COHERENT DETECTION FOR SPECTRAL AMPLITUDE-CODED OPTICAL LABEL SWITCHING SYSTEMS

DEFF Research Database (Denmark)

Osadchiy, Alexey Vladimirovich; Tafur Monroy, Idelfonso

2010-01-01

Coherent detection for spectrally encoded optical labels is proposed and experimentally demonstrated for three label tones spectrally spaced at 1 GHz. The proposed method utilizes a frequency swept local oscillator in a coherent receiver supported by digital signal processing for improved...... flexibility and upgradeability while reducing label detection subsystem complexity as compared with the conventional optical autocorrelation based approaches....

A Fiber-Optic System Generating Pulses of High Spectral Density

Science.gov (United States)

Abramov, A. S.; Zolotovskii, I. O.; Korobko, D. A.; Fotiadi, A. A.

2018-03-01

A cascade fiber-optic system that generates pulses of high spectral density by using the effect of nonlinear spectral compression is proposed. It is demonstrated that the shape of the pulse envelope substantially influences the degree of compression of its spectrum. In so doing, maximum compression is achieved for parabolic pulses. The cascade system includes an optical fiber exhibiting normal dispersion that decreases along the fiber length, thereby ensuring that the pulse envelope evolves toward a parabolic shape, along with diffraction gratings and a fiber spectral compressor. Based on computer simulation, we determined parameters of cascade elements leading to maximum spectral density of radiation originating from a subpicosecond laser pulse of medium energy.

Spectral domain optical coherence tomography findings in tamoxifen retinopathy--a case report.

Science.gov (United States)

Nair, Sandhya Narayanan; Anantharaman, Giridhar; Gopalakrishnan, Mahesh; Vyas, Jyothiprakash

2013-01-01

To report spectral domain optical coherence tomography findings in a case of typical tamoxifen retinopathy. In this observational case report, a patient with tamoxifen retinopathy was imaged with spectral domain optical coherence tomography and fundus auto fluorescence. Spectral domain optical coherence tomography showed numerous hyperreflective spots within the retina, mainly in the inner retinal layers in both the eyes. The external limiting membrane, the Inner Segment-Outer Segment junction, and the photoreceptors were not discernable at the fovea in the right eye. In the left eye, there was foveal atrophy with total loss of photoreceptors. The autofluorescent images showed macular hypofluorescence with foveal hyperfluorescence. Spectral domain optical coherence tomography demonstrated abnormalities in the outer retinal layers in tamoxifen retinopathy. There were also characteristic alterations in the autofluorescence pattern at the macula in tamoxifen retinopathy.

Interferometric and nonlinear-optical spectral-imaging techniques for outer space and live cells

Science.gov (United States)

Itoh, Kazuyoshi

2015-12-01

Multidimensional signals such as the spectral images allow us to have deeper insights into the natures of objects. In this paper the spectral imaging techniques that are based on optical interferometry and nonlinear optics are presented. The interferometric imaging technique is based on the unified theory of Van Cittert-Zernike and Wiener-Khintchine theorems and allows us to retrieve a spectral image of an object in the far zone from the 3D spatial coherence function. The retrieval principle is explained using a very simple object. The promising applications to space interferometers for astronomy that are currently in progress will also be briefly touched on. An interesting extension of interferometric spectral imaging is a 3D and spectral imaging technique that records 4D information of objects where the 3D and spectral information is retrieved from the cross-spectral density function of optical field. The 3D imaging is realized via the numerical inverse propagation of the cross-spectral density. A few techniques suggested recently are introduced. The nonlinear optical technique that utilizes stimulated Raman scattering (SRS) for spectral imaging of biomedical targets is presented lastly. The strong signals of SRS permit us to get vibrational information of molecules in the live cell or tissue in real time. The vibrational information of unstained or unlabeled molecules is crucial especially for medical applications. The 3D information due to the optical nonlinearity is also the attractive feature of SRS spectral microscopy.

Bidirectional soliton spectral tunneling effects in the regime of optical event horizon

DEFF Research Database (Denmark)

Gu, Jie; Guo, Hairun; Wang, Shaofei

2015-01-01

We study the cross-phase-modulation-induced soliton spectral shifting in the regime of the optical event horizon. The perturbed soliton to either red-shifting or blue-shifting is controllable, which could evoke bidirectional soliton spectral tunneling effects.......We study the cross-phase-modulation-induced soliton spectral shifting in the regime of the optical event horizon. The perturbed soliton to either red-shifting or blue-shifting is controllable, which could evoke bidirectional soliton spectral tunneling effects....

Submicron Resolution Spectral-Domain Optical Coherence Tomography

KAUST Repository

Alarousu, Erkki; Jabbour, Ghassan

2013-01-01

Apparatuses and systems for submicron resolution spectral-domain optical coherence tomography (OCT) are disclosed. The system may use white light sources having wavelengths within 400-1000 nanometers, and achieve resolution below 1 .mu

Precision spectral manipulation: A demonstration using a coherent optical memory

Energy Technology Data Exchange (ETDEWEB)

Sparkes, B. M.; Cairns, C.; Hosseini, M.; Higginbottom, D.; Campbell, G. T.; Lam, P. K.; Buchler, B. C. [Centre for Quantum Computation and Communication Technology, The Australian National University, Canberra (Australia)

2014-12-04

The ability to coherently spectrally manipulate quantum information has the potential to improve qubit rates across quantum channels and find applications in optical quantum computing. Here we present experiments that use a multi-element solenoid combined with the three-level gradient echo memory scheme to perform precision spectral manipulation of optical pulses. If applied in a quantum information network, these operations would enable frequency-based multiplexing of qubits.

Heterodyne detection using spectral line pairing for spectral phase encoding optical code division multiple access and dynamic dispersion compensation.

Science.gov (United States)

Yang, Yi; Foster, Mark; Khurgin, Jacob B; Cooper, A Brinton

2012-07-30

A novel coherent optical code-division multiple access (OCDMA) scheme is proposed that uses spectral line pairing to generate signals suitable for heterodyne decoding. Both signal and local reference are transmitted via a single optical fiber and a simple balanced receiver performs sourceless heterodyne detection, canceling speckle noise and multiple-access interference (MAI). To validate the idea, a 16 user fully loaded phase encoded system is simulated. Effects of fiber dispersion on system performance are studied as well. Both second and third order dispersion management is achieved by using a spectral phase encoder to adjust phase shifts of spectral components at the optical network unit (ONU).

Spectral tailoring of nanoscale EUV and soft x-ray multilayer optics

Science.gov (United States)

Huang, Qiushi; Medvedev, Viacheslav; van de Kruijs, Robbert; Yakshin, Andrey; Louis, Eric; Bijkerk, Fred

2017-03-01

Extreme ultraviolet and soft X-ray (XUV) multilayer optics have experienced significant development over the past few years, particularly on controlling the spectral characteristics of light for advanced applications like EUV photolithography, space observation, and accelerator- or lab-based XUV experiments. Both planar and three dimensional multilayer structures have been developed to tailor the spectral response in a wide wavelength range. For the planar multilayer optics, different layered schemes are explored. Stacks of periodic multilayers and capping layers are demonstrated to achieve multi-channel reflection or suppression of the reflective properties. Aperiodic multilayer structures enable broadband reflection both in angles and wavelengths, with the possibility of polarization control. The broad wavelength band multilayer is also used to shape attosecond pulses for the study of ultrafast phenomena. Narrowband multilayer monochromators are delivered to bridge the resolution gap between crystals and regular multilayers. High spectral purity multilayers with innovated anti-reflection structures are shown to select spectrally clean XUV radiation from broadband X-ray sources, especially the plasma sources for EUV lithography. Significant progress is also made in the three dimensional multilayer optics, i.e., combining micro- and nanostructures with multilayers, in order to provide new freedom to tune the spectral response. Several kinds of multilayer gratings, including multilayer coated gratings, sliced multilayer gratings, and lamellar multilayer gratings are being pursued for high resolution and high efficiency XUV spectrometers/monochromators, with their advantages and disadvantages, respectively. Multilayer diffraction optics are also developed for spectral purity enhancement. New structures like gratings, zone plates, and pyramids that obtain full suppression of the unwanted radiation and high XUV reflectance are reviewed. Based on the present achievement

Potential of optical spectral transmission measurements for joint inflammation measurements in rheumatoid arthritis patients

Science.gov (United States)

Meier, A. J. Louise; Rensen, Wouter H. J.; de Bokx, Pieter K.; de Nijs, Ron N. J.

2012-08-01

Frequent monitoring of rheumatoid arthritis (RA) patients enables timely treatment adjustments and improved outcomes. Currently this is not feasible due to a shortage of rheumatologists. An optical spectral transmission device is presented for objective assessment of joint inflammation in RA patients, while improving diagnostic accuracy and clinical workflow. A cross-sectional, nonrandomized observational study was performed with this device. In the study, 77 proximal interphalangeal (PIP) joints in 67 patients have been analyzed. Inflammation of these PIP joints was also assessed by a rheumatologist with a score varying from 1 (not inflamed) to 5 (severely inflamed). Out of 77 measurements, 27 were performed in moderate to strongly inflamed PIP joints. Comparison between the clinical assessment and an optical measurement showed a correlation coefficient r=0.63, p<0.001, 95% CI [0.47, 0.75], and a ROC curve (AUC=0.88) that shows a relative good specificity and sensitivity. Optical spectral transmission measurements in a single joint correlate with clinical assessment of joint inflammation, and therefore might be useful in monitoring joint inflammation in RA patients.

Spectral resolution control of acousto-optical cells operating with collimated and divergent beams

Science.gov (United States)

Voloshinov, Vitaly B.; Mishin, Dimitry D.

1994-01-01

The paper is devoted to theoretical and experimental investigations of acousto-optical interactions in crystals which may be used for spectral filtration of light in tunable acousto- optical filters. Attention is paid to spectral resolution control during operation with divergent or collimated noncoherent optical beams. In all examined cases spectral bands of anisotropic Bragg diffraction were regulated by means of novel electronical methods. Resolution control was achieved in paratellurite cells with non-collinear and quasi-collinear regimes of the diffraction. Filtration spectral bandwidths for visible light were electronically changed by a factor of 10 divided by 20 by drive electrical signals switching and drive electrical power regulations.

All-optical OFDM demultiplexing by spectral magnification and band-pass filtering

DEFF Research Database (Denmark)

Palushani, Evarist; Mulvad, Hans Christian Hansen; Kong, Deming

2014-01-01

We propose a simple OFDM receiver allowing for the use of standard WDM receivers to receive spectrally advanced OFDM signals. We propose to spectrally magnify the optical-OFDM super-channels using a spectral telescope consisting of two time-lenses, which enables reduced inter-carrier-interference...

Precision Spectral Manipulation: A Demonstration Using a Coherent Optical Memory

Directory of Open Access Journals (Sweden)

B. M. Sparkes

2012-06-01

Full Text Available The ability to coherently spectrally manipulate quantum information has the potential to improve qubit rates across quantum channels and find applications in optical quantum computing. In this paper, we present experiments that use a multielement solenoid combined with the three-level gradient echo memory scheme to perform precision spectral manipulation of optical pulses. These operations include separate bandwidth and frequency manipulation with precision down to tens of kHz, spectral filtering of up to three separate frequency components, as well as time-delayed interference between pulses with both the same, and different, frequencies. If applied in a quantum information network, these operations would enable frequency-based multiplexing of qubits.

Transfer standard for the spectral density of relative intensity noise of optical fiber sources near 1550 nm

International Nuclear Information System (INIS)

Obarski, Gregory E.; Splett, Jolene D.

2001-01-01

We have developed a transfer standard for the spectral density of relative intensity noise (RIN) of optical fiber sources near 1550 nm. Amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), when it is optically filtered over a narrow band (<5 nm), yields a stable RIN spectrum that is practically constant to several tens of gigahertz. The RIN is calculated from the power spectral density as measured with a calibrated optical spectrum analyzer. For a typical device it is -110 dB/Hz, with uncertainty ≤0.12 dB/Hz. The invariance of the RIN under attenuation yields a considerable dynamic range with respect to rf noise levels. Results are compared with those from a second method that uses a distributed-feedback laser (DFB) that has a Poisson-limited RIN. Application of each method to the same RIN measurement system yields frequency-dependent calibration functions that, when they are averaged, differ by ≤0.2 dB. [copyright] 2001 Optical Society of America

A Method to Analyze the Potential of Optical Remote Sensing for Benthic Habitat Mapping

Directory of Open Access Journals (Sweden)

Rodrigo A. Garcia

2015-10-01

Full Text Available Quantifying the number and type of benthic classes that are able to be spectrally identified in shallow water remote sensing is important in understanding its potential for habitat mapping. Factors that impact the effectiveness of shallow water habitat mapping include water column turbidity, depth, sensor and environmental noise, spectral resolution of the sensor and spectral variability of the benthic classes. In this paper, we present a simple hierarchical clustering method coupled with a shallow water forward model to generate water-column specific spectral libraries. This technique requires no prior decision on the number of classes to output: the resultant classes are optically separable above the spectral noise introduced by the sensor, image based radiometric corrections, the benthos’ natural spectral variability and the attenuating properties of a variable water column at depth. The modeling reveals the effect reducing the spectral resolution has on the number and type of classes that are optically distinct. We illustrate the potential of this clustering algorithm in an analysis of the conditions, including clustering accuracy, sensor spectral resolution and water column optical properties and depth that enabled the spectral distinction of the seagrass Amphibolis antartica from benthic algae.

Spectral and kinetic analysis of radiation induced optical attenuation in silica: towards intrinsic fibre optic dosimetry?

International Nuclear Information System (INIS)

Borgermans, P.

2002-01-01

The document is an abstract of a PhD thesis. The PhD work concerns the detailed investigation of the behaviour of optical fibres in radiation fields such as is the case for various nuclear and space application,s. The core of the work concerns the spectral and kinetic analysis of the radiation induced optical attenuation. Models describing underlying physical phenomena, both for the spectral and the time dimensions, have been developed. The potential of silica optical fibre waveguides for intrinsic dosimetry has been assessed by employing specific properties of radiation induced defects in the silica waveguide material

Introduction of Spectrally and Spatially Flexible Optical Networks

DEFF Research Database (Denmark)

Xia, Tiejun J.; Fevrier, Herve; Wang, Ting

2015-01-01

Given the introduction of coherent 100G systems has provided enough fiber capacity to meet data traffic growth in the near term, enhancing network efficiency will be service providers' high priority. Adding flexibility at the optical layer is a key step to increasing network efficiency, and both...... spectral and spatial functionality will be considered in next generation optical networks along with advanced network management to effectively harness the new capabilities....

ANALYZING SPECTRAL CHARACTERISTICS OF SHADOW AREA FROM ADS-40 HIGH RADIOMETRIC RESOLUTION AERIAL IMAGES

Directory of Open Access Journals (Sweden)

Y.-T. Hsieh

2016-06-01

Full Text Available The shadows in optical remote sensing images are regarded as image nuisances in numerous applications. The classification and interpretation of shadow area in a remote sensing image are a challenge, because of the reduction or total loss of spectral information in those areas. In recent years, airborne multispectral aerial image devices have been developed 12-bit or higher radiometric resolution data, including Leica ADS-40, Intergraph DMC. The increased radiometric resolution of digital imagery provides more radiometric details of potential use in classification or interpretation of land cover of shadow areas. Therefore, the objectives of this study are to analyze the spectral properties of the land cover in the shadow areas by ADS-40 high radiometric resolution aerial images, and to investigate the spectral and vegetation index differences between the various shadow and non-shadow land covers. According to research findings of spectral analysis of ADS-40 image: (i The DN values in shadow area are much lower than in nonshadow area; (ii DN values received from shadowed areas that will also be affected by different land cover, and it shows the possibility of land cover property retrieval as in nonshadow area; (iii The DN values received from shadowed regions decrease in the visible band from short to long wavelengths due to scattering; (iv The shadow area NIR of vegetation category also shows a strong reflection; (v Generally, vegetation indexes (NDVI still have utility to classify the vegetation and non-vegetation in shadow area. The spectral data of high radiometric resolution images (ADS-40 is potential for the extract land cover information of shadow areas.

Transfer standard for the spectral density of relative intensity noise of optical fiber sources near 1550 nm

Energy Technology Data Exchange (ETDEWEB)

Obarski, Gregory E.; Splett, Jolene D.

2001-06-01

We have developed a transfer standard for the spectral density of relative intensity noise (RIN) of optical fiber sources near 1550 nm. Amplified spontaneous emission (ASE) from an erbium-doped fiber amplifier (EDFA), when it is optically filtered over a narrow band ({lt}5 nm), yields a stable RIN spectrum that is practically constant to several tens of gigahertz. The RIN is calculated from the power spectral density as measured with a calibrated optical spectrum analyzer. For a typical device it is {minus}110 dB/Hz, with uncertainty {le}0.12 dB/Hz. The invariance of the RIN under attenuation yields a considerable dynamic range with respect to rf noise levels. Results are compared with those from a second method that uses a distributed-feedback laser (DFB) that has a Poisson-limited RIN. Application of each method to the same RIN measurement system yields frequency-dependent calibration functions that, when they are averaged, differ by {le}0.2 dB. {copyright} 2001 Optical Society of America

Spectral space-time coding for optical communications through a multimode fiber

NARCIS (Netherlands)

Alonso, A.; Berghmans, F.; Thienpont, H.; Danckaert, J.; Desmet, L.

2001-01-01

We propose a method for coding the mode structure of a multimode optical fiber by spectral coding mixed with space-time modulation. With this system we can improve the data carrying capacity of a multimode fiber for optical communications and optical interconnects, and encode and decode the

Spectrally and Energy Efficient OFDM (SEE-OFDM) for Intensity Modulated Optical Wireless Systems

OpenAIRE

Lam, Emily; Wilson, Sarah Kate; Elgala, Hany; Little, Thomas D. C.

2015-01-01

Spectrally and energy efficient orthogonal frequency division multiplexing (SEE-OFDM) is an optical OFDM technique based on combining multiple asymmetrically clipped optical OFDM (ACO-OFDM) signals into one OFDM signal. By summing different components together, SEE-OFDM can achieve the same spectral efficiency as DC-biased optical OFDM (DCO-OFDM) without an energy-inefficient DC-bias. This paper introduces multiple methods for decoding a SEE-OFDM symbol and shows that an iterative decoder wit...

Group velocity measurement using spectral interference in near-field scanning optical microscopy

International Nuclear Information System (INIS)

Mills, John D.; Chaipiboonwong, Tipsuda; Brocklesby, William S.; Charlton, Martin D. B.; Netti, Caterina; Zoorob, Majd E.; Baumberg, Jeremy J.

2006-01-01

Near-field scanning optical microscopy provides a tool for studying the behavior of optical fields inside waveguides. In this experiment the authors measure directly the variation of group velocity between different modes of a planar slab waveguide as the modes propagate along the guide. The measurement is made using the spectral interference between pulses propagating inside the waveguide with different group velocities, collected using a near-field scanning optical microscope at different points down the guide and spectrally resolved. The results are compared to models of group velocities in simple guides

Autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytoma.

Science.gov (United States)

Guerra, Ricardo Luz Leitão; Marback, Eduardo Ferrari; Silva, Igor Sandes Pessoa da; Maia Junior, Otacílio de Oliveira; Marback, Roberto Lorens

2014-01-01

The authors report fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (OCT) findings of two consecutive patients who presented with optic disk melanocytoma (ODM). A retrospective study was performed by reviewing medical records and ophthalmic imaging examinations. Optical coherence tomography findings were sloped and brightly reflective anterior tumor surface, adjacent retinal desorganization and abrupt posterior optical shadowing. Vitreous seeds were found in one patient. Fundus autofluorescence revealed outstanding hypoautofluorescence at the tumor area and isoautofluorescence at the remaining retina. Optical coherence tomography findings of the reported cases are consistent with those reported in the reviewed literature. Fundus autofluorescence has been used in the assessment of choroidal melanocytic tumors, but not yet in melanocytomas. We assume that this is the first report of these findings and believe that when its pattern has become clearly defined, fundus autofluorescence will be a useful tool to avoid misdiagnosis in suspicious cases and for follow-up.

Autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytoma

Directory of Open Access Journals (Sweden)

Ricardo Luz Leitão Guerra

2014-12-01

Full Text Available The authors report fundus autofluorescence (FAF and spectral-domain optical coherence tomography (OCT findings of two consecutive patients who presented with optic disk melanocytoma (ODM. A retrospective study was performed by reviewing medical records and ophthalmic imaging examinations. Optical coherence tomography findings were sloped and brightly reflective anterior tumor surface, adjacent retinal desorganization and abrupt posterior optical shadowing. Vitreous seeds were found in one patient. Fundus autofluorescence revealed outstanding hypoautofluorescence at the tumor area and isoautofluorescence at the remaining retina. Optical coherence tomography findings of the reported cases are consistent with those reported in the reviewed literature. Fundus autofluorescence has been used in the assessment of choroidal melanocytic tumors, but not yet in melanocytomas. We assume that this is the first report of these findings and believe that when its pattern has become clearly defined, fundus autofluorescence will be a useful tool to avoid misdiagnosis in suspicious cases and for follow-up.

Optical spectral weight anomalies and strong correlation

International Nuclear Information System (INIS)

Toschi, A.; Capone, M.; Ortolani, M.; Calvani, P.; Lupi, S.; Castellani, C.

2007-01-01

The anomalous behavior observed in the optical spectral weight (W) of the cuprates provides valuable information about the physics of these compounds. Both the doping and the temperature dependences of W are hardly explained through conventional estimates based on the f-sum rule. By computing the optical conductivity of the doped Hubbard model with the Dynamical Mean Field Theory, we point out that the strong correlation plays a key role in determining the basic features of the observed anomalies: the proximity to a Mott insulating phase accounts simultaneously for the strong temperature dependence of W and for its zero temperature value

Online monitoring of printed electronics by Spectral-Domain Optical Coherence Tomography

KAUST Repository

Alarousu, Erkki; Alsaggaf, Ahmed; Jabbour, Ghassan E.

2013-01-01

Spectral-Domain Optical Coherence Tomography (SD-OCT) is an optical method capable of 3D imaging of object's internal structure with micron-scale resolution. Modern SD-OCT tools offer the speed capable of online monitoring of printed devices

Parametric spectro-temporal analyzer (PASTA) for ultrafast optical performance monitoring

Science.gov (United States)

Zhang, Chi; Wong, Kenneth K. Y.

2013-12-01

Ultrafast optical spectrum monitoring is one of the most challenging tasks in observing ultrafast phenomena, such as the spectroscopy, dynamic observation of the laser cavity, and spectral encoded imaging systems. However, conventional method such as optical spectrum analyzer (OSA) spatially disperses the spectrum, but the space-to-time mapping is realized by mechanical rotation of a grating, so are incapable of operating at high speed. Besides the spatial dispersion, temporal dispersion provided by dispersive fiber can also stretches the spectrum in time domain in an ultrafast manner, but is primarily confined in measuring short pulses. In view of these constraints, here we present a real-time spectrum analyzer called parametric spectro-temporal analyzer (PASTA), which is based on the time-lens focusing mechanism. It achieves a 100-MHz frame rate and can measure arbitrary waveforms. For the first time, we observe the dynamic spectrum of an ultrafast swept-source: Fourier domain mode-locked (FDML) laser, and the spectrum evolution of a laser cavity during its stabilizing process. In addition to the basic single-lens structure, the multi-lens configurations (e.g. telescope or wide-angle scope) will provide a versatile operating condition, which can zoom in to achieve 0.05-nm resolution and zoom out to achieve 10-nm observation range, namely 17 times zoom in/out ratio. In view of the goal of achieving spectrum analysis with fine accuracy, PASTA provides a promising path to study the real-time spectrum of some dynamic phenomena and non-repetitive events, with orders of magnitude enhancement in the frame rate over conventional OSAs.

Relationship Between Optic Nerve Appearance and Retinal Nerve Fiber Layer Thickness as Explored with Spectral Domain Optical Coherence Tomography

Science.gov (United States)

Aleman, Tomas S.; Huang, Jiayan; Garrity, Sean T.; Carter, Stuart B.; Aleman, Wendy D.; Ying, Gui-shuang; Tamhankar, Madhura A.

2014-01-01

Purpose To study the relationship between the appearance of the optic nerve and the retinal nerve fiber layer (RNFL) thickness determined by spectral domain optical coherence tomography (OCT). Methods Records from patients with spectral domain-OCT imaging in a neuro-ophthalmology practice were reviewed. Eyes with glaucoma/glaucoma suspicion, macular/optic nerve edema, pseudophakia, and with refractive errors > 6D were excluded. Optic nerve appearance by slit lamp biomicroscopy was related to the RNFL thickness by spectral domain-OCT and to visual field results. Results Ninety-one patients (176 eyes; mean age: 49 ± 15 years) were included. Eighty-three eyes (47%) showed optic nerve pallor; 89 eyes (50.6%) showed RNFL thinning (sectoral or average peripapillary). Average peripapillary RNFL thickness in eyes with pallor (mean ± SD = 76 ± 17 μm) was thinner compared to eyes without pallor (91 ± 14 μm, P < 0.001). Optic nerve pallor predicted RNFL thinning with a sensitivity of 69% and a specificity of 75%. Optic nerve appearance predicted RNFL thinning (with a sensitivity and specificity of 81%) when RNFL had thinned by ∼ 40%. Most patients with pallor had RNFL thinning with (66%) or without (25%) visual field loss; the remainder had normal RNFL and fields (5%) or with visual field abnormalities (4%). Conclusions Optic nerve pallor as a predictor of RNFL thinning showed fair sensitivity and specificity, although it is optimally sensitive/specific only when substantial RNFL loss has occurred. Translational Relevance Finding an acceptable relationship between the optic nerve appearance by ophthalmoscopy and spectral domain-OCT RNFL measures will help the clinician's interpretation of the information provided by this technology, which is gaining momentum in neuro-ophthalmic research. PMID:25374773

Digital nonlinearity compensation in high-capacity optical communication systems considering signal spectral broadening effect.

Science.gov (United States)

Xu, Tianhua; Karanov, Boris; Shevchenko, Nikita A; Lavery, Domaniç; Liga, Gabriele; Killey, Robert I; Bayvel, Polina

2017-10-11

Nyquist-spaced transmission and digital signal processing have proved effective in maximising the spectral efficiency and reach of optical communication systems. In these systems, Kerr nonlinearity determines the performance limits, and leads to spectral broadening of the signals propagating in the fibre. Although digital nonlinearity compensation was validated to be promising for mitigating Kerr nonlinearities, the impact of spectral broadening on nonlinearity compensation has never been quantified. In this paper, the performance of multi-channel digital back-propagation (MC-DBP) for compensating fibre nonlinearities in Nyquist-spaced optical communication systems is investigated, when the effect of signal spectral broadening is considered. It is found that accounting for the spectral broadening effect is crucial for achieving the best performance of DBP in both single-channel and multi-channel communication systems, independent of modulation formats used. For multi-channel systems, the degradation of DBP performance due to neglecting the spectral broadening effect in the compensation is more significant for outer channels. Our work also quantified the minimum bandwidths of optical receivers and signal processing devices to ensure the optimal compensation of deterministic nonlinear distortions.

Spectral-domain optical coherence tomography of roth spots.

Science.gov (United States)

Giovinazzo, Jerome; Mrejen, Sarah; Freund, K Bailey

2013-01-01

To describe the retinal findings of subacute bacterial endocarditis, their evolution after treatment, and analysis with spectral-domain optical coherence tomography. Retrospective chart review. A 21-year-old man presented with the sudden onset of a central scotoma in his left eye because of a sub-internal limiting membrane hemorrhage overlying the left fovea. When examined 2 weeks later, Roth spots were noted in his right eye. The patient was immediately referred to his internist and diagnosed with subacute bacterial endocarditis with cultures positive for Streptococcus viridans. He subsequently underwent aortic valve replacement surgery after 4 weeks of intravenous antibiotic therapy. When examined 4 weeks after valve replacement surgery, there was regression of the Roth spots. The present case demonstrates the importance of a funduscopic examination in the early diagnosis and management of subacute bacterial endocarditis. The analysis of Roth spots with spectral-domain optical coherence tomography suggested that they were septic emboli.

Spectrally efficient polymer optical fiber transmission

Science.gov (United States)

Randel, Sebastian; Bunge, Christian-Alexander

2011-01-01

The step-index polymer optical fiber (SI-POF) is an attractive transmission medium for high speed communication links in automotive infotainment networks, in industrial automation, and in home networks. Growing demands for quality of service, e.g., for IPTV distribution in homes and for Ethernet based industrial control networks will necessitate Gigabit speeds in the near future. We present an overview on recent advances in the design of spectrally efficient and robust Gigabit-over-SI-POF transmission systems.

The development of MOSA-II multichannel optical spectrum analyzer

International Nuclear Information System (INIS)

Guo Li; Yang Zhoujing; Fang Shuyao

1989-01-01

The MOSA-II Multichannel Optical Spectrum Analyzer is a high-perfor mance, easy-to-use measurment system for extremely rapid spectral data acquistion, processing and presentation. It consists of four parts: vidicon, data acquiring and timing circuit, the correcting circuit for the geometric distortion and the non-uniform distortion of the vidicon, IBMPC/XT and color plotter. The system has the following functions: single spectrum acquisition, continuous acquisition of multi-spectra, noise reduction, math, operations (including addition, subtraction, multiplication, and division) and geometric transform action of the spectra, and 3D-presentation of the spectra on both the color screen and the plotter. The absolute sensitivity of the system is 18 Photons/sec · mm 2 . The access time for data acquisition is 64 μs/per channel and the spectrum range is 1800 A - 8000A, the geometric distortion<2%, the amplitude error<5%

Extended depth of focus adaptive optics spectral domain optical coherence tomography

Science.gov (United States)

Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

2012-01-01

We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the applied SA. PMID:23082278

640 Gbit/s return-to-zero to non-return-to-zero format conversion based on optical linear spectral phase filtering

DEFF Research Database (Denmark)

Maram, Reza; Kong, Deming; Galili, Michael

2016-01-01

We propose a novel approach for all-optical return-to-zero (RZ) to non-return-to-zero (NRZ) telecommunication data format conversion based on linear spectral phase manipulation of an RZ data signal. The operation principle is numerically analyzed and experimentally validated through successful fo...

Submicron Resolution Spectral-Domain Optical Coherence Tomography

KAUST Repository

Alarousu, Erkki

2013-11-14

Apparatuses and systems for submicron resolution spectral-domain optical coherence tomography (OCT) are disclosed. The system may use white light sources having wavelengths within 400-1000 nanometers, and achieve resolution below 1 .mu.m. The apparatus is aggregated into a unitary piece, and a user can connect the apparatus to a user provided controller and/or light source. The light source may be a supercontinuum source.

Optical spectral signatures of liquids by means of fiber optic technology for product and quality parameter identification

Science.gov (United States)

Mignani, A. G.; Ciaccheri, L.; Mencaglia, A. A.; Diaz-Herrera, N.; Garcia-Allende, P. B.; Ottevaere, H.; Thienpont, H.; Attilio, C.; Cimato, A.; Francalanci, S.; Paccagnini, A.; Pavone, F. S.

2009-01-01

Absorption spectroscopy in the wide 200-1700 nm spectral range is carried out by means of optical fiber instrumentation to achieve a digital mapping of liquids for the prediction of important quality parameters. Extra virgin olive oils from Italy and lubricant oils from turbines with different degrees of degradation were considered as "case studies". The spectral data were processed by means of multivariate analysis so as to obtain a correlation to quality parameters. In practice, the wide range absorption spectra were considered as an optical signature of the liquids from which to extract product quality information. The optical signatures of extra virgin olive oils were used to predict the content of the most important fatty acids. The optical signatures of lubricant oils were used to predict the concentration of the most important parameters for indicating the oil's degree of degradation, such as TAN, JOAP anti-wear index, and water content.

Receiver sensitivity improvement in spectrally-efficient guard-band twin-SSB-OFDM using an optical IQ modulator

Science.gov (United States)

Chen, Ming; Peng, Miao; Zhou, Hui; Zheng, Zhiwei; Tang, Xionggui; Maivan, Lap

2017-12-01

To further improve receiver sensitivity of spectrally-efficient guard-band direct-detection optical orthogonal frequency-division multiplexing (OFDM) with twin single-side-band (SSB) modulation technique, an optical IQ modulator (IQM) is employed to optimize optical carrier-to-signal power ratio (CSPR). The CSPRs for the guard-band twin-SSB-OFDM signal generated by using dual-drive Mach-Zehnder modulator (DD-MZM) and optical IQM are theoretically analyzed and supported by simulations. The optimal CSPR for the two types of guard-band twin-SSB-OFDM are identified. The simulations exhibit that the error vector magnitude (EVM) performance of the IQM-enabled guard-band twin-SSB-OFDM is improved by more than 4-dB compared to that of the twin-SSB-OFDM enabled by DD-MZM after 80-km single-mode fiber (SMF) transmission. In addition, more than 3-dB and 10 dB receiver sensitivity improvements in terms of received optical power (ROP) and optical signal-to-noise ratio (OSNR) are also achieved, respectively.

Time Lens based Optical Fourier Transformation for All-Optical Signal Processing of Spectrally-Efficient Data

DEFF Research Database (Denmark)

Guan, Pengyu; Røge, Kasper Meldgaard; Lillieholm, Mads

2017-01-01

We review recent progress in the use of time lens based optical Fourier transformation for advanced all-optical signal processing. A novel time lens based complete optical Fourier transformation (OFT) technique is introduced. This complete OFT is based on two quadratic phase-modulation stages using...... four-wave mixing (FWM), separated by a dispersive medium, which enables time-to-frequency and frequency-to-time conversions simultaneously, thus performing an exchange between the temporal and spectral profiles of the input signal. Using the proposed complete OFT, several advanced all-optical signal......, such as orthogonal frequency division multiplexing (OFDM), Nyquist wavelength-division multiplexing (Nyquist-WDM) and Nyquist optical time division multiplexing (Nyquist-OTDM) signals....

Spectral-optical characteristics of anthocyanin-containing natural dye staff

International Nuclear Information System (INIS)

Astanov, S.; Sharipov, M.Z.; Dalmuradova, N.N.

2007-01-01

Spectral-optical characteristics of anthocyanin-containing natural dye staff received from fruit ficus carica are determined. The chromatographic separating of dyeing pigment obtained is performed. The data obtained can be used as passport characteristics of the new food dye staff. (authors)

Time lens based optical fourier transformation for advanced processing of spectrally-efficient OFDM and N-WDM signals

DEFF Research Database (Denmark)

Guan, Pengyu; Røge, Kasper Meldgaard; Morioka, Toshio

2016-01-01

We review recent progress in the use of time lens based optical Fourier transformation for advanced optical signal processing, with focus on all-optical generation, detection and format conversion of spectrally-efficient OFDM and N-WDM signals.......We review recent progress in the use of time lens based optical Fourier transformation for advanced optical signal processing, with focus on all-optical generation, detection and format conversion of spectrally-efficient OFDM and N-WDM signals....

Spectral domain optical coherence tomography morphology in optic disc pit associated maculopathy

Directory of Open Access Journals (Sweden)

Janusz Michalewski

2014-01-01

Full Text Available Purpose: Our purpose was to study the clinical manifestation and course of optic pit maculopathy using Spectral Domain Optical Coherence Tomography (SD- OCT images. Materials and Methods: We used SD-OCT to examine 20 eyes of 19 patients with a macular detachment in combination with an optic. Results: We observed five different fovea appearances in regard to fluid localization. In five eyes, we recorded changes in the fluid distribution with SD-OCT. In 17/20 eyes, we noted a communication between the perineural and subretinal and/or intraretinal space at the margin of the optic disc. Conclusion: 3-dimensional SD-OCT (3D-SDOCT scans revealed a three-fold connection, between subretinal and intraretinal space, perineural space, and the vitreous cavity. Therefore, we suppose that intraretinal or subretinal fluid in optic pit maculopathy may have both a vitreous and cerebrospinal origin. A membrane, covering the optic nerve was noted in 14 cases. Even if it seems intact in some B-scans, it is not complete in others several micrometers apart. Additionally, we observed fluid accumulation below the margin of the optic disc and hyperreflective porous tissue in the optic disc excavation. Those findings do not influence the course of maculopathy.

OTDM-WDM Conversion Based on Time-Domain Optical Fourier Transformation with Spectral Compression

DEFF Research Database (Denmark)

Mulvad, Hans Christian Hansen; Palushani, Evarist; Galili, Michael

2011-01-01

We propose a scheme enabling direct serial-to-parallel conversion of OTDM data tributaries onto a WDM grid, based on optical Fourier transformation with spectral compression. Demonstrations on 320 Gbit/s and 640 Gbit/s OTDM data are shown.......We propose a scheme enabling direct serial-to-parallel conversion of OTDM data tributaries onto a WDM grid, based on optical Fourier transformation with spectral compression. Demonstrations on 320 Gbit/s and 640 Gbit/s OTDM data are shown....

Extraction of optical parameters of thin films from spectral measurements for design and optical performance of multilayer structures

International Nuclear Information System (INIS)

Muellerova, J.; Jurecka, S.; Kucerova, A.

2003-01-01

Optical parameters of a-Si:H and indium tin oxide (ITO) thin films deposited on glass substrates are determined from spectral measurements of reflectance and/or transmittance. It is shown how important the exact knowledge of optical parameters as well as thicknesses of the layers for the design and the optical performance of multilayer structures is. The model of the p-i-n based a:Si-H solar cell with ITO as transparent conductive oxide layer is used for illustrating. The modeling of the solar cell integral reflectance in the spectral region of (650-830) nm is used as a criterion to reverse engineering of a multilayer structure with suppressed reflectance losses. The reflectance of a solar cell is modelled and the simulation of the varying optical parameters of individual layers including their thicknesses is discussed. Besides this,the advantage of using an antireflective layer under ITO is discussed (Authors)

Optically transparent multiple access networks employing incoherent spectral codes

NARCIS (Netherlands)

Huiszoon, B.

2008-01-01

This Ph.D. thesis is divided into 7 chapters to provide the reader an overview of the main results achieved in di®erent sub-topics of the study towards optically transparent multiple access networks employing incoherent spectral codes taking into account wireless transmission aspects. The work

Technologies for Elastic Optical Networking Systems in Spatial, Temporal and Spectral Domains

Science.gov (United States)

Qin, Chuan

As the demand for more data capacity keeps increasing, the need for the more efficient use of the data channel becomes more imperative. The fixed wavelength grid which has been in use for more than ten years in conventional wavelength division multiplexing (WDM) is a bottleneck that prevents the capacity from upgrading towards 400 Gb/s and above. A new elastic optical networking scheme where both transceivers and interconnects become flexible break the boundary of wavelength grids and allow a more efficient use of the limited optical bands for communication. This dissertation focuses on a few enabling technologies for elastic optical networking systems. Optical arbitrary waveform generation (OAWG) uses Fourier synthesis and generates user-defined broad-band scalable optical waveforms with high-fidelity through line-by-line full field control of a coherent optical frequency comb. OAWG finds its niche in elastic optical networking since it provides no grids, and scales to user-defined bandwidth. When elastic optical networking builds various connections to use an arbitrary number of subcarriers depending on the users' bandwidth needs, the flexibility also creates non-contiguous spectral fragmentation, much like a computer hard disk generating fragments. Spectral defragmentation aims to re-optimize and re-assign the optical spectrum to achieve more efficient use of the spectrum. One of the technologies is "hop tuning" defragmentation method with a fast auto-tracking local oscillator (LO). In the demonstrated defragmentation experiment, I used a field-programmable gate array (FPGA) to monitor the wavelength change in the signal laser and tune the front and rear current that controls the wavelength of the local oscillator laser. However, the control of the front and rear current needs a complete and accurate calibration of the LO laser and may not apply to a larger number of coherent communication links. A single-tone optical frequency shifter can shift the LO laser

Growth, spectral and optical characterization of a novel nonlinear optical organic material: D-Alanine DL-Mandelic acid single crystal

Science.gov (United States)

Jayaprakash, P.; Mohamed, M. Peer; Caroline, M. Lydia

2017-04-01

An organic nonlinear optical single crystal, D-alanine DL-mandelic acid was synthesized and successfully grown by slow evaporation solution growth technique at ambient temperature using solvent of aqueous solution. The unit cell parameters were assessed from single crystal X-ray diffraction analysis. The presence of diverse functional groups and vibrational modes were identified using Fourier Transform Infra Red and Fourier Transform Raman spectral analyses. The chemical structure of grown crystal has been identified by Nuclear Magnetic Resonance spectroscopic study. Ultraviolet-visible spectral analysis reveal that the crystal has lower cut-off wavelength down to 259 nm, is a key factor to exhibit second harmonic generation signal. The electronic optical band gap and Urbach energy is calculated as 5.31 eV and 0.2425 eV respectively from the UV absorption profile. The diverse optical properties such as, extinction coefficient, reflectance, linear refractive index, optical conductivity was calculated using UV-visible data. The relative second harmonic efficiency of the compound is found to be 0.81 times greater than that of KH2PO4 (KDP). The thermal stability of the grown crystal was studied by thermogravimetric analysis and differential thermal analysis techniques. The luminescence spectrum exhibited two peaks (520 nm, 564 nm) due to the donation of protons from carboxylic acid to amino group. The Vickers microhardness test was carried out employing one of the as-grown hard crystal and there by hardness number (Hv), Meyer's index (n), yield strength (σy), elastic stiffness constant (C11) and Knoop hardness number (HK) were assessed. The dielectric behaviour of the as-grown crystal was analyzed for different temperatures (313 K, 333 K, 353 K, and 373 K) at different frequencies.

Using spectral methods to obtain particle size information from optical data: applications to measurements from CARES 2010

Science.gov (United States)

Atkinson, Dean B.; Pekour, Mikhail; Chand, Duli; Radney, James G.; Kolesar, Katheryn R.; Zhang, Qi; Setyan, Ari; O'Neill, Norman T.; Cappa, Christopher D.

2018-04-01

Multi-wavelength in situ aerosol extinction, absorption and scattering measurements made at two ground sites during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) are analyzed using a spectral deconvolution method that allows extraction of particle-size-related information, including the fraction of extinction produced by the fine-mode particles and the effective radius of the fine mode. The spectral deconvolution method is typically applied to analysis of remote sensing measurements. Here, its application to in situ measurements allows for comparison with more direct measurement methods and validation of the retrieval approach. Overall, the retrieved fine-mode fraction and effective radius compare well with other in situ measurements, including size distribution measurements and scattering and absorption measurements made separately for PM1 and PM10, although there were some periods during which the different methods yielded different results. One key contributor to differences between the results obtained is the alternative, spectrally based definitions of fine and coarse modes from the optical methods, relative to instruments that use a physically defined cut point. These results indicate that for campaigns where size, composition and multi-wavelength optical property measurements are made, comparison of the results can result in closure or can identify unusual circumstances. The comparison here also demonstrates that in situ multi-wavelength optical property measurements can be used to determine information about particle size distributions in situations where direct size distribution measurements are not available.

Using spectral methods to obtain particle size information from optical data: applications to measurements from CARES 2010

Directory of Open Access Journals (Sweden)

D. B. Atkinson

2018-04-01

Full Text Available Multi-wavelength in situ aerosol extinction, absorption and scattering measurements made at two ground sites during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES are analyzed using a spectral deconvolution method that allows extraction of particle-size-related information, including the fraction of extinction produced by the fine-mode particles and the effective radius of the fine mode. The spectral deconvolution method is typically applied to analysis of remote sensing measurements. Here, its application to in situ measurements allows for comparison with more direct measurement methods and validation of the retrieval approach. Overall, the retrieved fine-mode fraction and effective radius compare well with other in situ measurements, including size distribution measurements and scattering and absorption measurements made separately for PM1 and PM10, although there were some periods during which the different methods yielded different results. One key contributor to differences between the results obtained is the alternative, spectrally based definitions of fine and coarse modes from the optical methods, relative to instruments that use a physically defined cut point. These results indicate that for campaigns where size, composition and multi-wavelength optical property measurements are made, comparison of the results can result in closure or can identify unusual circumstances. The comparison here also demonstrates that in situ multi-wavelength optical property measurements can be used to determine information about particle size distributions in situations where direct size distribution measurements are not available.

Research on the strong optical feedback effects based on spectral analysis method

Science.gov (United States)

Zeng, Zhaoli; Qu, XueMin; Li, Weina; Zhang, Min; Wang, Hao; Li, Tuo

2018-01-01

The strong optical feedback has the advantage of generating high resolution fringes. However, these feedback fringes usually seem like the noise signal when the feedback level is high. This defect severely limits its practical application. In this paper, the generation mechanism of noise fringes with strong optical feedback is studied by using spectral analysis method. The spectral analysis results show that, in most cases, the noise-like fringes are observed owing to the strong multiple high-order feedback. However, at certain feedback cavity condition, there may be only one high-order feedback beam goes back to the laser cavity, the noise-like fringes can change to the cosine-like fringes. And the resolution of this fringe is dozens times than that of the weak optical feedback. This research provides a method to obtain high resolution cosine-like fringes rather than noise signal in the strong optical feedback, which makes it possible to be used in nanoscale displacement measurements.

Thin film optical coatings for the ultraviolet spectral region

Science.gov (United States)

Torchio, P.; Albrand, G.; Alvisi, M.; Amra, C.; Rauf, H.; Cousin, B.; Otrio, G.

2017-11-01

The applications and innovations related to the ultraviolet field are today in strong growth. To satisfy these developments which go from biomedical to the large equipment like the Storage Ring Free Electron Laser, it is crucial to control with an extreme precision the optical performances, in using the substrates and the thin film materials impossible to circumvent in this spectral range. In particular, the reduction of the losses by electromagnetic diffusion, Joule effect absorption, or the behavior under UV luminous flows of power, resistance to surrounding particulate flows... become top priority which concerns a broad European and international community. Our laboratory has the theoretical, experimental and technological tools to design and fabricate numerous multilayer coatings with desirable optical properties in the visible and infrared spectral ranges. We have extended our expertise to the ultraviolet. We present here some results on high reflectivity multidielectric mirrors towards 250 nm in wavelength, produced by Ion Plating Deposition. The latter technique allows us to obtain surface treatments with low absorption and high resistance. We give in this study the UV transparent materials and the manufacturing technology which have been the best suited to meet requirements. Single UV layers were deposited and characterized. HfO2/SiO2 mirrors with a reflectance higher than 99% at 300 nm were obtained. Optical and non-optical characterizations such as UV spectrophotometric measurements, X-Ray Diffraction spectra, Scanning Electron Microscope and Atomic Force Microscope images were performed

Measuring and analyzing excitation-induced decoherence in rare-earth-doped optical materials

International Nuclear Information System (INIS)

Thiel, C W; Macfarlane, R M; Cone, R L; Sun, Y; Böttger, T; Sinclair, N; Tittel, W

2014-01-01

A method is introduced for quantitatively analyzing photon echo decay measurements to characterize excitation-induced decoherence resulting from the phenomenon of instantaneous spectral diffusion. Detailed analysis is presented that allows fundamental material properties to be extracted that predict and describe excitation-induced decoherence for a broad range of measurements, applications and experimental conditions. Motivated by the need for a method that enables systematic studies of ultra-low decoherence systems and direct comparison of properties between optical materials, this approach employs simple techniques and analytical expressions that avoid the need for difficult to measure and often unknown material parameters or numerical simulations. This measurement and analysis approach is demonstrated for the 3 H 6 to 3 H 4 optical transition of three thulium-doped crystals, Tm 3+ :YAG, Tm 3+ :LiNbO 3 and Tm 3+ :YGG, that are currently employed in quantum information and classical signal processing demonstrations where minimizing decoherence is essential to achieve high efficiencies and large signal bandwidths. These new results reveal more than two orders of magnitude variation in sensitivity to excitation-induced decoherence among the materials studied and establish that the Tm 3+ :YGG system offers the longest optical coherence lifetimes and the lowest levels of excitation-induced decoherence yet observed for any known thulium-doped material. (paper)

Thin film and multilayer optics for XUV spectral domain (1 nm to 60 nm)

International Nuclear Information System (INIS)

Delmotte, Franck

2010-02-01

The XUV spectral domain (1-60 nm wavelength range) has experienced rapid growth in recent years. On one side, the sources (synchrotron radiation, harmonic generation, x-ray laser, free-electron laser...) require ever more efficient optics, on the other hand, applications (diagnostics of hot plasma, solar physics, x-ray microscopy, EUV lithography, x-ray analysis...) provide new constraints on the design of multilayer stacks. The multilayer mirrors are the only way to achieve efficient optics operating at non-grazing incidence angles in this spectral range. Our work within the team XUV Optics at Laboratoire Charles Fabry de l'Institut d'Optique focuses on the study of materials in thin layers correlated to the study of optical properties of multilayers. The objective is to achieve new multilayer components previously unavailable in the XUV domain, through a better understanding of physical phenomena in these nano-layer stacks. We show through several examples of how we have managed both to improve the performance of multilayer mirrors in a broad spectral range, and secondly, to develop new optical functions: beam splitters, broadband mirrors, dual-band mirrors or phase compensation mirrors. (author)

Optical CDMA with Embedded Spectral-Polarization Coding over Double Balanced Differential-Detector

Science.gov (United States)

Huang, Jen-Fa; Yen, Chih-Ta; Chen, Bo-Hau

A spectral-polarization coding (SPC) optical code-division multiple-access (OCDMA) configuration structured over arrayed-waveguide grating (AWG) router is proposed. The polarization-division double balanced detector is adopted to execute difference detection and enhances system performance. The signal-to-noise ratio (SNR) is derived by taking the effect of PIIN into account. The result indicates that there would be up to 9-dB SNR improvement than the conventional spectral-amplitude coding (SAC) structures with Walsh-Hadamard codes. Mathematical deriving results of the SNR demonstrate the system embedded with the orthogonal state of polarization (SOP) will suppress effectively phase-induced intensity noise (PIIN). In addition, we will analyze the relations about bit error rate (BER) vs. the number of active users under the different encoding schemes and compare them with our proposed scheme. The BER vs. the effective power under the different encoding scheme with the same number of simultaneous active user conditions are also revealed. Finally, the polarization-matched factor and the difference between simulated and experimental values are discussed.

Design of integrated optics all-optical label swappers for spectral amplitude code label swapping optical packet networks on active/passive InP technology

NARCIS (Netherlands)

Habib, C.; Munoz, P.; Leijtens, X.J.M.; Chen, Lawrence; Smit, M.K.; Capmany, J.

2009-01-01

In this paper the designs of optical label swapper devices, for spectral amplitude coded labels, monolithically integrated on InP active/passive technology are pre sented. The devices are based on cross-gain modulation in a semiconductor optical amplifier. Multi-wavelength operation is enabled by

Clinical manifestations of optic pit maculopathy as demonstrated by spectral domain optical coherence tomography

Directory of Open Access Journals (Sweden)

Tzu JH

2013-01-01

Full Text Available Jonathan H Tzu, Harry W Flynn Jr, Audina M Berrocal, William E Smiddy, Timothy G Murray, Yale L FisherDepartment of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USAPurpose: The purpose of this retrospective study was to evaluate the characteristic features, including spectral-domain optical coherence tomography (SD-OCT, clinical course, and outcome of treatment if given for patients with optic disc pit maculopathy.Methods: We investigated a consecutive series of patients with a diagnosis of optic pit maculopathy treated between 2001 and 2012 at the Bascom Palmer Eye Institute. Patients were divided into two main groups, ie, patients who were observed without surgery and patients who received surgical intervention. The main outcome measures were presenting and final visual acuity, and changes in SD-OCT imaging were recorded. Other data including age, gender, eye, age of onset, length of follow-up, location of optic pit, and location of fluid by OCT were also recorded.Results: On OCT, 67% (12/18 of the eyes showed schisis-like cavities, 22% (4/18 had only subretinal fluid, and 17% (3/18 had only a schisis-like cavity without subretinal fluid. In the patients managed by observation, visual acuity was ≥20/200 in 6/8 eyes initially and 6/8 eyes at last follow-up. Ten of 18 patients received either focal laser, surgery or both. Six of 10 eyes undergoing surgery had initial visual acuity ≥ 20/200, and 8 of 10 eyes undergoing surgery had a visual acuity of ≥20/200 at last follow-up.Conclusion: In this study, many eyes were observed and remained stable during follow-up. In eyes with reduced vision, surgical intervention produced variable outcomes, and persistent intraretinal/subretinal fluid was a common occurrence.Keywords: optic pit maculopathy, spectral-domain optical coherence tomography

Optical decoherence times and spectral diffusion in an Er-doped optical fiber measured by two-pulse echoes, stimulated photon echoes, and spectral hole burning

International Nuclear Information System (INIS)

Macfarlane, R.M.; Sun, Y.; Sellin, P.B.; Cone, R.L.

2007-01-01

Two-pulse and stimulated photon echoes and spectral hole burning were measured on the transition from the lowest component of the 4 I 15/2 manifold to the lowest component of 4 I 13/2 of Er 3+ in a silicate optical fiber at 1.6 K. The two-pulse echo decays gave decoherence times as long as 230 ns for magnetic fields above 2 T. A large field dependent contribution to the homogeneous line width of >2 MHz was found and interpreted in terms of coupling to magnetic tunneling modes (TLS) in the glass. The stimulated echoes measured at 2 T showed spectral diffusion of 0.8 MHz/decade of time between 0.4 and 500 μs. Spectral diffusion in this high field region is attributed to coupling to elastic TLS modes which have a distribution of flip rates in glasses. Time-resolved spectral hole burning at very low field showed stronger spectral diffusion of 5.7 MHz/decade of time, attributed to coupling to magnetic spin-elastic TLS modes

Multiplex CARS imaging with spectral notch shaped laser pulses delivered by optical fibers.

Science.gov (United States)

Oh, Seung Ryeol; Park, Joo Hyun; Kim, Kyung-Soo; Lee, Jae Yong; Kim, Soohyun

2017-12-11

We present an experimental demonstration of single-pulse coherent anti-Stokes Raman spectroscopy (CARS) using a spectrally shaped broadband laser that is delivered by an optical fiber to a sample at its distal end. The optical fiber consists of a fiber Bragg grating component to serve as a narrowband notch filter and a combined large-mode-area fiber to transmit such shaped ultrashort laser pulses without spectral distortion in a long distance. Experimentally, our implementation showed a capability to measure CARS spectra of various samples with molecular vibrations in the fingerprint region. Furthermore, CARS imaging of poly(methyl methacrylate) bead samples was carried out successfully under epi-CARS geometry in which backward-scattered CARS signals were collected into a multimode optical fiber. A compatibility of single-pulse CARS scheme with fiber optics, verified in this study, implies a potential for future realization of compact all-fiber CARS spectroscopic imaging systems.

Impact of initial pulse shape on the nonlinear spectral compression in optical fibre

Science.gov (United States)

Boscolo, Sonia; Chaussard, Frederic; Andresen, Esben; Rigneault, Hervé; Finot, Christophe

2018-02-01

We theoretically study the effects of the temporal intensity profile of the initial pulse on the nonlinear propagation spectral compression process arising from nonlinear propagation in an optical fibre. Various linearly chirped input pulse profiles are considered, and their dynamics is explained with the aid of time-frequency representations. While initially parabolic-shaped pulses show enhanced spectral compression compared to Gaussian pulses, no significant spectral narrowing occurs when initially super-Gaussian pulses are used. Triangular pulses lead to a spectral interference phenomenon similar to the Fresnel bi-prism experiment.

Optical microwave filter based on spectral slicing by use of arrayed waveguide gratings.

Science.gov (United States)

Pastor, Daniel; Ortega, Beatriz; Capmany, José; Sales, Salvador; Martinez, Alfonso; Muñoz, Pascual

2003-10-01

We have experimentally demonstrated a new optical signal processor based on the use of arrayed waveguide gratings. The structure exploits the concept of spectral slicing combined with the use of an optical dispersive medium. The approach presents increased flexibility from previous slicing-based structures in terms of tunability, reconfiguration, and apodization of the samples or coefficients of the transversal optical filter.

Spectral-domain optical coherence tomography staging and autofluorescence imaging in achromatopsia.

Science.gov (United States)

Greenberg, Jonathan P; Sherman, Jerome; Zweifel, Sandrine A; Chen, Royce W S; Duncker, Tobias; Kohl, Susanne; Baumann, Britta; Wissinger, Bernd; Yannuzzi, Lawrence A; Tsang, Stephen H

2014-04-01

IMPORTANCE Evidence is mounting that achromatopsia is a progressive retinal degeneration, and treatments for this condition are on the horizon. OBJECTIVES To categorize achromatopsia into clinically identifiable stages using spectral-domain optical coherence tomography and to describe fundus autofluorescence imaging in this condition. DESIGN, SETTING, AND PARTICIPANTS A prospective observational study was performed between 2010 and 2012 at the Edward S. Harkness Eye Institute, New York-Presbyterian Hospital. Participants included 17 patients (aged 10-62 years) with full-field electroretinography-confirmed achromatopsia. MAIN OUTCOMES AND MEASURES Spectral-domain optical coherence tomography features and staging system, fundus autofluorescence and near-infrared reflectance features and their correlation to optical coherence tomography, and genetic mutations served as the outcomes and measures. RESULTS Achromatopsia was categorized into 5 stages on spectral-domain optical coherence tomography: stage 1 (2 patients [12%]), intact outer retina; stage 2 (2 patients [12%]), inner segment ellipsoid line disruption; stage 3 (5 patients [29%]), presence of an optically empty space; stage 4 (5 patients [29%]), optically empty space with partial retinal pigment epithelium disruption; and stage 5 (3 patients [18%]), complete retinal pigment epithelium disruption and/or loss of the outer nuclear layer. Stage 1 patients showed isolated hyperreflectivity of the external limiting membrane in the fovea, and the external limiting membrane was hyperreflective above each optically empty space. On near infrared reflectance imaging, the fovea was normal, hyporeflective, or showed both hyporeflective and hyperreflective features. All patients demonstrated autofluorescence abnormalities in the fovea and/or parafovea: 9 participants (53%) had reduced or absent autofluorescence surrounded by increased autofluorescence, 4 individuals (24%) showed only reduced or absent autofluorescence, 3

Optical decoherence and persistent spectral hole burning in Er3+:LiNbO3

International Nuclear Information System (INIS)

Thiel, C.W.; Macfarlane, R.M.; Boettger, T.; Sun, Y.; Cone, R.L.; Babbitt, W.R.

2010-01-01

Developing new resonant optical materials for spatial-spectral holography and quantum information applications requires detailed knowledge of the decoherence and population relaxation dynamics for the quantum states involved in the optical transitions, motivating the need for fundamental material studies. We report recent progress in studying these properties in erbium-doped lithium niobate at liquid helium temperatures. The influence of temperature, applied magnetic fields, measurement timescale, and dopant concentration were probed using photon echo spectroscopy and time-resolved spectral hole burning on the 1532 nm transition of Er 3+ :LiNbO 3 . Effects of spectral diffusion due to interactions between Er 3+ ions and between the Er 3+ ion and 7 Li and 93 Nb nuclear spins in the host lattice were observed. In addition, long-lived persistent spectral storage of seconds to minutes was observed due to non-equilibrium population redistribution among superhyperfine states.

Single interval shortwave radiation scheme with parameterized optical saturation and spectral overlaps

Czech Academy of Sciences Publication Activity Database

Mašek, Jan; Geleyn, J.- F.; Brožková, Radmila; Giot, O.; Achom, H. O.; Kuma, P.

2016-01-01

Roč. 142, č. 659 (2016), s. 304-326 ISSN 0035-9009 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : shortwave radiative transfer * delta-two stream system * broadband approach * Malkmus band model * optical saturation * idealized optical paths * spectral overlap Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.444, year: 2016

An optical modulation format generation scheme based on spectral filtering and frequency-to-time mapping

Institute of Scientific and Technical Information of China (English)

ZHANG Ai-ling; ZHANG Yue; SONG Hong-yun; YAO Yuan; PAN Hong-gang

2018-01-01

An optical modulation format generation scheme based on spectral filtering and frequency-to-time mapping is experimentally demonstrated.Many modulation formats with continuously adjustable duty radio and bit rate can be formed by changing the dispersion of dispersion element and the bandwidth of shaped spectrum in this scheme.In the experiment,non-return-to-zero (NRZ) signal with bit rate of 29.41 Gbit/s and 1/2 duty ratio return-to-zero (RZ) signal with bit rate of 13.51 Gbit/s are obtained.The maximum bit rate of modulation format signal is also analyzed.

Linear and nonlinear optical spectroscopy: Spectral, temporal and spatial resolution

DEFF Research Database (Denmark)

Hvam, Jørn Marcher

1997-01-01

Selected linear and nonlinear optical spectroscopies are being described with special emphasis on the possibility of obtaining simultaneous spectral, temporal and spatial resolution. The potential of various experimental techniques is being demonstrated by specific examples mostly taken from inve...... investigations of the electronic, and opto-electronic, properties of semiconductor nanostructures....

Analysis of dust and marine aerosol optical depth spectral-curvature information in the UV to SWIR (Short Wave Infrared) wavelength regions.

Science.gov (United States)

O'Neill, N. T.; Smirnov, A.; Eck, T. F.; Sakerin, S.; Kabanov, D.

2005-12-01

Traditional sunphotometry in the UV, visible and very NIR (Near Infrared) spectral regions is weighted, in terms of spectral information content, towards sub-micron (fine mode) particles. Sunphotometry in the NIR and SWIR increases the diversity and information content of spectral aerosol optical depth (AOD) measurements for supermicron (coarse mode) particles. Two data sets representing dust aerosols from the UAE (United Arab Emirates) region and marine aerosols from the northern, tropical and southern Atlantic Ocean were analyzed in terms of their spectral curvature diversity and information content. The former data set was acquired using NIR-enhanced CIMEL sunphotometers (340, 340, 380, 440, 500, 670, 870, 1020, 1640 nm) as part of the August to October, 2004 UAE2 field campaign while the latter data set was acquired using an automated Russian UV to SWIR SP-5 sunphotometer (339, 423, 438, 484, 552, 633, 677, 777, 869, 1241, 1560, 2148, 4000 nm) as part of a October/December 2004 cruise campaign in the northern, tropical and south Atlantic Ocean. A Microtops hand-held sunphotometer was also employed to acquire VIS to NIR AOD spectra during the latter field campaign. Results will be presented in terms of robust micro-physical and spectral curvature parameters which characterize super-micron aerosols and, in a more general sense, in terms of what universal/fundamental optical inferences can be drawn from the two disperse data sets.

Spectral tailoring of nanoscale EUV and soft x-ray multilayer optics

NARCIS (Netherlands)

Huang, Qiushi; Medvedev, Viacheslav; van de Kruijs, Robbert Wilhelmus Elisabeth; Yakshin, Andrey; Louis, Eric; Bijkerk, Frederik

2017-01-01

Extreme ultraviolet and soft X-ray (XUV) multilayer optics have experienced significant development over the past few years, particularly on controlling the spectral characteristics of light for advanced applications like EUV photolithography, space observation, and accelerator- or lab-based XUV

On the possibility of developing incoherent fibre-optic data transmission systems based on signal spectral coding with matched acousto-optical filters

International Nuclear Information System (INIS)

Proklov, Valerii V; Byshevski-Konopko, O A; Grigorievski, V I

2013-01-01

The scheme is suggested for developing the optical communication line based on the principle of code division of multiple access with matched acousto-optical filters and a 16-bit long Walsh sequence. Results of modelling show that such a line can operate if adjacent spectral lines are separated by at least double the Rayleigh criterion. (optical information transmission)

Spectral shaping for non-Gaussian source spectra in optical coherence tomography

NARCIS (Netherlands)

Tripathi, R; Nassif, N. A.; Nelson, JS; Park, B.H.; de Boer, JF

2002-01-01

We present a digital spectral shaping technique to reduce the sidelobes (ringing) of the axial point-spread function in optical coherence tomography for non-Gaussian-shaped source spectra. The spectra of two superluminescent diodes were combined to generate a spectrum with significant modulation.

Light Optics for Optical Stochastic Cooling

Energy Technology Data Exchange (ETDEWEB)

Andorf, Matthew [NICADD, DeKalb; Lebedev, Valeri [Fermilab; Piot, Philippe [NICADD, DeKalb; Ruan, Jinhao [Fermilab

2016-06-01

In Optical Stochastic Cooling (OSC) radiation generated by a particle in a "pickup" undulator is amplified and transported to a downstream "kicker" undulator where it interacts with the same particle which radiated it. Fermilab plans to carry out both passive (no optical amplifier) and active (optical amplifier) tests of OSC at the Integrable Optics Test Accelerator (IOTA) currently in construction*. The performace of the optical system is analyzed with simulations in Synchrotron Radiation Workshop (SRW) accounting for the specific temporal and spectral properties of undulator radiation and being augmented to include dispersion of lens material.

Posterior Lattice Degeneration Characterized by Spectral Domain Optical Tomography

OpenAIRE

Manjunath, Varsha; Taha, Mohammed; Fujimoto, James G.; Duker, Jay S.

2011-01-01

PURPOSE: To utilize high-resolution spectral domain optical coherence tomography (SD-OCT) in the characterization of retinal and vitreal morphological changes overlying posterior lattice degeneration. METHODS: A cross-sectional, retrospective analysis was performed on 13 eyes of 13 nonconsecutive subjects with posterior lattice degeneration seen at the New England Eye Center, Tufts Medical Center between October 2009 and January 2010. SD-OCT images taken through the region of latti...

Advanced spectral processing of broadband light using acousto-optic devices with arbitrary transmission functions.

Science.gov (United States)

Molchanov, Vladimir Ya; Yushkov, Konstantin B

2014-06-30

In the paper, we developed a dispersive method for transmission function synthesis of collinear and quasi-collinear acousto-optic tunable filters. General theoretical consideration was performed, and modelling was made for broadband and narrowband signals. Experimental results on spectral shaping of femtosecond laser emission were obtained. Binary spectral encoding of broadband emission was demonstrated.

Algebraic reconstruction techniques for spectral reconstruction in diffuse optical tomography

International Nuclear Information System (INIS)

Brendel, Bernhard; Ziegler, Ronny; Nielsen, Tim

2008-01-01

Reconstruction in diffuse optical tomography (DOT) necessitates solving the diffusion equation, which is nonlinear with respect to the parameters that have to be reconstructed. Currently applied solving methods are based on the linearization of the equation. For spectral three-dimensional reconstruction, the emerging equation system is too large for direct inversion, but the application of iterative methods is feasible. Computational effort and speed of convergence of these iterative methods are crucial since they determine the computation time of the reconstruction. In this paper, the iterative methods algebraic reconstruction technique (ART) and conjugated gradients (CGs) as well as a new modified ART method are investigated for spectral DOT reconstruction. The aim of the modified ART scheme is to speed up the convergence by considering the specific conditions of spectral reconstruction. As a result, it converges much faster to favorable results than conventional ART and CG methods

Optical decoherence and persistent spectral hole burning in Tm3+:LiNbO3

International Nuclear Information System (INIS)

Thiel, C.W.; Sun, Y.; Boettger, T.; Babbitt, W.R.; Cone, R.L.

2010-01-01

We report studies of decoherence and spectral hole burning for the 794 nm optical transition of thulium-doped lithium niobate. In addition to transient spectral holes due to the 3 H 4 and 3 F 4 excited states of Tm 3+ , persistent spectral holes with lifetimes of up to minutes were observed when a magnetic field of a few hundred Gauss was applied. The observed anti-hole structure identified the hole burning mechanism as population storage in the 169 Tm nuclear hyperfine levels. In addition, the magnetic field was effective in suppressing spectral diffusion, increasing the phase memory lifetime from 11 μs at zero field to 23 μs in a field of 320 Gauss applied along the crystal's c-axis. Coupling between Tm 3+ and the 7 Li and 93 Nb spins in the host lattice was also observed and a quadrupole shift of 22 kHz was measured for 7 Li at 1.7 K. A Stark shift of 18 kHz cm/V was measured for the optical transition with the electric field applied parallel to the c-axis.

Performance Analysis of Spectral-Phase-Encoded Optical CDMA System Using Two-Photon-Absorption Receiver Structure for Asynchronous and Slot-Level Synchronous Transmitters

Science.gov (United States)

Jamshidi, Kambiz; Salehi, Jawad A.

2007-06-01

In this paper, we analyze the performance of a nonlinear two-photon-absorption (TPA) receiver and compare its performance with that of a single-photon-absorption (SPA) receiver in the context of spectral-phase-encoded optical code-division multiple access (CDMA) technique. The performances for the above systems are evaluated for two different transmission scenarios, namely, asynchronous and slot-level synchronous transmitters. Performance evaluation includes different sources of degradation such as multiple-access interference, noise due to optical amplification, shot noise, and thermal noise. In obtaining the performance, the mean and variance of the received signal in each of the above techniques are derived, and bit error rate is obtained using Gaussian approximation. In general, it is shown that TPA receivers are superior in performance with respect to SPA receivers when the receiver employs a much slower photodetector in comparison with the laser's transmitted pulse duration. This, indeed, is the reason behind the choice of nonlinear receivers, such as TPA, in most spectral-phase-encoded optical CDMA systems.

Signal enhancement by spectral equalization of high frequency broadband signals transmitted through optical fibers

International Nuclear Information System (INIS)

Lyons, P.B.; Ogle, J.W.; Holzman, M.A.

1980-01-01

A new technique is discussed for enhancing the bandwidth and intensity of high frequency (> 1 GHz) analog, spectrally broad (40 nm) signals transmitted through one kilometer of optical fiber. The existing method for bandwidth enhancement of such a signal uses a very narrow (approx. 1 nm) filter between the fiber and detector to limit bandwidth degradation due to material dispersion. Using this method, most of the available optical intensity is rejected and lost. This new technique replaces the narrow-band filter with a spectral equalizer device which uses a reflection grating to disperse the input signal spectrum and direct it onto a linear array of fibers

Evaluation of methods to determine the spectral variations of aerosol optical thickness

Digital Repository Service at National Institute of Oceanography (India)

Suresh, T.; Talaulikar, M.; Rodrigues, A.; Desa, E.; Chauhan, P.

The methods used to derive spectral variations of aerosol optical thickness, AOT are evaluated. For our analysis we have used the AOT measured using a hand held sunphotometer at the coastal station on the west coast of India, Dona-Paula, Goa...

Photoreceptor layer map using spectral-domain optical coherence tomography.

Science.gov (United States)

Lee, Ji Eun; Lim, Dae Won; Bae, Han Yong; Park, Hyun Jin

2009-12-01

To develop a novel method for analysis of the photoreceptor layer map (PLM) generated using spectral-domain optical coherence tomography (OCT). OCT scans were obtained from 20 eyes, 10 with macular holes (MH) and 10 with central serous chorioretinopathy (CSC) using the Macular Cube (512 x 128) protocol of the Cirrus HD-OCT (Carl Zeiss). The scanned data were processed using embedded tools of the advanced visualization. A partial thickness OCT fundus image of the photoreceptor layer was generated by setting the region of interest to a 50-microm thick layer that was parallel and adjacent to the retinal pigment epithelium. The resulting image depicted the photoreceptor layer as a map of the reflectivity in OCT. The PLM was compared with fundus photography, auto-fluorescence, tomography, and retinal thickness map. The signal from the photoreceptor layer of every OCT scan in each case was demonstrated as a single image of PLM in a fundus photograph fashion. In PLM images, detachment of the sensory retina is depicted as a hypo-reflective area, which represents the base of MH and serous detachment in CSC. Relative hypo-reflectivity, which was also noted at closed MH and at recently reattached retina in CSC, was associated with reduced signal from the junction between the inner and outer segments of photoreceptors in OCT images. Using PLM, changes in the area of detachment and reflectivity of the photoreceptor layer could be efficiently monitored. The photoreceptor layer can be analyzed as a map using spectral-domain OCT. In the treatment of both MH and CSC, PLM may provide new pathological information about the photoreceptor layer to expand our understanding of these diseases.

Using spectral-domain optical coherence tomography to detect optic neuropathy in patients with craniosynostosis.

Science.gov (United States)

Dagi, Linda R; Tiedemann, Laura M; Heidary, Gena; Robson, Caroline D; Hall, Amber M; Zurakowski, David

2014-12-01

Detecting and monitoring optic neuropathy in patients with craniosynostosis is a clinical challenge due to limited cooperation, and subjective measures of visual function. The purpose of this study was to appraise the correlation of peripapillary retinal nerve fiber layer (RNFL) thickness measured by spectral-domain ocular coherence tomography (SD-OCT) with indication of optic neuropathy based on fundus examination. The medical records of all patients with craniosynostosis presenting for ophthalmic evaluation during 2013 were retrospectively reviewed. The following data were abstracted from the record: diagnosis, historical evidence of elevated intracranial pressure, current ophthalmic evaluation and visual field results, and current peripapillary RNFL thickness. A total of 54 patients were included (mean age, 10.6 years [range, 2.4-33.8 years]). Thirteen (24%) had evidence of optic neuropathy based on current fundus examination. Of these, 10 (77%) demonstrated either peripapillary RNFL elevation and papilledema or depression with optic atrophy. Sensitivity for detecting optic atrophy was 88%; for papilledema, 60%; and for either form of optic neuropathy, 77%. Specificity was 94%, 90%, and 83%, respectively. Kappa agreement was substantial for optic atrophy (κ = 0.73) and moderate for papilledema (κ = 0.39) and for either form of optic neuropathy (κ = 0.54). Logistic regression indicated that peripapillary RNFL thickness was predictive of optic neuropathy (P optic neuropathy than visual field testing (likelihood ratio = 10.02; P = 0.002). Sensitivity and specificity of logMAR visual acuity in detecting optic neuropathy were 15% and 95%, respectively. Peripapillary RNFL thickness measured by SD-OCT provides adjunctive evidence for identifying optic neuropathy in patients with craniosynostosis and appears more sensitive at detecting optic atrophy than papilledema. Copyright © 2014 American Association for Pediatric Ophthalmology and Strabismus. Published by

Wideband optical vector network analyzer based on optical single-sideband modulation and optical frequency comb.

Science.gov (United States)

Xue, Min; Pan, Shilong; He, Chao; Guo, Ronghui; Zhao, Yongjiu

2013-11-15

A novel approach to increase the measurement range of the optical vector network analyzer (OVNA) based on optical single-sideband (OSSB) modulation is proposed and experimentally demonstrated. In the proposed system, each comb line in an optical frequency comb (OFC) is selected by an optical filter and used as the optical carrier for the OSSB-based OVNA. The frequency responses of an optical device-under-test (ODUT) are thus measured channel by channel. Because the comb lines in the OFC have fixed frequency spacing, by fitting the responses measured in all channels together, the magnitude and phase responses of the ODUT can be accurately achieved in a large range. A proof-of-concept experiment is performed. A measurement range of 105 GHz and a resolution of 1 MHz is achieved when a five-comb-line OFC with a frequency spacing of 20 GHz is applied to measure the magnitude and phase responses of a fiber Bragg grating.

Optical decoherence and persistent spectral hole burning in Er{sup 3+}:LiNbO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Thiel, C.W., E-mail: thiel@physics.montana.ed [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Macfarlane, R.M. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); IBM Almaden Research Center, San Jose, CA 95120 (United States); Boettger, T. [Department of Physics, University of San Francisco, San Francisco, CA 94117 (United States); Sun, Y. [Department of Physics, University of South Dakota, Vermillion, SD 57069 (United States); Cone, R.L. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Babbitt, W.R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

2010-09-15

Developing new resonant optical materials for spatial-spectral holography and quantum information applications requires detailed knowledge of the decoherence and population relaxation dynamics for the quantum states involved in the optical transitions, motivating the need for fundamental material studies. We report recent progress in studying these properties in erbium-doped lithium niobate at liquid helium temperatures. The influence of temperature, applied magnetic fields, measurement timescale, and dopant concentration were probed using photon echo spectroscopy and time-resolved spectral hole burning on the 1532 nm transition of Er{sup 3+}:LiNbO{sub 3}. Effects of spectral diffusion due to interactions between Er{sup 3+} ions and between the Er{sup 3+} ion and {sup 7}Li and {sup 93}Nb nuclear spins in the host lattice were observed. In addition, long-lived persistent spectral storage of seconds to minutes was observed due to non-equilibrium population redistribution among superhyperfine states.

All-optical cryptography of M-QAM formats by using two-dimensional spectrally sliced keys.

Science.gov (United States)

Abbade, Marcelo L F; Cvijetic, Milorad; Messani, Carlos A; Alves, Cleiton J; Tenenbaum, Stefan

2015-05-10

There has been an increased interest in enhancing the security of optical communications systems and networks. All-optical cryptography methods have been considered as an alternative to electronic data encryption. In this paper we propose and verify the use of a novel all-optical scheme based on cryptographic keys applied on the spectral signal for encryption of the M-QAM modulated data with bit rates of up to 200 gigabits per second.

Transient spectral domain optical coherence tomography findings in classic MEWDS: a case report.

Science.gov (United States)

Lavigne, Luciana Castro; Isaac, David Leonardo Cruvinel; Duarte Júnior, José Osório; Avila, Marcos Pereira de

2014-01-01

The purpose of this study was to describe a patient with multiple evanescent white dot syndrome (MEWDS) who presented with classic retinal findings and transient changes in outer retinal anatomy. A 20-year-old man presented with mild blurred vision in the left eye, reporting flu-like symptoms 1 week before the visual symptoms started. Fundus examination of the left eye revealed foveal granularity and multiple scattered spots deep to the retina in the posterior pole. Fluorescein angiography and indocyanine green angiography showed typical MEWDS findings. Spectral Domain Optical Coherence Tomography has shown transient changes in outer retinal anatomy with disappearance of inner segment-outer segment junction and mild attenuation of external limiting membrane. Six months later, Spectral Domain Optical Coherence Tomography has shown complete resolution with recovery of normal outer retinal aspect.

Infrared imaging and spectral-domain optical coherence tomography findings correlate with microperimetry in acute macular neuroretinopathy: a case report

Directory of Open Access Journals (Sweden)

Grover Sandeep

2011-10-01

Full Text Available Abstract Introduction Spectral-domain optical coherence tomography findings in a patient with acute macular neuroretinopathy, and correlation with functional defects on microperimetry, are presented. Case presentation A 25-year old Caucasian woman presented with bitemporal field defects following an upper respiratory tract infection. Her visual acuity was 20/20 in both eyes and a dilated fundus examination revealed bilateral hyperpigmentary changes in the papillomacular bundle. Our patient underwent further evaluation with spectral-domain optical coherence tomography, infrared and fundus autofluorescence imaging. Functional changes were assessed by microperimetry. Infrared imaging showed the classic wedge-shaped defects and spectral-domain optical coherence tomography exhibited changes at the inner segment-outer segment junction, with a thickened outer plexiform layer overlying these areas. Fluorescein and indocyanine green angiography did not demonstrate any perfusion defects or any other abnormality. Microperimetry demonstrated focal elevation in threshold correlating with the wedge-shaped defects in both eyes. Conclusion Spectral-domain optical coherence tomography findings provide new evidence of the involvement of the outer plexiform layer of the retina in acute macular neuroretinopathy.

Fiber Bragg grating for spectral phase optical code-division multiple-access encoding and decoding

Science.gov (United States)

Fang, Xiaohui; Wang, Dong-Ning; Li, Shichen

2003-08-01

A new method for realizing spectral phase optical code-division multiple-access (OCDMA) coding based on step chirped fiber Bragg gratings (SCFBGs) is proposed and the corresponding encoder/decoder is presented. With this method, a mapping code is introduced for the m-sequence address code and the phase shift can be inserted into the subgratings of the SCFBG according to the mapping code. The transfer matrix method together with Fourier transform is used to investigate the characteristics of the encoder/decoder. The factors that influence the correlation property of the encoder/decoder, including index modulation and bandwidth of the subgrating, are identified. The system structure is simple and good correlation output can be obtained. The performance of the OCDMA system based on SCFBGs has been analyzed.

Experimental study of the use of multiband acousto-optic filters for spectral encoding / decoding the optical signals

International Nuclear Information System (INIS)

Proklov, V V; Byshevski-Konopko, O A; Filatov, A L; Lugovskoi, A V; Pisarevsky, Yu V

2016-01-01

A prototype of the acousto-optic (AO) decoder of optical signals is created on the base of the multiband AO filter. The joint work of the decoder with the developed previously AO coder has been verified experimentally. The main qualitative and quantitate characteristics of the spectral coding and decoding by Walsh sequences of the industrial LED radiation in the near infrared range are investigated. It is shown, that in the proposed data transmission system realization Signal-to-Interference Ratio (SIR) is not less than 13 dB. (paper)

Spectral triangulation molecular contrast optical coherence tomography with indocyanine green as the contrast agent

OpenAIRE

Yang, Changhuei; McGuckin, Laura E. L.; Simon, John D.; Choma, Michael A.; Applegate, Brian E.; Izatt, Joseph A.

2004-01-01

We report a new molecular contrast optical coherence tomography (MCOCT) implementation that profiles the contrast agent distribution in a sample by measuring the agent's spectral differential absorption. The method, spectra triangulation MCOCT, can effectively suppress contributions from spectrally dependent scatterings from the sample without a priori knowledge of the scattering properties. We demonstrate molecular imaging with this new MCOCT modality by mapping the distribution of indocyani...

A New Statistical Approach to the Optical Spectral Variability in Blazars

Directory of Open Access Journals (Sweden)

Jose A. Acosta-Pulido

2016-12-01

Full Text Available We present a spectral variability study of a sample of about 25 bright blazars, based on optical spectroscopy. Observations cover the period from the end of 2008 to mid 2015, with an approximately monthly cadence. Emission lines have been identified and measured in the spectra, which permits us to classify the sources into BL Lac-type or FSRQs, according to the commonly used EW limit. We have obtained synthetic photometry and produced colour-magnitude diagrams which show different trends associated with the object classes: generally, BL Lacs tend to become bluer when brighter and FSRQs become redder when brighter, although several objects exhibit both trends, depending on brightness. We have also applied a pattern recognition algorithm to obtain the minimum number of physical components which can explain the variability of the optical spectrum. We have used NMF (Non-Negative Matrix Factorization instead of PCA (Principal Component Analysis to avoid un-realistic negative components. For most targets we found that 2 or 3 meta-components are enough to explain the observed spectral variability.

Spectral-domain optical coherence tomography findings of the macula in 500 consecutive patients with uveitis.

Science.gov (United States)

Grajewski, R S; Boelke, A C; Adler, W; Meyer, S; Caramoy, A; Kirchhof, B; Cursiefen, C; Heindl, L M

2016-11-01

PurposeTo analyze the macular structure in a large series of consecutive patients with different types of uveitis using spectral-domain optical coherence tomography (SD-OCT).Patients and methodsFive hundred eyes of 500 consecutive patients with anterior, intermediate, posterior, and panuveitis underwent standardized macular examination using SD-OCT. Central retinal thickness (CRT), macular volume (MV), and presence of cystoid macular edema (CME), diffuse macular edema (DME), serous retinal detachment (SRD), epiretinal membrane with (ERM+) and without (ERM-) retinal surface wrinkling were determined.ResultsThe anatomic location of inflammation affected significantly CRT and MV (Pmacula is recommended for all uveitis patients. CRT, MV, and the incidence of CME were highest in intermediate and panuveitis.

PREVALENCE OF FOVEOLAR LUCENCY WITH DIFFERENT GAS TAMPONADES IN SURGICALLY CLOSED MACULAR HOLES ASSESSED BY SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

Science.gov (United States)

Zarranz-Ventura, Javier; Ellabban, Abdallah A; Sim, Dawn A; Keane, Pearse A; Kirkpatrick, James N; Sallam, Ahmed A B

2017-07-07

To evaluate the prevalence of foveolar lucency (FL) in surgically closed macular holes by spectral domain optical coherence tomography. One hundred forty-two eyes of 132 patients underwent pars plana vitrectomy, internal limiting membrane peeling, and gas tamponade in a 60-month time frame. Anatomical success and FL rates assessed by spectral domain optical coherence tomography, mean preoperative, and postoperative best-measured visual acuity and surgical details were retrospectively analyzed. Spectral domain optical coherence tomography confirmed closed holes with FL in 33.7% (34/101) of eyes at 1 month, 7.3% (9/123) at 3 months, 4.6% (6/129) at 6 months, and 3% (4/133) at 12 months. Prevalence of FL in closed holes at Month 1 was lower in C3F8-treated eyes (9.5%, 2/21) compared with C2F6 (40.9%, 18/44, P = 0.03) and SF6-treated eyes (38.9%, 14/36, P = 0.05). No differences were observed at Month 3. No differences in best-measured visual acuity change were observed between closed holes with or without FL at Month 1 (-0.14 ± 0.19 vs. -0.11 ± 0.23, P = 0.48) or any of the other time points. Temporary FL is a highly prevalent feature in successfully closed macular holes. Eyes treated with C3F8 gas had lower rates of FL at Month 1 than C2F6 and SF6-treated eyes. The presence of FL in closed holes does not seem to have any effect on the visual outcomes.

Quantification of retinal nerve fiber layer thickness using spectral domain optical coherence tomography in normal Indian population

Directory of Open Access Journals (Sweden)

Tarannum Mansoori

2012-01-01

Full Text Available The purpose of this study was to measure peripapillary retinal nerve fiber layer thickness (RNFLT using spectral domain optical coherence tomography (SD-OCT in normal Indian eyes, for which, 210 normal volunteers were recruited. One eye of each subject underwent RNFL scanning at 3.4 mm circle diameter around optic nerve using SD OCT. The data were analyzed to determine RNFLT in the sample population and its variation with age and gender. The average peripapillary RNFLT was 114.03 ± 9.59 μm. There was no effect of gender on RNFLT parameters. Age had significant negative correlation with average (P = 0.005, superior (P = 0.04, temporal (P = 0.049, and nasal quadrants (P = 0.01 RNFLT. Inferior quadrant RNFLT also had a negative correlation with age, but it was not statistically significant (P = 0.15.

Spectral phase shift and residual angular dispersion of an accousto-optic programme dispersive filter

International Nuclear Information System (INIS)

Boerzsoenyi, A.; Meroe, M.

2010-01-01

Complete text of publication follows. There is an increasing demand for active and precise dispersion control of ultrashort laser pulses. In chirped pulse amplification (CPA) laser systems, the dispersion of the optical elements of the laser has to be compensated at least to the fourth order to obtain high temporal contrast compressed pulses. Nowadays the most convenient device for active and programmable control of spectral phase and amplitude of broadband laser pulses is the acousto-optic programmable dispersive filter (AOPDF), claimed to be able to adjust the spectral phase up to the fourth order. Although it has been widely used, surprisingly enough there has been only a single, low resolution measurement reported on the accuracy of the induced spectral phase shift of the device. In our paper we report on the first systematic experiment aiming at the precise characterization of an AOPDF device. In the experiment the spectral phase shift of the AOPDF device was measured by spectrally and spatially resolved interferometry, which is especially powerful tool to determine small dispersion values with high accuracy. Besides the spectral phase dispersion, we measured both the propagation direction angular dispersion (PDAD) and the phase front angular dispersion (PhFAD). Although the two quantities are equal for plane waves, there may be noticeable difference for Gaussian pulses. PDAD was determined simply by focusing the beam on the slit of an imaging spectrograph, while PhFAD was measured by the use of an inverted Mach-Zehnder interferometer and an imaging spectrograph. In the measurements, the spectral phase shift and both types of angular dispersion have been recorded upon the systematic change of all the accessible functions of the acousto-optic programmable dispersive filter. The measured values of group delay dispersion (GDD) and third order dispersion (TOD) have been found to agree with the preset values within the error of the measurement (1 fs 2 and 10 fs 3

Potential of remote sensing of cirrus optical thickness by airborne spectral radiance measurements at different sideward viewing angles

OpenAIRE

Wolf, Kevin; Ehrlich, André; Hüneke, Tilman; Pfeilsticker, Klaus; Werner, Frank; Wirth, Martin; Wendisch, Manfred

2017-01-01

Spectral radiance measurements collected in nadir and sideward viewing directions by two airborne passive solar remote sensing instruments, the Spectral Modular Airborne Radiation measurement sysTem (SMART) and the Differential Optical Absorption Spectrometer (mini-DOAS), are used to compare the remote sensing results of cirrus optical thickness τ. The comparison is based on a sensitivity study using radiative transfer simulations (RTS) and on data obtained during three airb...

UTILIZATION OF FUNDUS AUTOFLUORESCENCE, SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY, AND ENHANCED DEPTH IMAGING IN THE CHARACTERIZATION OF BIETTI CRYSTALLINE DYSTROPHY IN DIFFERENT STAGES.

Science.gov (United States)

Li, Qian; Li, Yang; Zhang, Xiaohui; Xu, Zhangxing; Zhu, Xiaoqing; Ma, Kai; She, Haicheng; Peng, Xiaoyan

2015-10-01

To characterize Bietti crystalline dystrophy (BCD) in different stages using multiple imaging modalities. Sixteen participants clinically diagnosed as BCD were included in the retrospective study and were categorized into 3 stages according to fundus photography. Eleven patients were genetically confirmed. Fundus autofluorescence, spectral domain optical coherence tomography, and enhanced depth imaging features of BCD were analyzed. On fundus autofluorescence, the abnormal autofluorescence was shown to enlarge in area and decrease in intensity with stages. Using spectral domain optical coherence tomography, the abnormalities in Stage 1 were observed to localize in outer retinal layers, whereas in Stage 2 and Stage 3, more extensive retinal atrophy was seen. In enhanced depth imaging, the subfoveal choroidal layers were delineated clearly in Stage 1; in Stage 2, destructions were primarily found in the choriocapillaris with associated alterations in the outer vessels; Stage 3 BCD displayed severe choroidal thinning. Choroidal neovascularization and macular edema were exhibited with high incidence. IVS6-8del17bp/inGC of the CYP4V2 gene was the most common mutant allele. Noninvasive fundus autofluorescence, spectral domain optical coherence tomography, and enhanced depth imaging may help to characterize the chorioretinal pathology of BCD at different degrees, and therefore, we propose staging of BCD depending on those methods. Physicians should be cautious of the vision-threatening complications of the disease.

Power Spectral Density Specification and Analysis of Large Optical Surfaces

Science.gov (United States)

Sidick, Erkin

2009-01-01

The 2-dimensional Power Spectral Density (PSD) can be used to characterize the mid- and the high-spatial frequency components of the surface height errors of an optical surface. We found it necessary to have a complete, easy-to-use approach for specifying and evaluating the PSD characteristics of large optical surfaces, an approach that allows one to specify the surface quality of a large optical surface based on simulated results using a PSD function and to evaluate the measured surface profile data of the same optic in comparison with those predicted by the simulations during the specification-derivation process. This paper provides a complete mathematical description of PSD error, and proposes a new approach in which a 2-dimentional (2D) PSD is converted into a 1-dimentional (1D) one by azimuthally averaging the 2D-PSD. The 1D-PSD calculated this way has the same unit and the same profile as the original PSD function, thus allows one to compare the two with each other directly.

Spectral shaping of an all-fiber torsional acousto-optic tunable filter.

Science.gov (United States)

Ko, Jeakwon; Lee, Kwang Jo; Kim, Byoung Yoon

2014-12-20

Spectral shaping of an all-fiber torsional acousto-optic (AO) tunable filter is studied. The technique is based on the axial modulation of AO coupling strength along a highly birefringent optical fiber, which is achieved by tailoring the outer diameter of the fiber along its propagation axis. Two kinds of filter spectral shaping schemes-Gaussian apodization and matched filtering with triple resonance peaks-are proposed and numerically investigated under realistic experimental conditions: at the 50-cm-long AO interaction length of the fiber and at half of the original fiber diameter as the minimum thickness of the tailored fiber section. The results show that the highest peak of sidelobe spectra in filter transmission is suppressed from 11.64% to 0.54% via Gaussian modulation of the AO coupling coefficient (κ). Matched filtering with triple resonance peaks operating with a single radio frequency signal is also achieved by cosine modulation of κ, of which the modulation period determines the spectral distance between two satellite peaks located in both wings of the main resonance peak. The splitting of two satellite peaks in the filter spectra reaches 48.2 nm while the modulation period varies from 7.7 to 50 cm. The overall peak power of two satellite resonances is calculated to be 22% of the main resonance power. The results confirm the validity and practicality of our approach, and we predict robust and stable operation of the designed all-fiber torsional AO filters.

Conjugation of fiber-coupled wide-band light sources and acousto-optical spectral elements

Science.gov (United States)

Machikhin, Alexander; Batshev, Vladislav; Polschikova, Olga; Khokhlov, Demid; Pozhar, Vitold; Gorevoy, Alexey

2017-12-01

Endoscopic instrumentation is widely used for diagnostics and surgery. The imaging systems, which provide the hyperspectral information of the tissues accessible by endoscopes, are particularly interesting and promising for in vivo photoluminescence diagnostics and therapy of tumour and inflammatory diseases. To add the spectral imaging feature to standard video endoscopes, we propose to implement acousto-optical (AO) filtration of wide-band illumination of incandescent-lamp-based light sources. To collect maximum light and direct it to the fiber-optic light guide inside the endoscopic probe, we have developed and tested the optical system for coupling the light source, the acousto-optical tunable filter (AOTF) and the light guide. The system is compact and compatible with the standard endoscopic components.

Analyzing Water's Optical Absorption

Science.gov (United States)

2002-01-01

A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

Universal dispersion model for characterization of optical thin films over wide spectral range: Application to magnesium fluoride

Science.gov (United States)

Franta, Daniel; Nečas, David; Giglia, Angelo; Franta, Pavel; Ohlídal, Ivan

2017-11-01

Optical characterization of magnesium fluoride thin films is performed in a wide spectral range from far infrared to extreme ultraviolet (0.01-45 eV) utilizing the universal dispersion model. Two film defects, i.e. random roughness of the upper boundaries and defect transition layer at lower boundary are taken into account. An extension of universal dispersion model consisting in expressing the excitonic contributions as linear combinations of Gaussian and truncated Lorentzian terms is introduced. The spectral dependencies of the optical constants are presented in a graphical form and by the complete set of dispersion parameters that allows generating tabulated optical constants with required range and step using a simple utility in the newAD2 software package.

Spectrally selective molecular doped solids: spectroscopy, photophysics and their application to ultrafast optical pulse processing

International Nuclear Information System (INIS)

Galaup, Jean-Pierre

2005-01-01

The persistent spectral hole-burning (PSHB) phenomenon observed in molecular doped polymers cooled down to liquid helium temperatures allows the engraving of spectral structures in the inhomogeneous absorption profile of the material. This phenomenon known since 1974 has became a fruitful field for the study of the intimacy of complex molecular systems in the solid state, revealing high-resolution spectroscopy, photophysics, photochemistry and dynamics of molecular doped amorphous media, organic as well as inorganic. A PSHB molecular doped solid can be programmed in spectral domain and therefore, it can be converted in an optical processor capable to achieve user-defined optical functions. Some aspects of this field are illustrated in the present paper. An application is presented where a naphthalocyanine doped polymer film is used in a demonstrative experiment to prove that temporal aberration free re-compression of ultra-short light pulses is feasible. Perspectives for the coherent control of light fields or photochemical processes are also evoked

Prediction of meat spectral patterns based on optical properties and concentrations of the major constituents.

Science.gov (United States)

ElMasry, Gamal; Nakauchi, Shigeki

2016-03-01

A simulation method for approximating spectral signatures of minced meat samples was developed depending on concentrations and optical properties of the major chemical constituents. Minced beef samples of different compositions scanned on a near-infrared spectroscopy and on a hyperspectral imaging system were examined. Chemical composition determined heuristically and optical properties collected from authenticated references were simulated to approximate samples' spectral signatures. In short-wave infrared range, the resulting spectrum equals the sum of the absorption of three individual absorbers, that is, water, protein, and fat. By assuming homogeneous distributions of the main chromophores in the mince samples, the obtained absorption spectra are found to be a linear combination of the absorption spectra of the major chromophores present in the sample. Results revealed that developed models were good enough to derive spectral signatures of minced meat samples with a reasonable level of robustness of a high agreement index value more than 0.90 and ratio of performance to deviation more than 1.4.

Online monitoring of printed electronics by Spectral-Domain Optical Coherence Tomography

KAUST Repository

Alarousu, Erkki

2013-03-28

Spectral-Domain Optical Coherence Tomography (SD-OCT) is an optical method capable of 3D imaging of object\\'s internal structure with micron-scale resolution. Modern SD-OCT tools offer the speed capable of online monitoring of printed devices. This paper demonstrates the use of SD-OCT in a simulated roll-to-roll (R2R) process through monitoring some structural properties of moving screen printed interdigitated electrodes. It is shown that structural properties can be resolved for speeds up to ca. 1m/min, which is the first step towards application of this method in real manufacturing processes, including roll-to-roll (R2R) printing.

Spectral domain optical coherence tomography characteristics in diabetic retinopathy

Directory of Open Access Journals (Sweden)

Laxmi Gella

2014-01-01

Full Text Available Purpose: To report the appearance of diabetic retinopathy lesions using spectral domain optical coherence tomography (SD-OCT. Materials and Methods: A total of 287 eyes of 199 subjects were included. All the subjects underwent complete ophthalmic examination including SD-OCT. Results: The appearance of various lesions of diabetic retinopathy and the retinal layers involved were reported. In subjects with macular edema the prevalence of incomplete PVD was 55.6%. Conclusion: SD-OCT brings new insights into the morphological changes of the retina in diabetic retinopathy.

Multi-spectral optical absorption in substrate-free nanowire arrays

Energy Technology Data Exchange (ETDEWEB)

Zhang, Junpeng; Chia, Andrew; Boulanger, Jonathan; LaPierre, Ray, E-mail: lapierr@mcmaster.ca [Department of Engineering Physics, McMaster University, 1280 Main St. West, Hamilton, Ontario L8S 4L7 (Canada); Dhindsa, Navneet; Khodadad, Iman; Saini, Simarjeet [Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave West, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute of Nanotechnology, University of Waterloo, 200 University Ave West, Waterloo, Ontario N2L 3G1 (Canada)

2014-09-22

A method is presented of fabricating gallium arsenide (GaAs) nanowire arrays of controlled diameter and period by reactive ion etching of a GaAs substrate containing an indium gallium arsenide (InGaP) etch stop layer, allowing the precise nanowire length to be controlled. The substrate is subsequently removed by selective etching, using the same InGaP etch stop layer, to create a substrate-free GaAs nanowire array. The optical absorptance of the nanowire array was then directly measured without absorption from a substrate. We directly observe absorptance spectra that can be tuned by the nanowire diameter, as explained with rigorous coupled wave analysis. These results illustrate strong optical absorption suitable for nanowire-based solar cells and multi-spectral absorption for wavelength discriminating photodetectors. The solar-weighted absorptance above the bandgap of GaAs was 94% for a nanowire surface coverage of only 15%.

Enhanced optical transmission through a star-shaped bull's eye at dual resonant-bands in UV and the visible spectral range.

Science.gov (United States)

Nazari, Tavakol; Khazaeinezhad, Reza; Jung, Woohyun; Joo, Boram; Kong, Byung-Joo; Oh, Kyunghwan

2015-07-13

Dual resonant bands in UV and the visible range were simultaneously observed in the enhanced optical transmission (EOT) through star-shaped plasmonic structures. EOTs through four types of polygonal bull's eyes with a star aperture surrounded by the concentric star grooves were analyzed and compared for 3, 4, 5, and 6 corners, using finite difference time domain (FDTD) method. In contrast to plasmonic resonances in the visible range, the UV-band resonance intensity was found to scale with the number of corners, which is related with higher order multipole interactions. Spectral positions and relative intensities of the dual resonances were analyzed parametrically to find optimal conditions to maximize EOT in UV-visible dual bands.

Terahertz Josephson spectral analysis and its applications

Science.gov (United States)

Snezhko, A. V.; Gundareva, I. I.; Lyatti, M. V.; Volkov, O. Y.; Pavlovskiy, V. V.; Poppe, U.; Divin, Y. Y.

2017-04-01

Principles of Hilbert-transform spectral analysis (HTSA) are presented and advantages of the technique in the terahertz (THz) frequency range are discussed. THz HTSA requires Josephson junctions with high values of characteristic voltages I c R n and dynamics described by a simple resistively shunted junction (RSJ) model. To meet these requirements, [001]- and [100]-tilt YBa2Cu3O7-x bicrystal junctions with deviations from the RSJ model less than 1% have been developed. Demonstrators of Hilbert-transform spectrum analyzers with various cryogenic environments, including integration into Stirling coolers, are described. Spectrum analyzers have been characterized in the spectral range from 50 GHz to 3 THz. Inside a power dynamic range of five orders, an instrumental function of the analyzers has been found to have a Lorentz form around a single frequency of 1.48 THz with a spectral resolution as low as 0.9 GHz. Spectra of THz radiation from optically pumped gas lasers and semiconductor frequency multipliers have been studied with these spectrum analyzers and the regimes of these radiation sources were optimized for a single-frequency operation. Future applications of HTSA will be related with quick and precise spectral characterization of new radiation sources and identification of substances in the THz frequency range.

[Research on symmetrical optical waveguide based surface plasmon resonance sensing with spectral interrogation].

Science.gov (United States)

Zhang, Yi-long; Liu, Le; Guo, Jun; Zhang, Peng-fei; Guo, Ji-hua; Ma, Hui; He, Yong-hong

2015-02-01

Surface plasmon resonance (SPR) sensors with spectral interrogation can adopt fiber to transmit light signals, thus leaving the sensing part separated, which is very convenient for miniaturization, remote-sensing and on-site analysis. Symmetrical optical waveguide (SOW) SPR has the same refractive index of the-two buffer media layers adjacent to the metal film, resulting in longer propagation distance, deeper penetration depth and better performance compared to conventional SPR In the present paper, we developed a symmetrical optical, waveguide (SOW) SPR sensor with wavelength interrogation. In the system, MgF2-Au-MgF2 film was used as SOW module for glucose sensing, and a fiber based light source and detection was used in the spectral interrogation. In the experiment, a refractive index resolution of 2.8 x 10(-7) RIU in fluid protocol was acquired. This technique provides advantages of high resolution and could have potential use in compact design, on-site analysis and remote sensing.

A joint estimation detection of Glaucoma progression in 3D spectral domain optical coherence tomography optic nerve head images

Science.gov (United States)

Belghith, Akram; Bowd, Christopher; Weinreb, Robert N.; Zangwill, Linda M.

2014-03-01

Glaucoma is an ocular disease characterized by distinctive changes in the optic nerve head (ONH) and visual field. Glaucoma can strike without symptoms and causes blindness if it remains without treatment. Therefore, early disease detection is important so that treatment can be initiated and blindness prevented. In this context, important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, an essential element for glaucoma detection and monitoring. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new framework for detection of glaucoma progression using 3D SD-OCT images. In contrast to previous works that the retinal nerve fiber layer (RNFL) thickness measurement provided by commercially available spectral-domain optical coherence tomograph, we consider the whole 3D volume for change detection. To integrate a priori knowledge and in particular the spatial voxel dependency in the change detection map, we propose the use of the Markov Random Field to handle a such dependency. To accommodate the presence of false positive detection, the estimated change detection map is then used to classify a 3D SDOCT image into the "non-progressing" and "progressing" glaucoma classes, based on a fuzzy logic classifier. We compared the diagnostic performance of the proposed framework to existing methods of progression detection.

Spectral dependence of third-order nonlinear optical properties in InN

International Nuclear Information System (INIS)

Ahn, H.; Lee, M.-T.; Chang, Y.-M.

2014-01-01

We report on the nonlinear optical properties of InN measured in a wide near-infrared spectral range with the femtosecond Z-scan technique. The above-bandgap nonlinear absorption in InN is found to originate from the saturation of absorption by the band-state-filling and its cross-section increases drastically near the bandgap energy. With below-bandgap excitation, the nonlinear absorption undergoes a transition from saturation absorption (SA) to reverse-SA (RSA), attributed to the competition between SA of band-tail states and two-photon-related RSA. The measured large nonlinear refractive index of the order of 10 −10 cm 2 /W indicates InN as a potential material for all-optical switching and related applications

Measurements of spectral responses for developing fiber-optic pH sensor

Science.gov (United States)

Yoo, Wook Jae; Heo, Ji Yeon; Jang, Kyoung Won; Seo, Jeong Ki; Moon, Jin Soo; Park, Jang-Yeon; Park, Byung Gi; Cho, Seunghyun; Lee, Bongsoo

2011-01-01

In this study, we have fabricated a fiber-optic pH sensor, which is composed of a light source, a pH-sensing probe, plastic optical fibers and a spectrometer, for determining the degree of infection by Helicobacter pylori in the stomach. As pH indicators, phenol red and m-cresol purple are used, and pH liquid solutions are prepared by mixing phenol red or m-cresol purple solutions and various kinds of pH buffer solutions. The light emitted by a light source is guided by plastic optical fibers to the pH liquid solution, and the optical characteristic of a reflected light is changed according to the color variations of the pH indicator in the pH-sensing probe. Therefore, we have measured the intensities and wavelength shifts of the reflected lights, which change according to the color variations of indicators at different pH values, by using a spectrometer for spectral analysis. Also, the relationships between the pH values of liquid solutions and the optical properties of the modulated lights are obtained on the basis of the changes of the colors of indicators.

Spectral characterization in deep UV of an improved imaging KDP acousto-optic tunable filter

International Nuclear Information System (INIS)

Gupta, Neelam; Voloshinov, Vitaly

2014-01-01

Recently, we developed a number of high quality noncollinear acousto-optic tunable filter (AOTF) cells in different birefringent materials with UV imaging capability. Cells based on a single crystal of KDP (potassium dihydrophosphate) had the best transmission efficiency and the optical throughput needed to acquire high quality spectral images at wavelengths above 220 nm. One of the main limitations of these imaging filters was their small angular aperture in air, limited to about 1.0°. In this paper, we describe an improved imaging KDP AOTF operating from the deep UV to the visible region of the spectrum. The linear and angular apertures of the new filter are 10 × 10 mm 2 and 1.8°, respectively. The spectral tuning range is 205–430 nm with a 60 cm −1 spectral resolution. We describe the filter and present experimental results on imaging using both a broadband source and a number of light emitting diodes (LEDs) in the UV, and include the measured spectra of these LEDs obtained with a collinear SiO 2 filter-based spectrometer operating above 255 nm. (paper)

Removal of Optically Thick Clouds from Multi-Spectral Satellite Images Using Multi-Frequency SAR Data

Directory of Open Access Journals (Sweden)

Robert Eckardt

2013-06-01

Full Text Available This study presents a method for the reconstruction of pixels contaminated by optical thick clouds in multi-spectral Landsat images using multi-frequency SAR data. A number of reconstruction techniques have already been proposed in the scientific literature. However, all of the existing techniques have certain limitations. In order to overcome these limitations, we expose the Closest Spectral Fit (CSF method proposed by Meng et al. to a new, synergistic approach using optical and SAR data. Therefore, the term Closest Feature Vector (CFV is introduced. The technique facilitates an elegant way to avoid radiometric distortions in the course of image reconstruction. Furthermore the cloud cover removal is independent from underlying land cover types and assumptions on seasonality, etc. The methodology is applied to mono-temporal, multi-frequency SAR data from TerraSAR-X (X-Band, ERS (C-Band and ALOS Palsar (L-Band. This represents a way of thinking about Radar data not as foreign, but as additional data source in multi-spectral remote sensing. For the assessment of the image restoration performance, an experimental framework is established and a statistical evaluation protocol is designed. The results show the potential of a synergistic usage of multi-spectral and SAR data to overcome the loss of data due to cloud cover.

Spectral solar irradiance and some optical properties for various polluted atmospheres

International Nuclear Information System (INIS)

Jacovides, Constantinos P.; Asimakopoulos, Demosthenis N.; Steven, Michael D.

2000-01-01

Using ground-based spectroradiometric measurements taken over the Athens atmosphere during May 1995, the influence of gaseous pollutants and aerosol on the spectral radiant energy distribution was investigated. It was found that spectral measurements exhibited variations based on various polluted urban atmospheric conditions as determined via gaseous pollutants record analysis. The relative attenuations cause by gaseous pollutants and aerosol can exceed 27%, 17% and 16% in the global ultraviolet, visible and near-infrared portions of the solar spectrum respectively, as compared to 'background' values. In contrast, an enhancement of the near-infrared diffuse component by 66%, was observed, while in visible and ultraviolet bands the relative increases reached 54% and 21% respectively. Experimental total Rayleigh-corrected and spectral aerosol optical depths were retrieved, representing differences in polluted air over the Athens atmosphere. The diffuse component accounts for more than 80% of the total radiation field under high polluted atmosphere. The observed differences of solar radiation between the Athens center and at a nearby suburban site are a manifestation of contrasting air properties provided mainly by automotive traffic. (Author)

DSP-enabled reconfigurable and transparent spectral converters for converging optical and mobile fronthaul/backhaul networks.

Science.gov (United States)

Mao, M Z; Giddings, R P; Cao, B Y; Xu, Y T; Wang, M; Tang, J M

2017-06-12

Dynamically reconfigurable and transparent signal spectral conversion is expected to play a vital role in seamlessly integrating traditional metropolitan optical networks and mobile fronthaul/backhaul networks. In this paper, a simple digital signal processing (DSP)-enabled spectral converter is proposed and extensively investigated, for the first time, which just utilizes a single standard dual-parallel Mach-Zehnder modulator (DP-MZM) driven by SDN-controllable RF signals and DC bias currents. As an important thrust of the paper, optimum operating conditions of the proposed converter are analytically identified, statistically examined and experimentally verified. Optimum operating condition-supported spectral converter performances in IMDD-based network nodes are explored both theoretically and experimentally in terms of frequency detuning range-dependent conversion efficiency, spectral conversion-induced OSNR/power penalty and transparency to input signal characteristics. The proposed spectral converter has unique advantages including low configuration complexity, strict transparency, SDN-controllable performance reconfigurability and flexibility, as well as negligible spectral conversion-induced latency.

OPTICAL POLARIZATION AND SPECTRAL VARIABILITY IN THE M87 JET

International Nuclear Information System (INIS)

Perlman, Eric S.; Cara, Mihai; Bourque, Matthew; Simons, Raymond C.; Adams, Steven C.; Harris, D. E.; Madrid, Juan P.; Clausen-Brown, Eric; Cheung, C. C.; Stawarz, Lukasz; Georganopoulos, Markos; Sparks, William B.; Biretta, John A.

2011-01-01

During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability has also been seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST-1 shows a highly significant correlation between flux and polarization, with P increasing from ∼20% at minimum to >40% at maximum, while the orientation of its electric vector stayed constant. HST-1's optical-UV spectrum is very hard (α UV-O ∼ 0.5, F ν ∝ν –α ), and displays 'hard lags' during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2σ upper limits of 0.5δ pc and 1.02c on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet position angle (P.A.) makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and 'looping' in the (I, P) plane. The nucleus has a much steeper spectrum (α UV-O ∼ 1.5) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.

OPTICAL POLARIZATION AND SPECTRAL VARIABILITY IN THE M87 JET

Energy Technology Data Exchange (ETDEWEB)

Perlman, Eric S.; Cara, Mihai; Bourque, Matthew; Simons, Raymond C. [Department of Physics and Space Sciences, 150 W. University Blvd., Florida Institute of Technology, Melbourne, FL 32901 (United States); Adams, Steven C. [Department of Physics and Astronomy, University of Georgia, Athens, GA 30605 (United States); Harris, D. E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Madrid, Juan P. [Center for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122 (Australia); Clausen-Brown, Eric [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Cheung, C. C. [National Academy of Sciences, Washington, DC 20001 (United States); Stawarz, Lukasz [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Georganopoulos, Markos [Department of Physics, University of Maryland-Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States); Sparks, William B.; Biretta, John A., E-mail: eperlman@fit.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2011-12-20

During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability has also been seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST-1 shows a highly significant correlation between flux and polarization, with P increasing from {approx}20% at minimum to >40% at maximum, while the orientation of its electric vector stayed constant. HST-1's optical-UV spectrum is very hard ({alpha}{sub UV-O} {approx} 0.5, F{sub {nu}}{proportional_to}{nu}{sup -{alpha}}), and displays 'hard lags' during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2{sigma} upper limits of 0.5{delta} pc and 1.02c on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet position angle (P.A.) makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and 'looping' in the (I, P) plane. The nucleus has a much steeper spectrum ({alpha}{sub UV-O} {approx} 1.5) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.

Ultra-wideband spectral analysis using S2 technology

International Nuclear Information System (INIS)

Krishna Mohan, R.; Chang, T.; Tian, M.; Bekker, S.; Olson, A.; Ostrander, C.; Khallaayoun, A.; Dollinger, C.; Babbitt, W.R.; Cole, Z.; Reibel, R.R.; Merkel, K.D.; Sun, Y.; Cone, R.; Schlottau, F.; Wagner, K.H.

2007-01-01

This paper outlines the efforts to develop an ultra-wideband spectrum analyzer that takes advantage of the broad spectral response and fine spectral resolution (∼25 kHz) of spatial-spectral (S2) materials. The S2 material can process the full spectrum of broadband microwave transmissions, with adjustable time apertures (down to 100 μs) and fast update rates (up to 1 kHz). A cryogenically cooled Tm:YAG crystal that operates on microwave signals modulated onto a stabilized optical carrier at 793 nm is used as the core for the spectrum analyzer. Efforts to develop novel component technologies that enhance the performance of the system and meet the application requirements are discussed, including an end-to-end device model for parameter optimization. We discuss the characterization of new ultra-wide bandwidth S2 materials. Detection and post-processing module development including the implementation of a novel spectral recovery algorithm using field programmable gate array technology (FPGA) is also discussed

Ultra-wideband spectral analysis using S2 technology

Energy Technology Data Exchange (ETDEWEB)

Krishna Mohan, R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States)]. E-mail: krishna@spectrum.montana.edu; Chang, T. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Tian, M. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Bekker, S. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Olson, A. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Ostrander, C. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Khallaayoun, A. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Dollinger, C. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Babbitt, W.R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Cole, Z. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); S2 Corporation, Bozeman, MT 59718 (United States); Reibel, R.R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); S2 Corporation, Bozeman, MT 59718 (United States); Merkel, K.D. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); S2 Corporation, Bozeman, MT 59718 (United States); Sun, Y. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Cone, R. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Schlottau, F. [University of Colorado, Boulder, CO 80309 (United States); Wagner, K.H. [University of Colorado, Boulder, CO 80309 (United States)

2007-11-15

This paper outlines the efforts to develop an ultra-wideband spectrum analyzer that takes advantage of the broad spectral response and fine spectral resolution ({approx}25 kHz) of spatial-spectral (S2) materials. The S2 material can process the full spectrum of broadband microwave transmissions, with adjustable time apertures (down to 100 {mu}s) and fast update rates (up to 1 kHz). A cryogenically cooled Tm:YAG crystal that operates on microwave signals modulated onto a stabilized optical carrier at 793 nm is used as the core for the spectrum analyzer. Efforts to develop novel component technologies that enhance the performance of the system and meet the application requirements are discussed, including an end-to-end device model for parameter optimization. We discuss the characterization of new ultra-wide bandwidth S2 materials. Detection and post-processing module development including the implementation of a novel spectral recovery algorithm using field programmable gate array technology (FPGA) is also discussed.

Optical decoherence and persistent spectral hole burning in Tm{sup 3+}:LiNbO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Thiel, C.W., E-mail: thiel@physics.montana.ed [Department of Physics, Montana State University, EPS 264, Bozeman, MT 59717 (United States); Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Sun, Y. [Department of Physics, University of South Dakota, Vermillion, SD 57069 (United States); Boettger, T. [Department of Physics, University of San Francisco, San Francisco, CA 94117 (United States); Babbitt, W.R. [Department of Physics, Montana State University, EPS 264, Bozeman, MT 59717 (United States); Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Cone, R.L. [Department of Physics, Montana State University, EPS 264, Bozeman, MT 59717 (United States)

2010-09-15

We report studies of decoherence and spectral hole burning for the 794 nm optical transition of thulium-doped lithium niobate. In addition to transient spectral holes due to the {sup 3}H{sub 4} and {sup 3}F{sub 4} excited states of Tm{sup 3+}, persistent spectral holes with lifetimes of up to minutes were observed when a magnetic field of a few hundred Gauss was applied. The observed anti-hole structure identified the hole burning mechanism as population storage in the {sup 169}Tm nuclear hyperfine levels. In addition, the magnetic field was effective in suppressing spectral diffusion, increasing the phase memory lifetime from 11 {mu}s at zero field to 23 {mu}s in a field of 320 Gauss applied along the crystal's c-axis. Coupling between Tm{sup 3+} and the {sup 7}Li and {sup 93}Nb spins in the host lattice was also observed and a quadrupole shift of 22 kHz was measured for {sup 7}Li at 1.7 K. A Stark shift of 18 kHz cm/V was measured for the optical transition with the electric field applied parallel to the c-axis.

Analysis of In-Situ Spectral Reflectance of Sago and Other Palms: Implications for Their Detection in Optical Satellite Images

Science.gov (United States)

Rendon Santillan, Jojene; Makinano-Santillan, Meriam

2018-04-01

We present a characterization, comparison and analysis of in-situ spectral reflectance of Sago and other palms (coconut, oil palm and nipa) to ascertain on which part of the electromagnetic spectrum these palms are distinguishable from each other. The analysis also aims to reveal information that will assist in selecting which band to use when mapping Sago palms using the images acquired by these sensors. The datasets used in the analysis consisted of averaged spectral reflectance curves of each palm species measured within the 345-1045 nm wavelength range using an Ocean Optics USB4000-VIS-NIR Miniature Fiber Optic Spectrometer. This in-situ reflectance data was also resampled to match the spectral response of the 4 bands of ALOS AVNIR-2, 3 bands of ASTER VNIR, 4 bands of Landsat 7 ETM+, 5 bands of Landsat 8, and 8 bands of Worldview-2 (WV2). Examination of the spectral reflectance curves showed that the near infra-red region, specifically at 770, 800 and 875 nm, provides the best wavelengths where Sago palms can be distinguished from other palms. The resampling of the in-situ reflectance spectra to match the spectral response of optical sensors made possible the analysis of the differences in reflectance values of Sago and other palms in different bands of the sensors. Overall, the knowledge learned from the analysis can be useful in the actual analysis of optical satellite images, specifically in determining which band to include or to exclude, or whether to use all bands of a sensor in discriminating and mapping Sago palms.

Growth, spectral, linear and nonlinear optical characteristics of an efficient semiorganic acentric crystal: L-valinium L-valine chloride

Energy Technology Data Exchange (ETDEWEB)

Nageshwari, M.; Jayaprakash, P.; Kumari, C. Rathika Thaya [PG & Research Department of Physics, Arignar Anna Govt. Arts College, Cheyyar 604407, Tamil Nadu (India); Vinitha, G. [Department of Physics, School of Advanced Sciences, VIT Chennai, 600127 Tamil Nadu (India); Caroline, M. Lydia, E-mail: lydiacaroline2006@yahoo.co.in [PG & Research Department of Physics, Arignar Anna Govt. Arts College, Cheyyar 604407, Tamil Nadu (India)

2017-04-15

An efficient nonlinear optical semiorganic material L-valinium L-valine chloride (LVVCl) was synthesized and grown-up by means of slow evaporation process. Single crystal XRD evince that LVVCl corresponds to monoclinic system having acentric space group P2{sub 1}. The diverse functional groups existing in LVVCl were discovered with FTIR spectral investigation. The UV-Visible and photoluminescence spectrum discloses the optical and electronic properties respectively for the grown crystal. Several optical properties specifically extinction coefficient, reflectance, linear refractive index, electrical and optical conductivity were also determined. The SEM analysis was also carried out and it portrayed the surface morphology of LVVCl. The calculated value of laser damage threshold was 2.59 GW/cm{sup 2}. The mechanical and dielectric property of LVVCl was investigated employing microhardness and dielectric studies. The second and third order nonlinear optical characteristics of LVVCl was characterized utilizing Kurtz Perry and Z scan technique respectively clearly suggest its suitability in the domain of optics and photonics. - Graphical abstract: Good quality transparent single crystals of L-valinium L-valine chloride single crystal was grown by slow evaporation technique. The grown crystals were analyzed using different instrumentation methods to check its usefulness for the device fabrication. The determination of nonlinear refractive index (n{sub 2}), absorption coefficient (β) and third order nonlinear susceptibility was determined by Z scan technique, highlighted that LVVCl can serve as a promising candidate for opto electronic and nonlinear optical applications.

Enhancement of nonlinear optical response of weakly confined excitons in GaAs thin films by spectrally rectangle-shape-pulse-excitation

International Nuclear Information System (INIS)

Kojima, O; Isu, T; Ishi-Hayase, J; Sasaki, M; Tsuchiya, M

2007-01-01

We report the enhancement of the nonlinear optical response of the weakly confined excitons with use of spectrally rectangular pulse. The nonlinear optical response was investigated as a function of excitation energy by a degenerate four-wave-mixing (DFWM) technique. In the case that the laser pulse with the controlled spectral shape excites the plural exciton states simultaneously, the DFWM signal intensity is enhanced by a factor of two in comparison with the intensity under the excitation of a single exciton state. This enhancement is caused by the superposition of the nonlinear optical responses from the plural exciton states

InP monolithically integrated label swapper device for spectral amplitude coded optical packet networks

NARCIS (Netherlands)

Muñoz, P.; García-Olcina, R.; Doménech, J.D.; Rius, M.; Sancho, J.C.; Capmany, J.; Chen, L.R.; Habib, C.; Leijtens, X.J.M.; Vries, de T.; Heck, M.J.R.; Augustin, L.M.; Nötzel, R.; Robbins, D.J.

2010-01-01

In this paper a label swapping device, for spectral amplitude coded optical packet networks, fully integrated using InP technology is presented. Compared to previous demonstrations using discrete component assembly, the device footprint is reduced by a factor of 105 and the operation speed is

Parametric spectro-temporal analyzer (PASTA) for real-time optical spectrum observation

Science.gov (United States)

Zhang, Chi; Xu, Jianbing; Chui, P. C.; Wong, Kenneth K. Y.

2013-06-01

Real-time optical spectrum analysis is an essential tool in observing ultrafast phenomena, such as the dynamic monitoring of spectrum evolution. However, conventional method such as optical spectrum analyzers disperse the spectrum in space and allocate it in time sequence by mechanical rotation of a grating, so are incapable of operating at high speed. A more recent method all-optically stretches the spectrum in time domain, but is limited by the allowable input condition. In view of these constraints, here we present a real-time spectrum analyzer called parametric spectro-temporal analyzer (PASTA), which is based on the time-lens focusing mechanism. It achieves a frame rate as high as 100 MHz and accommodates various input conditions. As a proof of concept and also for the first time, we verify its applications in observing the dynamic spectrum of a Fourier domain mode-locked laser, and the spectrum evolution of a laser cavity during its stabilizing process.

Optical signal processing for enabling high-speed, highly spectrally efficient and high capacity optical systems

Science.gov (United States)

Fazal, Muhammad Irfan

The unabated demand for more capacity due to the ever-increasing internet traffic dictates that the boundaries of the state of the art maybe pushed to send more data through the network. Traditionally, this need has been satisfied by multiple wavelengths (wavelength division multiplexing), higher order modulation formats and coherent communication (either individually or combined together). WDM has the ability to reduce cost by using multiple channels within the same physical fiber, and with EDFA amplifiers, the need for O-E-O regenerators is eliminated. Moreover the availability of multiple colors allows for wavelength-based routing and network planning. Higher order modulation formats increases the capacity of the link by their ability to encode data in both the phase and amplitude of light, thereby increasing the bits/sec/Hz as compared to simple on-off keyed format. Coherent communications has also emerged as a primary means of transmitting and receiving optical data due to its support of formats that utilize both phase and amplitude to further increase the spectral efficiency of the optical channel, including quadrature amplitude modulation (QAM) and quadrature phase shift keying (QPSK). Polarization multiplexing of channels can double capacity by allowing two channels to share the same wavelength by propagating on orthogonal polarization axis and is easily supported in coherent systems where the polarization tracking can be performed in the digital domain. Furthermore, the forthcoming IEEE 100 Gbit/s Ethernet Standard, 802.3ba, provides greater bandwidth, higher data rates, and supports a mixture of modulation formats. In particular, Pol-MUX QPSK is increasingly becoming the industry's format of choice as the high spectral efficiency allows for 100 Gbit/s transmission while still occupying the current 50 GHz/channel allocation of current 10 Gbit/s OOK fiber systems. In this manner, 100 Gbit/s transfer speeds using current fiber links, amplifiers, and filters

Approaches to contactless optical thermometer in the NIR spectral range based on Nd{sup 3+} doped crystalline nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Kaldvee, K.; Nefedova, A.V. [Institute of Physics, University of Tartu, W. Ostwaldi st. 1, Tartu 50411 (Estonia); Fedorenko, S.G. [Voevodsky Institute of Chemical Kinetics and Combustion SB RAS, Novosibirsk 630090 (Russian Federation); Vanetsev, A.S. [Institute of Physics, University of Tartu, W. Ostwaldi st. 1, Tartu 50411 (Estonia); Prokhorov General Physics Institute RAS, Vavilov st. 38, Moscow 119991 (Russian Federation); Orlovskaya, E.O. [Prokhorov General Physics Institute RAS, Vavilov st. 38, Moscow 119991 (Russian Federation); Puust, L.; Pärs, M.; Sildos, I. [Institute of Physics, University of Tartu, W. Ostwaldi st. 1, Tartu 50411 (Estonia); Ryabova, A.V. [Prokhorov General Physics Institute RAS, Vavilov st. 38, Moscow 119991 (Russian Federation); National Research Nuclear University Moscow Engineering Physics Institute, Kashirskoe Highway, 31, Moscow 115409 (Russian Federation); Orlovskii, Yu.V., E-mail: orlovski@Lst.gpi.ru [Institute of Physics, University of Tartu, W. Ostwaldi st. 1, Tartu 50411 (Estonia); Prokhorov General Physics Institute RAS, Vavilov st. 38, Moscow 119991 (Russian Federation)

2017-03-15

The fluorescence kinetics and spectral intensity ratio (FIR) methods for contactless optical temperature measurement in the NIR spectral range with Nd{sup 3+} doped YAG micro- and YPO{sub 4} nanocrystals are considered and the problems are revealed. The requirements for good temperature RE doped crystalline nanoparticles sensor are formulated.

Spectral phase encoding of ultra-short optical pulse in time domain for OCDMA application.

Science.gov (United States)

Wang, Xu; Wada, Naoya

2007-06-11

We propose a novel reconfigurable time domain spectral phase encoding (SPE) scheme for coherent optical code-division-multiple-access application. In the proposed scheme, the ultra-short optical pulse is stretched by dispersive device and the SPE is done in time domain using high speed phase modulator. The time domain SPE scheme is robust to wavelength drift of the light source and is very flexible and compatible with the fiber optical system. Proof-of-principle experiments of encoding with 16-chip, 20 GHz/chip binary-phase-shift-keying codes and 1.25 Gbps data transmission have been successfully demonstrated together with an arrayed-wave-guide decoder.

Comparison of automated analysis of Cirrus HD OCT spectral-domain optical coherence tomography with stereo photographs of the optic disc.

Science.gov (United States)

Sharma, Ashish; Oakley, Jonathan D; Schiffman, Joyce C; Budenz, Donald L; Anderson, Douglas R

2011-07-01

To evaluate a new automated analysis of optic disc images obtained by spectral-domain optical coherence tomography (SD OCT). Areas of the optic disc, cup, and neural rim in SD OCT images were compared with these areas from stereoscopic photographs to represent the current traditional optic nerve evaluation. The repeatability of measurements by each method was determined and compared. Evaluation of diagnostic technology. One hundred nineteen healthy eyes, 23 eyes with glaucoma, and 7 glaucoma suspect eyes. Optic disc and cup margins were traced from stereoscopic photographs by 3 individuals independently. Optic disc margins and rim widths were determined automatically in SD OCT. A subset of photographs was examined and traced a second time, and duplicate SD OCT images also were analyzed. Agreement among photograph readers, between duplicate readings, and between SD OCT and photographs were quantified by the intraclass correlation coefficient (ICC), by the root mean square, and by the standard deviation of the differences. Optic disc areas tended to be slightly larger when judged in photographs than by SD OCT, whereas cup areas were similar. Cup and optic disc areas showed good correlation (0.8) between the average photographic reading and SD OCT, but only fair correlation of rim areas (0.4). The SD OCT was highly reproducible (ICC, 0.96-0.99). Each reader also was consistent with himself on duplicate readings of 21 photographs (ICC, 0.80-0.88 for rim area and 0.95-0.98 for all other measurements), but reproducibility was not as good as SD OCT. Measurements derived from SD OCT did not differ from photographic readings more than the readings of photographs by different readers differed from each other. Designation of the cup and optic disc boundaries by an automated analysis of SD OCT was within the range of variable designations by different readers from color stereoscopic photographs, but use of different landmarks typically made the designation of the optic disc

ANALYSIS OF IN-SITU SPECTRAL REFLECTANCE OF SAGO AND OTHER PALMS: IMPLICATIONS FOR THEIR DETECTION IN OPTICAL SATELLITE IMAGES

Directory of Open Access Journals (Sweden)

J. R. Santillan

2018-04-01

Full Text Available We present a characterization, comparison and analysis of in-situ spectral reflectance of Sago and other palms (coconut, oil palm and nipa to ascertain on which part of the electromagnetic spectrum these palms are distinguishable from each other. The analysis also aims to reveal information that will assist in selecting which band to use when mapping Sago palms using the images acquired by these sensors. The datasets used in the analysis consisted of averaged spectral reflectance curves of each palm species measured within the 345–1045 nm wavelength range using an Ocean Optics USB4000-VIS-NIR Miniature Fiber Optic Spectrometer. This in-situ reflectance data was also resampled to match the spectral response of the 4 bands of ALOS AVNIR-2, 3 bands of ASTER VNIR, 4 bands of Landsat 7 ETM+, 5 bands of Landsat 8, and 8 bands of Worldview-2 (WV2. Examination of the spectral reflectance curves showed that the near infra-red region, specifically at 770, 800 and 875 nm, provides the best wavelengths where Sago palms can be distinguished from other palms. The resampling of the in-situ reflectance spectra to match the spectral response of optical sensors made possible the analysis of the differences in reflectance values of Sago and other palms in different bands of the sensors. Overall, the knowledge learned from the analysis can be useful in the actual analysis of optical satellite images, specifically in determining which band to include or to exclude, or whether to use all bands of a sensor in discriminating and mapping Sago palms.

The optical constants and spectral specular reflectivity of highly oriented pyrolytic graphite (HOPG)

International Nuclear Information System (INIS)

Havstad, M.A.; Schildbach, M.A.; McLean, W. II.

1993-08-01

Measurements of the specular reflectivity and the optical constants of highly ordered pyrolytic graphite (HOPG) have been made using two independent optical systems. The first measures reflectance (at 1.06 μm and 293 K) by comparing the intensity of a laser beam before and after reflecting off the sample. The second determines the complex index of raft-action (from 0.55 to 8.45 μm, with sample temperatures of 293, 480, 900 and 1300 K) by ellipsometry. Agreement between the two methods is good. Moderate reflectivities are observed over the full spectral range of measurement: the spectral directional-hemispherical reflectivity at normal incidence varies from 0.41 at 0.55 μm to 0.74 at 8.45 μm. The components of the complex index of refraction increase smoothly with wavelength. The index of refraction increases from 3.10 at 0.55 μm to 7.84 at 8.45 μm. The extinction coefficient varies from 2.01 to 6.66 over the same range

Spectral, structural, optical and dielectrical studies of UV irradiated Rose Bengal thin films prepared by spin coating technique

Energy Technology Data Exchange (ETDEWEB)

Zeyada, H.M., E-mail: hzeyada@gmail.com [Department of Physics, Faculty of Science at New Damietta, University of Damietta, 34517 (Egypt); Youssif, M.I.; El-Ghamaz, N.A. [Department of Physics, Faculty of Science at New Damietta, University of Damietta, 34517 (Egypt); Aboderbala, M.E.O. [Department of Physics, Faculty of Science at New Damietta, University of Damietta, 34517 (Egypt); Department of Physics, Faculty of Science, AlJabl Al Gharbi University (Libya)

2017-02-01

Optical properties of pristine and UV irradiated Rose Bengal (RB) films have been investigated using transmittance and reflectance methods. The refractive index(n) and extinction coefficient (k) have been calculated from the absolute values of transmission and reflection spectrum. Single oscillator parameters and Drude model of free carrier absorption have been applied for analysis of the refractive index dispersion. Within the frame work of the band-to-band electron transitions theory; the fundamental absorption edge data were analyzed. Our results suggest that thickness of RB films has no effect on the absorption or the refractive indices in the investigated thicknesses range and within the experimental error. Structural transformation of films from amorphous to polycrystalline has been observed upon UV irradiation. Accordingly, the decreases of all of the absorption coefficient, the energy gap and the refractive index of RB films have been detected. Furthermore, the dependence of the optical functions on UV exposure times has been discussed based on the spectral distribution of the dielectric constant.

Characterizing CDOM Spectral Variability Across Diverse Regions and Spectral Ranges

Science.gov (United States)

Grunert, Brice K.; Mouw, Colleen B.; Ciochetto, Audrey B.

2018-01-01

Satellite remote sensing of colored dissolved organic matter (CDOM) has focused on CDOM absorption (aCDOM) at a reference wavelength, as its magnitude provides insight into the underwater light field and large-scale biogeochemical processes. CDOM spectral slope, SCDOM, has been treated as a constant or semiconstant parameter in satellite retrievals of aCDOM despite significant regional and temporal variabilities. SCDOM and other optical metrics provide insights into CDOM composition, processing, food web dynamics, and carbon cycling. To date, much of this work relies on fluorescence techniques or aCDOM in spectral ranges unavailable to current and planned satellite sensors (e.g., global variability in SCDOM and fit deviations in the aCDOM spectra using the recently proposed Gaussian decomposition method. From this, we investigate if global variability in retrieved SCDOM and Gaussian components is significant and regionally distinct. We iteratively decreased the spectral range considered and analyzed the number, location, and magnitude of fitted Gaussian components to understand if a reduced spectral range impacts information obtained within a common spectral window. We compared the fitted slope from the Gaussian decomposition method to absorption-based indices that indicate CDOM composition to determine the ability of satellite-derived slope to inform the analysis and modeling of large-scale biogeochemical processes. Finally, we present implications of the observed variability for remote sensing of CDOM characteristics via SCDOM.

Spectral domain optical coherence tomography cross-sectional image of optic nerve head during intraocular pressure elevation

Directory of Open Access Journals (Sweden)

Ji Young Lee

2014-12-01

Full Text Available AIM: To analyze changes of the optic nerve head (ONH and peripapillary region during intraocular pressure (IOP elevation in patients using spectral domain optical coherence tomography (SD-OCT.METHODS: Both an optic disc 200×200 cube scan and a high-definition 5-line raster scan were obtained from open angle glaucoma patients presented with monocular elevation of IOP (≥30 mm Hg using SD-OCT. Additional baseline characteristics included age, gender, diagnosis, best-corrected visual acuity, refractive error, findings of slit lamp biomicroscopy, findings of dilated stereoscopic examination of the ONH and fundus, IOP, pachymetry findings, and the results of visual field.RESULTS: The 24 patients were selected and divided into two groups:group 1 patients had no history of IOP elevation or glaucoma (n=14, and group 2 patients did have history of IOP elevation or glaucoma (n=10. In each patient, the study eye with elevated IOP was classified into group H (high, and the fellow eye was classified into group L (low. The mean deviation (MD differed significantly between groups H and L when all eyes were considered (P=0.047 and in group 2 (P=0.042, not in group 1 (P=0.893. Retinal nerve fiber layer (RNFL average thickness (P=0.050, rim area (P=0.015, vertical cup/disc ratio (P=0.011, cup volume (P=0.028, inferior quadrant RNFL thickness (P=0.017, and clock-hour (1, 5, and 6 RNFL thicknesses (P=0.050, 0.012, and 0.018, respectively, cup depth (P=0.008, central prelaminar layer thickness (P=0.023, mid-inferior prelaminar layer thickness (P=0.023, and nasal retinal slope (P=0.034 were significantly different between the eyes with groups H and L.CONCLUSION:RNFL average thickness, rim area, vertical cup/disc ratio, cup volume, inferior quadrant RNFL thickness, and clock-hour (1, 5, and 6 RNFL thicknesses significantly changed during acute IOP elevation.

Infrared autofluorescence, short-wave autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytomas

Directory of Open Access Journals (Sweden)

Peng Zhang

2016-05-01

Full Text Available AIM: To investigate the findings of infrared fundus autofluorescence (IR-AF and spectral-domain optical coherence tomography (SD-OCT in eyes with optic disc melanocytoma (ODM. METHODS: IR-AF findings and those of other ophthalmologic imaging examinations, including short-wave autofluorescence (SW-AF, fluorescein angiography (FA, fundus color photography, and SD-OCT of 8 eyes of 8 consecutive cases with ODM were assessed. RESULTS: The ODMs in all cases (100% presented similar IR-AF, SW-AF, and FA findings. On IR-AF images, ODMs showed outstanding hyper-AF with well-defined outline. On SW-AF images, the area of ODMs presented as hypo-AF. FA images revealed the leaking retinal telangiectasia on the surface of the ODMs. On SD-OCT images in 8 cases (100%, the ODMs were sloped with highly reflective surface, which were disorganized retina and optic nerve layers. In 7 cases (87.5%, peripapillary choroids were involved. The melanocytomas of 8 cases (100% presented as optically empty spaces. Vitreous seeds were found in one case (12.5%. CONCLUSION: IR-AF imaging may provide a new modality to evaluate the pathologic features of ODMs, and together with SW-AF imaging, offers a new tool to study biological characteristics associated with ODMs. SD-OCT is a valuable tool in delimitating the tumor extension and providing morphological information about the adjacent retinal tissue.

Spectral evolution of soft x-ray emission from optically thin, high electron temperature platinum plasmas

Directory of Open Access Journals (Sweden)

Hiroyuki Hara

2017-08-01

Full Text Available The soft x-ray spectra of heavy element plasmas are frequently dominated by unresolved transition array (UTA emission. We describe the spectral evolution of an intense UTA under optically thin conditions in platinum plasmas. The UTA was observed to have a peak wavelength around 4.6 nm at line-of-sight averaged electron temperatures less than 1.4 keV at electron densities of (2.5–7.5 × 1013 cm−3. The UTA spectral structure was due to emission from 4d–4f transitions in highly charged ions with average charge states of q = 20–40. A numerical simulation successfully reproduced the observed spectral behavior.

Extracting structural features of rat sciatic nerve using polarization-sensitive spectral domain optical coherence tomography

NARCIS (Netherlands)

Islam, M.S.; Oliveira, M.C.; Wang, Y.; Henry, F.P.; Randolph, M.A.; Park, B. H.; de Boer, J.F.

2012-01-01

We present spectral domain polarization-sensitive optical coherence tomography (SD PS-OCT) imaging of peripheral nerves. Structural and polarization-sensitive OCT imaging of uninjured rat sciatic nerves was evaluated both qualitatively and quantitatively. OCT and its functional extension, PS-OCT,

Synthesis, growth, spectral, electrical, mechanical and thermal characterization of a potential optical material: γ-glycine single crystal

Science.gov (United States)

Sivakumar, N.; Jayavel, R.; Anbalagan, G.; Yadav, R. R.

2018-06-01

Gamma glycine, an organic material was grown by slow solvent evaporation method. Conventional polythermal method was employed in the temperature range, 30-50 °C to obtain the solubility and the metastable zonewidth. The crystal and molecular structures were analyzed by X-ray powder diffraction, FT-IR and FT-Raman spectral studies. Optical refractive index was determined by prism coupling technique and was found to be 1.4488. Electrical properties such as ac conductivity and activation energy were studied for different temperatures in the frequency range from 40 Hz to 6 MHz. The dc electrical conductivity was estimated from the Cole-Cole plot and the values were found to be 2.19 × 10-6 Sm-1 at 353K and 1.46 × 10-6 Sm-1 at 373K respectively. Mechanical studies on the grown crystal revealed that the material belongs to soft materials category. Thermal conductivity and specific heat capacities were estimated by Hot Disk Thermal Constants Analyzer.

A novel and compact spectral imaging system based on two curved prisms

Science.gov (United States)

Nie, Yunfeng; Bin, Xiangli; Zhou, Jinsong; Li, Yang

2013-09-01

As a novel detection approach which simultaneously acquires two-dimensional visual picture and one-dimensional spectral information, spectral imaging offers promising applications on biomedical imaging, conservation and identification of artworks, surveillance of food safety, and so forth. A novel moderate-resolution spectral imaging system consisting of merely two optical elements is illustrated in this paper. It can realize the function of a relay imaging system as well as a 10nm spectral resolution spectroscopy. Compared to conventional prismatic imaging spectrometers, this design is compact and concise with only two special curved prisms by utilizing two reflective surfaces. In contrast to spectral imagers based on diffractive grating, the usage of compound-prism possesses characteristics of higher energy utilization and wider free spectral range. The seidel aberration theory and dispersive principle of this special prism are analyzed at first. According to the results, the optical system of this design is simulated, and the performance evaluation including spot diagram, MTF and distortion, is presented. In the end, considering the difficulty and particularity of manufacture and alignment, an available method for fabrication and measurement is proposed.

Quasi-optical analysis of a far-infrared spatio-spectral space interferometer concept

Science.gov (United States)

Bracken, C.; O'Sullivan, C.; Murphy, J. A.; Donohoe, A.; Savini, G.; Lightfoot, J.; Juanola-Parramon, R.; Fisica Consortium

2016-07-01

FISICA (Far-Infrared Space Interferometer Critical Assessment) was a three year study of a far-infrared spatio-spectral double-Fourier interferometer concept. One of the aims of the FISICA study was to set-out a baseline optical design for such a system, and to use a model of the system to simulate realistic telescope beams for use with an end-to-end instrument simulator. This paper describes a two-telescope (and hub) baseline optical design that fulfils the requirements of the FISICA science case, while minimising the optical mass of the system. A number of different modelling techniques were required for the analysis: fast approximate simulation tools such as ray tracing and Gaussian beam methods were employed for initial analysis, with GRASP physical optics used for higher accuracy in the final analysis. Results are shown for the predicted far-field patterns of the telescope primary mirrors under illumination by smooth walled rectangular feed horns. Far-field patterns for both on-axis and off-axis detectors are presented and discussed.

Spectral optical properties of selected photosynthetic microalgae producing biofuels

International Nuclear Information System (INIS)

Lee, Euntaek; Heng, Ri-Liang; Pilon, Laurent

2013-01-01

This paper presents the spectral complex index of refraction of biofuel producing photosynthetic microalgae between 400 and 750 nm. They were retrieved from their experimentally measured average absorption and scattering cross-sections. The microalgae were treated as homogeneous polydisperse spheres with equivalent diameter such that their surface area was identical to that of their actual spheroidal shape. An inverse method was developed combining Lorentz–Mie theory as the forward method and genetic algorithm. The unicellular green algae Chlamydomonas reinhardtii strain CC125 and its truncated chlorophyll antenna transformants tla1, tlaX, and tla1-CW + as well as Botryococcus braunii, Chlorella sp., and Chlorococcum littorale were investigated. These species were selected for their ability to produce either hydrogen gas or lipids for liquid fuel production. Their retrieved real and imaginary parts of the complex index of refraction were continuous functions of wavelength with absorption peaks corresponding to those of in vivo Chlorophylls a and b. The T-matrix method was also found to accurately predict the experimental measurements by treating the microalgae as axisymmetric spheroids with the experimentally measured major and minor diameter distributions and the retrieved spectral complex index of refraction. Finally, pigment mass fractions were also estimated from the retrieved absorption index. The method and/or the reported optical properties can be used in various applications from ocean remote sensing, carbon cycle study, as well as photobiological carbon dioxide mitigation and biofuel production. -- Highlights: ► Retrieval of optical properties from average absorption and scattering cross-sections. ► Inverse method based on Lorentz–Mie theory and genetic algorithm. ► Refraction and absorption indices of selected microalgae between 400 and 750 nm. ► Determination of pigment concentrations from absorption index. ► Good agreement between T

Diffractive interference optical analyzer (DiOPTER)

Science.gov (United States)

Sasikumar, Harish; Prasad, Vishnu; Pal, Parama; Varma, Manoj M.

2016-03-01

This report demonstrates a method for high-resolution refractometric measurements using, what we have termed as, a Diffractive Interference Optical Analyzer (DiOpter). The setup consists of a laser, polarizer, a transparent diffraction grating and Si-photodetectors. The sensor is based on the differential response of diffracted orders to bulk refractive index changes. In these setups, the differential read-out of the diffracted orders suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6x10-7 RIU was achieved in glass. This work focuses on devices with integrated sample well, made on low-cost PDMS. As the detection methodology is experimentally straightforward, it can be used across a wide array of applications, ranging from detecting changes in surface adsorbates via binding reactions to estimating refractive index (and hence concentration) variations in bulk samples. An exciting prospect of this technique is the potential integration of this device to smartphones using a simple interface based on transmission mode configuration. In a transmission configuration, we were able to achieve an LoD of 4x10-4 RIU which is sufficient to explore several applications in food quality testing and related fields. We are envisioning the future of this platform as a personal handheld optical analyzer for applications ranging from environmental sensing to healthcare and quality testing of food products.

Flow patterns on spectral-domain optical coherence tomography reveal flow directions at retinal vessel bifurcations

DEFF Research Database (Denmark)

Willerslev, Anne; Li, Xiao Q; Munch, Inger C

2014-01-01

PURPOSE: To study intravascular characteristics of flowing blood in retinal vessels using spectral-domain optical coherence tomography (SD-OCT). METHODS: Examination of selected arterial bifurcations and venous sites of confluence in 25 healthy 11-year-old children recruited as an ad hoc subsample...

Clinical manifestations of optic pit maculopathy as demonstrated by spectral domain optical coherence tomography.

Science.gov (United States)

Tzu, Jonathan H; Flynn, Harry W; Berrocal, Audina M; Smiddy, William E; Murray, Timothy G; Fisher, Yale L

2013-01-01

The purpose of this retrospective study was to evaluate the characteristic features, including spectral-domain optical coherence tomography (SD-OCT), clinical course, and outcome of treatment if given for patients with optic disc pit maculopathy. We investigated a consecutive series of patients with a diagnosis of optic pit maculopathy treated between 2001 and 2012 at the Bascom Palmer Eye Institute. Patients were divided into two main groups, ie, patients who were observed without surgery and patients who received surgical intervention. The main outcome measures were presenting and final visual acuity, and changes in SD-OCT imaging were recorded. Other data including age, gender, eye, age of onset, length of follow-up, location of optic pit, and location of fluid by OCT were also recorded. On OCT, 67% (12/18) of the eyes showed schisis-like cavities, 22% (4/18) had only subretinal fluid, and 17% (3/18) had only a schisis-like cavity without subretinal fluid. In the patients managed by observation, visual acuity was ≥20/200 in 6/8 eyes initially and 6/8 eyes at last follow-up. Ten of 18 patients received either focal laser, surgery or both. Six of 10 eyes undergoing surgery had initial visual acuity ≥ 20/200, and 8 of 10 eyes undergoing surgery had a visual acuity of ≥20/200 at last follow-up. In this study, many eyes were observed and remained stable during follow-up. In eyes with reduced vision, surgical intervention produced variable outcomes, and persistent intraretinal/subretinal fluid was a common occurrence.

Photoreceptor inner segment ellipsoid band integrity on spectral domain optical coherence tomography

Directory of Open Access Journals (Sweden)

Saxena S

2014-12-01

Full Text Available Sandeep Saxena,1 Khushboo Srivastav,1 Chui M Cheung,2 Joanne YW Ng,3 Timothy YY Lai3 1Retina Service, Department of Ophthalmology, King George’s Medical University Lucknow, India; 2Singapore National Eye Centre, Singapore; 3Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong Abstract: Spectral domain optical coherence tomography cross-sectional imaging of the macula has conventionally been resolved into four bands. However, some doubts were raised regarding authentication of the existence of these bands. Recently, a number of studies have suggested that the second band appeared to originate from the inner segment ellipsoids of the foveal cone photoreceptors, and therefore the previously called inner segment-outer segment junction is now referred to as inner segment ellipsoidband. Photoreceptor dysfunction may be a significant predictor of visual acuity in a spectrum of surgical and medical retinal diseases. This review aims to provide an overview and summarizes the role of the photoreceptor inner segment ellipsoid band in the management and prognostication of various vitreoretinal diseases. Keywords: spectral domain optical coherence tomography, inner segment-outer segment junction, external limiting membrane, macular hole, diabetic macular edema, age relate macular degeneration

Augmenting the spectral efficiency of enhanced PAM-DMT-based optical wireless communications.

Science.gov (United States)

Islim, Mohamed Sufyan; Haas, Harald

2016-05-30

The energy efficiency of pulse-amplitude-modulated discrete multitone modulation (PAM-DMT) decreases as the modulation order of M-PAM modulation increases. Enhanced PAM-DMT (ePAM-DMT) was proposed as a solution to the reduced energy efficiency of PAM-DMT. This was achieved by allowing multiple streams of PAM-DMT to be superimposed and successively demodulated at the receiver side. In order to maintain a distortion-free unipolar ePAM-DMT system, the multiple time-domain PAM-DMT streams are required to be aligned. However, aligning the antisymmetry in ePAM-DMT is complex and results in efficiency losses. In this paper, a novel simplified method to apply the superposition modulation on M-PAM modulated discrete multitone (DMT) is introduced. Contrary to ePAM-DMT, the signal generation of the proposed system, termed augmented spectral efficiency discrete multitone (ASE-DMT), occurs in the frequency domain. This results in an improved spectral and energy efficiency. The analytical bit error rate (BER) performance bound of the proposed system is derived and compared with Monte-Carlo simulations. The system performance is shown to offer significant electrical and optical energy savings compared with ePAM-DMT and DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM).

Accurate optical vector network analyzer based on optical single-sideband modulation and balanced photodetection.

Science.gov (United States)

Xue, Min; Pan, Shilong; Zhao, Yongjiu

2015-02-15

A novel optical vector network analyzer (OVNA) based on optical single-sideband (OSSB) modulation and balanced photodetection is proposed and experimentally demonstrated, which can eliminate the measurement error induced by the high-order sidebands in the OSSB signal. According to the analytical model of the conventional OSSB-based OVNA, if the optical carrier in the OSSB signal is fully suppressed, the measurement result is exactly the high-order-sideband-induced measurement error. By splitting the OSSB signal after the optical device-under-test (ODUT) into two paths, removing the optical carrier in one path, and then detecting the two signals in the two paths using a balanced photodetector (BPD), high-order-sideband-induced measurement error can be ideally eliminated. As a result, accurate responses of the ODUT can be achieved without complex post-signal processing. A proof-of-concept experiment is carried out. The magnitude and phase responses of a fiber Bragg grating (FBG) measured by the proposed OVNA with different modulation indices are superimposed, showing that the high-order-sideband-induced measurement error is effectively removed.

Spectral domain optical coherence tomography imaging of spectacular ecdysis in the royal python (Python regius).

Science.gov (United States)

Tusler, Charlotte A; Maggs, David J; Kass, Philip H; Paul-Murphy, Joanne R; Schwab, Ivan R; Murphy, Christopher J

2015-01-01

To describe using spectral domain optical coherence tomography (SD-OCT), digital slit-lamp biomicroscopy, and external photography, changes in the ophidian cuticle, spectacle, and cornea during ecdysis. Four normal royal pythons (Python regius). Snakes were assessed once daily throughout a complete shed cycle using nasal, axial, and temporal SD-OCT images, digital slit-lamp biomicroscopy, and external photography. Spectral domain optical coherence tomography (SD-OCT) images reliably showed the spectacular cuticle and stroma, subcuticular space (SCS), cornea, anterior chamber, iris, and Schlemm's canal. When visible, the subspectacular space (SSS) was more distended peripherally than axially. Ocular surface changes throughout ecdysis were relatively conserved among snakes at all three regions imaged. From baseline (7 days following completion of a full cycle), the spectacle gradually thickened before separating into superficial cuticular and deep, hyper-reflective stromal components, thereby creating the SCS. During spectacular separation, the stroma regained original reflectivity, and multiple hyper-reflective foci (likely fragments from the cuticular-stromal interface) were noted within the SCS. The cornea was relatively unchanged in character or thickness throughout all stages of ecdysis. Slit-lamp images did not permit observation of these changes. Spectral domain optical coherence tomography (SD-OCT) provided excellent high-resolution images of the snake anterior segment, and especially the cuticle, spectacle, and cornea of manually restrained normal snakes at all stages of ecdysis and warrants investigation in snakes with anterior segment disease. The peripheral spectacle may be the preferred entry point for diagnostic or therapeutic injections into the SSS and for initiating spectacular surgery. © 2014 American College of Veterinary Ophthalmologists.

Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008

Directory of Open Access Journals (Sweden)

J. Jung

2010-06-01

Full Text Available As a part of the IGAC (International Global Atmospheric Chemistry Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC ratio showed clear monthly variation with high values in summer and low values in winter mainly due to the enhancement of light attenuation by the internal mixing of EC. Novel approach has been suggested to retrieve the spectral light absorption coefficient (b_abs from Aethalometer raw data by using BC/EC ratio. Mass absorption efficiency, σ_abs (=b_abs/EC at 550 nm was determined to be 9.0±1.3, 8.9±1.5, 9.5±2.0, and 10.3±1.7 m² g⁻¹ in spring, summer, fall, and winter, respectively with an annual mean of 9.4±1.8 m² g⁻¹. Threshold values to classify severe haze events were suggested in this study. Increasing trend of aerosol single scattering albedo (SSA with wavelength was observed during Asian dust events while little spectral dependence of SSA was observed during long-range transport pollution (LTP events. Satellite aerosol optical thickness (AOT and Hysplit air mass backward trajectory analyses as well as chemical analysis were performed to characterize the dependence of spectral optical properties on aerosol type. Results from this study can provide useful information for studies on regional air quality and aerosol's effects on climate change.

Optimization of a Michelson interferometer with a rotating retroreflector in opitcal design, spectral resolution, and optical throughput

International Nuclear Information System (INIS)

Haschberger, P.; Tank, V.

1993-01-01

A newly designed Michelson interferometer for Fourier spectroscopy utilizes a nutating retroreflector (cube corner mirror) to generate alterations in geometrical and optical paths. The practical optomechanical design of a Fourier-transform spectrometer incorporating a rotating retroreflector for path-length alteration is considered. (The instrument has been given the name MIROR, for Michelson Interferometer with a Rotating Retroreflector.) Two parameters of the instrument are essential: the maximum optical path difference, which yields the spectral resolution of the instrument, and the diameter of the transmitted beam, which determines the throughput and hence the achievable signal-to-noise ratio. The maximum allowable beam diameter is calculated as a function of the geometry and the orientation of the rotating retroreflector and the other optical components. The geometrical configuration and the orientation of all the optical components with respect to one another are also optimized for the maximum transmitted beam diameter when the required path difference is given. A principal investigation of different possible configurations of the optical components is presented. Then a quantitative optimization for an interferometer employing a retroreflector having a 5-in. (12.7-cm) aperture diameter requiring an optical path difference of more than 10 cm (spectral resolution better than 0.1 cm -1 ) is performed. Finally a simplified but enhanced design is described. 10 refs., 15 figs

Agreement of angle closure assessments between gonioscopy, anterior segment optical coherence tomography and spectral domain optical coherence tomography

OpenAIRE

Tay, Elton Lik Tong; Yong, Vernon Khet Yau; Lim, Boon Ang; Sia, Stelson; Wong, Elizabeth Poh Ying; Yip, Leonard Wei Leon

2015-01-01

AIM: To determine angle closure agreements between gonioscopy and anterior segment optical coherence tomography (AS-OCT), as well as gonioscopy and spectral domain OCT (SD-OCT). A secondary objective was to quantify inter-observer agreements of AS-OCT and SD-OCT assessments. METHODS: Seventeen consecutive subjects (33 eyes) were recruited from the study hospital’s Glaucoma clinic. Gonioscopy was performed by a glaucomatologist masked to OCT results. OCT images were read independently by 2 ...

Coulomb field strength measurement by electro-optic spectral decoding system at the CALIFES beam line

CERN Document Server

Pan, R; Lefevre, T; Gillepsie, WA; CERN. Geneva. ATS Department

2016-01-01

Electro-optic (EO) techniques are increasingly used for longitudinal bunch profile measurements. A bunch profile monitor, based on electro-optic spectral decoding(EOSD), has been developed and demonstrated on the CALIFES beam line at CERN. The EO response is analysed using a frequency domain description, and two methods for extraction of absolute Coulomb field strengths from the electron bunch are demonstrated. Measurements at field strengths up to 1.3 MV/m agree with the expectation based on independent charge measurements.

Bandwidth scalable, coherent transmitter based on the parallel synthesis of multiple spectral slices using optical arbitrary waveform generation.

Science.gov (United States)

Geisler, David J; Fontaine, Nicolas K; Scott, Ryan P; He, Tingting; Paraschis, Loukas; Gerstel, Ori; Heritage, Jonathan P; Yoo, S J B

2011-04-25

We demonstrate an optical transmitter based on dynamic optical arbitrary waveform generation (OAWG) which is capable of creating high-bandwidth (THz) data waveforms in any modulation format using the parallel synthesis of multiple coherent spectral slices. As an initial demonstration, the transmitter uses only 5.5 GHz of electrical bandwidth and two 10-GHz-wide spectral slices to create 100-ns duration, 20-GHz optical waveforms in various modulation formats including differential phase-shift keying (DPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK) with only changes in software. The experimentally generated waveforms showed clear eye openings and separated constellation points when measured using a real-time digital coherent receiver. Bit-error-rate (BER) performance analysis resulted in a BER < 9.8 × 10(-6) for DPSK and QPSK waveforms. Additionally, we experimentally demonstrate three-slice, 4-ns long waveforms that highlight the bandwidth scalable nature of the optical transmitter. The various generated waveforms show that the key transmitter properties (i.e., packet length, modulation format, data rate, and modulation filter shape) are software definable, and that the optical transmitter is capable of acting as a flexible bandwidth transmitter.

Low-frequency acousto-optic backscattering of Bessel light beams

Science.gov (United States)

Khilo, Nikolai A.; Belyi, Vladimir N.; Khilo, Petr A.; Kazak, Nikolai S.

2018-05-01

The use of Bessel light beams, as well as Bessel acoustic beams, substantially enhances the capabilities of acousto-optic methods for control of optical field. We present a theoretical study of the process of optical Bessel beams conversion by means of backward acousto-optic scattering on a Bessel acoustic field in a transversely isotropic crystal. It is shown that, with an appropriate choice of Bessel beams parameters, the backscattering in visible spectral range can be realized at relatively low acoustic frequencies less than one gigahertz. Under conditions of phase matching and transverse spatial synchronism, the efficiency of backscattering is sufficiently high, which is interesting, for example, for construction of acousto-optic spectral analyzers.

Peripapillary Retinal Nerve Fiber Measurement with Spectral-Domain Optical Coherence Tomography in Age-Related Macular Degeneration

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Simon K. Law

2017-12-01

Full Text Available Purpose: To evaluate the relationship between the peripapillary retinal nerve fiber layer (RNFL measurements with Spectral-domain Optical Coherence Tomography (OCT and Age-related macular degeneration (AMD. Methods: Patients >60 years of age without glaucoma or record of intraocular pressure >21 mmHg and no systemic or intraocular diseases or treatment or surgical intervention that affected the RNFL underwent OCT measurement of the RNFL. The severity of AMD was staged with the Clinical Age-Related Maculopathy Staging System. The relationship between RNFL measurements and AMD stages of one eye per patient was analyzed. Results: Eighty-six eyes (46 patients with AMD and no glaucoma or other exclusion criteria received OCT RNFL measurements. Nine eyes (10.5% were excluded because of distorted peripapillary anatomy from exudative AMD (7 eyes or failure of the RNFL segmentation algorithm (2 eyes. Mean age ± S.D. of the 43 patients analyzed was 81.2 ± 7.3 years. The mean stage ± S.D. of AMD of the 77 eyes was 3.77 ± 1.05. Higher stages of AMD were statistically significantly associated with lower average RNFL and inferior sector RNFL (p = 0.049, 0 0015, respectively. The association of inferior sector RNFL and AMD stage remained statistically significant after adjusting for age. Conclusions: Spectral domain OCT is generally useful in measuring the peripapillary RNFL in eyes with different stages of AMD. Higher stage of AMD is associated with thinner peripapillary RNFL, which may masquerade as early glaucomatous damage.

Structural, optical absorption and photoluminescence spectral studies of Sm3+ ions in Alkaline-Earth Boro Tellurite glasses

Science.gov (United States)

Siva Rama Krishna Reddy, K.; Swapna, K.; Mahamuda, Sk.; Venkateswarlu, M.; Srinivas Prasad, M. V. V. K.; Rao, A. S.; Prakash, G. Vijaya

2018-05-01

Sm3+ ions doped Alkaline-Earth Boro Tellurite (AEBT) glasses were prepared by using conventional melt quenching technique and characterized using the spectroscopic techniques such as FT-IR, optical absorption, emission and decay spectral measurements to understand their utility in optoelectronic devices. From absorption spectra, the bonding parameters, nephelauxetic ratios were determined to know the nature of bonding between Sm3+ ions and its surrounding ligands. From the measured oscillator strengths, the Judd-Ofelt (J-O) intensity parameters were evaluated and in turn used to estimate various radiative parameters for the fluorescent levels of Sm3+ ions in AEBT glasses. The PL spectra of Sm3+ ions exhibit three emission bands corresponding to the transitions 4G5/2 → 6H5/2, 6H7/2 and 6H9/2 in the visible region for which the emission cross-sections and branching ratios were evaluated. The decay spectral profiles measured for 4G5/2 → 6H7/2 transition showed single exponential for lower concentration and non-exponential for higher concentration of doped rare earth ion in the as prepared glasses. Conversion of decay spectral profiles from single to non-exponential have been analyzed using Inokuti-Hirayama (I-H) model to understand the energy transfer mechanism involved in the decay process. CIE Chromaticity coordinates were measured using emission spectral data to identify the exact region of emission from the as-prepared glasses. From the evaluated radiative parameters, emission cross-sections and quantum efficiencies, it was observed that AEBT glass with 1 mol% of Sm3+ ions is more suitable for designing optoelectronic devices.

Optical vector network analyzer with improved accuracy based on polarization modulation and polarization pulling.

Science.gov (United States)

Li, Wei; Liu, Jian Guo; Zhu, Ning Hua

2015-04-15

We report a novel optical vector network analyzer (OVNA) with improved accuracy based on polarization modulation and stimulated Brillouin scattering (SBS) assisted polarization pulling. The beating between adjacent higher-order optical sidebands which are generated because of the nonlinearity of an electro-optic modulator (EOM) introduces considerable error to the OVNA. In our scheme, the measurement error is significantly reduced by removing the even-order optical sidebands using polarization discrimination. The proposed approach is theoretically analyzed and experimentally verified. The experimental results show that the accuracy of the OVNA is greatly improved compared to a conventional OVNA.

In-plane optical spectral weight redistribution in the optimally doped Ba0.6 K0.4Fe2As2 superconductor

International Nuclear Information System (INIS)

Xu Bing; Dai Yao-Min; Xiao Hong; Qiu Xiang-Gang; Lobo, R. P. S. M.

2014-01-01

We performed detailed temperature-dependent optical measurements on optimally doped Ba 0.6 K 0.4 Fe 2 As 2 single crystal. We examine the changes of the in-plane optical conductivity spectral weight in the normal state and the evolution of the superconducting condensate in the superconducting state. In the normal state, the low-frequency spectral weight shows a metallic response with an arctan (T) dependence, indicating a T-linear scattering rate behavior for the carriers. A high energy spectral weight transfer associated with the Hund's coupling occurs from the low frequencies below 4000 cm −1 ∼ 5000 cm −1 to higher frequencies up to at least 10 cm −1 . Its temperature dependence analysis suggests that the Hund's coupling strength is continuously enhanced as the temperature is reduced. In the superconducting state, the FGT sum rule is conserved according to the spectral weight estimation within the conduction bands, only about 40% of the conduction bands participates in the superconducting condensate indicating that Ba 0.6 K 0.4 Fe 2 As 2 is in dirty limit. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Retinal nerve fiber and optic disc morphology using spectral-domain optical coherence tomography in scleroderma patients.

Science.gov (United States)

Sahin-Atik, Sevinc; Koc, Feray; Akin-Sari, Sirin; Ozmen, Mustafa

2017-05-11

To evaluate the optic nerve head parameters and peripapillary retinal nerve fiber layer using spectral-domain optical coherence tomography (SD-OCT) in a systemic sclerosis (SSc) cohort and age-matched controls to determine whether SSc patients have an increased risk of normal-tension glaucoma (NTG). We examined 30 patients (3 male, 27 female) with SSc and 28 age- and sex-matched controls. Retinal nerve fiber and optic disc morphology were evaluated using Cirrus SD-OCT. Optic disc morphology measurements including disc area, rim area, average and vertical cup/disc (C/D) ratio, and cup volume were not significantly different between the study groups. The average and 4-quadrant retinal nerve fiber layer (RNFL) measurements of the C/D >0.3 subgroups were not significantly different in the patients and controls. These values were also similar for the C/D >0.5 subgroups except that the average inferior quadrant RNFL thickness of the right eyes in the patient subgroup was significantly thinner than in the control subgroup (p<0.05). Our SSc cohort had relatively shorter disease duration but increased prevalence of early glaucomatous damage signs. Our findings indicate that SSc is a risk factor for developing normal-tension glaucoma. Further studies combined with visual field evaluation are necessary to identify the long-term glaucomatous effects of SSc.

Threshold-Based Multiple Optical Signal Selection Scheme for Free-Space Optical Wavelength Division Multiplexing Systems

KAUST Repository

Nam, Sung Sik

2017-11-13

We propose a threshold-based multiple optical signal selection scheme (TMOS) for free-space optical wavelength division multiplexing systems. With this scheme, we can obtain higher spectral efficiency while reducing the possible complexity of implementation caused by the beam-selection scheme and without a considerable performance loss. To characterize the performance of our scheme, we statistically analyze the operation characteristics under conventional detection conditions (i.e., heterodyne detection and intensity modulation/direct detection techniques) with log-normal turbulence while taking into consideration the impact of pointing error. More specifically, we derive exact closed-form expressions for the outage probability, the average bit error rate, and the average spectral efficiency while adopting an adaptive modulation. Some selected results show that TMOS increases the average spectral efficiency while maintaining a minimum average bit error rate requirement.

INFORMATIVITY OF SPECTRAL OPTICAL COHERENT TOMOGRAPHY IN AGGRESSIVE POSTERIOR RETINOPATHY OF PREMATURITY

Directory of Open Access Journals (Sweden)

A. V. Tereshchenko

2017-01-01

Full Text Available The purpose: to evaluate the informativity of optical coherence tomography in patients with aggressive posterior retinopathy of prematurity. Patients and methods. spectral optical coherence tomography using portable device iVue-100 with a removable camera (Optovue, USA was held in 32 children (64 eyes with aggressive posterior retinopathy of prematurity with a gestational period 26–31 week. Results. Children with aggressive posterior retinopathy of prematurity at the stage of early clinical manifestations, in addition to the indication that the immaturity of the retina, according to the spectral optical coherence tomography revealed only a few areas of epiretinal proliferation, which are not visualized with a digital retinoscopy and binocular indirect ophthalmoscopy. When the process is more pronounced in children with retinopathy of prematurity aggressive rear stage manifestation already determined multiple zones epiretinal proliferation as a "mushroom" and "flake" conglomerates with rear zone hyaloid membrane had an uneven seal. Coarser structural disorders of the retina and the vitreoretinal interface have been identified in patients with advancedstage aggressive posterior retinopathy of prematurity. We determined the shaft extraretinal proliferation as a "comb", as well as portions of epiretinal proliferation on the border of vascularized and avascular retina, which tended to merge, and the formation of massive hyperreflection complexes, lifted back hyaloid membrane, which was not only uneven sealed, but in some places is stratified. Conclusion. Despite the complexity of the procedure and the complexity of its implementation, the data obtained are particularly valuable and informative because they allow to complement the clinical picture and objectify it. It helps to choose the optimal tactics and improvement of a differentiated approach to the treatment of aggressive posterior retinopathy of prematurity.

Broadband superluminescent diodes and semiconductor optical amplifiers for the spectral range 750 - 800 nm

International Nuclear Information System (INIS)

Il'chenko, S N; Kostin, Yu O; Kukushkin, I A; Ladugin, M A; Lapin, P I; Lobintsov, A A; Marmalyuk, Aleksandr A; Yakubovich, S D

2011-01-01

We have studied superluminescent diodes (SLDs) and semiconductor optical amplifiers (SOAs) based on an (Al x Ga 1-x )As/GaAs single quantum well structure with an Al content x ∼ 0.1 in a 10-nm-thick active layer. Depending on the length of the active channel, the single-mode fibre coupled cw output power of the SLDs is 1 to 30 mW at a spectral width of about 50 nm. The width of the optical gain band in the active channel exceeds 40 nm. Preliminary operating life tests have demonstrated that the devices are sufficiently reliable. (lasers)

Donor disc attachment assessment with intraoperative spectral optical coherence tomography during descemet stripping automated endothelial keratoplasty

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Edward Wylegala

2013-01-01

Full Text Available Optical coherence tomography has already been proven to be useful for pre- and post-surgical anterior eye segment assessment, especially in lamellar keratoplasty procedures. There is no evidence for intraoperative usefulness of optical coherence tomography (OCT. We present a case report of the intraoperative donor disc attachment assessment with spectral-domain optical coherence tomography in case of Descemet stripping automated endothelial keratoplasty (DSAEK surgery combined with corneal incisions. The effectiveness of the performed corneal stab incisions was visualized directly by OCT scan analysis. OCT assisted DSAEK allows the assessment of the accuracy of the Descemet stripping and donor disc attachment.

Crystal growth, structural, spectral, thermal, dielectric, linear and nonlinear optical characteristics of a new organic acentric material: L-Methionine-Succinic acid (2/1)

Science.gov (United States)

Nageshwari, M.; Kumari, C. Rathika Thaya; Vinitha, G.; Mohamed, M. Peer; Sudha, S.; Caroline, M. Lydia

2018-03-01

L-Methionine-Succinic acid (2/1) (LMSA), 2C5H11NO2S·C4H6O4, a novel nonlinear optical material which belongs to the class of organic category was grown-up for the first time by the technique of slow evaporation. Purity of LMSA was improved using repetitive recrystallization. LMSA was analyzed by single crystal and powder X-ray diffraction investigation to affirm the crystal structure and crystalline character. The single crystal XRD revealed that LMSA corresponds to the crystal system of triclinic with P1 as space group showing the asymmetric unit consists of a neutral succinic acid molecule and two methionine residues which are crystallographically independent existing in zwitterionic form. The functional groups existing in LMSA was accomplished using Fourier transform infrared spectroscopy. The optical transparency and the band gap energy were identified utilizing UV-Visible spectrum. The optical constants specifically reflectance and extinction coefficient clearly indicate the elevated transparency of LMSA. The thermal analyses affirmed its thermal stability. The luminescence behavior of LMSA has been analyzed by Photoluminescence (PL) spectral study. The mechanical, laser damage threshold and dielectric investigation of LMSA was done to suggest the material for practical applications. The second and third harmonic generation efficacy was confirmed by means of Kurtz-Perry and Z-scan procedure which attest its potentiality in the domain of nonlinear optics.

Investigation on the growth, spectral, lifetime, mechanical analysis and third-order nonlinear optical studies of L-methionine admixtured D-mandelic acid single crystal: A promising material for nonlinear optical applications

Science.gov (United States)

Jayaprakash, P.; Sangeetha, P.; Kumari, C. Rathika Thaya; Caroline, M. Lydia

2017-08-01

A nonlinear optical bulk single crystal of L-methionine admixtured D-mandelic acid (LMDMA) has been grown by slow solvent evaporation technique using water as solvent at ambient temperature. The crystallized LMDMA single crystal subjected to single crystal X-ray diffraction study confirmed monoclinic system with the acentric space group P21. The FTIR analysis gives information about the modes of vibration in the various functional groups present in LMDMA. The UV-visible spectral analysis assessed the optical quality and linear optical properties such as extinction coefficient, reflectance, refractive index and from which optical conductivity and electric susceptibility were also evaluated. The frequency doubling efficiency was observed using Kurtz Perry powder technique. A multiple shot laser was utilized to evaluate the laser damage threshold energy of the crystal. Discrete thermodynamic properties were carried out by TG-DTA studies. The hardness, Meyer's index, yield strength, elastic stiffness constant, Knoop hardness, fracture toughness and brittleness index were analyzed using Vickers microhardness tester. Layer growth pattern and the surface defect were examined by chemical etching studies using optical microscope. Fluorescence emission spectrum was recorded and lifetime was also studied. The electric field response of crystal was investigated from the dielectric studies at various temperatures at different frequencies. The third-order nonlinear optical response in LMDMA has been investigated using Z-scan technique with He-Ne laser at 632.8 nm and nonlinear parameters such as refractive index (n2), absorption coefficient (β) and susceptibility (χ3) investigated extensively for they are in optical phase conjucation, high-speed optical switches and optical dielectric devices.

Practical implementation of spectral-intensity dispersion-canceled optical coherence tomography with artifact suppression

Science.gov (United States)

Shirai, Tomohiro; Friberg, Ari T.

2018-04-01

Dispersion-canceled optical coherence tomography (OCT) based on spectral intensity interferometry was devised as a classical counterpart of quantum OCT to enhance the basic performance of conventional OCT. In this paper, we demonstrate experimentally that an alternative method of realizing this kind of OCT by means of two optical fiber couplers and a single spectrometer is a more practical and reliable option than the existing methods proposed previously. Furthermore, we develop a recipe for reducing multiple artifacts simultaneously on the basis of simple averaging and verify experimentally that it works successfully in the sense that all the artifacts are mitigated effectively and only the true signals carrying structural information about the sample survive.

Label swapper device for spectral amplitude coded optical packet networks monolithically integrated on InP

NARCIS (Netherlands)

Muñoz, P.; García-Olcina, R.; Habib, C.; Chen, L.R.; Leijtens, X.J.M.; Vries, de T.; Robbins, D.J.; Capmany, J.

2011-01-01

In this paper the design, fabrication and experimental characterization of an spectral amplitude coded (SAC) optical label swapper monolithically integrated on Indium Phosphide (InP) is presented. The device has a footprint of 4.8x1.5 mm2 and is able to perform label swapping operations required in

Optical spectral reshaping for directly modulated 4-pulse amplitude modulation signals

DEFF Research Database (Denmark)

Ozolins, Oskars; Da Ros, Francesco; Cristofori, Valentina

2017-01-01

The tremendous traffic growth in intra/inter-datacenters requires low-cost high-speed integrated solutions [1]. To enable a significantly reduced footprint directly modulated lasers (DMLs) have been proposed instead of large external modulators. However, it is challenging to use DMLs due to their......The tremendous traffic growth in intra/inter-datacenters requires low-cost high-speed integrated solutions [1]. To enable a significantly reduced footprint directly modulated lasers (DMLs) have been proposed instead of large external modulators. However, it is challenging to use DMLs due...... (PAM) [3] signals. However, moving to 4-PAM,many of the impressive demonstrations reported so far rely heavily on off-line digital signal processing (DSP), which increases latency, power consumption and cost. In this talk, we report on (i) a detailed numerical analysis on the complex transfer function...... of the optical filter for optical spectral reshaping in case of pulse amplitude modulation and(ii) an experimental demonstration of real-time dispersion-uncompensated transmission of 10-GBd and 14-GBd 4-PAM signals up to 10- and 26-km SSMF. This is achieved by combining a commercial 10-Gb/s DML with optical...

Full-range k-domain linearization in spectral-domain optical coherence tomography.

Science.gov (United States)

Jeon, Mansik; Kim, Jeehyun; Jung, Unsang; Lee, Changho; Jung, Woonggyu; Boppart, Stephen A

2011-03-10

A full-bandwidth k-domain linearization method for spectral-domain optical coherence tomography (SD-OCT) is demonstrated. The method uses information of the wavenumber-pixel-position provided by a translating-slit-based wavelength filter. For calibration purposes, the filter is placed either after a broadband source or at the end of the sample path, and the filtered spectrum with a narrowed line width (∼0.5 nm) is incident on a line-scan camera in the detection path. The wavelength-swept spectra are co-registered with the pixel positions according to their central wavelengths, which can be automatically measured with an optical spectrum analyzer. For imaging, the method does not require a filter or a software recalibration algorithm; it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. The accuracy of k-linearization is maximized by increasing the k-linearization order, which is known to be a crucial parameter for maintaining a narrow point-spread function (PSF) width at increasing depths. The broadening effect is studied by changing the k-linearization order by undersampling to search for the optimal value. The system provides more position information, surpassing the optimum without compromising the imaging speed. The proposed full-range k-domain linearization method can be applied to SD-OCT systems to simplify their hardware/software, increase their speed, and improve the axial image resolution. The experimentally measured width of PSF in air has an FWHM of 8 μm at the edge of the axial measurement range. At an imaging depth of 2.5 mm, the sensitivity of the full-range calibration case drops less than 10 dB compared with the uncompensated case.

Spectral studies of ocean water with space-borne sensor SCIAMACHY using Differential Optical Absorption Spectroscopy (DOAS

Directory of Open Access Journals (Sweden)

M. Vountas

2007-09-01

Full Text Available Methods enabling the retrieval of oceanic parameter from the space borne instrumentation Scanning Imaging Absorption Spectrometer for Atmospheric ChartographY (SCIAMACHY using Differential Optical Absorption Spectroscopy (DOAS are presented. SCIAMACHY onboard ENVISAT measures back scattered solar radiation at a spectral resolution (0.2 to 1.5 nm. The DOAS method was used for the first time to fit modelled Vibrational Raman Scattering (VRS in liquid water and in situ measured phytoplankton absorption reference spectra to optical depths measured by SCIAMACHY. Spectral structures of VRS and phytoplankton absorption were clearly found in these optical depths. Both fitting approaches lead to consistent results. DOAS fits correlate with estimates of chlorophyll concentrations: low fit factors for VRS retrievals correspond to large chlorophyll concentrations and vice versa; large fit factors for phytoplankton absorption correspond with high chlorophyll concentrations and vice versa. From these results a simple retrieval technique taking advantage of both measurements is shown. First maps of global chlorophyll concentrations were compared to the corresponding MODIS measurements with very promising results. In addition, results from this study will be used to improve atmospheric trace gas DOAS-retrievals from visible wavelengths by including these oceanographic signatures.

Correlation between Spectral Optical Coherence Tomography and Fundus Autofluorescence at the margins of Geographic Atrophy

Science.gov (United States)

Brar, Manpreet; Kozak, Igor; Cheng, Lingyun; Bartsch, Dirk-Uwe G.; Yuson, Ritchie; Nigam, Nitin; Oster, Stephen F.; Mojana, Francesca; Freeman, William R.

2009-01-01

Purpose We studied the appearance of margins of Geographic atrophy in high- resolution optical coherence tomography (OCT) images and correlate those changes with fundus autofluorescence imaging. Design Retrospective observational case study. Methods Patients with geographic atrophy secondary to dry age related macular degeneration (ARMD) were assessed by means of Spectral Domain OCT (Spectralis HRA/OCT; Heidelberg Engineering, Heidelberg, Germany or OTI, Inc, Toronto, Canada) as well as Autofluoresence Imaging (HRA or Spectralis Heidelberg Engineering, Heidelberg, Germany): The outer retinal layer alterations were analyzed in the junctional zone between normal retina and atrophic retina, and correlated with corresponding fundus autofluorescence. Results 23 eyes of 16 patients aged between 62 years to 96 years were examined. There was a significant association between OCT findings and the fundus autofluorescence findings(r=0.67, pautofluorescence; Smooth margins on OCT correspond significantly to normal fundus autofluorescence. (Kappa-0.7348, pautofluorescence; secondary to increased lipofuscin may together serve as determinants of progression of geographic atrophy. PMID:19541290

Multimode laser beam analyzer instrument using electrically programmable optics.

Science.gov (United States)

Marraccini, Philip J; Riza, Nabeel A

2011-12-01

Presented is a novel design of a multimode laser beam analyzer using a digital micromirror device (DMD) and an electronically controlled variable focus lens (ECVFL) that serve as the digital and analog agile optics, respectively. The proposed analyzer is a broadband laser characterization instrument that uses the agile optics to smartly direct light to the required point photodetectors to enable beam measurements of minimum beam waist size, minimum waist location, divergence, and the beam propagation parameter M(2). Experimental results successfully demonstrate these measurements for a 500 mW multimode test laser beam with a wavelength of 532 nm. The minimum beam waist, divergence, and M(2) experimental results for the test laser are found to be 257.61 μm, 2.103 mrad, 1.600 and 326.67 μm, 2.682 mrad, 2.587 for the vertical and horizontal directions, respectively. These measurements are compared to a traditional scan method and the results of the beam waist are found to be within error tolerance of the demonstrated instrument.

Magnetic field effects on spectrally resolved lifetime of on-line oxygen monitoring using magneto-optic probes

Science.gov (United States)

Mermut, O.; Gallant, P.; Le Bouch, N.; Leclair, S.; Noiseux, I.; Vernon, M.; Morin, J.-F.; Diamond, K.; Patterson, M. S.; Samkoe, K.; Pogue, B.

2009-02-01

Multimodal agents that serve as both probes for contrast and light-activated effectors of cellular processes in diseased tissue were developed. These agents were introduced into multicellular tumor spheroids (3D tissue models) and in the chorioallantoic membrane (CAM) of a chicken embryo. The luminescence decay was examined using a novel technique involving a spectrally-resolved fluorescence lifetime apparatus integrated with a weak electromagnet. A spectrallyresolved lifetime setup was used to identify magneto-optic species sensitive to magnetic field effects and distinguish from background emissions. We demonstrate that the applied magnetic fields can alter reaction rates and product distribution of some dyes detected by time- and spectrally-resolved luminescence changes. We will discuss the use of exogenous magneto-optical probes taken up in tumors to both induce phototoxicity, a process that is governed by complex and dynamically evolving mechanisms involving reactive oxygen species, and monitor treatment progress. The magnetic field enhancement, measured over a range of weak fields (0-300 mT) is correlated to oxygenation and may be used to monitor dynamic changes occurring due to oxygen consumption over the course of photodynamic therapy. Such online measurements provide the possibility to derive real-time information about response to treatment via monitoring magnetic field enhancement/suppression of the time-resolved, spectrally-resolved luminescence of the probe at the site of the treatment directly. Magnetic perturbation of lifetime can serve as a status reporter, providing optical feedback of oxygen-mediated treatments in situ and allowing for real-time adjustment of a phototherapy treatment plan.

Magneto-optic Doppler analyzer: a new instrument to measure mesopause winds

Science.gov (United States)

Williams, Bifford P.; Tomczyk, Steven

1996-11-01

The magneto-optic Doppler analyzer (MODA) is a new type of passive optical instrument that one can use to measure the Doppler shift of the sodium nightglow emitted at approximately 91 km near the mesopause. From this measurement, horizontal wind signatures are inferred. The MODA is based on a sodium vapor magneto-optic filter that provides inherent wavelength stability at a low cost. The instrument has been used to take nightly zonal and meridional wind measurements since October 1994 at Niwot Ridge, Colorado (40 N, 105 W). We obtained an internally consistent wind signal and measured the semidiurnal tide for several seasons.

Constellation Shaping for Fiber-optic Channels with QAM and High Spectral Efficiency

DEFF Research Database (Denmark)

Yankov, Metodi Plamenov; Zibar, Darko; Larsen, Knud J.

2014-01-01

In this letter the fiber-optic communication channel with Quadrature Amplitude Modulation (QAM) input constella- tion is treated. Using probabilistic shaping, we show that high order QAM constellations can achieve and slightly exceed the lower bound on the channel capacity, set by ring constellat......In this letter the fiber-optic communication channel with Quadrature Amplitude Modulation (QAM) input constella- tion is treated. Using probabilistic shaping, we show that high order QAM constellations can achieve and slightly exceed the lower bound on the channel capacity, set by ring...... constellations in [1]. We then propose a mapping function for turbo coded bit interleaved coded modulation based on optimization of the mu- tual information between the channel input and output. Using this mapping, spectral efficiency as high as 6.5 bits/s/Hz/polarization is achieved on a simulated single...... channel long-haul fiber-optical link excluding the pilot overhead, used for synchronization, and taking into account frequency and phase mismatch impairments, as well as laser phase noise and analog-to-digital conversion quantization impairments. The simulations suggest that major improvements can...

UV-Vis-IR spectral complex refractive indices and optical properties of brown carbon aerosol from biomass burning

Science.gov (United States)

Sumlin, Benjamin J.; Heinson, Yuli W.; Shetty, Nishit; Pandey, Apoorva; Pattison, Robert S.; Baker, Stephen; Hao, Wei Min; Chakrabarty, Rajan K.

2018-02-01

Constraining the complex refractive indices, optical properties and size of brown carbon (BrC) aerosols is a vital endeavor for improving climate models and satellite retrieval algorithms. Smoldering wildfires are the largest source of primary BrC, and fuel parameters such as moisture content, source depth, geographic origin, and fuel packing density could influence the properties of the emitted aerosol. We measured in situ spectral (375-1047 nm) optical properties of BrC aerosols emitted from smoldering combustion of Boreal and Indonesian peatlands across a range of these fuel parameters. Inverse Lorenz-Mie algorithms used these optical measurements along with simultaneously measured particle size distributions to retrieve the aerosol complex refractive indices (m = n + iκ). Our results show that the real part n is constrained between 1.5 and 1.7 with no obvious functionality in wavelength (λ), moisture content, source depth, or geographic origin. With increasing λ from 375 to 532 nm, κ decreased from 0.014 to 0.003, with corresponding increase in single scattering albedo (SSA) from 0.93 to 0.99. The spectral variability of κ follows the Kramers-Kronig dispersion relation for a damped harmonic oscillator. For λ ≥ 532 nm, both κ and SSA showed no spectral dependency. We discuss differences between this study and previous work. The imaginary part κ was sensitive to changes in FPD, and we hypothesize mechanisms that might help explain this observation.

Heavy carriers, non-drude optical conductivity and transfer of spectral weight in MnSi

International Nuclear Information System (INIS)

Mena, F.P.; Damascelli, A.; Marel, D. van der; Fath, M.; Menovsky, A.A.; Mydosh, J.A.

2004-01-01

The optical properties of the weak magnetic metal MnSi were determined using reflectance at 80 deg. (2-800 meV) and ellipsometry (0.8-4.5 eV). At low frequencies in the magnetic phase we observe a departure of the optical conductivity from Drude behavior: m*(ω)/m is strongly frequency dependent and 1/τ(ω) is approximately linear in frequency. In fact, we show that σ(ω)/σ(0)=(1+iω/Γ) -0.5 . Moreover, in the magnetic phase, the plasma frequency shifts to the red indicating that spectral weight is transferred to high frequencies. This is opposite to the effect recently seen in other magnetic compounds

Multi-spectral and fluorescence diffuse optical tomography of breast cancer

Science.gov (United States)

Corlu, Alper

Multi-spectral and fluorescence diffuse optical tomography (DOT) techniques are explored and applied to image human breast cancer in vivo. Image reconstruction algorithms that utilize first and second order gradient information are described in detail. Breast DOT requires large computational memory and long run times. To this end, parallel computation techniques were developed appropriate to each reconstruction algorithm. A parallel plate DOT instrument developed for breast cancer imaging is described. The system relies heavily on continuous-wave (CW) transmission measurements and utilizes frequency domain (FD) measurements on the reemission side. However, traditional DOT image reconstruction methods based on CW measurements fail to separate tissue absorption and scattering uniquely. In this manuscript, multi-spectral DOT is shown to be capable of minimizing cross-talk and retrieving spectral parameters almost uniquely when the measurement wavelengths are optimized. A theoretical framework to select optimum wavelengths is provided, and tested with computer simulations. Results from phantom spectroscopy experiments and in vivo patient measurements support the notion that multi-spectral methods are superior to traditional DOT image reconstruction schemes. The same breast DOT instrument is improved and utilized to obtain the first in vivo images of human breast cancer based on fluorescence DOT (FDOT). To this end the fluorophore Indocyanine Green (ICG) is injected intravenously and fluorescence excitation and detection are accomplished in the soft-compression, parallel-plane, transmission geometry using laser sources at 786 nm and spectrally filtered CCD detection. Careful phantom and in vivo measurements are carried on to assure that the signals are due to ICG fluorescence, rather than tissue autofluorescence and excitation light leakage. An in vivo measurement protocol is designed to maximize the ICG contrast by acquiring full fluorescence tomographic scan during

Development of a low-cost, 11 µm spectral domain optical coherence tomography surface profilometry prototype

Science.gov (United States)

Suliali, Nyasha J.; Baricholo, Peter; Neethling, Pieter H.; Rohwer, Erich G.

2017-06-01

A spectral-domain Optical Coherence Tomography (OCT) surface profilometry prototype has been developed for the purpose of surface metrology of optical elements. The prototype consists of a light source, spectral interferometer, sample fixture and software currently running on Microsoft® Windows platforms. In this system, a broadband light emitting diode beam is focused into a Michelson interferometer with a plane mirror as its sample fixture. At the interferometer output, spectral interferograms of broadband sources were measured using a Czerny-Turner mount monochromator with a 2048-element complementary metal oxide semiconductor linear array as the detector. The software performs importation and interpolation of interferometer spectra to pre-condition the data for image computation. One dimensional axial OCT images were computed by Fourier transformation of the measured spectra. A first reflection surface profilometry (FRSP) algorithm was then formulated to perform imaging of step-function-surfaced samples. The algorithm re-constructs two dimensional colour-scaled slice images by concatenation of 21 and 13 axial scans to form a 10 mm and 3.0 mm slice respectively. Measured spectral interferograms, computed interference fringe signals and depth reflectivity profiles were comparable to simulations and correlated to displacements of a single reflector linearly translated about the arm null-mismatch point. Surface profile images of a double-step-function-surfaced sample, embedded with inclination and crack detail were plotted with an axial resolution of 11 μm. The surface shape, defects and misalignment relative to the incident beam were detected to the order of a micron, confirming high resolution of the developed system as compared to electro-mechanical surface profilometry techniques.

Hyper-spectral modulation fluorescent imaging using double acousto-optical tunable filter based on TeO2-crystals

International Nuclear Information System (INIS)

Zaytsev, Kirill I; Perchik, Alexey V; Chernomyrdin, Nikita V; Yurchenko, Stanislav O; Kudrin, Konstantin G; Reshetov, Igor V

2015-01-01

We have proposed a method for hyper-spectral fluorescent imaging based on acousto-optical filtering. The object of interest was pumped using ultraviolet radiation of mercury lamp equipped with monochromatic excitation filter with the window of transparency centered at 365 nm. Double TeO 2 -based acousto-optical filter, tunable in range from 430 to 780 nm and having 2 nm bandwidth of spectral transparency, was used in order to detect quasimonochromatic images of object fluorescence. Modulating of ultraviolet pump intensity was used in order to reduce an impact of non-fluorescent background on the sample fluorescent imaging. The technique for signal-to-noise ratio improvement, based on fluorescence intensity estimation via digital processing of modulated video sequence of fluorescent object, was introduced. We have implemented the proposed technique for the test sample studying and we have discussed its possible applications

Geometric optimisation of an accurate cosine correcting optic fibre coupler for solar spectral measurement

Science.gov (United States)

Cahuantzi, Roberto; Buckley, Alastair

2017-09-01

Making accurate and reliable measurements of solar irradiance is important for understanding performance in the photovoltaic energy sector. In this paper, we present design details and performance of a number of fibre optic couplers for use in irradiance measurement systems employing remote light sensors applicable for either spectrally resolved or broadband measurement. The angular and spectral characteristics of different coupler designs are characterised and compared with existing state-of-the-art commercial technology. The new coupler designs are fabricated from polytetrafluorethylene (PTFE) rods and operate through forward scattering of incident sunlight on the front surfaces of the structure into an optic fibre located in a cavity to the rear of the structure. The PTFE couplers exhibit up to 4.8% variation in scattered transmission intensity between 425 nm and 700 nm and show minimal specular reflection, making the designs accurate and reliable over the visible region. Through careful geometric optimization near perfect cosine dependence on the angular response of the coupler can be achieved. The PTFE designs represent a significant improvement over the state of the art with less than 0.01% error compared with ideal cosine response for angles of incidence up to 50°.

Geometric optimisation of an accurate cosine correcting optic fibre coupler for solar spectral measurement.

Science.gov (United States)

Cahuantzi, Roberto; Buckley, Alastair

2017-09-01

Making accurate and reliable measurements of solar irradiance is important for understanding performance in the photovoltaic energy sector. In this paper, we present design details and performance of a number of fibre optic couplers for use in irradiance measurement systems employing remote light sensors applicable for either spectrally resolved or broadband measurement. The angular and spectral characteristics of different coupler designs are characterised and compared with existing state-of-the-art commercial technology. The new coupler designs are fabricated from polytetrafluorethylene (PTFE) rods and operate through forward scattering of incident sunlight on the front surfaces of the structure into an optic fibre located in a cavity to the rear of the structure. The PTFE couplers exhibit up to 4.8% variation in scattered transmission intensity between 425 nm and 700 nm and show minimal specular reflection, making the designs accurate and reliable over the visible region. Through careful geometric optimization near perfect cosine dependence on the angular response of the coupler can be achieved. The PTFE designs represent a significant improvement over the state of the art with less than 0.01% error compared with ideal cosine response for angles of incidence up to 50°.

Retrieval of spectral aerosol optical thickness over land using ocean color sensors MERIS and SeaWiFS

Directory of Open Access Journals (Sweden)

W. von Hoyningen-Huene

2011-02-01

Full Text Available For the determination of aerosol optical thickness (AOT Bremen AErosol Retrieval (BAER has been developed. Method and main features on the aerosol retrieval are described together with validation and results. The retrieval separates the spectral aerosol reflectance from surface and Rayleigh path reflectance for the shortwave range of the measured spectrum of top-of-atmosphere reflectance for wavelength less than 0.670 μm. The advantage of MERIS (Medium Resolution Imaging Spectrometer on the Environmental Satellite – ENVISAT – of the European Space Agency – ESA and SeaWiFS (Sea viewing Wide Field Sensor on OrbView-2 spacecraft observations is the availability of several spectral channels in the blue and visible range enabling the spectral determination of AOT in 7 (or 6 channels (0.412–0.670 μm and additionally channels in the NIR, which can be used to characterize the surface properties. A dynamical spectral surface reflectance model for different surface types is used to obtain the spectral surface reflectance for this separation. The normalized differential vegetation index (NDVI, taken from the satellite observations, is the model input. Further surface bi-directional reflectance distribution function (BRDF is considered by the Raman-Pinty-Verstraete (RPV model. Spectral AOT is obtained from aerosol reflectance using look-up-tables, obtained from radiative transfer calculations with given aerosol phase functions and single scattering albedos either from aerosol models, given by model package "optical properties of aerosol components" (OPAC or from experimental campaigns. Validations of the obtained AOT retrieval results with data of Aerosol Robotic Network (AERONET over Europe gave a preference for experimental phase functions derived from almucantar measurements. Finally long-term observations of SeaWiFS have been investigated for 11 year trends in AOT. Western European regions have negative trends with decreasing AOT with time

Multi-spectral optical scanners for commercial earth observation missions

Science.gov (United States)

Schröter, Karin; Engel, Wolfgang; Berndt, Klaus

2017-11-01

In recent years, a number of commercial Earth observation missions have been initiated with the aim to gather data in the visible and near-infrared wavelength range. Some of these missions aim at medium resolution (5 to 10 m) multi-spectral imaging with the special background of daily revisiting. Typical applications aim at monitoring of farming area for growth control and harvest prediction, irrigation control, or disaster monitoring such as hail damage in farming, or flood survey. In order to arrive at profitable business plans for such missions, it is mandatory to establish the space segment, i.e. the spacecraft with their opto -electronic payloads, at minimum cost while guaranteeing maximum reliability for mission success. As multiple spacecraft are required for daily revisiting, the solutions are typically based on micro-satellites. This paper presents designs for multi-spectral opto-electric scanners for this type of missions. These designs are drive n by minimum mass and power budgets of microsatellites, and the need for minimum cost. As a consequence, it is mandatory to arrive at thermally robust, compact telescope designs. The paper gives a comparison between refractive, catadioptric, and TMA optics. For mirror designs, aluminium and Zerodur mirror technologies are briefly discussed. State-of-the art focal plane designs are presented. The paper also addresses the choice of detector technologies such as CCDs and CMOS Active Pixel Sensors. The electronics of the multi-spectral scanners represent the main design driver regarding power consumption, reliability, and (most often) cost. It can be subdivided into the detector drive electronics, analog and digital data processing chains, the data mass memory unit, formatting and down - linking units, payload control electronics, and local power supply. The paper gives overviews and trade-offs between data compression strategies and electronics solutions, mass memory unit designs, and data formatting approaches

Quantitative functional optical imaging of the human skin using multi-spectral imaging

International Nuclear Information System (INIS)

Kainerstorfer, J. M.

2010-01-01

Light tissue interactions can be described by the physical principles of absorption and scattering. Based on those parameters, different tissue types and analytes can be distinguished. Extracting blood volume and oxygenation is of particular interest in clinical routines for tumor diagnostics and treatment follow up, since they are parameters of angiogenic processes. The quantification of those analytes in tissue can be done by physical modeling of light tissue interaction. The physical model used here is the random walk theory. However, for quantification and clinical usefulness, one has to account for multiple challenges. First, one must consider the effect of topology of the sample on measured physical parameters. Second, diffusion of light inside the tissue is dependent on the structure of the sample imaged. Thus, the structural conformation has to be taken into account. Third, clinical translation of imaging modalities is often hindered due to the complicated post-processing of data, not providing results in real-time. In this thesis, two imaging modalities are being utilized, where the first one, diffuse multi-spectral imaging, is based on absorption contrast and spectral characteristics and the second one, Optical Coherence Tomography (OCT), is based on scattering changes within the tissue. Multi-spectral imaging can provide spatial distributions of blood volume and blood oxygenation and OCT yields 3D structural images with micrometer resolution. In order to address the challenges mentioned above, a curvature correction algorithm for taking the topology into account was developed. Without taking curvature of the object into account, reconstruction of optical properties is not accurate. The method developed removes this artifact and recovers the underlying data, without the necessity of measuring the object's shape. The next step was to recover blood volume and oxygenation values in real time. Principal Component Analysis (PCA) on multi spectral images is

Two-harmonic complex spectral-domain optical coherence tomography using achromatic sinusoidal phase modulation

Science.gov (United States)

Lu, Sheng-Hua; Huang, Siang-Ru; Chou, Che-Chung

2018-03-01

We resolve the complex conjugate ambiguity in spectral-domain optical coherence tomography (SD-OCT) by using achromatic two-harmonic method. Unlike previous researches, the optical phase of the fiber interferometer is modulated by an achromatic phase shifter based on an optical delay line. The achromatic phase modulation leads to a wavelength-independent scaling coefficient for the two harmonics. Dividing the mean absolute value of the first harmonic by that of the second harmonic in a B-scan interferogram directly gives the scaling coefficient. It greatly simplifies the determination of the magnitude ratio between the two harmonics without the need of third harmonic and cumbersome iterative calculations. The inverse fast Fourier transform of the complex-valued interferogram constructed with the scaling coefficient, first and second harmonics yields a full-range OCT image. Experimental results confirm the effectiveness of the proposed achromatic two-harmonic technique for suppressing the mirror artifacts in SD-OCT images.

Phase extracting algorithms analysis in the white-light spectral interferometry

Science.gov (United States)

Guo, Tong; Li, Bingtong; Li, Minghui; Chen, Jinping; Fu, Xing; Hu, Xiaotang

2018-01-01

As an optical testing method, white-light spectral interferometry has the characteristics of non-contact, high precision. The phase information can be obtained by analyzing the spectral interference signal of the tested sample, and then the absolute distance is calculated. Fourier transform method, temporal phase-shifting method, spatial phase-shifting method and envelope method can be used to extract the phase information of the spectral interference signal. In this paper, the performance of four methods to extract phase information is simulated and analyzed by using the ideal spectral interference signal. It turns out that temporal phase-shifting method has the performance of high precision, the results of Fourier transform method and envelop method are distorted at the edge of the signal, and spatial phase-shifting method has the worst precision. Adding different levels of white noise to the ideal signal, temporal phase-shifting method is most accurate, while Fourier transform method and envelope method are relatively poor. Finally, the absolute distance measurement experiment is carried out on the constructed test system, and the results are consistent with the simulation ones.

[Development of a portable mid-infrared rapid analyzer for oil concentration in water based on MEMS linear sensor array].

Science.gov (United States)

Gao, Zhi-fan; Zeng, Li-bo; Shi, Lei; Li, Kai; Yang, Yuan-zhou; Wu, Qiong-shui

2014-06-01

Aiming at the existing problems such as weak environmental adaptability, low analytic efficiency and poor measuring repeatability in the traditional spectral oil analyzers, the present paper designed a portable mid-infrared rapid analyzer for oil concentration in water. To reduce the volume of the instrument, the non-symmetrical folding M-type Czerny-Turner optical structure was adopted in the core optical path. With a periodically rotating chopper, controlled by digital PID algorithm, applied for infrared light modulation, the modulating accuracy reached ±0.5%. Different from traditional grating-scanning spectrophotometers, this instrument used a fixed grating for light dispersion and avoided rotating error in the course of the measuring procedures. A new-type MEMS infrared linear sensor array was applied for modulated spectral signals detection, which improved the measuring efficiency remarkably. Optical simulation and experimental results indicate that the spectral range is 2 800 - 3 200 cm(-1), the spectral resolution is 6 cm(-1) (@3 130 cm(-1)), and the signal to noise ratio is up to 5 200 : 1. The acquisition time is 13 milliseconds per spectrogram, and the standard deviation of absorbance is less than 3 x 10(-3). These performances meet the standards of oil concentration measurements perfectly. Compared with traditional infrared spectral analyzers for oil concentration, the instrument demonstrated in this paper has many advantages such as smaller size, more efficiency, higher precision, and stronger vibration & moisture isolation. In addition, the proposed instrument is especially suitable for the environmental monitoring departments to implement real-time measurements in the field for oil concentration in water, hence it has broad prospects of application in the field of water quality monitoring.

Polarization modeling and predictions for DKIST part 3: focal ratio and thermal dependencies of spectral polarization fringes and optic retardance

Science.gov (United States)

Harrington, David M.; Sueoka, Stacey R.

2018-01-01

Data products from high spectral resolution astronomical polarimeters are often limited by fringes. Fringes can skew derived magnetic field properties from spectropolarimetric data. Fringe removal algorithms can also corrupt the data if the fringes and object signals are too similar. For some narrow-band imaging polarimeters, fringes change the calibration retarder properties and dominate the calibration errors. Systems-level engineering tools for polarimetric instrumentation require accurate predictions of fringe amplitudes, periods for transmission, diattenuation, and retardance. The relevant instabilities caused by environmental, thermal, and optical properties can be modeled and mitigation tools developed. We create spectral polarization fringe amplitude and temporal instability predictions by applying the Berreman calculus and simple interferometric calculations to optics in beams of varying F/ number. We then apply the formalism to superachromatic six-crystal retarders in converging beams under beam thermal loading in outdoor environmental conditions for two of the world's largest observatories: the 10-m Keck telescope and the Daniel K. Inouye Solar Telescope (DKIST). DKIST will produce a 300-W optical beam, which has imposed stringent requirements on the large diameter six-crystal retarders, dichroic beamsplitters, and internal optics. DKIST retarders are used in a converging beam with F/ ratios between 8 and 62. The fringe spectral periods, amplitudes, and thermal models of retarder behavior assisted DKIST optical designs and calibration plans with future application to many astronomical spectropolarimeters. The Low Resolution Imaging Spectrograph with polarimetry instrument at Keck also uses six-crystal retarders in a converging F / 13 beam in a Cassegrain focus exposed to summit environmental conditions providing observational verification of our predictions.

Influences of optical-spectrum errors on excess relative intensity noise in a fiber-optic gyroscope

Science.gov (United States)

Zheng, Yue; Zhang, Chunxi; Li, Lijing

2018-03-01

The excess relative intensity noise (RIN) generated from broadband sources degrades the angular-random-walk performance of a fiber-optic gyroscope dramatically. Many methods have been proposed and managed to suppress the excess RIN. However, the properties of the excess RIN under the influences of different optical errors in the fiber-optic gyroscope have not been systematically investigated. Therefore, it is difficult for the existing RIN-suppression methods to achieve the optimal results in practice. In this work, the influences of different optical-spectrum errors on the power spectral density of the excess RIN are theoretically analyzed. In particular, the properties of the excess RIN affected by the raised-cosine-type ripples in the optical spectrum are elaborately investigated. Experimental measurements of the excess RIN corresponding to different optical-spectrum errors are in good agreement with our theoretical analysis, demonstrating its validity. This work provides a comprehensive understanding of the properties of the excess RIN under the influences of different optical-spectrum errors. Potentially, it can be utilized to optimize the configurations of the existing RIN-suppression methods by accurately evaluating the power spectral density of the excess RIN.

Influence of corneal power on circumpapillary retinal nerve fiber layer and optic nerve head measurements by spectral-domain optical coherence tomography

Directory of Open Access Journals (Sweden)

Kazunori Hirasawa

2017-09-01

Full Text Available AIM: To evaluate the influence of corneal power on circumpapillary retinal nerve fiber layer (cpRNFL and optic nerve head (ONH measurements by spectral-domain optical coherence tomography (SD-OCT. METHODS: Twenty-five eyes of 25 healthy participants (mean age 23.6±3.6y were imaged by SD-OCT using horizontal raster scans. Disposable soft contact lenses of different powers (from −11 to +5 diopters including 0 diopter were worn to induce 2-diopter changes in corneal power. Differences in the cpRNFL and ONH measurements per diopter of change in corneal power were analyzed. RESULTS: As corneal power increased by 1 diopter, total and quadrant cpRNFL thicknesses, except for the nasal sector, decreased by −0.19 to −0.32 μm (P<0.01. Furthermore, the disc, cup, and rim areas decreased by −0.017, −0.007, and −0.015 mm2, respectively (P<0.001; the cup and rim volumes decreased by −0.0013 and −0.006 mm3, respectively (P<0.01; and the vertical and horizontal disc diameters decreased by −0.006 and −0.007 mm, respectively (P<0.001. CONCLUSION: For more precise OCT imaging, the ocular magnification should be corrected by considering both the axial length and corneal power. However, the effect of corneal power changes on cpRNFL thickness and ONH topography are small when compare with those of the axial length.

Comprehensive method for analyzing the power conversion efficiency of organic solar cells under different spectral irradiances considering both photonic and electrical characteristics

International Nuclear Information System (INIS)

Chong, Kok-Keong; Khlyabich, Petr P.; Hong, Kai-Jeat; Reyes-Martinez, Marcos; Rand, Barry P.; Loo, Yueh-Lin

2016-01-01

Highlights: • Method to analyze power-conversion efficiency under various solar irradiance. • Power-conversion efficiency at local irradiance is 5.4% higher than AM1.5G. • Diffuse local irradiance has gain of 23.7–27.9% relative to AM1.5G conditions. • Annual average energy density yield is estimated as 31.89 kW h/m 2 in Malaysia. - Abstract: The solar spectral irradiance varies significantly for different locations and time due to latitude, humidity, cosine effect of incident sunlight, etc. For convenience, the power-conversion efficiency of a solar cell is referenced to the international standard of AM1.5G spectral irradiance, which inevitably leads to varying performance of deployed solar cells under the specific local climate and insolation conditions. To predict the actual performance of solar cells under local climate conditions, we propose a methodology to compute the power-conversion efficiency of organic photovoltaic cells based upon indoor measurement with a solar simulator, the measured local solar spectrum, and making use of both optical and electrical factors. From our study, the annual average energy density yield of poly(3-hexylthiophene):phenyl-C 61 -butyric acid methyl ester (P3HT:PCBM) bulk-heterojunction organic solar cells under the local spectral irradiance of Malaysia is estimated to be 31.89 kW h/m 2 and the power-conversion efficiency is increased by 5.4% compared to that measured under AM1.5G conditions. In addition, diffuse solar irradiance (cloudy condition) was found to be in favor of P3HT:PCBM solar cells, with gain of 23.7–27.9% relative to AM1.5G conditions.

XOP: a multiplatform graphical user interface for synchrotron radiation spectral and optics calculations

Science.gov (United States)

Sanchez del Rio, Manuel; Dejus, Roger J.

1997-11-01

XOP (X-ray OPtics utilities) is a graphical user interface (GUI) created to execute several computer programs that calculate the basic information needed by a synchrotron beamline scientist (designer or experimentalist). Typical examples of such calculations are: insertion device (undulator or wiggler) spectral and angular distributions, mirror and multilayer reflectivities, and crystal diffraction profiles. All programs are provided to the user under a unified GUI, which greatly simplifies their execution. The XOP optics applications (especially mirror calculations) take their basic input (optical constants, compound and mixture tables) from a flexible file-oriented database, which allows the user to select data from a large number of choices and also to customize their own data sets. XOP includes many mathematical and visualization capabilities. It also permits the combination of reflectivities from several mirrors and filters, and their effect, onto a source spectrum. This feature is very useful when calculating thermal load on a series of optical elements. The XOP interface is written in the IDL (Interactive Data Language). An embedded version of XOP, which freely runs under most Unix platforms (HP, Sun, Dec, Linux, etc) and under Windows95 and NT, is available upon request.

XOP: A multiplatform graphical user interface for synchrotron radiation spectral and optics calculations

Energy Technology Data Exchange (ETDEWEB)

Sanchez del Rio, M. [European Synchrotron Radiation Facility, Grenoble (France); Dejus, R.J. [Argonne National Lab., IL (United States). Advanced Photon Source

1997-09-01

XOP (X-ray OPtics utilities) is a graphical user interface (GUI) created to execute several computer programs that calculate the basic information needed by a synchrotron beamline scientist (designer or experimentalist). Typical examples of such calculations are: insertion device (undulator or wiggler) spectral and angular distributions, mirror and multilayer reflectivities, and crystal diffraction profiles. All programs are provided to the user under a unified GUI, which greatly simplifies their execution. The XOP optics applications (especially mirror calculations) take their basic input (optical constants, compound and mixture tables) from a flexible file-oriented database, which allows the users to select data from a large number of choices and also to customize their own data sets. XOP includes many mathematical and visualization capabilities. It also permits the combination of reflectivities from several mirrors and filters, and their effect, onto a source spectrum. This feature is very useful when calculating thermal load on a series of optical elements. The XOP interface is written in the IDL (Interactive Data Language). An embedded version of XOP, which freely runs under most Unix platforms (HP, Sun, Dec, Linux, etc) and under Windows95 and NT, is available upon request.

THE POTENTIAL IMPORTANCE OF BINARY EVOLUTION IN ULTRAVIOLET-OPTICAL SPECTRAL FITTING OF EARLY-TYPE GALAXIES

International Nuclear Information System (INIS)

Li, Zhongmu; Mao, Caiyan; Chen, Li; Zhang, Qian; Li, Maocai

2013-01-01

Most galaxies possibly contain some binaries, and more than half of Galactic hot subdwarf stars, which are thought to be a possible origin of the UV-upturn of old stellar populations, are found in binaries. However, the effect of binary evolution has not been taken into account in most works on the spectral fitting of galaxies. This paper studies the role of binary evolution in the spectral fitting of early-type galaxies, via a stellar population synthesis model including both single and binary star populations. Spectra from ultraviolet to optical bands are fitted to determine a few galaxy parameters. The results show that the inclusion of binaries in stellar population models may lead to obvious change in the determination of some parameters of early-type galaxies and therefore it is potentially important for spectral studies. In particular, the ages of young components of composite stellar populations become much older when using binary star population models instead of single star population models. This implies that binary star population models will measure significantly different star formation histories for early-type galaxies compared to single star population models. In addition, stellar population models with binary interactions on average measure larger dust extinctions than single star population models. This suggests that when binary star population models are used, negative extinctions are possibly no longer necessary in the spectral fitting of galaxies (see previous works, e.g., Cid Fernandes et al. for comparison). Furthermore, it is shown that optical spectra have strong constraints on stellar age while UV spectra have strong constraints on binary fraction. Finally, our results suggest that binary star population models can provide new insight into the stellar properties of globular clusters

Spectral domain optical coherence tomography imaging of subretinal bands associated with chronic retinal detachments

OpenAIRE

Kothari, Nikisha; Kuriyan, Ajay E; Flynn, Harry W

2016-01-01

Nikisha Kothari, Ajay E Kuriyan, Harry W Flynn JrDepartment of Ophthalmology, Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami, Miami, FL, USAAbstract: We report three patients with subretinal bands associated with retinal detachment in chronic retinal detachments who underwent successful retinal reattachment. Subretinal bands before and after surgery can be identified on clinical examination and spectral domain optical coherence tomography. Removal of subr...

Optical Coherence Tomography-Based Decision Making in Exudative Age-related Macular Degeneration: Comparison of Time- versus Spectral-Domain Devices

Science.gov (United States)

Cukras, Catherine; Wang, Yunqing D.; Meyerle, Catherine B.; Forooghian, Farzin; Chew, Emily Y.; Wong, Wai T.

2010-01-01

Purpose To determine if optical coherence tomography (OCT) device-type influences clinical grading of OCT imaging in the context of exudative age-related macular degeneration (AMD). Methods Ninety-six paired OCT scans from 49 patients with active exudative AMD were obtained on both the time-domain Stratus™ OCT system and the spectral-domain Cirrus™ OCT system at the same visit. Three independent graders judged each scan for the presence of intraretinal fluid (IRF) or subretinal fluid (SRF). The degree of grader consensus was evaluated and the ability of the systems to detect the presence of disease activity was analyzed. Results Cirrus™ OCT generated a higher degree of inter-grader consensus than Stratus OCT with higher intraclass correlation coefficients (ICC) for all parameters analyzed. A pair-wise comparison of Cirrus™ OCT to Stratus™ OCT systems revealed that Cirrus™-based gradings more frequently reported the presence of SRF and IRF and detected overall neovascular activity at a higher rate (p<0.05) compared to Stratus™-based gradings Conclusions The choice of time-domain (Stratus™) versus spectra-domain (Cirrus™) OCT systems has a measurable impact on clinical decision making in exudative AMD. Spectral-domain OCT systems may be able to generate more consensus in clinical interpretation and, in particular cases, detect disease activity not detected by time-domain systems. Clinical trials employing OCT-based clinical evaluations of exudative AMD may need to account for these inter-system differences in planning and analysis. PMID:19696804

From spectral holeburning memory to spatial-spectral microwave signal processing

International Nuclear Information System (INIS)

Babbitt, Wm Randall; Barber, Zeb W; Harrington, Calvin; Mohan, R Krishna; Sharpe, Tia; Bekker, Scott H; Chase, Michael D; Merkel, Kristian D; Stiffler, Colton R; Traxinger, Aaron S; Woidtke, Alex J

2014-01-01

Many storage and processing systems based on spectral holeburning have been proposed that access the broad bandwidth and high dynamic range of spatial-spectral materials, but only recently have practical systems been developed that exceed the performance and functional capabilities of electronic devices. This paper reviews the history of the proposed applications of spectral holeburning and spatial-spectral materials, from frequency domain optical memory to microwave photonic signal processing systems. The recent results of a 20 GHz bandwidth high performance spectrum monitoring system with the additional capability of broadband direction finding demonstrates the potential for spatial-spectral systems to be the practical choice for solving demanding signal processing problems in the near future. (paper)

Information content in spectral dependencies of optical unit volume parameters under action of He-Ne laser on blood

Science.gov (United States)

Khairullina, Alphiya Y.; Oleinik, Tatiana V.

1995-01-01

Our previous works concerned with the development of methods for studying blood and action of low-intensity laser radiation on blood and erythrocyte suspensions had shown the light- scattering methods gave a large body of information on a medium studied due to the methodological relationship between irradiation processes and techniques for investigations. Detail analysis of spectral diffuse reflectivities and transmissivities of optically thick blood layers, spectral absorptivities calculated on this basis over 600 - 900 nm, by using different approximations, for a pathological state owing to hypoxia testifies to the optical significance of not only hemoglobin derivatives but also products of hemoglobin decomposition. Laser action on blood is specific and related to an initial state of blood absorption due to different composition of chromoproteids. This work gives the interpretation of spectral observations. Analysis of spectral dependencies of the exinction coefficient e, mean cosine m of phase function, and parameter Q equals (epsilon) (1-(mu) )H/(lambda) (H - hematocrit) testifies to decreasing the relative index of refraction of erythrocytes and to morphological changes during laser action under pathology owing to hypoxia. The possibility to obtain physical and chemical information on the state of blood under laser action in vivo is shown to be based on the method proposed by us for calculating multilayered structures modeling human organs and on the technical implementation of this method.

Spectral BRDF measurements of metallic samples for laser processing applications

International Nuclear Information System (INIS)

Vitali, L; Fustinoni, D; Gramazio, P; Niro, A

2015-01-01

The spectral bidirectional reflectance distribution function (BRDF) of metals plays an important role in industrial processing involving laser-surface interaction. In particular, in laser metal machining, absorbance is strongly dependent on the radiation incidence angle as well as on finishing and contamination grade of the surface, and in turn it can considerably affect processing results. Very recently, laser radiation is also used to structure metallic surfaces, in order to produce many particular optical effects, ranging from a high level polishing to angular color shifting. Of course, full knowledge of the spectral BRDF of these structured layers makes it possible to infer reflectance or color for any irradiation and viewing angles. In this paper, we present Vis-NIR spectral BRDF measurements of laser-polished metallic, opaque, flat samples commonly employed in such applications. The resulting optical properties seem to be dependent on the atmospheric composition during the polishing process in addition to the roughness. The measurements are carried out with a Perkin Elmer Lambda 950 double-beam spectrophotometer, equipped with the Absolute Reflectance/Transmittance Analyzer (ARTA) motorized goniometer. (paper)

The effect of silver on the optical, spectral-luminescent, and crystallization properties of bromide photo-thermo-refractive glasses

Science.gov (United States)

Oreshkina, K. V.; Dubrovin, V. D.; Ignat'ev, A. I.; Nikonorov, N. V.

2017-10-01

The effect of silver on the optical, spectral-luminescent, and crystallization properties of bromide photo-thermo-refractive glasses is studied. Multicomponent photosensitive glasses of the Na2O-ZnO-Al2O3-SiO2 system with photosensitizing agents (cerium, antimony, silver) and halogenides (fluorine and bromine) are synthesized. Ultraviolet irradiation and thermal treatment below the glass-transition temperature of the glasses cause the formation of silver molecular clusters, which exhibit luminescence in the visible and infrared regions. UV irradiation and thermal treatment of glasses above the glass-transition temperature lead to the growth of silver nanoparticles with plasmon resonance peak in the region of 420 nm. Further thermal treatment of glasses above the glass-transition temperature shifts the plasmon-resonance maximum by 70 nm to longer wavelengths, which is related to the growth of a crystalline shell consisting of mixed silver and sodium bromides on nanoparticles. This formation of a crystalline phase on colloidal centers results in a local increase in the refractive index of the irradiated region by +Δ n 900 ppm compared to the nonirradiated region. Photo-thermo-refractive glasses with increased silver concentration are promising photosensitive materials for creating holographic optical elements and devices for line narrowing and stabilizing filters, spectral beam combiners, and filters for increasing the spectral brightness of laser diodes. A positive change in the refractive index of Photo-thermo-refractive glasses provides the possibility of recording in them 3D waveguide and integrated-optical structures.

NEW OPTICAL/ULTRAVIOLET COUNTERPARTS AND THE SPECTRAL ENERGY DISTRIBUTIONS OF NEARBY, THERMALLY EMITTING, ISOLATED NEUTRON STARS

International Nuclear Information System (INIS)

Kaplan, D. L.; Kamble, A.; Van Kerkwijk, M. H.; Ho, W. C. G.

2011-01-01

We present Hubble Space Telescope optical and ultraviolet photometry for five nearby, thermally emitting neutron stars. With these measurements, all seven such objects have confirmed optical and ultraviolet counterparts. Combining our data with archival space-based photometry, we present spectral energy distributions for all sources and measure the 'optical excess': the factor by which the measured photometry exceeds that extrapolated from X-ray spectra. We find that the majority have optical and ultraviolet fluxes that are inconsistent with that expected from thermal (Rayleigh-Jeans) emission, exhibiting more flux at longer wavelengths. We also find that most objects have optical excesses between 5 and 12, but that one object (RX J2143.0+0654) exceeds the X-ray extrapolation by a factor of more than 50 at 5000 A, and that this is robust to uncertainties in the X-ray spectra and absorption. We consider explanations for this ranging from atmospheric effects, magnetospheric emission, and resonant scattering, but find that none is satisfactory.

Opto-mechanical design of the MTG FCI spectral separation assembly

Science.gov (United States)

Riguet, François; Brousse, Emmanuel; Carel, Jean-Louis; Cottenye, Justine; Harmann, David; Joncour, Marc; Makhlouf, Houssine; Mouricaud, Daniel; Oussalah, Meihdi; Rodolfo, Jacques

2015-09-01

The Spectral Separation Assembly is a key component of the Flexible Combined Imager, an instrument that will be on-board Meteosat Third Generation. It splits the input beam coming from the telescope into five spectral groups, for a total of 16 channels, from 0.4 to 13.3 μm. It comprises a set of four dichroics separators followed by four collimating optics for the infrared spectral groups, which feed the cold imaging optics. The visible spectral group is directly imaged on a detector. This paper presents the optical design of the assembly, the mechanical mounting of the optical components, and the coatings developed for the dichroics, mirrors and lenses.

Eddy covariance measurements with a new fast-response, enclosed-path analyzer: Spectral characteristics and cross-system comparisons

Science.gov (United States)

K. Novick; J. Walker; W.S. Chan; A. Schmidt; C. Sobek; J.M. Vose

2013-01-01

A new class of enclosed path gas analyzers suitable for eddy covariance applications combines the advantages of traditional closed-path systems (small density corrections, good performance in poor weather) and open-path systems (good spectral response, low power requirements), and permits estimates of instantaneous gas mixing ratio. Here, the extent to which these...

The optical + infrared L dwarf spectral sequence of young planetary-mass objects in the Upper Scorpius association

Science.gov (United States)

Lodieu, N.; Zapatero Osorio, M. R.; Béjar, V. J. S.; Peña Ramírez, K.

2018-01-01

We present the results of photometric and spectroscopic follow-ups of the lowest mass member candidates in the nearest OB association, Upper Scorpius (∼5-10 Myr; 145 ± 17 pc), with the Gran Telescopio de Canarias (GTC) and European Southern Observatory (ESO) Very Large Telescope (VLT). We confirm the membership of the large majority (>80 per cent) of candidates originally selected photometrically and astrometrically based on their spectroscopic features, weak equivalent widths of gravity-sensitive doublets and radial velocities. Confirmed members follow a sequence over a wide magnitude range (J = 17.0-19.3 mag) in several colour-magnitude diagrams with optical, near- and mid-infrared photometry and have near-infrared spectral types in the L1-L7 interval with likely masses below 15 Jupiter masses. We find that optical spectral types tend to be earlier than near-infrared spectral types by a few subclasses for spectral types later than M9. We investigate the behaviour of spectral indices, defined in the literature as a function of spectral type and gravity, by comparison with values reported in the literature for young and old dwarfs. We also derive effective temperatures in the 1900-1600 K range from fits of synthetic model-atmosphere spectra to the observed photometry, but we caution that the procedure carries large uncertainties. We determine bolometric corrections for young L dwarfs with ages of ∼5-10 Myr (Upper Sco association) and find them to be similar in the J band but larger by 0.1-0.4 mag in the K band with respect to field L dwarfs. Finally, we discover two faint young L dwarfs, Visible and Infrared Survey Telescope for Astronomy (VISTA) J1607-2146 (L4.5) and VISTA J1611-2215 (L5), that have Hα emission and possible flux excesses at 4.5 μm, pointing to the presence of accretion from a disc on to the central objects of mass below ∼15MJup at an age of 5-10 Myr.

Three-dimensional, time-resolved profiling of ferroelectric domain wall dynamics by spectral-domain optical coherence tomography

International Nuclear Information System (INIS)

Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M.; Kirsten, Lars; Cimalla, Peter; Koch, Edmund

2017-01-01

We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Three-dimensional, time-resolved profiling of ferroelectric domain wall dynamics by spectral-domain optical coherence tomography

Energy Technology Data Exchange (ETDEWEB)

Haussmann, Alexander; Schmidt, Sebastian; Wehmeier, Lukas; Eng, Lukas M. [Technische Universitaet Dresden, Institute of Applied Physics and Center for Advancing Electronics Dresden (cfaed), Dresden (Germany); Kirsten, Lars; Cimalla, Peter; Koch, Edmund [Technische Universitaet Dresden, Faculty of Medicine Carl Gustav Carus, Anesthesiology and Intensive Care Medicine, Clinical Sensoring and Monitoring, Dresden (Germany)

2017-08-15

We apply here spectral-domain optical coherence tomography (SD-OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium-doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ∝ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3-dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs' polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD-OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high-speed SD-OCT setup for the real-time DW tracking upon ferroelectric domain switching under high external fields. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Optically trapped atomic resonant devices for narrow linewidth spectral imaging

Science.gov (United States)

Qian, Lipeng

This thesis focuses on the development of atomic resonant devices for spectroscopic applications. The primary emphasis is on the imaging properties of optically thick atomic resonant fluorescent filters and their applications. In addition, this thesis presents a new concept for producing very narrow linewidth light as from an atomic vapor lamp pumped by a nanosecond pulse system. This research was motivated by application for missile warning system, and presents an innovative approach to a wide angle, ultra narrow linewidth imaging filter using a potassium vapor cell. The approach is to image onto and collect the fluorescent photons emitted from the surface of an optically thick potassium vapor cell, generating a 2 GHz pass-band imaging filter. This linewidth is narrow enough to fall within a Fraunhefer dark zone in the solar spectrum, thus make the detection solar blind. Experiments are conducted to measure the absorption line shape of the potassium resonant filter, the quantum efficiency of the fluorescent behavior, and the resolution of the fluorescent image. Fluorescent images with different spatial frequency components are analyzed by using a discrete Fourier transform, and the imaging capability of the fluorescent filter is described by its Modulation Transfer Function. For the detection of radiation that is spectrally broader than the linewidth of the potassium imaging filter, the fluorescent image is seen to be blurred by diffuse fluorescence from the slightly off resonant photons. To correct this, an ultra-thin potassium imaging filter is developed and characterized. The imaging property of the ultra-thin potassium imaging cell is tested with a potassium seeded flame, yielding a resolution image of ˜ 20 lines per mm. The physics behind the atomic resonant fluorescent filter is radiation trapping. The diffusion process of the resonant photons trapped in the atomic vapor is theoretically described in this thesis. A Monte Carlo method is used to simulate the

Giant magneto-optical faraday effect in HgTe thin films in the terahertz spectral range.

Science.gov (United States)

Shuvaev, A M; Astakhov, G V; Pimenov, A; Brüne, C; Buhmann, H; Molenkamp, L W

2011-03-11

We report the observation of a giant Faraday effect, using terahertz (THz) spectroscopy on epitaxial HgTe thin films at room temperature. The effect is caused by the combination of the unique band structure and the very high electron mobility of HgTe. Our observations suggest that HgTe is a high-potential material for applications as optical isolator and modulator in the THz spectral range.

Information-efficient spectral imaging sensor

Science.gov (United States)

Sweatt, William C.; Gentry, Stephen M.; Boye, Clinton A.; Grotbeck, Carter L.; Stallard, Brian R.; Descour, Michael R.

2003-01-01

A programmable optical filter for use in multispectral and hyperspectral imaging. The filter splits the light collected by an optical telescope into two channels for each of the pixels in a row in a scanned image, one channel to handle the positive elements of a spectral basis filter and one for the negative elements of the spectral basis filter. Each channel for each pixel disperses its light into n spectral bins, with the light in each bin being attenuated in accordance with the value of the associated positive or negative element of the spectral basis vector. The spectral basis vector is constructed so that its positive elements emphasize the presence of a target and its negative elements emphasize the presence of the constituents of the background of the imaged scene. The attenuated light in the channels is re-imaged onto separate detectors for each pixel and then the signals from the detectors are combined to give an indication of the presence or not of the target in each pixel of the scanned scene. This system provides for a very efficient optical determination of the presence of the target, as opposed to the very data intensive data manipulations that are required in conventional hyperspectral imaging systems.

Meeting the Cool Neighbors. XII. An Optically Anchored Analysis of the Near-infrared Spectra of L Dwarfs

Science.gov (United States)

Cruz, Kelle L.; Núñez, Alejandro; Burgasser, Adam J.; Abrahams, Ellianna; Rice, Emily L.; Reid, I. Neill; Looper, Dagny

2018-01-01

Discrepancies between competing optical and near-infrared (NIR) spectral typing systems for L dwarfs have motivated us to search for a classification scheme that ties the optical and NIR schemes together, and addresses complexities in the spectral morphology. We use new and extant optical and NIR spectra to compile a sample of 171 L dwarfs, including 27 low-gravity β and γ objects, with spectral coverage from 0.6–2.4 μm. We present 155 new low-resolution NIR spectra and 19 new optical spectra. We utilize a method for analyzing NIR spectra that partially removes the broad-band spectral slope and reveals similarities in the absorption features between objects of the same optical spectral type. Using the optical spectra as an anchor, we generate near-infrared spectral average templates for L0–L8, L0–L4γ, and L0–L1β type dwarfs. These templates reveal that NIR spectral morphologies are correlated with the optical types. They also show the range of spectral morphologies spanned by each spectral type. We compare low-gravity and field-gravity templates to provide recommendations on the minimum required observations for credibly classifying low-gravity spectra using low-resolution NIR data. We use the templates to evaluate the existing NIR spectral standards and propose new ones where appropriate. Finally, we build on the work of Kirkpatrick et al. to provide a spectral typing method that is tied to the optical and can be used when only H or K band data are available. The methods we present here provide resolutions to several long-standing issues with classifying L dwarf spectra and could also be the foundation for a spectral classification scheme for cloudy exoplanets.

Performance analysis of spectral-phase-encoded optical code-division multiple-access system regarding the incorrectly decoded signal as a nonstationary random process

Science.gov (United States)

Yan, Meng; Yao, Minyu; Zhang, Hongming

2005-11-01

The performance of a spectral-phase-encoded (SPE) optical code-division multiple-access (OCDMA) system is analyzed. Regarding the incorrectly decoded signal (IDS) as a nonstationary random process, we derive a novel probability distribution for it. The probability distribution of the IDS is considered a chi-squared distribution with degrees of freedom r=1, which is more reasonable and accurate than in previous work. The bit error rate (BER) of an SPE OCDMA system under multiple-access interference is evaluated. Numerical results show that the system can sustain very low BER even when there are multiple simultaneous users, and as the code length becomes longer or the initial pulse becomes shorter, the system performs better.

A scalable, self-analyzing digital locking system for use on quantum optics experiments.

Science.gov (United States)

Sparkes, B M; Chrzanowski, H M; Parrain, D P; Buchler, B C; Lam, P K; Symul, T

2011-07-01

Digital control of optics experiments has many advantages over analog control systems, specifically in terms of the scalability, cost, flexibility, and the integration of system information into one location. We present a digital control system, freely available for download online, specifically designed for quantum optics experiments that allows for automatic and sequential re-locking of optical components. We show how the inbuilt locking analysis tools, including a white-noise network analyzer, can be used to help optimize individual locks, and verify the long term stability of the digital system. Finally, we present an example of the benefits of digital locking for quantum optics by applying the code to a specific experiment used to characterize optical Schrödinger cat states.

Imaging of the iridocorneal angle with the RTVue spectral domain optical coherence tomography.

Science.gov (United States)

Perera, Shamira A; Ho, Ching Lin; Aung, Tin; Baskaran, Mani; Ho, Henrietta; Tun, Tin A; Lee, Tian Loon; Kumar, Rajesh S

2012-04-02

To determine the ability of the RTVue spectral domain optical coherence tomography (SDOCT) to image the anterior chamber angle (ACA). Consecutive subjects, recruited from glaucoma clinics, prospectively underwent ophthalmic evaluation including gonioscopy by an ophthalmologist and anterior chamber imaging with SDOCT, adapted with a corneal lens adapter (cornea anterior module-low magnification [CAM-L]) and anterior segment OCT (ASOCT), both performed by a technician. Two different ophthalmologists, masked to gonioscopy findings, assessed visualization of the scleral spur (SS), Schwalbe's line (SL), and trabecular meshwork (TM) by the two modalities. The ability to detect a closed angle was compared with gonioscopy. The average age (SD) of the 81 subjects enrolled was 64.1 (11.4) years; the majority were Chinese (91.4%) and female (61.7%). SDOCT images revealed the SS in 26.9% (56/324) of quadrants and the SL in 44.1% (143/324) of quadrants; in ASOCT images, the SS could be visualized in 69.1% (224/324) of quadrants (P gonioscopy. When analyzing the horizontal quadrants only, both modalities agreed well with gonioscopy, 0.75 and 0.74, respectively (AC1 statistics). The RTVue SDOCT allowed visualization of SL, TM, and SS. However, these landmarks were not detected in a large percentage of images.

Utilizing the ratio and the summation of two spectral lines for estimation of optical depth: Focus on thick plasmas

Science.gov (United States)

Rezaei, Fatemeh; Tavassoli, Seyed Hassan

2016-11-01

In this paper, a study is performed on the spectral lines of plasma radiations created from focusing of the Nd:YAG laser on Al standard alloys at atmospheric air pressure. A new theoretical method is presented to investigate the evolution of the optical depth of the plasma based on the radiative transfer equation, in LTE condition. This work relies on the Boltzmann distribution, lines broadening equations, and as well as the self-absorption relation. Then, an experimental set-up is devised to extract some of plasma parameters such as temperature from modified line ratio analysis, electron density from Stark broadening mechanism, line intensities of two spectral lines in the same order of ionization from similar species, and the plasma length from the shadowgraphy section. In this method, the summation and the ratio of two spectral lines are considered for evaluation of the temporal variations of the plasma parameters in a LIBS homogeneous plasma. The main advantage of this method is that it comprises the both of thin and thick laser induced plasmas without straight calculation of self-absorption coefficient. Moreover, the presented model can also be utilized for evaluation the transition of plasma from the thin condition to the thick one. The results illustrated that by measuring the line intensities of two spectral lines at different evolution times, the plasma cooling and the growth of the optical depth can be followed.

Prevalence of Split Nerve Fiber Layer Bundles in Healthy People Imaged with Spectral Domain Optical Coherence Tomography

Directory of Open Access Journals (Sweden)

Sirel Gür Güngör

2016-12-01

Full Text Available Objectives: The presence of retinal nerve fiber layer (RNFL split bundles was recently described in normal eyes scanned using scanning laser polarimetry and by histologic studies. Split bundles may resemble RNFL loss in healthy eyes. The aim of our study was to determine the prevalence of nerve fiber layer split bundles in healthy people. Materials and Methods: We imaged 718 eyes of 359 healthy persons with the spectral domain optical coherence tomography in this cross-sectional study. All eyes had intraocular pressure of 21 mmHg or less, normal appearance of the optic nerve head, and normal visual fields (Humphrey Field Analyzer 24-2 full threshold program. In our study, a bundle was defined as ‘split’ when there is localized defect not resembling a wedge defect in the RNFL deviation map with a symmetrically divided RNFL appearance on the RNFL thickness map. The classification was performed by two independent observers who used an identical set of reference examples to standardize the classification. Results: Inter-observer consensus was reached in all cases. Bilateral superior split bundles were seen in 19 cases (5.29% and unilateral superior split was observed in 15 cases (4.16%. In 325 cases (90.52% there was no split bundle. Conclusion: Split nerve fiber layer bundles, in contrast to single nerve fiber layer bundles, are not common findings in healthy eyes. In eyes with normal optic disc appearance, especially when a superior RNFL defect is observed in RNFL deviation map, the RNLF thickness map and graphs should also be examined for split nerve fiber layer bundles.

Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

NARCIS (Netherlands)

Mokiem, MR; Martin-Hernandez, NL; Lenorzer, A; de Koter, A; Tielens, AGGA

We present a systematic study of the effect of metallicity on the stellar spectral energy distribution (SED) of 0 main sequence (dwarf) stars, focussing on the hydrogen and helium ionizing continua, and on the optical and near-IR lines used for spectral classification. The spectra are based on

Metallicity and the spectral energy distribution and spectral types of dwarf O-stars

NARCIS (Netherlands)

Mokiem, M.R.; Martín-Hernández, N.L.; Lenorzer, A.; de Koter, A.; Tielens, A.G.G.M.

2004-01-01

We present a systematic study of the effect of metallicity on the stellar spectral energy distribution (SED) of O main sequence (dwarf) stars, focussing on the hydrogen and helium ionizing continua, and on the optical and near-IR lines used for spectral classification. The spectra are based on

Brillouin Scattering Spectrum Analysis Based on Auto-Regressive Spectral Estimation

Science.gov (United States)

Huang, Mengyun; Li, Wei; Liu, Zhangyun; Cheng, Linghao; Guan, Bai-Ou

2018-06-01

Auto-regressive (AR) spectral estimation technology is proposed to analyze the Brillouin scattering spectrum in Brillouin optical time-domain refelectometry. It shows that AR based method can reliably estimate the Brillouin frequency shift with an accuracy much better than fast Fourier transform (FFT) based methods provided the data length is not too short. It enables about 3 times improvement over FFT at a moderate spatial resolution.

Brillouin Scattering Spectrum Analysis Based on Auto-Regressive Spectral Estimation

Science.gov (United States)

Huang, Mengyun; Li, Wei; Liu, Zhangyun; Cheng, Linghao; Guan, Bai-Ou

2018-03-01

Auto-regressive (AR) spectral estimation technology is proposed to analyze the Brillouin scattering spectrum in Brillouin optical time-domain refelectometry. It shows that AR based method can reliably estimate the Brillouin frequency shift with an accuracy much better than fast Fourier transform (FFT) based methods provided the data length is not too short. It enables about 3 times improvement over FFT at a moderate spatial resolution.

Automated 3-D method for the correction of axial artifacts in spectral-domain optical coherence tomography images

NARCIS (Netherlands)

B. Antony (Bhavna); M.D. Abràmoff (Michael); L. Tang (Li); W.D. Ramdas (Wishal); J.R. Vingerling (Hans); N.M. Jansonius (Nomdo); K. Lee (Kyungmoo); Y.H. Kwon (Young); M. Sonka (Milan); M.K. Garvin (Mona)

2011-01-01

textabstractThe 3-D spectral-domain optical coherence tomography (SD-OCT) images of the retina often do not reflect the true shape of the retina and are distorted differently along the x and y axes. In this paper, we propose a novel technique that uses thin-plate splines in two stages to estimate

MODIS Aqua Optical Throughput Degradation Impact on Relative Spectral Response and Calibration on Ocean Color Products

Science.gov (United States)

Lee, Shihyan; Meister, Gerhard

2017-01-01

Since Moderate Resolution Imaging Spectroradiometer Aqua's launch in 2002, the radiometric system gains of the reflective solar bands have been degrading, indicating changes in the systems optical throughput. To estimate the optical throughput degradation, the electronic gain changes were estimated and removed from the measured system gain. The derived optical throughput degradation shows a rate that is much faster in the shorter wavelengths than the longer wavelengths. The wavelength-dependent optical throughput degradation modulated the relative spectral response (RSR) of the bands. In addition, the optical degradation is also scan angle-dependent due to large changes in response versus the scan angle over time. We estimated the modulated RSR as a function of time and scan angles and its impacts on sensor radiometric calibration for the ocean science. Our results show that the calibration bias could be up to 1.8 % for band 8 (412 nm) due to its larger out-of-band response. For the other ocean bands, the calibration biases are much smaller with magnitudes at least one order smaller.

XOP: A graphical user interface for spectral calculations and x-ray optics utilities

International Nuclear Information System (INIS)

Dejus, R.J.; Sanchez del Rio, M.

1996-01-01

A graphical user interface, using the Interactive Data Language (IDL) widget toolkit, for calculation of spectral properties of synchrotron radiation sources and for interaction of x-rays with optical elements has been developed. The interface runs presently on three different computer architectures under the Unix operating system endash the Sun-OS, the HP-UX, and the DEC-Unix operating systems. The point-and-click interface is used as a driver program for a variety of codes from different authors written in different computer languages. The execution of codes for calculating synchrotron radiation from undulators, wigglers, and bending magnets is summarized. The computation of optical properties of materials and the x-ray diffraction profiles from crystals in different geometries are also discussed. The interface largely simplifies the use of these codes and may be used without prior knowledge of how to run a particular program. copyright 1996 American Institute of Physics

Application and analysis of performance of dqpsk advanced modulation format in spectral amplitude coding ocdma

International Nuclear Information System (INIS)

Memon, A.

2015-01-01

SAC (Spectral Amplitude Coding) is a technique of OCDMA (Optical Code Division Multiple Access) to encode and decode data bits by utilizing spectral components of the broadband source. Usually OOK (ON-Off-Keying) modulation format is used in this encoding scheme. To make SAC OCDMA network spectrally efficient, advanced modulation format of DQPSK (Differential Quaternary Phase Shift Keying) is applied, simulated and analyzed, m-sequence code is encoded in the simulated setup. Performance regarding various lengths of m-sequence code is also analyzed and displayed in the pictorial form. The results of the simulation are evaluated with the help of electrical constellation diagram, eye diagram and bit error rate graph. All the graphs indicate better transmission quality in case of advanced modulation format of DQPSK used in SAC OCDMA network as compared with OOK. (author)

Broadband semiconductor optical amplifiers of the spectral range 750 – 1100 nm

International Nuclear Information System (INIS)

Andreeva, E V; Il'chenko, S N; Lobintsov, A A; Shramenko, M V; Ladugin, M A; Marmalyuk, A A; Yakubovich, S D

2013-01-01

A line of travelling-wave semiconductor optical amplifiers (SOAs) based on heterostructures used for production of broadband superluminescent diodes is developed. The pure small-signal gains of the developed SOA modules are about 25 dB, while the gain bandwidths at a level of –10 dB reach 50 – 100 nm. As a whole, the SOA modules cover the IR spectral range from 750 to 1100 nm. The SOAs demonstrate a high reliability at a single-mode fibre-coupled cw output power up to 50 mW. Examples of application of two of the developed SOA modules as active elements of broadband fast-tunable lasers are presented. (lasers)

Broadband semiconductor optical amplifiers of the spectral range 750 – 1100 nm

Energy Technology Data Exchange (ETDEWEB)

Andreeva, E V; Il' chenko, S N; Lobintsov, A A; Shramenko, M V [Superlum Diodes Ltd., Moscow (Russian Federation); Ladugin, M A [' Sigm Plyus' Ltd, Moscow (Russian Federation); Marmalyuk, A A [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation); Yakubovich, S D [Moscow State Institute of Radio-Engineering, Electronics and Automation (Technical University), Moscow (Russian Federation)

2013-11-30

A line of travelling-wave semiconductor optical amplifiers (SOAs) based on heterostructures used for production of broadband superluminescent diodes is developed. The pure small-signal gains of the developed SOA modules are about 25 dB, while the gain bandwidths at a level of –10 dB reach 50 – 100 nm. As a whole, the SOA modules cover the IR spectral range from 750 to 1100 nm. The SOAs demonstrate a high reliability at a single-mode fibre-coupled cw output power up to 50 mW. Examples of application of two of the developed SOA modules as active elements of broadband fast-tunable lasers are presented. (lasers)

Automated 3-D method for the correction of axial artifacts in spectral-domain optical coherence tomography images

NARCIS (Netherlands)

Antony, Bhavna; Abramoff, Michael D.; Tang, Li; Ramdas, Wishal D.; Vingerling, Johannes R.; Jansonius, Nomdo M.; Lee, Kyungmoo; Kwon, Young H.; Sonka, Milan; Garvin, Mona K.

2011-01-01

The 3-D spectral-domain optical coherence tomography (SD-OCT) images of the retina often do not reflect the true shape of the retina and are distorted differently along the x and y axes. In this paper, we propose a novel technique that uses thin-plate splines in two stages to estimate and correct

Contributed Review: Absolute spectral radiance calibration of fiber-optic shock-temperature pyrometers using a coiled-coil irradiance standard lamp

Energy Technology Data Exchange (ETDEWEB)

Fat’yanov, O. V., E-mail: fatyan1@gps.caltech.edu; Asimow, P. D., E-mail: asimow@gps.caltech.edu [Division of Geological and Planetary Sciences 252-21, California Institute of Technology, Pasadena, California 91125 (United States)

2015-10-15

We describe an accurate and precise calibration procedure for multichannel optical pyrometers such as the 6-channel, 3-ns temporal resolution instrument used in the Caltech experimental geophysics laboratory. We begin with a review of calibration sources for shock temperatures in the 3000-30 000 K range. High-power, coiled tungsten halogen standards of spectral irradiance appear to be the only practical alternative to NIST-traceable tungsten ribbon lamps, which are no longer available with large enough calibrated area. However, non-uniform radiance complicates the use of such coiled lamps for reliable and reproducible calibration of pyrometers that employ imaging or relay optics. Careful analysis of documented methods of shock pyrometer calibration to coiled irradiance standard lamps shows that only one technique, not directly applicable in our case, is free of major radiometric errors. We provide a detailed description of the modified Caltech pyrometer instrument and a procedure for its absolute spectral radiance calibration, accurate to ±5%. We employ a designated central area of a 0.7× demagnified image of a coiled-coil tungsten halogen lamp filament, cross-calibrated against a NIST-traceable tungsten ribbon lamp. We give the results of the cross-calibration along with descriptions of the optical arrangement, data acquisition, and processing. We describe a procedure to characterize the difference between the static and dynamic response of amplified photodetectors, allowing time-dependent photodiode correction factors for spectral radiance histories from shock experiments. We validate correct operation of the modified Caltech pyrometer with actual shock temperature experiments on single-crystal NaCl and MgO and obtain very good agreement with the literature data for these substances. We conclude with a summary of the most essential requirements for error-free calibration of a fiber-optic shock-temperature pyrometer using a high-power coiled tungsten halogen

method for ranging and noise reduction of low coherence interferometry LCI and optical coherence tomography OCT signals by parallel detection of spectral bands

NARCIS (Netherlands)

Boer, JF De; Tearney, G. J.; Bouma, BE

2008-01-01

Apparatus and method for increasing the sensitivity in the detection of optical coherence tomography and loW coher ence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source is split

Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

Directory of Open Access Journals (Sweden)

V. E. Cachorro

2002-04-01

Full Text Available We report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company covering the range from 300–1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study.Key words. Atmospheric composition and structure (aerosols and particles; transmission and scattering of radiation; troposphere – composition and chemistry

Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

Directory of Open Access Journals (Sweden)

V. E. Cachorro

Full Text Available We report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company covering the range from 300–1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study.

Key words. Atmospheric composition and structure (aerosols and particles; transmission and scattering of radiation; troposphere – composition and chemistry

Multi-spectral confocal microendoscope for in-vivo imaging

Science.gov (United States)

Rouse, Andrew Robert

The concept of in-vivo multi-spectral confocal microscopy is introduced. A slit-scanning multi-spectral confocal microendoscope (MCME) was built to demonstrate the technique. The MCME employs a flexible fiber-optic catheter coupled to a custom built slit-scan confocal microscope fitted with a custom built imaging spectrometer. The catheter consists of a fiber-optic imaging bundle linked to a miniature objective and focus assembly. The design and performance of the miniature objective and focus assembly are discussed. The 3mm diameter catheter may be used on its own or routed though the instrument channel of a commercial endoscope. The confocal nature of the system provides optical sectioning with 3mum lateral resolution and 30mum axial resolution. The prism based multi-spectral detection assembly is typically configured to collect 30 spectral samples over the visible chromatic range. The spectral sampling rate varies from 4nm/pixel at 490nm to 8nm/pixel at 660nm and the minimum resolvable wavelength difference varies from 7nm to 18nm over the same spectral range. Each of these characteristics are primarily dictated by the dispersive power of the prism. The MCME is designed to examine cellular structures during optical biopsy and to exploit the diagnostic information contained within the spectral domain. The primary applications for the system include diagnosis of disease in the gastro-intestinal tract and female reproductive system. Recent data from the grayscale imaging mode are presented. Preliminary multi-spectral results from phantoms, cell cultures, and excised human tissue are presented to demonstrate the potential of in-vivo multi-spectral imaging.

Optical characterization of agricultural pest insects: a methodological study in the spectral and time domains

Science.gov (United States)

Li, Y. Y.; Zhang, H.; Duan, Z.; Lian, M.; Zhao, G. Y.; Sun, X. H.; Hu, J. D.; Gao, L. N.; Feng, H. Q.; Svanberg, S.

2016-08-01

Identification of agricultural pest insects is an important aspect in insect research and agricultural monitoring. We have performed a methodological study of how spectroscopic techniques and wing-beat frequency analysis might provide relevant information. An optical system based on the combination of close-range remote sensing and reflectance spectroscopy was developed to study the optical characteristics of different flying insects, collected in Southern China. The results demonstrate that the combination of wing-beat frequency assessment and reflectance spectral analysis has the potential to successfully differentiate between insect species. Further, studies of spectroscopic characteristics of fixed specimen of insects, also from Central China, showed the possibility of refined agricultural pest identification. Here, in addition to reflectance recordings also laser-induced fluorescence spectra were investigated for all the species of insects under study and found to provide complementary information to optically distinguish insects. In order to prove the practicality of the techniques explored, clearly fieldwork aiming at elucidating the variability of parameters, even within species, must be performed.

Aerosol spectral optical depths and size characteristics at a coastal industriallocation in India - effect of synoptic and mesoscale weather

Directory of Open Access Journals (Sweden)

K. Niranjan

2004-06-01

Full Text Available The aerosol spectral optical depths at ten discrete channels in the visible and near IR bands, obtained from a ground-based passive multi-wavelength solar radiometer at a coastal industrial location, Visakhapatnam, on the east coast of India, are used to study the response of the aerosol optical properties and size distributions to the changes in atmospheric humidity, wind speed and direction. It is observed that during high humidity conditions, the spectral optical depths show about 30% higher growth factors, and the size distributions show the generation of a typical new mode around 0.4 microns. The surface wind speed and direction also indicate the formation of new particles when the humid marine air mass interacts with the industrial air mass. This is interpreted in terms of new particle formation and subsequent particle growth by condensation and self-coagulation. The results obtained on the surface-size segregated aerosol mass distribution from a co-located Quartz Crystal Microbalance during different humidity conditions also show a large mass increase in the sub-micron size range with an increase in atmospheric humidity, indicating new particle formation at the sub-micron size range.

Investigation of retinal morphology alterations using spectral domain optical coherence tomography in a mouse model of retinal branch and central retinal vein occlusion.

Directory of Open Access Journals (Sweden)

Andreas Ebneter

Full Text Available Retinal vein occlusion is a leading cause of visual impairment. Experimental models of this condition based on laser photocoagulation of retinal veins have been described and extensively exploited in mammals and larger rodents such as the rat. However, few reports exist on the use of this paradigm in the mouse. The objective of this study was to investigate a model of branch and central retinal vein occlusion in the mouse and characterize in vivo longitudinal retinal morphology alterations using spectral domain optical coherence tomography. Retinal veins were experimentally occluded using laser photocoagulation after intravenous application of Rose Bengal, a photo-activator dye enhancing thrombus formation. Depending on the number of veins occluded, variable amounts of capillary dropout were seen on fluorescein angiography. Vascular endothelial growth factor levels were markedly elevated early and peaked at day one. Retinal thickness measurements with spectral domain optical coherence tomography showed significant swelling (p<0.001 compared to baseline, followed by gradual thinning plateauing two weeks after the experimental intervention (p<0.001. Histological findings at day seven correlated with spectral domain optical coherence tomography imaging. The inner layers were predominantly affected by degeneration with the outer nuclear layer and the photoreceptor outer segments largely preserved. The application of this retinal vein occlusion model in the mouse carries several advantages over its use in other larger species, such as access to a vast range of genetically modified animals. Retinal changes after experimental retinal vein occlusion in this mouse model can be non-invasively quantified by spectral domain optical coherence tomography, and may be used to monitor effects of potential therapeutic interventions.

Potential of remote sensing of cirrus optical thickness by airborne spectral radiance measurements at different sideward viewing angles

Science.gov (United States)

Wolf, Kevin; Ehrlich, André; Hüneke, Tilman; Pfeilsticker, Klaus; Werner, Frank; Wirth, Martin; Wendisch, Manfred

2017-03-01

Spectral radiance measurements collected in nadir and sideward viewing directions by two airborne passive solar remote sensing instruments, the Spectral Modular Airborne Radiation measurement sysTem (SMART) and the Differential Optical Absorption Spectrometer (mini-DOAS), are used to compare the remote sensing results of cirrus optical thickness τ. The comparison is based on a sensitivity study using radiative transfer simulations (RTS) and on data obtained during three airborne field campaigns: the North Atlantic Rainfall VALidation (NARVAL) mission, the Mid-Latitude Cirrus Experiment (ML-CIRRUS) and the Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems (ACRIDICON) campaign. Radiative transfer simulations are used to quantify the sensitivity of measured upward radiance I with respect to τ, ice crystal effective radius reff, viewing angle of the sensor θV, spectral surface albedo α, and ice crystal shape. From the calculations it is concluded that sideward viewing measurements are generally better suited than radiance data from the nadir direction to retrieve τ of optically thin cirrus, especially at wavelengths larger than λ = 900 nm. Using sideward instead of nadir-directed spectral radiance measurements significantly improves the sensitivity and accuracy in retrieving τ, in particular for optically thin cirrus of τ ≤ 2. The comparison of retrievals of τ based on nadir and sideward viewing radiance measurements from SMART, mini-DOAS and independent estimates of τ from an additional active remote sensing instrument, the Water Vapor Lidar Experiment in Space (WALES), shows general agreement within the range of measurement uncertainties. For the selected example a mean τ of 0.54 ± 0.2 is derived from SMART, and 0.49 ± 0.2 by mini-DOAS nadir channels, while WALES obtained a mean value of τ = 0.32 ± 0.02 at 532 nm wavelength, respectively. The mean of τ derived from the sideward viewing mini

Spectral Characteristics of Young Stars Associated with the Sh2-296 Nebula

Science.gov (United States)

Fernandes, Beatriz; Gregorio-Hetem, Jane

Aiming to contribute to the understanding of star formation and evolution in the Canis Major (CMa R1) Molecular Clouds Complex, we analyze the spectral characteristics of a population of young stars associated with the arc-shaped nebula Sh2-296. Our XMM/Newton observations detected 109 X-ray sources in the region and optical spectroscopy was performed with Gemini telescope for 85 optical counterparts. We identified and characterized 51 objects that present features typically found in young objects, such as Hα emission and strong absorption on the Li I line.

Dynamic virtual optical network embedding in spectral and spatial domains over elastic optical networks with multicore fibers

Science.gov (United States)

Zhu, Ruijie; Zhao, Yongli; Yang, Hui; Tan, Yuanlong; Chen, Haoran; Zhang, Jie; Jue, Jason P.

2016-08-01

Network virtualization can eradicate the ossification of the infrastructure and stimulate innovation of new network architectures and applications. Elastic optical networks (EONs) are ideal substrate networks for provisioning flexible virtual optical network (VON) services. However, as network traffic continues to increase exponentially, the capacity of EONs will reach the physical limitation soon. To further increase network flexibility and capacity, the concept of EONs is extended into the spatial domain. How to map the VON onto substrate networks by thoroughly using the spectral and spatial resources is extremely important. This process is called VON embedding (VONE).Considering the two kinds of resources at the same time during the embedding process, we propose two VONE algorithms, the adjacent link embedding algorithm (ALEA) and the remote link embedding algorithm (RLEA). First, we introduce a model to solve the VONE problem. Then we design the embedding ability measurement of network elements. Based on the network elements' embedding ability, two VONE algorithms were proposed. Simulation results show that the proposed VONE algorithms could achieve better performance than the baseline algorithm in terms of blocking probability and revenue-to-cost ratio.

Polarization diversity scheme on spectral polarization coding optical code-division multiple-access network

Science.gov (United States)

Yen, Chih-Ta; Huang, Jen-Fa; Chang, Yao-Tang; Chen, Bo-Hau

2010-12-01

We present an experiment demonstrating the spectral-polarization coding optical code-division multiple-access system introduced with a nonideal state of polarization (SOP) matching conditions. In the proposed system, the encoding and double balanced-detection processes are implemented using a polarization-diversity scheme. Because of the quasiorthogonality of Hadamard codes combining with array waveguide grating routers and a polarization beam splitter, the proposed codec pair can encode-decode multiple code words of Hadamard code while retaining the ability for multiple-access interference cancellation. The experimental results demonstrate that when the system is maintained with an orthogonal SOP for each user, an effective reduction in the phase-induced intensity noise is obtained. The analytical SNR values are found to overstate the experimental results by around 2 dB when the received effective power is large. This is mainly limited by insertion losses of components and a nonflattened optical light source. Furthermore, the matching conditions can be improved by decreasing nonideal influences.

Solar radio bursts of spectral type II, coronal shocks, and optical coronal transients

Science.gov (United States)

Maxwell, A.; Dryer, M.

1981-01-01

An examination is presented of the association of solar radio bursts of spectral type II and coronal shocks with solar flare ejecta observed in H-alpha, the green coronal line, and white-light coronagraphs. It is suggested that fast-moving optical coronal transients should for the most part be identified with piston-type phenomena well behind the outward-traveling shock waves that generate type II radio bursts. A general model is presented which relates type II radio bursts and coronal shocks to optically observed ejecta and consists of three main velocity regimes: (1) a quasi-hemispherical shock wave moving outward from the flare at speeds of 1000-2000 km/sec and Alfven Mach number of about 1.5; (2) the velocity of the piston driving the shock, on the order of 0.8 that of the shock; and (3) the regime of the slower-moving H-alpha ejecta, with velocities of 300-500 km/sec.

Piecewise spectrally band-pass for compressive coded aperture spectral imaging

International Nuclear Information System (INIS)

Qian Lu-Lu; Lü Qun-Bo; Huang Min; Xiang Li-Bin

2015-01-01

Coded aperture snapshot spectral imaging (CASSI) has been discussed in recent years. It has the remarkable advantages of high optical throughput, snapshot imaging, etc. The entire spatial-spectral data-cube can be reconstructed with just a single two-dimensional (2D) compressive sensing measurement. On the other hand, for less spectrally sparse scenes, the insufficiency of sparse sampling and aliasing in spatial-spectral images reduce the accuracy of reconstructed three-dimensional (3D) spectral cube. To solve this problem, this paper extends the improved CASSI. A band-pass filter array is mounted on the coded mask, and then the first image plane is divided into some continuous spectral sub-band areas. The entire 3D spectral cube could be captured by the relative movement between the object and the instrument. The principle analysis and imaging simulation are presented. Compared with peak signal-to-noise ratio (PSNR) and the information entropy of the reconstructed images at different numbers of spectral sub-band areas, the reconstructed 3D spectral cube reveals an observable improvement in the reconstruction fidelity, with an increase in the number of the sub-bands and a simultaneous decrease in the number of spectral channels of each sub-band. (paper)

Diagonal Eigenvalue Unity (DEU) code for spectral amplitude coding-optical code division multiple access

Science.gov (United States)

Ahmed, Hassan Yousif; Nisar, K. S.

2013-08-01

Code with ideal in-phase cross correlation (CC) and practical code length to support high number of users are required in spectral amplitude coding-optical code division multiple access (SAC-OCDMA) systems. SAC systems are getting more attractive in the field of OCDMA because of its ability to eliminate the influence of multiple access interference (MAI) and also suppress the effect of phase induced intensity noise (PIIN). In this paper, we have proposed new Diagonal Eigenvalue Unity (DEU) code families with ideal in-phase CC based on Jordan block matrix with simple algebraic ways. Four sets of DEU code families based on the code weight W and number of users N for the combination (even, even), (even, odd), (odd, odd) and (odd, even) are constructed. This combination gives DEU code more flexibility in selection of code weight and number of users. These features made this code a compelling candidate for future optical communication systems. Numerical results show that the proposed DEU system outperforms reported codes. In addition, simulation results taken from a commercial optical systems simulator, Virtual Photonic Instrument (VPI™) shown that, using point to multipoint transmission in passive optical network (PON), DEU has better performance and could support long span with high data rate.

Fabrication of the polarization independent spectral beam combining grating

Science.gov (United States)

Liu, Quan; Jin, Yunxia; Wu, Jianhong; Guo, Peiliang

2016-03-01

Owing to damage, thermal issues, and nonlinear optical effects, the output power of fiber laser has been proven to be limited. Beam combining techniques are the attractive solutions to achieve high-power high-brightness fiber laser output. The spectral beam combining (SBC) is a promising method to achieve high average power output without influencing the beam quality. A polarization independent spectral beam combining grating is one of the key elements in the SBC. In this paper the diffraction efficiency of the grating is investigated by rigorous coupled-wave analysis (RCWA). The theoretical -1st order diffraction efficiency of the grating is more than 95% from 1010nm to 1080nm for both TE and TM polarizations. The fabrication tolerance is analyzed. The polarization independent spectral beam combining grating with the period of 1.04μm has been fabricated by holographic lithography - ion beam etching, which are within the fabrication tolerance.

Spectral map-analysis: a method to analyze gene expression data

OpenAIRE

Bijnens, Luc J.M.; Lewi, Paul J.; Göhlmann, Hinrich W.; Molenberghs, Geert; Wouters, Luc

2004-01-01

bioinformatics; biplot; correspondence factor analysis; data mining; data visualization; gene expression data; microarray data; multivariate exploratory data analysis; principal component analysis; Spectral map analysis

En face spectral domain optical coherence tomography analysis of lamellar macular holes.

Science.gov (United States)

Clamp, Michael F; Wilkes, Geoff; Leis, Laura S; McDonald, H Richard; Johnson, Robert N; Jumper, J Michael; Fu, Arthur D; Cunningham, Emmett T; Stewart, Paul J; Haug, Sara J; Lujan, Brandon J

2014-07-01

To analyze the anatomical characteristics of lamellar macular holes using cross-sectional and en face spectral domain optical coherence tomography. Forty-two lamellar macular holes were retrospectively identified for analysis. The location, cross-sectional length, and area of lamellar holes were measured using B-scans and en face imaging. The presence of photoreceptor inner segment/outer segment disruption and the presence or absence of epiretinal membrane formation were recorded. Forty-two lamellar macular holes were identified. Intraretinal splitting occurred within the outer plexiform layer in 97.6% of eyes. The area of intraretinal splitting in lamellar holes did not correlate with visual acuity. Eyes with inner segment/outer segment disruption had significantly worse mean logMAR visual acuity (0.363 ± 0.169; Snellen = 20/46) than in eyes without inner segment/outer segment disruption (0.203 ± 0.124; Snellen = 20/32) (analysis of variance, P = 0.004). Epiretinal membrane was present in 34 of 42 eyes (81.0%). En face imaging allowed for consistent detection and quantification of intraretinal splitting within the outer plexiform layer in patients with lamellar macular holes, supporting the notion that an area of anatomical weakness exists within Henle's fiber layer, presumably at the synaptic connection of these fibers within the outer plexiform layer. However, the en face area of intraretinal splitting did not correlate with visual acuity, disruption of the inner segment/outer segment junction was associated with significantly worse visual acuity in patients with lamellar macular holes.

Nanolaser spectroscopy and micro-optical resonators for detecting, analyzing, and manipulating bioparticles

Science.gov (United States)

Gourley, Paul L

2012-06-26

This invention provides a new method for rapidly analyzing single bioparticles to assess their material condition and state of health. The method is enabled by use of a resonant cavity apparatus to measure an optical property related to the bioparticle size and refractive index. Measuring the refractive index is useful for determining material properties of the bioparticle. The material properties depend on the biomolecular composition of the bioparticle. The biomolecular composition is, in turn, dependent on the state of health of the bioparticle. Thus, measured optical properties can be used to differentiate normal (healthy) and abnormal (diseased) states of bioparticles derived from cells or tissues. The method is illustrated with data obtained from a resonator with a gain medium. The invention also provides new methods for making multiple measurements in a single device and detecting, analyzing, and manipulating bioparticles that are much smaller than the wavelength of light.

Application and Analysis of Performance of DQPSK Advanced Modulation Format in Spectral Amplitude Coding OCDMA

Directory of Open Access Journals (Sweden)

Abdul Latif Memon

2014-04-01

Full Text Available SAC (Spectral Amplitude Coding is a technique of OCDMA (Optical Code Division Multiple Access to encode and decode data bits by utilizing spectral components of the broadband source. Usually OOK (ON-Off-Keying modulation format is used in this encoding scheme. To make SAC OCDMA network spectrally efficient, advanced modulation format of DQPSK (Differential Quaternary Phase Shift Keying is applied, simulated and analyzed. m-sequence code is encoded in the simulated setup. Performance regarding various lengths of m-sequence code is also analyzed and displayed in the pictorial form. The results of the simulation are evaluated with the help of electrical constellation diagram, eye diagram and bit error rate graph. All the graphs indicate better transmission quality in case of advanced modulation format of DQPSK used in SAC OCDMA network as compared with OOK

A differential detection scheme of spectral shifts in long-period fiber gratings

Science.gov (United States)

Zhelyazkova, Katerina; Eftimov, Tinko; Smietana, Mateusz; Bock, Wojtek

2010-10-01

In this work we present an analysis of the response of a compact, simple and inexpensive optoelectronic sensor system intended to detect spectral shifts of a long-period fiber grating (LPG). The system makes use of a diffraction grating and a couple of receiving optical fibers that pick up signals at two different wavelengths. This differential detection system provides the same useful information from an LPG-based sensor as with a conventional laboratory system using optical spectrum analyzers for monitoring the minimum offset of LPG. The design of the fiber detection pair as a function of the parameters of the dispersion grating, the pick-up fiber and the LPG parameters, is presented in detail. Simulation of the detection system responses is presented using real from spectral shifts in nano-coated LPGs caused by the evaporation of various liquids such as water, ethanol and acetone, which are examples of corrosive, flammable and hazardous substances. Fiber optic sensors with similar detection can find applications in structural health monitoring for moisture detection, monitoring the spillage of toxic and flammable substances in industry etc.

Development of procedures for spectrometer brand Spectral Products to capture spectra of incoherent optical radiation for the Laboratorio de Fotonica y Tecnologia Laser Aplicada

International Nuclear Information System (INIS)

Arias Avendano, Fabio Andres

2008-01-01

The procedure to capture spectra of incoherent optical radiation for the Laboratorio de Fotonica y Tecnologia Laser Aplicada (LAFTLA), of the Escuela de Ingenieria Electrica de la Universidad de Costa Rica is developed through the use of a spectrometer brand Spectral Products. The thorough understanding of manuals spectrometer brand Spectral Products was necessary for the satisfactory development of the project. Spectrometer and the card National Instruments are installed and run both devices with a montage of suitable laboratory. Two catches of spectrum for two different sources of optical radiation are performanced, since damages to the files .ddl precluded that the SM 240 spectrometer worked properly to take more catches to other sources of optical radiation. A final report containing the two catches is produced with the respective analysis. (author) [es

Magnetorefractive effect in manganites with a colossal magnetoresistance in the visible spectral region

International Nuclear Information System (INIS)

Sukhorukov, Yu. P.; Telegin, A. V.; Granovsky, A. B.; Gan’shina, E. A.; Zhukov, A.; Gonzalez, J.; Herranz, G.; Caicedo, J. M.; Yurasov, A. N.; Bessonov, V. D.; Kaul’, A. R.; Gorbenko, O. Yu.; Korsakov, I. E.

2012-01-01

The magnetotransmission, magnetoreflection, and magnetoresistance of the La 0.7 Ca 0.3 MnO 3 and La 0.9 Ag 0.1 MnO 3 epitaxial films have been investigated. It has been found that the films exhibit a significant magnetorefractive effect in the case of reflection and transmission of light in the fundamental absorption region both in the vicinity of the Curie temperature and at low temperatures. It has been shown that the magnetorefractive effect in the infrared spectral region of the manganites is determined by a high-frequency response to magnetoresistance, whereas the magnetorefractive effect in the visible spectral region of these materials is associated with a change in the electronic structure in response to a magnetic field, which, in turn, leads to a change in the electron density of states, the probability of interband optical transitions, and the shift of light absorption bands. The obtained values of the magnetotransmittance and magnetoreflectance in the visible spectral region are less than those observed in the infrared region of the spectrum, but they are several times greater than the linear magneto-optical effects. As a result, the magnetorefractive effect, which is a nongyrotropic phenomenon, makes it possible to avoid the use of light analyzers and polarizers in optical circuits.

Measurements of stimulated-Raman-scattering-induced tilt in spectral-amplitude-coding optical code-division multiple-access systems

Science.gov (United States)

Al-Qazwini, Zaineb A. T.; Abdullah, Mohamad K.; Mokhtar, Makhfudzah B.

2009-01-01

We measure the stimulated Raman scattering (SRS)-induced tilt in spectral-amplitude-coding optical code-division multiple-access (SAC-OCDMA) systems as a function of system main parameters (transmission distance, power per chip, and number of users) via computer simulations. The results show that SRS-induced tilt significantly increases as transmission distance, power per chip, or number of users grows.

Analysis of optical proprieties of the water reservoir Rodolfo Costa e Silva – Itaara, RS, Brazil, with field spectral data and orbital multispectral images

Directory of Open Access Journals (Sweden)

Waterloo Pereira Filho

2007-08-01

Full Text Available An evaluation of the discrimination of water classes using continuum removal technique applied over spectral data obtained in field and multispectral images classification is presented. The study area was the Rodolfo Costa e Silva water reservoir, located in central region of Rio Grande do Sul (RS State, in Southern region of Brazil. The methodology was based on in situ data collection of: total suspended solids, chlorophyll (a, b and c, water transparency, and bidirectional spectral reflectance. These data were collected in 21 point (samples in May 16, 2006. The continuum removal technique was applied on the spectral data over 4 absorption bands: 400-550nm, 610-640nm, 650-680nm e 580-700nm. The continuum removal parameters analyzed for each absorption band were: depth, area and width. The multispectral images used were CBERS-2/CCD and Landsat 5/TM. The images were acquired in a date nearest to field work and with appropriate weather conditions. These images were corrected by removing atmospheric effects and then classified. According to the results obtained from the continuum removal technique, it was verified that band depth, area and width did not present a good potential to separate different water classes. Digital classification results did not show significant correlations with the limnological parameters collected in field and, therefore, could not be used to characterize spectrally different water classes or compartments. The main problem of establishing relationships between spectral reflectance and water quality parameters was due to the low variability of optical components in the water of Rodolfo Costa e Silva Reservoir. In this case the spectral analyses (considering both techniques were not sensitive to the relative small variations observed in field data.

Synthesis, XRD, TEM, EPR, and Optical Absorption Spectral Studies of CuZnO2 Nanocompound

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T. Ravindra Reddy

2014-01-01

Full Text Available Synthesis of nano CuZnO2 compound is carried out by thermal decomposition method. The crystalline phase of the material is characterized by XRD. The calculated unit cell constants are a=3.1 Å and c=3.4786 Å and are of tetragonal structure. The unit cell constants are different from wurtzite (hexagonal which indicate that a nanocompound is formed. Further TEM images reveal that the metal ion is in tetragonal structure with oxygen ligands. The prepared CuZnO2 is then characterized for crystallite size analysis by employing transmission electron microscopy (TEM. The size is found to be 100 nm. Uniform bright rings are noticed in the TEM picture suggesting that the nanocrystals have preferential instead of random orientations. The selected-area electron diffraction (SAED pattern clearly indicates the formation of CuO-ZnO nanocompound. The nature of bonding is studied by electron paramagnetic resonance (EPR. The covalency character is about 0.74 and thus the compound is electrically less conductive. Optical absorption spectral studies suggest that Cu(II is placed in tetragonal elongation crystal field. The spin-orbit coupling constant, λ, is calculated using the EPR and optical absorption spectral results suggest some covalent bond between metal and ligand. Near infrared (NIR spectra are due to hydroxyl and water fundamentals.

Spectral Domain Optical Coherence Tomography Findings in Posterior Microphthalmia

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Emine Tınkır Kayıtmazbatır

2014-05-01

Full Text Available The retinal spectral domain optical coherence tomography (SD-OCT findings of two posterior microphthalmia cases are presented in this case report. For this purpose, the findings of two siblings aged five and seven years who presented to our clinic with the complain of far-sightedness and high hypermetropia were evaluated. Both cases diagnosed to have posterior microphthalmia demonstrated normal biomicroscopic anterior segment examination and gonioscopy findings and the axial lengths were measured to be shorter than 17mm. The SD-OCT analysis of papillomacular folds detected in fundus examination revealed contribution of only neurosensorial retina. Beneath the retinal fold, we observed bilateral cysts in the intraretinal area in one of the cases and a triangle-shaped hyporeflective space with an apex corresponding to that of the retinal fold in the subretinal area in both cases. SD-OCT is an adjunctive imaging tool for diagnosis and follow-up of degenerative changes in posterior microphthalmia. These changes may be also important for visual prognosis. (Turk J Ophthalmol 2014; 44: 240-2

Epsilon-Q: An Automated Analyzer Interface for Mass Spectral Library Search and Label-Free Protein Quantification.

Science.gov (United States)

Cho, Jin-Young; Lee, Hyoung-Joo; Jeong, Seul-Ki; Paik, Young-Ki

2017-12-01

Mass spectrometry (MS) is a widely used proteome analysis tool for biomedical science. In an MS-based bottom-up proteomic approach to protein identification, sequence database (DB) searching has been routinely used because of its simplicity and convenience. However, searching a sequence DB with multiple variable modification options can increase processing time, false-positive errors in large and complicated MS data sets. Spectral library searching is an alternative solution, avoiding the limitations of sequence DB searching and allowing the detection of more peptides with high sensitivity. Unfortunately, this technique has less proteome coverage, resulting in limitations in the detection of novel and whole peptide sequences in biological samples. To solve these problems, we previously developed the "Combo-Spec Search" method, which uses manually multiple references and simulated spectral library searching to analyze whole proteomes in a biological sample. In this study, we have developed a new analytical interface tool called "Epsilon-Q" to enhance the functions of both the Combo-Spec Search method and label-free protein quantification. Epsilon-Q performs automatically multiple spectral library searching, class-specific false-discovery rate control, and result integration. It has a user-friendly graphical interface and demonstrates good performance in identifying and quantifying proteins by supporting standard MS data formats and spectrum-to-spectrum matching powered by SpectraST. Furthermore, when the Epsilon-Q interface is combined with the Combo-Spec search method, called the Epsilon-Q system, it shows a synergistic function by outperforming other sequence DB search engines for identifying and quantifying low-abundance proteins in biological samples. The Epsilon-Q system can be a versatile tool for comparative proteome analysis based on multiple spectral libraries and label-free quantification.

Development of spectral analysis math models and software program and spectral analyzer, digital converter interface equipment design

Science.gov (United States)

Hayden, W. L.; Robinson, L. H.

1972-01-01

Spectral analyses of angle-modulated communication systems is studied by: (1) performing a literature survey of candidate power spectrum computational techniques, determining the computational requirements, and formulating a mathematical model satisfying these requirements; (2) implementing the model on UNIVAC 1230 digital computer as the Spectral Analysis Program (SAP); and (3) developing the hardware specifications for a data acquisition system which will acquire an input modulating signal for SAP. The SAP computational technique uses extended fast Fourier transform and represents a generalized approach for simple and complex modulating signals.

High spectral efficiency optical CDMA system based on guard-time and optical hard-limiting (OHL)

Energy Technology Data Exchange (ETDEWEB)

Gagliardi, R M; Bennett, C V; Mendez, A J; Hernandez, V J; Lennon, W J

2003-12-02

Optical code-division multiple access (OCDMA) is an interesting subject of research because of its potential to support asynchronous, bursty communications. OCDMA has been investigated for local area networks, access networks, and, more recently, as a packet label for emerging networks. Two-dimensional (2-D) OCDMA codes are preferred in current research because of the flexibility of designing the codes and their higher cardinality and spectral efficiency (SE) compared with direct sequence codes based on on-off keying and intensity modulation/direct detection, and because they lend themselves to being implemented with devices developed for wavelength-division-multiplexed (WDM) transmission (the 2-D codes typically combine wavelength and time as the two dimensions of the codes). This paper shows rigorously that 2-D wavelength/time codes have better SE than one-dimensional (1-D) CDMA/WDM combinations (of the same cardinality). Then, the paper describes a specific set of wavelength/time (W/T) codes and their implementation. These 2-D codes are high performance because they simultaneously have high cardinality (/spl Gt/10), per-user high bandwidth (>1 Gb/s), and high SE (>0.10 b/s/Hz). The physical implementation of these W/T codes is described and their performance evaluated by system simulations and measurements on an OCDMA technology demonstrator. This research shows that OCDMA implementation complexity (e.g., incorporating double hard-limiting and interference estimation) can be avoided by using a guard time in the codes and an optical hard limiter in the receiver.

Spectral encoding method for measuring the relative arrival time between x-ray/optical pulses

International Nuclear Information System (INIS)

Bionta, M. R.; Hartmann, N.; Weaver, M.; French, D.; Glownia, J. M.; Bostedt, C.; Chollet, M.; Ding, Y.; Fritz, D. M.; Fry, A. R.; Krzywinski, J.; Lemke, H. T.; Messerschmidt, M.; Schorb, S.; Zhu, D.; White, W. E.; Nicholson, D. J.; Cryan, J. P.; Baker, K.; Kane, D. J.

2014-01-01

The advent of few femtosecond x-ray light sources brings promise of x-ray/optical pump-probe experiments that can measure chemical and structural changes in the 10–100 fs time regime. Widely distributed timing systems used at x-ray Free-Electron Laser facilities are typically limited to above 50 fs fwhm jitter in active x-ray/optical synchronization. The approach of single-shot timing measurements is used to sort results in the event processing stage. This has seen wide use to accommodate the insufficient precision of active stabilization schemes. In this article, we review the current technique for “measure-and-sort” at the Linac Coherent Light Source at the SLAC National Accelerator Laboratory. The relative arrival time between an x-ray pulse and an optical pulse is measured near the experimental interaction region as a spectrally encoded cross-correlation signal. The cross-correlation provides a time-stamp for filter-and-sort algorithms used for real-time sorting. Sub-10 fs rms resolution is common in this technique, placing timing precision at the same scale as the duration of the shortest achievable x-ray pulses

Noncoherent Spectral Optical CDMA System Using 1D Active Weight Two-Code Keying Codes

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Bih-Chyun Yeh

2016-01-01

Full Text Available We propose a new family of one-dimensional (1D active weight two-code keying (TCK in spectral amplitude coding (SAC optical code division multiple access (OCDMA networks. We use encoding and decoding transfer functions to operate the 1D active weight TCK. The proposed structure includes an optical line terminal (OLT and optical network units (ONUs to produce the encoding and decoding codes of the proposed OLT and ONUs, respectively. The proposed ONU uses the modified cross-correlation to remove interferences from other simultaneous users, that is, the multiuser interference (MUI. When the phase-induced intensity noise (PIIN is the most important noise, the modified cross-correlation suppresses the PIIN. In the numerical results, we find that the bit error rate (BER for the proposed system using the 1D active weight TCK codes outperforms that for two other systems using the 1D M-Seq codes and 1D balanced incomplete block design (BIBD codes. The effective source power for the proposed system can achieve −10 dBm, which has less power than that for the other systems.

Adjustment of a goniometer for X-rays optics calibration in the spectral range 1.5-20 KeV

International Nuclear Information System (INIS)

Legistre, S.

1992-10-01

The aim of this memoir is the adjustment of a (θ, 2θ) goniometer coupled to X-rays source to calibrate mirrors (single layers like C, Ni, Au, etc... and multilayers like C/W, Si/W, etc...) in the spectral range 1.5 - 20 keV. For each kind of tested optics the adjustment of the goniometer include the procedure alignment of the different components (X-ray source, collimation slits, optics, detectors) and the first reflectivity measurements. Those measurements are compared those realized at LURE, using synchrotron radiation provided by SUPER ACO storage ring, and to a theoretical simulation

Adaptive optics parallel spectral domain optical coherence tomography for imaging the living retina

Science.gov (United States)

Zhang, Yan; Rha, Jungtae; Jonnal, Ravi S.; Miller, Donald T.

2005-06-01

Although optical coherence tomography (OCT) can axially resolve and detect reflections from individual cells, there are no reports of imaging cells in the living human retina using OCT. To supplement the axial resolution and sensitivity of OCT with the necessary lateral resolution and speed, we developed a novel spectral domain OCT (SD-OCT) camera based on a free-space parallel illumination architecture and equipped with adaptive optics (AO). Conventional flood illumination, also with AO, was integrated into the camera and provided confirmation of the focus position in the retina with an accuracy of ±10.3 μm. Short bursts of narrow B-scans (100x560 μm) of the living retina were subsequently acquired at 500 Hz during dynamic compensation (up to 14 Hz) that successfully corrected the most significant ocular aberrations across a dilated 6 mm pupil. Camera sensitivity (up to 94 dB) was sufficient for observing reflections from essentially all neural layers of the retina. Signal-to-noise of the detected reflection from the photoreceptor layer was highly sensitive to the level of cular aberrations and defocus with changes of 11.4 and 13.1 dB (single pass) observed when the ocular aberrations (astigmatism, 3rd order and higher) were corrected and when the focus was shifted by 200 μm (0.54 diopters) in the retina, respectively. The 3D resolution of the B-scans (3.0x3.0x5.7 μm) is the highest reported to date in the living human eye and was sufficient to observe the interface between the inner and outer segments of individual photoreceptor cells, resolved in both lateral and axial dimensions. However, high contrast speckle, which is intrinsic to OCT, was present throughout the AO parallel SD-OCT B-scans and obstructed correlating retinal reflections to cell-sized retinal structures.

Three dimensional tracking for volumetric spectral-domain optical coherence tomography.

Science.gov (United States)

Maguluri, Gopi; Mujat, Mircea; Park, B H; Kim, K H; Sun, Wei; Iftimia, N V; Ferguson, R D; Hammer, Daniel X; Chen, Teresa C; de Boer, Johannes F

2007-12-10

We present a three-dimensional (3D) tracker for a clinical ophthalmic spectral domain optical coherence tomography (SD-OCT) system that combines depth-tracking with lateral tracking, providing a stabilized reference frame for 3D data recording and post acquisition analysis. The depth-tracking system is implemented through a real-time dynamic feedback mechanism to compensate for motion artifact in the axial direction. Active monitoring of the retina and adapting the reference arm of the interferometer allowed the whole thickness of the retina to be stabilized to within +/-100 mum. We achieve a relatively constant SNR from image to image by stabilizing the image of the retina with respect to the depth dependent sensitivity of SD-OCT. The depth tracking range of our system is 5.2 mm in air and the depth is adjusted every frame.nhancement in the stability of the images with the depth-tracking algorithm is demonstrated on a healthy volunteer.

Reflectivity and thickness analysis of epiretinal membranes using spectral-domain optical coherence tomography

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Ajay E. Kuriyan

2016-01-01

Full Text Available AIM: To compare thickness and reflectivity spectral domain optical coherence tomography (SD-OCT findings in patients with idiopathic epiretinal membranes (ERMs, before and after ERM peeling surgery, with normal controls. METHODS: A retrospective study analyzed SD-OCTs of eyes with ERMs undergoing ERM peeling surgery by one surgeon from 2008 to 2010 and normal control eyes. SD-OCTs were analyzed using a customized algorithm to measure reflectivity and thickness. The relationship between the SD-OCT findings and best corrected visual acuity (BCVA outcomes was also studied. RESULTS: Thirty-four ERM eyes and 12 normal eyes were identified. Preoperative eyes had high reflectivity and thickness of the group of layers from the internal limiting membrane (ILM to the retinal pigment epithelium (RPE and the group of layers from the ILM to the external limiting membrane (ELM. The values of reflectivity of these two groups of layers decreased postoperatively, but were still higher than normal eyes. In contrast, preoperative eyes had lower reflectivity of two 10×15 pixel regions of interest (ROIs incorporating: 1 ELM + outer nuclear layer (ONL and 2 photoreceptor layer (PRL + RPE, compared to controls. The values of reflectivity of these ROIs increased postoperatively, but were still lower than normal controls. A larger improvement in BCVA postoperatively was correlated with a greater degree of abnormal preoperative reflectivity and thickness findings. CONCLUSION: Quantitative differences in reflectivity and thickness between preoperative, postoperative, and normal SD-OCTs allow assessment of changes in the retina secondary to ERM. Our study identified hyperreflective inner retina changes and hyporeflective outer retina changes in patients with ERMs. SD-OCT quantitative measures of reflectivity and/or thickness of specific groups of retinal layers and/or ROIs correlate with improvement in BCVA.

Novel concepts in near-field optics: from magnetic near-field to optical forces

Science.gov (United States)

Yang, Honghua

Driven by the progress in nanotechnology, imaging and spectroscopy tools with nanometer spatial resolution are needed for in situ material characterizations. Near-field optics provides a unique way to selectively excite and detect elementary electronic and vibrational interactions at the nanometer scale, through interactions of light with matter in the near-field region. This dissertation discusses the development and applications of near-field optical imaging techniques, including plasmonic material characterization, optical spectral nano-imaging and magnetic field detection using scattering-type scanning near-field optical microscopy (s-SNOM), and exploring new modalities of optical spectroscopy based on optical gradient force detection. Firstly, the optical dielectric functions of one of the most common plasmonic materials---silver is measured with ellipsometry, and analyzed with the Drude model over a broad spectral range from visible to mid-infrared. This work was motivated by the conflicting results of previous measurements, and the need for accurate values for a wide range of applications of silver in plasmonics, optical antennas, and metamaterials. This measurement provides a reference for dielectric functions of silver used in metamaterials, plasmonics, and nanophotonics. Secondly, I implemented an infrared s-SNOM instrument for spectroscopic nano-imaging at both room temperature and low temperature. As one of the first cryogenic s-SNOM instruments, the novel design concept and key specifications are discussed. Initial low-temperature and high-temperature performances of the instrument are examined by imaging of optical conductivity of vanadium oxides (VO2 and V2O 3) across their phase transitions. The spectroscopic imaging capability is demonstrated on chemical vibrational resonances of Poly(methyl methacrylate) (PMMA) and other samples. The third part of this dissertation explores imaging of optical magnetic fields. As a proof-of-principle, the magnetic

Analysis of Few-Mode Multi-Core Fiber Splice Behavior Using an Optical Vector Network Analyzer

DEFF Research Database (Denmark)

Rommel, Simon; Mendinueta, Jose Manuel Delgado; Klaus, Werner

2017-01-01

The behavior of splices in a 3-mode 36-core fiber is analyzed using optical vector network analysis. Time-domain response analysis confirms splices may cause significant mode-mixing, while frequency-domain analysis shows splices may affect system level mode-dependent loss both positively and negativ......The behavior of splices in a 3-mode 36-core fiber is analyzed using optical vector network analysis. Time-domain response analysis confirms splices may cause significant mode-mixing, while frequency-domain analysis shows splices may affect system level mode-dependent loss both positively...

Reducing BER of spectral-amplitude coding optical code-division multiple-access systems by single photodiode detection technique

Science.gov (United States)

Al-Khafaji, H. M. R.; Aljunid, S. A.; Amphawan, A.; Fadhil, H. A.; Safar, A. M.

2013-03-01

In this paper, we present a single photodiode detection (SPD) technique for spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. The proposed technique eliminates both phase-induced intensity noise (PIIN) and multiple-access interference (MAI) in the optical domain. Analytical results show that for 35 simultaneous users transmitting at data rate of 622 Mbps, the bit-error rate (BER) = 1.4x10^-28 for SPD technique is much better compared to 9.3x10^-6 and 9.6x10^-3 for the modified-AND as well as the AND detection techniques, respectively. Moreover, we verified the improved performance afforded by the proposed technique using data transmission simulations.

CLASSIFICATION AND QUANTITATIVE ANALYSIS OF GEOGRAPHIC ATROPHY JUNCTIONAL ZONE USING SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

Science.gov (United States)

Qu, Jinfeng; Velaga, Swetha Bindu; Hariri, Amir H; Nittala, Muneeswar Gupta; Sadda, Srinivas

2017-08-22

The junctional zone at the border of areas of geographic atrophy (GA) in eyes with nonneovascular age-related macular degeneration is an important target region for future therapeutic strategies. The goal of this study was to perform a detailed classification and quantitative characterization of the junctional zone using spectral domain optical coherence tomography. Spectral domain optical coherence tomography volume cube scans (Spectralis OCT, 1024 × 37, Automatic Real Time > 9) were obtained from 15 eyes of 11 patients with GA because of nonneovascular age-related macular degeneration. Volume optical coherence tomography data were imported into previously described validated grading software (3D-OCTOR), and manual segmentation of the retinal pigment epithelium (RPE) and photoreceptor layers was performed on all B-scans (total of 555). Retinal pigment epithelium and photoreceptor defect maps were produced for each case. The borders of the photoreceptor defect area and RPE defect area were delineated individually on separate annotation layers. The two outlines were then superimposed to compare the areas of overlap and nonoverlap. The perimeter of the RPE defect area was calculated by the software in pixels. The superimposed outline of the photoreceptor defect area and the RPE defect area was scrutinized to classify the overlap configuration of the junctional zone into one of three categories: Type 0, exact correspondence between the edge of the RPE defect and photoreceptor defect; Type 1, loss of photoreceptors outside and beyond the edge of the RPE defect; Type 2, preservation of photoreceptors beyond the edge of the RPE defect. The relative proportion of the various border configurations was expressed as a percentage of the perimeter of the RPE defect. Each configuration was then classified into four subgroups according to irregularity of the RPE band and the presence of debris. Fifteen eyes of 11 patients (mean age: 79.3 ± 4.3 years; range: 79-94 years) were

Magnetorefractive effect in manganites with a colossal magnetoresistance in the visible spectral region

Energy Technology Data Exchange (ETDEWEB)

Sukhorukov, Yu. P., E-mail: suhorukov@imp.uran.ru; Telegin, A. V. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Granovsky, A. B., E-mail: granov@magn.ru; Gan' shina, E. A. [Moscow State University, Faculty of Physics (Russian Federation); Zhukov, A.; Gonzalez, J. [Universidad del Pais Vasco (UPV)/Euskal Herriko Unibertsitatea (EHU), Departamento de Fisica de Materiales, Facultad de Quimica (Spain); Herranz, G. [Institut de Ciencia de Materials de Barcelona (ICMAB)-CSIC (Spain); Caicedo, J. M. [Universidad del Pais Vasco (UPV)/Euskal Herriko Unibertsitatea (EHU), Departamento de Fisica de Materiales, Facultad de Quimica (Spain); Yurasov, A. N. [Moscow State Institute of Radio-Engineering, Electronics, and Automation (Technical University) (Russian Federation); Bessonov, V. D. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Kaul' , A. R.; Gorbenko, O. Yu.; Korsakov, I. E. [Moscow State University, Faculty of Physics (Russian Federation)

2012-01-15

The magnetotransmission, magnetoreflection, and magnetoresistance of the La{sub 0.7}Ca{sub 0.3}MnO{sub 3} and La{sub 0.9}Ag{sub 0.1}MnO{sub 3} epitaxial films have been investigated. It has been found that the films exhibit a significant magnetorefractive effect in the case of reflection and transmission of light in the fundamental absorption region both in the vicinity of the Curie temperature and at low temperatures. It has been shown that the magnetorefractive effect in the infrared spectral region of the manganites is determined by a high-frequency response to magnetoresistance, whereas the magnetorefractive effect in the visible spectral region of these materials is associated with a change in the electronic structure in response to a magnetic field, which, in turn, leads to a change in the electron density of states, the probability of interband optical transitions, and the shift of light absorption bands. The obtained values of the magnetotransmittance and magnetoreflectance in the visible spectral region are less than those observed in the infrared region of the spectrum, but they are several times greater than the linear magneto-optical effects. As a result, the magnetorefractive effect, which is a nongyrotropic phenomenon, makes it possible to avoid the use of light analyzers and polarizers in optical circuits.

Label swapper device for spectral amplitude coded optical packet networks monolithically integrated on InP.

Science.gov (United States)

Muñoz, P; García-Olcina, R; Habib, C; Chen, L R; Leijtens, X J M; de Vries, T; Robbins, D; Capmany, J

2011-07-04

In this paper the design, fabrication and experimental characterization of an spectral amplitude coded (SAC) optical label swapper monolithically integrated on Indium Phosphide (InP) is presented. The device has a footprint of 4.8x1.5 mm2 and is able to perform label swapping operations required in SAC at a speed of 155 Mbps. The device was manufactured in InP using a multiple purpose generic integration scheme. Compared to previous SAC label swapper demonstrations, using discrete component assembly, this label swapper chip operates two order of magnitudes faster.

Enhanced spectral domain optical coherence tomography for pathological and functional studies

Science.gov (United States)

Yuan, Zhijia

Optical coherence tomography (OCT) is a novel technique that enables noninvasive or minimally invasive, cross-sectional imaging of biological tissue at sub-10mum spatial resolution and up to 2-3mm imaging depth. Numerous technological advances have emerged in recent years that have shown great potential to develop OCT into a powerful imaging and diagnostic tools. In particular, the implementation of Fourier-domain OCT (FDOCT) is a major step forward that leads to greatly improved imaging rate and image fidelity of OCT. This dissertation summarizes the work that focuses on enhancing the performances and functionalities of spectral radar based FDOCT (SDOCT) for pathological and functional applications. More specifically, chapters 1-4 emphasize on the development of SDOCT and its utility in pathological studies, including cancer diagnosis. The principle of SDOCT is first briefly outlined, followed by the design of our bench-top SDOCT systems with emphasis on spectral linear interpolation, calibration and system dispersion compensation. For ultrahigh-resolution SDOCT, time-lapse image registration and frame averaging is introduced to effectively reduce speckle noise and uncover subcellular details, showing great promise for enhancing the diagnosis of carcinoma in situ. To overcome the image depth limitation of OCT, a dual-modal imaging method combing SDOCT with high-frequency ultrasound is proposed and examined in animal cancer models to enhance the sensitivity and staging capabilities for bladder cancer diagnosis. Chapters 5-7 summarize the work on developing Doppler SDOCT for functional studies. Digital-frequency-ramping OCT (DFR-OCT) is developed in the study, which has demonstrated the ability to significantly improve the signal-to-noise ratio and thus sensitivity for retrieving subsurface blood flow imaging. New DFR algorithms and imaging processing methods are discussed to further enhance cortical CBF imaging. Applications of DFR-OCT for brain functional studies

Spectral Discrimination of Fine and Coarse Mode Aerosol Optical Depth from AERONET Direct Sun Data of Singapore and South-East Asia

Science.gov (United States)

Salinas Cortijo, S.; Chew, B.; Liew, S.

2009-12-01

Aerosol optical depth combined with the Angstrom exponent and its derivative, are often used as a qualitative indicator of aerosol particle size, with Angstrom exp. values greater than 2 indicating small (fine mode) particles associated with urban pollution and bio-mass burning. Around this region, forest fires are a regular occurrence during the dry season, specially near the large land masses of Sumatra and Borneo. The practice of clearing land by burning the primary and sometimes secondary forest, results in a smog-like haze covering large areas of regional cities such as cities Singapore, Kuala Lumpur and sometimes the south of Thailand, often reducing visibility and increasing health problems for the local population. In Singapore, the sources of aerosols are mostly from fossil fuel burning (energy stations, incinerators, urban transport etc.) and from the industrial and urban areas. The proximity to the sea adds a possible oceanic source. However, as stated above and depending on the time of the year, there can be a strong bio-mass component coming from forest fires from various regions of the neighboring countries. Bio-mass related aerosol particles are typically characterized by showing a large optical depth and small, sub-micron particle size distributions. In this work, we analyze three years of direct Sun measurements performed with a multi-channel Cimel Sun-Photometer (part of the AERONET network) located at our site. In order to identify bio-mass burning events in this region, we perform a spectral discrimination between coarse and fine mode optical depth; subsequently, the fine mode parameters such as optical depth, optical ratio and fine mode Angstrom exponents (and its derivative) are used to identify possible bio-mass related events within the data set.

WIDEFIELD SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY IMAGING OF PERIPHERAL ROUND RETINAL HOLES WITH OR WITHOUT RETINAL DETACHMENT.

Science.gov (United States)

Casswell, Edward J; Abou Ltaif, Sleiman; Carr, Thomas; Keane, Pearse A; Charteris, David G; Wickham, Louisa

2018-03-02

To describe the widefield spectral-domain optical coherence tomography features of peripheral round retinal holes, with or without associated retinal detachment (RD). Retrospective, observational study of 28 eyes with peripheral round retinal holes, with and without RD. Patients underwent imaging with a widefield 50-degree spectral-domain optical coherence tomography (Heidelberg Engineering, Germany) and Optos ultra-widefield imaging systems (Optos, United Kingdom). Vitreous attachment at the site of the retinal hole was detected in 27/28 (96.4%) cases. Cases were split into three groups: RHs with RD (n = 12); RHs with subretinal fluid (n = 5), and flat RHs (n = 11), with minimal or no subretinal fluid. 91.6% retinal holes associated with subretinal fluid or RD had vitreous attachment at the site of the hole. Eighty percent had vitreous attachment at both edges of the retinal hole, in a U-shape configuration, which appeared to exert traction. By contrast, flat retinal holes had visible vitreous attachment only at one edge of the retinal hole in 45.4%. Vitreous attachment was commonly seen at the site of round retinal holes. Vitreous attachment at both edges of the retinal hole in a U-shape configuration was more commonly seen at holes associated with subretinal fluid or RD.

3-D segmentation of retinal blood vessels in spectral-domain OCT volumes of the optic nerve head

Science.gov (United States)

Lee, Kyungmoo; Abràmoff, Michael D.; Niemeijer, Meindert; Garvin, Mona K.; Sonka, Milan

2010-03-01

Segmentation of retinal blood vessels can provide important information for detecting and tracking retinal vascular diseases including diabetic retinopathy, arterial hypertension, arteriosclerosis and retinopathy of prematurity (ROP). Many studies on 2-D segmentation of retinal blood vessels from a variety of medical images have been performed. However, 3-D segmentation of retinal blood vessels from spectral-domain optical coherence tomography (OCT) volumes, which is capable of providing geometrically accurate vessel models, to the best of our knowledge, has not been previously studied. The purpose of this study is to develop and evaluate a method that can automatically detect 3-D retinal blood vessels from spectral-domain OCT scans centered on the optic nerve head (ONH). The proposed method utilized a fast multiscale 3-D graph search to segment retinal surfaces as well as a triangular mesh-based 3-D graph search to detect retinal blood vessels. An experiment on 30 ONH-centered OCT scans (15 right eye scans and 15 left eye scans) from 15 subjects was performed, and the mean unsigned error in 3-D of the computer segmentations compared with the independent standard obtained from a retinal specialist was 3.4 +/- 2.5 voxels (0.10 +/- 0.07 mm).

Multichannel spectral mode of the ALOHA up-conversion interferometer

Science.gov (United States)

Lehmann, L.; Darré, P.; Boulogne, H.; Delage, L.; Grossard, L.; Reynaud, F.

2018-06-01

In this paper, we propose a multichannel spectral configuration of the Astronomical Light Optical Hybrid Analysis (ALOHA) instrument dedicated to high-resolution imaging. A frequency conversion process is implemented in each arm of an interferometer to transfer the astronomical light to a shorter wavelength domain. Exploiting the spectral selectivity of this non-linear optical process, we propose to use a set of independent pump lasers in order to simultaneously study multiple spectral channels. This principle is experimentally demonstrated with a dual-channel configuration as a proof-of-principle.

Concentric circular ring and nanodisk optical antenna enhanced multispectral quantum dot infrared photodetector with spectral localization

International Nuclear Information System (INIS)

Zhang, Yingjie; Kemsri, Thitikorn; Li, Lin; Lu, Xuejun; Gu, Guiru

2017-01-01

In this paper, we report a concentric circular ring and nanodisk plasmonic optical antenna (POA) enhanced multispectral quantum dot infrared photodetector (QDIP). The circular ring and the nanodisk POA structures are designed to have plasmonic resonant wavelengths in the longwave infrared (LWIR) and the midwave infrared (MWIR) spectral regimes, respectively. The electric field ( E -field) distributions are simulated and show spectral localization due to the distinct plasmonic resonant wavelengths of the POA structures. The circular ring is found to enhance the E -fields in the nanodisk regions due to the mutual coupling. A concentric circular ring and nanodisk POA enhanced multispectral QDIP was fabricated and tested. Multispectral enhancement was observed. The enhancement is compared to that of a QDIP with only the circular ring POA structure. The experiment data agree with the simulation. The concentric circular ring and nanodisk POA provides a compact planar structure for multispectral QDIP enhancement. (paper)

Normative data for macular thickness by high-definition spectral-domain optical coherence tomography (spectralis).

Science.gov (United States)

Grover, Sandeep; Murthy, Ravi K; Brar, Vikram S; Chalam, Kakarla V

2009-08-01

To establish normative data for the macular thickness by spectral-domain optical coherence tomography (SD-OCT) in subjects with no known retinal disease. Prospective, observational study in an academic institutional setting. Fifty subjects (age range, 20 to 84 years) with no known retinal disease, best-corrected visual acuity 20/20, and normal intraocular pressure were enrolled. The subjects were divided into 3 age groups: group 1 included subjects 20 to 40 years of age; group 2 included subjects 41 to 60 years of age; and group 3 included subjects 61 years of age and older. All subjects underwent a complete ophthalmologic examination to rule out any retinal diseases or glaucoma. All the OCT scans were performed by a single operator, and data obtained from the right eyes were analyzed by default, unless the right eye did not meet the inclusion criteria, and then data from left eyes were analyzed (n = 4). Central point thickness (CPT) and retinal thickness (RT) in 9 Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, including central subfield (CSF), were analyzed. Statistical analyses were carried out using the analysis of variance. Overall, the mean CPT was 227.3 +/- 23.2 microm, and mean CSF was 270.2 +/- 22.5 microm. Among the ETDRS subfields, the outer nasal quadrant had the maximum thickness (mean +/- standard deviation, 339.5 +/- 16.9 microm). The RT did not show significant difference with age (P = .62) or with gender (P = .1). However, there was a suggestion of significant difference in RT of Black subjects as compared with White subjects (P = .007) in the present study. Normative values for macular thickness in otherwise healthy eyes were measured to be 227.3 microm (CPT) and 270.2 microm (CSF) using commercially available Spectralis SD-OCT. Based on the data, the present study proposes the guidelines for normal CSF thickness to be 315 microm for future studies using macular thickness measurements with Spectralis SD-OCT (Heidelberg Engineering

The influence of temperature calibration on the OC–EC results from a dual-optics thermal carbon analyzer

Science.gov (United States)

The Sunset Laboratory Dual-Optical Carbonaceous Analyzer that simultaneously measures transmission and reflectance signals is widely used in thermal-optical analysis of particulate matter samples. Most often this instrument is used to measure total carbon (TC), organic carbon (O...

Aerosol Optical Properties in Southeast Asia From AERONET Observations

Science.gov (United States)

Eck, T. F.; Holben, B. N.; Boonjawat, J.; Le, H. V.; Schafer, J. S.; Reid, J. S.; Dubovik, O.; Smirnov, A.

2003-12-01

There is little published data available on measured optical properties of aerosols in the Southeast Asian region. The AERONET project and collaborators commenced monitoring of aerosol optical properties in February 2003 at four sites in Thailand and two sites in Viet Nam to measure the primarily anthropogenic aerosols generated by biomass burning and fossil fuel combustion/ industrial emissions. Automatic sun/sky radiometers at each site measured spectral aerosol optical depth in 7 wavelengths from 340 to 1020 nm and combined with directional radiances in the almucantar, retrievals were made of spectral single scattering albedo and aerosol size distributions. Angstrom exponents, size distributions and spectral single scattering albedo of primarily biomass burning aerosols at rural sites are compared to measurements made at AERONET sites in other major biomass burning regions in tropical southern Africa, South America, and in boreal forest regions. Additionally, the aerosol single scattering albedo and size distributions measured in Bangkok, Thailand are compared with those measured at other urban sites globally. The influences of aerosols originating from other regions outside of Southeast Asia are analyzed using trajectory analyses. Specifically, cases of aerosol transport and mixing from Southern China and from India are presented.

Quasi-Optical Network Analyzers and High-Reliability RF MEMS Switched Capacitors

Science.gov (United States)

Grichener, Alexander

The thesis first presents a 2-port quasi-optical scalar network analyzer consisting of a transmitter and receiver both built in planar technology. The network analyzer is based on a Schottky-diode mixer integrated inside a planar antenna and fed differentially by a CPW transmission line. The antenna is placed on an extended hemispherical high-resistivity silicon substrate lens. The LO signal is swept from 3-5 GHz and high-order harmonic mixing in both up- and down- conversion mode is used to realize the 15-50 GHz RF bandwidth. The network analyzer resulted in a dynamic range of greater than 40 dB and was successfully used to measure a frequency selective surface with a second-order bandpass response. Furthermore, the system was built with circuits and components for easy scaling to millimeter-wave frequencies which is the primary motivation for this work. The application areas for a millimeter and submillimeter-wave network analyzer include material characterization and art diagnostics. The second project presents several RF MEMS switched capacitors designed for high-reliability operation and suitable for tunable filters and reconfigurable networks. The first switched-capacitor resulted in a digital capacitance ratio of 5 and an analog capacitance ratio of 5-9. The analog tuning of the down-state capacitance is enhanced by a positive vertical stress gradient in the the beam, making it ideal for applications that require precision tuning. A thick electroplated beam resulted in Q greater than 100 at C to X-band frequencies, and power handling of 0.6-1.1 W. The design also minimized charging in the dielectric, resulting in excellent reliability performance even under hot-switched and high power (1 W) conditions. The second switched-capacitor was designed without any dielectric to minimize charging. The device was hot-switched at 1 W of RF power for greater than 11 billion cycles with virtually no change in the C-V curve. The final project presents a 7-channel

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime.

Science.gov (United States)

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V

2012-06-01

Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.

Spectral-domain optical coherence tomography study on dynamic changes of human tears after instillation of artificial tears.

Science.gov (United States)

Napoli, Pietro Emanuele; Satta, Giovanni Maria; Coronella, Franco; Fossarello, Maurizio

2014-07-01

To analyze in vivo the dynamic changes induced by different artificial tears (ATs) in the precorneal tear film (PCTF) and lower tear meniscus (LTM) by using spectral-domain (SD) anterior segment optical coherence tomography (OCT). We prospectively examined 42 normal human eyes by using SD-OCT imaging. On the day before OCT imaging, all enrolled subjects were evaluated for abnormalities of ocular surface. All tear film images were obtained before and after instillation of three different types of ATs (mucomimetic, lipid-based, and saline) in five serial scans: immediately (within 30 seconds), at the first, fifth, 10th, and 20th minute. Subjects received a drop of 35 μL in one randomly selected eye. All examinations were conducted in the same conditions of temperature, brightness, humidity, and time of day. Changes in the morphological pattern of both LTM and PCTF were associated with the type of artificial tear instilled on the ocular surface. Similarly, the radius of curvature (rc), the height (h), and the depth (d) showed dynamic variations depending on treatment. Although by the 20th minute, both h and d returned to baseline values in all groups, a significant difference in rc (compared with baseline) was detected for mucomimetic ATs (P = 0.04) and lipid ATs (P = 0.02). Spectral-domain OCT imaging has preliminarily proved to be a noninvasive tool to evaluate, in real time, the different changes induced by ATs instillation. An important stride in understanding the clinical response to various tear substitutes can be achieved by this objective and quantitative approach. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Precise Multi-Spectral Dermatological Imaging

DEFF Research Database (Denmark)

Gomez, David Delgado; Carstensen, Jens Michael; Ersbøll, Bjarne Kjær

2004-01-01

In this work, an integrated imaging system to obtain accurate and reproducible multi-spectral dermatological images is proposed. The system is made up of an integrating sphere, light emitting diodes and a generic monochromatic camera. The system can collect up to 10 different spectral bands....... These spectral bands vary from ultraviolet to near infrared. The welldefined and diffuse illumination of the optically closed scene aims to avoid shadows and specular reflections. Furthermore, the system has been developed to guarantee the reproducibility of the collected images. This allows for comparative...

An optical spectroscopic study of T Tauri stars. I. Photospheric properties

Energy Technology Data Exchange (ETDEWEB)

Herczeg, Gregory J. [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian Qu, Beijing 100871 (China); Hillenbrand, Lynne A. [Caltech, MC105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States)

2014-05-10

Estimates of the mass and age of young stars from their location in the H-R diagram are limited by not only the typical observational uncertainties that apply to field stars, but also by large systematic uncertainties related to circumstellar phenomena. In this paper, we analyze flux-calibrated optical spectra to measure accurate spectral types and extinctions of 281 nearby T Tauri stars (TTSs). The primary advances in this paper are (1) the incorporation of a simplistic accretion continuum in optical spectral type and extinction measurements calculated over the full optical wavelength range and (2) the uniform analysis of a large sample of stars, many of which are well known and can serve as benchmarks. Comparisons between the non-accreting TTS photospheric templates and stellar photosphere models are used to derive conversions from spectral type to temperature. Differences between spectral types can be subtle and difficult to discern, especially when accounting for accretion and extinction. The spectral types measured here are mostly consistent with spectral types measured over the past decade. However, our new spectral types are one to two subclasses later than literature spectral types for the original members of the TW Hya Association (TWA) and are discrepant with literature values for some well-known members of the Taurus Molecular Cloud. Our extinction measurements are consistent with other optical extinction measurements but are typically 1 mag lower than near-IR measurements, likely the result of methodological differences and the presence of near-IR excesses in most CTTSs. As an illustration of the impact of accretion, spectral type, and extinction uncertainties on the H-R diagrams of young clusters, we find that the resulting luminosity spread of stars in the TWA is 15%-30%. The luminosity spread in the TWA and previously measured for binary stars in Taurus suggests that for a majority of stars, protostellar accretion rates are not large enough to

High symmetry versus optical isotropy of a negative-index metamaterial

DEFF Research Database (Denmark)

Menzel, Christoph; Rockstuhl, Carsten; Lliew, Rumen

2010-01-01

condition since it is usually assumed that light does not resolve the spatial details of MM but experiences the properties of an effective medium, which is then optically isotropic. In this work we challenge this assumption by analyzing the isofrequency surfaces of the dispersion relation of the split cube...... in carcass negative index MM. We show that this MM is basically optically isotropic but not in the spectral domain where it exhibits negative refraction. The primary goal of this contribution is to introduce a tool that allows to probe a MM against optical isotropy....

APPLICATION OF CHEMOMETRICS FOR ANALYSIS OF BIOAEROSOLS BY FLOW-OPTICAL METHOD

Directory of Open Access Journals (Sweden)

E. S. Khudyakov

2016-01-01

Full Text Available Subject of Research. The informativity of detection channels for bioaerosol analyzer is investigated. Analyzer operation is based on flow-optical method. Method. Measurements of fluorescence and the light scattering of separate bioaerosol particles were performed in five and two spectral ranges, correspondingly. The signals of soil dust particles were registered and used as an imitation of background atmospheric particles. For fluorescenceinduction of bioaerosol particles we used light sources: a laser one with a wavelength equal to 266 nm and 365 nm LED source.Main Results. Using chemometric data processing the classification of informative parameters has been performed and three most significant parameters have been chosen which account for 72% of total data variance. Testing has been done using SIMCA and k-NN methods. It has been proved that the use of the original and the reduced sets of three parameters produces comparable accuracy for classification of bioaerosols. Practical Relevance. The possibility of rapid detection and identification of bioaerosol particles of 1-10 microns respirable fraction (hindering in the human respiratory system by flow-optical method on a background of non-biological particles is demonstrated. The most informative optical spectral ranges for development of compact and inexpensive analyzer are chosen.

A spectral analysis of the domain decomposed Monte Carlo method for linear systems

Energy Technology Data Exchange (ETDEWEB)

Slattery, S. R.; Wilson, P. P. H. [Engineering Physics Department, University of Wisconsin - Madison, 1500 Engineering Dr., Madison, WI 53706 (United States); Evans, T. M. [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37830 (United States)

2013-07-01

The domain decomposed behavior of the adjoint Neumann-Ulam Monte Carlo method for solving linear systems is analyzed using the spectral properties of the linear operator. Relationships for the average length of the adjoint random walks, a measure of convergence speed and serial performance, are made with respect to the eigenvalues of the linear operator. In addition, relationships for the effective optical thickness of a domain in the decomposition are presented based on the spectral analysis and diffusion theory. Using the effective optical thickness, the Wigner rational approximation and the mean chord approximation are applied to estimate the leakage fraction of stochastic histories from a domain in the decomposition as a measure of parallel performance and potential communication costs. The one-speed, two-dimensional neutron diffusion equation is used as a model problem to test the models for symmetric operators. In general, the derived approximations show good agreement with measured computational results. (authors)

A spectral analysis of the domain decomposed Monte Carlo method for linear systems

International Nuclear Information System (INIS)

Slattery, S. R.; Wilson, P. P. H.; Evans, T. M.

2013-01-01

The domain decomposed behavior of the adjoint Neumann-Ulam Monte Carlo method for solving linear systems is analyzed using the spectral properties of the linear operator. Relationships for the average length of the adjoint random walks, a measure of convergence speed and serial performance, are made with respect to the eigenvalues of the linear operator. In addition, relationships for the effective optical thickness of a domain in the decomposition are presented based on the spectral analysis and diffusion theory. Using the effective optical thickness, the Wigner rational approximation and the mean chord approximation are applied to estimate the leakage fraction of stochastic histories from a domain in the decomposition as a measure of parallel performance and potential communication costs. The one-speed, two-dimensional neutron diffusion equation is used as a model problem to test the models for symmetric operators. In general, the derived approximations show good agreement with measured computational results. (authors)

A Bayesian approach to spectral quantitative photoacoustic tomography

International Nuclear Information System (INIS)

Pulkkinen, A; Kaipio, J P; Tarvainen, T; Cox, B T; Arridge, S R

2014-01-01

A Bayesian approach to the optical reconstruction problem associated with spectral quantitative photoacoustic tomography is presented. The approach is derived for commonly used spectral tissue models of optical absorption and scattering: the absorption is described as a weighted sum of absorption spectra of known chromophores (spatially dependent chromophore concentrations), while the scattering is described using Mie scattering theory, with the proportionality constant and spectral power law parameter both spatially-dependent. It is validated using two-dimensional test problems composed of three biologically relevant chromophores: fat, oxygenated blood and deoxygenated blood. Using this approach it is possible to estimate the Grüneisen parameter, the absolute chromophore concentrations, and the Mie scattering parameters associated with spectral photoacoustic tomography problems. In addition, the direct estimation of the spectral parameters is compared to estimates obtained by fitting the spectral parameters to estimates of absorption, scattering and Grüneisen parameter at the investigated wavelengths. It is shown with numerical examples that the direct estimation results in better accuracy of the estimated parameters. (papers)

A threshold-based multiple optical signal selection scheme for WDM FSO systems

KAUST Repository

Nam, Sung Sik

2017-07-20

In this paper, we propose a threshold-based-multiple optical signal selection scheme (TMOS) for free-space optical systems based on wavelength division multiplexing. With the proposed TMOS, we can obtain higher spectral efficiency while reducing the potential increase in complexity of implementation caused by applying a selection-based beam selection scheme without a considerable performance loss. Here, to accurately characterize the performance of the proposed TMOS, we statistically analyze the characteristics with heterodyne detection technique over independent and identically distributed Log-normal turbulence conditions taking into considerations the impact of pointing error. Specifically, we derive exact closed-form expressions for the average bit error rate, and the average spectral efficiency by adopting an adaptive modulation. Some selected results shows that the average spectral efficiency can be increased with TMOS while the system requirement is satisfied.

A threshold-based multiple optical signal selection scheme for WDM FSO systems

KAUST Repository

Nam, Sung Sik; Alouini, Mohamed-Slim; Ko, Young-Chai; Cho, Sung Ho

2017-01-01

In this paper, we propose a threshold-based-multiple optical signal selection scheme (TMOS) for free-space optical systems based on wavelength division multiplexing. With the proposed TMOS, we can obtain higher spectral efficiency while reducing the potential increase in complexity of implementation caused by applying a selection-based beam selection scheme without a considerable performance loss. Here, to accurately characterize the performance of the proposed TMOS, we statistically analyze the characteristics with heterodyne detection technique over independent and identically distributed Log-normal turbulence conditions taking into considerations the impact of pointing error. Specifically, we derive exact closed-form expressions for the average bit error rate, and the average spectral efficiency by adopting an adaptive modulation. Some selected results shows that the average spectral efficiency can be increased with TMOS while the system requirement is satisfied.

Comparison of retina specialist preferences regarding spectral-domain and swept-source optical coherence tomography angiography

Directory of Open Access Journals (Sweden)

Su GL

2017-05-01

Full Text Available Grace L Su,1 Douglas M Baughman,2 Qinqin Zhang,3 Kasra Rezaei,2 Aaron Y Lee,2 Cecilia S Lee2 1Lewis Katz School of Medicine, Temple University, Philadelphia, PA, 2Department of Ophthalmology, 3Department of Bioengineering, University of Washington, Seattle, WA, USA Purpose: The aim of this study was to compare physician preferences regarding the commercially available spectral-domain (SD optical coherence tomography angiography (OCTA and swept-source (SS OCTA prototype device.Design: Comparative analysis of diagnostic instruments was performed.Patients and methods: Subjects at the University of Washington Eye Institute and Harborview Medical Center were prospectively recruited and imaged with the Zeiss SD OCTA (HD-5000, Angioplex and Zeiss SS OCTA (Plex Elite, Everest devices on the same day. The study included 10 eyes from 10 subjects diagnosed with a retinal/choroidal disease. Deidentified images were compiled into a survey and sent to retina specialists in various countries. The survey presented masked SD and SS images of each eye for each retinal sublayer side by side. Respondents were asked about their image preference and impact on clinical management. A priori and post hoc preferences for SD vs SS were collected.Results: Fifty-four retina specialists responded to the survey. Median years in practice was 3.00 (interquartile range [IQR] 1.50–17.00. At baseline, 23 (48% physicians owned an OCTA machine. The majority of physician responses showed a preference for the SS over SD OCTA, independent of the retinal pathology shown (n=454 overall responses, 74%. Nevertheless, the majority indicated that both SD and SS would be equally valuable in informing clinical decisions (n=374 overall responses, 61%.Conclusion: These findings indicate that the majority of retina specialists surveyed prefer SS over SD OCTA based on image quality, regardless of the retinal pathology shown. Regarding the clinical utility of each modality, the majority of

Coi-wiz: An interactive computer wizard for analyzing cardiac optical signals.

Science.gov (United States)

Yuan, Xiaojing; Uyanik, Ilyas; Situ, Ning; Xi, Yutao; Cheng, Jie

2009-01-01

A number of revolutionary techniques have been developed for cardiac electrophysiology research to better study the various arrhythmia mechanisms that can enhance ablating strategies for cardiac arrhythmias. Once the three-dimensional high resolution cardiac optical imaging data is acquired, it is time consuming to manually go through them and try to identify the patterns associated with various arrhythmia symptoms. In this paper, we present an interactive computer wizard that helps cardiac electrophysiology researchers to visualize and analyze the high resolution cardiac optical imaging data. The wizard provides a file interface that accommodates different file formats. A series of analysis algorithms output waveforms, activation and action potential maps after spatial and temporal filtering, velocity field and heterogeneity measure. The interactive GUI allows the researcher to identify the region of interest in both the spatial and temporal domain, thus enabling them to study different heart chamber at their choice.

Effective spectral index properties for Fermi blazars

Science.gov (United States)

Yang, JiangHe; Fan, JunHui; Liu, Yi; Zhang, YueLian; Tuo, ManXian; Nie, JianJun; Yuan, YuHai

2018-05-01

Blazars are a special subclass of active galactic nuclei with extreme observation properties. This subclass can be divided into two further subclasses of flat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs) according to their emission line features. To compare the spectral properties of FSRQs and BL Lacs, the 1.4 GHz radio, optical R-band, 1 keV X-ray, and 1 GeV γ-ray flux densities for 1108 Fermi blazars are calculated to discuss the properties of the six effective spectral indices of radio to optical ( α RO), radio to X-ray ( α RX), radio to γ ray ( α Rγ), optical to X-ray ( α OX), optical to γ ray ( α Oγ), and X-ray to γ ray ( α Xγ). The main results are as follows: For the averaged effective spectral indices, \\overline {{α _{OX}}} > \\overline {{α _{Oγ }}} > \\overline {{α _{Xγ }}} > \\overline {{α _{Rγ }}} > \\overline {{α _{RX}}} > \\overline {{α _{RO}}} for samples of whole blazars and BL Lacs; \\overline {{α _{Xγ }}} ≈ \\overline {{α _{Rγ }}} ≈ \\overline {{α _{RX}}} for FSRQs and low-frequency-peaked BL Lacs (LBLs); and \\overline {{α _{OX}}} ≈ \\overline {{α _{Oγ }}} ≈ \\overline {{α _{Xγ }}} for high-synchrotron-frequency-peaked BL Lacs (HBLs). The distributions of the effective spectral indices involving optical emission ( α RO, α OX, and α Oγ) for LBLs are different from those for FSRQs, but if the effective spectral index does not involve optical emission ( α RX, α Rγ, and α Xγ), the distributions for LBLs and FSRQs almost come from the same parent population. X-ray emissions from blazars include both synchrotron and inverse Compton (IC) components; the IC component for FSRQs and LBLs accounts for a larger proportion than that for HBLs; and the radiation mechanism for LBLs is similar to that for FSRQs, but the radiation mechanism for HBLs is different from that for both FSRQs and LBLs in X-ray bands. The tendency of α Rγ decreasing from LBLs to HBLs suggests that the synchrotron self

Spectral response modeling and analysis of p–n–p In0.53Ga0.47As/InP HPTs

International Nuclear Information System (INIS)

Chen Jun; Lv Jiabing

2016-01-01

We report our results on the modeling of the spectral response of the near-infrared (NIR) lattice-matched p–n–p In 0.53 Ga 0.47 As/InP heterojunction phototransistors (HPTs). The spectral response model is developed from the solution of the steady state continuity equations that dominate the excess optically generated minority-carriers in the active regions of the HPTs with accurate boundary conditions. In addition, a detailed optical-power absorption profile is constructed for the device modeling. The calculated responsivity is in good agreement with the measured one for the incident radiation at 980 nm, 1310 nm, and 1550 nm. Furthermore, the variation in the responsivity of the device with the base region width is analyzed. (paper)

Spectral-Domain Measurement of Strain Sensitivity of a Two-Mode Birefringent Side-Hole Fiber

Directory of Open Access Journals (Sweden)

Waclaw Urbanczyk

2012-09-01

Full Text Available The strain sensitivity of a two-mode birefringent side-hole fiber is measured in the spectral domain. In a simple experimental setup comprising a broadband source, a polarizer, a two-mode birefringent side-hole fiber under varied elongations, an analyzer and a compact spectrometer, the spectral interferograms are resolved. These are characterized by the equalization wavelength at which spectral interference fringes have the highest visibility (the largest period due to the zero group optical path difference between the fundamental, the LP01 mode and the higher-order, the LP11 mode. The spectral interferograms with the equalization wavelength are processed to retrieve the phase as a function of the wavelength. From the retrieved phase functions corresponding to different elongations of a two-mode birefringent side-hole fiber under test, the spectral strain sensitivity is obtained. Using this approach, the intermodal spectral strain sensitivity was measured for both x and y polarizations. Moreover, the spectral polarimetric sensitivity to strain was measured for the fundamental mode when a birefringent delay line was used in tandem with the fiber. Its spectral dependence was also compared with that obtained from a shift of the spectral interferograms not including the equalization wavelength, and good agreement was confirmed.

A spectral approach for the quantitative description of cardiac collagen network from nonlinear optical imaging.

Science.gov (United States)

Masè, Michela; Cristoforetti, Alessandro; Avogaro, Laura; Tessarolo, Francesco; Piccoli, Federico; Caola, Iole; Pederzolli, Carlo; Graffigna, Angelo; Ravelli, Flavia

2015-01-01

The assessment of collagen structure in cardiac pathology, such as atrial fibrillation (AF), is essential for a complete understanding of the disease. This paper introduces a novel methodology for the quantitative description of collagen network properties, based on the combination of nonlinear optical microscopy with a spectral approach of image processing and analysis. Second-harmonic generation (SHG) microscopy was applied to atrial tissue samples from cardiac surgery patients, providing label-free, selective visualization of the collagen structure. The spectral analysis framework, based on 2D-FFT, was applied to the SHG images, yielding a multiparametric description of collagen fiber orientation (angle and anisotropy indexes) and texture scale (dominant wavelength and peak dispersion indexes). The proof-of-concept application of the methodology showed the capability of our approach to detect and quantify differences in the structural properties of the collagen network in AF versus sinus rhythm patients. These results suggest the potential of our approach in the assessment of collagen properties in cardiac pathologies related to a fibrotic structural component.

Quasi-periodic photonic crystal Fabry–Perot optical filter based on Si/SiO2 for visible-laser spectral selectivity

Science.gov (United States)

Qi, Dong; Wang, Xian; Cheng, Yongzhi; Chen, Fu; Liu, Lei; Gong, Rongzhou

2018-06-01

We report on a 1D quasi-periodic photonic crystal Fabry–Perot optical filter Cs(Si/SiO2)3(SiO2/Si)3 for spectral selectivity of visible light and 1.55 µm laser. A material transparency interval of 1.03–2.06 µm makes Si a unique choice of high refractive index material. Owing to the CIE 1931 standard and equal inclination interference, the designed structure can be successfully fabricated with a certain color (brown, khaki, or blue) corresponding to the different Cs physical thickness d and response R(λ). In addition, the peak transmittance T max of the proposed structure can reach as high as 92.56% (Cs  =  20 nm), 90.83% (Cs  =  40 nm), and 88.85% (Cs  =  60 nm) with a relatively narrow full width at half maximum of 4.4, 4.6, and 4.8 nm at 1.55 µm. The as-prepared structure indicates that it is feasible for a photonic crystal Fabry–Perot optical filter to achieve visible-laser (1.55 µm) spectral selectivity.

Age, Sex, and Ethnic Variations in Inner and Outer Retinal and Choroidal Thickness on Spectral-Domain Optical Coherence Tomography.

Science.gov (United States)

Bafiq, Rinoza; Mathew, Raeba; Pearce, Elizabeth; Abdel-Hey, Ahmed; Richardson, Matthew; Bailey, Thomas; Sivaprasad, Sobha

2015-11-01

To evaluate age, sex, and ethnic variations in inner and outer retinal and choroidal thickness and foveal pit, using spectral-domain optical coherence tomography (SD OCT). Single-center observational cross-sectional study. Ninety randomly selected, healthy individuals of white, black, and South Asian origin underwent SD OCT raster and enhanced depth imaging scan. Manual measurements of inner and outer retinal thickness and choroidal thickness up to 3 mm nasal and temporal to the fovea were performed. The age, sex, and ethnic differences in these parameters were analyzed. The mean inner retinal thickness was lower by approximately 12 μm in black subjects across the central retina compared to white subjects (P ethnic groups but the temporal choroid was significantly thinner in black subjects (P < .05). The choroid showed an age-related decline in thickness of 2 μm per year of age of the subjects. Interethnic differences include wider fovea, lower central foveal thickness, and thinner inner retina in eyes of black subjects compared to their white and South Asian counterparts. Copyright © 2015 Elsevier Inc. All rights reserved.

Optical vector network analyzer based on double-sideband modulation.

Science.gov (United States)

Jun, Wen; Wang, Ling; Yang, Chengwu; Li, Ming; Zhu, Ning Hua; Guo, Jinjin; Xiong, Liangming; Li, Wei

2017-11-01

We report an optical vector network analyzer (OVNA) based on double-sideband (DSB) modulation using a dual-parallel Mach-Zehnder modulator. The device under test (DUT) is measured twice with different modulation schemes. By post-processing the measurement results, the response of the DUT can be obtained accurately. Since DSB modulation is used in our approach, the measurement range is doubled compared with conventional single-sideband (SSB) modulation-based OVNA. Moreover, the measurement accuracy is improved by eliminating the even-order sidebands. The key advantage of the proposed scheme is that the measurement of a DUT with bandpass response can also be simply realized, which is a big challenge for the SSB-based OVNA. The proposed method is theoretically and experimentally demonstrated.

Night myopia studied with an adaptive optics visual analyzer.

Directory of Open Access Journals (Sweden)

Pablo Artal

Full Text Available PURPOSE: Eyes with distant objects in focus in daylight are thought to become myopic in dim light. This phenomenon, often called "night myopia" has been studied extensively for several decades. However, despite its general acceptance, its magnitude and causes are still controversial. A series of experiments were performed to understand night myopia in greater detail. METHODS: We used an adaptive optics instrument operating in invisible infrared light to elucidate the actual magnitude of night myopia and its main causes. The experimental setup allowed the manipulation of the eye's aberrations (and particularly spherical aberration as well as the use of monochromatic and polychromatic stimuli. Eight subjects with normal vision monocularly determined their best focus position subjectively for a Maltese cross stimulus at different levels of luminance, from the baseline condition of 20 cd/m(2 to the lowest luminance of 22 × 10(-6 cd/m(2. While subjects performed the focusing tasks, their eye's defocus and aberrations were continuously measured with the 1050-nm Hartmann-Shack sensor incorporated in the adaptive optics instrument. The experiment was repeated for a variety of controlled conditions incorporating specific aberrations of the eye and chromatic content of the stimuli. RESULTS: We found large inter-subject variability and an average of -0.8 D myopic shift for low light conditions. The main cause responsible for night myopia was the accommodation shift occurring at low light levels. Other factors, traditionally suggested to explain night myopia, such as chromatic and spherical aberrations, have a much smaller effect in this mechanism. CONCLUSIONS: An adaptive optics visual analyzer was applied to study the phenomenon of night myopia. We found that the defocus shift occurring in dim light is mainly due to accommodation errors.

Forum metrology 2009: control of optics, targets and optical analyzers

International Nuclear Information System (INIS)

Desenne, D.; Andre, R.

2010-01-01

The 1. 'Forum Metrologie' of the CEA/DAM has been held in the 'Institut Laser et Plasma' on the December 9, 2009, close to the 'Centre d'etudes Scientifiques et Techniques d'Aquitaine'. It has been set up by the 'Departement Lasers de Puissance'. The chosen thematic was the metrology around laser experiments, with a special focus on the metrology of the dedicated optics, targets and optical analysers. The talks have shown the progress and difficulties in each of these fields. (authors)

Self-phase-modulation induced spectral broadening in silicon waveguides

Science.gov (United States)

Boyraz, Ozdal; Indukuri, Tejaswi; Jalali, Bahram

2004-03-01

The prospect for generating supercontinuum pulses on a silicon chip is studied. Using ~4ps optical pulses with 2.2GW/cm2 peak power, a 2 fold spectral broadening is obtained. Theoretical calculations, that include the effect of two-photon-absorption, indicate up to 5 times spectral broadening is achievable at 10x higher peak powers. Representing a nonlinear loss mechanism at high intensities, TPA limits the maximum optical bandwidth that can be generated.

Integrated optics refractometry: sensitivity in relation to spectral shifts

NARCIS (Netherlands)

Hoekstra, Hugo; Hammer, M.

2013-01-01

A new variant of the Vernier-effect based sensor reported in ref. 1 is introduced. Both sensor types may show a huge index induced spectral shift. It will be shown in a poster presentation that with such sensors, as well as with surface plasmon based sensors, the constraints on the spectral

Spectral approach to optical resonator theory

International Nuclear Information System (INIS)

Feit, M.D.; Fleck, J.A. Jr.

1981-01-01

A new computational method for unloaded optical resonators is developed based on the discrete Fourier analysis of informaton generated by repated iterations of the optical field corresponding to transits between reflectors. The method is a straightforward extension of the propagating beam method developed earlier for optical fibers for extracting modal properties from numerical solutions to the paraxial scalar wave equation. The method requires computation of a field correlation function, whose Fourier transform reveals the eigenmodes as resonant peaks. Analysis of the location and breadth of these peaks determines the resonator eigenvalues When the eigenvalues are known, additional discrete Fourier transforms of the field are used to generate the mode eigenfunctions. This new method makes possible the unambiguous identification and accurate characterization of the entire spectrum of transverse resonator modes

Atlas of Atomic Spectral Lines of Neptunium Emitted by Inductively Coupled Plasma

Energy Technology Data Exchange (ETDEWEB)

DeKalb, E.L. and Edelson, M. C.

1987-08-01

Optical emission spectra from high-purity Np-237 were generated with a glovebox-enclosed inductively coupled plasma (ICP) source. Spectra covering the 230-700 nm wavelength range are presented along with general commentary on the methodology used in collecting the data. The Ames Laboratory Nuclear Safeguards and Security Program has been charged with the task of developing optical spectroscopic methods to analyze the composition of spent nuclear fuels. Such materials are highly radioactive even after prolonged 'cooling' and are chemically complex. Neptunium (Np) is a highly toxic by-product of nuclear power generation and is found, in low abundance, in spent nuclear fuels. This atlas of the optical emission spectrum of Np, as produced by an inductively coupled plasma (ICP) spectroscopic source, is part of a general survey of the ICP emission spectra of the actinide elements. The ICP emission spectrum of the actinides originates almost exclusively from the electronic relaxation of excited, singly ionized species. Spectral data on the Np ion emission spectrum (i.e., the Np II spectrum) have been reported by Tomkins and Fred [1] and Haaland [2]. Tomkins and Fred excited the Np II spectrum with a Cu spark discharge and identified 114 Np lines in the 265.5 - 436.3 nm spectral range. Haaland, who corrected some spectral line misidentifications in the work of Tomkins and Fred, utilized an enclosed Au spark discharge to excite the Np II spectrum and reported 203 Np lines within the 265.4 - 461.0 nm wavelength range.

Littoral Assessment of Mine Burial Signatures (LAMBS) buried land mine/background spectral signature analyses

Science.gov (United States)

Kenton, A.C.; Geci, D.M.; Ray, K.J.; Thomas, C.M.; Salisbury, J.W.; Mars, J.C.; Crowley, J.K.; Witherspoon, N.H.; Holloway, J.H.; Harmon R.S.Broach J.T.Holloway, Jr. J.H.

2004-01-01

The objective of the Office of Naval Research (ONR) Rapid Overt Reconnaissance (ROR) program and the Airborne Littoral Reconnaissance Technologies (ALRT) project's LAMBS effort is to determine if electro-optical spectral discriminants exist that are useful for the detection of land mines in littoral regions. Statistically significant buried mine overburden and background signature data were collected over a wide spectral range (0.35 to 14 ??m) to identify robust spectral features that might serve as discriminants for new airborne sensor concepts. LAMBS has expanded previously collected databases to littoral areas - primarily dry and wet sandy soils - where tidal, surf, and wind conditions can severely modify spectral signatures. At AeroSense 2003, we reported completion of three buried mine collections at an inland bay, Atlantic and Gulf of Mexico beach sites.1 We now report LAMBS spectral database analyses results using metrics which characterize the detection performance of general types of spectral detection algorithms. These metrics include mean contrast, spectral signal-to-clutter, covariance, information content, and spectral matched filter analyses. Detection performance of the buried land mines was analyzed with regard to burial age, background type, and environmental conditions. These analyses considered features observed due to particle size differences, surface roughness, surface moisture, and compositional differences.

A simple multipurpose double-beam optical image analyzer

Energy Technology Data Exchange (ETDEWEB)

Popowicz, A., E-mail: adam.popowicz@polsl.pl [Institute of Automatic Control, Silesian University of Technology, Akademicka Str. 16, 44-100 Gliwice (Poland); Blachowicz, T. [Institute of Physics - Center for Science and Education, Silesian University of Technology, S. Konarskiego 22B Str., 44-100 Gliwice (Poland)

2016-07-15

In the paper we present a low cost optical device which splits the light in the focal plane into two separate optical paths and collimates it back into a single image plane, and where a selective information processing can be carried out. The optical system is straightforward and easily implementable as it consists of only three lenses and two mirrors. The system is dedicated for imaging in low-light-level conditions in which widely used optical devices, based on beam splitters or dichroic mirrors, suffer from light loss. We expose examples of applications of our device, using a prototype model. The proposed optical system may be employed for: monitoring the objects located at different distances from observer (1), creating regions of different magnification within a single image plane (2), high dynamic range photometry (3), or imaging in two wavelength bands simultaneously (4).

High-speed spectral domain optical coherence tomography using non-uniform fast Fourier transform

Science.gov (United States)

Chan, Kenny K. H.; Tang, Shuo

2010-01-01

The useful imaging range in spectral domain optical coherence tomography (SD-OCT) is often limited by the depth dependent sensitivity fall-off. Processing SD-OCT data with the non-uniform fast Fourier transform (NFFT) can improve the sensitivity fall-off at maximum depth by greater than 5dB concurrently with a 30 fold decrease in processing time compared to the fast Fourier transform with cubic spline interpolation method. NFFT can also improve local signal to noise ratio (SNR) and reduce image artifacts introduced in post-processing. Combined with parallel processing, NFFT is shown to have the ability to process up to 90k A-lines per second. High-speed SD-OCT imaging is demonstrated at camera-limited 100 frames per second on an ex-vivo squid eye. PMID:21258551

Analyzing quantum jumps of one and two atoms strongly coupled to an optical cavity

DEFF Research Database (Denmark)

Reick, Sebastian; Mølmer, Klaus; Alt, Wolfgang

2010-01-01

We induce quantum jumps between the hyperfine ground states of one and two cesium atoms, strongly coupled to the mode of a high-finesse optical resonator, and analyze the resulting random telegraph signals. We identify experimental parameters to deduce the atomic spin state nondestructively from ...

Optical properties behavior of three optical filters and a mirror used in the internal optical head of a Raman laser spectrometer after exposed to proton radiation

Science.gov (United States)

Guembe, V.; Alvarado, C. G.; Fernández-Rodriguez, M.; Gallego, P.; Belenguer, T.; Díaz, E.

2017-11-01

The Raman Laser Spectrometer is one of the ExoMars Pasteur Rover's payload instruments that is devoted to the analytical analysis of the geochemistry content and elemental composition of the observed minerals provided by the Rover through Raman spectroscopy technique. One subsystem of the RLS instrument is the Internal Optical Head unit (IOH), which is responsible for focusing the light coming from the laser onto the mineral under analysis and for collecting the Raman signal emitted by the excited mineral. The IOH is composed by 4 commercial elements for Raman spectroscopy application; 2 optical filters provided by Iridian Spectral Technologies Company and 1 optical filter and 1 mirror provided by Semrock Company. They have been exposed to proton radiation in order to analyze their optical behaviour due to this hostile space condition. The proton irradiation test was performed following the protocol of LINES lab (INTA). The optical properties have been studied through transmittance, reflectance and optical density measurements, the final results and its influence on optical performances are presented.

Fundus autofluorescence in central serous chorioretinopathy:association with spectral-domain optical coherence tomography and fluorescein angiography

Directory of Open Access Journals (Sweden)

Peng Zhang

2015-10-01

Full Text Available AIM: To evaluate the correlation among changes in fundus autofluorescence (AF measured using infrared fundus AF (IR-AF and short-wave length fundus AF (SW-AF with changes in spectral-domain optical coherence tomography (SD-OCT and fluorescein angiography (FA in central serous chorioretinopathy (CSC.METHODS:Two hundred and twenty consecutive patients with CSC were included. In addition to AF, patients were assessed by means of SD-OCT and FA. Abnormalities in images of IR-AF, SW-AF, FA were analyzed and correlated with the corresponding outer retinal alterations in SD-OCT findings.RESULTS:Eyes with abnormalities on either IR-AF or SW-AF were found in 256 eyes (58.18%, among them 256 eyes (100% showed abnormal IR-AF, but SW-AF abnormalities were present only in 213 eyes (83.20%. The hypo-IR-AF corresponded to accumulation of sub-retinal liquid, collapse of retinal pigment epithelium (RPE or detachment of RPE with or without RPE leakage point in the corresponding area. The hyper-IR-AF corresponded to the area with loss of the ellipsoid portion of the inner segments and sub-sensory retinal deposits or focal melanogenesis under sensory retina. The hypo-SW-AF corresponded to accumulation of sub-retinal liquid or atrophy of RPE. The hyper-SW-AF associated with sub-sensory retinal deposits, detachment of RPE and focal melanogenesis.CONCLUSION:IR-AF was more sensitive than SW-AF and FA for identifying pathological abnormalities in CSC. The characteristics of IR-AF in CSC were attributable to the modification of melanin in the RPE. IR-AF should be used as a common diagnostic tool for identifying pathological lesion in CSC.KEYWORDS:central serous chorioretinopathy; fluorescein angiography; fundus autofluorescence; optical coherence tomography

Advanced astigmatism-corrected tandem Wadsworth mounting for small-scale spectral broadband imaging spectrometer.

Science.gov (United States)

Lei, Yu; Lin, Guan-yu

2013-01-01

Tandem gratings of double-dispersion mount make it possible to design an imaging spectrometer for the weak light observation with high spatial resolution, high spectral resolution, and high optical transmission efficiency. The traditional tandem Wadsworth mounting is originally designed to match the coaxial telescope and large-scale imaging spectrometer. When it is used to connect the off-axis telescope such as off-axis parabolic mirror, it presents lower imaging quality than to connect the coaxial telescope. It may also introduce interference among the detector and the optical elements as it is applied to the short focal length and small-scale spectrometer in a close volume by satellite. An advanced tandem Wadsworth mounting has been investigated to deal with the situation. The Wadsworth astigmatism-corrected mounting condition for which is expressed as the distance between the second concave grating and the imaging plane is calculated. Then the optimum arrangement for the first plane grating and the second concave grating, which make the anterior Wadsworth condition fulfilling each wavelength, is analyzed by the geometric and first order differential calculation. These two arrangements comprise the advanced Wadsworth mounting condition. The spectral resolution has also been calculated by these conditions. An example designed by the optimum theory proves that the advanced tandem Wadsworth mounting performs excellently in spectral broadband.

Laser's calibration of an AOTF-based spectral colorimeter

Science.gov (United States)

Emelianov, Sergey P.; Khrustalev, Vladimir N.; Kochin, Leonid B.; Polosin, Lev L.

2003-06-01

The paper is devoted to expedients of AOTF spectral colorimeters calibration. The spectrometer method of color values measuring with reference to spectral colorimeters on AOTF surveyed. The theoretical exposition of spectrometer data processing expedients is offered. The justified source of radiation choice, suitable for calibration of spectral colorimeters is carried out. The experimental results for different acousto-optical mediums and modes of interaction are submitted.

Retinal Imaging of Infants on Spectral Domain Optical Coherence Tomography

Directory of Open Access Journals (Sweden)

Anand Vinekar

2015-01-01

Full Text Available Spectral domain coherence tomography (SD OCT has become an important tool in the management of pediatric retinal diseases. It is a noncontact imaging device that provides detailed assessment of the microanatomy and pathology of the infant retina with a short acquisition time allowing office examination without the requirement of anesthesia. Our understanding of the development and maturation of the infant fovea has been enhanced by SD OCT allowing an in vivo assessment that correlates with histopathology. This has helped us understand the critical correlation of foveal development with visual potential in the first year of life and beyond. In this review, we summarize the recent literature on the clinical applications of SD OCT in studying the pathoanatomy of the infant macula, its ability to detect subclinical features, and its correlation with disease and vision. Retinopathy of prematurity and macular edema have been discussed in detail. The review also summarizes the current status of SD OCT in other infant retinal conditions, imaging the optic nerve, the choroid, and the retinal nerve fibre in infants and children, and suggests future areas of research.

Analysis of physical layer performance of data center with optical wavelength switches based on advanced modulation formats

Science.gov (United States)

Ahmad, Iftikhar; Chughtai, Mohsan Niaz

2018-05-01

In this paper the IRIS (Integrated Router Interconnected spectrally), an optical domain architecture for datacenter network is analyzed. The IRIS integrated with advanced modulation formats (M-QAM) and coherent optical receiver is analyzed. The channel impairments are compensated using the DSP algorithms following the coherent receiver. The proposed scheme allows N2 multiplexed wavelengths for N×N size. The performance of the N×N-IRIS switch with and without wavelength conversion is analyzed for different Baud rates over M-QAM modulation formats. The performance of the system is analyzed in terms of bit error rate (BER) vs OSNR curves.

Characterization of spectral compression of OFDM symbols using optical time lenses

DEFF Research Database (Denmark)

Røge, Kasper Meldgaard; Guan, Pengyu; Kjøller, Niels-Kristian

2015-01-01

We present a detailed investigation of a double-time-lens subsystem for spectral compression of OFDM symbols. We derive optimized parameter settings by simulations and experimental characterization. The required chirp for OFDM spectral compression is very large.......We present a detailed investigation of a double-time-lens subsystem for spectral compression of OFDM symbols. We derive optimized parameter settings by simulations and experimental characterization. The required chirp for OFDM spectral compression is very large....

Changes in Tear Volume after 3% Diquafosol Treatment in Patients with Dry Eye Syndrome: An Anterior Segment Spectral-domain Optical Coherence Tomography Study.

Science.gov (United States)

Lee, Kwan Bok; Koh, Kyung Min; Kwon, Young A; Song, Sang Wroul; Kim, Byoung Yeop; Chung, Jae Lim

2017-08-01

To evaluate changes in the tear meniscus area and tear meniscus height over time in patients with dry eye syndrome, using anterior segment spectral-domain optical coherence tomography after the instillation of 3% diquafosol ophthalmic solution. Sixty eyes from 30 patients with mild to moderate dry eye syndrome were included. Tear meniscus images acquired by anterior segment spectral-domain optical coherence tomography were analyzed using National Institutes of Health's image-analysis software (ImageJ 1.44p). Tear meniscus area and tear meniscus height were measured at baseline, 5 minutes, 10 minutes, and 30 minutes after instillation of a drop of diquafosol in one eye and normal saline in the other eye. Changes in ocular surface disease index score, tear film break-up time, corneal staining score by Oxford schema, and meibomian expressibility were also evaluated at baseline, and after 1 week and 1 month of a diquafosol daily regimen. Sixty eyes from 30 subjects (mean age, 29.3 years; 8 men and 22 women) were included. In eyes receiving diquafosol, tear volume was increased at 5 and 10 minutes compared with baseline. It was also higher than saline instilled eyes at 5, 10, and 30 minutes. Changes in tear volume with respect to baseline were not statistically different after the use of diquafosol for 1 month. Ocular surface disease index score, tear film break-up time, and Oxford cornea stain score were significantly improved after 1 week and 1 month of daily diquafosol instillation, but meibomian expressibility did not change. Topical diquafosol ophthalmic solution effectively increased tear volume for up to 30 minutes, compared to normal saline in patients with dry eye syndrome. © 2017 The Korean Ophthalmological Society

Multiple spectral channels in branchiopods. I. Vision in dim light and neural correlates.

Science.gov (United States)

Lessios, Nicolas; Rutowski, Ronald L; Cohen, Jonathan H; Sayre, Marcel E; Strausfeld, Nicholas J

2018-05-22

Animals that have true color vision possess several spectral classes of photoreceptors. Pancrustaceans (Hexapoda+Crustacea) that integrate spectral information about their reconstructed visual world do so from photoreceptor terminals supplying their second optic neuropils, with subsequent participation of the third (lobula) and deeper centers (optic foci). Here, we describe experiments and correlative neural arrangements underlying convergent visual pathways in two species of branchiopod crustaceans that have to cope with a broad range of spectral ambience and illuminance in ephemeral pools, yet possess just two optic neuropils, the lamina and the optic tectum. Electroretinographic recordings and multimodel inference based on modeled spectral absorptance were used to identify the most likely number of spectral photoreceptor classes in their compound eyes. Recordings from the retina provide support for four color channels. Neuroanatomical observations resolve arrangements in their laminas that suggest signal summation at low light intensities, incorporating chromatic channels. Neuroanatomical observations demonstrate that spatial summation in the lamina of the two species are mediated by quite different mechanisms, both of which allow signals from several ommatidia to be pooled at single lamina monopolar cells. We propose that such summation provides sufficient signal for vision at intensities equivalent to those experienced by insects in terrestrial habitats under dim starlight. Our findings suggest that despite the absence of optic lobe neuropils necessary for spectral discrimination utilized by true color vision, four spectral photoreceptor classes have been maintained in Branchiopoda for vision at very low light intensities at variable ambient wavelengths that typify conditions in ephemeral freshwater habitats. © 2018. Published by The Company of Biologists Ltd.

THE PHOTOMETRIC AND SPECTRAL EVOLUTION OF THE 2008 LUMINOUS OPTICAL TRANSIENT IN NGC 300

International Nuclear Information System (INIS)

Humphreys, Roberta M.; Davidson, Kris; Bond, Howard E.; Bedin, Luigi R.; Bonanos, Alceste Z.; Berto Monard, L. A. G.; Prieto, José L.; Walter, Frederick M.

2011-01-01

The 2008 optical transient in NGC 300 is one of a growing class of intermediate-luminosity transients that brighten several orders of magnitude from a previously optically obscured state. The origin of their eruptions is not understood. Our multi-wavelength photometry and spectroscopy from maximum light to more than a year later provide a record of its post-eruption behavior. We describe its changing spectral energy distribution, the evolution of its absorption- and emission-line spectrum, the development of a bipolar outflow, and the rapid transition from a dense wind to an optically thin ionized wind. In addition to strong, narrow hydrogen lines, the F-type absorption-line spectrum of the transient is characterized by strong Ca II and [Ca II] emission. The very broad wings of the Ca II triplet and the asymmetric [Ca II] emission lines are due to strong Thomson scattering in the expanding ejecta. Post-maximum, the hydrogen and Ca II lines developed double-peaked emission profiles that we attribute to a bipolar outflow. Between approximately 60 and 100 days after maximum, the F-type absorption spectrum, formed in its dense wind, weakened and the wind became transparent to ionizing radiation. We discuss the probable evolutionary state of the transient and similar objects such as SN 2008S and conclude that they were most likely post-red supergiants or post-asymptotic giant branch stars on a blue loop to warmer temperatures when the eruption occurred. These objects are not luminous blue variables.

Specification of optical components using Wigner distribution function

International Nuclear Information System (INIS)

Xu Jiancheng; Li Haibo; Xu Qiao; Chai Liqun; Fan Changjiang

2010-01-01

In order to characterize and specify small-scale local wavefront deformation of optical component, a method based on Wigner distribution function has been proposed, which can describe wavefront deformation in spatial and spatial frequency domain. The relationship between Wigner distribution function and power spectral density is analyzed and thus the specification of small-scale local wavefront deformation is obtained by Wigner distribution function. Simulation and experiment demonstrate the effectiveness of the proposed method. The proposed method can not only identify whether the optical component meets the requirement of inertial confinement fusion (ICF), but also determine t he location where small-scale wavefront deformation is unqualified. Thus it provides an effective guide to the revision of unqualified optical components. (authors)

A reflectivity profilometer for the optical characterisation of graded reflectivity mirrors in the 250 nm - 1100 nm spectral region

International Nuclear Information System (INIS)

Colucci, Alessandro; Nichelatti, Enrico

1998-04-01

It's developed the prototype of an instrument that can be used for the optical characterisation of graded reflectivity mirrors at any wavelength in the spectral region from 250 nm to 1100 nm. The instrument utilises a high-pressure Xe arc lamp as light source. Light is spectrally filtered by means of a grating monochromator. The sample is illuminated with an image of the monochromator exit slit. After reflection from the sample, this image is projected onto a 1024-elements charge-coupled device linear array driven by a digital frame board and interfaced with a personal computer. It's tested the instrument accuracy by comparing measurement results with the corresponding ones obtained by means of a laser scanning technique. Measurement Rms repeatability has been estimated to be approximately of 0.8% [it

Cost-Effective Brillouin Optical Time-Domain Analysis Sensor Using a Single Optical Source and Passive Optical Filtering

Directory of Open Access Journals (Sweden)

H. Iribas

2016-01-01

Full Text Available We present a simplified configuration for distributed Brillouin optical time-domain analysis sensors that aims to reduce the cost of the sensor by reducing the number of components required for the generation of the two optical waves involved in the sensing process. The technique is based on obtaining the pump and probe waves by passive optical filtering of the spectral components generated in a single optical source that is driven by a pulsed RF signal. The optical source is a compact laser with integrated electroabsorption modulator and the optical filters are based on fiber Bragg gratings. Proof-of-concept experiments demonstrate 1 m spatial resolution over a 20 km sensing fiber with a 0.9 MHz precision in the measurement of the Brillouin frequency shift, a performance similar to that of much more complex setups. Furthermore, we discuss the factors limiting the sensor performance, which are basically related to residual spectral components in the filtering process.

COFFEE - Coherent Optical System Field Trial for Spectral Efficiency Enhancement

DEFF Research Database (Denmark)

Imran, Muhammad; Fresi, Francesco; Rommel, Simon

2016-01-01

The scope, aims, and contributions of the COFFEE project for spectral efficiency enhancement and market exposure are presented.......The scope, aims, and contributions of the COFFEE project for spectral efficiency enhancement and market exposure are presented....

Observation of Lorentzian lineshapes in the room temperature optical spectra of strongly coupled Jaggregate/metal hybrid nanostructures by linear two-dimensional optical spectroscopy

International Nuclear Information System (INIS)

Wang, Wei; Sommer, Ephraim; De Sio, Antonietta; Gross, Petra; Vogelgesang, Ralf; Lienau, Christoph; Vasa, Parinda

2014-01-01

We analyze the linear optical reflectivity spectra of a prototypical, strongly coupled metal/molecular hybrid nanostructure by means of a new experimental approach, linear two-dimensional optical spectroscopy. White-light, broadband spectral interferometry is used to measure amplitude and spectral phase of the sample reflectivity or transmission with high precision and to reconstruct the time structure of the electric field emitted by the sample upon impulsive excitation. A numerical analysis of this time-domain signal provides a two-dimensional representation of the coherent optical response of the sample as a function of excitation and detection frequency. The approach is used to study a nanostructure formed by depositing a thin J-aggregated dye layer on a gold grating. In this structure, strong coupling between excitons and surface plasmon polaritons results in the formation of hybrid polariton modes. In the strong coupling regime, Lorentzian lineshape profiles of different polariton modes are observed at room temperature. This is taken as an indication that the investigated strongly coupled polariton excitations are predominantly homogeneously broadened at room temperature. This new approach presents a versatile, simple and highly precise addition to nonlinear optical spectroscopic techniques for the analysis of line broadening phenomena. (paper)

Atlas of Atomic Spectral Lines of Neptunium Emitted by an Inductively Coupled Plasma

International Nuclear Information System (INIS)

DeKalb, E.L.; Edelson, M.C.

1987-01-01

Optical emission spectra from high-purity Np-237 were generated with a glovebox-enclosed inductively coupled plasma (ICP) source. Spectra covering the 230-700 nm wavelength range are presented along with general commentary on the methodology used in collecting the data. The Ames Laboratory Nuclear Safeguards and Security Program has been charged with the task of developing optical spectroscopic methods to analyze the composition of spent nuclear fuels. Such materials are highly radioactive even after prolonged 'cooling' and are chemically complex. Neptunium (Np) is a highly toxic by-product of nuclear power generation and is found, in low abundance, in spent nuclear fuels. This atlas of the optical emission spectrum of Np, as produced by an inductively coupled plasma (ICP) spectroscopic source, is part of a general survey of the ICP emission spectra of the actinide elements. The ICP emission spectrum of the actinides originates almost exclusively from the electronic relaxation of excited, singly ionized species. Spectral data on the Np ion emission spectrum (i.e., the Np II spectrum) have been reported by Tomkins and Fred (1) and Haaland (2). Tomkins and Fred excited the Np II spectrum with a Cu spark discharge and identified 114 Np lines in the 265.5 - 436.3 nm spectral range. Haaland, who corrected some spectral line misidentifications in the work of Tomkins and Fred, utilized an enclosed Au spark discharge to excite the Np II spectrum and reported 203 Np lines within the 265.4 - 461.0 nm wavelength range.

Fluorescence imaging spectrometer optical design

Science.gov (United States)

Taiti, A.; Coppo, P.; Battistelli, E.

2015-09-01

The optical design of the FLuORescence Imaging Spectrometer (FLORIS) studied for the Fluorescence Explorer (FLEX) mission is discussed. FLEX is a candidate for the ESA's 8th Earth Explorer opportunity mission. FLORIS is a pushbroom hyperspectral imager foreseen to be embarked on board of a medium size satellite, flying in tandem with Sentinel-3 in a Sun synchronous orbit at a height of about 815 km. FLORIS will observe the vegetation fluorescence and reflectance within a spectral range between 500 and 780 nm. Multi-frames acquisitions on matrix detectors during the satellite movement will allow the production of 2D Earth scene images in two different spectral channels, called HR and LR with spectral resolution of 0.3 and 2 nm respectively. A common fore optics is foreseen to enhance by design the spatial co-registration between the two spectral channels, which have the same ground spatial sampling (300 m) and swath (150 km). An overlapped spectral range between the two channels is also introduced to simplify the spectral coregistration. A compact opto-mechanical solution with all spherical and plane optical elements is proposed, and the most significant design rationales are described. The instrument optical architecture foresees a dual Babinet scrambler, a dioptric telescope and two grating spectrometers (HR and LR), each consisting of a modified Offner configuration. The developed design is robust, stable vs temperature, easy to align, showing very high optical quality along the whole field of view. The system gives also excellent correction for transverse chromatic aberration and distortions (keystone and smile).

Perspective and potential of smart optical materials

Science.gov (United States)

Choi, Sang H.; Duzik, Adam J.; Kim, Hyun-Jung; Park, Yeonjoon; Kim, Jaehwan; Ko, Hyun-U.; Kim, Hyun-Chan; Yun, Sungryul; Kyung, Ki-Uk

2017-09-01

The increasing requirements of hyperspectral imaging optics, electro/photo-chromic materials, negative refractive index metamaterial optics, and miniaturized optical components from micro-scale to quantum-scale optics have all contributed to new features and advancements in optics technology. Development of multifunctional capable optics has pushed the boundaries of optics into new fields that require new disciplines and materials to maximize the potential benefits. The purpose of this study is to understand and show the fundamental materials and fabrication technology for field-controlled spectrally active optics (referred to as smart optics) that are essential for future industrial, scientific, military, and space applications, such as membrane optics, filters, windows for sensors and probes, telescopes, spectroscopes, cameras, light valves, light switches, and flat-panel displays. The proposed smart optics are based on the Stark and Zeeman effects in materials tailored with quantum dot arrays and thin films made from readily polarizable materials via ferroelectricity or ferromagnetism. Bound excitonic states of organic crystals are also capable of optical adaptability, tunability, and reconfigurability. To show the benefits of smart optics, this paper reviews spectral characteristics of smart optical materials and device technology. Experiments testing the quantum-confined Stark effect, arising from rare earth element doping effects in semiconductors, and applied electric field effects on spectral and refractive index are discussed. Other bulk and dopant materials were also discovered to have the same aspect of shifts in spectrum and refractive index. Other efforts focus on materials for creating field-controlled spectrally smart active optics on a selected spectral range. Surface plasmon polariton transmission of light through apertures is also discussed, along with potential applications. New breakthroughs in micro scale multiple zone plate optics as a micro

Effect of Hydroxychloroquine on the Retinal Layers: A Quantitative Evaluation with Spectral-Domain Optical Coherence Tomography

Directory of Open Access Journals (Sweden)

Hasim Uslu

2016-01-01

Full Text Available Purpose. To evaluate the effect of hydroxychloroquine on retinal pigment epithelium- (RPE- Bruch’s membrane complex, photoreceptor outer segment, and macular ganglion cell-inner plexiform layer (GCIPL thicknesses using spectral-domain optical coherence tomography (SD-OCT. Methods. In this prospective case-control study, 51 eyes of 51 hydroxychloroquine patients and 30 eyes of 30 healthy subjects were included. High-quality images were obtained using a Cirrus HD-OCT with 5-line raster mode; the photoreceptor inner segment (IS and outer segment (OS, sum of the segments (IS + OS, and RPE-Bruch’s membrane complex were analyzed. Results. The thicknesses of the IS + OS and OS layers were significantly lower in the hydroxychloroquine subjects compared to the control subjects (P<0.05. RPE-Bruch’s membrane complex thicknesses were significantly higher in the hydroxychloroquine subjects than for those of the control subjects (P<0.05. The minimum and temporal-inferior macular GCIPL thicknesses were significantly different between the patients with hydroxychloroquine use and the control subjects (P=0.04 and P=0.03, resp.. Conclusions. The foveal photoreceptor OS thinning, loss of GCIPL, and RPE-Bruch’s membrane thickening were detected in patients with hydroxychloroquine therapy. This quantitative approach using SD-OCT images may have important implications to use as an early indicator of retinal toxicity without any visible signs of hydroxychloroquine retinopathy.

Characterisation of optical filters for broadband UVA radiometer

Science.gov (United States)

Alves, Luciana C.; Coelho, Carla T.; Corrêa, Jaqueline S. P. M.; Menegotto, Thiago; Ferreira da Silva, Thiago; Aparecida de Souza, Muriel; Melo da Silva, Elisama; Simões de Lima, Maurício; Dornelles de Alvarenga, Ana Paula

2016-07-01

Optical filters were characterized in order to know its suitability for use in broadband UVA radiometer head for spectral irradiance measurements. The spectral transmittance, the angular dependence and the spatial uniformity of the spectral transmittance of the UVA optical filters were investigated. The temperature dependence of the transmittance was also studied.

Optical label-controlled transparent metro-access network interface

DEFF Research Database (Denmark)

Osadchiy, Alexey Vladimirovich

This thesis presents results obtained during the course of my PhD research on optical signal routing and interfacing between the metropolitan and access segments of optical networks. Due to both increasing capacity demands and variety of emerging services types, new technological challenges...... control. Highlights of my research include my proposal and experimental proof of principle of an optical coherent detection based optical access network architecture providing support for a large number of users over a single distribution fiber; a spectral amplitude encoded label detection technique...... are arising for seamlessly interfacing metropolitan and access networks. Therefore, in this PhD project, I have analyzed those technological challenges and identified the key aspects to be addressed. I have also proposed and experimentally verified a number of solutions to metropolitan and access networks...

Imaging spectroscopy using embedded diffractive optical arrays

Science.gov (United States)

Hinnrichs, Michele; Hinnrichs, Bradford

2017-09-01

Pacific Advanced Technology (PAT) has developed an infrared hyperspectral camera based on diffractive optic arrays. This approach to hyperspectral imaging has been demonstrated in all three infrared bands SWIR, MWIR and LWIR. The hyperspectral optical system has been integrated into the cold-shield of the sensor enabling the small size and weight of this infrared hyperspectral sensor. This new and innovative approach to an infrared hyperspectral imaging spectrometer uses micro-optics that are made up of an area array of diffractive optical elements where each element is tuned to image a different spectral region on a common focal plane array. The lenslet array is embedded in the cold-shield of the sensor and actuated with a miniature piezo-electric motor. This approach enables rapid infrared spectral imaging with multiple spectral images collected and processed simultaneously each frame of the camera. This paper will present our optical mechanical design approach which results in an infrared hyper-spectral imaging system that is small enough for a payload on a small satellite, mini-UAV, commercial quadcopter or man portable. Also, an application of how this spectral imaging technology can easily be used to quantify the mass and volume flow rates of hydrocarbon gases. The diffractive optical elements used in the lenslet array are blazed gratings where each lenslet is tuned for a different spectral bandpass. The lenslets are configured in an area array placed a few millimeters above the focal plane and embedded in the cold-shield to reduce the background signal normally associated with the optics. The detector array is divided into sub-images covered by each lenslet. We have developed various systems using a different number of lenslets in the area array. Depending on the size of the focal plane and the diameter of the lenslet array will determine the number of simultaneous different spectral images collected each frame of the camera. A 2 x 2 lenslet array will image

Tunable optical setup with high flexibility for spectrally resolved coherent anti-Stokes Raman scattering microscopy

International Nuclear Information System (INIS)

Bergner, G; Akimov, D; Bartelt, H; Dietzek, B; Popp, J; Schlücker, S

2011-01-01

A simplified setup for coherent anti-Stokes Raman scattering (CARS) microscopy is introduced, which allows for recording CARS images with 30 cm -1 excitation bandwidth for probing Raman bands between 500 and 900 cm -1 with minimal requirements for alignment. The experimental arrangement is based on electronic switching between CARS images recorded at different Raman resonances by combining a photonic crystal fiber (PCF) as broadband light source and an acousto-optical programmable dispersive filter (AOPDF) as tunable wavelength filter. Such spatial light modulator enables selection of a narrow-band spectrum to yield high vibrational contrast and hence chemical contrast in the resultant CARS images. Furthermore, an experimental approach to reconstruct spectral information from CARS image contrast is introduced

Synthesis and spectral characterization of hydrazone derivative of furfural using experimental and DFT methods.

Science.gov (United States)

Babu, N Ramesh; Subashchandrabose, S; Ali Padusha, M Syed; Saleem, H; Erdoğdu, Y

2014-01-01

The Spectral Characterization of (E)-1-(Furan-2-yl) methylene)-2-(1-phenylvinyl) hydrazine (FMPVH) were carried out by using FT-IR, FT-Raman and UV-Vis., Spectrometry. The B3LYP/6-311++G(d,p) level of optimization has been performed on the title compound. The conformational analysis was performed for this molecule, in which the cis and trans conformers were studied for spectral characterization. The recorded spectral results were compared with calculated results. The optimized bond parameters of FMPVH molecule was compared with X-ray diffraction data of related molecule. To study the intra-molecular charge transfers within the molecule the Lewis (bonding) and Non-Lewis (anti-bonding) structural calculation was performed. The Non-linear optical behavior of the title compound was measured using first order hyperpolarizability calculation. The atomic charges were calculated and analyzed. Copyright © 2013 Elsevier B.V. All rights reserved.

Spectral ellipsometry of a nanodiamond composite

International Nuclear Information System (INIS)

Yastrebov, S. G.; Gordeev, S. K.; Garriga, M.; Alonso, I. A.; Ivanov-Omskii, V. I.

2006-01-01

Optical properties of a nanodiamond composite were analyzed by methods of spectral ellipsometry in the range of photon energies 1.4-5 eV, which are characteristic of π-π* transitions in amorphous carbon. The nanocomposite was synthesized by molding nanodiamond powder with subsequent binding of diamond nanoparticles by pyrocarbon formed as a result of the heterogeneous chemical reaction of methane decomposition. The dispersion curves of the imaginary and real parts of the dielectric function were reconstructed. It is shown that the imaginary part of the dielectric function can be represented as the sum of two components generated by the two types of π-π* optical transitions. The maximum contribution of the transitions of the first and second types manifests itself at energies of 2.6 and 5.6 eV, respectively, which correspond to peaks in optical density at 2.9 and 6.11 eV. It was established that the main specific features of the normalized optical density of the nanodiamond composite almost coincide with those for poly(para-phenylenevinylene). It was found that the energy of a σ + π plasmon of the pyrocarbon component of the nanodiamond composite is 24.2 eV. On the basis on this value, the pyrocarbon density matrix was estimated to be 2 g/cm 3 . Within the concepts of optimum filling of an elementary volume by carbon atoms in an amorphous material with such a density, the allotropic composition of the pyrocarbon matrix was restored

Optical radiation emitted by a silver surface bombarded by low-energy electrons

International Nuclear Information System (INIS)

Miserey, F.; Lebon, P.; Septier, A.; Trehin, F.; Beaugrand, C.

1975-01-01

Thick silver targets are obtained on flat glass discs by evaporation in a UHV cell (p -10 torr) and their optical coefficients measured by ellipsometry. A field-emission electron gun bombards a limited region of the target, corresponding to the entry pupil of a light spectrometer. Radiation emitted in the domain 250-600nm is analyzed for both normal and parallel polarizations. Spectral distributions of photons are obtained by using a very sensitive counting device including a multi channel analyzer. First experimental results concerning optical radiation generated by 6keV electrons are reported and compared to Transition Radiation and Bremsstrahlung theoretical spectra [fr

Study of the spectral width of intermode beats and optical spectrum of an actively mode-locked three-mirror semiconductor laser

International Nuclear Information System (INIS)

Zakharyash, Valerii F; Kashirsky, Aleksandr V; Klementyev, Vasilii M; Kuznetsov, Sergei A; Pivtsov, V S

2005-01-01

Various oscillation regimes of an actively mode-locked semiconductor laser are studied experimentally. Two types of regimes are found in which the minimal spectral width (∼3.5 kHz) of intermode beats is achieved. The width of the optical spectrum of modes is studied as a function of their locking and the feedback coefficients. The maximum width of the spectrum is ∼3.7 THz. (control of laser radiation parameters)

Structure-function relationships using spectral-domain optical coherence tomography: comparison with scanning laser polarimetry.

Science.gov (United States)

Aptel, Florent; Sayous, Romain; Fortoul, Vincent; Beccat, Sylvain; Denis, Philippe

2010-12-01

To evaluate and compare the regional relationships between visual field sensitivity and retinal nerve fiber layer (RNFL) thickness as measured by spectral-domain optical coherence tomography (OCT) and scanning laser polarimetry. Prospective cross-sectional study. One hundred and twenty eyes of 120 patients (40 with healthy eyes, 40 with suspected glaucoma, and 40 with glaucoma) were tested on Cirrus-OCT, GDx VCC, and standard automated perimetry. Raw data on RNFL thickness were extracted for 256 peripapillary sectors of 1.40625 degrees each for the OCT measurement ellipse and 64 peripapillary sectors of 5.625 degrees each for the GDx VCC measurement ellipse. Correlations between peripapillary RNFL thickness in 6 sectors and visual field sensitivity in the 6 corresponding areas were evaluated using linear and logarithmic regression analysis. Receiver operating curve areas were calculated for each instrument. With spectral-domain OCT, the correlations (r(2)) between RNFL thickness and visual field sensitivity ranged from 0.082 (nasal RNFL and corresponding visual field area, linear regression) to 0.726 (supratemporal RNFL and corresponding visual field area, logarithmic regression). By comparison, with GDx-VCC, the correlations ranged from 0.062 (temporal RNFL and corresponding visual field area, linear regression) to 0.362 (supratemporal RNFL and corresponding visual field area, logarithmic regression). In pairwise comparisons, these structure-function correlations were generally stronger with spectral-domain OCT than with GDx VCC and with logarithmic regression than with linear regression. The largest areas under the receiver operating curve were seen for OCT superior thickness (0.963 ± 0.022; P polarimetry, and was better expressed logarithmically than linearly. Measurements with these 2 instruments should not be considered to be interchangeable. Copyright © 2010 Elsevier Inc. All rights reserved.

The cloud radiation impact from optics simulation and airborne observation

Science.gov (United States)

Melnikova, Irina; Kuznetsov, Anatoly; Gatebe, Charles

2017-02-01

The analytical approach of inverse asymptotic formulas of the radiative transfer theory is used for solving inverse problems of cloud optics. The method has advantages because it does not impose strict constraints, but it is tied to the desired solution. Observations are accomplished in extended stratus cloudiness, above a homogeneous ocean surface. Data from NASA`s Cloud Absorption Radiometer (CAR) during two airborne experiments (SAFARI-2000 and ARCTAS-2008) were analyzed. The analytical method of inverse asymptotic formulas was used to retrieve cloud optical parameters (optical thickness, single scattering albedo and asymmetry parameter of the phase function) and ground albedo in all 8 spectral channels independently. The method is free from a priori restrictions and there is no links to parameters, and it has been applied to data set of different origin and geometry of observations. Results obtained from different airborne, satellite and ground radiative experiments appeared consistence and showed common features of values of cloud parameters and its spectral dependence (Vasiluev, Melnikova, 2004; Gatebe et al., 2014). Optical parameters, retrieved here, are used for calculation of radiative divergence, reflected and transmitted irradiance and heating rates in cloudy atmosphere, that agree with previous observational data.

Thin Film Solar Cells and their Optical Properties

Directory of Open Access Journals (Sweden)

Stanislav Jurecka

2006-01-01

Full Text Available In this work we report on the optical parameters of the semiconductor thin film for solar cell applications determination. The method is based on the dynamical modeling of the spectral reflectance function combined with the stochastic optimization of the initial reflectance model estimation. The spectral dependency of the thin film optical parameters computations is based on the optical transitions modeling. The combination of the dynamical modeling and the stochastic optimization of the initial theoretical model estimation enable comfortable analysis of the spectral dependencies of the optical parameters and incorporation of the microstructure effects on the solar cell properties. The results of the optical parameters ofthe i-a-Si thin film determination are presented.

Optical remote sensing

CERN Document Server

Prasad, Saurabh; Chanussot, Jocelyn

2011-01-01

Optical remote sensing relies on exploiting multispectral and hyper spectral imagery possessing high spatial and spectral resolutions respectively. These modalities, although useful for most remote sensing tasks, often present challenges that must be addressed for their effective exploitation. This book presents current state-of-the-art algorithms that address the following key challenges encountered in representation and analysis of such optical remotely sensed data: challenges in pre-processing images, storing and representing high dimensional data, fusing different sensor modalities, patter

Synthesis, spectral and third-order nonlinear optical properties of terpyridine Zn(II) complexes based on carbazole derivative with polyether group

Science.gov (United States)

Kong, Ming; Liu, Yanqiu; Wang, Hui; Luo, Junshan; Li, Dandan; Zhang, Shengyi; Li, Shengli; Wu, Jieying; Tian, Yupeng

2015-01-01

Four novel Zn(II) terpyridine complexes (ZnLCl2, ZnLBr2, ZnLI2, ZnL(SCN)2) based on carbazole derivative group were designed, synthesized and fully characterized. Their photophysical properties including absorption and one-photon excited fluorescence, two-photon absorption (TPA) and optical power limiting (OPL) were further investigated systematically and interpreted on the basis of theoretical calculations (TD-DFT). The influences of different solvents on the absorption and One-Photon Excited Fluorescence (OPEF) spectral behavior, quantum yields and the lifetime of the chromophores have been investigated in detail. The third-order nonlinear optical (NLO) properties were investigated by open/closed aperture Z-scan measurements using femtosecond pulse laser in the range from 680 to 1080 nm. These results revealed that ZnLCl2 and ZnLBr2 exhibited strong two-photon absorption and ZnLCl2 showed superior optical power limiting property.

Spectrally adjustable quasi-monochromatic radiance source based on LEDs and its application for measuring spectral responsivity of a luminance meter

International Nuclear Information System (INIS)

Hirvonen, Juha-Matti; Poikonen, Tuomas; Vaskuri, Anna; Kärhä, Petri; Ikonen, Erkki

2013-01-01

A spectrally adjustable radiance source based on light-emitting diodes (LEDs) has been constructed for spectral responsivity measurements of radiance and luminance meters. A 300 mm integrating sphere source with adjustable output port is illuminated using 30 thermally stabilized narrow-band LEDs covering the visible wavelength range of 380–780 nm. The functionality of the measurement setup is demonstrated by measuring the relative spectral responsivities of a luminance meter and a photometer head with cosine-corrected input optics. (paper)

Digital dynamic amplitude-frequency spectra analyzer

International Nuclear Information System (INIS)

Kalinnikov, V.A.; )

2006-01-01

The spectra analyzer is intended for the dynamic spectral analysis of signals physical installations and noise filtering. The recurrence Fourier transformation algorithm is used in the digital dynamic analyzer. It is realized on the basis of the fast logic FPGA matrix and the special signal ADSP microprocessor. The discretization frequency is 2 kHz-10 MHz. The number of calculated spectral coefficients is not less 512. The functional fast-action is 20 ns [ru

Radiative modeling and characterization of aerosol plumes hyper-spectral imagery

International Nuclear Information System (INIS)

Alakian, A.

2008-03-01

This thesis aims at characterizing aerosols from plumes (biomass burning, industrial discharges, etc.) with hyper-spectral imagery. We want to estimate the optical properties of emitted particles and also their micro-physical properties such as number, size distribution and composition. To reach our goal, we have built a forward semi-analytical model, named APOM (Aerosol Plume Optical Model), which allows to simulate the radiative effects of aerosol plumes in the spectral range [0,4-2,5 μm] for nadir viewing sensors. Mathematical formulation and model coefficients are obtained from simulations performed with the radiative transfer code COMANCHE. APOM is assessed on simulated data and proves to be accurate with modeling errors between 1% and 3%. Three retrieval methods using APOM have been developed: L-APOM, M-APOM and A-APOM. These methods take advantage of spectral and spatial dimensions in hyper-spectral images. L-APOM and M-APOM assume a priori knowledge on particles but can estimate their optical and micro-physical properties. Their performances on simulated data are quite promising. A-APOM method does not require any a priori knowledge on particles but only estimates their optical properties. However, it still needs improvements before being usable. On real images, inversion provides satisfactory results for plumes above water but meets some difficulties for plumes above vegetation, which underlines some possibilities of improvement for the retrieval algorithm. (author)

Polymer-Optical-Fiber Lasers and Amplifiers Doped with Organic Dyes

Directory of Open Access Journals (Sweden)

Joseba Zubia

2011-07-01

Full Text Available Polymer optical fibers (POFs doped with organic dyes can be used to make efficient lasers and amplifiers due to the high gains achievable in short distances. This paper analyzes the peculiarities of light amplification in POFs through some experimental data and a computational model capable of carrying out both power and spectral analyses. We investigate the emission spectral shifts and widths and on the optimum signal wavelength and pump power as functions of the fiber length, the fiber numerical aperture and the radial distribution of the dopant. Analyses for both step-index and graded-index POFs have been done.

The determination of the optical selectivity of W/Al2O3 layers after unloading at 500 C by means of spectral ellipsometry between 0.25 and 25 μm

International Nuclear Information System (INIS)

Djahanbakhsh, M.

1997-01-01

Optically selective W/Al 2 O 3 cermet layers were fabricated in the CVD and sputtering procedure. The study of the optical property of the W/Al 2 O 3 cermet layers was measured with two ellipsometers spectrally from 250 to 1700 nm and from 2000 to 25000 nm

The B3-VLA CSS sample. VIII. New optical identifications from the Sloan Digital Sky Survey The ultraviolet-optical spectral energy distribution of the young radio sources

Science.gov (United States)

Fanti, C.; Fanti, R.; Zanichelli, A.; Dallacasa, D.; Stanghellini, C.

2011-04-01

Context. Compact steep-spectrum radio sources and giga-hertz peaked spectrum radio sources (CSS/GPS) are generally considered to be mostly young radio sources. In recent years we studied at many wavelengths a sample of these objects selected from the B3-VLA catalog: the B3-VLA CSS sample. Only ≈60% of the sources were optically identified. Aims: We aim to increase the number of optical identifications and study the properties of the host galaxies of young radio sources. Methods: We cross-correlated the CSS B3-VLA sample with the Sloan Digital Sky Survey (SDSS), DR7, and complemented the SDSS photometry with available GALEX (DR 4/5 and 6) and near-IR data from UKIRT and 2MASS. Results: We obtained new identifications and photometric redshifts for eight faint galaxies and for one quasar and two quasar candidates. Overall we have 27 galaxies with SDSS photometry in five bands, for which we derived the ultraviolet-optical spectral energy distribution (UV-O-SED). We extended our investigation to additional CSS/GPS selected from the literature. Most of the galaxies show an excess of ultra-violet (UV) radiation compared with the UV-O-SED of local radio-quiet ellipticals. We found a strong dependence of the UV excess on redshift and analyzed it assuming that it is generated either from the nucleus (hidden quasar) or from a young stellar population (YSP). We also compare the UV-O-SEDs of our CSS/GPS sources with those of a selection of large size (LSO) powerful radio sources from the literature. Conclusions: If the major process of the UV excess is caused by a YSP, our conclusion is that it is the result of the merger process that also triggered the onset of the radio source with some time delay. We do not see evidence for a major contribution from a YSP triggered by the radio sources itself. Appendices A-G are only available in electronic form at http://www.aanda.org

Effect of input spectrum on the spectral switch characteristics in a white-light Michelson interferometer.

Science.gov (United States)

Brundavanam, Maruthi M; Viswanathan, Nirmal K; Rao, D Narayana

2009-12-01

We report here a detailed experimental study to demonstrate the effect of source spectral characteristics such as spectral bandwidth (Deltalambda), peak wavelength (lambda(0)), and shape of the spectrum on the spectral shifts and spectral switches measured due to temporal correlation in a white-light Michelson interferometer operated in the spectral domain. Behavior of the spectral switch characteristics such as the switch position, switch amplitude, and switch symmetry are discussed in detail as a function of optical path difference between the interfering beams. The experimental results are compared with numerical calculations carried out using interference law in the spectral domain with modified source spectral characteristics. On the basis of our results we feel that our study is of critical importance in the selection of source spectral characteristics to further improve the longitudinal resolution or the measurement sensitivity in spectral-domain optical coherence tomography and microscopy.

Effect of H+ implantation on the optical properties of semi-insulating GaAs crystals in the IR spectral region

International Nuclear Information System (INIS)

Klyui, N. I.; Lozinskii, V. B.; Liptuga, A. I.; Dikusha, V. N.; Oksanych, A. P.; Kogdas’, M. G.; Perekhrest, A. L.; Pritchin, S. E.

2017-01-01

The optical properties of semi-insulating GaAs crystals subjected to multienergy hydrogen-ion implantation and treatment in a high-frequency electromagnetic field are studied in the infrared spectral region. It is established that such combined treatment provides a means for substantially increasing the transmittance of GaAs crystals to values characteristic of crystals of high optical quality. On the basis of analysis of the infrared transmittance and reflectance data, Raman spectroscopy data, and atomic-force microscopy data on the surface morphology of the crystals, a physical model is proposed to interpret the effects experimentally observed in the crystals. The model takes into account the interaction of radiation defects with the initial structural defects in the crystals as well as the effect of compensation of defect centers by hydrogen during high-frequency treatment.

Self-referencing, spectrally, or spatially encoded spectral interferometry for the complete characterization of attosecond electromagnetic pulses

International Nuclear Information System (INIS)

Cormier, Eric; Walmsley, Ian A.; Wyatt, Adam S.; Corner, Laura; Kosik, Ellen M.; DiMauro, Louis F.

2005-01-01

We propose a method for the complete characterization of attosecond duration electromagnetic pulses produced by high harmonic generation in an atomic gas. Our method is based on self-referencing spectral interferometry of two spectrally sheared extreme ultraviolet pulses, which is achieved by pumping the harmonic source with two sheared optical driving pulses. The resulting interferogram contains sufficient information to completely reconstruct the temporal behavior of the electric field. We demonstrate that such a method is feasible, and outline two possible experimental configurations

Spectral ellipsometry of nanodiamond composite

International Nuclear Information System (INIS)

Yastrebov, S.G.; Ivanov-Omskij, V.I.; Gordeev, S.K.; Garriga, M.; Alonso, I.A.

2006-01-01

Methods of spectral ellipsometry were applied for analysis of optical properties of nanodiamond based composite in spectral region 1.4-5 eV. The nanocomposite was synthesized by molding of ultradispersed nanodiamond powder in the course of heterogeneous chemical reaction of decomposition of methane, forming pyrocarbon interconnecting nanodiamond grains. The energy of σ + π plasmon of pyrocarbon component of nanodiamond composite was restored which proves to be ∼ 24 eV; using this value, an estimation was done of pyrocarbon matrix density, which occurs to be 2 g/cm 3 [ru

Structure-function relationships with spectral-domain optical coherence tomography retinal nerve fiber layer and optic nerve head measurements.

Science.gov (United States)

Pollet-Villard, Frédéric; Chiquet, Christophe; Romanet, Jean-Paul; Noel, Christian; Aptel, Florent

2014-05-02

To evaluate the regional structure-function relationship between visual field sensitivity and retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) measurements using spectral-domain optical coherence tomography (SD-OCT). Prospective cross-sectional study conducted on patients with glaucoma, suspected glaucoma, and healthy subjects. Eyes were tested on Cirrus OCT and standard achromatic perimetry. RNFL thickness of 12 peripapillary 30° sectors, neuroretinal rim thickness extracted from 36 neuroretinal rim scans, and Bruch membrane opening minimum rim width (BMO-MRW)-a recently defined parameter-extracted from 36 neuroretinal rim scans were obtained. Correlations between peripapillary RNFL thickness, neuroretinal rim thickness, all six sectors of BMO-MRW, and visual field sensitivity in the six corresponding areas were evaluated using logarithmic regression analysis. Receiver operating curve areas were calculated for each RNFL, ONH, and macular ganglion cell analysis parameter. We included 142 eyes of 142 subjects. The correlations (r(2)) between RNFL thickness, Cirrus-based neuroretinal rim thickness, BMO-MRW and visual field sensitivity ranged from 0.07 to 0.60, 0.15 to 0.49, and 0.24 to 0.66, respectively. The structure-function correlations were stronger with BMO-MRW than with Cirrus-based neuroretinal rim thickness. The largest areas under the receiver operating curve were seen for rim area (0.926 [95% confidence interval 0.875, 0.977]; P function relationship was significantly stronger with BMO-MRW than other ONH SD-OCT parameters. The best diagnostic capabilities were seen with rim area and average RNFL.

Spectral Signatures of Surface Materials in Pig Buildings

DEFF Research Database (Denmark)

Zhang, GuoQiang; Strøm, Jan; Blanke, Mogens

2006-01-01

. In this study, the optical properties of different types of surfaces to be cleaned and the dirt found in finishing pig units were investigated in the visual and the near infrared (VIS-NIR) optical range. Four types of commonly used materials in pig buildings, i.e. concrete, plastic, wood and steel were applied...... and after high-pressure water cleaning. The spectral signatures of the surface materials and dirt attached to the surfaces showed that it is possible to make discrimination and hence to classify areas that are visually clean. When spectral bands 450, 600, 700 and 800 nm are chosen, there are at least two...

Time domain optical spectrometry with fiber optic waveguides

International Nuclear Information System (INIS)

Whitten, W.B.

1983-01-01

Spectrometers which use optical fibers to obtain time domain spectral dispersion are reviewed. Pulse transmission through fiber optic waveguides is discussed and the basic requirements for sources and detectors are given. Multiplex spectrometry and time-of-flight spectrometry are then discussed. Resolution, fiber requirements, instrumentation and specific spectrometers are presented

Development of a spectral analyzer for radio-frequencies; Etude et realisation d'un analyseur de spectres pour radio-frequences

Energy Technology Data Exchange (ETDEWEB)

Bourbigot, J [Commission a l' Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1967-04-01

This report describes an apparatus designed to show on the screen of a cathode ray tube the amplitude and frequency distribution of the spectral components of a given signal. The frequency range is from 5 kHz to 25 MHz. Two fundamental elements are used in the development of this apparatus, a ferrite and a ring modulator. The basic properties of these elements are studied and discussed. A theoretical study for the determination of the fundamental parameters of the analyzer is presented in the Appendix. (author) [French] On decrit un appareil qui permet de representer sur l'ecran d'un tube a rayons cathodiques la distribution en frequence et en amplitude des composantes spectrales d'un signal donne. Il fonctionne dans la gamme de frequences s'etendant de 5 kHz a 25 MHz. Deux elements interviennent fondamentalement dans la realisation de cet appareil: un echantillon de ferrite et un modulateur en anneau. Des proprietes particulieres de ces elements sont etudiees et discutees. En annexe une theorie s'appliquant a la determination de parametres fondamentaux de l'analyseur est developpee. (auteur)

Growth, spectral, dielectric and antimicrobial studies on 4-piperidinium carboxylamide picrate crystals

Science.gov (United States)

Dhanabal, T.; Tharanitharan, V.; Amirthaganesan, G.; Dhandapani, M.

2014-07-01

Single crystal of 4-piperidinium carboxylamide picrate was grown by slow evaporation solution growth technique at ambient temperature. The average dimensions of grown crystal were 0.7 × 0.3 × 0.2 cm3. The solubility of the compound was analyzed using methanol and acetone. Optical property of the compound was ascertained by UV-visible absorption spectral study. The sharp and well defined Bragg peaks observed in the powder X-ray diffraction pattern confirm its crystallinity. The different kinds of protons and carbons in the compound were confirmed by 1H and 13C NMR spectral analyses. The presence of various functional groups in the compound was assigned through polarized Raman spectral study. The mechanical property of the crystal was measured by Vicker's microhardness test and the compound was found to be soft material. The dielectric constant and dielectric loss of the crystal decrease with increase in frequency. The antibacterial and antifungal activities of the crystal were studied by disc diffusion method and found that the compound shows good inhibition efficiency against various bacteria and fungi species.

Morphometric analysis of fovea with spectral-domain optical coherence tomography and visual outcome postsurgery for retinal detachment

Directory of Open Access Journals (Sweden)

Manish Nagpal

2014-01-01

Full Text Available Purpose: The purpose of this study was to correlate the postoperative best-corrected visual acuity (BCVA with spectral-domain optical coherence tomography (SD-OCT findings in fovea involving rhegmatogenous retinal detachment (RRD surgery. Materials and Methods: Thirty eyes with preoperative fovea-involving RRD, who underwent scleral buckling (SB (6 eyes and pars plana vitrectomy (PPV (19 eyes and combined SB and PPV (5 eyes were recruited. Patients underwent clinical examination and SD-OCT scan of fovea preoperatively and at 30 days and 90 days postoperatively. The correlations between SD-OCT findings and BCVA were analyzed. Results: Inner segment/outer segment (IS/OS junction integrity was the indicator of better BCVA at 30 days and 90 days (P = 0.0002 and P = 0.0003, respectively whereas outer retinal corrugation (ORC was related to worse BCVA at 30 days and 90 days (P = 0.001. External limiting membrane did not have a co-relation with visual outcome, but cystoid macular edema showed co-relation at 90 days (P = 0.047. All eyes of SB and 3 eyes of PPV had a minimal subfoveal fluid at 30 days follow-up that had no effect on visual acuity. All retinas were attached at final follow-up. Conclusion: IS/OS junction integrity and ORC may be important predictors of postoperative visual outcome after anatomically successful RRD surgery.

Optical properties of InGaAs/InGaAlAs quantum wells for the 1520–1580 nm spectral range

Energy Technology Data Exchange (ETDEWEB)

Gladyshev, A. G., E-mail: andrey.gladyshev@connector-optics.com; Novikov, I. I.; Karachinsky, L. Ya.; Denisov, D. V. [Connector Optics OOO (Russian Federation); Blokhin, S. A.; Blokhin, A. A.; Nadtochiy, A. M. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Kurochkin, A. S. [St. Petersburg National Research University of Information Technologies, Mechanics, and Optics (Russian Federation); Egorov, A. Yu. [Connector Optics OOO (Russian Federation)

2016-09-15

The optical properties of elastically strained semiconductor heterostructures with InGaAs/InGaAlAs quantum wells (QWs), intended for use in the formation of the active region of lasers emitting in the spectral range 1520–1580 nm, are studied. Active regions with varied lattice mismatch between the InGaAs QWs and the InP substrate are fabricated by molecular beam epitaxy. The maximum lattice mismatch for the InGaAs QWs is +2%. The optical properties of the elastically strained InGaAlAs/InGaAs/InP heterostructures are studied by the photoluminescence method in the temperature range from 20 to 140°C at various power densities of the excitation laser. Investigation of the optical properties of InGaAlAs/InGaAs/InP experimental samples confirms the feasibility of using the developed elastically strained heterostructures for the fabrication of active regions for laser diodes with high temperature stability.

Adaptive Spectral Doppler Estimation

DEFF Research Database (Denmark)

Gran, Fredrik; Jakobsson, Andreas; Jensen, Jørgen Arendt

2009-01-01

. The methods can also provide better quality of the estimated power spectral density (PSD) of the blood signal. Adaptive spectral estimation techniques are known to pro- vide good spectral resolution and contrast even when the ob- servation window is very short. The 2 adaptive techniques are tested......In this paper, 2 adaptive spectral estimation techniques are analyzed for spectral Doppler ultrasound. The purpose is to minimize the observation window needed to estimate the spectrogram to provide a better temporal resolution and gain more flexibility when designing the data acquisition sequence...... and compared with the averaged periodogram (Welch’s method). The blood power spectral capon (BPC) method is based on a standard minimum variance technique adapted to account for both averaging over slow-time and depth. The blood amplitude and phase estimation technique (BAPES) is based on finding a set...

SpectralNET – an application for spectral graph analysis and visualization

Directory of Open Access Journals (Sweden)

Schreiber Stuart L

2005-10-01

Full Text Available Abstract Background Graph theory provides a computational framework for modeling a variety of datasets including those emerging from genomics, proteomics, and chemical genetics. Networks of genes, proteins, small molecules, or other objects of study can be represented as graphs of nodes (vertices and interactions (edges that can carry different weights. SpectralNET is a flexible application for analyzing and visualizing these biological and chemical networks. Results Available both as a standalone .NET executable and as an ASP.NET web application, SpectralNET was designed specifically with the analysis of graph-theoretic metrics in mind, a computational task not easily accessible using currently available applications. Users can choose either to upload a network for analysis using a variety of input formats, or to have SpectralNET generate an idealized random network for comparison to a real-world dataset. Whichever graph-generation method is used, SpectralNET displays detailed information about each connected component of the graph, including graphs of degree distribution, clustering coefficient by degree, and average distance by degree. In addition, extensive information about the selected vertex is shown, including degree, clustering coefficient, various distance metrics, and the corresponding components of the adjacency, Laplacian, and normalized Laplacian eigenvectors. SpectralNET also displays several graph visualizations, including a linear dimensionality reduction for uploaded datasets (Principal Components Analysis and a non-linear dimensionality reduction that provides an elegant view of global graph structure (Laplacian eigenvectors. Conclusion SpectralNET provides an easily accessible means of analyzing graph-theoretic metrics for data modeling and dimensionality reduction. SpectralNET is publicly available as both a .NET application and an ASP.NET web application from http://chembank.broad.harvard.edu/resources/. Source code is

Optical spectral characterization of leaves for endemic species from La Primavera forest

Science.gov (United States)

Barragán, R. C.; Strojnik, Marija; Rodríguez-Rivas, Antonio; Garcia-Torales, G.; González, Francisco Javier

2017-09-01

La Primavera forest is the main climate regulator in the metropolitan area of Guadalajara, the second most populated megalopolis in Mexico with approximately 4.4 million people. This forest area has been a focus of fires in the last decade and it is deteriorating the quality of life of the inhabitants. Leaves from the endemic forest provide information about their biochemical composition and physiology. This information is enclosed in the spectral range of the visible band to the middle infrared (400 nm at 2500 nm). In this paper we examine the reflectance of six endemic species leaves of La Primavera forest, considering the measurement in fresh and dry samples. Measurements will be obtained with a Vis-NIR spectrometer that uses a calibrated light source. A formal collection of the optical properties of tree leaves in La Primavera forest does not exist, but it is important to classify about the type of vegetation in the area. In addition, it will provide information to generate vegetation inventories, provide data to the forest fire prevention systems, pest control and erosion in the area.

The effect of optical substrates on micro-FTIR analysis of single mammalian cells.

Science.gov (United States)

Wehbe, Katia; Filik, Jacob; Frogley, Mark D; Cinque, Gianfelice

2013-02-01

The study of individual cells with infrared (IR) microspectroscopy often requires living cells to be cultured directly onto a suitable substrate. The surface effect of the specific substrates on the cell growth-viability and associated biochemistry-as well as on the IR analysis-spectral interference and optical artifacts-is all too often ignored. Using the IR beamline, MIRIAM (Diamond Light Source, UK), we show the importance of the substrate used for IR absorption spectroscopy by analyzing two different cell lines cultured on a range of seven optical substrates in both transmission and reflection modes. First, cell viability measurements are made to determine the preferable substrates for normal cell growth. Successively, synchrotron radiation IR microspectroscopy is performed on the two cell lines to determine any genuine biochemically induced changes or optical effect in the spectra due to the different substrates. Multivariate analysis of spectral data is applied on each cell line to visualize the spectral changes. The results confirm the advantage of transmission measurements over reflection due to the absence of a strong optical standing wave artifact which amplifies the absorbance spectrum in the high wavenumber regions with respect to low wavenumbers in the mid-IR range. The transmission spectra reveal interference from a more subtle but significant optical artifact related to the reflection losses of the different substrate materials. This means that, for comparative studies of cell biochemistry by IR microspectroscopy, it is crucial that all samples are measured on the same substrate type.

Magnetic Field Sensing Based on Bi-Tapered Optical Fibers Using Spectral Phase Analysis.

Science.gov (United States)

Herrera-Piad, Luis A; Haus, Joseph W; Jauregui-Vazquez, Daniel; Sierra-Hernandez, Juan M; Estudillo-Ayala, Julian M; Lopez-Dieguez, Yanelis; Rojas-Laguna, Roberto

2017-10-20

A compact, magnetic field sensor system based on a short, bi-tapered optical fiber (BTOF) span lying on a magnetic tape was designed, fabricated, and characterized. We monitored the transmission spectrum from a broadband light source, which displayed a strong interference signal. After data collection, we applied a phase analysis of the interference optical spectrum. We here report the results on two fabricated, BTOFs with different interference spectrum characteristics; we analyzed the signal based on the interference between a high-order modal component and the core fiber mode. The sensor exhibited a linear response for magnetic field increments, and we achieved a phase sensitivity of around 0.28 rad/mT. The sensing setup presented remote sensing operation and low-cost transducer magnetic material.

Magnetic Field Sensing Based on Bi-Tapered Optical Fibers Using Spectral Phase Analysis

Directory of Open Access Journals (Sweden)

Luis A. Herrera-Piad

2017-10-01

Full Text Available A compact, magnetic field sensor system based on a short, bi-tapered optical fiber (BTOF span lying on a magnetic tape was designed, fabricated, and characterized. We monitored the transmission spectrum from a broadband light source, which displayed a strong interference signal. After data collection, we applied a phase analysis of the interference optical spectrum. We here report the results on two fabricated, BTOFs with different interference spectrum characteristics; we analyzed the signal based on the interference between a high-order modal component and the core fiber mode. The sensor exhibited a linear response for magnetic field increments, and we achieved a phase sensitivity of around 0.28 rad/mT. The sensing setup presented remote sensing operation and low-cost transducer magnetic material.

Advances in estimation methods of vegetation water content based on optical remote sensing techniques

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

Quantitative estimation of vegetation water content(VWC) using optical remote sensing techniques is helpful in forest fire as-sessment,agricultural drought monitoring and crop yield estimation.This paper reviews the research advances of VWC retrieval using spectral reflectance,spectral water index and radiative transfer model(RTM) methods.It also evaluates the reli-ability of VWC estimation using spectral water index from the observation data and the RTM.Focusing on two main definitions of VWC-the fuel moisture content(FMC) and the equivalent water thickness(EWT),the retrieval accuracies of FMC and EWT using vegetation water indices are analyzed.Moreover,the measured information and the dataset are used to estimate VWC,the results show there are significant correlations among three kinds of vegetation water indices(i.e.,WSI,NDⅡ,NDWI1640,WI/NDVI) and canopy FMC of winter wheat(n=45).Finally,the future development directions of VWC detection based on optical remote sensing techniques are also summarized.

Hemispherical-field-of-view, nonimaging narrow-band spectral filter

Science.gov (United States)

Miles, R. B.; Webb, S. G.; Griffith, E. L.

1981-01-01

Two compound parabolic concentrators are used to create a 180-deg-field-of-view spectral filter. The collection optics are reflective and are designed to collimate the light through a multilayer interference filter and then to refocus it onto an optical detector. Assuming unit reflectance and no loss through the optical filter, this device operates at the thermodynamic collection limit.

Laser linewidth narrowing using transient spectral hole burning

Energy Technology Data Exchange (ETDEWEB)

Thiel, Charles W.; Cone, Rufus L. [Department of Physics, Montana State University, Bozeman, MT 59715 (United States); Böttger, Thomas, E-mail: tbottger@usfca.edu [Department of Physics and Astronomy, 2130 Fulton Street, University of San Francisco, San Francisco, CA 94117 (United States)

2014-08-01

We demonstrate significant narrowing of laser linewidths by high optical density materials with inhomogeneously broadened absorption. As a laser propagates through the material, the nonlinear spectral hole burning process causes a progressive self-filtering of the laser spectrum, potentially reaching values less than the homogeneous linewidth. The transient spectral hole dynamically adjusts itself to the instantaneous frequency of the laser, passively suppressing laser phase noise and side modes over the entire material absorption bandwidth without the need for electronic or optical feedback to the laser. Wide bandwidth laser phase noise suppression was demonstrated using Er{sup 3+} doped Y{sub 2}SiO{sub 5} and LiNbO{sub 3} at 1.5 μm by employing time-delayed self-heterodyne detection of an external cavity diode laser to study the spectral narrowing effect. Our method is not restricted to any particular wavelength or laser system and is attractive for a range of applications where ultra-low phase noise sources are required. - Highlights: • We demonstrate significant laser linewidths narrowing by high optical density materials. • Nonlinear spectral hole burning causes progressive self-filtering of laser spectrum. • Filter dynamically adjusts itself to the instantaneous frequency of the laser. • Demonstrated at 1.5 μm in Er{sup 3+} doped Y{sub 2}SiO{sub 5} and LiNbO{sub 3}. • Linewidth filtering is not restricted to any particular wavelength or laser system.

Performance of highly connected photonic switching lossless metro-access optical networks

Science.gov (United States)

Martins, Indayara Bertoldi; Martins, Yara; Barbosa, Felipe Rudge

2018-03-01

The present work analyzes the performance of photonic switching networks, optical packet switching (OPS) and optical burst switching (OBS), in mesh topology of different sizes and configurations. The "lossless" photonic switching node is based on a semiconductor optical amplifier, demonstrated and validated with experimental results on optical power gain, noise figure, and spectral range. The network performance was evaluated through computer simulations based on parameters such as average number of hops, optical packet loss fraction, and optical transport delay (Am). The combination of these elements leads to a consistent account of performance, in terms of network traffic and packet delivery for OPS and OBS metropolitan networks. Results show that a combination of highly connected mesh topologies having an ingress e-buffer present high efficiency and throughput, with very low packet loss and low latency, ensuring fast data delivery to the final receiver.

Topography description of thin films by optical Fourier Transform

International Nuclear Information System (INIS)

Jaglarz, Janusz

2008-01-01

In this work, the main problems concerning the scattering of light by real surfaces and films are presented in view of results obtained with the bidirectional reflection distribution function (BRDF) method and optical profilometry (OP). The BRDF and OP studies, being complementary to the atomic force microscopy (AFM), allow one to get information about surface topography. From the optical data, the surface power spectral density (PSD) functions for absorbing and transparent rough films have been found. Both functions have been evaluated from the Fourier transform (FT) of the surface profiles. The usefulness of BRDF-and OP methods in characterization of real surfaces is demonstrated when analyzing the optical data obtained for metallic TiN-and organic PVK thin films deposited on various substrates

Topography description of thin films by optical Fourier Transform

Energy Technology Data Exchange (ETDEWEB)

Jaglarz, Janusz [Institute of Physics, Cracow University of Technology, ul. Podchoraz.ych 1, 30-084 Krakow (Poland)], E-mail: pujaglar@cyfronet.krakow.pl

2008-09-30

In this work, the main problems concerning the scattering of light by real surfaces and films are presented in view of results obtained with the bidirectional reflection distribution function (BRDF) method and optical profilometry (OP). The BRDF and OP studies, being complementary to the atomic force microscopy (AFM), allow one to get information about surface topography. From the optical data, the surface power spectral density (PSD) functions for absorbing and transparent rough films have been found. Both functions have been evaluated from the Fourier transform (FT) of the surface profiles. The usefulness of BRDF-and OP methods in characterization of real surfaces is demonstrated when analyzing the optical data obtained for metallic TiN-and organic PVK thin films deposited on various substrates.

Studies on the growth aspects, structural, thermal, dielectric and third order nonlinear optical properties of solution grown 4-methylpyridinium p-nitrophenolate single crystal

Science.gov (United States)

Devi, S. Reena; Kalaiyarasi, S.; Zahid, I. MD.; Kumar, R. Mohan

2016-11-01

An ionic organic optical crystal of 4-methylpyridinium p-nitrophenolate was grown from methanol by slow evaporation method at ambient temperature. Powder and single crystal X-ray diffraction studies revealed the crystal system and its crystalline perfection. The rocking curve recorded from HRXRD study confirmed the crystal quality. FTIR spectral analysis confirmed the functional groups present in the title compound. UV-visible spectral study revealed the optical window and band gap of grown crystal. The thermal, electrical and surface laser damage threshold properties of harvested crystal were examined by using TGA/DTA, LCR/Impedance Analyzer and Nd:YAG laser system respectively. The third order nonlinear optical property of grown crystal was elucidated by Z-scan technique.

Spectral-domain optical coherence tomography of macula in myopia.

Science.gov (United States)

Choovuthayakorn, Janejit; Laowong, Taksaorn; Watanachai, Nawat; Patikulsila, Direk; Chaikitmongkol, Voraporn

2016-06-01

The aim of this study is to determine the associations between regional macular thickness and gender, age, axial length, and degree of myopia in young and middle-aged healthy myopic eyes. One hundred and seventy-one subjects with -0.5 diopters of myopia or worse underwent prospective macular thickness measurement by Spectralis spectral-domain optical coherence tomography. Subjects' mean age was 32.40 ± 8.25 years (range 18 to 49 years), with 45 % being male. The mean degree of myopia was -4.57 ± 3.52 diopters, with a mean axial length of 25.09 ± 1.67 mm. Multivariate regression analysis demonstrated significantly thicker central (mean 9.13 µm thicker) and inner subfields (mean 8.55 µm thicker) in males (P values were <0.001 and 0.002, respectively). In addition, in both genders, for each millimeter of increased axial length, the central subfield thickness increased by 2.11 µm, the inner subfield decreased by 2.25 µm, and the outer subfield decreased by 3.62 µm (P values were 0.010, <0.001, and <0.001, respectively). Factors including gender and axial length affect baseline regional macular thickness in young and middle-age myopic subjects. The central subfield and inner subfield were affected by both gender and axial length, while the outer subfield was affected only by axial length. The macular thickness of myopic subjects with macular disease should be interpreted in light of these factors.

Observation and analysis of water inherent optical properties

Science.gov (United States)

Sun, Deyong; Li, Yunmei; Le, Chengfeng; Huang, Changchun

2008-03-01

Inherent optical property is an important part of water optical properties, and is the foundation of water color analytical model establishment. Through quantity filter technology (QFT) and backscattering meter BB9 (WETlabs Inc), absorption coefficients of CDOM, total suspended minerals and backscattering coefficients of total suspended minerals had been observed in Meiliang Bay of Taihu lake at summer and winter respectively. After analyzing the spectral characteristics of absorption and backscattering coefficients, the differences between two seasons had been illustrated adequately, and the reasons for the phenomena, which are related to the changes of water quality coefficient, had also been explained. So water environment states can be reflected by inherent optical properties. In addition, the relationship models between backscattering coefficients and suspended particle concentrations had been established, which can support coefficients for analytical models.

Atmospheric turbulence profiling with unknown power spectral density

Science.gov (United States)

Helin, Tapio; Kindermann, Stefan; Lehtonen, Jonatan; Ramlau, Ronny

2018-04-01

Adaptive optics (AO) is a technology in modern ground-based optical telescopes to compensate for the wavefront distortions caused by atmospheric turbulence. One method that allows to retrieve information about the atmosphere from telescope data is so-called SLODAR, where the atmospheric turbulence profile is estimated based on correlation data of Shack-Hartmann wavefront measurements. This approach relies on a layered Kolmogorov turbulence model. In this article, we propose a novel extension of the SLODAR concept by including a general non-Kolmogorov turbulence layer close to the ground with an unknown power spectral density. We prove that the joint estimation problem of the turbulence profile above ground simultaneously with the unknown power spectral density at the ground is ill-posed and propose three numerical reconstruction methods. We demonstrate by numerical simulations that our methods lead to substantial improvements in the turbulence profile reconstruction compared to the standard SLODAR-type approach. Also, our methods can accurately locate local perturbations in non-Kolmogorov power spectral densities.

Ability of spectral domain optical coherence tomography peripapillary retinal nerve fiber layer thickness measurements to identify early glaucoma

Directory of Open Access Journals (Sweden)

Tarannum Mansoori

2011-01-01

Full Text Available Purpose : To evaluate the ability of spectral domain optical coherence tomography (OCT peripapillary retinal nerve fiber layer thickness (RNFLT parameters to distinguish normal eyes from those with early glaucoma in Asian Indian eyes. Design : Observational cross-sectional study. Materials and Methods : One hundred and seventy eight eyes (83 glaucoma patients and 95 age matched healthy subjects of subjects more than 40 years of age were included in the study. All subjects underwent RNFLT measurement with spectral OCT/ scanning laser ophthalmoscope (SLO after dilatation. Sensitivity, specificity and area under the receiving operating characteristic curve (AROC were calculated for various OCT peripapillary RNFL parameters. Results: The mean RNFLT in healthy subjects and patients with early glaucoma were 105.7 ± 5.1 μm and 90.7 ± 7.5 μm, respectively. The largest AROC was found for 12 o′clock- hour (0.98, average (0.96 and superior quadrant RNFLT (0.9. When target specificity was set at ≥ 90% and ≥ 80%, the parameters with highest sensitivity were 12 o′clock -hour (91.6%, average RNFLT (85.3% and 12 o′ clock- hour (96.8 %, average RNFLT (94.7% respectively. Conclusion : Our study showed good ability of spectral OCT/ SLO to differentiate normal eyes from patients with early glaucoma and hence it may serve as an useful adjunct for early diagnosis of glaucoma.

Growth and optical spectroscopy of synthetic diamonds

International Nuclear Information System (INIS)

Mudryj, A.V.; Larionova, T.P.; Shakin, I.A.; Gysakov, G.A.; Dubrov, G.A.; Tikhonov, V.V.

2003-01-01

It is studied the growth and optical properties of synthetic diamonds, which may be used for detection of ionizing radiation, optical windows, heat removal, ultraviolet and thermo sensors, optoelectronic devices. Optical properties of diamonds (grown in different technological conditions) were studied in temperature range 78 - 300 K by means of measuring transmission in spectral band 0.2 - 25 μm, photoluminescence and registration of luminescence excitation spectra in spectral band 0.2 - 2 μm

The Infrared Telescope Facility (IRTF) Spectral Library: Cool Stars

Science.gov (United States)

Rayner, John T.; Cushing, Michael C.; Vacca, William D.

2009-12-01

We present a 0.8-5 μm spectral library of 210 cool stars observed at a resolving power of R ≡ λ/Δλ ~ 2000 with the medium-resolution infrared spectrograph, SpeX, at the 3.0 m NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. The stars have well-established MK spectral classifications and are mostly restricted to near-solar metallicities. The sample not only contains the F, G, K, and M spectral types with luminosity classes between I and V, but also includes some AGB, carbon, and S stars. In contrast to some other spectral libraries, the continuum shape of the spectra is measured and preserved in the data reduction process. The spectra are absolutely flux calibrated using the Two Micron All Sky Survey photometry. Potential uses of the library include studying the physics of cool stars, classifying and studying embedded young clusters and optically obscured regions of the Galaxy, evolutionary population synthesis to study unresolved stellar populations in optically obscured regions of galaxies and synthetic photometry. The library is available in digital form from the IRTF Web site.

Extraction and fusion of spectral parameters for face recognition

Science.gov (United States)

Boisier, B.; Billiot, B.; Abdessalem, Z.; Gouton, P.; Hardeberg, J. Y.

2011-03-01

Many methods have been developed in image processing for face recognition, especially in recent years with the increase of biometric technologies. However, most of these techniques are used on grayscale images acquired in the visible range of the electromagnetic spectrum. The aims of our study are to improve existing tools and to develop new methods for face recognition. The techniques used take advantage of the different spectral ranges, the visible, optical infrared and thermal infrared, by either combining them or analyzing them separately in order to extract the most appropriate information for face recognition. We also verify the consistency of several keypoints extraction techniques in the Near Infrared (NIR) and in the Visible Spectrum.

Grading of Age-Related Macular Degeneration: Comparison between Color Fundus Photography, Fluorescein Angiography, and Spectral Domain Optical Coherence Tomography

Directory of Open Access Journals (Sweden)

Nils F. Mokwa

2013-01-01

Full Text Available Purpose. To compare color fundus photography (FP, fluorescein angiography (FA, and spectral domain optical coherence tomography (SDOCT for the detection of age-related macular degeneration (AMD, choroidal neovascularisation (CNV, and CNV activity. Methods. FPs, FAs, and SDOCT volume scans from 120 eyes of 66 AMD and control patients were randomly collected. Control eyes were required to show no AMD, but other retinal pathology was allowed. The presence of drusen, pigmentary changes, CNV, and signs for CNV activity was independently analyzed for all imaging modalities. Results. AMD was diagnosed based on FP in 75 eyes. SDOCT and FA showed sensitivity (specificity of 89% (76% and 92% (82%, respectively. CNV was present on FA in 68 eyes. Sensitivity (specificity was 78% (100% for FP and 94% (98% for SDOCT. CNV activity was detected by SDOCT or FA in 60 eyes with an agreement in 46 eyes. Sensitivity was 88% for SDOCT and 88% for FA. FP showed sensitivity of 38% and specificity of 98%. Conclusions. CNV lesions and activity may be missed by FP alone, but FP may help identifying drusen and pigmentary changes. SDOCT is highly sensitive for the detection of AMD, CNV, and CNV activity; however, it cannot fully replace FA.

Radical advancement in multi-spectral imaging for autonomous vehicles (UAVs, UGVs, and UUVs) using active compensation.

Energy Technology Data Exchange (ETDEWEB)

Clark, Brian F.; Bagwell, Brett E.; Wick, David Victor

2007-01-01

The purpose of this LDRD was to demonstrate a compact, multi-spectral, refractive imaging systems using active optical compensation. Compared to a comparable, conventional lens system, our system has an increased operational bandwidth, provides for spectral selectivity and, non-mechanically corrects aberrations induced by the wavelength dependent properties of a passive refractive optical element (i.e. lens). The compact nature and low power requirements of the system lends itself to small platforms such as autonomous vehicles. In addition, the broad spectral bandwidth of our system would allow optimized performance for both day/night use, and the multi-spectral capability allows for spectral discrimination and signature identification.

Effect of H{sup +} implantation on the optical properties of semi-insulating GaAs crystals in the IR spectral region

Energy Technology Data Exchange (ETDEWEB)

Klyui, N. I.; Lozinskii, V. B., E-mail: lvb@isp.kiev.ua [Jilin University, College of Physics (China); Liptuga, A. I.; Dikusha, V. N. [National Academy of Sciences of Ukraine, Lashkaryov Institute of Semiconductor Physics (Ukraine); Oksanych, A. P.; Kogdas’, M. G.; Perekhrest, A. L.; Pritchin, S. E. [Kremenchug National University (Ukraine)

2017-03-15

The optical properties of semi-insulating GaAs crystals subjected to multienergy hydrogen-ion implantation and treatment in a high-frequency electromagnetic field are studied in the infrared spectral region. It is established that such combined treatment provides a means for substantially increasing the transmittance of GaAs crystals to values characteristic of crystals of high optical quality. On the basis of analysis of the infrared transmittance and reflectance data, Raman spectroscopy data, and atomic-force microscopy data on the surface morphology of the crystals, a physical model is proposed to interpret the effects experimentally observed in the crystals. The model takes into account the interaction of radiation defects with the initial structural defects in the crystals as well as the effect of compensation of defect centers by hydrogen during high-frequency treatment.

Multi-Band Spectral Properties of Fermi Blazars Benzhong Dai ...

Indian Academy of Sciences (India)

... FSRQs, 41 AGNs of other types and 72 AGNs of unknown type (Abdo et al. 2010a). This large sample enable us to investigate the spectral shapes of blazars from optical to X-ray to γ-ray in more detail than has been done before. For this purpose, we collected data for all Fermi blazars having available spectral information.

Final Report on LDRD project 130784 : functional brain imaging by tunable multi-spectral Event-Related Optical Signal (EROS).

Energy Technology Data Exchange (ETDEWEB)

Speed, Ann Elizabeth; Spahn, Olga Blum; Hsu, Alan Yuan-Chun

2009-09-01

Functional brain imaging is of great interest for understanding correlations between specific cognitive processes and underlying neural activity. This understanding can provide the foundation for developing enhanced human-machine interfaces, decision aides, and enhanced cognition at the physiological level. The functional near infrared spectroscopy (fNIRS) based event-related optical signal (EROS) technique can provide direct, high-fidelity measures of temporal and spatial characteristics of neural networks underlying cognitive behavior. However, current EROS systems are hampered by poor signal-to-noise-ratio (SNR) and depth of measure, limiting areas of the brain and associated cognitive processes that can be investigated. We propose to investigate a flexible, tunable, multi-spectral fNIRS EROS system which will provide up to 10x greater SNR as well as improved spatial and temporal resolution through significant improvements in electronics, optoelectronics and optics, as well as contribute to the physiological foundation of higher-order cognitive processes and provide the technical foundation for miniaturized portable neuroimaging systems.

Preclinical evaluation and intraoperative human retinal imaging with a high-resolution microscope-integrated spectral domain optical coherence tomography device.

Science.gov (United States)

Hahn, Paul; Migacz, Justin; O'Donnell, Rachelle; Day, Shelley; Lee, Annie; Lin, Phoebe; Vann, Robin; Kuo, Anthony; Fekrat, Sharon; Mruthyunjaya, Prithvi; Postel, Eric A; Izatt, Joseph A; Toth, Cynthia A

2013-01-01

The authors have recently developed a high-resolution microscope-integrated spectral domain optical coherence tomography (MIOCT) device designed to enable OCT acquisition simultaneous with surgical maneuvers. The purpose of this report is to describe translation of this device from preclinical testing into human intraoperative imaging. Before human imaging, surgical conditions were fully simulated for extensive preclinical MIOCT evaluation in a custom model eye system. Microscope-integrated spectral domain OCT images were then acquired in normal human volunteers and during vitreoretinal surgery in patients who consented to participate in a prospective institutional review board-approved study. Microscope-integrated spectral domain OCT images were obtained before and at pauses in surgical maneuvers and were compared based on predetermined diagnostic criteria to images obtained with a high-resolution spectral domain research handheld OCT system (HHOCT; Bioptigen, Inc) at the same time point. Cohorts of five consecutive patients were imaged. Successful end points were predefined, including ≥80% correlation in identification of pathology between MIOCT and HHOCT in ≥80% of the patients. Microscope-integrated spectral domain OCT was favorably evaluated by study surgeons and scrub nurses, all of whom responded that they would consider participating in human intraoperative imaging trials. The preclinical evaluation identified significant improvements that were made before MIOCT use during human surgery. The MIOCT transition into clinical human research was smooth. Microscope-integrated spectral domain OCT imaging in normal human volunteers demonstrated high resolution comparable to tabletop scanners. In the operating room, after an initial learning curve, surgeons successfully acquired human macular MIOCT images before and after surgical maneuvers. Microscope-integrated spectral domain OCT imaging confirmed preoperative diagnoses, such as full-thickness macular hole

The spectral energy distribution of the scattered light from dark clouds

Science.gov (United States)

Mattila, Kalevi; Schnur, G. F. O.

1989-01-01

A dark cloud is exposed to the ambient radiation field of integrated starlight in the Galaxy. Scattering of starlight by the dust particles gives rise to a diffuse surface brightness of the dark nebula. The intensity and the spectrum of this diffuse radiation can be used to investigate, e.g., the scattering parameters of the dust, the optical thickness of the cloud, and as a probe of the ambient radiation field at the location of the cloud. An understanding of the scattering process is also a prerequisite for the isolation of broad spectral features due to fluorescence or to any other non-scattering origin of the diffuse light. Model calculations are presented for multiple scattering in a spherical cloud. These calculations show that the different spectral shapes of the observed diffuse light can be reproduced with standard dust parameters. The possibility to use the observed spectrum as a diagnostic tool for analyzing the thickness of the cloud and the dust particle is discussed.

Spectral-Efficiency - Illumination Pareto Front for Energy Harvesting Enabled VLC System

KAUST Repository

Abdelhady, Amr Mohamed Abdelaziz; Amin, Osama; Chaaban, Anas; Alouini, Mohamed-Slim

2017-01-01

. The adopted optical system provides users with illumination and data communication services. The outdoor optical design objective is to maximize the illumination, while the communication design objective is to maximize the spectral efficiency (SE). The design

High spectral resolution infrared observations of V1057 Cygni

International Nuclear Information System (INIS)

Hartmann, L.; Kenyon, S.J.

1987-01-01

High-resolution near-infrared spectra of V1057 Cygni obtained in 1986 with the KPNO 4-m Fourier transform spectrometer provide support for a previously proposed accretion disk model. The model predicts that the observed rotational broadening of spectral lines should be smaller in the infrared than in the optical. The present observations show that V1057 Cyg rotates more slowly at 2.3 microns than at 6000 A by an amount quantitatively consistent with the simple disk models. The absence of any radial velocity variations in either the infrared or optical spectral regions supports the suggestion that the accreted material arises from a remnant disk of protostellar material. 19 references

Opto-mechanical design of optical window for aero-optics effect simulation instruments

Science.gov (United States)

Wang, Guo-ming; Dong, Dengfeng; Zhou, Weihu; Ming, Xing; Zhang, Yan

2016-10-01

A complete theory is established for opto-mechanical systems design of the window in this paper, which can make the design more rigorous .There are three steps about the design. First, the universal model of aerodynamic environment is established based on the theory of Computational Fluid Dynamics, and the pneumatic pressure distribution and temperature data of optical window surface is obtained when aircraft flies in 5-30km altitude, 0.5-3Ma speed and 0-30°angle of attack. The temperature and pressure distribution values for the maximum constraint is selected as the initial value of external conditions on the optical window surface. Then, the optical window and mechanical structure are designed, which is also divided into two parts: First, mechanical structure which meet requirements of the security and tightness is designed. Finally, rigorous analysis and evaluation are given about the structure of optics and mechanics we have designed. There are two parts to be analyzed. First, the Fluid-Solid-Heat Coupled Model is given based on finite element analysis. And the deformation of the glass and structure can be obtained by the model, which can assess the feasibility of the designed optical windows and ancillary structure; Second, the new optical surface is fitted by Zernike polynomials according to the deformation of the surface of the optical window, which can evaluate imaging quality impact of spectral camera by the deformation of window.

Optical design constrains in triangular Sagnac imaging interferometers for earth observation

Science.gov (United States)

Barducci, A.; Guzzi, D.; Lastri, C.; Nardino, V.; Pippi, I.

2017-11-01

The Italian Space Agency selected the imaging interferometer ALISEO (Aerospace Leap-frog Imaging Stationary interferometer for Earth Observation) as the main payload for a technological optical mission based on the small satellite MIOsat. The simple design of such an instrument, based on Sagnac configuration, makes it a promising for Earth observation missions. The ALISEO instrument acquires an image of 10 Km by 10 Km with a spatial resolution better than 10 m and a spectral resolution of 200 cm-1 (7 nm @ 0.6 μm) in the 0.4 - 1 μm spectral range. ALISEO does not employ any moving part to generate the phase delays between the two interfering beams. The sensor acquires target images modulated by a pattern of autocorrelation functions of the energy coming from each scene pixel, and the resulting fringe pattern remains fixed with respect to the instrument's field-of-view. The complete interferogram of each target location is retrieved by introducing a relative source-observer motion, which allows any image pixels to be observed under different viewing-angles corresponding to different Optical Path Differences (OPDs). In this paper various optical configurations are analyzed in order to meet the mission requirements. Optical configurations are discussed taking into account: detector size, spatial resolution, and entrance pupil aperture. The proposed configurations should avoid vignetting, reduce geometric and chromatic aberrations, and comply with the size and weight constrains requested by space mission. Optical configurations, based on both refractive and reflective focusing elements, are presented and discussed. Finally, some properties pertaining to the selected Sagnac configuration are discussed in conjunction with spectral estimations and data processing.

Nonlinear single-spin spectrum analyzer.

Science.gov (United States)

Kotler, Shlomi; Akerman, Nitzan; Glickman, Yinnon; Ozeri, Roee

2013-03-15

Qubits have been used as linear spectrum analyzers of their environments. Here we solve the problem of nonlinear spectral analysis, required for discrete noise induced by a strongly coupled environment. Our nonperturbative analytical model shows a nonlinear signal dependence on noise power, resulting in a spectral resolution beyond the Fourier limit as well as frequency mixing. We develop a noise characterization scheme adapted to this nonlinearity. We then apply it using a single trapped ion as a sensitive probe of strong, non-Gaussian, discrete magnetic field noise. Finally, we experimentally compared the performance of equidistant vs Uhrig modulation schemes for spectral analysis.

Non-local effect in Brillouin optical time-domain analyzer based on Raman amplification

International Nuclear Information System (INIS)

Jia Xinhong; Rao Yunjiang; Wang Zinan; Zhang Weili; Ran Zengling; Deng Kun; Yang Zixin

2012-01-01

Compared with conventional Brillouin optical time-domain analyzer (BOTDA), the BOTDA based on Raman amplification allows longer sensing range, higher signal-to-noise ratio and higher measurement accuracy. However, the non-local effect induced by pump depletion significantly restricts the probe optical power injected to sensing fiber, thereby limiting the further extension for sensing distance. In this paper, the coupled equations including the interaction of probe light, Brillouin and Raman pumps are applied to the study on the non-local characteristics of BOTDA based on Raman amplification. The results show that, the system error induced by non-local effect worsens with increased powers of probe wave and Raman pump. The frequency-division-multiplexing (cascading the fibers with various Brillouin frequency shifts) and time-division-multiplexing (modulating both of the Brillouin pump and probe lights) technologies are efficient approaches to suppress the non-local effect, through shortening the effective interaction range between Brillouin pump and probe lights. (authors)

Analyzing availability using transfer function models and cross spectral analysis

International Nuclear Information System (INIS)

Singpurwalla, N.D.

1980-01-01

The paper shows how the methods of multivariate time series analysis can be used in a novel way to investigate the interrelationships between a series of operating (running) times and a series of maintenance (down) times of a complex system. Specifically, the techniques of cross spectral analysis are used to help obtain a Box-Jenkins type transfer function model for the running times and the down times of a nuclear reactor. A knowledge of the interrelationships between the running times and the down times is useful for an evaluation of maintenance policies, for replacement policy decisions, and for evaluating the availability and the readiness of complex systems

Evans hole and non linear optical activity in Bis(melaminium) sulphate dihydrate: A vibrational spectral study.

Science.gov (United States)

Suresh Kumar, V R; Binoy, J; Dawn Dharma Roy, S; Marchewka, M K; Jayakumar, V S

2015-01-01

Bis(melaminium) sulphate dihydrate (BMSD), an interesting melaminium derivative for nonlinear optical activity, has been subjected to vibrational spectral analysis using FT IR and FT Raman spectra. The analysis has been aided by the Potential Energy Distribution (PED) of vibrational spectral bands, derived using density functional theory (DFT) at B3LYP/6-31G(d) level. The geometry is found to correlate well with the XRD structure and the band profiles for certain vibrations in the finger print region have been theoretically explained using Evans hole. The detailed Natural Bond Orbital (NBO) analysis of the hydrogen bonding in BMSD has also been carried out to understand the correlation between the stabilization energy of hyperconjugation of the lone pair of donor with the σ(∗) orbital of hydrogen-acceptor bond and the strength of hydrogen bond. The theoretical calculation shows that BMSD has NLO efficiency, 2.66 times that of urea. The frontier molecular orbital analysis points to a charge transfer, which contributes to NLO activity, through N-H…O intermolecular hydrogen bonding between the melaminium ring and the sulphate. The molecular electrostatic potential (MEP) mapping has also been performed for the detailed analysis of the mutual interactions between melaminium ring and sulphate ion. Copyright © 2015 Elsevier B.V. All rights reserved.

High Spectral Resolution Lidar and MPLNET Micro Pulse Lidar Aerosol Optical Property Retrieval Intercomparison During the 2012 7-SEAS Field Campaign at Singapore

Science.gov (United States)

Lolli, Simone; Welton, Ellsworth J.; Campbell, James R.; Eloranta, Edwin; Holben, Brent N.; Chew, Boon Ning; Salinas, Santo V.

2014-01-01

From August 2012 to February 2013 a High Resolution Spectral Lidar (HSRL; 532 nm) was deployed at that National University of Singapore near a NASA Micro Pulse Lidar NETwork (MPLNET; 527 nm) site. A primary objective of the MPLNET lidar project is the production and dissemination of reliable Level 1 measurements and Level 2 retrieval products. This paper characterizes and quantifies error in Level 2 aerosol optical property retrievals conducted through inversion techniques that derive backscattering and extinction coefficients from MPLNET elastic single-wavelength datasets. MPLNET Level 2 retrievals for aerosol optical depth and extinction/backscatter coefficient profiles are compared with corresponding HSRL datasets, for which the instrument collects direct measurements of each using a unique optical configuration that segregates aerosol and cloud backscattered signal from molecular signal. The intercomparison is performed, and error matrices reported, for lower (0-5km) and the upper (>5km) troposphere, respectively, to distinguish uncertainties observed within and above the MPLNET instrument optical overlap regime.

Angle of arrival estimation using spectral interferometry

International Nuclear Information System (INIS)

Barber, Z.W.; Harrington, C.; Thiel, C.W.; Babbitt, W.R.; Krishna Mohan, R.

2010-01-01

We have developed a correlative signal processing concept based on a Mach-Zehnder interferometer and spatial-spectral (S2) materials that enables direct mapping of RF spectral phase as well as power spectral recording. This configuration can be used for precise frequency resolved time delay estimation between signals received by a phased antenna array system that in turn could be utilized to estimate the angle of arrival. We present an analytical theoretical model and a proof-of-principle demonstration of the concept of time difference of arrival estimation with a cryogenically cooled Tm:YAG crystal that operates on microwave signals modulated onto a stabilized optical carrier at 793 nm.

Angle of arrival estimation using spectral interferometry

Energy Technology Data Exchange (ETDEWEB)

Barber, Z.W.; Harrington, C.; Thiel, C.W.; Babbitt, W.R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Krishna Mohan, R., E-mail: krishna@spectrum.montana.ed [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States)

2010-09-15

We have developed a correlative signal processing concept based on a Mach-Zehnder interferometer and spatial-spectral (S2) materials that enables direct mapping of RF spectral phase as well as power spectral recording. This configuration can be used for precise frequency resolved time delay estimation between signals received by a phased antenna array system that in turn could be utilized to estimate the angle of arrival. We present an analytical theoretical model and a proof-of-principle demonstration of the concept of time difference of arrival estimation with a cryogenically cooled Tm:YAG crystal that operates on microwave signals modulated onto a stabilized optical carrier at 793 nm.

Onboard spectral imager data processor

Science.gov (United States)

Otten, Leonard J.; Meigs, Andrew D.; Franklin, Abraham J.; Sears, Robert D.; Robison, Mark W.; Rafert, J. Bruce; Fronterhouse, Donald C.; Grotbeck, Ronald L.

1999-10-01

Previous papers have described the concept behind the MightySat II.1 program, the satellite's Fourier Transform imaging spectrometer's optical design, the design for the spectral imaging payload, and its initial qualification testing. This paper discusses the on board data processing designed to reduce the amount of downloaded data by an order of magnitude and provide a demonstration of a smart spaceborne spectral imaging sensor. Two custom components, a spectral imager interface 6U VME card that moves data at over 30 MByte/sec, and four TI C-40 processors mounted to a second 6U VME and daughter card, are used to adapt the sensor to the spacecraft and provide the necessary high speed processing. A system architecture that offers both on board real time image processing and high-speed post data collection analysis of the spectral data has been developed. In addition to the on board processing of the raw data into a usable spectral data volume, one feature extraction technique has been incorporated. This algorithm operates on the basic interferometric data. The algorithm is integrated within the data compression process to search for uploadable feature descriptions.

Accurately Measuring the Color of the Ocean on Earth and from Space: Uncertainties Revisited and A Report from the Community-Led Spectral Absorption Workshop to Update and Revise the NASA Inherent Optical Properties Protocol

Science.gov (United States)

Neeley, Aimee Renee

2014-01-01

The color of the ocean (apparent optical properties or AOPs) is determined by the spectral scattering and absorption of light by its dissolved and particulate constituents.The absorption and scattering properties of the water column are the so-called inherent optical properties.

Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS in the red spectral range

Directory of Open Access Journals (Sweden)

T. Wagner

2007-01-01

Full Text Available A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm reflectance structures (i.e. "fingerprint" structures of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS, which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric absorptions are automatically corrected (in contrast to other algorithms. The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the results illustrate the seasonal cycles of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

Management of Patients with Graves’ Disease and Orbital Involvement: Role of Spectral Domain Optical Coherence Tomography

Directory of Open Access Journals (Sweden)

Alice Bruscolini

2018-01-01

Full Text Available Purpose. To investigate the role of choroidal thickness evaluation with spectral domain optical coherence tomography (SDOCT and enhanced depth imaging (EDI technique in the management of patients with Graves’ disease and orbitopathy (GO. Methods. Thirty-six eyes of 18 patients with GO and 36 eyes of 18 age-matched control subjects were included in this retrospective observational study. All the subjects underwent a complete ophthalmological evaluation, including clinical activity score (CAS and exophthalmometry. The SDOCT images of the choroid were obtained by EDI modality. Results. Choroidal thickness was significantly increased in GO than in control eyes (p<0.01. A significant correlation was found between choroidal thickness and CAS, proptosis, and the duration of disease (p<0.05. Conclusion. This study shows that choroidal thickness, evaluated with EDI-OCT, is significantly increased in patients with GO and correlates with the activity of the disease, proptosis, and duration of the disease. The choroidal thickening may reflect the ocular hemodynamic changes, and enhanced depth imaging optical coherence tomography may be a useful tool for the evaluation of orbital congestion and management of patients with Graves’ disease and orbital involvement.

Noise suppression system of OCDMA with spectral/spatial 2D hybrid code

Science.gov (United States)

Matem, Rima; Aljunid, S. A.; Junita, M. N.; Rashidi, C. B. M.; Shihab Aqrab, Israa

2017-11-01

In this paper, we propose a novel 2D spectral/spatial hybrid code based on 1D ZCC and 1D MD where the both present a zero cross correlation property analyzed and the influence of the noise of optical as Phase Induced Intensity Noise (PIIN), shot and thermal noise. This new code is shown effectively to mitigate the PIIN and suppresses MAI. Using 2D ZCC/MD code the performance of the system can be improved in term of as well as to support more simultaneous users compared of the 2D FCC/MDW and 2D DPDC codes.

Noise suppression system of OCDMA with spectral/spatial 2D hybrid code

Directory of Open Access Journals (Sweden)

Matem Rima

2017-01-01

Full Text Available In this paper, we propose a novel 2D spectral/spatial hybrid code based on 1D ZCC and 1D MD where the both present a zero cross correlation property analyzed and the influence of the noise of optical as Phase Induced Intensity Noise (PIIN, shot and thermal noise. This new code is shown effectively to mitigate the PIIN and suppresses MAI. Using 2D ZCC/MD code the performance of the system can be improved in term of as well as to support more simultaneous users compared of the 2D FCC/MDW and 2D DPDC codes.

Salinity and spectral reflectance of soils

Science.gov (United States)

Szilagyi, A.; Baumgardner, M. F.

1991-01-01

The basic spectral response related to the salt content of soils in the visible and reflective IR wavelengths is analyzed in order to explore remote sensing applications for monitoring processes of the earth system. The bidirectional reflectance factor (BRF) was determined at 10 nm of increments over the 520-2320-nm spectral range. The effect of salts on reflectance was analyzed on the basis of 162 spectral measurements. MSS and TM bands were simulated within the measured spectral region. A strong relationship was found in variations of reflectance and soil characteristics pertaining to salinization and desalinization. Although the individual MSS bands had high R-squared values and 75-79 percent of soil/treatment combinations were separable, there was a large number of soil/treatment combinations not distinguished by any of the four highly correlated MSS bands under consideration.

HIGH-REDSHIFT DUST OBSCURED GALAXIES: A MORPHOLOGY-SPECTRAL ENERGY DISTRIBUTION CONNECTION REVEALED BY KECK ADAPTIVE OPTICS

International Nuclear Information System (INIS)

Melbourne, J.; Matthews, K.; Soifer, B. T.

2009-01-01

A simple optical to mid-IR color selection, R - [24]>14, i.e., f ν (24 μm)/f ν (R) ∼> 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z ∼ 2 ± 0.5. Extreme mid-IR luminosities (L IR > 10 12-14 ) suggest that DOGs are powered by a combination of active galactic nuclei (AGNs) and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest-frame optical morphologies, we obtained high-spatial resolution (0.''05-0.''1) Keck Adaptive Optics K'-band images of 15 DOGs. The images reveal a wide range of morphologies, including small exponential disks (eight of 15), small ellipticals (four of 15), and unresolved sources (two of 15). One particularly diffuse source could not be classified because of low signal-to-noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral energy distributions (SEDs) suggestive of AGN activity. Thus, central AGN light may be biasing the morphologies of the more luminous DOGs to higher concentration. Conversely, more diffuse DOGs tend to show an SED shape suggestive of star formation. Two of 15 in the sample show multiple resolved components with separations of ∼1 kpc, circumstantial evidence for ongoing mergers.

Design and simulations of a spectral efficient optical code division multiple access scheme using alternated energy differentiation and single-user soft-decision demodulation

Science.gov (United States)

A. Garba, Aminata

2017-01-01

This paper presents a new approach to optical Code Division Multiple Access (CDMA) network transmission scheme using alternated amplitude sequences and energy differentiation at the transmitters to allow concurrent and secure transmission of several signals. The proposed system uses error control encoding and soft-decision demodulation to reduce the multi-user interference at the receivers. The design of the proposed alternated amplitude sequences, the OCDMA energy modulators and the soft decision, single-user demodulators are also presented. Simulation results show that the proposed scheme allows achieving spectral efficiencies higher than several reported results for optical CDMA and much higher than the Gaussian CDMA capacity limit.

Extending the Effective Ranging Depth of Spectral Domain Optical Coherence Tomography by Spatial Frequency Domain Multiplexing

Directory of Open Access Journals (Sweden)

Tong Wu

2016-11-01

Full Text Available We present a spatial frequency domain multiplexing method for extending the imaging depth range of a spectral domain optical coherence tomography (SDOCT system without any expensive device. This method uses two galvo scanners with different pivot-offset distances in two independent reference arms for spatial frequency modulation and multiplexing. The spatial frequency contents corresponding to different depth regions of the sample can be shifted to different frequency bands. The spatial frequency domain multiplexing SDOCT system provides an approximately 1.9-fold increase in the effective ranging depth compared with that of a conventional full-range SDOCT system. The reconstructed images of phantom and biological tissue demonstrate the expected increase in ranging depth. The parameters choice criterion for this method is discussed.

Optical spatial differentiator based on subwavelength high-contrast gratings

Science.gov (United States)

Dong, Zhewei; Si, Jiangnan; Yu, Xuanyi; Deng, Xiaoxu

2018-04-01

An optical spatial differentiator based on subwavelength high-contrast gratings (HCGs) is proposed experimentally. The spatial differentiation property of the subwavelength HCG is analyzed by calculating its spatial spectral transfer function based on the periodic waveguide theory. By employing the FDTD solutions, the performance of the subwavelength HCG spatial differentiator was investigated numerically. The subwavelength HCG differentiator with the thickness at the nanoscale was fabricated on the quartz substrate by electron beam lithography and Bosch deep silicon etching. Observed under an optical microscope with a CCD camera, the spatial differentiation of the incident field profile was obtained by the subwavelength HCG differentiator in transmission without Fourier lens. By projecting the images of slits, letter "X," and a cross on the subwavelength HCG differentiator, edge detections of images were obtained in transmission. With the nanoscale HCG structure and simple optical implementation, the proposed optical spatial differentiator provides the prospects for applications in optical computing systems and parallel data processing.

Performance characterization of a pressure-tuned wide-angle Michelson interferometric spectral filter for high spectral resolution lidar

Science.gov (United States)

Seaman, Shane T.; Cook, Anthony L.; Scola, Salvatore J.; Hostetler, Chris A.; Miller, Ian; Welch, Wayne

2015-09-01

High Spectral Resolution Lidar (HSRL) is typically realized using an absorption filter to separate molecular returns from particulate returns. NASA Langley Research Center (LaRC) has designed and built a Pressure-Tuned Wide-Angle Michelson Interferometer (PTWAMI) as an alternate means to separate the two types of atmospheric returns. While absorption filters only work at certain wavelengths and suffer from low photon efficiency due to light absorption, an interferometric spectral filter can be designed for any wavelength and transmits nearly all incident photons. The interferometers developed at LaRC employ an air spacer in one arm, and a solid glass spacer in the other. Field widening is achieved by specific design and selection of the lengths and refractive indices of these two arms. The principal challenge in using such an interferometer as a spectral filter for HSRL aboard aircraft is that variations in glass temperature and air pressure cause changes in the interferometer's optical path difference. Therefore, a tuning mechanism is needed to actively accommodate for these changes. The pressure-tuning mechanism employed here relies on changing the pressure in an enclosed, air-filled arm of the interferometer to change the arm's optical path length. However, tuning using pressure will not adjust for tilt, mirror warpage, or thermally induced wavefront error, so the structural, thermal, and optical behavior of the device must be well understood and optimized in the design and manufacturing process. The PTWAMI has been characterized for particulate transmission ratio, wavefront error, and tilt, and shows acceptable performance for use in an HSRL instrument.

Chromatic aberrations correction for imaging spectrometer based on acousto-optic tunable filter with two transducers.

Science.gov (United States)

Zhao, Huijie; Wang, Ziye; Jia, Guorui; Zhang, Ying; Xu, Zefu

2017-10-02

The acousto-optic tunable filter (AOTF) with wide wavelength range and high spectral resolution has long crystal and two transducers. A longer crystal length leads to a bigger chromatic focal shift and the double-transducer arrangement induces angular mutation in diffracted beam, which increase difficulty in longitudinal and lateral chromatic aberration correction respectively. In this study, the two chromatic aberrations are analyzed quantitatively based on an AOTF optical model and a novel catadioptric dual-path configuration is proposed to correct both the chromatic aberrations. The test results exhibit effectiveness of the optical configuration for this type of AOTF-based imaging spectrometer.

Automated 3-D method for the correction of axial artifacts in spectral-domain optical coherence tomography images

Science.gov (United States)

Antony, Bhavna; Abràmoff, Michael D.; Tang, Li; Ramdas, Wishal D.; Vingerling, Johannes R.; Jansonius, Nomdo M.; Lee, Kyungmoo; Kwon, Young H.; Sonka, Milan; Garvin, Mona K.

2011-01-01

The 3-D spectral-domain optical coherence tomography (SD-OCT) images of the retina often do not reflect the true shape of the retina and are distorted differently along the x and y axes. In this paper, we propose a novel technique that uses thin-plate splines in two stages to estimate and correct the distinct axial artifacts in SD-OCT images. The method was quantitatively validated using nine pairs of OCT scans obtained with orthogonal fast-scanning axes, where a segmented surface was compared after both datasets had been corrected. The mean unsigned difference computed between the locations of this artifact-corrected surface after the single-spline and dual-spline correction was 23.36 ± 4.04 μm and 5.94 ± 1.09 μm, respectively, and showed a significant difference (p < 0.001 from two-tailed paired t-test). The method was also validated using depth maps constructed from stereo fundus photographs of the optic nerve head, which were compared to the flattened top surface from the OCT datasets. Significant differences (p < 0.001) were noted between the artifact-corrected datasets and the original datasets, where the mean unsigned differences computed over 30 optic-nerve-head-centered scans (in normalized units) were 0.134 ± 0.035 and 0.302 ± 0.134, respectively. PMID:21833377

Silver metaphosphate glass wires inside silica fibers--a new approach for hybrid optical fibers.

Science.gov (United States)

Jain, Chhavi; Rodrigues, Bruno P; Wieduwilt, Torsten; Kobelke, Jens; Wondraczek, Lothar; Schmidt, Markus A

2016-02-22

Phosphate glasses represent promising candidates for next-generation photonic devices due to their unique characteristics, such as vastly tunable optical properties, and high rare earth solubility. Here we show that silver metaphosphate wires with bulk optical properties and diameters as small as 2 µm can be integrated into silica fibers using pressure-assisted melt filling. By analyzing two types of hybrid metaphosphate-silica fibers, we show that the filled metaphosphate glass has only negligible higher attenuation and a refractive index that is identical to the bulk material. The presented results pave the way towards new fiber-type optical devices relying on metaphosphate glasses, which are promising materials for applications in nonlinear optics, sensing and spectral filtering.

Recent progress of push-broom infrared hyper-spectral imager in SITP

Science.gov (United States)

Wang, Yueming; Hu, Weida; Shu, Rong; Li, Chunlai; Yuan, Liyin; Wang, Jianyu

2017-02-01

In the past decades, hyper-spectral imaging technologies were well developed in SITP, CAS. Many innovations for system design and key parts of hyper-spectral imager were finished. First airborne hyper-spectral imager operating from VNIR to TIR in the world was emerged in SITP. It is well known as OMIS(Operational Modular Imaging Spectrometer). Some new technologies were introduced to improve the performance of hyper-spectral imaging system in these years. A high spatial space-borne hyper-spectral imager aboard Tiangong-1 spacecraft was launched on Sep.29, 2011. Thanks for ground motion compensation and high optical efficiency prismatic spectrometer, a large amount of hyper-spectral imagery with high sensitivity and good quality were acquired in the past years. Some important phenomena were observed. To diminish spectral distortion and expand field of view, new type of prismatic imaging spectrometer based curved prism were proposed by SITP. A prototype of hyper-spectral imager based spherical fused silica prism were manufactured, which can operate from 400nm 2500nm. We also made progress in the development of LWIR hyper-spectral imaging technology. Compact and low F number LWIR imaging spectrometer was designed, manufactured and integrated. The spectrometer operated in a cryogenically-cooled vacuum box for background radiation restraint. The system performed well during flight experiment in an airborne platform. Thanks high sensitivity FPA and high performance optics, spatial resolution and spectral resolution and SNR of system are improved enormously. However, more work should be done for high radiometric accuracy in the future.

Causality and analyticity in optics

International Nuclear Information System (INIS)

Nussenzveig, H.M.

In order to provide an overall picture of the broad range of optical phenomena that are directly linked with the concepts of causality and analyticity, the following topics are briefly reviewed, emphasizing recent developments: 1) Derivation of dispersion relations for the optical constants of general linear media from causality. Application to the theory of natural optical activity. 2) Derivation of sum rules for the optical constants from causality and from the short-time response function (asymptotic high-frequency behavior). Average spectral behavior of optical media. Applications. 3) Role of spectral conditions. Analytic properties of coherence functions in quantum optics. Reconstruction theorem.4) Phase retrieval problems. 5) Inverse scattering problems. 6) Solution of nonlinear evolution equations in optics by inverse scattering methods. Application to self-induced transparency. Causality in nonlinear wave propagation. 7) Analytic continuation in frequency and angular momentum. Complex singularities. Resonances and natural-mode expansions. Regge poles. 8) Wigner's causal inequality. Time delay. Spatial displacements in total reflection. 9) Analyticity in diffraction theory. Complex angular momentum theory of Mie scattering. Diffraction as a barrier tunnelling effect. Complex trajectories in optics. (Author) [pt

Potential application of Chinese traditional medicine (CTM) as enhancer for tissue optical clearing

Science.gov (United States)

Chen, Wei; Jiang, Jingying; Wang, Ruikang K.; Xu, Kexin

2009-02-01

Many biocompatible hyperosmotic agents such as dimethyl sulfoxide(DMSO) have been used as enhancers for tissue optical clearing technique. However, previous investigations showed that DMSO can induce bradycardia, respiratory problems, and alterations in blood pressure. Also, DMSO could potentially alter the chemical structure, and hence the functional properties, of cell membranes. In this talk, Borneol among natural and nontoxic CTMs was introduced as new enhancer for optical clearing of porcine skin tissue since it has been widely used as new penetration promoter in the field of trandermial drug delivery system(TDDS) and been proved to be effective. In the first, the spectral characteristics of borneol was obtained and analyzed by Fourier Transformation Infrared (FTIR) spectrophotometer. And further experimental studies were performed to probe if borneol is capable of optical clearing of porcine skin tissue in vitro with near infrared spectroscopy, double integrating-spheres system and Inverse Adding-Doubling(IAD) algorithm. Spectral results show that light penetration depth into skin tissue got the increase. Meanwhile, absorption coefficient and scattering coefficient of porcine skin treated by borneol got the decrease during the permeation of Borneol. Therefore, Borneol could be potentially used as enhancer for tissue optical clearing to improve non-invasive light-based diagnostic and imaging techniques while practically optical application and clinical safety are under consideration.

Specalyzer—an interactive online tool to analyze spectral reflectance measurements

Directory of Open Access Journals (Sweden)

Alexander Koc

2018-06-01

Full Text Available Low-cost phenotyping using proximal sensors is increasingly becoming popular in plant breeding. As these techniques generate a large amount of data, analysis pipelines that do not require expertise in computer programming can benefit a broader user base. In this work, a new online tool Specalyzer is presented that allows interactive analysis of the spectral reflectance data generated by proximal spectroradiometers. Specalyzer can be operated from any web browser allowing data uploading, analysis, interactive plots and exporting by point and click using a simple graphical user interface. Specalyzer is evaluated with case study data from a winter wheat fertilizer trial with two fertilizer treatments. Specalyzer can be accessed online at http://www.specalyzer.org.

Unified analysis of ensemble and single-complex optical spectral data from light-harvesting complex-2 chromoproteins for gaining deeper insight into bacterial photosynthesis

Science.gov (United States)

Pajusalu, Mihkel; Kunz, Ralf; Rätsep, Margus; Timpmann, Kõu; Köhler, Jürgen; Freiberg, Arvi

2015-11-01

Bacterial light-harvesting pigment-protein complexes are very efficient at converting photons into excitons and transferring them to reaction centers, where the energy is stored in a chemical form. Optical properties of the complexes are known to change significantly in time and also vary from one complex to another; therefore, a detailed understanding of the variations on the level of single complexes and how they accumulate into effects that can be seen on the macroscopic scale is required. While experimental and theoretical methods exist to study the spectral properties of light-harvesting complexes on both individual complex and bulk ensemble levels, they have been developed largely independently of each other. To fill this gap, we simultaneously analyze experimental low-temperature single-complex and bulk ensemble optical spectra of the light-harvesting complex-2 (LH2) chromoproteins from the photosynthetic bacterium Rhodopseudomonas acidophila in order to find a unique theoretical model consistent with both experimental situations. The model, which satisfies most of the observations, combines strong exciton-phonon coupling with significant disorder, characteristic of the proteins. We establish a detailed disorder model that, in addition to containing a C2-symmetrical modulation of the site energies, distinguishes between static intercomplex and slow conformational intracomplex disorders. The model evaluations also verify that, despite best efforts, the single-LH2-complex measurements performed so far may be biased toward complexes with higher Huang-Rhys factors.

Towards spectral-domain optical coherence tomography on a silicon chip

NARCIS (Netherlands)

Akça, B.I.; Worhoff, Kerstin; Nguyen, V.D.; Kalkman, J.; van Leeuwen, Ton; de Ridder, R.M.; Pollnau, Markus

Optical coherence tomography (OCT) is a widely used optical imaging technology, particularly in the medical field, since it can provide non-invasive, sub-micrometer resolution diagnostic images of tissue. Current OCT systems contain optical fibers and free-space optical components which make these

Broad-band spectral studies of optical lightnings and possible correlation with solar activity

International Nuclear Information System (INIS)

Bhat, C.L.; Sapru, M.L.; Kaul, R.K.; Razdan, H.

1984-01-01

Optical pulses from lightning discharges have been recorded in a ground-based experiment, meant primarily for the detection of cosmic X- and γ-ray bursts through the atmospheric fluorescence technique. It is shown that the spectral ratio Asub(v)/Asub(y), i.e. the ratio of pulse amplitudes in the violet to that in yellow wavelength bands (3400-4300 A and 4400-6000 A respectively) provides a good indication of the lightning channel temperature, the range of derived temperatures extending from 5.000 K to 60.000 K. Based on the distribution of observed Asub(v)/Asub(y) values on a daily basis, it has been possible to separate the observed lightning activity into two classes. One class of event is shown to be correlated with the peaking of the global atmospheric electric field and occurs preferentially on days when the ground-level cosmic ray intensity shows a significant decrease in association with an increase in geomagnetic activity. The results are discussed in terms of the contemporary views regarding solar control of atmospheric electricity and the various sun-weather correlations reported earlier. (author)

The hand-hold polarization-sensitive spectral domain optical coherence and its applications

Science.gov (United States)

Liu, Hao; Gao, Wanrong

2017-08-01

The polarization-sensitive spectral domain optical coherence tomography (PSOCT) has the advantages of being able to measure the polarization properties of samples, such as phase-retardation, diattenuation, depolarization, and optical axis orientation, providing a contrast to identify the diseased area and normal area in tissues in PSOCT images. Conventionally, the sample arm of PSOCT is fixed on the stage where biomedical tissues or models is placed, and the OCT images is acquired by scanning with a galvanometer-based mirror. To be applied in the practical diagnosis, a promising way is to design a hand-held device. To this end, it is required that probe is assembled with a small volume to allow for comprehensively imaging large tissues areas at a microscopic scale, and is available to move on different samples to be acquired quickly with negligible motion artifacts. Meanwhile, the probe should be manufactured wih well stability to avoid system jitter error while it is used to detect the biological tissues in vivo. In this work, a design of a hand-hold fiber-based PSOCT is described. The device is of the size of 10 cm (length) × 8 cm (width) × 6 cm (height). Both the axial resolution and the imaging depth of the system are measured and were approximately 7 μm and 2.5 mm in air, respectively, which are in good agreement with the theoretical predictions. The A-scan rate of the system is 70 kHz. The structure is compact and all the components are fixed on the shell to reduce the motion artifact, resulting in a great stability on measuring the tissues in vivo. The cross sectional images of ex vivo chicken breast, ex vivo pork cartilage and in vivo forearm skin of human wolunteer are presented to demonstrate the capability of the system.

THE INFRARED TELESCOPE FACILITY (IRTF) SPECTRAL LIBRARY: COOL STARS

International Nuclear Information System (INIS)

Rayner, John T.; Cushing, Michael C.; Vacca, William D.

2009-01-01

We present a 0.8-5 μm spectral library of 210 cool stars observed at a resolving power of R ≡ λ/Δλ ∼ 2000 with the medium-resolution infrared spectrograph, SpeX, at the 3.0 m NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. The stars have well-established MK spectral classifications and are mostly restricted to near-solar metallicities. The sample not only contains the F, G, K, and M spectral types with luminosity classes between I and V, but also includes some AGB, carbon, and S stars. In contrast to some other spectral libraries, the continuum shape of the spectra is measured and preserved in the data reduction process. The spectra are absolutely flux calibrated using the Two Micron All Sky Survey photometry. Potential uses of the library include studying the physics of cool stars, classifying and studying embedded young clusters and optically obscured regions of the Galaxy, evolutionary population synthesis to study unresolved stellar populations in optically obscured regions of galaxies and synthetic photometry. The library is available in digital form from the IRTF Web site.

Tunable thin-film optical filters for hyperspectral microscopy

Science.gov (United States)

Favreau, Peter F.; Rich, Thomas C.; Prabhat, Prashant; Leavesley, Silas J.

2013-02-01

Hyperspectral imaging was originally developed for use in remote sensing applications. More recently, it has been applied to biological imaging systems, such as fluorescence microscopes. The ability to distinguish molecules based on spectral differences has been especially advantageous for identifying fluorophores in highly autofluorescent tissues. A key component of hyperspectral imaging systems is wavelength filtering. Each filtering technology used for hyperspectral imaging has corresponding advantages and disadvantages. Recently, a new optical filtering technology has been developed that uses multi-layered thin-film optical filters that can be rotated, with respect to incident light, to control the center wavelength of the pass-band. Compared to the majority of tunable filter technologies, these filters have superior optical performance including greater than 90% transmission, steep spectral edges and high out-of-band blocking. Hence, tunable thin-film optical filters present optical characteristics that may make them well-suited for many biological spectral imaging applications. An array of tunable thin-film filters was implemented on an inverted fluorescence microscope (TE 2000, Nikon Instruments) to cover the full visible wavelength range. Images of a previously published model, GFP-expressing endothelial cells in the lung, were acquired using a charge-coupled device camera (Rolera EM-C2, Q-Imaging). This model sample presents fluorescently-labeled cells in a highly autofluorescent environment. Linear unmixing of hyperspectral images indicates that thin-film tunable filters provide equivalent spectral discrimination to our previous acousto-optic tunable filter-based approach, with increased signal-to-noise characteristics. Hence, tunable multi-layered thin film optical filters may provide greatly improved spectral filtering characteristics and therefore enable wider acceptance of hyperspectral widefield microscopy.

Optical and structural properties of nanostructured CeO2:Tb3+ film

International Nuclear Information System (INIS)

Ansari, Anees A.; Singh, S.P.; Malhotra, B.D.

2011-01-01

Nanostructured CeO 2 :Tb 3+ film has been fabricated on glass substrate through sol-gel technique via dip-coating process. (NH 4 ) 2 Ce(NO 3 ) 6 , Tb(NO 3 ) 3 .6H 2 O, ethylene glycol have been used as precursors for sol preparation. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV/VIS and photoluminescence (PL) spectral studies have been employed to analyze the structural and optical properties of the film. XRD pattern has been used to analyze the crystallite nature and calculated particle size by Scherrer equation of nanostructured CeO 2 :Tb 3+ film, found in the range 3-4 nm. SEM image has been observed to analyze the surface topography of the film which is well porous, highly agglomerated and uniformly distributed nanoparticles on the film surface. Optical band gap of nanostructured CeO 2 :Tb 3+ film has been estimated as 3.57 eV. A significant enhancement in band shape of CeO 2 :Tb 3+ spectrum has been observed in PL spectra, showed their promising usages as optical materials in optoelectronic devices.

Performance of the Multi-Spectral Solar Telescope Array. III - Optical characteristics of the Ritchey-Chretien and Cassegrain telescopes