would describe the development and performance of an engineering hardened 2μm laser transmitter for coherent Doppler wind measurement from ground/aircraft/space platform.

Coherent optical transition radiation and self-amplified spontaneous emission generated by chicane-compressed electron beams

NASA Astrophysics Data System (ADS)

Lumpkin, A. H.; Dejus, R. J.; Sereno, N. S.

2009-04-01

Observations of strongly enhanced optical transition radiation (OTR) following significant bunch compression of photoinjector beams by a chicane have been reported during the commissioning of the Linac Coherent Light Source accelerator and recently at the Advanced Photon Source (APS) linac. These localized transverse spatial features involve signal enhancements of nearly a factor of 10 and 100 in the APS case at the 150-MeV and 375-MeV OTR stations, respectively. They are consistent with a coherent process seeded by noise and may be evidence of a longitudinal space charge microbunching instability which leads to coherent OTR emissions. Additionally, we suggest that localized transverse structure in the previous self-amplified spontaneous emission (SASE) free-electron laser (FEL) data at APS in the visible regime as reported at FEL02 may be attributed to such beam structure entering the FEL undulators and inducing the SASE startup at those “prebunched” structures. Separate beam structures 120 microns apart in x and 2.9 nm apart in wavelength were reported. The details of these observations and operational parameters will be presented.

Evaluation of dental enamel caries assessment using Quantitative Light Induced Fluorescence and Optical Coherence Tomography.

PubMed

Maia, Ana Marly Araújo; de Freitas, Anderson Zanardi; de L Campello, Sergio; Gomes, Anderson Stevens Leônidas; Karlsson, Lena

2016-06-01

An in vitro study of morphological alterations between sound dental structure and artificially induced white spot lesions in human teeth, was performed through the loss of fluorescence by Quantitative Light-Induced Fluorescence (QLF) and the alterations of the light attenuation coefficient by Optical Coherence Tomography (OCT). To analyze the OCT images using a commercially available system, a special algorithm was applied, whereas the QLF images were analyzed using the software available in the commercial system employed. When analyzing the sound region against white spot lesions region by QLF, a reduction in the fluorescence intensity was observed, whilst an increase of light attenuation by the OCT system occurred. Comparison of the percentage of alteration between optical properties of sound and artificial enamel caries regions showed that OCT processed images through the attenuation of light enhanced the tooth optical alterations more than fluorescence detected by QLF System. QLF versus OCT imaging of enamel caries: a photonics assessment. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced UV light detection using a p-terphenyl wavelength shifter

NASA Astrophysics Data System (ADS)

Joosten, S.; Kaczanowicz, E.; Ungaro, M.; Rehfuss, M.; Johnston, K.; Meziani, Z.-E.

2017-10-01

UV-glass photomultiplier tubes (PMTs) have poor photon detection efficiency for wavelengths below 300 nm due to the opaqueness of the window material. Costly quartz PMTs could be used to enhance the efficiency below 300 nm. A less expensive solution that dramatically improves this efficiency is the application of a thin film of a p-terphenyl (PT) wavelength shifter on UV-glass PMTs. This improvement was quantified for Photonis XP4500B PMTs for wavelengths between 200 nm and 400 nm. The gain factor ranges up to 5 . 4 ± 0 . 5 at a wavelength of 215 nm, with a material load of 110 ± 10 μg /cm2 (894 nm). The wavelength shifter was found to be fully transparent for wavelengths greater than 300 nm. The resulting gain in detection efficiency, when used in a typical C̆erenkov counter, was estimated to be of the order of 40%. Consistent coating quality was assured by a rapid gain testing procedure using narrow-band UV LEDs. Based on these results, 200 Photonis XP4500B PMTs were treated with PT for the upgraded low-threshold C̆erenkov counter (LTCC) to be used in the CEBAF Large Acceptance Spectrometer upgraded detector (CLAS12) at the Thomas Jefferson National Accelerator Facility.

Solid-state lasers for coherent communication and remote sensing

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1990-01-01

Laser development, high efficiency, high power second harmonic generation, operation of optical parametric oscillators for wavelength diversity and tunability, and studies in coherent communications are reviewed.

Fast interaction of atoms with crystal surfaces: coherent lighting

NASA Astrophysics Data System (ADS)

Gravielle, M. S.

2017-11-01

Quantum coherence of incident waves results essential for the observation of interference patterns in grazing incidence fast atom diffraction (FAD). In this work we investigate the influence of the impact energy and projectile mass on the transversal length of the surface area that is coherently illuminated by the atomic beam, after passing through a collimating aperture. Such a transversal coherence length controls the general features of the interference structures, being here derived by means of the Van Cittert-Zernike theorem. The coherence length is then used to build the initial coherent wave packet within the Surface Initial Value Representation (SIVR) approximation. The SIVR approach is applied to fast He and Ne atoms impinging grazingly on a LiF(001) surface along a low-indexed crystallographic direction. We found that with the same collimating setup, by varying the impact energy we would be able to control the interference mechanism that prevails in FAD patterns, switching between inter-cell and unit-cell interferences. These findings are relevant to use FAD spectra adequately as a surface analysis tool, as well as to choose the appropriate collimating scheme for the observation of interference effects in a given collision system.

Using UVC Light-Emitting Diodes at Wavelengths of 266 to 279 Nanometers To Inactivate Foodborne Pathogens and Pasteurize Sliced Cheese.

PubMed

Kim, Soo-Ji; Kim, Do-Kyun; Kang, Dong-Hyun

2016-01-01

UVC light is a widely used sterilization technology. However, UV lamps have several limitations, including low activity at refrigeration temperatures, a long warm-up time, and risk of mercury exposure. UV-type lamps only emit light at 254 nm, so as an alternative, UV light-emitting diodes (UV-LEDs) which can produce the desired wavelengths have been developed. In this study, we validated the inactivation efficacy of UV-LEDs by wavelength and compared the results to those of conventional UV lamps. Selective media inoculated with Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes were irradiated using UV-LEDs at 266, 270, 275, and 279 nm in the UVC spectrum at 0.1, 0.2, 0.5, and 0.7 mJ/cm(2), respectively. The radiation intensity of the UV-LEDs was about 4 μW/cm(2), and UV lamps were covered with polypropylene films to adjust the light intensity similar to those of UV-LEDs. In addition, we applied UV-LED to sliced cheese at doses of 1, 2, and 3 mJ/cm(2). Our results showed that inactivation rates after UV-LED treatment were significantly different (P < 0.05) from those of UV lamps at a similar intensity. On microbiological media, UV-LED treatments at 266 and 270 nm showed significantly different (P < 0.05) inactivation effects than other wavelength modules. For sliced cheeses, 4- to 5-log reductions occurred after treatment at 3 mJ/cm(2) for all three pathogens, with negligible generation of injured cells. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Propagation and scattering of vector light beam in turbid scattering medium

NASA Astrophysics Data System (ADS)

Doronin, Alexander; Milione, Giovanni; Meglinski, Igor; Alfano, Robert R.

2014-03-01

Due to its high sensitivity to subtle alterations in medium morphology the vector light beams have recently gained much attention in the area of photonics. This leads to development of a new non-invasive optical technique for tissue diagnostics. Conceptual design of the particular experimental systems requires careful selection of various technical parameters, including beam structure, polarization, coherence, wavelength of incident optical radiation, as well as an estimation of how the spatial and temporal structural alterations in biological tissues can be distinguished by variations of these parameters. Therefore, an accurate realistic description of vector light beams propagation within tissue-like media is required. To simulate and mimic the propagation of vector light beams within the turbid scattering media the stochastic Monte Carlo (MC) technique has been used. In current report we present the developed MC model and the results of simulation of different vector light beams propagation in turbid tissue-like scattering media. The developed MC model takes into account the coherent properties of light, the influence of reflection and refraction at the medium boundary, helicity flip of vortexes and their mutual interference. Finally, similar to the concept of higher order Poincaŕe sphere (HOPS), to link the spatial distribution of the intensity of the backscattered vector light beam and its state of polarization on the medium surface we introduced the color-coded HOPS.

Acousto-Optic–Based Wavelength-Comb-Swept Laser for Extended Displacement Measurements

PubMed Central

Park, Nam Su; Chun, Soo Kyung; Han, Ga-Hee; Kim, Chang-Seok

2017-01-01

We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic–based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R2 = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain. PMID:28362318

1 × 4 MMI visible light wavelength demultiplexer based on a GaN slot-waveguide structure

NASA Astrophysics Data System (ADS)

Shoresh, Tamir; Katanov, Nadav; Malka, Dror

2018-07-01

High transmission losses are the key problem that limits the performance of visible light communication systems, which work on wavelength division multiplexing (WDM) technology. To overcome this problem, we propose a novel design for a 1 × 4 optical demultiplexer based on the multimode interference in a slot-waveguide structure that operates at 547 nm, 559 nm, 566 nm, and 584 nm. Gallium nitride and silicon oxide were found to be excellent materials for the slot-waveguide structure. Simulation results showed that the proposed device can transmit four channels that work in the visible light range with a low transmission loss of 0.983-1.423 dB, crosstalk of 13.8-18.3 dB, and bandwidth of 1.8-3.2 nm. Thus, this device can be very useful in visible light networking systems, which work on the WDM technology.

A 12 GHz wavelength spacing multi-wavelength laser source for wireless communication systems

NASA Astrophysics Data System (ADS)

Peng, P. C.; Shiu, R. K.; Bitew, M. A.; Chang, T. L.; Lai, C. H.; Junior, J. I.

2017-08-01

This paper presents a multi-wavelength laser source with 12 GHz wavelength spacing based on a single distributed feedback laser. A light wave generated from the distributed feedback laser is fed into a frequency shifter loop consisting of 50:50 coupler, dual-parallel Mach-Zehnder modulator, optical amplifier, optical filter, and polarization controller. The frequency of the input wavelength is shifted and then re-injected into the frequency shifter loop. By re-injecting the shifted wavelengths multiple times, we have generated 84 optical carriers with 12 GHz wavelength spacing and stable output power. For each channel, two wavelengths are modulated by a wireless data using the phase modulator and transmitted through a 25 km single mode fiber. In contrast to previously developed schemes, the proposed laser source does not incur DC bias drift problem. Moreover, it is a good candidate for radio-over-fiber systems to support multiple users using a single distributed feedback laser.

Modeling of the Light Speckle Field Structure Inside a Multilayer Human Skin Tissue

NASA Astrophysics Data System (ADS)

Barun, V. V.; Dik, S. K.; Ivanov, A. P.; Abramovich, N. D.

2013-11-01

We present an analytic method and the results of investigating the characteristics of the interference pattern formed by multiply scattered light in a multilayer biological tissue of the type of human skin at the wavelengths of the visible and neat IR spectral regions under laser irradiation. Calculations were performed with the use of the known solutions of the equations of radiation transfer in the biotissue and the relation between the theory of propagation of light in a scattering medium and the coherence theory. The radial structure of the light field in the depth of the human skin formed by coherent and incoherent radiation depending on its biophysical parameters has been investigated. The characteristic sizes of speckles in each layer of the skin have been estimated. The biophysical factors connected with the volume concentration of blood in the dermis and the degree of its oxygenation influencing the contrast of the speckle pattern in the dermis have been discussed. The possibility of formulating and solving inverse problems of biomedical optics on the restoration of blood parameters from measurements of speckle characteristics has been shown.

Modern fibre-optic coherent lidars for remote sensing

NASA Astrophysics Data System (ADS)

Hill, Chris

2015-10-01

This paper surveys some growth areas in optical sensing that exploit near-IR coherent laser sources and fibreoptic hardware from the telecoms industry. Advances in component availability and performance are promising benefits in several military and commercial applications. Previous work has emphasised Doppler wind speed measurements and wind / turbulence profiling for air safety, with recent sharp increases in numbers of lidar units sold and installed, and with wider recognition that different lidar / radar wavebands can and should complement each other. These advances are also enabling fields such as microDoppler measurement of sub-wavelength vibrations and acoustic waves, including non-lineof- sight acoustic sensing in challenging environments. To shed light on these different applications we review some fundamentals of coherent detection, measurement probe volume, and parameter estimation - starting with familiar similarities and differences between "radar" and "laser radar". The consequences of changing the operating wavelength by three or four orders of magnitude - from millimetric or centimetric radar to a typical fibre-optic lidar working near 1.5 μm - need regular review, partly because of continuing advances in telecoms technology and computing. Modern fibre-optic lidars tend to be less complicated, more reliable, and cheaper than their predecessors; and they more closely obey the textbook principles of easily adjusted and aligned Gaussian beams. The behaviours of noises and signals, and the appropriate processing strategies, are as expected different for the different wavelengths and applications. For example, the effective probe volumes are easily varied (e.g. by translating a fibre facet) through six or eight orders of magnitude; as the average number of contributing scatterers varies, from <<1 through ~1 to >>1, we should review any assumptions about "many" scatterers and Gaussian statistics. Finally, some much older but still relevant scientific

Use of coupled wavelength ultraviolet light-emitting diodes for inactivation of bacteria in subsea oil-field injection water.

PubMed

Qiao, Yang; Chen, Daoyi; Wen, Diya

2018-06-04

The development of subsea injection water disinfection systems will enable the novel exploration of offshore oilfields. Ultraviolet light emitting diodes (UV-LEDs) with peak wavelengths at 255 nm, 280 nm, 350 nm, and combinations of 255 nm and 350 nm, and 280 nm and 350 nm were investigated in this study to determine their efficiency at disinfecting saprophytic bacteria, iron bacteria, and sulfate reducing bacteria. Results show that UV-LEDs with peak wavelengths at 280 nm were the most practical in this domain because of their high performance in both energy-efficiency and reactivation suppression, although 255 nm UV-LEDs achieved an optimal germicidal effect in dose-based experiments. The use of combined 280 nm and 350 nm wavelengths also induced synergistic bactericidal effects on saprophytic bacteria. Copyright © 2018. Published by Elsevier B.V.

Mechanism of wavelength conversion in polystyrene doped with benzoxanthene: emergence of a complex.

PubMed

Nakamura, Hidehito; Shirakawa, Yoshiyuki; Kitamura, Hisashi; Sato, Nobuhiro; Shinji, Osamu; Saito, Katashi; Takahashi, Sentaro

2013-01-01

Fluorescent guest molecules doped in polymers have been used to convert ultraviolet light into visible light for applications ranging from optical fibres to filters for the cultivation of plants. The wavelength conversion process involves the absorption of light at short wavelengths followed by fluorescence emission at a longer wavelength. However, a precise understanding of the light conversion remains unclear. Here we show light responses for a purified polystyrene base substrates doped with fluorescent benzoxanthene in concentrations varied over four orders of magnitude. The shape of the excitation spectrum for fluorescence emission changes significantly with the concentration of the benzoxanthene, indicating formation of a base substrate/fluorescent molecule complex. Furthermore, the wavelength conversion light yield increases in three stages depending on the nature of the complex. These findings identify a mechanism that will have many applications in wavelength conversion materials.

Mechanism of wavelength conversion in polystyrene doped with benzoxanthene: emergence of a complex

PubMed Central

Nakamura, Hidehito; Shirakawa, Yoshiyuki; Kitamura, Hisashi; Sato, Nobuhiro; Shinji, Osamu; Saito, Katashi; Takahashi, Sentaro

2013-01-01

Fluorescent guest molecules doped in polymers have been used to convert ultraviolet light into visible light for applications ranging from optical fibres to filters for the cultivation of plants. The wavelength conversion process involves the absorption of light at short wavelengths followed by fluorescence emission at a longer wavelength. However, a precise understanding of the light conversion remains unclear. Here we show light responses for a purified polystyrene base substrates doped with fluorescent benzoxanthene in concentrations varied over four orders of magnitude. The shape of the excitation spectrum for fluorescence emission changes significantly with the concentration of the benzoxanthene, indicating formation of a base substrate/fluorescent molecule complex. Furthermore, the wavelength conversion light yield increases in three stages depending on the nature of the complex. These findings identify a mechanism that will have many applications in wavelength conversion materials. PMID:23974205

A comprehensive comparable study of the physiological properties of four microalgal species under different light wavelength conditions.

PubMed

Zhong, Yu; Jin, Peng; Cheng, Jay J

2018-05-19

Microalgae treated with blue light have potential for production of human nutrition supplement and biofuel due to their higher biomass productivity and favorable fatty acid composition. Chlorella vulgaris, Chlorella pyrenoidosa, Scenedesmus quadricauda and Scenedesmus obliquus are representative green microalgae which are widely reported for algal production. In this study, we provide a systematic investigation of the biomass productivity, photosynthetic pigments, chlorophyll fluorescence and fatty acid content of the four green microalgae. The strains were grown in two primary monochromatic light wavelengths [red and blue LEDs (light emitting diode)], and in white LED conditions, respectively. Among them, blue LED light was determined as the best light for growth rate, followed by red LED and white LED. The chlorophyll generation was more sensitive to the monochromatic blue light. The polyunsaturated fatty acids (PUFAs) such as α-linolenic acid (18:3), which were perfect for human nutrition supplementation, showed high concentrations in these algae strains under blue LED. Collectively, the results indicate that the blue LED is suitable for various food, feed, and algal biofuel productions due to both biomass and fatty acid productivity.

Human phase response curve to a single 6.5 h pulse of short-wavelength light

PubMed Central

Rüger, Melanie; St Hilaire, Melissa A; Brainard, George C; Khalsa, Sat-Bir S; Kronauer, Richard E; Czeisler, Charles A; Lockley, Steven W

2013-01-01

The photic resetting response of the human circadian pacemaker depends on the timing of exposure, and the direction and magnitude of the resulting shift is described by a phase response curve (PRC). Previous PRCs in humans have utilized high-intensity polychromatic white light. Given that the circadian photoreception system is maximally sensitive to short-wavelength visible light, the aim of the current study was to construct a PRC to blue (480 nm) light and compare it to a 10,000 lux white light PRC constructed previously using a similar protocol. Eighteen young healthy participants (18–30 years) were studied for 9–10 days in a time-free environment. The protocol included three baseline days followed by a constant routine (CR) to assess initial circadian phase. Following this CR, participants were exposed to a 6.5 h 480 nm light exposure (11.8 μW cm−2, 11.2 lux) following mydriasis via a modified Ganzfeld dome. A second CR was conducted following the light exposure to re-assess circadian phase. Phase shifts were calculated from the difference in dim light melatonin onset (DLMO) between CRs. Exposure to 6.5 h of 480 nm light resets the circadian pacemaker according to a conventional type 1 PRC with fitted maximum delays and advances of −2.6 h and 1.3 h, respectively. The 480 nm PRC induced ∼75% of the response of the 10,000 lux white light PRC. These results may contribute to a re-evaluation of dosing guidelines for clinical light therapy and the use of light as a fatigue countermeasure. PMID:23090946

Boosting the Light: X-ray Physics in Confinement

ScienceCinema

Rhisberger, Ralf [HASYLAB/ DESY

2017-12-09

Remarkable effects are observed if light is confined to dimensions comparable to the wavelength of the light. The lifetime of atomic resonances excited by the radiation is strongly reduced in photonic traps, such as cavities or waveguides. Moreover, one observes an anomalous boost of the intensity scattered from the resonant atoms. These phenomena results from the strong enhancement of the photonic density of states in such geometries. Many of these effects are currently being explored in the regime of vsible light due to their relevance for optical information processing. It is thus appealing to study these phenomena also for much shorter wavelengths. This talk illuminates recent experiments where synchrotron x-rays were trapped in planar waveguides to resonantly excite atomos ([57]Fe nuclei_ embedded in them. In fact, one observes that the radiative decay of these excited atoms is strongly accelerated. The temporal acceleration of the decay goes along with a strong boost of the radiation coherently scattered from the confined atmos. This can be exploited to obtain a high signal-to-noise ratio from tiny quantities of material, leading to manifold applications in the investigation of nanostructured materials. One application is the use of ultrathin probe layers to image the internal structure of magnetic layer systems.

Imaging Foveal Microvasculature: Optical Coherence Tomography Angiography Versus Adaptive Optics Scanning Light Ophthalmoscope Fluorescein Angiography.

PubMed

Mo, Shelley; Krawitz, Brian; Efstathiadis, Eleni; Geyman, Lawrence; Weitz, Rishard; Chui, Toco Y P; Carroll, Joseph; Dubra, Alfredo; Rosen, Richard B

2016-07-01

To compare the use of optical coherence tomography angiography (OCTA) and adaptive optics scanning light ophthalmoscope fluorescein angiography (AOSLO FA) for characterizing the foveal microvasculature in healthy and vasculopathic eyes. Four healthy controls and 11 vasculopathic patients (4 diabetic retinopathy, 4 retinal vein occlusion, and 3 sickle cell retinopathy) were imaged with OCTA and AOSLO FA. Foveal perfusion maps were semiautomatically skeletonized for quantitative analysis, which included foveal avascular zone (FAZ) metrics (area, perimeter, acircularity index) and vessel density in three concentric annular regions of interest. On each set of OCTA and AOSLO FA images, matching vessel segments were used for lumen diameter measurement. Qualitative image comparisons were performed by visual identification of microaneurysms, vessel loops, leakage, and vessel segments. Adaptive optics scanning light ophthalmoscope FA and OCTA showed no statistically significant differences in FAZ perimeter, acircularity index, and vessel densities. Foveal avascular zone area, however, showed a small but statistically significant difference of 1.8% (P = 0.004). Lumen diameter was significantly larger on OCTA (mean difference 5.7 μm, P < 0.001). Microaneurysms, fine structure of vessel loops, leakage, and some vessel segments were visible on AOSLO FA but not OCTA, while blood vessels obscured by leakage were visible only on OCTA. Optical coherence tomography angiography is comparable to AOSLO FA at imaging the foveal microvasculature except for differences in FAZ area, lumen diameter, and some qualitative features. These results, together with its ease of use, short acquisition time, and avoidance of potentially phototoxic blue light, support OCTA as a tool for monitoring ocular pathology and detecting early disease.

Enhanced UV light detection using a p-terphenyl wavelength shifter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joosten, Sylvester J.; Kaczanowicz, Ed; Ungaro, Maurizio

Here, UV-glass photomultiplier tubes (PMTs) have poor photon detection efficiency for wavelengths belowmore » $$300\\,\\text{nm}$$ due to the opaqueness of the window material. Costly quartz PMTs could be used to enhance the efficiency below $$300\\,\\text{nm}$$. A less expensive solution that dramatically improves this efficiency is the application of a thin film of a p-terphenyl (PT) wavelength shifter on UV-glass PMTs. This improvement was quantified for Photonis XP4500B PMTs for wavelengths between $$200\\,\\text{nm}$$ and $$400\\,\\text{nm}$$. The gain factor ranges up to 5.4 $$\\pm$$ 0.5 at a wavelength of $$215\\,\\text{nm}$$, with a material load of $$110\\pm10\\,\\mu\\text{g}/\\text{cm}^2$$ ($$894\\,\\text{nm}$$). The wavelength shifter was found to be fully transparent for wavelengths greater than $$300\\,\\text{nm}$$. The resulting gain in detection efficiency, when used in a typical Cherenkov counter, was estimated to be of the order of 40%. Consistent coating quality was assured by a rapid gain testing procedure using narrow-band UV LEDs. Based on these results, 200 Photonis XP4500B PMTs were treated with PT for the upgraded low-threshold Cherenkov counter (LTCC) to be used in the CEBAF Large Acceptance Spectrometer upgraded detector (CLAS12) at the Thomas Jefferson National Accelerator Facility.« less

Enhanced UV light detection using a p-terphenyl wavelength shifter

DOE PAGES

Joosten, Sylvester J.; Kaczanowicz, Ed; Ungaro, Maurizio; ...

2017-07-25

Here, UV-glass photomultiplier tubes (PMTs) have poor photon detection efficiency for wavelengths belowmore » $$300\\,\\text{nm}$$ due to the opaqueness of the window material. Costly quartz PMTs could be used to enhance the efficiency below $$300\\,\\text{nm}$$. A less expensive solution that dramatically improves this efficiency is the application of a thin film of a p-terphenyl (PT) wavelength shifter on UV-glass PMTs. This improvement was quantified for Photonis XP4500B PMTs for wavelengths between $$200\\,\\text{nm}$$ and $$400\\,\\text{nm}$$. The gain factor ranges up to 5.4 $$\\pm$$ 0.5 at a wavelength of $$215\\,\\text{nm}$$, with a material load of $$110\\pm10\\,\\mu\\text{g}/\\text{cm}^2$$ ($$894\\,\\text{nm}$$). The wavelength shifter was found to be fully transparent for wavelengths greater than $$300\\,\\text{nm}$$. The resulting gain in detection efficiency, when used in a typical Cherenkov counter, was estimated to be of the order of 40%. Consistent coating quality was assured by a rapid gain testing procedure using narrow-band UV LEDs. Based on these results, 200 Photonis XP4500B PMTs were treated with PT for the upgraded low-threshold Cherenkov counter (LTCC) to be used in the CEBAF Large Acceptance Spectrometer upgraded detector (CLAS12) at the Thomas Jefferson National Accelerator Facility.« less

Transient quantum coherent response to a partially coherent radiation field.

PubMed

Sadeq, Zaheen S; Brumer, Paul

2014-02-21

The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turn-on and pulsed turn-on effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal "toy" model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.

Compact low crosstalk 1x2 wavelength selective switch architectures

NASA Astrophysics Data System (ADS)

Sumriddetchkajorn, Sarun; Chaitavon, Khunat

2005-02-01

Thin film filter (TF)-based 1x2 wavelength selective switch (WSS) architectures are introduced. Our key idea is to locate a movable mirror orientated at a desired angle close to the TF to switch the desired wavelength optical beams to the wanted switch ports. Our first proposed WSS is in the transmissive mode where the surfaces of the TF and the movable mirror are parallel to each other and it provides a moderate optical isolation. Another WSS structure is in reflective configuration in which the movable mirror is tilted with respect to the surface of the TF and when combined with the optical circulator leads to a very low optical coherent crosstalk. Our experiment using a commercially available TF and a movable mirror shows that our transmissive-mode WSS provides a -18.87 dB optical coherent crosstalk while a much improved < -53 dB optical coherent crosstalk can be obtained between the two switching ports in our reflective-mode WSS structure. Our reflective 1x2 WSS also gives a higher optical loss due to the use of an optical circulator. Low polarization dependent loss of < 0.1 dB is determined for both WSS structures.

Coherence properties of the radiation from FLASH

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2016-02-01

Free electron LASer in Hamburg is the first free electron laser user facility operating in the vacuum ultraviolet and soft X-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper, we present a theoretical analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach their maxima close to the free electron laser (FEL) saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that nonazimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability.

Spectrometer calibration for spectroscopic Fourier domain optical coherence tomography

PubMed Central

Szkulmowski, Maciej; Tamborski, Szymon; Wojtkowski, Maciej

2016-01-01

We propose a simple and robust procedure for Fourier domain optical coherence tomography (FdOCT) that allows to linearize the detected FdOCT spectra to wavenumber domain and, at the same time, to determine the wavelength of light for each point of detected spectrum. We show that in this approach it is possible to use any measurable physical quantity that has linear dependency on wavenumber and can be extracted from spectral fringes. The actual values of the measured quantity have no importance for the algorithm and do not need to be known at any stage of the procedure. As example we calibrate a spectral OCT spectrometer using Doppler frequency. The technique of spectral calibration can be in principle adapted to of all kind of Fourier domain OCT devices. PMID:28018723

All-optical photochromic spatial light modulators based on photoinduced electron transfer in rigid matrices

NASA Technical Reports Server (NTRS)

Beratan, David N. (Inventor); Perry, Joseph W. (Inventor)

1991-01-01

A single material (not a multi-element structure) spatial light modulator may be written to, as well as read out from, using light. The device has tailorable rise and hold times dependent on the composition and concentration of the molecular species used as the active components. The spatial resolution of this device is limited only by light diffraction as in volume holograms. The device may function as a two-dimensional mask (transmission or reflection) or as a three-dimensional volume holographic medium. This device, based on optically-induced electron transfer, is able to perform incoherent to coherent image conversion or wavelength conversion over a wide spectral range (ultraviolet, visible, or near-infrared regions).

Coherent x-ray diffraction

NASA Astrophysics Data System (ADS)

Pitney, John Allen

Conventional x-ray diffraction has historically been done under conditions such that the measured signal consists of an incoherent addition of scattering which is coherent only on a length scale determined by the properties of the beam. The result of the incoherent summation is a statistical averaging over the whole illuminated volume of the sample, which yields certain kinds of information with a high degree of precision and has been key to the success of x-ray diffraction in a variety of applications. Coherent x-ray scattering techniques, such as coherent x-ray diffraction (CXD) and x-ray intensity fluctuation spectroscopy (XIFS), attempt to reduce or eliminate any incoherent averaging so that specific, local structures couple to the measurement without being averaged out. In the case of XIFS, the result is analogous to dynamical light scattering, but with sensitivity to length scales less than 200 nm and time scales from 10-3 s to 103 s. When combined with phase retrieval, CXD represents an imaging technique with the penetration, in situ capabilities, and contrast mechanisms associated with x-rays and with a spatial resolution ultimately limited by the x-ray wavelength. In practice, however, the spatial resolution of CXD imaging is limited by exposure to about 100 A. This thesis describes CXD measurements of the binary alloy Cu3Au and the adaptation of phase retrieval methods for the reconstruction of real-space images of Cu3Au antiphase domains. The theoretical foundations of CXD are described in Chapter 1 as derived from the kinematical formulation for x-ray diffraction and from the temporal and spatial coherence of radiation. The antiphase domain structure of Cu 3Au is described, along with the associated reciprocal-space structure which is measured by CXD. CXD measurements place relatively stringent requirements on the coherence properties of the beam and on the detection mechanism of the experiment; these requirements and the means by which they have been

Investigation of black and brown carbon multiple-wavelength-dependent light absorption from biomass and fossil fuel combustion source emissions

Treesearch

Michael R. Olson; Mercedes Victoria Garcia; Michael A. Robinson; Paul Van Rooy; Mark A. Dietenberger; Michael Bergin; James Jay Schauer

2015-01-01

Quantification of the black carbon (BC) and brown carbon (BrC) components of source emissions is critical to understanding the impact combustion aerosols have on atmospheric light absorption. Multiple-wavelength absorption was measured from fuels including wood, agricultural biomass, coals, plant matter, and petroleum distillates in controlled combustion settings....

Coherent control in bulk and nanostructure semiconductors

NASA Astrophysics Data System (ADS)

Sipe, John E.; van Driel, Henry M.

1998-04-01

Laser light has been used as a probe of atoms, molecules, and solids since the invention of the laser. The use of laser light in a more active role, to modify and process surfaces, and initiate chemical reactions, followed shortly thereafter. But usually it is the intensity and the directionality of the laser light that is employed, not necessarily its coherence, and not particularly the fact that it has a well-defined phase. 'Coherence control' can be broadly understood as the set of processes whereby light modifies matter in a way that is critically dependent on the incident light beams possessing well-defined phases. While in a laser matter is manipulated to produce light of the desired properties, in coherent control light is manipulated -- in particular, its phase and intensity is adjusted -- to produce a material response of the desired type. Of the various coherent control processes that are currently being investigated, some involve a transition in the material medium from an initial state to a final state by two or more possible processes. With each of these is associated a quantum mechanical amplitude, and hence the probability for the transition can show interference effects between the two amplitudes, just as in the familiar two-slit interference experiment the probability for the electron to be observed at a given position involves a probability that is the square of the sum of two amplitudes. In quantum interference control (QUIC), the relative phase of the two amplitudes is adjusted by adjusting the relative phase of two polarizations of a single beam, or the relative phase of two beams at different frequencies. It is this particular type of coherent control that is of interest in this communication.

A phase coherence approach to estimating the spatial extent of earthquakes

NASA Astrophysics Data System (ADS)

Hawthorne, Jessica C.; Ampuero, Jean-Paul

2016-04-01

We present a new method for estimating the spatial extent of seismic sources. The approach takes advantage of an inter-station phase coherence computation that can identify co-located sources (Hawthorne and Ampuero, 2014). Here, however, we note that the phase coherence calculation can eliminate the Green's function and give high values only if both earthquakes are point sources---if their dimensions are much smaller than the wavelengths of the propagating seismic waves. By examining the decrease in coherence at higher frequencies (shorter wavelengths), we can estimate the spatial extents of the earthquake ruptures. The approach can to some extent be seen as a simple way of identifying directivity or variations in the apparent source time functions recorded at various stations. We apply this method to a set of well-recorded earthquakes near Parkfield, CA. We show that when the signal to noise ratio is high, the phase coherence remains high well above 50 Hz for closely spaced M<1.5 earthquake. The high-frequency phase coherence is smaller for larger earthquakes, suggesting larger spatial extents. The implied radii scale roughly as expected from typical magnitude-corner frequency scalings. We also examine a second source of high-frequency decoherence: spatial variation in the shape of the Green's functions. This spatial decoherence appears to occur on a similar wavelengths as the decoherence associated with the apparent source time functions. However, the variation in Green's functions can be normalized away to some extent by comparing observations at multiple components on a single station, which see the same apparent source time functions.

Towards combined optical coherence tomography and hyper-spectral imaging for gastrointestinal endoscopy

NASA Astrophysics Data System (ADS)

Attendu, Xavier; Crunelle, Camille; de Sivry-Houle, Martin Poinsinet; Maubois, Billie; Urbain, Joanie; Turrell, Chloe; Strupler, Mathias; Godbout, Nicolas; Boudoux, Caroline

2018-04-01

Previous works have demonstrated feasibility of combining optical coherence tomography (OCT) and hyper-spectral imaging (HSI) through a single double-clad fiber (DCF). In this proceeding we present the continued development of a system combining both modalities and capable of rapid imaging. We discuss the development of a rapidly scanning, dual-band, polygonal swept-source system which combines NIR (1260-1340 nm) and visible (450-800 nm) wavelengths. The NIR band is used for OCT imaging while visible light allows HSI. Scanning rates up to 24 kHz are reported. Furthermore, we present and discuss the fiber system used for light transport, delivery and collection, and the custom signal acquisition software. Key points include the use of a double-clad fiber coupler as well as important alignments and back-reflection management. Simultaneous and co-registered imaging with both modalities is presented in a bench-top system

High-Energy Density science at the Linac Coherent Light Source

NASA Astrophysics Data System (ADS)

Glenzer, S. H.; Fletcher, L. B.; Hastings, J. B.

2016-03-01

The Matter in Extreme Conditions end station at the Linac Coherent Light Source holds great promise for novel pump-probe experiments to make new discoveries in high- energy density science. In recent experiments we have demonstrated the first spectrally- resolved measurements of plasmons using a seeded 8-keV x-ray laser beam. Forward x-ray Thomson scattering spectra from isochorically heated solid aluminum show a well-resolved plasmon feature that is down-shifted in energy by 19 eV from the incident 8 keV elastic scattering feature. In this spectral range, the simultaneously measured backscatter spectrum shows no spectral features indicating observation of collective plasmon oscillations on a scattering length comparable to the screening length. This technique is a prerequisite for Thomson scattering measurements in compressed matter where the plasmon shift is a sensitive function of the free electron density and where the plasmon intensity provides information on temperature.

Start-to-end simulation of the shot-noise driven microbunching instability experiment at the Linac Coherent Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiang, J.; Ding, Y.; Emma, P.

The shot-noise driven microbunching instability can significantly degrade electron beam quality in x-ray free electron laser light sources. Experiments were carried out at the Linac Coherent Light Source (LCLS) to study this instability. Here in this paper, we present start-to-end simulations of the shot-noise driven microbunching instability experiment at the LCLS using the real number of electrons. The simulation results reproduce the measurements quite well. A microbunching self-heating mechanism is also illustrated in the simulation, which helps explain the experimental observation.

Start-to-end simulation of the shot-noise driven microbunching instability experiment at the Linac Coherent Light Source

DOE PAGES

Qiang, J.; Ding, Y.; Emma, P.; ...

2017-05-23

The shot-noise driven microbunching instability can significantly degrade electron beam quality in x-ray free electron laser light sources. Experiments were carried out at the Linac Coherent Light Source (LCLS) to study this instability. Here in this paper, we present start-to-end simulations of the shot-noise driven microbunching instability experiment at the LCLS using the real number of electrons. The simulation results reproduce the measurements quite well. A microbunching self-heating mechanism is also illustrated in the simulation, which helps explain the experimental observation.

Time-stretch microscopy based on time-wavelength sequence reconstruction from wideband incoherent source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chi, E-mail: chizheung@gmail.com; Xu, Yiqing; Wei, Xiaoming

2014-07-28

Time-stretch microscopy has emerged as an ultrafast optical imaging concept offering the unprecedented combination of the imaging speed and sensitivity. However, dedicated wideband and coherence optical pulse source with high shot-to-shot stability has been mandated for time-wavelength mapping—the enabling process for ultrahigh speed wavelength-encoded image retrieval. From the practical point of view, exploiting methods to relax the stringent requirements (e.g., temporal stability and coherence) for the source of time-stretch microscopy is thus of great value. In this paper, we demonstrated time-stretch microscopy by reconstructing the time-wavelength mapping sequence from a wideband incoherent source. Utilizing the time-lens focusing mechanism mediated bymore » a narrow-band pulse source, this approach allows generation of a wideband incoherent source, with the spectral efficiency enhanced by a factor of 18. As a proof-of-principle demonstration, time-stretch imaging with the scan rate as high as MHz and diffraction-limited resolution is achieved based on the wideband incoherent source. We note that the concept of time-wavelength sequence reconstruction from wideband incoherent source can also be generalized to any high-speed optical real-time measurements, where wavelength is acted as the information carrier.« less

Temperature effects on wavelength calibration of the optical spectrum analyzer

NASA Astrophysics Data System (ADS)

Mongkonsatit, Kittiphong; Ranusawud, Monludee; Srikham, Sitthichai; Bhatranand, Apichai; Jiraraksopakun, Yuttapong

2018-03-01

This paper presents the investigation of the temperature effects on wavelength calibration of an optical spectrum analyzer or OSA. The characteristics of wavelength dependence on temperatures are described and demonstrated under the guidance of the IEC 62129-1:2006, the international standard for the Calibration of wavelength/optical frequency measurement instruments - Part 1: Optical spectrum analyzer. Three distributed-feedback lasers emit lights with wavelengths of 1310 nm, 1550 nm, and 1600 nm were used as light sources in this work. Each light was split by a 1 x 2 fiber splitter whereas one end was connected to a standard wavelength meter and the other to an under-test OSA. Two Experiment setups were arranged for the analysis of the wavelength reading deviations between a standard wavelength meter and an OSA under a variety of circumstances of different temperatures and humidity conditions. The experimental results showed that, for wavelengths of 1550 nm and 1600 nm, the wavelength deviations were proportional to the value of temperature with the minimum and maximum of -0.015 and 0.030 nm, respectively. While the deviations of 1310 nm wavelength did not change much with the temperature as they were in the range of -0.003 nm to 0.010 nm. The measurement uncertainty was also evaluated according to the IEC 62129-1:2006. The main contribution of measurement uncertainty was caused by the wavelength deviation. The uncertainty of measurement in this study is 0.023 nm with coverage factor, k = 2.

Wavelength-scale light concentrator made by direct 3D laser writing of polymer metamaterials.

PubMed

Moughames, J; Jradi, S; Chan, T M; Akil, S; Battie, Y; Naciri, A En; Herro, Z; Guenneau, S; Enoch, S; Joly, L; Cousin, J; Bruyant, A

2016-10-04

We report on the realization of functional infrared light concentrators based on a thick layer of air-polymer metamaterial with controlled pore size gradients. The design features an optimum gradient index profile leading to light focusing in the Fresnel zone of the structures for two selected operating wavelength domains near 5.6 and 10.4 μm. The metamaterial which consists in a thick polymer containing air holes with diameters ranging from λ/20 to λ/8 is made using a 3D lithography technique based on the two-photon polymerization of a homemade photopolymer. Infrared imaging of the structures reveals a tight focusing for both structures with a maximum local intensity increase by a factor of 2.5 for a concentrator volume of 1.5 λ 3 , slightly limited by the residual absorption of the selected polymer. Such porous and flat metamaterial structures offer interesting perspectives to increase infrared detector performance at the pixel level for imaging or sensing applications.

Wavelength-scale light concentrator made by direct 3D laser writing of polymer metamaterials

PubMed Central

Moughames, J.; Jradi, S.; Chan, T. M.; Akil, S.; Battie, Y.; Naciri, A. En; Herro, Z.; Guenneau, S.; Enoch, S.; Joly, L.; Cousin, J.; Bruyant, A.

2016-01-01

We report on the realization of functional infrared light concentrators based on a thick layer of air-polymer metamaterial with controlled pore size gradients. The design features an optimum gradient index profile leading to light focusing in the Fresnel zone of the structures for two selected operating wavelength domains near 5.6 and 10.4 μm. The metamaterial which consists in a thick polymer containing air holes with diameters ranging from λ/20 to λ/8 is made using a 3D lithography technique based on the two-photon polymerization of a homemade photopolymer. Infrared imaging of the structures reveals a tight focusing for both structures with a maximum local intensity increase by a factor of 2.5 for a concentrator volume of 1.5 λ3, slightly limited by the residual absorption of the selected polymer. Such porous and flat metamaterial structures offer interesting perspectives to increase infrared detector performance at the pixel level for imaging or sensing applications. PMID:27698476

Nonclassical light in interferometric measurements

NASA Technical Reports Server (NTRS)

Ansari, N. A.; Difiore, L.; Romano, R.; Solimeno, S.; Zaccaria, F.; Manko, Margarita A.; Manko, Vladimir I.

1995-01-01

It is shown that the even and odd coherent light and other nonclassical states of light like superposition of coherent states with different phases may replace the squeezed light in an interferometric gravitational wave detector to increase its sensitivity.

Wavelength calibration of an imaging spectrometer based on Savart interferometer

NASA Astrophysics Data System (ADS)

Li, Qiwei; Zhang, Chunmin; Yan, Tingyu; Quan, Naicheng; Wei, Yutong; Tong, Cuncun

2017-09-01

The basic principle of Fourier-transform imaging spectrometer (FTIS) based on Savart interferometer is outlined. The un-identical distribution of the optical path difference which leads to the wavelength drift of each row of the interferogram is analyzed. Two typical methods for wavelength calibration of the presented system are described. The first method unifies different spectral intervals and maximum spectral frequencies of each row by a reference monochromatic light with known wavelength, and the dispersion compensation of Savart interferometer is also involved. The second approach is based on the least square fitting which builds the functional relation between recovered wavelength, row number and calibrated wavelength by concise equations. The effectiveness of the two methods is experimentally demonstrated with monochromatic lights and mixed light source across the detecting band of the system, and the results indicate that the first method has higher precision and the mean root-mean-square error of the recovered wavelengths is significantly reduced from 19.896 nm to 1.353 nm, while the second method is more convenient to implement and also has good precision of 2.709 nm.

Compensation of spectral artifacts in dual-modality intravascular optical coherence tomography and near-infrared spectroscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fard, Ali M.; Gardecki, Joseph A.; Ughi, Giovanni J.; Hyun, Chulho; Tearney, Guillermo J.

2016-02-01

Intravascular optical coherence tomography (OCT) is a high-resolution catheter-based imaging method that provides three-dimensional microscopic images of coronary artery in vivo, facilitating coronary artery disease treatment decisions based on detailed morphology. Near-infrared spectroscopy (NIRS) has proven to be a powerful tool for identification of lipid-rich plaques inside the coronary walls. We have recently demonstrated a dual-modality intravascular imaging technology that integrates OCT and NIRS into one imaging catheter using a two-fiber arrangement and a custom-made dual-channel fiber rotary junction. It therefore enables simultaneous acquisition of microstructural and composition information at 100 frames/second for improved diagnosis of coronary lesions. The dual-modality OCT-NIRS system employs a single wavelength-swept light source for both OCT and NIRS modalities. It subsequently uses a high-speed photoreceiver to detect the NIRS spectrum in the time domain. Although use of one light source greatly simplifies the system configuration, such light source exhibits pulse-to-pulse wavelength and intensity variation due to mechanical scanning of the wavelength. This can be in particular problematic for NIRS modality and sacrifices the reliability of the acquired spectra. In order to address this challenge, here we developed a robust data acquisition and processing method that compensates for the spectral variations of the wavelength-swept light source. The proposed method extracts the properties of the light source, i.e., variation period and amplitude from a reference spectrum and subsequently calibrates the NIRS datasets. We have applied this method on datasets obtained from cadaver human coronary arteries using a polygon-scanning (1230-1350nm) OCT system, operating at 100,000 sweeps per second. The results suggest that our algorithm accurately and robustly compensates the spectral variations and visualizes the dual-modality OCT-NIRS images. These

Multi-Wavelength Photomagnetic Imaging for Oral Cancer

NASA Astrophysics Data System (ADS)

Marks, Michael

In this study, a multi-wavelength Photomagnetic Imaging (PMI) system is developed and evaluated with experimental studies.. PMI measures temperature increases in samples illuminated by near-infrared light sources using magnetic resonance thermometry. A multiphysics solver combining light and heat transfer models the spatiotemporal distribution of the temperature change. The PMI system develop in this work uses three lasers of varying wavelength (785 nm, 808 nm, 860 nm) to heat the sample. By using multiple wavelengths, we enable the PMI system to quantify the relative concentrations of optical contrast in turbid media and monitor their distribution, at a higher resolution than conventional diffuse optical imaging. The data collected from agarose phantoms with multiple embedded contrast agents designed to simulate the optical properties of oxy- and deoxy-hemoglobin is presented. The reconstructed images demonstrate that multi-wavelength PMI can resolve this complex inclusion structure with high resolution and recover the concentration of each contrast agent with high quantitative accuracy. The modified multi-wavelength PMI system operates under the maximum skin exposure limits defined by the American National Standards Institute, to enable future clinical applications.

Marginal eyespots on butterfly wings deflect bird attacks under low light intensities with UV wavelengths.

PubMed

Olofsson, Martin; Vallin, Adrian; Jakobsson, Sven; Wiklund, Christer

2010-05-24

Predators preferentially attack vital body parts to avoid prey escape. Consequently, prey adaptations that make predators attack less crucial body parts are expected to evolve. Marginal eyespots on butterfly wings have long been thought to have this deflective, but hitherto undemonstrated function. Here we report that a butterfly, Lopinga achine, with broad-spectrum reflective white scales in its marginal eyespot pupils deceives a generalist avian predator, the blue tit, to attack the marginal eyespots, but only under particular conditions-in our experiments, low light intensities with a prominent UV component. Under high light intensity conditions with a similar UV component, and at low light intensities without UV, blue tits directed attacks towards the butterfly head. In nature, birds typically forage intensively at early dawn, when the light environment shifts to shorter wavelengths, and the contrast between the eyespot pupils and the background increases. Among butterflies, deflecting attacks is likely to be particularly important at dawn when low ambient temperatures make escape by flight impossible, and when insectivorous birds typically initiate another day's search for food. Our finding that the deflective function of eyespots is highly dependent on the ambient light environment helps explain why previous attempts have provided little support for the deflective role of marginal eyespots, and we hypothesize that the mechanism that we have discovered in our experiments in a laboratory setting may function also in nature when birds forage on resting butterflies under low light intensities.

Spatial coherence effect on layer thickness determination in narrowband full-field optical coherence tomography.

PubMed

Safrani, Avner; Abdulhalim, Ibrahim

2011-06-20

Longitudinal spatial coherence (LSC) is determined by the spatial frequency content of an optical beam. The use of lenses with a high numerical aperture (NA) in full-field optical coherence tomography and a narrowband light source makes the LSC length much shorter than the temporal coherence length, hence suggesting that high-resolution 3D images of biological and multilayered samples can be obtained based on the low LSC. A simplified model is derived, supported by experimental results, which describes the expected interference output signal of multilayered samples when high-NA lenses are used together with a narrowband light source. An expression for the correction factor for the layer thickness determination is found valid for high-NA objectives. Additionally, the method was applied to a strongly scattering layer, demonstrating the potential of this method for high-resolution imaging of scattering media.

Intraocular application of gold nanodisks optically tuned for optical coherence tomography: inhibitory effect on retinal neovascularization without unbearable toxicity.

PubMed

Song, Hyun Beom; Wi, Jung-Sub; Jo, Dong Hyun; Kim, Jin Hyoung; Lee, Sang-Won; Lee, Tae Geol; Kim, Jeong Hun

2017-08-01

Bare gold nanospheres have been shown to have anti-angiogenic effects but are optically unfavorable because their resonant wavelength lies in the visible spectrum. Here, we design gold nanodisks with a higher scattering capability than gold nanorods and with a resonant wavelength at near-infrared region - the area where the source of light utilized by optical coherence tomography (OCT) lies. With a physical synthesis system, we then fabricate 160-nm-sized gold nanodisks exhibiting resonant wavelength at 830 nm. The synthesized nanoparticles were successfully visualized in in vivo OCT at concentrations as low as 1 pM. After demonstrating their binding ability to vascular endothelial growth factor (VEGF), we show that they suppress VEGF-induced migration of endothelial cells. Finally, we demonstrate that intravitreally injected gold nanodisks attenuate neovascularization of oxygen-induced retinopathy in mice, in a dose dependent manner, such that they are cleared from the vitreous within 2 weeks without histologic or electrophysiologic toxicity. Copyright © 2017 Elsevier Inc. All rights reserved.

Optical diffraction tomography with fully and partially coherent illumination in high numerical aperture label-free microscopy [Invited].

PubMed

Soto, Juan M; Rodrigo, José A; Alieva, Tatiana

2018-01-01

Quantitative label-free imaging is an important tool for the study of living microorganisms that, during the last decade, has attracted wide attention from the optical community. Optical diffraction tomography (ODT) is probably the most relevant technique for quantitative label-free 3D imaging applied in wide-field microscopy in the visible range. The ODT is usually performed using spatially coherent light illumination and specially designed holographic microscopes. Nevertheless, the ODT is also compatible with partially coherent illumination and can be realized in conventional wide-field microscopes by applying refocusing techniques, as it has been recently demonstrated. Here, we compare these two ODT modalities, underlining their pros and cons and discussing the optical setups for their implementation. In particular, we pay special attention to a system that is compatible with a conventional wide-field microscope that can be used for both ODT modalities. It consists of two easily attachable modules: the first for sample illumination engineering based on digital light processing technology; the other for focus scanning by using an electrically driven tunable lens. This hardware allows for a programmable selection of the wavelength and the illumination design, and provides fast data acquisition as well. Its performance is experimentally demonstrated in the case of ODT with partially coherent illumination providing speckle-free 3D quantitative imaging.

Simultaneous multimodal ophthalmic imaging using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

PubMed Central

Malone, Joseph D.; El-Haddad, Mohamed T.; Bozic, Ivan; Tye, Logan A.; Majeau, Lucas; Godbout, Nicolas; Rollins, Andrew M.; Boudoux, Caroline; Joos, Karen M.; Patel, Shriji N.; Tao, Yuankai K.

2016-01-01

Scanning laser ophthalmoscopy (SLO) benefits diagnostic imaging and therapeutic guidance by allowing for high-speed en face imaging of retinal structures. When combined with optical coherence tomography (OCT), SLO enables real-time aiming and retinal tracking and provides complementary information for post-acquisition volumetric co-registration, bulk motion compensation, and averaging. However, multimodality SLO-OCT systems generally require dedicated light sources, scanners, relay optics, detectors, and additional digitization and synchronization electronics, which increase system complexity. Here, we present a multimodal ophthalmic imaging system using swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography (SS-SESLO-OCT) for in vivo human retinal imaging. SESLO reduces the complexity of en face imaging systems by multiplexing spatial positions as a function of wavelength. SESLO image quality benefited from single-mode illumination and multimode collection through a prototype double-clad fiber coupler, which optimized scattered light throughput and reduce speckle contrast while maintaining lateral resolution. Using a shared 1060 nm swept-source, shared scanner and imaging optics, and a shared dual-channel high-speed digitizer, we acquired inherently co-registered en face retinal images and OCT cross-sections simultaneously at 200 frames-per-second. PMID:28101411

Effects of Wavelength and Defect Density on the Efficiency of (In,Ga)N-Based Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Pristovsek, Markus; Bao, An; Oliver, Rachel A.; Badcock, Tom; Ali, Muhammad; Shields, Andrew

2017-06-01

We measure the electroluminescence of light-emitting diodes (LEDs) on substrates with low dislocation densities (LDD) at 106 cm-2 and low 108 cm-2 , and compare them to LEDs on substrates with high dislocation densities (HDD) closer to 1010 cm-2 . The external quantum efficiencies (EQEs) are fitted using the A B C model with and without localization. The nonradiative-recombination (NR) coefficient A is constant for HDD LEDs, indicating that the NR is dominated by dislocations at all wavelengths. However, A strongly increases for LDD LEDs by a factor of 20 when increasing the emission wavelength from 440 to 540 nm. We attribute this to an increased density of point defects due to the lower growth temperatures used for longer wavelengths. The radiative recombination coefficient B follows the squared wave-function overlap for all samples. Using the observed coefficients, we calculate the peak efficiency as a function of the wavelength. For HDD LEDs the change of wave-function overlap (i.e., B ) is sufficient to reduce the EQE as observed, while for LDD LEDs also the NR coefficient A must increase to explain the observed EQEs. Thus, reducing NR is important to improving the EQEs of green LEDs, but this cannot be achieved solely by reducing the dislocation density: point defects must also be addressed.

Non-thermal damage to lead tungstate induced by intense short-wavelength laser radiation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Vozda, Vojtech; Boháček, Pavel; Burian, Tomáš; Chalupský, Jaromir; Hájková, Vera; Juha, Libor; Vyšín, Ludek; Gaudin, Jérôme; Heimann, Philip A.; Hau-Riege, Stefan P.; Jurek, Marek; Klinger, Dorota; Krzywinski, Jacek; Messerschmidt, Marc; Moeller, Stefan P.; Nagler, Robert; Pelka, Jerzy B.; Rowen, Michael; Schlotter, William F.; Swiggers, Michele L.; Sinn, Harald; Sobierajski, Ryszard; Tiedtke, Kai; Toleikis, Sven; Tschentscher, Thomas; Turner, Joshua J.; Wabnitz, Hubertus; Nelson, Art J.; Kozlova, Maria V.; Vinko, Sam M.; Whitcher, Thomas; Dzelzainis, Thomas; Renner, Oldrich; Saksl, Karel; Fäustlin, Roland R.; Khorsand, Ali R.; Fajardo, Marta; Iwan, Bianca S.; Andreasson, Jakob; Hajdu, Janos; Timneanu, Nicusor; Wark, Justin S.; Riley, David; Lee, Richard W.; Nagasono, Mitsuru; Yabashi, Makina

2017-05-01

Interaction of short-wavelength free-electron laser (FEL) beams with matter is undoubtedly a subject to extensive investigation in last decade. During the interaction various exotic states of matter, such as warm dense matter, may exist for a split second. Prior to irreversible damage or ablative removal of the target material, complicated electronic processes at the atomic level occur. As energetic photons impact the target, electrons from inner atomic shells are almost instantly photo-ionized, which may, in some special cases, cause bond weakening, even breaking of the covalent bonds, subsequently result to so-called non-thermal melting. The subject of our research is ablative damage to lead tungstate (PbWO4) induced by focused short-wavelength FEL pulses at different photon energies. Post-mortem analysis of complex damage patterns using the Raman spectroscopy, atomic-force (AFM) and Nomarski (DIC) microscopy confirms an existence of non-thermal melting induced by high-energy photons in the ionic monocrystalline target. Results obtained at Linac Coherent Light Source (LCLS), Free-electron in Hamburg (FLASH), and SPring-8 Compact SASE Source (SCSS) are presented in this Paper.

Wavelength-division and spatial multiplexing using tandem interferometers for Bragg grating sensor networks

NASA Astrophysics Data System (ADS)

Kalli, K.; Brady, G. P.; Webb, D. J.; Jackson, D. A.; Zhang, L.; Bennion, I.

1995-12-01

We present a new method for the interrogation of large arrays of Bragg grating sensors. Eight gratings operating between the wavelengths of 1533 and 1555 nm have been demultiplexed. An unbalanced Mach-Zehnder interferometer illuminated by a single low-coherence source provides a high-phase-resolution output for each sensor, the outputs of which are sequentially selected in wavelength by a tunable Fabry-Perot interferometer. The minimum detectable strain measured was 90 n 3 / \\radical Hz \\end-radical at 7 Hz for a wavelength of 1535 nm.

Ultra-high Resolution Coherent X-ray Imaging of Nano-Materials

NASA Astrophysics Data System (ADS)

Shapiro, David

A revolution is underway in the field of x-ray microscopy driven by the develop of experimental, theoretical and computational means of producing a complete description of coherent imaging systems from x-ray diffraction data. The methods being developed not only allow for full quantification and removal of all optical aberrations but also extension of the numerical aperture to the diffraction limit. One such method under intensive development is x-ray ptychography. This is a scanned probe method that reconstructs a scattering object and its illumination from coherent diffraction data. Within the first few years of development at the Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, this method has already achieved the highest resolution x-ray images ever recorded in two, three and four dimensions. With the ability of x-rays to penetrate significantly more matter than electrons, their short wavelength and their sensitivity to chemical and magnetic states of matter, x-ray ptychography is set to revolutionize how we see the nano-scale world. In this presentation I will briefly describe the technical framework for how various methods work and will give a detailed account of a practical implementation at the ALS along with various scientific applications. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Silver nanoparticles (AgNPs) as a contrast agent for imaging of animal tissue using swept-source optical coherence tomography (SSOCT)

NASA Astrophysics Data System (ADS)

Mondal, Indranil; Raj, Shipra; Roy, Poulomi; Poddar, Raju

2018-01-01

We present noninvasive three-dimensional depth-resolved imaging of animal tissue with a swept-source optical coherence tomography system at 1064 nm center wavelength and silver nanoparticles (AgNPs) as a potential contrast agent. A swept-source laser light source is used to enable an imaging rate of 100 kHz (100 000 A-scans s-1). Swept-source optical coherence tomography is a new variant of the optical coherence tomography (OCT) technique, offering unique advantages in terms of sensitivity, reduction of motion artifacts, etc. To enhance the contrast of an OCT image, AgNPs are utilized as an exogeneous contrast agent. AgNPs are synthesized using a modified Tollens method and characterization is done by UV-vis spectroscopy, dynamic light scattering, scanning electron microscopy and energy dispersive x-ray spectroscopy. In vitro imaging of chicken breast tissue, with and without the application of AgNPs, is performed. The effect of AgNPs is studied with different exposure times. A mathematical model is also built to calculate changes in the local scattering coefficient of tissue from OCT images. A quantitative estimation of scattering coefficient and contrast is performed for tissues with and without application of AgNPs. Significant improvement in contrast and increase in scattering coefficient with time is observed.

Mechanisms and Methods for Selective Wavelength Filtering

NASA Technical Reports Server (NTRS)

Tuma, Margaret (Inventor); Brown, Thomas G. (Inventor); Gruhlke, Russell (Inventor)

2007-01-01

An optical filter includes a dielectric waveguide layer, supporting waveguide modes at specific wavelengths and receiving incident light, a corrugated film layer, composed of one of a metal and a semiconductor and positioned adjacent to a second surface of the waveguide layer and a sensor layer, wherein the sensor layer is capable of absorbing optical energy and generating a corresponding electrical signal. The metal film layer supports a plurality of plasmons, the plurality of plasmons producing a first field and is excited by a transverse mode of the waveguide modes at a wavelength interval. The first field penetrates the sensor layer and the sensor layer generates an electrical signal corresponding to an intensity of received incident light within the wavelength interval.

Slot-grating flat lens for telecom wavelengths.

PubMed

Pugh, Jonathan R; Stokes, Jamie L; Lopez-Garcia, Martin; Gan, Choon-How; Nash, Geoff R; Rarity, John G; Cryan, Martin J

2014-07-01

We present a stand-alone beam-focusing flat lens for use in the telecommunications wavelength range. Light incident on the back surface of the lens propagates through a subwavelength aperture and is heavily diffracted on exit and partially couples into a surface plasmon polariton and a surface wave propagating along the surface of the lens. Interference between the diffracted wave and re-emission from a grating patterned on the surface produces a highly collimated beam. We show for the first time a geometry at which a lens of this type can be used at telecommunication wavelengths (λ=1.55 μm) and identify the light coupling and re-emission mechanisms involved. Measured beam profile results at varying incident wavelengths show excellent agreement with Lumerical FDTD simulation results.

Note: Three wavelengths near-infrared spectroscopy system for compensating the light absorbance by water

NASA Astrophysics Data System (ADS)

Bhutta, M. Raheel; Hong, Keum-Shik; Kim, Beop-Min; Hong, Melissa Jiyoun; Kim, Yun-Hee; Lee, Se-Ho

2014-02-01

Given that approximately 80% of blood is water, we develop a wireless functional near-infrared spectroscopy system that detects not only the concentration changes of oxy- and deoxy-hemoglobin (HbO and HbR) during mental activity but also that of water (H2O). Additionally, it implements a water-absorption correction algorithm that improves the HbO and HbR signal strengths during an arithmetic task. The system comprises a microcontroller, an optical probe, tri-wavelength light emitting diodes, photodiodes, a WiFi communication module, and a battery. System functionality was tested by means of arithmetic-task experiments performed by healthy male subjects.

Note: three wavelengths near-infrared spectroscopy system for compensating the light absorbance by water.

PubMed

Bhutta, M Raheel; Hong, Keum-Shik; Kim, Beop-Min; Hong, Melissa Jiyoun; Kim, Yun-Hee; Lee, Se-Ho

2014-02-01

Given that approximately 80% of blood is water, we develop a wireless functional near-infrared spectroscopy system that detects not only the concentration changes of oxy- and deoxy-hemoglobin (HbO and HbR) during mental activity but also that of water (H2O). Additionally, it implements a water-absorption correction algorithm that improves the HbO and HbR signal strengths during an arithmetic task. The system comprises a microcontroller, an optical probe, tri-wavelength light emitting diodes, photodiodes, a WiFi communication module, and a battery. System functionality was tested by means of arithmetic-task experiments performed by healthy male subjects.

Coherence transfer of subhertz-linewidth laser light via an optical fiber noise compensated by remote users.

PubMed

Wu, Lifei; Jiang, Yanyi; Ma, Chaoqun; Yu, Hongfu; Bi, Zhiyi; Ma, Longsheng

2016-09-15

We present a technique for the coherence transfer of laser light through a fiber link, where the optical phase noise induced by environmental perturbation via the fiber link is compensated by remote users. When compensating the fiber noise by remote users, the time base at the remote site independent from that at the local site does not destroy the performance of the fiber output light. Using this technique, we demonstrate the transfer of subhertz-linewidth laser light through a 25-km-long, lab-based spooled fiber. After being compensated, the relative linewidth between the fiber input and output light is 1 mHz, and the relative frequency instability is 4×10^-17 at 1 s averaging time and scales down to 2×10^-19 at 800 s averaging time. The frequency uncertainty of the light after transferring through the fiber relative to that of the input light is 3.0×10^-19. This system is suitable for the simultaneous transfer of an optical signal to a number of end users within a city.

High-Energy Density science at the Linac Coherent Light Source

DOE PAGES

Glenzer, S. H.; Fletcher, L. B.; Hastings, J. B.

2016-04-01

The Matter in Extreme Conditions end station at the Linac Coherent Light Source holds great promise for novel pump-probe experiments to make new discoveries in high- energy density science. Recently, our experiments have demonstrated the first spectrally- resolved measurements of plasmons using a seeded 8-keV x-ray laser beam. Forward x-ray Thomson scattering spectra from isochorically heated solid aluminum show a well-resolved plasmon feature that is down-shifted in energy by 19 eV from the incident 8 keV elastic scattering feature. In this spectral range, the simultaneously measured backscatter spectrum shows no spectral features indicating observation of collective plasmon oscillations on amore » scattering length comparable to the screening length. Moreover, this technique is a prerequisite for Thomson scattering measurements in compressed matter where the plasmon shift is a sensitive function of the free electron density and where the plasmon intensity provides information on temperature.« less

Comparison of qubit and qutrit like entangled squeezed and coherent states of light

NASA Astrophysics Data System (ADS)

Najarbashi, G.; Mirzaei, S.

2016-10-01

Squeezed state of light is one of the important subjects in quantum optics which is generated by optical nonlinear interactions. In this paper, we especially focus on qubit like entangled squeezed states (ESS's) generated by beam splitters, phase-shifter and cross Kerr nonlinearity. Moreover the Wigner function of two-mode qubit and qutrit like ESS are investigated. We will show that the distances of peaks of Wigner functions for two-mode ESS are entanglement sensitive and can be a witness for entanglement. Like the qubit cases, monogamy inequality is fulfilled for qutrit like ESS. These trends are compared with those obtained for qubit and qutrit like entangled coherent states (ECS).

Tunnel junction multiple wavelength light-emitting diodes

DOEpatents

Olson, Jerry M.; Kurtz, Sarah R.

1992-01-01

A multiple wavelength LED having a monolithic cascade cell structure comprising at least two p-n junctions, wherein each of said at least two p-n junctions have substantially different band gaps, and electrical connector means by which said at least two p-n junctions may be collectively energized; and wherein said diode comprises a tunnel junction or interconnect.

Noise reduction in digital lensless holographic microscopy by engineering the light from a light-emitting diode.

PubMed

Garcia-Sucerquia, Jorge

2013-01-01

By engineering the light from a light-emitting diode (LED) the noises present in digital lensless holographic microscopy (DLHM) are reduced. The partially coherent light from an LED is tailored to produce a spherical wavefront with limited coherence time and the spatial coherence needed by DLHM to work. DLHM with this engineered light source is used to image biological samples that cover areas of the order of mm(2). The ratio between the diameter of the area that is almost coherently illuminated to the diameter of the illumination area is utilized as parameter to quantify the performance of the DLHM with the engineered LED light source. Experimental results show that while the noises can be reduced effectively the spatial resolution can be kept in the micrometer range.

Measurement of morphing wing deflection by a cross-coherence fiber optic interferometric technique

NASA Astrophysics Data System (ADS)

Tomić, Miloš C.; Djinović, Zoran V.; Scheerer, Michael; Petricevic, Slobodan J.

2018-01-01

A fiber-optic interferometric technique aimed at measuring the deflection of aircrafts’ morphing wings is presented. The wing deflection induces a strain in the sensing fiber optic coils that are firmly fixed onto the wing. A change of the phase angle of the light propagating through the fiber is measured by an ‘all-in-fiber’ Michelson interferometer based on a 3 × 3 fiber-optic coupler. Two light sources of different coherence lengths and wavelengths are simultaneously used to ensure a wide measurement range and high accuracy. A new technique for determination of the zero deflection point using the cross-correlation of the two interferograms is proposed. The experiments performed on a specimen made of a carbon-fiber-reinforced plastic honeycomb structure demonstrated a relative uncertainty <1% and a precision of about 0.06° in the measuring range ±5° of the morphing wing deflection.

Coherence time of over a second in a telecom-compatible quantum memory storage material

NASA Astrophysics Data System (ADS)

Rančić, Miloš; Hedges, Morgan P.; Ahlefeldt, Rose L.; Sellars, Matthew J.

2018-01-01

Quantum memories for light will be essential elements in future long-range quantum communication networks. These memories operate by reversibly mapping the quantum state of light onto the quantum transitions of a material system. For networks, the quantum coherence times of these transitions must be long compared to the network transmission times, approximately 100 ms for a global communication network. Due to a lack of a suitable storage material, a quantum memory that operates in the 1,550 nm optical fibre communication band with a storage time greater than 1 μs has not been demonstrated. Here we describe the spin dynamics of 167Er3+: Y2SiO5 in a high magnetic field and demonstrate that this material has the characteristics for a practical quantum memory in the 1,550 nm communication band. We observe a hyperfine coherence time of 1.3 s. We also demonstrate efficient spin pumping of the entire ensemble into a single hyperfine state, a requirement for broadband spin-wave storage. With an absorption of 70 dB cm-1 at 1,538 nm and Λ transitions enabling spin-wave storage, this material is the first candidate identified for an efficient, broadband quantum memory at telecommunication wavelengths.

Effect of pinpoint plantar long-wavelength infrared light irradiation on subcutaneous temperature and stress markers

PubMed Central

Ryotokuji, Kenji; Ishimaru, Keisou; Kihara, Kazuhiko; Namiki, Yoshihisa; Hozumi, Nobumichi

2013-01-01

Background and aims: The current investigation was aimed at the development of a novel non-invasive treatment system, “pinpoint plantar long-wavelength infrared light irradiation (PP-LILI)”, which may be able to relieve mental stress and reduce stress-related hormones. Materials (Subjects) and methods: We compared the subcutaneous temperature, blood pressure, the degree of secretion of stress hormones before and after pinpoint irradiations (wavelength: 8–11 μm; output: 30mW). The study enrolled 15 subjects (Japanese healthy adults; 8 males, 7 females; average age 47.8 ± 14.6 years). Two parts of the planter region were irradiated for 15 min respectively. The stress markers such as ACTH, salivary amylase and cortisol were measured. As well, core body temperature and blood pressure were analyzed before and after the irradiation. Results: A series of experiments revealed increased body temperature, decreased levels of blood pressure and stress markers described above after the irradiation. Conclusions: These results clearly suggest that the PP-LILI system will be quite useful for relieving stress and improvement of homeostatic functions in the body. PMID:24155554

Optical filter including a sub-wavelength periodic structure and method of making

DOEpatents

Kaushik, Sumanth; Stallard, Brian R.

1998-01-01

An optical filter includes a dielectric layer formed within a resonant optical cavity, with the dielectric layer having formed therein a sub-wavelength periodic structure to define, at least in part, a wavelength for transmission of light through the resonant optical cavity. The sub-wavelength periodic structure can be formed either by removing material from the dielectric layer (e.g. by etching through an electron-beam defined mask), or by altering the composition of the layer (e.g. by ion implantation). Different portions of the dielectric layer can be patterned to form one or more optical interference filter elements having different light transmission wavelengths so that the optical filter can filter incident light according to wavelength and/or polarization. For some embodiments, the optical filter can include a detector element in optical alignment with each optical interference filter element to quantify or measure the filtered light for analysis thereof. The optical filter has applications to spectrometry, colorimetry, and chemical sensing.

Optical filter including a sub-wavelength periodic structure and method of making