Science.gov

Sample records for accessible wavelength range

  1. Alternative wavelengths for laser ranging

    NASA Technical Reports Server (NTRS)

    Hamal, Karel

    1993-01-01

    The following are considered to be necessary to accomplish multicolor laser ranging: the nature of the atmospheric dispersion and absorption, the satellite/lunar/ground retro-array characteristics, and ground/satellite ranging machine performance. The energy balance and jitter budget have to be considered as well. It is concluded that the existing satellite/laser retroreflectors seem inadequate for future experiments. The Raman Stokes/Anti-Stokes (0.68/0.43 micron) plus solid state detector appear to be promising instrumentation that satisfy the ground/satellite and satellite/ground ranging machine requirements on the precision, compactness, and data processing.

  2. Two wavelength satellite laser ranging using SPAD

    NASA Technical Reports Server (NTRS)

    Prochazka, Ivan; Hamal, Karel; Jelinkova, Helena; Kirchner, Georg; Koidl, F.

    1993-01-01

    When ranging to satellites with lasers, there are several principal contributions to the error budget: from the laser ranging system on the ground, from the satellite retroarray geometry, and from the atmosphere. Using a single wavelength, we have routinely achieved a ranging precision of 8 millimeters when ranging to the ERS-1 and Starlette satellites. The systematic error of the atmosphere, assuming the existing dispersion models, is expected to be of the order of 1 cm. Multiple wavelengths ranging might contribute to the refinement of the existing models. Taking into account the energy balance, the existing picosecond lasers and the existing receiver and detection technology, several pairs or multiple wavelengths may be considered. To be able to improve the atmospheric models to the subcentimeter accuracy level, the differential time interval (DTI) has to be determined within a few picoseconds depending on the selected wavelength pair. There exist several projects based on picosecond lasers as transmitters and on two types of detection techniques: one is based on photodetectors, like photomultipliers or photodiodes connected to the time interval meters. Another technique is based on the use of a streak camera as an echo signal detector, temporal analyzer, and time interval vernier. The temporal analysis at a single wavelength using the streak camera showed the complexity of the problem.

  3. Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

    SciTech Connect

    Kita, Tomohiro Tang, Rui; Yamada, Hirohito

    2015-03-16

    We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

  4. Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

    NASA Astrophysics Data System (ADS)

    Kita, Tomohiro; Tang, Rui; Yamada, Hirohito

    2015-03-01

    We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

  5. Two-Dimensional Electronic Spectroscopy in the Ultraviolet Wavelength Range.

    PubMed

    West, Brantley A; Moran, Andrew M

    2012-09-20

    Coherent two-dimensional (2D) spectroscopies conducted at visible and infrared wavelengths are having a transformative impact on the understanding of numerous processes in condensed phases. The extension of 2D spectroscopy to the ultraviolet spectral range (2DUV) must contend with several challenges, including the attainment of adequate laser bandwidth, interferometric phase stability, and the suppression of undesired nonlinearities in the sample medium. Solutions to these problems are motivated by the study of a wide range of biological systems whose lowest-frequency electronic resonances are found in the UV. The development of 2DUV spectroscopy also makes possible the attainment of new insights into elementary chemical reaction dynamics (e.g., electrocyclic ring opening in cycloalkenes). Substantial progress has been made in both the implementation and application of 2DUV spectroscopy in the past several years. In this Perspective, we discuss 2DUV methodology, review recent applications, and speculate on what the future will hold.

  6. Emissivity range constraints algorithm for multi-wavelength pyrometer (MWP).

    PubMed

    Xing, Jian; Rana, R S; Gu, Weihong

    2016-08-22

    In order to realize rapid and real temperature measurement for high temperature targets by multi-wavelength pyrometer (MWP), emissivity range constraints to optimize data processing algorithm without effect from emissivity has been developed. Through exploring the relation between emissivity deviation and true temperature by fitting of large number of data from different emissivity distribution target models, the effective search range of emissivity for every time iteration is obtained, so data processing time is greatly reduced. Simulation and experimental results indicate that calculation time is less by 0.2 seconds with 25K absolute error at 1800K true temperature, and the efficiency is improved by more than 90% compared with the previous algorithm. The method has advantages of simplicity, rapidity, and suitability for in-line high temperature measurement.

  7. Emissivity range constraints algorithm for multi-wavelength pyrometer (MWP).

    PubMed

    Xing, Jian; Rana, R S; Gu, Weihong

    2016-08-22

    In order to realize rapid and real temperature measurement for high temperature targets by multi-wavelength pyrometer (MWP), emissivity range constraints to optimize data processing algorithm without effect from emissivity has been developed. Through exploring the relation between emissivity deviation and true temperature by fitting of large number of data from different emissivity distribution target models, the effective search range of emissivity for every time iteration is obtained, so data processing time is greatly reduced. Simulation and experimental results indicate that calculation time is less by 0.2 seconds with 25K absolute error at 1800K true temperature, and the efficiency is improved by more than 90% compared with the previous algorithm. The method has advantages of simplicity, rapidity, and suitability for in-line high temperature measurement. PMID:27557198

  8. Performance of an optical equalizer in a 10 G wavelength converting optical access network.

    PubMed

    Mendinueta, José Manuel D; Cao, Bowen; Thomsen, Benn C; Mitchell, John E

    2011-12-12

    A centralized optical processing unit (COPU) that functions both as a wavelength converter (WC) and optical burst equaliser in a 10 Gb/s wavelength-converting optical access network is proposed and experimentally characterized. This COPU is designed to consolidate drifting wavelengths generated with an uncooled laser in the upstream direction into a stable wavelength channel for WDM backhaul transmission and to equalize the optical loud/soft burst power in order to relax the burst-mode receiver dynamic range requirement. The COPU consists of an optical power equaliser composed of two cascaded SOAs followed by a WC. Using an optical packet generator and a DC-coupled PIN-based digital burst-mode receiver, the COPU is characterized in terms of payload-BER for back-to-back and backhaul transmission distances of 22, 40, and 62 km. We show that there is a compromise between the receiver sensitivity and overload points that can be optimized tuning the WC operating point for a particular backhaul fiber transmission distance. Using the optimized settings, sensitivities of -30.94, -30.17, and -27.26 dBm with overloads of -9.3, -5, and >-5 dBm were demonstrated for backhaul transmission distances of 22, 40 and 62 km, respectively. PMID:22274023

  9. Exploring the wavelength range of InP/AlGaInP QDs and application to dual-state lasing

    NASA Astrophysics Data System (ADS)

    Shutts, Samuel; Elliott, Stella N.; Smowton, Peter M.; Krysa, Andrey B.

    2015-04-01

    We explore the accessible wavelength range offered by InP/AlGaInP quantum dots (QD)s grown by metal-organic vapour phase epitaxy and explain how changes in growth temperature and wafer design can be used to influence the transition energy of the dot states and improve the performance of edge-emitting lasers. The self assembly growth method of these structures creates a multi-modal distribution of inhomogeneously broadened dot sizes, and via the effects of state-filling, allows access to a large range of lasing wavelengths. By characterising the optical properties of these dots, we have designed and demonstrated dual-wavelength lasers which operate at various difference-wavelengths between 8 and 63 nm. We show that the nature of QDs allows the difference-wavelength to be tuned by altering the operating temperature at a rate of up to 0.12 nm K-1 and we investigate the factors affecting intensity stability of the competing modes.

  10. Wide-capture-range, high-precision wavelength stabilization within ±50 MHz for flexible-grid wavelength division multiplexing by photomixing technique

    NASA Astrophysics Data System (ADS)

    Tsuboi, Jun; Kuboki, Takeshi; Kato, Kazutoshi

    2016-08-01

    The lasers for the flexible-grid wavelength division multiplexing (WDM) system are required to have high precision of wavelength stability. Previously, we proposed the wavelength-controlling system of the distributed feedback laser diode (DFB-LD) with the photomixing technique and a microwave filter to precisely measure the optical frequency error from the target value. To enlarge the wavelength-capture range, we improve the system to detect the wavelength error with two different microwave filters in parallel. Experimental results show that the wavelength-capture range is extended up to 4 GHz while the wavelength error is still kept within ±50 MHz.

  11. Experimental demonstration of wavelength domain rogue-free ONU based on wavelength-pairing for TDM/WDM optical access networks.

    PubMed

    Lee, Jie Hyun; Park, Heuk; Kang, Sae-Kyoung; Lee, Joon Ki; Chung, Hwan Seok

    2015-11-30

    In this study, we propose and experimentally demonstrate a wavelength domain rogue-free ONU based on wavelength-pairing of downstream and upstream signals for time/wavelength division-multiplexed optical access networks. The wavelength-pairing tunable filter is aligned to the upstream wavelength channel by aligning it to one of the downstream wavelength channels. Wavelength-pairing is implemented with a compact and cyclic Si-AWG integrated with a Ge-PD. The pairing filter covered four 100 GHz-spaced wavelength channels. The feasibility of the wavelength domain rogue-free operation is investigated by emulating malfunction of the misaligned laser. The wavelength-pairing tunable filter based on the Si-AWG blocks the upstream signal in the non-assigned wavelength channel before data collision with other ONUs.

  12. Spectral fluorescent properties of tissues in vivo with excitation in the red wavelength range

    NASA Astrophysics Data System (ADS)

    Stratonnikov, Alexander A.; Loschenov, Victor B.; Klimov, D. V.; Edinac, N. E.; Wolnukhin, V. A.; Strashkevich, I. A.

    1997-12-01

    The spectral fluorescence analysis is a promising method for differential tissue diagnostic. Usually the UV and visible light is used for fluorescence excitation with emission registration in the visible wavelength range. The light penetration length in this wavelength range is very small allowing one to analyze only the surface region of the tissue. Here we present the tissue fluorescent spectra in vivo excited in the red wavelength region. As excitation light source we used compact He-Ne laser (632.8 nm) and observed the fluorescence in 650 - 800 nm spectral range. The various tissues including normal skin, psoriasis, tumors, necrosis as well as photosensitized tissues have been measured.

  13. Effects of various wavelength ranges of vacuum ultraviolet radiation on Teflon® FEP film

    NASA Astrophysics Data System (ADS)

    Dever, Joyce A.; McCracken, Cara A.

    2003-09-01

    This paper describes testing to investigate the effects of vacuum ultraviolet (VUV) radiation on Teflon® fluorinated ethylene propylene (FEP) film, examining differences in mechanical properties degradation for samples of 50.8 μm thickness exposed to VUV of various lower cut-off wavelengths. Samples were exposed in a high vacuum facility to VUV lamps, which produce radiation in the 115-400 nm wavelength range, but with the highest intensity produced below 200 nm. Windows of fused silica, crystalline quartz, and magnesium fluoride provided lower cut-off wavelengths of 155, 140, and 115 nm, respectively. Lamp intensity was measured in the 115-200 nm wavelength range throughout the sample exposures, and these data were used to estimate intensity and incident energy in various wavelength ranges, between 115 and 400 nm. Samples were analyzed for tensile strength and elongation at failure. The effects of the different wavelength ranges were compared and discussed in terms of the expected depth to which various wavelengths are deposited into FEP.

  14. Multi-wavelength access gate for WDM-formatted words in optical RAM row architectures

    NASA Astrophysics Data System (ADS)

    Fitsios, D.; Alexoudi, T.; Vagionas, C.; Miliou, A.; Kanellos, G. T.; Pleros, N.

    2013-03-01

    Optical RAM has emerged as a promising solution for overcoming the "Memory Wall" of electronics, indicating the use of light in RAM architectures as the approach towards enabling ps-regime memory access times. Taking a step further towards exploiting the unique wavelength properties of optical signals, we reveal new architectural perspectives in optical RAM structures by introducing WDM principles in the storage area. To this end, we demonstrate a novel SOAbased multi-wavelength Access Gate for utilization in a 4x4 WDM optical RAM bank architecture. The proposed multiwavelength Access Gate can simultaneously control random access to a 4-bit optical word, exploiting Cross-Gain-Modulation (XGM) to process 8 Bit and Bit channels encoded in 8 different wavelengths. It also suggests simpler optical RAM row architectures, allowing for the effective sharing of one multi-wavelength Access Gate for each row, substituting the eight AGs in the case of conventional optical RAM architectures. The scheme is shown to support 10Gbit/s operation for the incoming 4-bit data streams, with a power consumption of 15mW/Gbit/s. All 8 wavelength channels demonstrate error-free operation with a power penalty lower than 3 dB for all channels, compared to Back-to-Back measurements. The proposed optical RAM architecture reveals that exploiting the WDM capabilities of optical components can lead to RAM bank implementations with smarter column/row encoders/decoders, increased circuit simplicity, reduced number of active elements and associated power consumption. Moreover, exploitation of the wavelength entity can release significant potential towards reconfigurable optical cache mapping schemes when using the wavelength dimension for memory addressing.

  15. Absolute absorption cross sections of ozone in the 185- to 350-nm wavelength range

    NASA Technical Reports Server (NTRS)

    Molina, L. T.; Molina, M. J.

    1986-01-01

    The absorption cross sections of ozone have been measured in the wavelength range 185-350 nm and in the temperature range 225-298 K. The absolute ozone concentrations were established by measuring the pressure of pure gaseous samples in the 0.08to 300-torr range, and the UV spectra were recorded under conditions where less than 1 percent of the sample decomposed. The temperature dependence is significant for wavelengths longer than about 280 nm. The absorption cross-section values around 210 nm were found to be about 10 percent larger than the previously accepted values.

  16. Photon Counting Detectors for the 1.0 - 2.0 Micron Wavelength Range

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.

    2004-01-01

    We describe results on the development of greater than 200 micron diameter, single-element photon-counting detectors for the 1-2 micron wavelength range. The technical goals include quantum efficiency in the range 10-70%; detector diameter greater than 200 microns; dark count rate below 100 kilo counts-per-second (cps), and maximum count rate above 10 Mcps.

  17. Detection range enhancement using circularly polarized light in scattering environments for infrared wavelengths

    SciTech Connect

    van der Laan, J. D.; Scrymgeour, D. A.; Kemme, S. A.; Dereniak, E. L.

    2015-03-13

    We find for infrared wavelengths there are broad ranges of particle sizes and refractive indices that represent fog and rain where the use of circular polarization can persist to longer ranges than linear polarization. Using polarization tracking Monte Carlo simulations for varying particle size, wavelength, and refractive index, we show that for specific scene parameters circular polarization outperforms linear polarization in maintaining the intended polarization state for large optical depths. This enhancement with circular polarization can be exploited to improve range and target detection in obscurant environments that are important in many critical sensing applications. Specifically, circular polarization persists better than linear for radiation fog in the short-wave infrared, for advection fog in the short-wave infrared and the long-wave infrared, and large particle sizes of Sahara dust around the 4 micron wavelength.

  18. Detection range enhancement using circularly polarized light in scattering environments for infrared wavelengths

    DOE PAGES

    van der Laan, J. D.; Sandia National Lab.; Scrymgeour, D. A.; Kemme, S. A.; Dereniak, E. L.

    2015-03-13

    We find for infrared wavelengths there are broad ranges of particle sizes and refractive indices that represent fog and rain where the use of circular polarization can persist to longer ranges than linear polarization. Using polarization tracking Monte Carlo simulations for varying particle size, wavelength, and refractive index, we show that for specific scene parameters circular polarization outperforms linear polarization in maintaining the intended polarization state for large optical depths. This enhancement with circular polarization can be exploited to improve range and target detection in obscurant environments that are important in many critical sensing applications. Specifically, circular polarization persists bettermore » than linear for radiation fog in the short-wave infrared, for advection fog in the short-wave infrared and the long-wave infrared, and large particle sizes of Sahara dust around the 4 micron wavelength.« less

  19. TCSPC FLIM in the wavelength range from 800 nm to 1700 nm (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Becker, Wolfgang; Shcheslavsky, Vladislav

    2016-03-01

    Excitation and detection in the wavelength range above 800nm is a convenient and relatively inexpensive way to increase the penetration depth in optical microscopy. Moreover, detection at long wavelength avoids the problem that tissue autofluorescence contaminates the signals from endogenous fluorescence probes. FLIM at NIR wavelength may therefore be complementary to multiphoton microscopy, especially if the lifetimes of NIR fluorophores report biological parameters of the tissue structures they are bound to. Unfortunately, neither the excitation sources nor the detectors of standard confocal and multiphoton laser scanning systems are directly suitable for excitation and detection of NIR fluorescence. Most of these problems can be solved, however, by using ps diode lasers or Ti:Sapphire lasers at their fundamental wavelength, and NIR-sensitive detectors. With NIR-sensitive PMTs the detection wavelength range can be extended up to 900 nm, with InGaAs SPAD detectors up to 1700 nm. Here, we demonstrate the use of a combination of laser scanning, multi-dimensional TCSPC, and advanced excitation sources and detectors for FLIM at up to 1700 nm. The performance was tested at tissue samples incubated with NIR dyes. The fluorescence lifetimes generally get shorter with increasing absorption and emission wavelengths of the dyes. For the cyanine dye IR1061, absorbing around 1060 nm, the lifetime was found to be as short as 70 ps. Nevertheless the fluorescence decay could still be clearly detected. Almost all dyes showed clear lifetime changes depending on the binding to different tissue constituents.

  20. Best dynamic wavelength range for shock detection via blood vessel density pattern

    NASA Astrophysics Data System (ADS)

    Kanawade, Rajesh; Saiko, Gennadiy; Douplik, Alexandre

    Diffuse reflectance spectroscopy is a non-invasive or minimally invasive medical diagnostic modality. Still challenges in noninvasive tools for early shock detection are unresolved especially in spatial resolution and broad range of sampling wavelength for reduced-/ oxy-hemoglobin concentrations detection from tissue sample. To minimize these limitations, we have developed a novel method based on spatially and spectrally resolved diffuse reflectance for shock detection. This study was performed to pick up best dynamic wavelength range sets to detect fine vessel density pattern modulation for shock detection.

  1. Evaluation wavelength range mapping, a tool to optimize the evaluation window in differential absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Vogel, L.; Sihler, H.; Lampel, J.; Wagner, T.; Platt, U.

    2012-04-01

    Optical remote sensing via Differential Optical Absorption Spectroscopy (DOAS) has become a standard technique to assess various trace gases in the atmosphere. Measurement instruments are usually classified into active instruments applying an artificial light source and passive instruments using natural light sources, e.g., scattered or direct sunlight. Platforms range from ground based to satellites and trace gases are studied in all kinds of different environments. Naturally, the evaluation of gathered spectra needs to be tuned to each specific case and trace gas of interest due to the wide range of measurement conditions, atmospheric compositions and instruments used. A well chosen evaluation wavelength range is crucial to the DOAS technique. It should be as large as possible and include the largest differential absorption features of the trace gas of interest in order to maximize sensitivity. However, the differential optical densities of other absorbers should be minimized in order to prevent interferences between different absorption cross sections. Furthermore, instrumental specific features and wavelength dependent radiative transfer effects may have malicious effects and lead to erroneous values. Usually a compromise needs to be found depending on the conditions at hand. Evaluation wavelength range mapping is an easily applied tool to visualize wavelength depending evaluation features of DOAS and to find the optimal retrieval wavelength range. As an example, synthetic spectra are studied which simulate passive DOAS measurements of stratospheric bromine monoxide (BrO) by Zenith-DOAS and Multi-Axis DOAS (MAX-DOAS) measurements of BrO in volcanic plumes. The influence of the I0-effect and the Ring-effect on the respective retrievals are demonstrated. However, due to the general nature of the tool it is applicable to any DOAS measurement and the technique also allows to study any other wavelength dependent influences on retrieved trace gas columns.

  2. [A Concept Design of Flat-Field Spectrograph for Wide Wavelength Range].

    PubMed

    Li, Shi-yuan; Zhang, Guang-cai; Teng, Ai-ping

    2015-05-01

    The radiation spectrum from the plasmas contains a large amount of information of plasmas. Thus, one of the most effective methods to detecting the plasma parameters is measure the plasma radiation spectrum. Until now, since the restriction of the Toshiba mechanically ruled aberration-corrected concave gratings, the measurable wavelength range of the incidence flat-field grazing spectrometer in the soft X-ray range are only from 5 to 40 nm. In order to extend the wavelength rang of grazing incidence flat-field spectrometer, first, a grazing incidence concave reflection grating ray-trace code is written using optical path equation. Second, under the same conditions with reference 6, we compare our numerical results with Harada's results. The results show that our results agree very well with the results of Harada. The results of comparison show that our ray-trace code is believable. Finally, the variety of the flat-field curves are detailedly investigated using the ray-trace code with the different grazing incidence conditions. The results show that the measurable wavelength range of the incidence flat-field grazing spectrometer are extended to 5~80 nm from the soft X-ray wavelength range of 5~40 nm. This result theoretically demonstrates the possibility of expanded the traditional band flat-field grazing incidence spectrometer from soft X-ray band to the extreme ultraviolet (XUV), and also bring a new design ideas for improving the use of grazing incidence flat field concave grating.

  3. Broadband tuning of continuous wave quantum cascade lasers in long wavelength (> 10 μm) range.

    PubMed

    Dougakiuchi, Tatsuo; Fujita, Kazuue; Sugiyama, Atsushi; Ito, Akio; Akikusa, Naota; Edamura, Tadataka

    2014-08-25

    Broadband spectral tuning in the long wavelength range (greater than 10 μm) was demonstrated with an external-cavity quantum cascade laser. The tunable wavelength of the laser ranged from 9.5 to 11.4 μm (176 cm(-1); corresponding to 18% of the center wavelength) in continuous wave (cw) operation at room temperature, without any anti-reflection coating. The gain chip based on the anti-crossed dual-upper-state (DAU) design provided a cw lasing up to 300 K, with a low threshold current density of 2.1 kA/cm2. The highly stable broadband spectral tuning and high laser performance were enabled by the spectrally homogeneous gain profile of the anti-crossed DAU active region.

  4. Three-dimensional range-gated imaging at infrared wavelengths with super-resolution depth mapping

    NASA Astrophysics Data System (ADS)

    Laurenzis, Martin; Christnacher, Frank; Metzger, Nicolas; Bacher, Emmanuel; Zielenski, Ingo

    2009-05-01

    Range-gated viewing is a prominent technique for night vision, remote sensing and vision trough obstacles (fog, smoke, camouflage netting ). Furthermore, range-gated images reflect not only the scene reflectance but also contain depth information. The whole depth information can be calculated from a minimum number of two range-gated images via the super-resolution depth mapping technique. For the first time, this method is applied to range-gated viewing at infrared wavelengths. An EBCMOS camera and a solid sate laser illumination in the 1.5 μm wavelength scale were used to depth-map a scene with minimal laser activity of 9 ns per image.

  5. III-V-on-silicon integrated micro - spectrometer for the 3 μm wavelength range.

    PubMed

    Muneeb, M; Vasiliev, A; Ruocco, A; Malik, A; Chen, H; Nedeljkovic, M; Penades, J S; Cerutti, L; Rodriguez, J B; Mashanovich, G Z; Smit, M K; Tourni, E; Roelkens, G

    2016-05-01

    A compact (1.2 mm2) fully integrated mid-IR spectrometer operating in the 3 μm wavelength range is presented. To our knowledge this is the longest wavelength integrated spectrometer operating in the important wavelength window for spectroscopy of organic compounds. The spectrometer is based on a silicon-on-insulator arrayed waveguide grating filter. An array of InAs0.91Sb0.09 p-i-n photodiodes is heterogeneously integrated on the spectrometers output grating couplers using adhesive bonding. The spectrometer insertion loss is less than 3 dB and the waveguide-referred responsivity of the integrated photodiodes at room temperature is 0.3 A/W.

  6. Spectroscopic technique with wide range of wavelength information improves near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Eda, Hideo; Aoki, Hiromichi; Eura, Shigeru; Ebe, Kazutoshi

    2009-02-01

    Near-infrared spectroscopy (NIRS) calculates hemoglobin parameters, such as oxygenated hemoglobin (oxyHb) and deoxygenated hemoglobin (deoxyHb) using the near-infrared light around the wavelength of 800nm. This is based on the modified-Lambert-Beer's law that changes in absorbance are proportional to changes in hemoglobin parameters. Many conventional measurement methods uses only a few wavelengths, however, in this research, basic examination of NIRS measurement was approached by acquiring wide range of wavelength information. Venous occlusion test was performed by using the blood pressure cuff around the upper arm. Pressure of 100mmHg was then applied for about 3 minutes. During the venous occlusion, the spectrum of the lower arm muscles was measured every 15 seconds, within the range of 600 to 1100nm. It was found that other wavelength bands hold information correlating to this venous occlusion task. Technique of improving the performance of NIRS measurement using the Spectroscopic Method is very important for Brain science.

  7. Autodyne interferometry for range-finding under laser radiation wavelength modulation

    NASA Astrophysics Data System (ADS)

    Usanov, D. A.; Skripal', A. V.; Astakhov, E. I.; Dobdin, S. Yu.

    2016-09-01

    The results of solution of the inverse problem of determining the distance to the reflector in the case of current modulation of the laser radiation wavelength are presented. It is shown that current modulation of the autodyne signal amplitude can reduce the inverse problem of finding the distance to the reflector to a state of affairs characteristic only of phase modulation. The technique that we propose provides a higher range-finding accuracy than does direct analysis of the autodyne signal.

  8. Recirculating photonic filter: a wavelength-selective time delay for phased-array antennas and wavelength code-division multiple access.

    PubMed

    Yegnanarayanan, S; Trinh, P D; Jalali, B

    1996-05-15

    A novel wavelength-selective photonic time-delay filter is proposed and demonstrated. The device consists of an optical phased-array waveguide grating in a recirculating feedback configuration. It can function as a true-time-delay generator for squint-free beam steering in optically controlled phased-array antennas and as an encoding-decoding filter for wavelength code-division multiple access.

  9. Multi-channel access technology based on wavelength division multiplexing in wireless UV communication mesh network

    NASA Astrophysics Data System (ADS)

    Zhao, Tai-fei; Zhang, Ai-li; Xue, Rong-li

    2013-05-01

    In this paper, the multi-channel access technology of wavelength division multiplexing (WDM) in the wireless ultraviolet (UV) scattering communication is studied. A multi-interface and multi-channel device is deployed in each UV transceiver node. The band-pass filter is configured in the receiving node so as to realize the multi-channel access by use of the UV WDM technology. Both the UV communication node model and the UV channel model are established. Three types of UV no-line-of-sight (NLOS) multi-channel communications are simulated in the mesh topologies with NS2. The results show that the UV multi-channel access technology can increase network throughput effectively with using WDM.

  10. Effects of Various Wavelength Ranges of Vacuum Ultraviolet Radiation on Teflon FEP Film Investigated

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; McCracken, Cara A.

    2004-01-01

    Teflon Fluorinated Ethylene Propylene (FTP) films (DuPont) have been widely used for spacecraft thermal control and have been observed to become embrittled and cracked upon exposure to the space environment. This degradation has been attributed to a synergistic combination of radiation and thermal effects. A research study was undertaken at the NASA Glenn Research Center to examine the effects of different wavelength ranges of vacuum ultraviolet (VUV) radiation on the degradation of the mechanical properties of FEP. This will contribute to an overall understanding of space radiation effects on Teflon FEP, and will provide information necessary to determine appropriate techniques for using laboratory tests to estimate space VUV degradation. Research was conducted using inhouse facilities at Glenn and was carried out, in part, through a grant with the Cleveland State University. Samples of Teflon FEP film of 50.8 microns thickness were exposed to radiation from a VUV lamp from beneath different cover windows to provide different exposure wavelength ranges: MgF2 (115 to 400 nm), crystalline quartz (140 to 400 nm), and fused silica (FS, 155 to 400 nm). Following exposure, FEP film specimens were tensile tested to determine the ultimate tensile strength and elongation at failure as a function of the exposure duration for each wavelength range. The graphs show the effect of ultraviolet exposure on the mechanical properties of the FEP samples.

  11. Increment of Access Points in Integrated System of Wavelength Division Multiplexed Passive Optical Network Radio over Fiber.

    PubMed

    Amiri, I S; Alavi, S E; Soltanian, M R K; Fisal, N; Supa'at, A S M; Ahmad, H

    2015-01-01

    This paper describes a novel technique to increase the numbers of access points (APs) in a wavelength division multiplexed-passive optical network (WDM-PON) integrated in a 100 GHz radio-over-fiber (RoF). Eight multi-carriers separated by 25 GHz intervals were generated in the range of 193.025 to 193.200 THz using a microring resonator (MRR) system incorporating an add-drop filter system. All optically generated multi-carriers were utilized in an integrated system of WDM-PON-RoF for transmission of four 43.6 Gb/sec orthogonal frequency division multiplexing (OFDM) signals. Results showed that an acceptable BER variation for different path lengths up to 25 km was achievable for all four access points and thus the transmission of four OFDM channels is feasible for a 25 km standard single mode fiber (SSMF) path length. PMID:26153536

  12. Wavelength dependent near-range lidar profiling of smog aerosol over Athens

    NASA Astrophysics Data System (ADS)

    Stachlewska, Iwona S.; Marinou, Eleni; Engelmann, Ronny; Costa Surós, Montserrat; Kottas, Mickael; Baars, Holger; Janicka, Lucja; Solomos, Stavros; Heese, Birgit; Kumala, Wojciech; Tsekeri, Alexandra; Binietoglou, Ioannis; Markowicz, Krzysztof M.; Amiridis, Vassilis; Balis, Dimitris; Althausen, Dietrich; Wandinger, Ulla; Ansmann, Albert

    2016-04-01

    Recently, the ACTRIS2 JRA1 field campaign focusing on joint remote and in-situ sensing of absorbing aerosols has been conducted in Athens (http://actris-athens.eu). In the frame of the ACTRIS2 BL-Smog TNA, co-located measurements of the near-range lidar receiver (NARLa) of the University of Warsaw with the multi-wavelength PollyXT lidar of the National Observatory of Athens were performed. The excellent capacities of the PollyXT-NOA lidar, equipped with eight far-range channels (355, 355s, 387, 407, 532, 532s, 607, and 1064nm) and two near-range channels (532 and 607 nm), were enhanced by integrating the NARLa for simultaneous observations. By using the NARLa, equipped with the elastic channels (355 and 532nm) and Raman channels (387 and 607nm), the wavelength dependence of the aerosol particles properties within boundary layer was captured. The dominant conditions observed during the JRA1 period were the fresh winter smog layers occurring in lowermost boundary layer over Athens. NARLa provided profiles as close to surface as 50m, thus the data obtained in the near-range were used for the incomplete overlap region of the far-field channels. With NARLa we assessed the overlap at 355 and 532nm wavelengths and concluded on the possibility of using the single near-range 532 nm channel for the overlap correction in both VIS and UV channels of the PollyXT-NOA. As a result, the obtained lidar profiles are expected to be more consistent with the sunphotometer measurements. In the future, the GARRLiC code can be applied on the synergy of combined near and far range lidar profiles with AERONET data sets in order to study improvement on the inversion results.

  13. Magnesium as Novel Material for Active Plasmonics in the Visible Wavelength Range.

    PubMed

    Sterl, Florian; Strohfeldt, Nikolai; Walter, Ramon; Griessen, Ronald; Tittl, Andreas; Giessen, Harald

    2015-12-01

    Investigating new materials plays an important role for advancing the field of nanoplasmonics. In this work, we fabricate nanodisks from magnesium and demonstrate tuning of their plasmon resonance throughout the whole visible wavelength range by changing the disk diameter. Furthermore, we employ a catalytic palladium cap layer to transform the metallic Mg particles into dielectric MgH2 particles when exposed to hydrogen gas. We prove that this transition can be reversed in the presence of oxygen. This yields plasmonic nanostructures with an extinction spectrum that can be repeatedly switched on or off or kept at any intermediate state, offering new perspectives for active plasmonic metamaterials.

  14. Structuring waveguide-grating-based wavelength-division multiplexing/optical code division multiple access network codecs over topology of concentric circles

    NASA Astrophysics Data System (ADS)

    Huang, Jen-Fa; Nieh, Ta-Chun; Chen, Kai-Sheng

    2013-01-01

    The cyclic period and free spectral range of arrayed-waveguide gratings (AWG) in a wavelength-division multiplexing/optical code division multiple access optical code division multiple access network are exploited. The total optical network unit (ONU) of network capacity is partitioned into groups of different wavelength in accordance with the geographical location of subscribers based on the radial distance of the ONU to the optical line terminal. Combining concentric circles round by round for ONU groups enables a fixed round-trip time in the data transmission and a significant increase in system performance. Using AWG router, the proposed topology of concentric circles retains signature orthogonality and minimizes wavelength collisions on the photo-detector. Furthermore, the adoption of extended M-sequence codes corresponding to the AWG codec provides a simpler, more efficient coding procedure and accommodates more users in a single group.

  15. Resonance Raman enhancement optimization in the visible range by selecting different excitation wavelengths

    NASA Astrophysics Data System (ADS)

    Wang, Zhong; Li, Yuee

    2015-09-01

    Resonance enhancement of Raman spectroscopy (RS) has been used to significantly improve the sensitivity and selectivity of detection for specific components in complicated environments. Resonance RS gives more insight into the biochemical structure and reactivity. In this field, selecting a proper excitation wavelength to achieve optimal resonance enhancement is vital for the study of an individual chemical/biological ingredient with a particular absorption characteristic. Raman spectra of three azo derivatives with absorption spectra in the visible range are studied under the same experimental conditions at 488, 532, and 633 nm excitations. Universal laws in the visible range have been concluded by analyzing resonance Raman (RR) spectra of samples. The long wavelength edge of the absorption spectrum is a better choice for intense enhancement and the integrity of a Raman signal. The obtained results are valuable for applying RR for the selective detection of biochemical constituents whose electronic transitions take place at energies corresponding to the visible spectra, which is much friendlier to biologial samples compared to ultraviolet.

  16. Temperature Dependence of Novel Single-Photon Detectors in the Long-Wavelength Infrared Range

    NASA Astrophysics Data System (ADS)

    Ueda, Takeji; An, Zhenghua; Komiyama, Susumu

    2011-05-01

    Novel single-photon detectors, called Charge-sensitive Infrared Phototransistor (CSIP), have been developed in the long wavelength infrared (LWIR) range. The devices are fabricated in GaAs/AlGaAs double-quantum-well (DQW) structure, and do not require ultralow temperatures ( T < 1 K) for operation. Figures of merit are determined in a T-range of 4.2 K˜30 K by using a homemade all-cryogenic spectrometer. We found that the photo-signal persists up to around 30 K. Excellent specific detectivity D * = 9.6 × 1014 cm Hz1/2/W and noise equivalent power NEP = 8.3 × 10-19 W/Hz1/2 are derived up to T = 23 K. The dynamic range of detection exceeds 106, roughly ranging from attowatt to picowatt levels. These values are by a few orders of magnitude higher than that of the state-of-the-art values of other detectors. Simple planar structure of CSIPs is feasible for array fabrication and will make it possible to monolithically integrate with reading circuit. CSIPs are, therefore, not only extremely sensitive but also suitable for practical use in wide ranging applications.

  17. Investigations of Saturn’s Main Rings over Broad Range of Wavelengths

    NASA Astrophysics Data System (ADS)

    Spilker, Linda J.; Deau, Estelle; Morishima, Ryuji; Filacchione, Gianrico; Hedman, Matt; Nicholson, Phil; Colwell, Josh; Bradley, Todd; Showalter, Mark; Pilorz, Stu; Brooks, Shawn; Ciarniello, Mauro

    2015-11-01

    An abundance of information about the characteristics of Saturn’s ring particles and their regolith can be obtained by comparing the changes in their brightness, color and temperature with changing viewing geometry over a wide range of wavelengths from ultraviolet through the thermal infrared. Data from Cassini’s Composite Infrared Spectrometer (CIRS), Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS) and Ultraviolet Imaging Spectrograph (UVIS) are jointly studied using data from the lit and unlit main rings at multiple geometries and solar elevations over 11 years of the Cassini mission. Using multi-wavelength data sets allows us to test different thermal models by combining the effects of particle albedo, regolith grain size and surface roughness with thermal emissivity and inertia, particle spin rate and spin axis orientation.CIRS temperatures, ISS colors and UVIS brightness appear to vary noticeably with phase angle, but are not a strong function of spacecraft elevation angle. Color, temperature and brightness dependence on solar elevation angle are also observed. VIMS observations show that the infrared ice absorption band depths change with the solar phase angle, in particular between 0-20° and at high phase. This trend indicates that single scattering approximation is correct only at low phases (<20°) while at high phase multiple scattering must be taken into account.These results imply that the individual properties of the ring particles may play a larger role than the collective properties of the rings, in particular at visible wavelengths. The temperature and color variation with phase angle may be a result of scattering within the regolith, as well as scattering between individual particles or clumps in a many-particle-thick layer. Initial results from our joint studies will be presented.This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA

  18. Optical access network using centralized light source, single-mode fiber + broad wavelength window multimode fiber

    NASA Astrophysics Data System (ADS)

    Yam, Scott S.-H.; Kim, Jaedon; Gutierrez, David; Achten, Frank

    2006-08-01

    Access networks based on a single-mode fiber (SMF) using a centralized light source (CLS) have attracted much attention recently due to their wavelength management flexibility and potential for cost reduction at customers' premises. Future networks, in addition, are likely to contain segments of multimode fiber (MMF), whose core dimension is relatively large in comparison with its single-mode counterpart, substantially reducing fiber alignment constraints and the subsequent network construction and installation cost. In this study, a CLS-based passive optical network (PON) is proposed, which will use a new generation of high-performance MMF optimized for a broad wavelength transmission window spanning from 1300to1550 nm, with a bandwidth distance product (BDP) of 40 Gbit/s-km. The proposed architecture is implemented in a test bed, and its performance is verified by bit error ratio (BER) measurement. Results show that we can implement high-performance CLS-based PONs containing both an SMF and an MMF infrastructure, simultaneously.

  19. Optical properties of apple skin and flesh in the wavelength range from 350 to 2200 nm

    NASA Astrophysics Data System (ADS)

    Saeys, Wouter; Velazco-Roa, Maria A.; Thennadil, Suresh N.; Ramon, Herman; Nicolaï, Bart M.

    2008-03-01

    Optical measurement of fruit quality is challenging due to the presence of a skin around the fruit flesh and the multiple scattering by the structured tissues. To gain insight in the light-tissue interaction, the optical properties of apple skin and flesh tissue are estimated in the 350-2200 nm range for three cultivars. For this purpose, single integrating sphere measurements are combined with inverse adding-doubling. The observed absorption coefficient spectra are dominated by water in the near infrared and by pigments and chlorophyll in the visible region, whose concentrations are much higher in skin tissue. The scattering coefficient spectra show the monotonic decrease with increasing wavelength typical for biological tissues with skin tissue being approximately three times more scattering than flesh tissue. Comparison to the values from time-resolved spectroscopy reported in literature showed comparable profiles for the optical properties, but overestimation of the absorption coefficient values, due to light losses.

  20. Atlas of Interstellar Extinction Curves of OB Stars Covering the Whole Available Wavelength Range

    NASA Astrophysics Data System (ADS)

    Wegner, W.

    The paper presents a collection of 436 extinction curves covering the whole available range of wavelengths from satellite UV to near-IR. The data were taken from the ANS photometric catalogue and from the compilations of IR photometric measurements. The data curves have been obtained with the aid of ``artificial standards": Papaj et al. (1993) and Wegner (1994, 1995). The visual magnitudes and spectral classifications of O and B type stars with EB-V>= 0.05 were taken from the SIMBAD database. The curves are given in the form of plots and tables E{lambda - V} / EB-V versus 1/λ. The observed variety of extinction laws among slightly reddened stars is apparently due to the various physical parameters of interstellar clouds.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  2. Intercomparison of reflectances observed by GOME and SCIAMACHY in the visible wavelength range.

    PubMed

    Tilstra, Lieuwe G; Stammes, Piet

    2006-06-10

    We compare the Earth reflectances of the spectrometers Global Ozone Monitoring Experiment (GOME) and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) over their overlapping wavelength range (240-800 nm). The goal is to investigate the quality of the radiometric calibration of SCIAMACHY using calibrated GOME data as a reference. However, severe degradation of the GOME instrument in the UV since 2001 prevents it from being a reliable reference below 500 nm. Above 500 nm, GOME is reliable and we find substantial disagreement between GOME and SCIAMACHY, of the order of 15%-20%, which we can attribute completely to the current calibration problems of SCIAMACHY. These numbers are supported by a previous study in which SCIAMACHY was compared with the imager Medium Resolution Imaging Spectrometer (MERIS) onboard the Envisat satellite.

  3. Material processing with ultra-short pulse lasers working in 2μm wavelength range

    NASA Astrophysics Data System (ADS)

    Voisiat, B.; Gaponov, D.; Gečys, P.; Lavoute, L.; Silva, M.; Hideur, A.; Ducros, N.; Račiukaitis, G.

    2015-03-01

    New wavelengths of laser radiation are of interest for material processing. Results of application of the all-fiber ultrashort pulsed laser emitting in 2 µm range, manufactured by Novae, are presented. Average output power was 4.35 W in a single-spatial-mode beam centered at the 1950 nm wavelength. Pulses duration was 40 ps, and laser operated at 4.2 MHz pulse repetition rate. This performance corresponded to 25 kW of pulse peak power and almost 1 µJ in pulse energy. Material processing was performed using three different focusing lenses (100, 30 and 18 mm) and mechanical stages for the workpiece translation. 2 µm laser radiation is strongly absorbed by some polymers. Swelling of PMMA surface was observed for scanning speed above 5 mm/s using the average power of 3.45 W focused with the 30 mm lens. When scanning speed was reduced below 4 mm/s, ablation of PMMA took place. The swelling of PMMA is a consequence of its melting due to absorbed laser power. Therefore, experiments on butt welding of PMMA and overlapping welding of PMMA with other polymers were performed. Stable joint was achieved for the butt welding of two PMMA blocks with thickness of 5 mm. The laser was used to cut a Kapton film on a paper carrier with the same set-up as previous. The cut width depended on the cutting speed and focusing optics. A perfect cut with a width of 11 µm was achieved at the translation speed of 60 mm/s.

  4. High power laser diodes at 14xx nm wavelength range for industrial and medical applications

    NASA Astrophysics Data System (ADS)

    Telkkälä, Jarkko; Boucart, Julien; Krejci, Martin; Crum, Trevor; Lichtenstein, Norbert

    2014-03-01

    We report on the development of the latest generation of high power laser diodes at 14xx nm wavelength range suitable for industrial applications such as plastics welding and medical applications including acne treatment, skin rejuvenation and surgery. The paper presents the newest chip generation developed at II-VI Laser Enterprise, increasing the output power and the power conversion efficiency while retaining the reliability of the initial design. At an emission wavelength around 1440 nm we applied the improved design to a variety of assemblies exhibiting maximum power values as high as 7 W for broad-area single emitters. For 1 cm wide bars on conductive coolers and for bars on active micro channel coolers we have obtained 50 W and 72 W in continuous wave (cw) operation respectively. The maximum power measured for a 1 cm bar operated with 50 μs pulse width and 0.01% duty cycle was 184 W, demonstrating the potential of the chip design for optimized cooling. Power conversion efficiency values as high as 50% for a single emitter device and over 40% for mounted bars have been demonstrated, reducing the required power budget to operate the devices. Both active and conductive bar assembly configurations show polarization purity greater than 98%. Life testing has been conducted at 95 A, 50% duty cycle and 0.5 Hz hard pulsed operation for bars which were soldered to conductive copper CS mounts using our hard solder technology. The results after 5500 h, or 10 million "on-off" cycles show stable operation.

  5. Method and apparatus for generating high power laser pulses in the two to six micron wavelength range

    DOEpatents

    MacPherson, David C.; Nelson, Loren D.; O'Brien, Martin J.

    1996-01-01

    Apparatus performs a method of generating one or more output laser pulses in a range of 2 to 6 microns. When a plurality of the output laser pulses are generated, a first output pulse has any selected wavelength within the range and a second output pulse is temporally closely spaced relative to the first output pulse and has a chosen wavelength differing from the selected wavelength. An oscillator laser cavity is provided with a tunable oscillator rod capable of generating initial laser pulses within a range of from 750 to 1000 nm, and a tuning element is coupled to the rod. A flashlamp is operable to pump the rod. For two pulse operation, the flashlamp has a given duration. A Q-switch provides the initial laser pulses upon operation of the tuning element and the flashlamp. A Raman device coupled to the rod shifts the wavelength of such initial laser pulse into the range of from 2 to 6 microns to form the output laser pulse having a wavelength within the range. For multiple pulses, a controller causes the Q-switch to provide first and second ones of the initial laser pulses, spaced by a time interval less than the given duration. Also, a selector coupled to the tuning element is operable within such duration to successively select the wavelength of the first output pulse and the chosen wavelength of the second initial pulse. The Raman device is responsive to each of the initial light pulses to generate radiation at first and second Stokes wavelengths, each of said the output laser pulses being radiation at the second Stokes wavelength.

  6. Method and apparatus for generating high power laser pulses in the two to six micron wavelength range

    DOEpatents

    MacPherson, D.C.; Nelson, L.D.; O`Brien, M.J.

    1996-12-10

    Apparatus performs a method of generating one or more output laser pulses in a range of 2 to 6 microns. When a plurality of the output laser pulses are generated, a first output pulse has any selected wavelength within the range and a second output pulse is temporally closely spaced relative to the first output pulse and has a chosen wavelength differing from the selected wavelength. An oscillator laser cavity is provided with a tunable oscillator rod capable of generating initial laser pulses within a range of from 750 to 1000 nm, and a tuning element is coupled to the rod. A flashlamp is operable to pump the rod. For two pulse operation, the flashlamp has a given duration. A Q-switch provides the initial laser pulses upon operation of the tuning element and the flashlamp. A Raman device coupled to the rod shifts the wavelength of such initial laser pulse into the range of from 2 to 6 microns to form the output laser pulse having a wavelength within the range. For multiple pulses, a controller causes the Q-switch to provide first and second ones of the initial laser pulses, spaced by a time interval less than the given duration. Also, a selector coupled to the tuning element is operable within such duration to successively select the wavelength of the first output pulse and the chosen wavelength of the second initial pulse. The Raman device is responsive to each of the initial light pulses to generate radiation at first and second Stokes wavelengths, each of said the output laser pulses being radiation at the second Stokes wavelength. 30 figs.

  7. The optical absorption of triatomic carbon C3 for the wavelength range 260 to 560 nm

    NASA Technical Reports Server (NTRS)

    Jones, J. J.

    1978-01-01

    The spectral absorption properties of C3 have been measured in a shock tube containing a test gas mixture of acetylene diluted with argon. The absorption of a pulsed xenon light source was measured by means of eight photomultiplier channels to a spectrograph and an accompanying drum camera. The postshock test gas temperature and pressure were varied over the range 3240 to 4300 K and 37 to 229 kPa, respectively. The results showed appreciable absorption by C3 for the wavelength range 300 to 540 nm. The various reported measurements of the heat of formation of C3 which are available in the open literature were reviewed, and a value of 198 kcal/mol is recommended. This value, along with best available values for other species, was used to calculate the number density of C3 for the conditions of the present experiments in order to compute absorption cross section or electronic oscillator strength. The computed electronic oscillator strength varied from a high of 0.062 at 3300 K to a low of 0.036 at 3900 K.

  8. Increment of Access Points in Integrated System of Wavelength Division Multiplexed Passive Optical Network Radio over Fiber

    PubMed Central

    Amiri, I. S.; Alavi, S. E.; Soltanian, M. R. K.; Fisal, N.; Supa’at, A. S. M.; Ahmad, H.

    2015-01-01

    This paper describes a novel technique to increase the numbers of access points (APs) in a wavelength division multiplexed-passive optical network (WDM-PON) integrated in a 100 GHz radio-over-fiber (RoF). Eight multi-carriers separated by 25 GHz intervals were generated in the range of 193.025 to 193.200 THz using a microring resonator (MRR) system incorporating an add-drop filter system. All optically generated multi-carriers were utilized in an integrated system of WDM-PON-RoF for transmission of four 43.6 Gb/sec orthogonal frequency division multiplexing (OFDM) signals. Results showed that an acceptable BER variation for different path lengths up to 25 km was achievable for all four access points and thus the transmission of four OFDM channels is feasible for a 25 km standard single mode fiber (SSMF) path length. PMID:26153536

  9. Satellite laser ranging using superconducting nanowire single-photon detectors at 1064  nm wavelength.

    PubMed

    Xue, Li; Li, Zhulian; Zhang, Labao; Zhai, Dongsheng; Li, Yuqiang; Zhang, Sen; Li, Ming; Kang, Lin; Chen, Jian; Wu, Peiheng; Xiong, Yaoheng

    2016-08-15

    Satellite laser ranging operating at 1064 nm wavelength using superconducting nanowire single-photon detectors (SNSPDs) is successfully demonstrated. A SNSPD with an intrinsic quantum efficiency of 80% and a dark count rate of 100 cps at 1064 nm wavelength is developed and introduced to Yunnan Observatory in China. With improved closed-loop telescope systems (field of view of about 26''), satellites including Cryosat, Ajisai, and Glonass with ranges of 1600 km, 3100 km, and 19,500 km, respectively, are experimentally ranged with mean echo rates of 1200/min, 4200/min, and 320/min, respectively. To the best of our knowledge, this is the first demonstration of laser ranging for satellites using SNSPDs at 1064 nm wavelength. Theoretical analysis of the detection efficiency and the mean echo rate for typical satellites indicate that it is possible for a SNSPD to range satellites from low Earth orbit to geostationary Earth orbit. PMID:27519105

  10. Spectral irradiance model for tungsten halogen lamps in 340-850 nm wavelength range.

    PubMed

    Ojanen, Maija; Kärhä, Petri; Ikonen, Erkki

    2010-02-10

    We have developed a physical model for the spectral irradiance of 1 kW tungsten halogen incandescent lamps for the wavelength range 340-850 nm. The model consists of the Planck's radiation law, published values for the emissivity of tungsten, and a residual spectral correction function taking into account unknown factors of the lamp. The correction function was determined by measuring the spectra of a 1000 W, quartz-halogen, tungsten coiled filament (FEL) lamp at different temperatures. The new model was tested with lamps of types FEL and 1000 W, 120 V quartz halogen (DXW). Comparisons with measurements of two national standards laboratories indicate that the model can account for the spectral irradiance values of lamps with an agreement better than 1% throughout the spectral region studied. We further demonstrate that the spectral irradiance of a lamp can be predicted with an expanded uncertainty of 2.6% if the color temperature and illuminance values for the lamp are known with expanded uncertainties of 20 K and 2%, respectively. In addition, it is suggested that the spectral irradiance may be derived from resistance measurements of the filament with lamp on and off.

  11. Detection of wavelengths in the visible range using fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Díaz, Leonardo; Morales, Yailteh; Mattos, Lorenzo; Torres, Cesar O.

    2013-11-01

    This paper shows the design and implementation of a fiber optic sensor for detecting and identifying wavelengths in the visible range. The system consists of a diffuse optical fiber, a conventional laser diode 650nm, 2.5mW of power, an ambient light sensor LX1972, a PIC 18F2550 and LCD screen for viewing. The principle used in the detection of the lambda is based on specular reflection and absorption. The optoelectronic device designed and built used the absorption and reflection properties of the material under study, having as active optical medium a bifurcated optical fiber, which is optically coupled to an ambient light sensor, which makes the conversion of light signals to electricas, procedure performed by a microcontroller, which acquires and processes the signal. To verify correct operation of the assembly were utilized the color cards of sewing thread and nail polish as samples for analysis. This optoelectronic device can be used in many applications such as quality control of industrial processes, classification of corks or bottle caps, color quality of textiles, sugar solutions, polymers and food among others.

  12. Electro-optical SLS devices for operating at new wavelength ranges

    DOEpatents

    Osbourn, Gordon C.

    1986-01-01

    An intrinsic semiconductor electro-optical device includes a p-n junction intrinsically responsive, when cooled, to electromagnetic radiation in the wavelength range of 8-12 um. The junction consists of a strained-layer superlattice of alternating layers of two different III-V semiconductors having mismatched lattice constants when in bulk form. A first set of layers is either InAs.sub.1-x Sb.sub.x (where x is aobut 0.5 to 0.7) or In.sub.1-x Ga.sub.x As.sub.1-y Sb.sub.y (where x and y are chosen such that the bulk bandgap of the resulting layer is about the same as the minimum bandgap in the In.sub.1-x Ga.sub.x As.sub.1-y Sb.sub.y family). The second set of layers has a lattice constant larger than the lattice constant of the layers in the first set.

  13. Novel Ultra-Sensitive Detectors in the 10–50 μm Wavelength Range

    PubMed Central

    Ueda, Takeji; Komiyama, Susumu

    2010-01-01

    We have developed novel single-photon detectors in the 10–50 μm wavelength region. The detectors are charge-sensitive infrared phototransistors (CSIPs) fabricated in GaAs/AlGaAs double quantum well (QW) structures, in which a photo-generated hole (+e) in the floating gate (upper QW) modulates the conductance of a capacitively-coupled channel located underneath (lower QW). The excellent noise equivalent power (NEP = 8.3 × 10−19 W/Hz1/2) and specific detectivity (D* = 8 × 1014 cm Hz1/2/W) are demonstrated for 15 micron detection up to 23 K, which are by a few orders of magnitude better than those of other state-of-the-art high-sensitivity detectors. The dynamic range exceeds 106 (∼aW to pW) by repeatedly resetting the accumulated holes in the upper QW. Simple device structure makes the detectors feasible for array fabrication: Furthermore, monolithic integration with reading circuits will be possible. PMID:22163662

  14. Spectral irradiance model for tungsten halogen lamps in 340-850 nm wavelength range

    SciTech Connect

    Ojanen, Maija; Kaerhae, Petri; Ikonen, Erkki

    2010-02-10

    We have developed a physical model for the spectral irradiance of 1 kW tungsten halogen incandescent lamps for the wavelength range 340-850 nm. The model consists of the Planck's radiation law, published values for the emissivity of tungsten, and a residual spectral correction function taking into account unknown factors of the lamp. The correction function was determined by measuring the spectra of a 1000 W, quartz-halogen, tungsten coiled filament (FEL) lamp at different temperatures. The new model was tested with lamps of types FEL and 1000 W, 120 V quartz halogen (DXW). Comparisons with measurements of two national standards laboratories indicate that the model can account for the spectral irradiance values of lamps with an agreement better than 1% throughout the spectral region studied. We further demonstrate that the spectral irradiance of a lamp can be predicted with an expanded uncertainty of 2.6% if the color temperature and illuminance values for the lamp are known with expanded uncertainties of 20 K and 2%, respectively. In addition, it is suggested that the spectral irradiance may be derived from resistance measurements of the filament with lamp on and off.

  15. Refractivities of H2, He, O2, CO, and Kr for 168-288 nm wavelength range

    NASA Technical Reports Server (NTRS)

    Smith, P. L.; Parkinson, W. H.; Huber, M. C. E.

    1976-01-01

    Precision measurements of the refractivities of H2, He, O2, CO, and Kr were made in the wavelength range 168-288 nm. By using a 1.2-m-long test cell and by keeping the test gas at accurately determined conditions near atmospheric pressure and room temperature, accuracies (90% confidence limit) were achieved for the absolute refractivities that ranged from plus or minus 0.1% to plus or minus 1.0% depending upon the gas and wavelength range. For a given gas, the ratio of refractivities at any two wavelengths has a smaller uncertainty. For H2, CO, and O2, results are for wavelengths shorter than those of previous measurements and, for He and Kr, the uncertainties are less than those of other measurements. For He refractivities agree with the theoretical ones, but in the case of H2 results are about 1% larger than the theoretical values. At the upper end of the wavelength range studied, the data are in agreement with previous measurements on H2, CO, and Kr. For O2 results indicate that the hitherto available data are too large by amounts ranging from 0.8% to 10%.

  16. Apparatus And Methods For Launching And Receiving A Broad Wavelength Range Source

    DOEpatents

    Von Drasek, William A.; Sonnenfroh, David; Allen, Mark G.; Stafford-Evans, Joy

    2006-02-28

    An apparatus and method for simultaneous detection of N gas species through laser radiation attenuation techniques is disclosed. Each of the N species has a spectral absorption band. N laser sources operate at a wavelength ?N in a spectral absorption band separated by the cutoff wavelength for single-mode transmission. Each laser source corresponds to a gas species and transmits radiation through an optical fiber constructed and arranged to provide single-mode transmission with minimal power loss.

  17. Science cases, wavelength ranges, and strategies for ELTs: some remarks and conclusions

    NASA Astrophysics Data System (ADS)

    Gustafsson, Bengt

    2008-04-01

    Discussions at the Symposium ELTs: Which wavelengths? in Lund in December 2007 are summarized and in particular comments are made on the relation between the optimization of the presently planned ELTs, and their corresponding background science cases. The division of labour between the ELTs and the JWST is commented on. The need for an ELT (and/or a future Space Telescope) for the optical wavelength region is stressed. Possible strategies for pursuing the ELT projects are commented on.

  18. Fluorescence imaging of viscous materials in the ultraviolet-visible wavelength range.

    PubMed

    Murr, Patrik J; Rauscher, Markus S; Tremmel, Anton; Schardt, Michael; Koch, Alexander W

    2014-08-01

    This paper presents an approach of an innovative measurement principle for the quality control of viscous materials during a manufacturing process based on fluorescence imaging. The main contribution to the state of the art provided by this measurement system is that three equal fluorescence images of a static or moving viscous object are available in different optical paths. The independent images are obtained by two beam splitters which are connected in series. Based on these images, it is possible to evaluate each image separately. In our case, three optical bandpass filters with different center wavelengths of 405 nm, 420 nm, and 440 nm were used to filter the separate fluorescence images. The developed system is useable for the detection of impurities in the micrometer range. Further, incorrect mixing ratios of particular components and wrong single components in the viscous materials can be detected with the setup. Moreover, it is possible to realize static and dynamic measurements. In this case the maximum speed of the objects was 0.2 m/s for the dynamic measurements. Advantages of this measurement setup are the universality due to the use of optical standard components, the small dimension and the opportunity to integrate it easily into ongoing processes. In addition, the measurement system works on a non-contact basis. Thus, the expense for maintenance is at a very low level compared to currently available measurement setups for the investigated application. Furthermore, the setup provides for the first time a simultaneous analysis of more than one component and the detection of impurities concerning their nature and size in a manufacturing process. PMID:25173316

  19. Fluorescence imaging of viscous materials in the ultraviolet-visible wavelength range

    SciTech Connect

    Murr, Patrik J. Rauscher, Markus S.; Tremmel, Anton; Schardt, Michael; Koch, Alexander W.

    2014-08-15

    This paper presents an approach of an innovative measurement principle for the quality control of viscous materials during a manufacturing process based on fluorescence imaging. The main contribution to the state of the art provided by this measurement system is that three equal fluorescence images of a static or moving viscous object are available in different optical paths. The independent images are obtained by two beam splitters which are connected in series. Based on these images, it is possible to evaluate each image separately. In our case, three optical bandpass filters with different center wavelengths of 405 nm, 420 nm, and 440 nm were used to filter the separate fluorescence images. The developed system is useable for the detection of impurities in the micrometer range. Further, incorrect mixing ratios of particular components and wrong single components in the viscous materials can be detected with the setup. Moreover, it is possible to realize static and dynamic measurements. In this case the maximum speed of the objects was 0.2 m/s for the dynamic measurements. Advantages of this measurement setup are the universality due to the use of optical standard components, the small dimension and the opportunity to integrate it easily into ongoing processes. In addition, the measurement system works on a non-contact basis. Thus, the expense for maintenance is at a very low level compared to currently available measurement setups for the investigated application. Furthermore, the setup provides for the first time a simultaneous analysis of more than one component and the detection of impurities concerning their nature and size in a manufacturing process.

  20. Fluorescence imaging of viscous materials in the ultraviolet-visible wavelength range

    NASA Astrophysics Data System (ADS)

    Murr, Patrik J.; Rauscher, Markus S.; Tremmel, Anton; Schardt, Michael; Koch, Alexander W.

    2014-08-01

    This paper presents an approach of an innovative measurement principle for the quality control of viscous materials during a manufacturing process based on fluorescence imaging. The main contribution to the state of the art provided by this measurement system is that three equal fluorescence images of a static or moving viscous object are available in different optical paths. The independent images are obtained by two beam splitters which are connected in series. Based on these images, it is possible to evaluate each image separately. In our case, three optical bandpass filters with different center wavelengths of 405 nm, 420 nm, and 440 nm were used to filter the separate fluorescence images. The developed system is useable for the detection of impurities in the micrometer range. Further, incorrect mixing ratios of particular components and wrong single components in the viscous materials can be detected with the setup. Moreover, it is possible to realize static and dynamic measurements. In this case the maximum speed of the objects was 0.2 m/s for the dynamic measurements. Advantages of this measurement setup are the universality due to the use of optical standard components, the small dimension and the opportunity to integrate it easily into ongoing processes. In addition, the measurement system works on a non-contact basis. Thus, the expense for maintenance is at a very low level compared to currently available measurement setups for the investigated application. Furthermore, the setup provides for the first time a simultaneous analysis of more than one component and the detection of impurities concerning their nature and size in a manufacturing process.

  1. Selective excavation of human carious dentin using the nanosecond pulsed laser in 5.8-μm wavelength range

    NASA Astrophysics Data System (ADS)

    Kita, Tetsuya; Ishii, Katsunori; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    Less-invasive treatment of caries has been needed in laser dentistry. Based on the absorption property of dentin substrates, 6 μm wavelength range shows specific absorptions and promising characteristics for the excavation. In our previous study, 5.8 μm wavelength range was found to be effective for selective excavation of carious dentin and restoration treatment using composite resin from the irradiation experiment with bovine sound and demineralized dentin. In this study, the availability of 5.8 μm wavelength range for selective excavation of human carious dentin was investigated for clinical application. A mid-infrared tunable nanosecond pulsed laser by difference-frequency generation was used for revealing the ablation property of human carious dentin. Irradiation experiments indicated that the wavelength of 5.85 μm and the average power density of 30 W/cm2 realized the selective excavation of human carious dentin, but ablation property was different with respect to each sample because of the different caries progression. In conclusion, 5.8 μm wavelength range was found to be effective for selective excavation of human carious dentin.

  2. Four-wavelength time-resolved optical mammography in the 680-980-nm range

    NASA Astrophysics Data System (ADS)

    Pifferi, Antonio; Taroni, Paola; Torricelli, Alessandro; Messina, Fabrizio; Cubeddu, Rinaldo; Danesini, Gianmaria

    2003-07-01

    What is to our knowledge the first instrument for time-resolved optical mammography operating at wavelengths longer than 900 nm has been developed. It is a scanning system that relies on the acquisition of time-resolved transmittance curves at 683, 785, 912, and 975 nm, with a total measurement time of ~5 min for an entire image. Breast structures and lesions can be discriminated based on the different absorption and scattering properties at the four wavelengths, which reflect different contributions of oxyhemoglobin, deoxyhemoglobin, water, and lipids, as well as distinct structures. The system is currently used in a European clinical trial.

  3. High-accuracy reference standards for two-photon absorption in the 680-1050 nm wavelength range.

    PubMed

    de Reguardati, Sophie; Pahapill, Juri; Mikhailov, Alexander; Stepanenko, Yuriy; Rebane, Aleksander

    2016-04-18

    Degenerate two-photon absorption (2PA) of a series of organic fluorophores is measured using femtosecond fluorescence excitation method in the wavelength range, λ2PA = 680-1050 nm, and ~100 MHz pulse repetition rate. The function of relative 2PA spectral shape is obtained with estimated accuracy 5%, and the absolute 2PA cross section is measured at selected wavelengths with the accuracy 8%. Significant improvement of the accuracy is achieved by means of rigorous evaluation of the quadratic dependence of the fluorescence signal on the incident photon flux in the whole wavelength range, by comparing results obtained from two independent experiments, as well as due to meticulous evaluation of critical experimental parameters, including the excitation spatial- and temporal pulse shape, laser power and sample geometry. Application of the reference standards in nonlinear transmittance measurements is discussed.

  4. Attenuation on an Earth-space path measured in the wavelength range of 8 to 14 micrometers.

    PubMed

    Wilson, R W

    1970-06-19

    A telescope operating over the wavelength range of 8 to 14 micrometers has been added to the Crawford Hill sun tracker for the purpose of measuring attenuation in that atmospheric window. Over a 9-month period the attenuation (typically from clouds) exceeded 10, 20, and 30 decibels for 48, 43, and 34 percent of the time.

  5. Linear absorption coefficient of beryllium in the 50-300-A wavelength range. [bandpass filter materials for ultraviolet astronomy instrumentation

    NASA Technical Reports Server (NTRS)

    Barstow, M. A.; Lewis, M.; Petre, R.

    1983-01-01

    Transmittances of thin-film filters fabricated for an extreme-UV astronomy sounding-rocket experiment yield values for the linear absorption coefficient of beryllium in the 50-300-A wavelength range, in which previous measurements are sparse. The inferred values are consistent with the lowest data previously published and may have important consequences for extreme-UV astronomers.

  6. 21-nm-range wavelength-tunable L-band Er-doped fiber linear-cavity laser

    NASA Astrophysics Data System (ADS)

    Yang, Shiquan; Zhao, Chunliu; Li, Zhaohui; Ding, Lei; Yuan, Shuzhong; Dong, Xiaoyi

    2001-10-01

    A novel method, which utilizes amplified spontaneous emission (ASE) as a secondary pump source, is presented for implanting a linear cavity erbium-doped fiber laser operating in L-Band. The output wavelength tuned from 1566 nm to 1587 nm, about 21 nm tuning range, was obtained in the experiment and the stability of the laser is very good.

  7. Laboratory Measurements Of Pure And Diluted Methanol In Water Ice In The Nir And Mir Wavelength Ranges.

    NASA Astrophysics Data System (ADS)

    Merlin, Frederic; Quirico, E.; Barucci, M. A.; Gourgeot, F.

    2012-10-01

    Observations performed in the mid infrared (MIR) show evidence of large amount of ices in the Galaxy. Water ice is the most abundant but other chemical compounds, such as carbon monoxide and methanol, can be present and be enriched in molecular clouds or protostellar disks (Garrod & Pauly 2011). Methanol forms mainly on ice-covered dust grain surfaces primarily through hydrogenation of CO or from an electron-irradiated H2O-CH4 icy mixture (see Moore & Hudson 1998 or Dartois et al. 1999). These compounds appear to be pristine in the minor bodies of the solar system (Merlin et al. 2012) and were found in comets (Bockelée-Morvan et al. 2004) and on the surface of Trans-Neptunian Objects and Centaurs (Barucci et al. 2012 for instance for methanol). Laboratory measurements are needed to constrain information on the physical and chemical properties of these objects and give constraint on the formation and evolution of the solar system. In the aim to give constraints on the physical properties of H2O and CH3OH from their spectral behavior, we performed laboratory measurements in the observable wavelength ranges accessible from the space and ground based observatories (in the MIR and in the near IR, respectively). We present new laboratory measurements depending on the ratio of each component and the ambient temperature (from 18 to 145K) for the amorphous and the crystalline phases. We focus our analyses on the effects of the dilution level of CH3OH in H2O and the phase changes, especially on the absorption bands located at 2,3 and 3,45 microns (associated to CH asymmetric stretch) and the possible formation of the mono hydrate CH3OH:H2O based on the 3,12 micron band (associated to the OH stretch).

  8. Broadband carbon monoxide laser system operating in the wavelength range of 2.5 - 8.3 {mu}m

    SciTech Connect

    Andreev, Yu M; Ionin, Andrei A; Kinyaevsky, I O; Klimachev, Yu M; Kozlov, A Yu; Kotkov, A A; Lanskii, G V; Shaiduko, A V

    2013-02-28

    A two-cascade frequency conversion of CO-laser radiation is demonstrated in a single sample of a nonlinear ZnGeP{sub 2} crystal. The crystal is pumped by a repetitively pulsed cryogenic lowpressure CO laser operating on {approx}150 vibration - rotational transitions in the wavelength range 5.0 - 7.5 {mu}m, which corresponds to the frequency range of a half octave. In the first conversion cascade, generation of second harmonic and sum frequencies of various pairs of CO-laser radiation give {approx}350 emission lines in the wavelength range 2.5 - 3.7 {mu}m. In the second cascade, by mixing the radiation converted in the first cascade with the residual radiation of the CO laser we have obtained {approx}90 lines in the range 4.3 - 5.0 {mu}m and more than 80 lines in the range 7.5 - 8.3 {mu}m. Thus, using a single sample of the nonlinear ZnGeP{sub 2} crystal pumped by the radiation of a single CO laser we have produced a source of broadband (more than one and a half octaves) laser radiation, simultaneously operating at {approx}670 lines in the wavelength range 2.5 - 8.3 {mu}m. (lasers)

  9. Model of optical nonlinearity of air in the mid-IR wavelength range

    SciTech Connect

    Geints, Yu E; Zemlyanov, A A

    2014-09-30

    A model of optical nonlinearity of air (atmospheric nitrogen and oxygen) is developed. This model can be used to calculate numerically the propagation of radiation with a wavelength close to 10 μm. It takes into account the electronic Kerr effect, higher order nonlinearities, ionisation of a gas medium by electron impact, and pulse group-velocity dispersion. The applicability limits of the Drude approximation for calculating the impact-ionisation rate are also considered. (nonlinear optical phenomena)

  10. Coherent supercontinuum generation in a silicon photonic wire in the telecommunication wavelength range.

    PubMed

    Leo, François; Gorza, Simon-Pierre; Coen, Stéphane; Kuyken, Bart; Roelkens, Gunther

    2015-01-01

    We demonstrate a fully coherent supercontinuum spectrum spanning 500 nm from a silicon-on-insulator photonic wire waveguide pumped at 1575 nm wavelength. An excellent agreement with numerical simulations is reported. The simulations also show that a high level of two-photon absorption can essentially enforce the coherence of the spectral broadening process irrespective of the pump pulse duration.

  11. A Scalable Long-Reach Wavelength-Division Multiplexing Access Network Sharing Both Fiber Protection and Broadcasting Services

    NASA Astrophysics Data System (ADS)

    Feng, Chen; Gan, Chaoqin; Gao, Ziyue; Guo, Su; Li, Wei; Fang, Yiqin

    2014-07-01

    A novel scalable wavelength-division multiplexing access network is proposed in this article. By newly designing the remote node, this network can not only support the long-reach transmission and broadcasting services, it can also have flexible scalability and the ability of sharing fiber protection. These make this network have great resilient capability. Also, this scheme still has the characteristic of Rayleigh backscattering mitigation and shared-seeding light of upstream signals. The simulation results indicate this network has good performance.

  12. Direct method of three-dimensional imaging using the multiple-wavelength range-gated active imaging principle.

    PubMed

    Matwyschuk, Alexis

    2016-05-10

    The tomography executed with mono-wavelength active imaging systems uses the recording of several images to restore a three-dimensional (3D) scene. Thus, in order to show the depth in the scene, a different color is attributed to each recorded image. Therefore, the 3D restoration depends on the video frame rate of the camera. By using a multiple-wavelength range-gated active imaging system, it is possible to restore the 3D scene directly in a single image at the moment of recording with a video camera. Each emitted light pulse with a different wavelength corresponds to a visualized zone at a different distance in the scene. The camera shutter opens just once during the emission of light pulses with the different wavelengths. Thus, the restoration can be executed in real time with regard to the video frame rate of the camera. From an analytical model and from a graphical approach, we demonstrated the feasibility of this new method of 3D restoration. The non-overlapping conditions between two consecutive visualized zones are analyzed. The experimental test results confirm these different conditions and validate the theoretical principle to directly restore the 3D scene in a color image with a multiple-wavelength laser source, an RGB filter, and a triggerable intensified camera. PMID:27168293

  13. Diffractive optical elements with an increased angular and wavelength range of operation for application in solar collectors

    NASA Astrophysics Data System (ADS)

    Akbari, H.; Naydenova, I.; Martin, S.

    2015-05-01

    A holographic device characterised by a large angular and wavelength range of operation is under development. It aims to improve the efficiency of solar energy concentration in solar cells. The aim of this study is to increase the angular and wavelength range of the gratings by stacking three layers of high efficiency gratings on top of each other so that light from a moving source, such as the sun, is collected from a broad range of angles. In order to increase the angle and the wavelength range of operation of the holographic device, low spatial frequency of holographic recording is preferable. Recording at low spatial frequency requires a photopolymer material with unique properties, such as fast monomer/monomers diffusion rate/rates. An acrylamide-based photopolymer developed at the Centre for Industrial and Engineering Optics has been used in this study. This material has fast diffusion rates and has previously demonstrated very good performance at low spatial frequency, where gratings of 90% diffraction efficiency at 300 lines/ mm spatial frequency were recorded in layers of 75 μm thickness. This paper will study the angular selectivity of a device consisting of stacked layer of Difftactive Optical Elements ( DOEs) recorded at range of angles at spatial frequency of 300 lines/mm with recording intensity of 1 mW/cm2. The optical recording process and the properties of the multilayer structure are described and discussed.

  14. Controlling the red boundary of the tunneling photoeffect in nanodimensional carbon structures in a broad (UV-IR) wavelength range

    NASA Astrophysics Data System (ADS)

    Akchurin, G. G.; Yakunin, A. N.; Aban'shin, N. P.; Gorfinkel', B. I.; Akchurin, G. G.

    2013-06-01

    The tunneling photoeffect (PE) has been studied in a microdiode with an electrostatic field localized at an emitter based on a nanodimensional carbon structure. It is established that, when the carbon nanoemitter is exposed to laser and LED radiation photons of low energy (below work function) in the spectral range from near-UV (380 nm) to near-IR (1150 nm) at micro- and milliwatt optical power, a tunneling photocurrent can be initiated by controlling the electric field strength in the emitter-anode gap. The observed phenomenon can be adequately interpreted using a modified Fowler-Nordheim equation for non-equilibrium photoelectrons. Specific features of the construction and operation of photodetectors based on the tunneling PE with a controlled long-wavelength threshold (red boundary) of photoelectron emission are considered. The bandwidth of photoelectron emitters is evaluated, and the possibility of their operation in the wavelength range from UV up to far-IR is predicted.

  15. 45 nm wavelength tuning range of an InP/InGaAsP photonic integrated tunable receiver

    NASA Astrophysics Data System (ADS)

    Jan, Yu-Heng; Heimbuch, Mark E.; Coldren, Larry A.; DenBaars, Steven P.

    1996-11-01

    An integrated widely tunable photonic receiver including a semiconductor optical preamplifier, a two-section grating-assisted co-directional coupler optical filter, and a waveguide photodetector has been produced in the InP/InGaAsP materials system. Although sidelobes and bandwidth are still higher than desired, this integrated receiver can be continuously tuned for a record-wide 45 nm wavelength range.

  16. Spectrophotometry of Jupiter in the Wavelength Range 320-1100 nm: Long-Term Observations of Variations over the Disk

    NASA Astrophysics Data System (ADS)

    Vdovichenko, V. D.; Kirienko, G. A.; Nosova, T. P.

    2003-07-01

    Based on long-term spectrophotometric observations of Jupiter in the wavelength range 320-1100 nm, we investigate the variations of aerosol extinction (at λ 320-600 nm) and methane-ammonia absorption (at λ 600-1100 nm) over Jupiter's disk. We give estimates of the optical parameters for the upper cloud layer of the planet, the overlying stratospheric haze, and a Rayleigh atmosphere.

  17. Blue light stress in retinal neuronal (R28) cells is dependent on wavelength range and irradiance.

    PubMed

    Knels, Lilla; Valtink, Monika; Roehlecke, Cora; Lupp, Amelie; de la Vega, Jamlec; Mehner, Mirko; Funk, Richard H W

    2011-08-01

    The aim of our study was to elucidate the role of wavelength and irradiance in blue light retinal damage. We investigated the impact of blue light emitted from light-emitting diode (LED) modules with peaks at either 411nm (half bandwidth 17nm) or 470nm (half bandwidth 25nm) at defined irradiances of 0.6, 1.5 and 4.5W/m(2) for 411nm and 4.5W/m(2) for 470nm on retinal neuronal (R28) cells in vitro. We observed a reduction in metabolic activity and transmembrane potential of mitochondria when cells were irradiated at 411nm at higher irradiances. Furthermore, production of mitochondrial superoxide radicals increased significantly when cells were irradiated with 411nm light at 4.5W/m(2) . In addition, such irradiation caused an activation of the antioxidative glutathion system. Using vital staining, flow cytometry and western blotting, we were able to show that apoptosis only took place when cells were exposed to 411nm blue light at higher irradiances; necrosis was not observed. Enhanced caspase-3 cleavage product levels confirmed that this effect was dependent on light irradiance. Significant alterations of the above-mentioned parameters were not observed when cells were irradiated with 471nm light despite a high irradiance of 4.5W/m(2) , indicating that the cytotoxic effect of blue light is highly dependent on wavelength. The observed phenomena in R28 cells at 411nm (4.5W/m(2) ) point to an apoptosis pathway elicited by direct mitochondrial damage and increased oxidative stress. Thus, light of 411nm should act via impairment of mitochondrial function by compromising the metabolic situation of these retinal neuronal cells.

  18. Stellar science from a blue wavelength range. A possible design for the blue arm of 4MOST

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Ludwig, H.-G.; Seifert, W.; Koch, A.; Xu, W.; Caffau, E.; Christlieb, N.; Korn, A. J.; Lind, K.; Sbordone, L.; Ruchti, G.; Feltzing, S.; de Jong, R. S.; Barden, S.

    2015-09-01

    From stellar spectra, a variety of physical properties of stars can be derived. In particular, the chemical composition of stellar atmospheres can be inferred from absorption line analyses. These provide key information on large scales, such as the formation of our Galaxy, down to the small-scale nucleosynthesis processes that take place in stars and supernovae. By extending the observed wavelength range toward bluer wavelengths, we optimize such studies to also include critical absorption lines in metal-poor stars, and allow for studies of heavy elements (Z\\ensuremath{g}e 38) whose formation processes remain poorly constrained. In this context, spectrographs optimized for observing blue wavelength ranges are essential, since many absorption lines at redder wavelengths are too weak to be detected in metal-poor stars. This means that some elements cannot be studied in the visual-redder regions, and important scientific tracers and science cases are lost. The present era of large public surveys will target millions of stars. It is therefore important that the next generation of spectrographs are designed such that they cover a wide wavelength range and can observe a large number of stars simultaneously. Only then, we can gain the full information from stellar spectra, from both metal-poor to metal-rich ones, that will allow us to understand the aforementioned formation scenarios in greater detail. Here we describe the requirements driving the design of the forthcoming survey instrument 4MOST, a multi-object spectrograph commissioned for the ESO VISTA 4 m-telescope. While 4MOST is also intended for studies of active galactic nuclei, baryonic acoustic oscillations, weak lensing, cosmological constants, supernovae and other transients, we focus here on high-density, wide-area survey of stars and the science that can be achieved with high-resolution stellar spectroscopy. Scientific and technical requirements that governed the design are described along with a thorough

  19. Vertically integrated (Ga, In)N nanostructures for future single photon emitters operating in the telecommunication wavelength range

    NASA Astrophysics Data System (ADS)

    Winden, A.; Mikulics, M.; Grützmacher, D.; Hardtdegen, H.

    2013-10-01

    Important technological steps are discussed and realized for future room-temperature operation of III-nitride single photon emitters. First, the growth technology of positioned single pyramidal InN nanostructures capped by Mg-doped GaN is presented. The optimization of their optical characteristics towards narrowband emission in the telecommunication wavelength range is demonstrated. In addition, a device concept and technology was developed so that the nanostructures became singularly addressable. It was found that the nanopyramids emit in the telecommunication wavelength range if their size is chosen appropriately. A p-GaN contacting layer was successfully produced as a cap to the InN pyramids and the top p-contact was achievable using an intrinsically conductive polymer PEDOT:PSS, allowing a 25% increase in light transmittance compared to standard Ni/Au contact technology. Single nanopyramids were successfully integrated into a high-frequency device layout. These decisive technology steps provide a promising route to electrically driven and room-temperature operating InN based single photon emitters in the telecommunication wavelength range.

  20. Vertically integrated (Ga, In)N nanostructures for future single photon emitters operating in the telecommunication wavelength range.

    PubMed

    Winden, A; Mikulics, M; Grützmacher, D; Hardtdegen, H

    2013-10-11

    Important technological steps are discussed and realized for future room-temperature operation of III-nitride single photon emitters. First, the growth technology of positioned single pyramidal InN nanostructures capped by Mg-doped GaN is presented. The optimization of their optical characteristics towards narrowband emission in the telecommunication wavelength range is demonstrated. In addition, a device concept and technology was developed so that the nanostructures became singularly addressable. It was found that the nanopyramids emit in the telecommunication wavelength range if their size is chosen appropriately. A p-GaN contacting layer was successfully produced as a cap to the InN pyramids and the top p-contact was achievable using an intrinsically conductive polymer PEDOT:PSS, allowing a 25% increase in light transmittance compared to standard Ni/Au contact technology. Single nanopyramids were successfully integrated into a high-frequency device layout. These decisive technology steps provide a promising route to electrically driven and room-temperature operating InN based single photon emitters in the telecommunication wavelength range.

  1. Influence of the absorption behavior of sunscreens in the short-wavelength UV range (UVB) and the long-wavelength UV range (UVA) on the relation of the UVB absorption to sun protection factor

    NASA Astrophysics Data System (ADS)

    Weigmann, Hans-Juergen; Schanzer, Sabine; Antoniou, Christina; Sterry, Wolfram; Lademann, Juergen

    2010-09-01

    The absorption of filter substances in sunscreens, reducing the incident ultraviolet (UV) radiation, is the basis for the protecting ability of such formulations. The erythema-correlated sun protection factor (SPF), depending mainly on the intensity of the UVB radiation, is the common value to quantify the efficacy of the formulations avoiding sunburn. An ex vivo method combining tape stripping and optical spectroscopy is applied to measure the absorption of sunscreens in the entire UV spectral range. The obtained relations between the short-wavelength UV (UVB) absorption and the SPF confirm a clear influence of the long-wavelength UV (UVA) absorption on the SPF values. The data reflect the historical development of the relation of the concentration of UVB and UVA filters in sunscreens and points to the influence of additional ingredients, e.g., antioxidants and cell-protecting agents on the efficacy of the products.

  2. High-power diode lasers for the 1.9 to 2.2 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Kelemen, Márc T.; Gilly, Jürgen; Moritz, Rudolf; Rattunde, Marcel; Schmitz, Johannes; Wagner, Joachim

    2008-02-01

    GaSb based diode laser both as single emitters and as arrays, emitting between 1.9 and 2.2 μm, have a huge potential especially for materials processing, medical applications and as optical pump sources for solid state laser systems emitting in the 2-4 μm wavelength range. Determined by the absorption characteristics of thermoplastic materials at wavelengths around 2 μm, the light emitted by the diode laser will be absorbed by the material itself and can thus be used for marking and welding without the addition of e.g. colour pigments. We will present results on different (AlGaIn)(AsSb) quantum-well diode laser single emitters and linear laser arrays, the latter consisting of 20 emitters on a 1 cm long bar, emitting at different wavelengths between 1.9 and 2.2 μm. To improve on the typically poor fast axis beam divergence of diode lasers emitting at these wavelengths, we abandoned the broadened waveguide concept and changed over to a new waveguide design which features a rather narrow waveguide core. This results in a remarkable reduction in fast axis beam divergence to 43° FWHM for the new waveguide design. Electro-optical and thermal behaviour and the wavelength tunability by current and temperature have been carefully investigated in detail. For single emitters cw output powers of 2 W have been demonstrated. For diode laser arrays mounted on actively cooled heat sinks, more than 20 W in continuous-wave mode have been achieved at a heat sink temperature of 20 °C resulting in wall-plug efficiencies of more than 26%.

  3. Centerless circular array method: Inferring phase velocities of Rayleigh waves in broad wavelength ranges using microtremor records

    NASA Astrophysics Data System (ADS)

    Cho, Ikuo; Tada, Taku; Shinozaki, Yuzo

    2006-09-01

    The centerless circular array (CCA) method, proposed by ourselves in an earlier work, is an algorithm of microtremor exploration which can be used to estimate phase velocities of Rayleigh waves by analyzing vertical component records of microtremors that are obtained with an array of three or five seismic sensors placed around a circumference. We have confirmed, through field tests, the applicability of our CCA method to arrays on the order of several to several hundred meters in radii and have revealed its remarkably high performance in long-wavelength ranges, the upper resolution limit extending as far as several 10 times the array radius. We have also invented a mathematical model that enables to evaluate signal-to-noise ratios in a given microtremor field. Scrutiny of field data has borne out our hypothesis that noise is the principal factor that biases the analysis results of the CCA method in long-wavelength ranges and that its longest resolvable wavelength is determined by the signal-to-noise ratio. Combined use of the CCA method and our new method of signal-to-noise ratio analysis provides a powerful methodological tool that allows one to extract maximal information from microtremor records obtained with a simple seismic array.

  4. Near-infrared spectroscopy with Spectroscopic technique with wide range of wavelength information detects tissue oxygenation level clearly

    NASA Astrophysics Data System (ADS)

    Eda, Hideo; Aoki, Hiromichi; Eura, Shigeru; Ebe, Kazutoshi

    2010-02-01

    Near-infrared spectroscopy (NIRS) is based on the modified-Lambert-Beer's law that changes in absorbance are proportional to changes in hemoglobin parameters. Majority of the conventional measurement methods uses only two or three wavelengths. In this research, basic examination of NIRS measurement was approached by acquiring wide range of wavelength information. Arterial occlusion task was performed by using the blood pressure cuff around the upper arm. Pressure of 200mmHg was then applied for about 3 minutes. During the arterial occlusion, the spectrum of the lower arm muscles was measured every 15 seconds, within the range of 600 to 1100nm. The secondary derivative spectrum was calculated from the measured spectrum. Arterial occlusion is a task which changes the oxygenation level of the tissue. The change can be regarded as the change of the spectrum form, not as the change of the baseline. Furthermore, it was found that other wavelength bands hold information correlating to this arterial occlusion task.

  5. Photon detectors with high quantum efficiency at NUV range using a confinement of wavelength-shifted signals and optical couplers

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Hadaway, J.; Pakhomov, A.; Takizawa, Y.

    Near-UV wavelengths 300 - 400 nm have been in a death-valley for photon detectors due to very low quantum efficiencies QE in this range Conventional bi-alkali photocathodes of PMTs do not have QE better than 20-26 Much better photo-cathodes like GaAsP GaN and similar give better efficiencies but only at wavelengths 400nm and are severely plagued by very short lifetimes Avalanche Photo-diodes perform better at low temperatures but no better than 35 QE in the NUV region Silicon Photo-multipliers at Geiger mode SiPM with micro-pixels have high QEs 90 like CCD and CMOS as bare silicon but are severely plagued by very poor geometrical fill-factors 30 and their overallQMis limited to no better than 20 at NUV regime An optical interference-filter works as a half-mirror passing more than 90 of NUV lights 300-400 nm and reflect more than 90 of longer wavelength lights 400 nm UV photons after converted into blue-green lights by wavelength-shifter are reflected back and confined without much loss back into space A specific dichroic interference mirror with WLS was made by RIKEN Japan H Shimizu Y Takahashi Y Takizawa Patent pending 2000-399940 for this optical principle It also allows a better use of limited photo-sensitive micro-cells of SiPM overcoming the past serious problem of its very poor fill-factor As a result Half-mirror SiPM yields high final efficiency for NUV photons This new detector TRAPPER with optical couplers for SiPM or by GaAsP PMTs could be used for photon-hungry space experiments at NUV range TRAPPER

  6. C+L band wavelength division multiplexing access network with distributed-controlled protection architecture

    NASA Astrophysics Data System (ADS)

    Yeh, Chien Hung; Chow, Chi Wai

    2011-12-01

    In this work, we propose and experimentally demonstrate a novel distributed-controlled protection architecture for automatic and fast network restoration in wavelength division multiplexing-passive optical network (WDM-PON). The proposed scheme can support both C and L bands. Besides, duplication of network equipments, such as optical networking unit (ONU) or optical line terminal, is not required. In this distributed-controlled system, each ONU can always keep track of the network status. Hence, this can facilitate the network manage by removing the work loads from the central office. Besides, the proposed scheme can tolerate simultaneous fiber cuts in the feeder and distributed fibers.

  7. Femtosecond laser nanostructuring of titanium metal towards fabrication of low-reflective surfaces over broad wavelength range

    NASA Astrophysics Data System (ADS)

    Dar, Mudasir H.; Kuladeep, R.; Saikiran, V.; Narayana Rao, D.

    2016-05-01

    We investigated experimentally the formation of laser induced periodic surface structures (LIPSS) on titanium (Ti) metal upon irradiation with linearly polarized Ti:Sapphire femtosecond (fs) laser pulses of ∼110 fs pulse width and 800 nm wavelength in air and water environments. It is observed that initially formed random and sparsely distributed nano-roughness (nanoholes, nanoparticles and nanoprotrusions) gets periodically structured with increase in number of laser pulses. In air at lower fluence, we observed the formation of high spatial frequency-LIPSS (HSFL) oriented parallel to the laser polarization direction, whereas at higher fluence formation of low spatial frequency-LIPSS (LSFL) were observed that are oriented perpendicular to the incident laser polarization. In water two types of subwavelength structures were observed, one with spatial periodicity of ∼λ/15 and oriented parallel to laser polarization, while the other oriented perpendicular to laser polarization with feature size of λ/4. The optimal conditions for fabricating periodic sub-wavelength structures are determined by controlling the fluence and pulse number. The fs laser induced surface modifications were found to suppress the specular reflection of the Ti surface over a wide wavelength range of 250-2000 nm to a great extent.

  8. Selective treatment of carious dentin using a mid-infrared tunable pulsed laser at 6 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Saiki, Masayuki; Ishii, Katsunori; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2011-03-01

    Optical technologies have good potential for caries detection, prevention, excavation, and the realization of minimal intervention dentistry. This study aimed to develop a selective excavation technique of carious tissue using the specific absorption in 6 μm wavelength range. Bovine dentin demineralized with lactic acid solution was used as a carious dentin model. A mid-infrared tunable pulsed laser was obtained by difference-frequency generation technique. The wavelength was tuned to 6.02 and 6.42 μm which correspond to absorption bands called amide I and amide II, respectively. The laser delivers 5 ns pulse width at a repetition rate of 10 Hz. The morphological change after irradiation was observed with a scanning electron microscope, and the measurement of ablation depth was performed with a confocal laser microscope. At λ = 6.02 μm and the average power density of 15 W/cm2, demineralized dentin was removed selectively with less-invasive effect on sound dentin. The wavelength of 6.42 μm also showed the possibility of selective removal. High ablation efficiency and low thermal side effect were observed using the nanosecond pulsed laser with λ = 6.02 μm. In the near future, development of compact laser device will open the minimal invasive laser treatment to the dental clinic.

  9. A HIGH-RESOLUTION, MULTI-EPOCH SPECTRAL ATLAS OF PECULIAR STARS INCLUDING RAVE, GAIA , AND HERMES WAVELENGTH RANGES

    SciTech Connect

    Tomasella, Lina; Munari, Ulisse; Zwitter, Tomaz

    2010-12-15

    We present an Echelle+CCD, high signal-to-noise ratio, high-resolution (R = 20,000) spectroscopic atlas of 108 well-known objects representative of the most common types of peculiar and variable stars. The wavelength interval extends from 4600 to 9400 A and includes the RAVE, Gaia, and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of the observed stars. A total of 425 spectra of peculiar stars, which were collected during 56 observing nights between 1998 November and 2002 August, are presented. The spectra are given in FITS format and heliocentric wavelengths, with accurate subtraction of both the sky background and the scattered light. Auxiliary material useful for custom applications (telluric dividers, spectrophotometric stars, flat-field tracings) is also provided. The atlas aims to provide a homogeneous database of the spectral appearance of stellar peculiarities, a tool useful both for classification purposes and inter-comparison studies. It could also serve in the planning and development of automated classification algorithms designed for RAVE, Gaia, HERMES, and other large-scale spectral surveys. The spectrum of XX Oph is discussed in some detail as an example of the content of the present atlas.

  10. Stimulated Raman scattering cascade spanning the wavelength range of 523 to 1750 nm using a graded-index multimode optical fiber

    NASA Astrophysics Data System (ADS)

    Pourbeyram, Hamed; Agrawal, Govind P.; Mafi, Arash

    2013-05-01

    We report on the generation of a Raman cascade spanning the wavelength range of 523 to 1750 nm wavelength range in a standard telecommunication graded-index multimode optical fiber. Despite the highly multimode nature of the pump, the Raman peaks are generated in specific modes of the fiber, confirming substantial beam cleanup during the stimulated Raman scattering process.

  11. Design of an extended-range, three-wavelength distance-measuring instrument

    NASA Technical Reports Server (NTRS)

    Moody, S. E.; Levine, J.

    1979-01-01

    The paper describes an extension of current multiwavelength electromagnetic distance measurement (EDM) techniques which should allow the range of multiwavelength measurements to be extended to approximately 50 km. The basic modification needed is the replacement of the retroreflector commonly used by an active station containing lasers and a microwave source. Because the system will always be operated as a full three-wave-length instrument, accuracies of about 5 x 10 to the -8th at 50 km should be obtainable on a routine basis under reasonably clear weather conditions.

  12. High-power cw laser bars of the 750 - 790-nm wavelength range

    SciTech Connect

    Degtyareva, N S; Kondakov, S A; Mikayelyan, G T; Gorlachuk, P V; Ladugin, M A; Marmalyuk, Aleksandr A; Ryaboshtan, Yu L; Yarotskaya, I V

    2013-06-30

    We have developed the effective design of semiconductor heterostructures, which allow one to fabricate cw laser diodes emitting in the 750 - 790-nm spectral range. The optimal conditions for fabrication of GaAsP/AlGaInP/GaAs heterostructures by MOCVD have been determined. It is shown that the use of quantum wells with a precisely defined quantity mismatch reduces the threshold current density and increases the external differential efficiency. The results of studies of characteristics of diode laser bars fabricated from these heterostructures are presented. (lasers)

  13. High-performance optically pumped GaSb-based semiconductor disk lasers for the 2.Xμm wavelength range

    NASA Astrophysics Data System (ADS)

    Rattunde, M.; Schulz, N.; Rösener, B.; Manz, C.; Köhler, K.; Wagner, J.; Hopkins, J.-M.; Burns, D.

    2008-02-01

    We report on recent advances in the performance of GaSb-based optically pumped semiconductor disk lasers (OPSDLs), emitting in the 2.0 - 2.3 μm wavelength range. Both barrier pumped OPSDL (using 980 nm laser diodes as pump source) and in-well pumped OPSDL (using 1.96 μm pump radiation) have been fabricated and characterized. Using alternative SiC or diamond intracavity heatspreader, multiple-watt CW-output powers have been achieved (e.g. >3W at 2.3 μm and >5W at 2.0 μm), with power efficiencies in the range of 18 % - 25 %. For an optimised resonator setup, the beam profile is close to the diffraction limit with M2 values around 1.2; and even for the highest power levels, M2 is in the range of 2-5.

  14. Low-cost tissue simulating phantoms with adjustable wavelength-dependent scattering properties in the visible and infrared ranges

    NASA Astrophysics Data System (ADS)

    Saager, Rolf B.; Quach, Alan; Rowland, Rebecca A.; Baldado, Melissa L.; Durkin, Anthony J.

    2016-06-01

    We present a method for low-cost fabrication of polydimethylsiloxane (PDMS) tissue simulating phantoms with tunable scattering spectra, spanning visible, and near-infrared regimes. These phantoms use optical polishing agents (aluminum oxide powders) at various grit sizes to approximate in vivo tissue scattering particles across multiple size distributions (range: 17 to 3 μm). This class of tunable scattering phantoms is used to mimic distinct changes in wavelength-dependent scattering properties observed in tissue pathologies such as partial thickness burns. Described by a power-law dependence on wavelength, the scattering magnitude of these phantoms scale linearly with particle concentration over a physiologic range [μs‧=(0.5 to 2.0 mm-1)] whereas the scattering spectra, specific to each particle size distribution, correlate to distinct exponential coefficients (range: 0.007 to 0.32). Aluminum oxide powders used in this investigation did not detectably contribute to the absorption properties of these phantoms. The optical properties of these phantoms are verified through inverse adding-doubling methods and the tolerances of this fabrication method are discussed.

  15. Large-Area Sub-Wavelength Optical Patterning via Long-Range Ordered Polymer Lens Array.

    PubMed

    Wu, Jin; Liow, Chihao; Tao, Kai; Guo, Yuanyuan; Wang, Xiaotian; Miao, Jianmin

    2016-06-29

    Fabrication of large-area, highly orderly, and high-resolution nanostructures in a cost-effective fashion prompts advances in nanotechnology. Herein, for the first time, we demonstrate a unique strategy to prepare a long-range highly regular polymer lens from photoresist nanotrenches based templates, which are obtained from underexposure. The relationship between exposure dose and the cross-sectional morphology of produced photoresist nanostructures is revealed for the first time. The polymer lens arrays are repeatedly used for rapid generation of sub-100 nm nanopatterns across centimeter-scale areas. The light focusing properties of the nanoscale polymer lens are investigated by both simulation and experiment. It is found that the geometry, size of the lens, and the exposure dose can be deployed to adjust the produced feature size, spacing, and shapes. Because the polymer lenses are derived from top-down photolithography, the nearly perfect long-range periodicity of produced nanopatterns is ensured, and the feature shapes can be flexibly designed. Because this nanolithographic strategy enables subwavelength periodical nanopatterns with controllable feature size, geometry, and composition in a cost-effective manner, it can be optimized as a viable and potent nanofabrication tool for various technological applications. PMID:27301636

  16. Synthetic spectra of cool stars for the wavelength range 2550-3200 A

    NASA Technical Reports Server (NTRS)

    Eaton, Joel A.

    1986-01-01

    In order to interpret the ultraviolet spectra of cool stars obtained with IUE and to determine the physical conditions in their outer atmospheres, synthetic IUE spectra of stars cooler than the Sun, mainly the Sun and the metal-deficient, carbon-rich CH stars were calculated. Results are encouraging. Synthetic spectra for the Sun over the range 2550 to 3300 A give roughly the observed level of overall emission and relative strengths or various absorption features (Fe II, Mg II, Mg I, and Fe I) although they still require extra sources of continuous opacity longward of 2650 A. Spectra of the CH stars have roughly the correct shape in the ultraviolet continuum for the expected effective temperature, although these models are problematic in that the electron density, hence H(-) opacity, is directly proportional to the Mg-Si-Fe density and the ratio of line to continuum opacity is only slightly affected by changing metallicity.

  17. A Sounding Rocket Mission Concept to Acquire High-Resolution Radiometric Spectra Spanning the 9 nm - 31 nm Wavelength Range

    NASA Technical Reports Server (NTRS)

    Krause, L. Habash; Cirtain, Jonathan; McGuirck, Michael; Pavelitz, Steven; Weber, Ed.; Winebarger, Amy

    2012-01-01

    When studying Solar Extreme Ultraviolet (EUV) emissions, both single-wavelength, two- dimensional (2D) spectroheliograms and multi-wavelength, one-dimensional (1D) line spectra are important, especially for a thorough understanding of the complex processes in the solar magnetized plasma from the base of the chromosphere through the corona. 2D image data are required for a detailed study of spatial structures, whereas radiometric (i.e., spectral) data provide information on relevant atomic excitation/ionization state densities (and thus temperature). Using both imaging and radiometric techniques, several satellite missions presently study solar dynamics in the EUV, including the Solar Dynamics Observatory (SDO), Hinode, and the Solar-Terrestrial Relations Observatory (STEREO). The EUV wavelengths of interest typically span 9 nm to 31 nm, with the shorter wavelengths being associated with the hottest features (e.g., intense flares and bright points) and the longer wavelengths associated with cooler features (e.g., coronal holes and filaments). Because the optical components of satellite instruments degrade over time, it is not uncommon to conduct sounding rocket underflights for calibration purposes. The authors have designed a radiometric sounding rocket payload that could serve as both a calibration underflight for and a complementary scientific mission to the upcoming Solar Ultraviolet Imager (SUVI) mission aboard the GOES-R satellite (scheduled for a 2015 launch). The challenge to provide quality radiometric line spectra over the 9-31 nm range covered by SUVI was driven by the multilayer coatings required to make the optical components, including mirrors and gratings, reflective over the entire range. Typically, these multilayers provide useful EUV reflectances over bandwidths of a few nm. Our solution to this problem was to employ a three-telescope system in which the optical components were coated with multilayers that spanned three wavelength ranges to cover

  18. ABSORPTION CROSS SECTION OF GASEOUS ACETYLENE AT 85 K IN THE WAVELENGTH RANGE 110-155 nm

    SciTech Connect

    Cheng, Bing-Ming; Chen, Hui-Fen; Lu, Hsiao-Chi; Chen, Hong-Kai; Alam, M. S.; Chou, Sheng-Lung; Lin, Meng-Yeh

    2011-09-01

    Absorption spectra and absorption cross sections of gaseous acetylene, C{sub 2}H{sub 2}, at 298 and 85 K were measured in the wavelength range 110-155 nm with a slit-jet system coupled to a synchrotron as a source of vacuum ultraviolet light. Using published spectral parameters of C{sub 2}H{sub 2}, we simulated the absorption profile for the Rydberg transition to state 4R{sub 0} in the range 124.6-125.1 nm, according to which the temperature of the jet-expanded sample at stagnation pressure 200 Torr is 85 {+-} 5 K. Our cross sections of C{sub 2}H{sub 2} are applicable for determining properties sensitive to temperature for diagnostic work on Saturn and Titan.

  19. Normal-incidence Sb/B{sub 4}C multilayer mirrors for the 80 A < {lambda} < 120 A wavelength range

    SciTech Connect

    Vishnyakov, E A; Voronov, D L; Gullikson, E M; Kondratenko, V V; Kopylets, I A; Luginin, M S; Pirozhkov, A S; Ragozin, Evgenii N; Shatokhin, A N

    2013-07-31

    Periodic and aperiodic Sb/B4C multilayer structures have been theoretically calculated and synthesised for the first time for the application in soft X-ray optics in the 80 A < {lambda} < 120 A range. The reflection spectra of the periodic multilayer mirrors are measured using synchrotron radiation and laser plasma-generated radiation. The experimental spectra are theoretically interpreted with the inclusion of transition layers and substrate roughness. The density of antimony layers is supposedly {rho}{sub (Sb)} = 6.0 g cm{sup -3}, and the thickness of transition layers (if any) in the Sb/B4C multilayer structures does not exceed 10 A. A peak reflectivity of 19 % is attained at a wavelength of 85 A. An aperiodic mirror optimised for maximum uniform reflectivity in the 100 - 120 A range is tested employing the laser plasma radiation source. (x-ray optics)

  20. Estimation of potential abilities of middle atmosphere density measurements from a near-Earth orbit within the UV wavelength range

    NASA Astrophysics Data System (ADS)

    Marichev, V. N.; Bochkovskii, D. A.; Sorokin, I. V.; Bychkov, V. V.

    2016-05-01

    Analysis of errors in atmospheric density measurements by lidar on board the ISS is performed. It is shown that using as the lidar transmitter a Nd:YAG laser with moderate parameters of emission at a wavelength of 353 nm and a receiving mirror diameter of 0.4 m, it is possible to cover with a 10% measurement error a height range, on average, from 40-60 km and 30-40 km in the nighttime and daytime, respectively, down to the troposphere. Working with emission at 266 nm with a 10% error, it is possible to move to the heights of the mesosphere (70 km) and penetrate the atmosphere down to a height of 40 km. Thus, the use of two harmonics makes it possible to assimilate the height range of atmospheric density measurements from on board the ISS beginning from 70 km and down to the troposphere.

  1. Asynchronous detection of optical code division multiple access signals using a bandwidth-efficient and wavelength-aware receiver.

    PubMed

    Fok, Mable P; Deng, Yanhua; Prucnal, Paul R

    2010-04-01

    We experimentally demonstrate what we believe to be a novel detection scheme for interfacing asynchronous optical code division multiple access (CDMA) signals with an electronic clock and data recovery system that operates only at the baseband bandwidth. This allows using a large optical bandwidth expansion factor in which the optical chip rate is much larger than the bandwidth of the optoelectronic receiver. The received optical CDMA signal is launched into a four-wave-mixing-based wavelength-aware all-optical front end that rejects multiaccess interference, followed by an amplitude-noise suppression stage comprised of a semiconductor optical amplifier. The clean signal is then converted into a non-return-to-zero-like signal by a baseband receiver. Using the proposed detection scheme, asynchronous transmission and detection of optical CDMA signals is implemented. With the novel detection scheme, the classic CDMA near-far problem is mitigated, and error-free detection is easily obtained.

  2. Glacial modifications of short-wavelength topography and potential feedbacks on the denudation of a deglaciated mountain range

    NASA Astrophysics Data System (ADS)

    Salcher, Bernhard; Kober, Florian; Kissling, Eduard; Willett, Sean

    2014-05-01

    Distinct erosional landforms in the European Alps and other mid- to high-latitude mountain belts highlight the importance of glacial erosion in shaping mountain topography. Here we focus on the glacially induced modifications to the short-wavelength topography of the European Central Alps in an attempt to characterize the impact of glacial erosion on topography and to highlight potential feedback mechanisms on the denudation of the deglaciated mountain range. Glacial induced changes to the short-wavelength topography were analyzed by measuring the variations of drainage density and hillslope relief across the range. Variations of denudation rates were analyzed by compiling catchment-averaged concentrations of cosmogenic 10Be from existing studies covering Alpine and Foreland basins. Our results underline the importance of the LGM ELA elevation (i.e. the Equilibrium Line Altitude at the Late Glacial Maximum) as an important limit for the destruction of short-wavelength topography: The cumulative impact of glacial erosion above the LGM ELA has progressively decreased (i) drainage density, (ii) channel integration and (iii) commensurately increased hillslopes length (or hillslope relief). Exceptions from this trend are the highest and steepest peaks and ridges, nunataks even during the LGM. Alpine catchments in the orogen parts below this limit (i.e. Alpine foothills) lack strong modifications by glaciers. Here, glacial erosion is largely restricted to glacial troughs. There is also a statistically significant correlation between drainage density (or hillslope length) and catchment-wide denudation rates. The correlation does not define a single-valued function; rather there are two populations above and below the LGM ELA, one with a positive correlation for low-elevation, fluvially-dominated landscapes and a second for high-elevation, glacially-eroded basins in which this correlation is negative. We speculate that the commensurate lengthening of hillslopes increase

  3. Detector system with high time resolution for the continuous measurement of spectra in the vacuum ultraviolet wavelength range

    NASA Astrophysics Data System (ADS)

    Biel, W.; Bertschinger, G.

    2004-07-01

    A new detector system with high time resolution (1 ms) has been developed and applied for the continuous measurement of spectra in the vacuum ultraviolet (VUV) and extreme ultraviolet (EUV) wavelength region at the fusion plasma experiment Torus Experiment for Technology-Oriented Research (TEXTOR). The system consists of an open multichannel-plate (MCP) detector with subsequent first generation (Gen I) light amplifier and a camera head which is based on a linear photodiode array with 1024 elements (pixels). The camera head provides the output signals of the individual pixels sequentially as an analog voltage with a full spectra rate of 1000 per second, which are measured using a PC-based data acquisition system. Three vacuum spectrometers operating in the VUV/EUV region (10-130 nm) have been equipped with the new system and a successful campaign of measurements from about 4000 discharges at TEXTOR has been performed. Spectra are recorded with a usable linear dynamic range of 10 bit and a wavelength resolution corresponding to a width of 3-4 pixels.

  4. Online surface characterization of paper and paperboards in a wide-range of the spatial wavelength spectrum

    NASA Astrophysics Data System (ADS)

    Alam, Anzar; Thim, Jan; O'Nils, Mattias; Manuilskiy, Anatoliy; Lindgren, Johan; Lidén, Joar

    2012-08-01

    In the paper industry, surface topography is the essence of both paper and paperboard, and accurate topographical measurements are equally essential in order to achieve a uniform smooth surface. The traditional laboratory methods measure only a few samples from the entire tambour and there are other obvious limitations to this approach. Online measurements may be of significant value to improve the surface quality throughout the production. Roughness is one of the topography components and the majority of techniques measure paper by means of a single predictor of average roughness, Ra which is inadequate in providing a comprehensive characterization of the surface. Measurements, in a wide range of wavelengths, can characterize topography components such as roughness, waviness, cockling, etc. Online measurements were taken for various grades of 8 paper reels, containing the wireside and topsides for newspaper, and uncoated and coated sides of paperboards. Their surface characterization, in the spatial wavelength spectrum, from 0.1 to 10 mm was obtained. This article presents the online characterization results which have efficiently distinguished the surfaces of same family materials including the edge and the middle position reels of fine coated paperboard. Online measurements were taken, at Iggesund Paperboard Pilot Coater in Sweden, by using a recently developed Online Topography (OnTop) device which is based on the principle of light triangulation.

  5. Operation of a free electron laser in the wavelength range from the extreme ultraviolet to the water window

    SciTech Connect

    Ackermann, W.; Asova, G.; Ayvazyan, V.; Azima, A.; Baboi, N.; Bahr, J.; Balandin, V.; Beutner, B.; Brandt, A.; Bolzmann, A.; Brinkmann, R.; /DESY /Dubna, JINR

    2007-01-01

    We report results on the performance of a free-electron laser operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have been measured. In the saturation regime, the peak energy approached 170 J for individual pulses, and the average energy per pulse reached 70 J. The pulse duration was in the region of 10 fs, and peak powers of 10 GW were achieved. At a pulse repetition frequency of 700 pulses per second, the average extreme-ultraviolet power reached 20 mW. The output beam also contained a significant contribution from odd harmonics of approximately 0.6% and 0.03% for the 3rd (4.6 nm) and the 5th (2.75 nm) harmonics, respectively. At 2.75 nm the 5th harmonic of the radiation reaches deep into the water window, a wavelength range that is crucially important for the investigation of biological samples.

  6. Review of polarization techniques for optimal performance of one and two color wavelength laser range finders and designators

    NASA Astrophysics Data System (ADS)

    Avila, Marco A.

    2015-02-01

    Laser range finders (LRF) and target designators (TD) for military applications usually have stringent environmental requirements for optimal performance. Current technology and system architectures need LRF and TD lasers to function in more than one color (near IR and eye safe wavelengths) for multiple ground and airborne applications. In addition, these kind of lasers need to be packaged inside a small space for portability. It is for these reasons that a folded crossed porro-polarization- out coupled resonators is usually the chosen geometry. This work will explore polarization techniques to design a laser resonator cavity that works perfectly for more than one color, sometimes without the need of actual birefringence components (i.e waveplates) to achieve the goal of a stable laser resonator.

  7. Extending the applicability of the Arndt formula in wavelength modulation spectroscopy for absorbance in the lower percent range

    NASA Astrophysics Data System (ADS)

    Hartmann, A.; Strzoda, R.; Schrobenhauser, R.; Weigel, R.

    2014-01-01

    The Arndt formula for Lorentzian signals broadened by modulation is enhanced for the usage on 2f WMS (wavelength modulation spectroscopy) signals produced by spectroscopic lines with high absorption (percent range). Next to the first order approach of the Beer-Lambert law, which is covered by the Arndt formula, a second order term is included for a better approximation of the damped Lorentzian line shape. This second order approximation of the 2f signal can be described by a combination of several components created by the Arndt formula. The error of a pure Arndt evaluation and the improvement of the Arndt extended technique are illustrated in the example of a humidity measurement performed at 100 °C and up to 100 vol%. The energy transition at ν=10,526.274910 cm-1 is used in this setup. With the presented technique, the error is reduced by a factor of 90.

  8. Effect of encoder--decoder mismatch due to wavelength and time misalignments on the performance of two-dimensional wavelength--time optical code-division multiple access systems.

    PubMed

    Adams, Rhys; Chen, Lawrence R

    2005-07-10

    We examine the effects of encoder and decoder mismatch due to wavelength and time chip misalignments on the bit-error rate (BER) performance of two-dimensional (2D) wavelength--time optical code-division multiple access systems. We investigate several instances of misalignment in the desired user encoder and decoder as well as in the interfering user encoders. Our simulation methodology can be used to analyze any type of 2D wavelength--time code family as well as probability distribution for misalignment. For illustration purposes, we consider codes generated by use of the depth-first search algorithm and a Gaussian distribution for the misalignment. Our simulation results show that, in the case of a misalignment in either wavelength or time chip, the variance of the distribution for the misalignment must be below 0.01 for the corresponding degradation in the BER system's performance to be less than 1 order of magnitude compared with that when there is no mismatch between the encoders and decoders. The tolerances become even more strict when misalignments in both wavelength and time chips are considered. Furthermore, our results show that the effect of misalignment in wavelength (time chips) is the same regardless of the number of wavelengths (time chips) used in the codes.

  9. Wavelength-encoding/temporal-spreading optical code division multiple-access system with in-fiber chirped moiré gratings.

    PubMed

    Chen, L R; Smith, P W; de Sterke, C M

    1999-07-20

    We propose an optical code division multiple-access (OCDMA) system that uses in-fiber chirped moiré gratings (CMG's) for encoding and decoding of broadband pulses. In reflection the wavelength-selective and dispersive nature of CMG's can be used to implement wavelength-encoding/temporal-spreading OCDMA. We give examples of codes designed around the constraints imposed by the encoding devices and present numerical simulations that demonstrate the proposed concept.

  10. Alleviating a form of electric vehicle range anxiety through on-demand vehicle access

    NASA Astrophysics Data System (ADS)

    King, Christopher; Griggs, Wynita; Wirth, Fabian; Quinn, Karl; Shorten, Robert

    2015-04-01

    On-demand vehicle access is a method that can be used to reduce types of range anxiety problems related to planned travel for electric vehicle owners. Using ideas from elementary queueing theory, basic quality of service (QoS) metrics are defined to dimension a shared fleet to ensure high levels of vehicle access. Using mobility data from Ireland, it is argued that the potential cost of such a system is very low.

  11. Prospects for high power Linac Coherent Light Source (LCLS) development in the 1000{angstrom} {minus} 1{angstrom} wavelength range

    SciTech Connect

    Tatchyn, R.; Bane, K.; Boyce, R.

    1994-03-01

    Electron bunch requirements for single-pass saturation of a Free-Electron Laser (FEL) operating at full transverse coherence in the Self-Amplified Spontaneous Emission (SASE) mode include: (1) a high peak current, (2) a sufficiently low relative energy spread, and (3) a transverse emittance {var_epsilon}[r-m] satisfying the condition {var_epsilon} {le} {lambda}A/4{pi}, where {lambda}[m] is the output wavelength of the FEL. In the insertion device that induces the coherent amplification, the prepared electron bunch must be kept on a trajectory sufficiently collinear with the amplified photons without significant dilution of its transverse density. In this paper we discuss a Linac Coherent Light Source (LCLS) based on a high energy accelerator such as, e.g., the 3km S-band structure at the Stanford Linear Accelerator Center (SLAC), followed by a long high-precision undulator with superimposed quadrupole (FODO) focusing, to fulfill the given requirements for SASE operation in the 1000{Angstrom}--1{Angstrom} range. The electron source for the linac, an RF gun with a laser-excited photocathode featuring a normalized emittance in the 1--3 mm-mrad range, a longitudinal bunch duration of the order of 3 ps, and approximately 10{sup {minus}9} C/bunch, is a primary determinant of the required low transverse and longitudinal emittances. Acceleration of the injected bunch to energies in the 5--25 GeV range is used to reduce the relative longitudinal energy spread in the bunch, as well as to reduce the transverse emittance to values consistent with the cited wavelength regime. Two longitudinal compression stages are employed to increase the peak bunch current to the 2--5 kA levels required for sufficiently rapid saturation. The output radiation is delivered, via a grazing-incidence mirror bank, to optical instrumentation and a multi-user beam line system. Technological requirements for LCLS operation at 40{Angstrom}, 4.5{Angstrom}, and 1.5{Angstrom} are examined.

  12. Characterization of long-range transported Saharan dust across the Atlantic Ocean; dual-wavelength lidar measurements during SALTRACE

    NASA Astrophysics Data System (ADS)

    Gross, Silke; Freudenthaler, Volker; Schäfler, Andreas; Schepanski, Kerstin; Heinold, Bernd; Toledano, Carlos; Wiegner, Matthias; Weinzierl, Bernadett

    2015-04-01

    Mineral dust is a major component of the atmospheric aerosol load which main source region is the Saharan desert. Dust layers can be transported over thousands of kilometers and thus they cannot be considered as regional phenomenon. During long-range transport the particles are influenced by aging and mixing processes altering the microphysical and thus the optical properties of Saharan dust. But the influence of long-range transport on the particle properties and their effect on the Earth's radiation budget is still not well understood. To study aging processes of transported Saharan dust as well as the microphysical, optical and radiative properties of long-range transported dust the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) took place at Barbados in June and July 2013. SALTRACE was designed as closure study combining ground-based and airborne lidar and in-situ measurements with Satellite observations, long-term measurements at Barbados, and model calculations. During SALTRACE four main dust events occurred with column integrated AOD of up to 0.6. The vertical aerosol distribution was characterized by a three layer structure consisting of a marine dominated boundary layer, a highly variable mixing layer often affected by clouds, and a Saharan dust layer in heights between 2 km and 3.5 km in some cases even up to 5 km. We will present first results of the ground-based measurements with the dual-wavelength lidar system POLIS of the Meteorological Institute of the Ludwig-Maximilians Universität, München. In particular we will investigate measurements of the particle linear depolarization ratio and the lidar ratio of the different aerosol layers. We compare our findings with results of the Saharan Mineral Dust Experiment (SAMUM) studying Saharan dust close to the source region in Morocco and at the beginning of the long-range transport on the Cape Verde Islands. In addition, we assess the influence of long-range

  13. Optical properties of dental restorative materials in the wavelength range 400 to 700 nm for the simulation of color perception.

    PubMed

    Friebel, Moritz; Povel, Kirsten; Cappius, Hans-Joachim; Helfmann, Jürgen; Meinke, Martina

    2009-01-01

    Aesthetic restorations require dental restorative materials to have optical properties very similar to those of the teeth. A method is developed to this end to determine the optical parameters absorption coefficient mu(a), scattering coefficient mu(s), anisotropy factor g, and effective scattering coefficient mu(s) (') of dental restorative materials. The method includes sample preparation and measurements of transmittance and reflectance in an integrating sphere spectrometer followed by inverse Monte Carlo simulations. Using this method the intrinsic optical parameters are determined for shade B2 of the light-activated composites TPH((R)) Spectrum, Esthet-X, and the Ormocer Definite in the wavelength range 400 to 700 nm. By using the determined parameters mu(a), mu(s), and g together with an appropriate phase function, the reflectance of samples with 1-mm layer thickness and shade B2 could be predicted with a very high degree of accuracy using a forward Monte Carlo simulation. The color perception was calculated from the simulated reflectance according to the CIELAB system. We initiate the compilation of a data pool of optical parameters that in the future will enable calculation models to be used as a basis for optimization of the optical approximation of the natural tooth, and the composition of new materials and their production process.

  14. Optical properties of dental restorative materials in the wavelength range 400 to 700 nm for the simulation of color perception

    NASA Astrophysics Data System (ADS)

    Friebel, Moritz; Povel, Kirsten; Cappius, Hans-Joachim; Helfmann, Jürgen; Meinke, Martina

    2009-09-01

    Aesthetic restorations require dental restorative materials to have optical properties very similar to those of the teeth. A method is developed to this end to determine the optical parameters absorption coefficient μa, scattering coefficient μs, anisotropy factor g, and effective scattering coefficient μs' of dental restorative materials. The method includes sample preparation and measurements of transmittance and reflectance in an integrating sphere spectrometer followed by inverse Monte Carlo simulations. Using this method the intrinsic optical parameters are determined for shade B2 of the light-activated composites TPH® Spectrum®, Esthet-X®, and the Ormocer® Definite® in the wavelength range 400 to 700 nm. By using the determined parameters μa, μs, and g together with an appropriate phase function, the reflectance of samples with 1-mm layer thickness and shade B2 could be predicted with a very high degree of accuracy using a forward Monte Carlo simulation. The color perception was calculated from the simulated reflectance according to the CIELAB system. We initiate the compilation of a data pool of optical parameters that in the future will enable calculation models to be used as a basis for optimization of the optical approximation of the natural tooth, and the composition of new materials and their production process.

  15. Selective removal of atherosclerotic plaque with a quantum cascade laser in the 5.7 µm wavelength range

    NASA Astrophysics Data System (ADS)

    Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

    2015-11-01

    Atherosclerotic plaques consist mainly of cholesteryl esters, and the C=O stretching vibration mode of cholesteryl esters strongly absorbs radiation at a wavelength of 5.75 µm. For clinical application of less-invasive laser angioplasty with 5.75 µm, a compact laser is required. Quantum cascade lasers (QCLs) are semiconductor lasers that can emit radiation in the mid-IR range. In this study, the potential of the QCL for less-invasive laser angioplasty was evaluated. At the average power density of 180 W/cm2, the atherosclerotic aorta was ablated for the irradiation time of 1 s or more, whereas the normal aorta was ablated for more than 10 s. This demonstrates that selective ablation of the atherosclerotic aorta was achieved. However, strong coagulation and carbonization were observed. For reducing thermal effects, improving the pulse structure is required. In conclusion, the QCL achieved the selective ablation of the atherosclerotic lesions, which indicates the potential of the QCL.

  16. On the reaction of adult Rhipicephalus evertsi mimeticus and Hyalomma truncatum to horizontally incidenting optical radiation of various wavelengths ranges and different irradiances and to optical radiation of a sun-simulating wavelength spectrum.

    PubMed

    Leuterer, G; Gothe, R

    1991-01-01

    The valence of horizontally incidenting light/optical radiation for host-seeking-inclined ixodid ticks was investigated by exposing male and female adults of Rhipicephalus evertsi mimeticus and Hyalomma truncatum to narrow-band monochromatic radiation in the wavelength range of 300-801 nm at irradiances corresponding to an overcast to clear sunny day, a cloudy day and a full-moon night as well as to optical radiation of a sun-simulating wavelength spectrum of 190-2600 nm within a test chamber from which other stimuli were excluded. It was demonstrated that independent of sex, adult ticks of R. e. mimeticus and H. truncatum responded to a wide wavelength spectrum in the visible and UV range, even at irradiances corresponding to a full-moon night. Interspecific differences existed in the degree and extent of the response as well as in the spectral sensitivity. Ticks of H. truncatum consistently showed a faster and stronger response and reacted phototactically positively in higher percentages than adults of R. e. mimeticus. Independent of wavelength range and irradiance, predominantly only few R. e. mimeticus ticks were stimulated to positive phototaxis, whereas at least 33.3% (in most cases, 50%) and maximally greater than 80% of H. truncatum adults reacted phototactically positively. Spectral sensitivity maxima were demonstrated at the yellow and red light and at the UV-A waveband width for R. e. mimeticus and at the violet, blue, green and yellow light wavelength for H. truncatum. With decreasing irradiance, the spectral sensitivity shifted to the blue wavelength range.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1866424

  17. 2 μm wavelength range InP-based type-II quantum well photodiodes heterogeneously integrated on silicon photonic integrated circuits.

    PubMed

    Wang, Ruijun; Sprengel, Stephan; Muneeb, Muhammad; Boehm, Gerhard; Baets, Roel; Amann, Markus-Christian; Roelkens, Gunther

    2015-10-01

    The heterogeneous integration of InP-based type-II quantum well photodiodes on silicon photonic integrated circuits for the 2 µm wavelength range is presented. A responsivity of 1.2 A/W at a wavelength of 2.32 µm and 0.6 A/W at 2.4 µm wavelength is demonstrated. The photodiodes have a dark current of 12 nA at -0.5 V at room temperature. The absorbing active region of the integrated photodiodes consists of six periods of a "W"-shaped quantum well, also allowing for laser integration on the same platform.

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

    PubMed

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

    2014-06-01

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

  19. [Corrective effects of electromagnetic radiation in a millimeter wavelength range on the parameters of oxidative stress after standard anti-helicobacterial therapy in patients with ulcer disease].

    PubMed

    Ivanishkina, E V; Podoprigorova, V G

    2012-01-01

    We assessed the possibilities of correction of oxidative stress parameters in the serum and gastroduodenal mucosa using electromagnetic radiation in a millimeter wavelength range in 127 patients with gastric and duodenal ulcer after eradication therapy. Control group included 230 healthy subjects. Parameter of lipid oxidation by free radicals were measured by direct methods (hemiluminescence and EPR-spectroscopy). The results show that standard eradication therapy does not influence parameters of oxidative stress. More pronounced effect of electromagnetic radiation in a millimeter wavelength range may be due to the correction of prooxidant-antioxidant and antioxidant disbalance. This observation provides pathogenetic substantiation for the inclusion of this physical method in modern therapeutic modalities.

  20. Fast, long-scan-range pump-probe measurement based on asynchronous sampling using a dual-wavelength mode-locked fiber laser.

    PubMed

    Zhao, Xin; Zheng, Zheng; Liu, Lei; Wang, Qi; Chen, Haiwei; Liu, Jiansheng

    2012-11-01

    A simple, fast and long-scan-range pump-probe scheme is experimentally demonstrated using a dual-wavelength passively mode-locked fiber laser. The pulse trains from the dual-wavelength laser have a small difference in their repetition frequencies inherently determined by the intracavity dispersion. This enables the realization of the asynchronous sampling scheme with a tens-of-nanosecond-long delay range and a picosecond scan step at a millisecond scan speed. Instead of two synchronized ultrafast lasers in the traditional asynchronous sampling scheme, just one fiber laser is needed in our scheme, which could significantly simplify the system setup.

  1. Wide range operation of regenerative optical parametric wavelength converter using ASE-degraded 43-Gb/s RZ-DPSK signals.

    PubMed

    Gao, Mingyi; Kurumida, Junya; Namiki, Shu

    2011-11-01

    For sustainable growth of the Internet, wavelength-tunable optical regeneration is the key to scaling up high energy-efficiency dynamic optical path networks while keeping the flexibility of the network. Wavelength-tunable optical parametric regenerator (T-OPR) based on the gain saturation effect of parametric amplification in a highly nonlinear fiber is promising for noise reduction in phase-shift keying signals. In this paper, we experimentally evaluated the T-OPR performance for ASE-degraded 43-Gb/s RZ-DPSK signals over a 20-nm input wavelength range between 1527 nm and 1547 nm. As a result, we achieved improved power penalty performance for the regenerated idler with a proper pump power range.

  2. Wavelength dependent UV inactivation and DNA damage of adenovirus as measured by cell culture infectivity and long range quantitative PCR.

    PubMed

    Beck, Sara E; Rodriguez, Roberto A; Linden, Karl G; Hargy, Thomas M; Larason, Thomas C; Wright, Harold B

    2014-01-01

    Adenovirus is regarded as the most resistant pathogen to ultraviolet (UV) disinfection due to its demonstrated resistance to monochromatic, low-pressure (LP) UV irradiation at 254 nm. This resistance has resulted in high UV dose requirements for all viruses in regulations set by the United States Environmental Protection Agency. Polychromatic, medium-pressure (MP) UV irradiation has been shown to be much more effective than 254 nm, although the mechanisms of polychromatic UV inactivation are not completely understood. This research analyzes the wavelength-specific effects of UV light on adenovirus type 2 by analyzing in parallel the reduction in viral infectivity and damage to the viral genome. A tunable laser from the National Institute of Standards and Technology was used to isolate single UV wavelengths. Cell culture infectivity and PCR were employed to quantify the adenoviral inactivation rates using narrow bands of irradiation (<1 nm) at 10 nm intervals between 210 and 290 nm. The inactivation rate corresponding to adenoviral genome damage matched the inactivation rate of adenovirus infectivity at 253.7 nm, 270 nm, 280 nm, and 290 nm, suggesting that damage to the viral DNA was primarily responsible for loss of infectivity at those wavelengths. At 260 nm, more damage to the nucleic acid was observed than reduction in viral infectivity. At 240 nm and below, the reduction of viral infectivity was significantly greater than the reduction of DNA amplification, suggesting that UV damage to a viral component other than DNA contributed to the loss of infectivity at those wavelengths. Inactivation rates were used to develop a detailed spectral sensitivity or action spectrum of adenovirus 2. This research has significant implications for the water treatment industry with regard to polychromatic inactivation of viruses and the development of novel wavelength-specific UV disinfection technologies. PMID:24266597

  3. Dual-wavelength laser speckle imaging to simultaneously access blood flow, blood volume, and oxygenation using a color CCD camera.

    PubMed

    Wang, Jia; Wang, Yaru; Li, Bing; Feng, Danqi; Lu, Jinling; Luo, Qingming; Li, Pengcheng

    2013-09-15

    We developed a dual-wavelength laser speckle imaging system using a single industrial-grade color CCD camera with Bayer filters to simultaneously image changes in blood flow, blood volume, and oxygenation. One frame of a color image recorded with dual-wavelength laser illumination provides not only the intensity fluctuation of the speckle pattern, but also the dual-wavelength optical reflectance signal. The method was validated using a tissue phantom and cuff ischemia experiments in the human arm. This system achieves complete time synchronization, unlike conventional time-sharing systems. Compared with a multicamera system, it also avoids the problem of image registration and can be less expensive.

  4. Full-Duplex Link Providing Alternative Wired and Wireless Broadband Access for the Wavelength-Division Multiplexing Passive Optical Network with a Uniform Converged Signal Format

    NASA Astrophysics Data System (ADS)

    Ma, Jianxin

    2014-05-01

    A full-duplex link implementing alternative wired and wireless access for wavelength-division multiplexing passive optical network is proposed with the uniformed three-tone converged optical signal, which provides a wired or wireless downlink access signal alternatively and an uplink optical carrier. The uplink optical carrier reversed by the converged optical signal makes the hybrid optical node unit free from the optical source. The simulation results show that the full-duplex link with a 10-Gb/s 16-quadrature amplitude modulation (16-QAM) downstream and 5 Gb/s binary upstream can provide both wired access with a bit-error rate below 10-9 and radio-over-fiber-based wireless access with a bit-error rate below 10-7 over 40 km of fiber without an optical source and optical amplifier in the hybrid optical node unit.

  5. Method for the assessment of effects of a range of wavelengths and intensities of red/near-infrared light therapy on oxidative stress in vitro.

    PubMed

    Giacci, Marcus K; Hart, Nathan S; Hartz, Richard V; Harvey, Alan R; Hodgetts, Stuart I; Fitzgerald, Melinda

    2015-03-21

    Red/near-infrared light therapy (R/NIR-LT), delivered by laser or light emitting diode (LED), improves functional and morphological outcomes in a range of central nervous system injuries in vivo, possibly by reducing oxidative stress. However, effects of R/NIR-LT on oxidative stress have been shown to vary depending on wavelength or intensity of irradiation. Studies comparing treatment parameters are lacking, due to absence of commercially available devices that deliver multiple wavelengths or intensities, suitable for high through-put in vitro optimization studies. This protocol describes a technique for delivery of light at a range of wavelengths and intensities to optimize therapeutic doses required for a given injury model. We hypothesized that a method of delivering light, in which wavelength and intensity parameters could easily be altered, could facilitate determination of an optimal dose of R/NIR-LT for reducing reactive oxygen species (ROS) in vitro. Non-coherent Xenon light was filtered through narrow-band interference filters to deliver varying wavelengths (center wavelengths of 440, 550, 670 and 810 nm) and fluences (8.5x10(-3) to 3.8x10(-1) J/cm2) of light to cultured cells. Light output from the apparatus was calibrated to emit therapeutically relevant, equal quantal doses of light at each wavelength. Reactive species were detected in glutamate stressed cells treated with the light, using DCFH-DA and H2O2 sensitive fluorescent dyes. We successfully delivered light at a range of physiologically and therapeutically relevant wavelengths and intensities, to cultured cells exposed to glutamate as a model of CNS injury. While the fluences of R/NIR-LT used in the current study did not exert an effect on ROS generated by the cultured cells, the method of light delivery is applicable to other systems including isolated mitochondria or more physiologically relevant organotypic slice culture models, and could be used to assess effects on a range of outcome

  6. Wavelength-Modulated Differential Photoacoustic (WM-DPA) imaging: a high dynamic range modality towards noninvasive diagnosis of cancer

    NASA Astrophysics Data System (ADS)

    Dovlo, Edem; Lashkari, Bahman; Choi, Sung soo Sean; Mandelis, Andreas

    2016-03-01

    This study explores wavelength-modulated differential photo-acoustic (WM-DPA) imaging for non-invasive early cancer detection via sensitive characterization of functional information such as hemoglobin oxygenation (sO2) levels. Well-known benchmarks of tumor formation such as angiogenesis and hypoxia can be addressed this way. While most conventional photo-acoustic imaging has almost entirely employed high-power pulsed lasers, frequency-domain photo-acoustic radar (FD-PAR) has seen significant development as an alternative technique. It employs a continuous wave laser source intensity-modulated and driven by frequency-swept waveforms. WM-DPA imaging utilizes chirp modulated laser beams at two distinct wavelengths for which absorption differences between oxy- and deoxygenated hemoglobin are minimum (isosbestic point, 805 nm) and maximum (680 nm) to simultaneously generate two signals detected using a standard commercial array transducer as well as a single-element transducer that scans the sample. Signal processing is performed using Lab View and Matlab software developed in-house. Minute changes in total hemoglobin concentration (tHb) and oxygenation levels are detectable using this method since background absorption is suppressed due to the out-of-phase modulation of the laser sources while the difference between the two signals is amplified, thus allowing pre-malignant tumors to become identifiable. By regulating the signal amplitude ratio and phase shift the system can be tuned to applications like cancer screening, sO2 quantification and hypoxia monitoring in stroke patients. Experimental results presented demonstrate WM-DPA imaging of sheep blood phantoms in comparison to single-wavelength FD-PAR imaging. Future work includes the functional PA imaging of small animals in vivo.

  7. Selective ablation of WHHLMI rabbit atherosclerotic plaque by quantum cascade laser in the 5.7 μm wavelength range for less-invasive laser angioplasty

    NASA Astrophysics Data System (ADS)

    Hashimura, Keisuke; Ishii, Katsunori; Akikusa, Naota; Edamura, Tadataka; Yoshida, Harumasa; Awazu, Kunio

    2013-06-01

    We investigated the potential of a compact and high-power quantum cascade laser (QCL) in the 5.7 μm wavelength range for less-invasive laser angioplasty. Atherosclerotic plaques consist mainly of cholesteryl esters. Radiation at a wavelength of 5.75 μm is strongly absorbed in C=O stretching vibration mode of cholesteryl esters. Our previous study achieved to make cutting differences between a normal artery and an atherosclerotic lesions using nanosecond pulsed laser by difference-frequency generation (DFG laser) at the wavelength of 5.75 μm. For applying this technique to clinical treatment, a compact laser device is required. In this study, QCL irradiation effects to a porcine normal aorta were compared with DFG laser. Subsequently, QCL irradiation effects on an atherosclerotic aorta of myocardial infarction-prone Watanabe heritable hyperlipidemic rabbit (WHHLMI rabbit) and a normal rabbit aorta were observed. As a result, the QCL could make cutting differences between the rabbit atherosclerotic and normal aortas. On the other hand, the QCL induced more thermal damage to porcine normal aorta than the DFG laser at the irradiation condition of comparable ablation depths. In conclusion, the possibility of less-invasive and selective treatment of atherosclerotic plaques using the QCL in the 5.7 μm wavelength range was revealed, although improvement of QCL was required to prevent the thermal damage of a normal artery.

  8. Wide range operation of an all-optical NRZ-DPSK-to-RZ-DPSK regenerative waveform-wavelength conversion with flexible width-tunability

    NASA Astrophysics Data System (ADS)

    Ismail, Irneza; Nguyen-The, Quang; Matsuura, Motoharu; Sharif, Gazi Mohammad; Kishi, Naoto

    2015-06-01

    For the first time, we demonstrated a wide range operation of an all-optical non-return-to-zero (NRZ)-differential-phase-shift-keying (DPSK)-to-return-to-zero (RZ)-DPSK waveform-wavelength conversion with flexible picosecond width-tunablity and regenerative functionality. The scheme is based on a Raman amplifier soliton compressor (RASC) and a fiber-based four-wave mixing (FWM) AND-gate. In the first demonstration, we demonstrated waveform-wavelength conversion of a 10-Gb/s DPSK signal without input signal degradation over 54-nm input-output wavelength ranges. The measurement results of the converted RZ-DPSK signal are pedestal-free, and its converted pulse width from 13.0 to 2.87-ps can be adjusted by tuning the Raman pump power between 0.20 and 0.90 W. An investigation of the regenerative waveform-wavelength conversion is further conducted at different Raman pump power settings over 40-km standard single-mode fibers without dispersion compensation. Error-free operation with a low power penalty less than dB is obtained for the RZ-DPSK regenerated converted signal.

  9. Natural variation in the temperature range permissive for vernalization in accessions of Arabidopsis thaliana.

    PubMed

    Wollenberg, Amanda C; Amasino, Richard M

    2012-12-01

    Vernalization is an acceleration of flowering in response to chilling, and is normally studied in the laboratory at near-freezing (2-4 °C) temperatures. Many vernalization-requiring species, such as Arabidopsis thaliana, are found in a range of habitats with varying winter temperatures. Natural variation in the temperature range that elicits a vernalization response in Arabidopsis has not been fully explored. We characterized the effect of intermediate temperatures (7-19 °C) on 15 accessions and the well-studied reference line Col-FRI. Although progressively warmer temperatures are gradually less effective at activating expression of the vernalization-specific gene VERNALIZATION-INSENSITIVE 3 (VIN3) and in accelerating flowering, there is substantial natural variation in the upper threshold (T(max) ) of the flowering-time response. VIN3 is required for the T(max) (13 °C) response of Col-FRI. Surprisingly, even 16 °C treatment caused induction of VIN3 in six tested lines, despite the ineffectiveness of this temperature in accelerating flowering for two of them. Finally, we present evidence that mild acceleration of flowering by 19 °C exposure may counterbalance the flowering time delay caused by non-inductive photoperiods in at least one accession, creating an appearance of photoperiod insensitivity.

  10. Ultrasonic Multiple-Access Ranging System Using Spread Spectrum and MEMS Technology for Indoor Localization

    PubMed Central

    Segers, Laurent; Tiete, Jelmer; Braeken, An; Touhafi, Abdellah

    2014-01-01

    Indoor localization of persons and objects poses a great engineering challenge. Previously developed localization systems demonstrate the use of wideband techniques in ultrasound ranging systems. Direct sequence and frequency hopping spread spectrum ultrasound signals have been proven to achieve a high level of accuracy. A novel ranging method using the frequency hopping spread spectrum with finite impulse response filtering will be investigated and compared against the direct sequence spread spectrum. In the first setup, distances are estimated in a single-access environment, while in the second setup, two senders and one receiver are used. During the experiments, the micro-electromechanical systems are used as ultrasonic sensors, while the senders were implemented using field programmable gate arrays. Results show that in a single-access environment, the direct sequence spread spectrum method offers slightly better accuracy and precision performance compared to the frequency hopping spread spectrum. When two senders are used, measurements point out that the frequency hopping spread spectrum is more robust to near-far effects than the direct sequence spread spectrum. PMID:24553084

  11. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization.

    PubMed

    Segers, Laurent; Van Bavegem, David; De Winne, Sam; Braeken, An; Touhafi, Abdellah; Steenhaut, Kris

    2015-07-30

    This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy.

  12. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization

    PubMed Central

    Segers, Laurent; Van Bavegem, David; De Winne, Sam; Braeken, An; Touhafi, Abdellah; Steenhaut, Kris

    2015-01-01

    This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy. PMID:26263986

  13. Nonlinear properties of dispersion engineered InGaP photonic wire waveguides in the telecommunication wavelength range.

    PubMed

    Dave, Utsav D; Kuyken, Bart; Leo, François; Gorza, Simon-Pierre; Combrie, Sylvain; De Rossi, Alfredo; Raineri, Fabrice; Roelkens, Gunther

    2015-02-23

    We propose high index contrast InGaP photonic wires as a platform for the integration of nonlinear optical functions in the telecom wavelength window. We characterize the linear and nonlinear properties of these waveguide structures. Waveguides with a linear loss of 12 dB/cm and which are coupled to a single mode fiber through gratings with a -7.5 dB coupling loss are realized. From four wave mixing experiments, we extract the real part of the nonlinear parameter γ to be 475 ± 50 W(-1)m(-1) and from nonlinear transmission measurements we infer the absence of two-photon absorption and measure a three-photon absorption coefficient of (2.5 ± 0.5) x 10(-2) cm(3)GW(-2).

  14. Improvement of thermal effects to rabbit atherosclerotic aortas by macro pulse irradiation of a quantum cascade laser in the 5.7 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

    2015-03-01

    Atherosclerotic plaques mainly consist of cholesteryl esters. Cholesteryl esters have an absorption peak at the wavelength of 5.75 μm originated from C=O stretching vibration mode of ester bond. Our group achieved making cutting difference between atherosclerotic lesions and normal vessels using a quantum cascade laser (QCL) in the 5.7 μm wavelength range. QCLs are relatively new types of semiconductor lasers that can emit mid-infrared range. They are sufficiently compact and have recently achieved their high-power emission. However, large thermal damage was observed because the QCL worked as a quasi-continuous wave laser due to its short pulse interval. To realize less invasive ablation by the QCL, reducing thermal effects to normal vessels is needed. In this study, we tried improving the thermal effects by changing the pulse structure. First, irradiation effects to rabbit atherosclerotic aortas by macro pulse irradiation (irradiation of pulses at intervals) and conventional continuous pulse irradiation were compared. The macro pulse width and the macro pulse interval were set to 0.54 and 12 ms, respectively, because the thermal relaxation time of rabbit normal and atherosclerotic aortas in the oscillation wavelength was 0.54-12 ms. As a result, ablation depth became longer and coagulation width became shorter by the macro pulse irradiation. In addition, cutting difference between rabbit normal and atherosclerotic aortas was observed by the macro pulse irradiation. Therefore, the macro pulse irradiation achieved the improvement of thermal effects by the QCL in the 5.7 μm wavelength range. The QCL has the potential of realizing less-invasive laser angioplasty.

  15. Air and silica core Bragg fibers for radiation delivery in the wavelength range 0.6-1.5 μ m

    NASA Astrophysics Data System (ADS)

    Frank, Milan; Jelínek, Michal; Kubeček, Václav; Kašík, Ivan; Podrazký, Ondřej; Matějec, Vlastimil

    2016-09-01

    This paper presents fundamental characteristics of laboratory designed and fabricated Bragg fibers with air and silica cores at wavelengths of 632, 975, 1064 and 1550 nm. Fibers with the 26- μ m-silica core and 5- or 73- μ m-air cores in diameters and claddings of 3 pairs of Bragg layers were prepared from one preform. The overall transmittance, attenuation coefficients, coupling losses, bending losses, and damage-intensity thresholds were determined using four continuous-wave laser sources with the maximum output power of 300 mW and a pulsed 9 ns laser with the maximum output energy up to 1 mJ. The lowest attenuation coefficient of about 70 dB/km was determined at 1064 nm with the 73- μ m-air-core Bragg fiber. All fibers have been found to exhibit negligible bending losses down to the bending diameters of 5 cm. In comparison with the conventional gradient optical fiber, all the prepared Bragg fibers have approximately six times higher damage intensity threshold of about 30 GWcm-2 and therefore they are very suitable for high power laser radiation delivery.

  16. Gas and dust in Comet 2P/Encke observed in the visual and submillimeter wavelength ranges

    NASA Astrophysics Data System (ADS)

    Jockers, K.; Szutowicz, S.; Villanueva, G.; Kiselev, N.; Bonev, T.; Hartogh, P.

    2005-06-01

    In November 2003 Comet 2P/Encke was observed simultaneously with the 10-m Heinrich--Hertz Submillimeter Telescope on Mount Graham, Arizona, USA, and the 2-m optical telescope on Mount Rozhen, Bulgaria. Simultaneous radio observations of the 4--3 and 3--2 rotational transitions of HCN and the 0--0 transition of the CN violet band system provide a three-dimensional view on the comet. The observations are consistent with outgassing from the source region I with location and pole position of Comet Encke taken from [14]. The outflow speed is 1.2 km. There is some evidence for another possible parent for CN besides HCN. The visual dust coma of Comet Encke is nearly spherical with a diameter of about 1000 km and a slight extension into Comet Encke's fan. The polarization of the observed NH2 transition at 662 nm is 7% at a phase angle of 94.5°, close to the value for two-atomic molecules. At this phase angle and a wavelength of 642 nm the polarization of Comet Encke's dust is greater than 30%, i.e., exceeds the value for so-called dusty comets.

  17. Wavelength-resolved optical extinction measurements of aerosols using broad-band cavity-enhanced absorption spectroscopy over the spectral range of 445-480 nm.

    PubMed

    Zhao, Weixiong; Dong, Meili; Chen, Weidong; Gu, Xuejun; Hu, Changjin; Gao, Xiaoming; Huang, Wei; Zhang, Weijun

    2013-02-19

    Despite the significant progress in the measurements of aerosol extinction and absorption using spectroscopy approaches such as cavity ring-down spectroscopy (CRDS) and photoacoustic spectroscopy (PAS), the widely used single-wavelength instruments may suffer from the interferences of gases absorption present in the real environment. A second instrument for simultaneous measurement of absorbing gases is required to characterize the effect of light extinction resulted from gases absorption. We present in this paper the development of a blue light-emitting diode (LED)-based incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) approach for broad-band measurements of wavelength-resolved aerosol extinction over the spectral range of 445-480 nm. This method also allows for simultaneous measurement of trace gases absorption present in the air sample using the same instrument. On the basis of the measured wavelength-dependent aerosol extinction cross section, the real part of the refractive index (RI) can be directly retrieved in a case where the RI does not vary strongly with the wavelength over the relevant spectral region. Laboratory-generated monodispersed aerosols, polystyrene latex spheres (PSL) and ammonium sulfate (AS), were employed for validation of the RI determination by IBBCEAS measurements. On the basis of a Mie scattering model, the real parts of the aerosol RI were retrieved from the measured wavelength-resolved extinction cross sections for both aerosol samples, which are in good agreement with the reported values. The developed IBBCEAS instrument was deployed for simultaneous measurements of aerosol extinction coefficient and NO(2) concentration in ambient air in a suburban site during two representative days. PMID:23320530

  18. Compact fixed wavelength femtosecond oscillators as an add-on for tunable Ti:sapphire lasers extend the range of applications towards multimodal imaging and optogenetics

    NASA Astrophysics Data System (ADS)

    Hakulinen, T.; Klein, J.

    2016-03-01

    Two-photon (2P) microscopy based on tunable Ti:sapphire lasers has become a widespread tool for 3D imaging with sub-cellular resolution in living tissues. In recent years multi-photon microscopy with simpler fixed-wavelength femtosecond oscillators using Yb-doped tungstenates as gain material has raised increasing interest in life-sciences, because these lasers offer one order of magnitude more average power than Ti:sapphire lasers in the wavelength range around 1040 nm: Two-photon (2P) excitation of mainly red or yellow fluorescent dyes and proteins (e.g. YFP, mFruit series) simultaneously has been proven with a single IR laser wavelength. A new approach is to extend the usability of existing tunable Titanium sapphire lasers by adding a fixed IR wavelength with an Yb femtosecond oscillator. By that means a multitude of applications for multimodal imaging and optogenetics can be supported. Furthermore fs Yb-lasers are available with a repetition rate of typically 10 MHz and an average power of typically 5 W resulting in pulse energy of typically 500 nJ, which is comparably high for fs-oscillators. This makes them an ideal tool for two-photon spinning disk laser scanning microscopy and holographic patterning for simultaneous photoactivation of large cell populations. With this work we demonstrate that economical, small-footprint Yb fixed-wavelength lasers can present an interesting add-on to tunable lasers that are commonly used in multiphoton microscopy. The Yb fs-lasers hereby offer higher power for imaging of red fluorescent dyes and proteins, are ideally enhancing existing Ti:sapphire lasers with more power in the IR, and are supporting pulse energy and power hungry applications such as spinning disk microscopy and holographic patterning.

  19. Simultaneous Chemical and Refractive Index Sensing in the 1-2.5 μm Near-Infrared Wavelength Range on Nanoporous Gold Disks.

    PubMed

    Shih, Wei-Chuan; Santos, Greggy M; Zhao, Fusheng; Zenasni, Oussama; Arnob, Md Masud Parvez

    2016-07-13

    Near-infrared (NIR) absorption spectroscopy provides molecular and chemical information based on overtones and combination bands of the fundamental vibrational modes in the infrared wavelengths. However, the sensitivity of NIR absorption measurement is limited by the generally weak absorption and the relatively poor detector performance compared to other wavelength ranges. To overcome these barriers, we have developed a novel technique to simultaneously obtain chemical and refractive index sensing in 1-2.5 μm NIR wavelength range on nanoporous gold (NPG) disks, which feature high-density plasmonic hot-spots of localized electric field enhancement. For the first time, surface-enhanced near-infrared absorption (SENIRA) spectroscopy has been demonstrated for high sensitivity chemical detection. With a self-assembled monolayer (SAM) of octadecanethiol (ODT), an enhancement factor (EF) of up to ∼10(4) has been demonstrated for the first C-H combination band at 2400 nm using NPG disk with 600 nm diameter. Together with localized surface plasmon resonance (LSPR) extinction spectroscopy, simultaneous sensing of sample refractive index has been achieved for the first time. The performance of this technique has been evaluated using various hydrocarbon compounds and crude oil samples.

  20. Optical properties measurement of laser coagulated tissues with double integrating sphere and inverse Monte Carlo technique in the wavelength range from 350 to 2100 nm

    NASA Astrophysics Data System (ADS)

    Honda, Norihiro; Nanjo, Takuya; Ishii, Katsunori; Awazu, Kunio

    2012-03-01

    In laser medicine, the accurate knowledge about the optical properties (absorption coefficient; μa, scattering coefficient; μs, anisotropy factor; g) of laser irradiated tissues is important for the prediction of light propagation in tissues, since the efficacy of laser treatment depends on the photon propagation within the irradiated tissues. Thus, it is likely that the optical properties of tissues at near-ultraviolet, visible and near-infrared wavelengths will be more important due to more biomedical applications of lasers will be developed. For improvement of the laser induced thermotherapy, the optical property change during laser treatment should be considered in the wide wavelength range. For estimation of the optical properties of the biological tissues, the optical properties measurement system with a double integrating sphere setup and an inverse Monte Carlo technique was developed. The optical properties of chicken muscle tissue were measured in the native state and after laser coagulation using the optical properties measurement system in the wavelength range from 350 to 2100 nm. A CO2 laser was used for laser coagulation. After laser coagulation, the reduced scattering coefficient of the tissue increased. And, the optical penetration depth decreased. For improvement of the treatment depth during laser coagulation, a quantitative procedure using the treated tissue optical properties for determination of the irradiation power density following light penetration decrease might be important in clinic.

  1. Frequency-resolved optical gating system with a tellurium crystal for characterizing free-electron lasers in the wavelength range of 10-30 {mu}m

    SciTech Connect

    Iijima, Hokuto; Nagai, Ryoji; Nishimori, Nobuyuki; Hajima, Ryoichi; Minehara, Eisuke J.

    2009-12-15

    A second-harmonic generation frequency-resolved optical gating (SHG-FROG) system has been developed for the complete characterization of laser pulses in the wavelength range of 10-30 {mu}m. A tellurium crystal is used so that spectrally resolved autocorrelation signals with a good signal-to-noise ratio are obtained. Pulses (wavelength {approx}22 {mu}m) generated from a free-electron laser are measured by the SHG-FROG system. The SHG intensity profile and the spectrum obtained by FROG measurements are well consistent with those of independent measurements of the pulse length and spectrum. The pulse duration and spectral width determined from the FROG trace are 0.6 ps and 5.2 THz at full width half maximum, respectively.

  2. Novel wavelength division multiplex-radio over fiber-passive optical network architecture for multiple access points based on multitone generation and triple sextupling frequency

    NASA Astrophysics Data System (ADS)

    Cheng, Guangming; Guo, Banghong; Liu, Songhao; Huang, Xuguang

    2014-01-01

    An innovative wavelength division multiplex-radio over fiber-passive optical network architecture for multiple access points (AP) based on multitone generation and triple sextupling frequency is proposed and demonstrated. A dual-drive Mach-Zehnder modulator (DD-MZM) is utilized to realize the multitone generation. Even sidebands are suppressed to make the adjacent frequency separation twice the frequency of the local oscillator by adjusting the modulation voltage of the DD-MZM. Due to adopting three fiber Bragg gratings to reflect the unmodulated sidebands for uplink communications source free at optical network unit (ONU), is achieved. The system can support at least three APs at one ONU simultaneously with a 30 km single-mode fiber (SMF) transmission and 5 Gb/s data rate both for uplink and downlink communications. The theoretical analysis and simulation results show the architecture has an excellent performance and will be a promising candidate in future hybrid access networks.

  3. Fundamental problems in modern astrophysics requiring access to the ultraviolet range

    NASA Astrophysics Data System (ADS)

    Gómez de Castro, Ana I.; Lecavelier des Étangs, Alain; Reimers, Dieter

    2006-06-01

    Progress of modern astrophysics requires the access to the electromagnetic spectrum in the broadest energy range. The ultraviolet is a fundamental energy domain; warm plasmas at temperatures of 3,000-300,000 K radiate in this range, also the electronic transitions of the most abundant molecules in the Universe are in the UV. Moreover, the UV radiation field is a powerful astrochemical and photoionizing agent. Some of the most relevant problems in modern astrophysical research are related with the properties and abundance of this warm plasma in the Universe, e.g. the chemical enrichment of the Universe, the formation of the galaxies or the contribution of the InterGalactic Medium (IGM) to the total mass of the Universe. Also, this plasma is the primary tracer of some very important processes for the generation of life in our planet like the onset and stabilization of the Solar dynamo or the acceleration of organic chemistry processes in young planetary disks. This contribution represents a brief accounting of the BIG science to be carried out if new UV instrumentation becomes, eventually, available.

  4. Satellite range delay simulator for a matrix-switched time division multiple-access network simulator

    NASA Technical Reports Server (NTRS)

    Nagy, Lawrence A.

    1989-01-01

    The Systems Integration, Test, and Evaluation (SITE) facility at NASA Lewis Research Center is presently configured as a satellite-switched time division multiple access (SS-TDMA) network simulator. The purpose of SITE is to demonstrate and evaluate advanced communication satellite technologies, presently embodied by POC components developed under NASA contracts in addition to other hardware, such as ground terminals, designed and built in-house at NASA Lewis. Each ground terminal in a satellite communications system will experience a different aspect of the satellite's motion due mainly to daily tidal effects and station keeping, hence a different duration and rate of variation in the range delay. As a result of this and other effects such as local oscillator instability, each ground terminal must constantly adjust its transmit burst timing so that data bursts from separate ground terminals arrive at the satellite in their assigned time slots, preventing overlap and keeping the system in synchronism. On the receiving end, ground terminals must synchronize their local clocks using reference transmissions received through the satellite link. A feature of the SITE facility is its capability to simulate the varying propagation delays and associated Doppler frequency shifts that the ground terminals in the network have to cope with. Delay is achieved by means of two NASA Lewis designed and built range delay simulator (RDS) systems, each independently controlled locally with front panel switches or remotely by an experiment control and monitor (EC/M) computer.

  5. Selective ablation of atherosclerotic lesions with less thermal damage by controlling the pulse structure of a quantum cascade laser in the 5.7-µm wavelength range

    NASA Astrophysics Data System (ADS)

    Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

    2016-04-01

    Cholesteryl esters are the main components of atherosclerotic plaques, and they have an absorption peak at the wavelength of 5.75 µm. To realize less-invasive ablation of the atherosclerotic plaques using a quasi-continuous wave (quasi-CW) quantum cascade laser (QCL), the thermal effects on normal vessels must be reduced. In this study, we attempted to reduce the thermal effects by controlling the pulse structure. The irradiation effects on rabbit atherosclerotic aortas using macro pulse irradiation (irradiation of pulses at intervals) and conventional quasi-CW irradiation were compared. The macro pulse width and the macro pulse interval were determined based on the thermal relaxation time of atherosclerotic and normal aortas in the oscillation wavelength of the QCL. The ablation depth increased and the coagulation width decreased using macro pulse irradiation. Moreover, difference in ablation depth between the atherosclerotic and normal rabbit aortas using macro pulse irradiation was confirmed. Therefore, the QCL in the 5.7-µm wavelength range with controlling the pulse structure was effective for less-invasive laser angioplasty.

  6. Spectral Aerosol Extinction (SpEx): A New Instrument for In situ Ambient Aerosol Extinction Measurements Across the UV/Visible Wavelength Range

    NASA Technical Reports Server (NTRS)

    Jordan, C. E.; Anderson, B. E.; Beyersdorf, A. J.; Corr, C. A.; Dibb, J. E.; Greenslade, M. E.; Martin, R. F.; Moore, R. H.; Scheuer, E.; Shook, M. A.; Thornhill, K. L.; Troop, D.; Winstead, Edward L.; Ziemba, L. D.

    2015-01-01

    We introduce a new instrument for the measurement of in situ ambient aerosol extinction over the 300-700 nm wavelength range, the Spectral Aerosol Extinction (SpEx) instrument. This measurement capability is envisioned to complement existing in situ instrumentation, allowing for simultaneous measurement of the evolution of aerosol optical, chemical, and physical characteristics in the ambient environment. In this work, a detailed description of the instrument is provided along with characterization tests performed in the laboratory. Measured spectra of NO2 and polystyrene latex spheres agreed well with theoretical calculations. Good agreement was also found with simultaneous aerosol extinction measurements at 450, 530, and 630 nm using CAPS PMex instruments in a series of 22 tests including non-absorbing compounds, dusts, soot, and black and brown carbon analogs. SpEx can more accurately distinguish the presence of brown carbon from other absorbing aerosol due to its 300 nm lower wavelength limit compared to measurements limited to visible wavelengths. In addition, the spectra obtained by SpEx carry more information than can be conveyed by a simple power law fit that is typically defined by the use of Angstrom Exponents. Future improvements aim at lowering detection limits and ruggedizing the instrument for mobile operation.

  7. Influence of zero dispersion wavelength on supercontinuum generation in near infrared, visible, and UV range for a series of microstructured fibres

    NASA Astrophysics Data System (ADS)

    Holdynski, Z.; Napierala, M.; Szymanski, M.; Murawski, M.; Mergo, P.; Marc, P.; Jaroszewicz, L. R.; Nasilowski, T.

    2014-03-01

    Nonlinear phenomena in microstructured fibers (MSFs) is defined by dispersive properties of a fiber. Zero dispersion wavelength (ZDW) and pump source wavelength play an important role in estimating the nonlinear effects and thus are subject of wide investigations. Multiple nonlinear processes like: four wave mixing (FWM), cross phase modulation (XPM), cannot be very efficient without phase matching which is achieved when a fiber is pumped in anomalous dispersion region. On the other hand, other nonlinear processes, such as self-phase modulation (SPM) and Raman scattering (RS), profit from pumping fiber in normal dispersion region. Thus the efficiency of supercontinuum (SC) generation in a fiber is dependent on its chromatic dispersion properties, which can be tailored by the proper fiber geometry design, and by the pump source wavelength. In our paper we present experimental analysis of SC generation obtained for a series of nonlinear MSFs. Our fibers have different ZDW and therefore when pumped by the same pump source, different nonlinear effects contribute to the SC generation. We analyze and explain the influence of ZDW on nonlinear effects. Comparisons of nonlinear interactions for fibers pumped in anomalous and normal dispersion regimes are provided. In our silica MSFs an ultra-short UV radiation was obtained by nonlinear processes estimation. We provide experimental analysis of MSFs geometrical parameters influence on UV conversion efficiency. Our studies present effective SC generation in near infrared, visible and UV ranges. Unique information about the influence of MSFs geometry on UV generation efficiency gives possibility to increase its application potential.

  8. The spectral opacity of triatomic carbon measured in a graphite tube furnace over the 280 to 600 nm wavelength range

    NASA Technical Reports Server (NTRS)

    Snow, W. L.; Wells, W. L.

    1980-01-01

    The opacity of linear triatomic carbon (C3) was measured in a graphite tube furnace from 280 to 600 nm to supplement the earlier measurements of Brewer and Engelke. The spectral cross section was estimated from the opacities using temperature profiles determined pyrometrically and a revised heat of formation delta H = 198 kcal/mole). The cross section was found to be nonnegligible over the range 300 to 500 nm and the electronic oscillator strength based on the total cross section estimate was 0.02.

  9. Photonic crystal fiber with a dual-frequency addressable liquid crystal: behavior in the visible wavelength range.

    PubMed

    Lorenz, A; Kitzerow, H-S; Schwuchow, A; Kobelke, J; Bartelt, H

    2008-11-10

    Wave-guiding in the visible spectral range is investigated for a micro-structured crystal fiber filled with a dual-frequency addressable nematic liquid crystal mixture. The fiber exhibits a solid core surrounded by just 4 rings of cylindrical holes. Control of the liquid crystal alignment by anchoring agents permits relatively low attenuation. Samples with different anchoring conditions at the interface of the silica glass and the liquid crystal show different transmission properties and switching behavior. Polarization dependent and independent fiber optic switching is observed. Due to a dualfrequency addressing scheme, active switching to both states with enhanced and reduced transmission becomes possible for planar anchoring. Even a non-perfect fiber shows reasonable transmission and a variety of interesting effects.

  10. Extended femtosecond laser wavelength range to 330 nm in a high power LBO based optical parametric oscillator.

    PubMed

    Fan, Jintao; Gu, Chenglin; Wang, Chingyue; Hu, Minglie

    2016-06-13

    We experimentally demonstrate a compact tunable, high average power femtosecond laser source in the ultraviolet (UV) regime. The laser source is based on intra-cavity frequency doubling of a temperature-tuned lithium tribotate (LBO) optical parametric oscillator (OPO), synchronously pumped at 520 nm by a frequency-doubled, Yb-fiber femtosecond laser amplifier system. By adjusting crystal temperature, the OPO can provide tunable visible to near-infrared (NIR) signal pulse, which have a wide spectral tuning range from 660 to 884 nm. Using a β-barium borate (BBO) crystal for intra-cavity frequency doubling, tunable femtosecond UV pulse are generated across 330~442 nm with up to 364 mW at 402 nm.

  11. Photonic crystal fiber with a dual-frequency addressable liquid crystal: behavior in the visible wavelength range.

    PubMed

    Lorenz, A; Kitzerow, H-S; Schwuchow, A; Kobelke, J; Bartelt, H

    2008-11-10

    Wave-guiding in the visible spectral range is investigated for a micro-structured crystal fiber filled with a dual-frequency addressable nematic liquid crystal mixture. The fiber exhibits a solid core surrounded by just 4 rings of cylindrical holes. Control of the liquid crystal alignment by anchoring agents permits relatively low attenuation. Samples with different anchoring conditions at the interface of the silica glass and the liquid crystal show different transmission properties and switching behavior. Polarization dependent and independent fiber optic switching is observed. Due to a dualfrequency addressing scheme, active switching to both states with enhanced and reduced transmission becomes possible for planar anchoring. Even a non-perfect fiber shows reasonable transmission and a variety of interesting effects. PMID:19582031

  12. Extended femtosecond laser wavelength range to 330 nm in a high power LBO based optical parametric oscillator.

    PubMed

    Fan, Jintao; Gu, Chenglin; Wang, Chingyue; Hu, Minglie

    2016-06-13

    We experimentally demonstrate a compact tunable, high average power femtosecond laser source in the ultraviolet (UV) regime. The laser source is based on intra-cavity frequency doubling of a temperature-tuned lithium tribotate (LBO) optical parametric oscillator (OPO), synchronously pumped at 520 nm by a frequency-doubled, Yb-fiber femtosecond laser amplifier system. By adjusting crystal temperature, the OPO can provide tunable visible to near-infrared (NIR) signal pulse, which have a wide spectral tuning range from 660 to 884 nm. Using a β-barium borate (BBO) crystal for intra-cavity frequency doubling, tunable femtosecond UV pulse are generated across 330~442 nm with up to 364 mW at 402 nm. PMID:27410342

  13. Space-resolved extreme ultraviolet spectroscopy free of high-energy neutral particle noise in wavelength range of 10–130 Å on the large helical device

    SciTech Connect

    Huang, Xianli; Morita, Shigeru; Oishi, Tetsutarou; Goto, Motoshi; Dong, Chunfeng

    2014-04-15

    A flat-field space-resolved extreme ultraviolet (EUV) spectrometer system working in wavelength range of 10–130 Å has been constructed in the Large Helical Device (LHD) for profile measurements of bremsstrahlung continuum and line emissions of heavy impurities in the central column of plasmas, which are aimed at studies on Z{sub eff} and impurity transport, respectively. Until now, a large amount of spike noise caused by neutral particles with high energies (≤180 keV) originating in neutral beam injection has been observed in EUV spectroscopy on LHD. The new system has been developed with an aim to delete such a spike noise from the signal by installing a thin filter which can block the high-energy neutral particles entering the EUV spectrometer. Three filters of 11 μm thick beryllium (Be), 3.3 μm thick polypropylene (PP), and 0.5 μm thick polyethylene terephthalate (PET: polyester) have been examined to eliminate the spike noise. Although the 11 μm Be and 3.3 μm PP filters can fully delete the spike noise in wavelength range of λ ≤ 20 Å, the signal intensity is also reduced. The 0.5 μm PET filter, on the other hand, can maintain sufficient signal intensity for the measurement and the spike noise remained in the signal is acceptable. As a result, the bremsstrahlung profile is successfully measured without noise at 20 Å even in low-density discharges, e.g., 2.9 × 10{sup 13} cm{sup −3}, when the 0.5 μm PET filter is used. The iron n = 3–2 Lα transition array consisting of FeXVII to FeXXIV is also excellently observed with their radial profiles in wavelength range of 10–18 Å. Each transition in the Lα array can be accurately identified with its radial profile. As a typical example of the method a spectral line at 17.62 Å is identified as FeXVIII transition. Results on absolute intensity calibration of the spectrometer system, pulse height and noise count analyses of the spike noise between holographic and ruled gratings and wavelength

  14. Space-resolved extreme ultraviolet spectroscopy free of high-energy neutral particle noise in wavelength range of 10-130 Å on the large helical device.

    PubMed

    Huang, Xianli; Morita, Shigeru; Oishi, Tetsutarou; Goto, Motoshi; Dong, Chunfeng

    2014-04-01

    A flat-field space-resolved extreme ultraviolet (EUV) spectrometer system working in wavelength range of 10-130 Å has been constructed in the Large Helical Device (LHD) for profile measurements of bremsstrahlung continuum and line emissions of heavy impurities in the central column of plasmas, which are aimed at studies on Zeff and impurity transport, respectively. Until now, a large amount of spike noise caused by neutral particles with high energies (≤180 keV) originating in neutral beam injection has been observed in EUV spectroscopy on LHD. The new system has been developed with an aim to delete such a spike noise from the signal by installing a thin filter which can block the high-energy neutral particles entering the EUV spectrometer. Three filters of 11 μm thick beryllium (Be), 3.3 μm thick polypropylene (PP), and 0.5 μm thick polyethylene terephthalate (PET: polyester) have been examined to eliminate the spike noise. Although the 11 μm Be and 3.3 μm PP filters can fully delete the spike noise in wavelength range of λ ≤ 20 Å, the signal intensity is also reduced. The 0.5 μm PET filter, on the other hand, can maintain sufficient signal intensity for the measurement and the spike noise remained in the signal is acceptable. As a result, the bremsstrahlung profile is successfully measured without noise at 20 Å even in low-density discharges, e.g., 2.9 × 10(13) cm(-3), when the 0.5 μm PET filter is used. The iron n = 3-2 Lα transition array consisting of FeXVII to FeXXIV is also excellently observed with their radial profiles in wavelength range of 10-18 Å. Each transition in the Lα array can be accurately identified with its radial profile. As a typical example of the method a spectral line at 17.62 Å is identified as FeXVIII transition. Results on absolute intensity calibration of the spectrometer system, pulse height and noise count analyses of the spike noise between holographic and ruled gratings and wavelength response of the used

  15. Recent Development of Sb-based Phototransistors in the 0.9- to 2.2-microns Wavelength Range for Applications to Laser Remote Sensing

    NASA Technical Reports Server (NTRS)

    Abedin, M. Nurul; Refaat, Tamer F.; Sulima, Oleg V.; Singh, Upendra N.

    2006-01-01

    We have investigated commercially available photodiodes and also recent developed Sb-based phototransistors in order to compare their performances for applications to laser remote sensing. A custom-designed phototransistor in the 0.9- to 2.2-microns wavelength range has been developed at AstroPower and characterized at NASA Langley's Detector Characterization Laboratory. The phototransistor's performance greatly exceeds the previously reported results at this wavelength range in the literature. The detector testing included spectral response, dark current and noise measurements. Spectral response measurements were carried out to determine the responsivity at 2-microns wavelength at different bias voltages with fixed temperature; and different temperatures with fixed bias voltage. Current versus voltage characteristics were also recorded at different temperatures. Results show high responsivity of 2650 A/W corresponding to an internal gain of three orders of magnitude, and high detectivity (D*) of 3.9x10(exp 11) cm.Hz(exp 1/2)/W that is equivalent to a noise-equivalent-power of 4.6x10(exp -14) W/Hz(exp 1/2) (-4.0 V @ -20 C) with a light collecting area diameter of 200-microns. It appears that this recently developed 2-micron phototransistor's performances such as responsivity, detectivity, and gain are improved significantly as compared to the previously published APD and SAM APD using similar materials. These detectors are considered as phototransistors based-on their structures and performance characteristics and may have great potential for high sensitivity differential absorption lidar (DIAL) measurements of carbon dioxide and water vapor at 2.05-microns and 1.9-microns, respectively.

  16. Influence of polymer packaging films on hyperspectral imaging data in the visible-near-infrared (450-950 nm) wavelength range.

    PubMed

    Gowen, A A; O'Donnell, C P; Esquerre, C; Downey, G

    2010-03-01

    Hyperspectral imaging (HSI) has recently emerged as a useful tool for quality analysis of consumer goods (e.g., food and pharmaceutical products). These products are typically packaged in polymeric film prior to distribution; however, HSI experiments are typically carried out on such samples ex-packaging (either prior to or after removal from packaging). This research examines the effects of polymer packaging films (polyvinyl chloride (PVC) and polyethylene terephthalate (PET)) on spectral and spatial features of HSI data in order to investigate the potential of HSI for quality evaluation of packaged goods. The effects of packaging film were studied for hyperspectral images of samples obtained in the visible-near-infrared (Vis-NIR, i.e., 450-950 nm) wavelength range, which is relevant to many food, agricultural, and pharmaceutical products. The dominant influence of the films tested in this wavelength range could be attributed to light scattering. Relative position of the light source, film, and detector were shown to be highly influential on the scattering effects observed. Detection of features on samples imaged through film was shown to be possible after some data preprocessing. This suggests that quality analysis of products packaged in polymer film is feasible using HSI. These findings would be useful in the development of quality monitoring tools for consumer products post-packaging using HSI.

  17. Low threshold lasing of bubble-containing glass microspheres by non-whispering gallery mode excitation over a wide wavelength range

    SciTech Connect

    Kumagai, Tsutaru Kishi, Tetsuo; Yano, Tetsuji

    2015-03-21

    Bubble-containing Nd{sup 3+}-doped tellurite glass microspheres were fabricated by localized laser heating technique to investigate their optical properties for use as microresonators. Fluorescence and excitation spectra measurements were performed by pumping with a tunable CW-Ti:Sapphire laser. The excitation spectra manifested several sharp peaks due to the conventional whispering gallery mode (WGM) when the pumping laser was irradiated to the edge part of the microsphere. However, when the excitation light was irradiated on the bubble position inside the microsphere, “non-WGM excitation” was induced, giving rise to numerous peaks at a broad wavelength range in the excitation spectra. Thus, efficient excitation was achieved over a wide wavelength range. Lasing threshold excited at the bubble position was much lower than that for the excitation at the edges of the microsphere. The lowest value of the laser threshold was 34 μW for a 4 μm sphere containing a 0.5 μm bubble. Efficiency of the excitation at the bubble position with broadband light was calculated to be 5 times higher than that for the edge of the microsphere. The bubble-containing microsphere enables efficient utilization of broadband light excitation from light-emitting diodes and solar light.

  18. Review of an assortment of IR materials-devices technologies used for imaging in spectral bands ranging from the visible to very long wavelengths

    NASA Astrophysics Data System (ADS)

    DeWames, Roger E.

    2016-05-01

    In this paper we review the intrinsic and extrinsic technological properties of the incumbent technology, InP/In0.53Ga0.47As/InP, for imaging in the visible- short wavelength spectral band, InSb and HgCdTe for imaging in the mid-wavelength spectral band and HgCdTe for imaging in the long wavelength spectral band. These material systems are in use for a wide range of applications addressing compelling needs in night vision imaging, low light level astronomical applications and defense strategic satellite sensing. These materials systems are direct band gap energy semiconductors hence the internal quantum efficiency η, is near unity over a wide spectral band pass. A key system figure of merit of a shot noise limited detector technology is given by the equation (1+Jdark. /Jphoton), where Jdark is the dark current density and Jphoton ~qηΦ is the photocurrent density; Φ is the photon flux incident on the detector and q is the electronic charge. The capability to maintain this factor for a specific spectral band close to unity for low illumination conditions and low temperature onset of non-ideal dark current components, basically intrinsic diffusion limited performance all the way, is a marker of quality and versatility of a semiconductor detector technology. It also enables the highest temperature of operation for tactical illumination conditions. A purpose of the work reported in this paper is to explore the focal plane array data sets of photodiode detector technologies widely used to bench mark their fundamental and technology properties and identify paths for improvements.

  19. Ultrahigh wavelength range (300nm-2μm) polarization-independent 500gs/s single-shot pulse, all-optical real time oscilloscope

    NASA Astrophysics Data System (ADS)

    Gleyze, Jean-François; Hocquet, Steve; Monnier Bourdin, Dominique; Le Boudec, Patrice; Arnaud, Romain; Chassagne, Bruno; Jolly, Alain; Penninckx, Denis

    2014-03-01

    The development of ultra-broadband oscilloscopes is mainly governed by the needs of future telecom networks. But other applications are requesting the availability of true real-time acquisition oscilloscopes. Systems able to be used in single-shot operation are of prime interest for Inertial Confinement Fusion (ICF) and for the related R&D for plasma physics. We previously demonstrate a single-shot, 100GHz design of an all-optical sampling oscilloscope at 1μm (MULO). This laboratory system has been improved in stability and compactness to make an all-in-one box prototype. More, by the addition of an opto-electro-optics (OEO) sub-system at the input, we developed the ability to use this oscilloscope to analyze an electrical input signal up to 60GHz. This new integrated subset also increases the range of wavelength for optical input signal, from 300nm up to 2μm. Furthermore, it allows the use of inexpensive opto-electronic components at telecom wavelength for this system regardless of the signal to be analysed. In parallel with these improvements, by optimizing the heart of the system, we get a very high sampling rate, up to 500Gs/s and more; this allows considering much higher bandwidths in the future. In this talk, we will present latest developments and integration of this system. It will also allow us to give more details on the innovative OEO sub-system.

  20. MEMS Fabry-Perot interferometer-based spectrometer demonstrator for 7.5 μm to 9.5 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Mäkynen, Jussi H.; Tuohiniemi, Mikko; Näsilä, Antti; Mannila, Rami; Antila, Jarkko E.

    2014-03-01

    VTT Technical research centre of Finland has developed a MEMS Fabry-Perot interferometer (FPI) for the wavelength range from 7.5 μm to 9.5 μm. The device consists of two Distributed Bragg Reflectors (DBR) manufactured with MEMS processing techniques. The full width half maximum of the transmission peak is 150nm. This transmission peak can be tuned from 7.5 μm to 9.5 μm by applying a control voltage from 0 V to 30 V. A laboratory demonstrator has been put together to show the use of this module as a part of a spectral measurement setup. Several gas samples have been measured with the setup and compared against measurement results found in literature.

  1. 5000 groove/mm multilayer-coated blazed grating with 33percent efficiency in the 3rd order in the EUV wavelength range

    SciTech Connect

    Advanced Light Source; Voronov, Dmitriy L.; Anderson, Erik; Cambie, Rossana; Salmassi, Farhad; Gullikson, Eric; Yashchuk, Valeriy; Padmore, Howard; Ahn, Minseung; Chang, Chih-Hao; Heilmann, Ralf; Schattenburg, Mark

    2009-07-07

    We report on recent progress in developing diffraction gratings which can potentially provide extremely high spectral resolution of 105-106 in the EUV and soft x-ray photon energy ranges. Such a grating was fabricated by deposition of a multilayer on a substrate which consists ofa 6-degree blazed grating with a high groove density. The fabrication of the substrate gratings was based on scanning interference lithography and anisotropic wet etch of silicon single crystals. The optimized fabrication process provided precise control of the grating periodicity, and the grating groove profile, together with very short anti-blazed facets, and near atomically smooth surface blazed facets. The blazed grating coated with 20 Mo/Si bilayers demonstrated a diffraction efficiency in the third order as high as 33percent at an incidence angle of 11? and wavelength of 14.18 nm.

  2. High-Sensitivity InAsSb Photoconductors with a Response Wavelength Range of 2-9 μm Operated at Room Temperature

    NASA Astrophysics Data System (ADS)

    Gao, Yu Zhu; Gong, Xiu Ying; Fang, Wei Zheng; Wu, Guang Hui; Feng, Yan Bin

    2009-08-01

    InAsSb immersion photoconductors with a response wavelength range of 2-9 μm operated at room temperature were reported. The detectors are based on InAsSb single crystals grown on InAs substrates by melt epitaxy (ME). Van der Pauw measurements showed that the 300 K electron mobilities of InAsSb materials are higher than 5× 104 cm2 V-1 s-1 with carrier densities of (1--3)× 1016 cm-3. The photoconductors were measured using a standard blackbody source at a temperature of 500 K and a modulation frequency of 800 Hz under an applied bias current of 10 mA. At 293 K, the blackbody detectivity Dbb{}* (500 K, 800) reaches (2--6)× 108 cm Hz1/2 W-1, indicating the high sensitivity of the detectors and their potential detection applications.

  3. Determination of Seed Soundness in Conifers Cryptomeria japonica and Chamaecyparis obtusa Using Narrow-Multiband Spectral Imaging in the Short-Wavelength Infrared Range.

    PubMed

    Matsuda, Osamu; Hara, Masashi; Tobita, Hiroyuki; Yazaki, Kenichi; Nakagawa, Toshinori; Shimizu, Kuniyoshi; Uemura, Akira; Utsugi, Hajime

    2015-01-01

    Regeneration of planted forests of Cryptomeria japonica (sugi) and Chamaecyparis obtuse (hinoki) is the pressing importance to the forest administration in Japan. Low seed germination rate of these species, however, has hampered low-cost production of their seedlings for reforestation. The primary cause of the low germinability has been attributed to highly frequent formation of anatomically unsound seeds, which are indistinguishable from sound germinable seeds by visible observation and other common criteria such as size and weight. To establish a method for sound seed selection in these species, hyperspectral imaging technique was used to identify a wavelength range where reflectance spectra differ clearly between sound and unsound seeds. In sound seeds of both species, reflectance in a narrow waveband centered at 1,730 nm, corresponding to a lipid absorption band in the short-wavelength infrared (SWIR) range, was greatly depressed relative to that in adjacent wavebands on either side. Such depression was absent or less prominent in unsound seeds. Based on these observations, a reflectance index SQI, abbreviated for seed quality index, was formulated using reflectance at three narrow SWIR wavebands so that it represents the extent of the depression. SQI calculated from seed area-averaged reflectance spectra and spatial distribution patterns of pixelwise SQI within each seed area were both proven as reliable criteria for sound seed selection. Enrichment of sound seeds was accompanied by an increase in germination rate of the seed lot. Thus, the methods described are readily applicable toward low-cost seedling production in combination with single seed sowing technology. PMID:26083366

  4. Performance of asynchronous fiber-optic code division multiple access system based on three-dimensional wavelength/time/space codes and its link analysis.

    PubMed

    Singh, Jaswinder

    2010-03-10

    A novel family of three-dimensional (3-D) wavelength/time/space codes for asynchronous optical code-division-multiple-access (CDMA) systems with "zero" off-peak autocorrelation and "unity" cross correlation is reported. Antipodal signaling and differential detection is employed in the system. A maximum of [(W x T+1) x W] codes are generated for unity cross correlation, where W and T are the number of wavelengths and time chips used in the code and are prime. The conditions for violation of the cross-correlation constraint are discussed. The expressions for number of generated codes are determined for various code dimensions. It is found that the maximum number of codes are generated for S < or = min(W,T), where W and T are prime and S is the number of space channels. The performance of these codes is compared to the earlier reported two-dimensional (2-D)/3-D codes for asynchronous systems. The codes have a code-set-size to code-size ratio greater than W/S. For instance, with a code size of 2065 (59 x 7 x 5), a total of 12,213 users can be supported, and 130 simultaneous users at a bit-error rate (BER) of 10(-9). An arrayed-waveguide-grating-based reconfigurable encoder/decoder design for 2-D implementation for the 3-D codes is presented so that the need for multiple star couplers and fiber ribbons is eliminated. The hardware requirements of the coders used for various modulation/detection schemes are given. The effect of insertion loss in the coders is shown to be significantly reduced with loss compensation by using an amplifier after encoding. An optical CDMA system for four users is simulated and the results presented show the improvement in performance with the use of loss compensation.

  5. Sensitivity of spectral reflectance to aerosol optical properties in UV and visible wavelength range: Preparatory study for aerosol retrieval from Geostationary Environmental Monitoring Spectrometer (GEMS)

    NASA Astrophysics Data System (ADS)

    KIM, M.; Kim, J.; Lee, J.

    2011-12-01

    Asia, with its rapid increase in industrialization and population, has been receiving great attention as one of important source regions of pollutants including aerosols and trace gases. Since the spatio-temporal distribution of the pollutants varies rapidly, demands to monitor air quality in a geostationary satellite have increased recently. In these perspectives, the Ministry of Environment of Korea initiated a geostationary satellite mission to launch the Geostationary Environmental Monitoring Spectrometer (GEMS) onboard the GEO-KOMPSAT in 2017-2018 timeframe. From the Ozone Monitoring Instrument (OMI) measurements, it has been found that the low surface reflectance and strong interaction between aerosol absorption and molecular scattering in UV wavelength range can be advantageous in retrieving aerosol optical properties, such as aerosol optical thickness (AOT) and optical type (or single scattering albedo), over the source regions as well as ocean areas. In addition, GEMS is expected to have finer spatial resolution compared to OMI (13 x 24 km2 at nadir), thereby less affected by sub-pixel clouds. In this study, we present sensitivity of spectral reflectance to aerosol optical properties in ultraviolet (UV) and visible wavelength range for a purpose to retrieve aerosol optical properties from GEMS. The so called UV-VIS algorithm plans to use spectral reflectance in 350-650 nm. The algorithm retrieves AOT and aerosol type using an inversion method, which adopts pre-calculated lookup table (LUT) for a set of assumed aerosol models. For the aerosol models optimized in Asia areas, the inversion data of Aerosol Robotic Network (AERONET) located in the target areas are selectively used to archive aerosol optical properties. As a result, major aerosol types representing dust, polluted dust, and absorbing/non-absorbing anthropogenic aerosols are constructed and used for the LUT calculations. We analyze the effect of cloud contamination on the retrieved AOT by

  6. Mitigating Phototoxicity during Multiphoton Microscopy of Live Drosophila Embryos in the 1.0–1.2 µm Wavelength Range

    PubMed Central

    Débarre, Delphine; Olivier, Nicolas; Supatto, Willy; Beaurepaire, Emmanuel

    2014-01-01

    Light-induced toxicity is a fundamental bottleneck in microscopic imaging of live embryos. In this article, after a review of photodamage mechanisms in cells and tissues, we assess photo-perturbation under illumination conditions relevant for point-scanning multiphoton imaging of live Drosophila embryos. We use third-harmonic generation (THG) imaging of developmental processes in embryos excited by pulsed near-infrared light in the 1.0–1.2 µm range. We study the influence of imaging rate, wavelength, and pulse duration on the short-term and long-term perturbation of development and define criteria for safe imaging. We show that under illumination conditions typical for multiphoton imaging, photodamage in this system arises through 2- and/or 3-photon absorption processes and in a cumulative manner. Based on this analysis, we derive general guidelines for improving the signal-to-damage ratio in two-photon (2PEF/SHG) or THG imaging by adjusting the pulse duration and/or the imaging rate. Finally, we report label-free time-lapse 3D THG imaging of gastrulating Drosophila embryos with sampling appropriate for the visualisation of morphogenetic movements in wild-type and mutant embryos, and long-term multiharmonic (THG-SHG) imaging of development until hatching. PMID:25111506

  7. The non-contact detection and identification of blood stained fingerprints using visible wavelength hyperspectral imaging: Part II effectiveness on a range of substrates.

    PubMed

    Cadd, Samuel; Li, Bo; Beveridge, Peter; O'Hare, William T; Campbell, Andrew; Islam, Meez

    2016-05-01

    Biological samples, such as blood, are regularly encountered at violent crime scenes and successful identification is critical for criminal investigations. Blood is one of the most commonly encountered fingerprint contaminants and current identification methods involve presumptive tests or wet chemical enhancement. These are destructive however; can affect subsequent DNA sampling; and do not confirm the presence of blood, meaning they are susceptible to false positives. A novel application of visible wavelength reflectance hyperspectral imaging (HSI) has been used for the non-contact, non-destructive detection and identification of blood stained fingerprints across a range of coloured substrates of varying porosities. The identification of blood was based on the Soret γ band absorption of haemoglobin between 400 nm and 500 nm. Ridge detail was successfully visualised to the third depletion across light coloured substrates and the stain detected to the tenth depletion on both porous and non-porous substrates. A higher resolution setup for blood stained fingerprints on black tiles, detected ridge detail to the third depletion and the stain to the tenth depletion, demonstrating considerable advancements from previous work. Diluted blood stains at 1500 and 1000 fold dilutions for wet and dry stains respectively were also detected on pig skin as a replica for human skin.

  8. Light harvesting over a wide range of wavelength using natural dyes of gardenia and cochineal for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Park, Kyung-Hee; Kim, Tae-Young; Han, Shin; Ko, Hyun-Seok; Lee, Suk-Ho; Song, Yong-Min; Kim, Jung-Hun; Lee, Jae-Wook

    2014-07-01

    Two natural dyes extracted from gardenia yellow (Gardenia jasminoides) and cochineal (Dactylopius coccus) were used as sensitizers in the assembly of dye-sensitized solar cells (DSSCs) to harvest light over a wide range of wavelengths. The adsorption characteristics, electrochemical properties and photovoltaic efficiencies of the natural DSSCs were investigated. The adsorption kinetics data of the dyes were obtained in a small adsorption chamber and fitted with a pseudo-second-order model. The photovoltaic performance of a photo-electrode adsorbed with single-dye (gardenia or cochineal) or the mixture or successive adsorption of the two dyes, was evaluated from current-voltage measurements. The energy conversion efficiency of the TiO2 electrode with the successive adsorption of cochineal and gardenia dyes was 0.48%, which was enhanced compared to single-dye adsorption. Overall, a double layer of the two natural dyes as sensitizers was successfully formulated on the nanoporous TiO2 surface based on the differences in their adsorption affinities of gardenia and cochineal.

  9. Light harvesting over a wide range of wavelength using natural dyes of gardenia and cochineal for dye-sensitized solar cells.

    PubMed

    Park, Kyung-Hee; Kim, Tae-Young; Han, Shin; Ko, Hyun-Seok; Lee, Suk-Ho; Song, Yong-Min; Kim, Jung-Hun; Lee, Jae-Wook

    2014-07-15

    Two natural dyes extracted from gardenia yellow (Gardenia jasminoides) and cochineal (Dactylopius coccus) were used as sensitizers in the assembly of dye-sensitized solar cells (DSSCs) to harvest light over a wide range of wavelengths. The adsorption characteristics, electrochemical properties and photovoltaic efficiencies of the natural DSSCs were investigated. The adsorption kinetics data of the dyes were obtained in a small adsorption chamber and fitted with a pseudo-second-order model. The photovoltaic performance of a photo-electrode adsorbed with single-dye (gardenia or cochineal) or the mixture or successive adsorption of the two dyes, was evaluated from current-voltage measurements. The energy conversion efficiency of the TiO2 electrode with the successive adsorption of cochineal and gardenia dyes was 0.48%, which was enhanced compared to single-dye adsorption. Overall, a double layer of the two natural dyes as sensitizers was successfully formulated on the nanoporous TiO2 surface based on the differences in their adsorption affinities of gardenia and cochineal. PMID:24709352

  10. The non-contact detection and identification of blood stained fingerprints using visible wavelength hyperspectral imaging: Part II effectiveness on a range of substrates.

    PubMed

    Cadd, Samuel; Li, Bo; Beveridge, Peter; O'Hare, William T; Campbell, Andrew; Islam, Meez

    2016-05-01

    Biological samples, such as blood, are regularly encountered at violent crime scenes and successful identification is critical for criminal investigations. Blood is one of the most commonly encountered fingerprint contaminants and current identification methods involve presumptive tests or wet chemical enhancement. These are destructive however; can affect subsequent DNA sampling; and do not confirm the presence of blood, meaning they are susceptible to false positives. A novel application of visible wavelength reflectance hyperspectral imaging (HSI) has been used for the non-contact, non-destructive detection and identification of blood stained fingerprints across a range of coloured substrates of varying porosities. The identification of blood was based on the Soret γ band absorption of haemoglobin between 400 nm and 500 nm. Ridge detail was successfully visualised to the third depletion across light coloured substrates and the stain detected to the tenth depletion on both porous and non-porous substrates. A higher resolution setup for blood stained fingerprints on black tiles, detected ridge detail to the third depletion and the stain to the tenth depletion, demonstrating considerable advancements from previous work. Diluted blood stains at 1500 and 1000 fold dilutions for wet and dry stains respectively were also detected on pig skin as a replica for human skin. PMID:27162017

  11. Effects of body size and home range on access to mates and paternity in male bridled nailtail wallabies.

    PubMed

    Fisher; Lara

    1999-07-01

    The bridled nailtail wallaby, Onychogalea fraenata, is a relatively small, solitary and sexually size dimorphic macropod. We studied the mating system of free-ranging wallabies over 3 years, using microsatellite analysis of paternity, radiotelemetry and behavioural observations. Both sexes were promiscuous, and general reproductive behaviour was similar to that of larger, better-known macropods. Home range size influenced the number of associations with oestrous females, and was a significant component of male reproductive success. Female population density varied within the site, but males with home ranges that overlapped more females did not sire more offspring. Aggression between males occurred only around oestrous females and males did not establish a predetermined dominance hierarchy. Male body weight strongly influenced priority of access to oestrous females, and was related to age. The number of times that males were seen closest to an oestrous female when other males were present (priority of access) was the most important predictor of variation in the number of offspring sired. Females mated with several males within and between oestrous cycles, and may have influenced male-male competition by prolonging advertisement of approaching oestrus, expanding their home ranges at oestrus and engaging in mate chases that attracted groups of up to six males. Despite overall similarities in the mating system of this species and that of other macropods, male mating success may be less skewed in bridled nailtail wallabies than in other species, although paternity analysis of free-ranging populations of other species is required to confirm this conclusion. Copyright 1999 The Association for the Study of Animal Behaviour. PMID:10413548

  12. An objective approach to determining the weight ranges of prey preferred by and accessible to the five large African carnivores.

    PubMed

    Clements, Hayley S; Tambling, Craig J; Hayward, Matt W; Kerley, Graham I H

    2014-01-01

    Broad-scale models describing predator prey preferences serve as useful departure points for understanding predator-prey interactions at finer scales. Previous analyses used a subjective approach to identify prey weight preferences of the five large African carnivores, hence their accuracy is questionable. This study uses a segmented model of prey weight versus prey preference to objectively quantify the prey weight preferences of the five large African carnivores. Based on simulations of known predator prey preference, for prey species sample sizes above 32 the segmented model approach detects up to four known changes in prey weight preference (represented by model break-points) with high rates of detection (75% to 100% of simulations, depending on number of break-points) and accuracy (within 1.3±4.0 to 2.7±4.4 of known break-point). When applied to the five large African carnivores, using carnivore diet information from across Africa, the model detected weight ranges of prey that are preferred, killed relative to their abundance, and avoided by each carnivore. Prey in the weight ranges preferred and killed relative to their abundance are together termed "accessible prey". Accessible prey weight ranges were found to be 14-135 kg for cheetah Acinonyx jubatus, 1-45 kg for leopard Panthera pardus, 32-632 kg for lion Panthera leo, 15-1600 kg for spotted hyaena Crocuta crocuta and 10-289 kg for wild dog Lycaon pictus. An assessment of carnivore diets throughout Africa found these accessible prey weight ranges include 88±2% (cheetah), 82±3% (leopard), 81±2% (lion), 97±2% (spotted hyaena) and 96±2% (wild dog) of kills. These descriptions of prey weight preferences therefore contribute to our understanding of the diet spectrum of the five large African carnivores. Where datasets meet the minimum sample size requirements, the segmented model approach provides a means of determining, and comparing, the prey weight range preferences of any carnivore species. PMID

  13. An Objective Approach to Determining the Weight Ranges of Prey Preferred by and Accessible to the Five Large African Carnivores

    PubMed Central

    Clements, Hayley S.; Tambling, Craig J.; Hayward, Matt W.; Kerley, Graham I. H.

    2014-01-01

    Broad-scale models describing predator prey preferences serve as useful departure points for understanding predator-prey interactions at finer scales. Previous analyses used a subjective approach to identify prey weight preferences of the five large African carnivores, hence their accuracy is questionable. This study uses a segmented model of prey weight versus prey preference to objectively quantify the prey weight preferences of the five large African carnivores. Based on simulations of known predator prey preference, for prey species sample sizes above 32 the segmented model approach detects up to four known changes in prey weight preference (represented by model break-points) with high rates of detection (75% to 100% of simulations, depending on number of break-points) and accuracy (within 1.3±4.0 to 2.7±4.4 of known break-point). When applied to the five large African carnivores, using carnivore diet information from across Africa, the model detected weight ranges of prey that are preferred, killed relative to their abundance, and avoided by each carnivore. Prey in the weight ranges preferred and killed relative to their abundance are together termed “accessible prey”. Accessible prey weight ranges were found to be 14–135 kg for cheetah Acinonyx jubatus, 1–45 kg for leopard Panthera pardus, 32–632 kg for lion Panthera leo, 15–1600 kg for spotted hyaena Crocuta crocuta and 10–289 kg for wild dog Lycaon pictus. An assessment of carnivore diets throughout Africa found these accessible prey weight ranges include 88±2% (cheetah), 82±3% (leopard), 81±2% (lion), 97±2% (spotted hyaena) and 96±2% (wild dog) of kills. These descriptions of prey weight preferences therefore contribute to our understanding of the diet spectrum of the five large African carnivores. Where datasets meet the minimum sample size requirements, the segmented model approach provides a means of determining, and comparing, the prey weight range preferences of any carnivore

  14. An objective approach to determining the weight ranges of prey preferred by and accessible to the five large African carnivores.

    PubMed

    Clements, Hayley S; Tambling, Craig J; Hayward, Matt W; Kerley, Graham I H

    2014-01-01

    Broad-scale models describing predator prey preferences serve as useful departure points for understanding predator-prey interactions at finer scales. Previous analyses used a subjective approach to identify prey weight preferences of the five large African carnivores, hence their accuracy is questionable. This study uses a segmented model of prey weight versus prey preference to objectively quantify the prey weight preferences of the five large African carnivores. Based on simulations of known predator prey preference, for prey species sample sizes above 32 the segmented model approach detects up to four known changes in prey weight preference (represented by model break-points) with high rates of detection (75% to 100% of simulations, depending on number of break-points) and accuracy (within 1.3±4.0 to 2.7±4.4 of known break-point). When applied to the five large African carnivores, using carnivore diet information from across Africa, the model detected weight ranges of prey that are preferred, killed relative to their abundance, and avoided by each carnivore. Prey in the weight ranges preferred and killed relative to their abundance are together termed "accessible prey". Accessible prey weight ranges were found to be 14-135 kg for cheetah Acinonyx jubatus, 1-45 kg for leopard Panthera pardus, 32-632 kg for lion Panthera leo, 15-1600 kg for spotted hyaena Crocuta crocuta and 10-289 kg for wild dog Lycaon pictus. An assessment of carnivore diets throughout Africa found these accessible prey weight ranges include 88±2% (cheetah), 82±3% (leopard), 81±2% (lion), 97±2% (spotted hyaena) and 96±2% (wild dog) of kills. These descriptions of prey weight preferences therefore contribute to our understanding of the diet spectrum of the five large African carnivores. Where datasets meet the minimum sample size requirements, the segmented model approach provides a means of determining, and comparing, the prey weight range preferences of any carnivore species.

  15. Line spectrum and ion temperature measurements from tungsten ions at low ionization stages in large helical device based on vacuum ultraviolet spectroscopy in wavelength range of 500–2200 Å

    SciTech Connect

    Oishi, T. Morita, S.; Goto, M.; Huang, X. L.; Zhang, H. M.

    2014-11-15

    Vacuum ultraviolet spectra of emissions released from tungsten ions at lower ionization stages were measured in the Large Helical Device (LHD) in the wavelength range of 500–2200 Å using a 3 m normal incidence spectrometer. Tungsten ions were distributed in the LHD plasma by injecting a pellet consisting of a small piece of tungsten metal and polyethylene tube. Many lines having different wavelengths from intrinsic impurity ions were observed just after the tungsten pellet injection. Doppler broadening of a tungsten candidate line was successfully measured and the ion temperature was obtained.

  16. Satellite range delay simulator for a matrix-switched time division multiple-access network simulation system

    NASA Technical Reports Server (NTRS)

    Nagy, Lawrence A.

    1990-01-01

    The Systems Integration, Test, and Evaluation (SITE) facility at NASA Lewis Research Center is presently configured as a satellite-switched time division multiple access (SS-TDMA) network simulator. The purpose of SITE is to demonstrate and evaluate advanced communication satellite technologies, presently embodied by POC components developed under NASA contracts in addition to other hardware, such as ground terminals, designed and built in-house at NASA Lewis. Each ground terminal in a satellite communications system will experience a different aspect of the satellite's motion due mainly to daily tidal effects and station keeping, hence a different duration and rate of variation in the range delay. As a result of this and other effects such as local oscillator instability, each ground terminal must constantly adjust its transmit burst timing so that data bursts from separate ground terminals arrive at the satellite in their assigned time slots, preventing overlap and keeping the system in synchronism. On the receiving end, ground terminals must synchronize their local clocks using reference transmissions received through the satellite link. A feature of the SITE facility is its capability to simulate the varying propagation delays and associated Doppler frequency shifts that the ground terminals in the network have to cope with. Delay is ahcieved by means of two NASA Lewis designed and built range delay simulator (RDS) systems, each independently controlled locally with front panel switches or remotely by an experiment control and monitor (EC/M) computer.

  17. Wavelength meter having elliptical wedge

    DOEpatents

    Hackel, R.P.; Feldman, M.

    1992-12-01

    A wavelength meter is disclosed which can determine the wavelength of a laser beam from a laser source within an accuracy range of two parts in 10[sup 8]. The wavelength meter has wedge having an elliptically shaped face to the optical path of the laser source and includes interferometer plates which form a vacuum housing. 7 figs.

  18. Wavelength meter having elliptical wedge

    DOEpatents

    Hackel, Richard P.; Feldman, Mark

    1992-01-01

    A wavelength meter is disclosed which can determine the wavelength of a laser beam from a laser source within an accuracy range of two parts in 10.sup.8. The wavelength meter has wedge having an elliptically shaped face to the optical path of the laser source and includes interferometer plates which form a vacuum housing.

  19. Increased wavelength options in the visible and ultraviolet for Raman lasers operating on dual Raman modes.

    PubMed

    Mildren, R P; Piper, J A

    2008-03-01

    We report increased wavelength options from Raman lasers for Raman media having two Raman modes of similar gain coefficient. For an external-cavity potassium gadolinium tungstate Raman laser pumped at 532 nm, we show that two sets of Stokes orders are generated simultaneously by appropriate orientation of the Raman crystal, and also wavelengths that correspond to sums of the two Raman modes. Up to 14 visible Stokes lines were observed in the wavelength range 555-675 nm. The increase in Stokes wavelengths also enables a much greater selection of wavelengths to be accessed via intracavity nonlinear sum frequency and difference frequency mixing. For example, we demonstrate 30 output wavelength options for a wavelength-selectable 271-321 nm Raman laser with intracavity sum frequency mixing in BBO. We also present a theoretical analysis that enables prediction of wavelength options for dual Raman mode systems.

  20. Linear and nonlinear transmission of Fe{sup 2+}-doped ZnSe crystals at a wavelength of 2940 nm in the temperature range 20–220 °C

    SciTech Connect

    Il'ichev, N N; Pashinin, P P; Gulyamova, E S; Bufetova, G A; Shapkin, P V; Nasibov, A S

    2014-03-28

    The linear and nonlinear transmission of Fe{sup 2+}:ZnSe crystals is measured at a wavelength of 2940 nm in the temperature range 20 – 220 °C. It is found that, with increasing temperature from 20 °C to 150 – 220 °C, the transmission of Fe{sup 2+}:ZnSe crystals decreases in the case of incident radiation with an intensity of ∼5.5 MW cm{sup -2} and increases in the case of radiation with an intensity of 28 kW cm{sup -2}. At a temperature of 220 °C, the linear transmission almost coincides with the nonlinear transmission. The transmission spectra of Fe{sup 2+}:ZnSe crystals at temperatures of 22 and 220 °C in the wavelength range 500 – 7000 nm are presented. (active media)

  1. Photodissociation of van der Waals clusters of isoprene with oxygen, C5H8-O2, in the wavelength range 213-277 nm

    NASA Astrophysics Data System (ADS)

    Vidma, Konstantin V.; Frederix, Pim W. J. M.; Parker, David H.; Baklanov, Alexey V.

    2012-08-01

    The speed and angular distribution of O atoms arising from the photofragmentation of C5H8-O2, the isoprene-oxygen van der Waals complex, in the wavelength region of 213-277 nm has been studied with the use of a two-color dissociation-probe method and the velocity map imaging technique. Dramatic enhancement in the O atoms photo-generation cross section in comparison with the photodissociation of individual O2 molecules has been observed. Velocity map images of these "enhanced" O atoms consisted of five channels, different in their kinetic energy, angular distribution, and wavelength dependence. Three channels are deduced to be due to the one-quantum excitation of the C5H8-O2 complex into the perturbed Herzberg III state (3Δu) of O2. This excitation results in the prompt dissociation of the complex giving rise to products C5H8+O+O when the energy of exciting quantum is higher than the complex photodissociation threshold, which is found to be 41740 ± 200 cm-1 (239.6±1.2 nm). This last threshold corresponds to the photodissociation giving rise to an unexcited isoprene molecule. The second channel, with threshold shifted to the blue by 1480 ± 280 cm-1, corresponds to dissociation with formation of rovibrationally excited isoprene. A third channel was observed at wavelengths up to 243 nm with excitation below the upper photodissociation threshold. This channel is attributed to dissociation with the formation of a bound O atom C5H8-O2 + hv → C5H8-O2(3Δu) → C5H8O + O and/or to dissociation of O2 with borrowing of the lacking energy from incompletely cooled complex internal degrees of freedom C5H8*-O2 + hv → C5H8*-O2(3Δu) → C5H8 + O + O. The kinetic energy of the O atoms arising in two other observed channels corresponds to O atoms produced by photodissociation of molecular oxygen in the excited a 1Δg and b ^1 Σ _g^ + singlet states as the precursors. This indicates the formation of singlet oxygen O2(a 1Δg) and O2({b }^1 Σ _g^ +) after excitation of the C5

  2. Selective ablation of rabbit atherosclerotic plaque with less thermal effect by the control of pulse structure of a quantum cascade laser in the 5.7 μm wavelength range

    NASA Astrophysics Data System (ADS)

    Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

    2016-03-01

    Cholesteryl esters are main components of atherosclerotic plaques and have an absorption peak at the wavelength of 5.75 μm originated from C=O stretching vibration mode of ester bond. Our group achieved the selective ablation of atherosclerotic lesions using a quantum cascade laser (QCL) in the 5.7 μm wavelength range. QCLs are relatively new types of semiconductor lasers that can emit mid-infrared range. They are sufficiently compact and considered to be useful for clinical application. However, large thermal effects were observed because the QCL worked as quasicontinuous wave (CW) lasers due to its short pulse interval. Then we tried macro pulse irradiation (irradiation of pulses at intervals) of the QCL and achieved effective ablation with less-thermal effects than conventional quasi-CW irradiation. However, lesion selectivity might be changed by changing pulse structure. Therefore, in this study, irradiation effects of the macro pulse irradiation to rabbit atherosclerotic plaque and normal vessel were compared. The macro pulse width and the macro pulse interval were set to 0.5 and 12 ms, respectively, because the thermal relaxation time of rabbit normal and atherosclerotic aortas in the oscillation wavelength of the QCL was 0.5-12 ms. As a result, cutting difference was achieved between rabbit atherosclerotic and normal aortas by the macro pulse irradiation. Therefore, macro pulse irradiation of a QCL in the 5.7 μm wavelength range is effective for reducing thermal effects and selective ablation of the atherosclerotic plaque. QCLs have the potential of realizing less-invasive laser angioplasty.

  3. Porous silicon-VO{sub 2} based hybrids as possible optical temperature sensor: Wavelength-dependent optical switching from visible to near-infrared range

    SciTech Connect

    Antunez, E. E.; Salazar-Kuri, U.; Estevez, J. O.; Basurto, M. A.; Agarwal, V.; Campos, J.

    2015-10-07

    Morphological properties of thermochromic VO{sub 2}—porous silicon based hybrids reveal the growth of well-crystalized nanometer-scale features of VO{sub 2} as compared with typical submicron granular structure obtained in thin films deposited on flat substrates. Structural characterization performed as a function of temperature via grazing incidence X-ray diffraction and micro-Raman demonstrate reversible semiconductor-metal transition of the hybrid, changing from a low-temperature monoclinic VO{sub 2}(M) to a high-temperature tetragonal rutile VO{sub 2}(R) crystalline structure, coupled with a decrease in phase transition temperature. Effective optical response studied in terms of red/blue shift of the reflectance spectra results in a wavelength-dependent optical switching with temperature. As compared to VO{sub 2} film over crystalline silicon substrate, the hybrid structure is found to demonstrate up to 3-fold increase in the change of reflectivity with temperature, an enlarged hysteresis loop and a wider operational window for its potential application as an optical temperature sensor. Such silicon based hybrids represent an exciting class of functional materials to display thermally triggered optical switching culminated by the characteristics of each of the constituent blocks as well as device compatibility with standard integrated circuit technology.

  4. Porous silicon-VO2 based hybrids as possible optical temperature sensor: Wavelength-dependent optical switching from visible to near-infrared range

    NASA Astrophysics Data System (ADS)

    Antunez, E. E.; Salazar-Kuri, U.; Estevez, J. O.; Campos, J.; Basurto, M. A.; Jiménez Sandoval, S.; Agarwal, V.

    2015-10-01

    Morphological properties of thermochromic VO2—porous silicon based hybrids reveal the growth of well-crystalized nanometer-scale features of VO2 as compared with typical submicron granular structure obtained in thin films deposited on flat substrates. Structural characterization performed as a function of temperature via grazing incidence X-ray diffraction and micro-Raman demonstrate reversible semiconductor-metal transition of the hybrid, changing from a low-temperature monoclinic VO2(M) to a high-temperature tetragonal rutile VO2(R) crystalline structure, coupled with a decrease in phase transition temperature. Effective optical response studied in terms of red/blue shift of the reflectance spectra results in a wavelength-dependent optical switching with temperature. As compared to VO2 film over crystalline silicon substrate, the hybrid structure is found to demonstrate up to 3-fold increase in the change of reflectivity with temperature, an enlarged hysteresis loop and a wider operational window for its potential application as an optical temperature sensor. Such silicon based hybrids represent an exciting class of functional materials to display thermally triggered optical switching culminated by the characteristics of each of the constituent blocks as well as device compatibility with standard integrated circuit technology.

  5. High-performance GaSb laser diodes and diode arrays in the 2.1-3.3 micron wavelength range for sensing and defense applications

    NASA Astrophysics Data System (ADS)

    Dvinelis, Edgaras; TrinkÅ«nas, Augustinas; Greibus, Mindaugas; Kaušylas, Mindaugas; Žukauskas, Tomas; Å imonytÄ--, Ieva; Songaila, RamÅ«nas; Vizbaras, Augustinas; Vizbaras, Kristijonas

    2015-01-01

    Mid-infrared spectral region (2-4 μm) is gaining significant attention recently due to the presence of numerous enabling applications in the field of gas sensing, medical, and defense applications. Gas sensing in this spectral region is attractive due to the presence of numerous absorption lines for such gases as methane, ethane, ozone, carbon dioxide, carbon monoxide, etc. Sensing of the mentioned gas species is of particular importance for applications such as atmospheric LIDAR, petrochemical industry, greenhouse gas monitoring, etc. Defense applications benefit from the presence of covert atmospheric transmission window in the 2.1-2.3 micron band which is more eye-safe and offers less Rayleigh scattering than the conventional atmospheric windows in the near-infrared. Major requirement to enable these application is the availability of high-performance, continuous-wave laser sources in this window. Type-I GaSb-based laser diodes are ideal candidates for these applications as they offer direct emission possibility, high-gain and continuous wave operation. Moreover, due to the nature of type-I transition, these devices have a characteristic low operation voltage, which results in very low input powers and high wall-plug efficiency. In this work, we present recent results of 2 μm - 3.0 μm wavelength room-temperature CW light sources based on type-I GaSb developed at Brolis Semiconductors. We discuss performance of defense oriented high-power multimode laser diodes with < 1 W CW power output with over 30 % WPE as well as ~ 100 mW single TE00 Fabry-Perot chips. In addition, recent development efforts on sensing oriented broad gain superluminescent gain chips will be presented.

  6. Medium-Range Predictability of Contrail-Cirrus Demonstrated during Experiments Ml-Cirrus and Access-Ii

    NASA Astrophysics Data System (ADS)

    Schumann, U.

    2015-12-01

    The Contrail Cirrus Prediction model CoCiP (doi:10.5194/gmd-5-543-2012) has been applied quasi operationally to predict contrails for flight planning of ML-CIRRUS (C. Voigt, DLR, et al.) in Europe and for ACCESS II in California (B. Anderson, NASA, et al.) in March-May 2014. The model uses NWP data from ECMWF and past airtraffic data (actual traffic data are used for analysis). The forecasts provided a sequence of hourly forecast maps of contrail cirrus optical depth for 3.5 days, every 12 h. CoCiP has been compared to observations before, e.g. within a global climate-aerosol-contrail model (Schumann, Penner et al., ACPD, 2015, doi:10.5194/acpd-15-19553-2015). Good predictions would allow for climate optimal routing (see, e.g., US patent by Mannstein and Schumann, US 2012/0173147 A1). The predictions are tested by: 1) Local eyewitness reports and photos, 2) satellite observed cloudiness, 3) autocorrelation analysis of predictions for various forecast periods, 4) comparisons of computed with observed optical depth from COCS (doi:10.5194/amt-7-3233-2014, 2014) by IR METEOSAT-SEVIRI observations over Europe. The results demonstrate medium-range predictability of contrail cirrus to a useful degree for given traffic, soot emissions, and high-quality NWP data. A growing set of satellite, Lidar, and in-situ data from ML-CIRRUS and ACCENT are becoming available and will be used to further test the forecast quality. The autocorrelation of optical depth predictions is near 70% for 3-d forecasts for Europe (outside times with high Sahara dust loads), and only slightly smaller for continental USA. Contrail cirrus is abundant over Europe and USA. More than 1/3 of all cirrus measured with the research aircraft HALO during ML-CIRRUS was impacted by contrails. The radiative forcing (RF) is strongly daytime and ambience dependent. The net annual mean RF, based on our global studies, may reach up to 0.08 W/m2 globally, and may well exceed 1 W/m2 regionally, with maximum over Europe

  7. Use of layer strains in strained-layer superlattices to make devices for operation in new wavelength ranges, E. G. , InAsSb at 8 to 12. mu. m. [InAs/sub 1-x/Sb/sub x/

    DOEpatents

    Osbourn, G.C.

    1983-10-06

    An intrinsic semiconductor electro-optical device comprises a p-n junction intrinsically responsive, when cooled, to electromagnetic radiation in the wavelength range of 8 to 12 ..mu..m. This radiation responsive p-n junction comprises a strained-layer superlattice (SLS) of alternating layers of two different III-V semiconductors. The lattice constants of the two semiconductors are mismatched, whereby a total strain is imposed on each pair of alternating semiconductor layers in the SLS structure, the proportion of the total strain which acts on each layer of the pair being proportional to the ratio of the layer thicknesses of each layer in the pair.

  8. Long-range Transport of Dust and Smoke towards Barbados during Summer and Winter Season Measured with Three-Wavelength Polarization Lidar during SALTRACE-1, 2 and 3

    NASA Astrophysics Data System (ADS)

    Haarig, Moritz; Ansmann, Albert; Althausen, Dietrich; Klepel, André; Baars, Holger; Farrell, David; Toledano, Carlos

    2015-04-01

    The annual cycle of the north-south movement of the intertropical convergence zone has an impact on the sources and mixture of the dust transported to the Caribbean. In summer, pure Saharan dust from northern Africa dominates, while in winter the dust originates from southern West Africa and is mixed with biomass burning smoke. The island of Barbados (13°N, 59°W) is an ideal site to investigate the long-range transport of Saharan dust because it is advected more than 5000 km across the Atlantic Ocean without any disturbance by anthropogenic aerosol sources. To investigate these seasonal changes in dust transport we extended the Saharan Aerosol Long-Range Transport and Aerosol-Cloud Interaction Experiment (SALTRACE) in June-July 2013 by further two campaigns in February-March 2014 (SALTRACE-2) and June-July 2014 (SALTRACE-3). Additionally a ship cruise with a Raman polarization lidar on board from the Caribbean to the Cape Verde islands was performed in April-May 2013. Dual-polar sun photometer observations were performed continuously from June 2013 to July 2014 (see AERONET Barbados_SALTRACE site). For SALTRACE, we used a complex lidar system equipped with two Raman channels and a 532 nm high spectral resolution lidar (HSRL) channel to obtain daytime (HSRL) and nighttime (Raman) extinction profiles. For the first time the dust linear depolarization ratios at 355, 532 and 1064 nm were measured simultaneously. The linear depolarization ratio provides information about the presence and amount of dust. The spectrum yields information about the dust size distribution. Combined with the extinction-to-backscatter ratio (lidar ratio) a separation of mineral dust (fine-mode and coarse-mode fractions), biomass burning smoke and maritime aerosols is possible. The measurements are presently used for understanding of long-range transported dust and provide insight into the aerosol composition over the western Atlantic. The classification of different aerosol types will be

  9. Non-Destructive and Discriminating Identification of Illegal Drugs by Transient Absorption Spectroscopy in the Visible and Near-IR Wavelength Range

    NASA Astrophysics Data System (ADS)

    Sato, Chie; Furube, Akihiro; Katoh, Ryuzi; Nonaka, Hidehiko; Inoue, Hiroyuki

    2008-11-01

    We have tested the possibility of identifying illegal drugs by means of nanosecond transient absorption spectroscopy with a 10-ns UV-laser pulse for the excitation light and visible-to-near-IR light for the probe light. We measured the transient absorption spectra of acetonitrile solutions of d-methamphetamine, dl-3,4-methylenedioxymethamphetamine hydrochloride (MDMA), and dl-N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine hydrochloride (MBDB), which are illegal drugs widely consumed in Japan. Transient absorption signals of these drugs were observed between 400 and 950 nm, a range in which they are transparent in the ground state. By analyzing the spectra in terms of exponential and Gaussian functions, we could identify the drugs and discriminate them from chemical substances having similar structures. We propose that transient absorption spectroscopy will be a useful, non-destructive method of inspecting for illegal drugs, especially when they are dissolved in liquids. Such a method may even be used for drugs packed in opaque materials if it is further extended to utilize intense femtosecond laser pulses.

  10. Internal to external wavelength calibration

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash C.

    1999-01-01

    The spectra of Hen 1357 (the Stingray nebula) were used to check the internal to external wavelength calibration of the STIS first order CCD modes. The radial velocity of the Stingray nebula is known to high accuracy (< 1 km/sec) and the line with of the nebular line is very narrow (< 8 km/sec for the integrated nebula). Thus the observations of the Stingray nebula are ideal to check the internal to external wavelength calibration of the first order modes. The observations were taken in G430L and G750M modes using a 52 x 0.05 arcsec slit covering the wavelength range 2900 to 5700 A and 6295 to 6867 A, respectively. The observed wavelength range includes many nebular emission lines. The wavelengths of the nebular lines derived using the pipeline internal wavelength calibration were compared with the wavelengths derived from other ground based observations. In all cases, the wavelength match between the two is of the same order as the accuracy to which the line center can be measured. These results imply that there is no significant offset between the internal and external wavelength calibrations for these modes. The HDF-S QSO observations were also used for this test both for the first order and the Echelle modes. The results of the HDF-S QSO observations further confirm the above finding for the first order modes, and imply that there is no significant offset between the internal and external wavelength calibration for the Echelle modes.

  11. Opacity of iron, nickel, and copper plasmas in the x-ray wavelength range: Theoretical interpretation of 2p-3d absorption spectra

    SciTech Connect

    Blenski, T.; Loisel, G.; Poirier, M.; Thais, F.; Arnault, P.; Caillaud, T.; Fariaut, J.; Gilleron, F.; Pain, J.-C.; Porcherot, Q.; Reverdin, C.; Silvert, V.; Villette, B.; Bastiani-Ceccotti, S.; Turck-Chieze, S.; Foelsner, W.; Gaufridy de Dortan, F. de

    2011-09-15

    This paper deals with theoretical studies on the 2p-3d absorption in iron, nickel, and copper plasmas related to LULI2000 (Laboratoire pour l'Utilisation des Lasers Intenses, 2000J facility) measurements in which target temperatures were of the order of 20 eV and plasma densities were in the range 0.004-0.01 g/cm{sup 3}. The radiatively heated targets were close to local thermodynamic equilibrium (LTE). The structure of 2p-3d transitions has been studied with the help of the statistical superconfiguration opacity code sco and with the fine-structure atomic physics codes hullac and fac. A new mixed version of the sco code allowing one to treat part of the configurations by detailed calculation based on the Cowan's code rcg has been also used in these comparisons. Special attention was paid to comparisons between theory and experiment concerning the term features which cannot be reproduced by sco. The differences in the spin-orbit splitting and the statistical (thermal) broadening of the 2p-3d transitions have been investigated as a function of the atomic number Z. It appears that at the conditions of the experiment the role of the term and configuration broadening was different in the three analyzed elements, this broadening being sensitive to the atomic number. Some effects of the temperature gradients and possible non-LTE effects have been studied with the help of the radiative-collisional code scric. The sensitivity of the 2p-3d structures with respect to temperature and density in medium-Z plasmas may be helpful for diagnostics of LTE plasmas especially in future experiments on the {Delta}n=0 absorption in medium-Z plasmas for astrophysical applications.

  12. A full-duplex multiband access radio-over-fiber link with frequency multiplying millimeter-wave generation and wavelength reuse for upstream signal

    NASA Astrophysics Data System (ADS)

    Ma, Jianxin; Li, Yanjie

    2015-01-01

    A full-duplex radio-over-fiber (RoF) link providing multiband wireless accesses including 20 GHz, 40 GHz and 60 GHz millimeter (mm)-wave signal using a 10 GHz RF signal source is proposed. According to our theoretical analysis and simulation of the transmission performance of the signal along the single mode fiber, the code form distortion caused by the sideband walk-off effect due to the fiber chromatic dispersion can be eliminated, and the degradation caused by the fading effect on the down-stream signal is removed by adjusting the relative phase shift between the two sidebands. The upstream signal carried by the optical carrier abstracted from the downlink signal is also immune to the code outline distortion. The numerical simulation results show that the 20 km full-duplex RoF link with our generated optical mm-wave signal maintains good performance.

  13. Multiple wavelength light collimator and monitor

    NASA Technical Reports Server (NTRS)

    Gore, Warren J. (Inventor)

    2011-01-01

    An optical system for receiving and collimating light and for transporting and processing light received in each of N wavelength ranges, including near-ultraviolet, visible, near-infrared and mid-infrared wavelengths, to determine a fraction of light received, and associated dark current, in each wavelength range in each of a sequence of time intervals.

  14. Productions of I, I{sup *}, and C{sub 2}H{sub 5} in the A-band photodissociation of ethyl iodide in the wavelength range from 245 to 283 nm by using ion-imaging detection

    SciTech Connect

    Tang, Ying; Lee, Wei-Bin; Hu, Zhengfa; Zhang, Bing; Lin, King-Chuen

    2007-02-14

    Photodissociation dynamics of ethyl iodide in the A band has been investigated at several wavelengths between 245 and 283 nm using resonance-enhanced multiphoton ionization technique combined with velocity map ion-imaging detection. The ion images of I, I{sup *}, and C{sub 2}H{sub 5} fragments are analyzed to yield corresponding speed and angular distributions. Two photodissociation channels are found: I(5p {sup 2}P{sub 3/2})+C{sub 2}H{sub 5} (hotter internal states) and I{sup *}(5p {sup 2}P{sub 1/2})+C{sub 2}H{sub 5} (colder). In addition, a competitive ionization dissociation channel, C{sub 2}H{sub 5}I{sup +}+h{nu}{yields}C{sub 2}H{sub 5}+I{sup +}, appears at the wavelengths <266 nm. The I/I{sup *} branching of the dissociation channels may be obtained directly from the C{sub 2}H{sub 5}{sup +} images, yielding the quantum yield of I{sup *} about 0.63-0.76, comparable to the case of CH{sub 3}I. Anisotropy parameters ({beta}) determined for the I{sup *} channel remain at 1.9{+-}0.1 over the wavelength range studied, indicating that the I{sup *} production should originate from the {sup 3}Q{sub 0} state. In contrast, the {beta}(I) values become smaller above 266 nm, comprising two components, direct excitation of {sup 3}Q{sub 1} and nonadiabatic transition between the {sup 3}Q{sub 0} and {sup 1}Q{sub 1} states. The curve crossing probabilities are determined to be 0.24-0.36, increasing with the wavelength. A heavier branched ethyl group does not significantly enhance the I(5p {sup 2}P{sub 3/2}) production from the nonadiabatic contribution, as compared to the case of CH{sub 3}I.

  15. Absorption Spectroscopy in the 4.4-4.6 μ m Infrared Wavelength Range for the 10 Khz High-Speed Measurement of CO and CO2 Concentrations in Combusting Environments.

    NASA Astrophysics Data System (ADS)

    Fotia, Matthew L.; Sell, Brian C.; Hoke, John; Schauer, Fred

    2014-06-01

    An instrument has been developed to make 10 kHz in situ combustion gas measurements of carbon monoxide (CO) and carbon dioxide (CO_2) concentrations. Operating in both the 4.40 and 4.58 μ m wavelength ranges allows for the fundamental molecular absorption bands of both molecules to be utilized. Such concentration measurements allow for the determination of total combustion efficiency of a particular process, which has engineering implications when considering the energy available from a combustion process to be utilized for propulsion purposes. A brief discussion of the initial calibration of the sensor with a calibrated diffusion flame, Hencken burner, and pressure-concentration cell is made with the main focus of the current work being the application of the instrument to examine the structure of propagating detonation waves.

  16. Divinyl-end-functionalized polyethylenes: ready access to a range of telechelic polyethylenes through thiol-ene reactions.

    PubMed

    Norsic, Sebastien; Thomas, Coralie; D'Agosto, Franck; Boisson, Christophe

    2015-04-01

    Telechelic α,ω-iodo-vinyl-polyethylenes (Vin-PE-I) were obtained by catalytic ethylene polymerization in the presence of [(C5 Me5 )2 NdCl2 Li(OEt2 )2 ] in combination with a functionalized chain-transfer agent, namely, di(10-undecenyl)magnesium, followed by treatment of the resulting di(vinylpolyethylenyl)magnesium compounds ((vinyl-PE)2 Mg) with I2 . The iodo-functionalized vinylpolyethylenes (Vin-PE-I) were transformed into unique divinyl-functionalized polyethylenes (Vin-PE-Vin) by simple treatment with tBuOK in toluene at 95 °C. Thiol-ene reactions were then successfully performed on Vin-PE-Vin with functionalized thiols in the presence of AIBN. A range of homobifunctional telechelic polyethylenes were obtained on which a hydroxy, diol, carboxylic acid, amine, ammonium chloride, trimethoxysilyl, chloro, or fluoroalkyl group was installed quantitatively at each chain end. PMID:25688747

  17. Analysis of weld seam uniformity through temperature distribution by spatially resolved detector elements in the wavelength range of 0.3μm to 5μm for the detection of structural changing heating and cooling processes

    NASA Astrophysics Data System (ADS)

    Lempe, B.; Maschke, R.; Rudek, F.; Baselt, T.; Hartmann, P.

    2016-03-01

    Online process control systems often only detecting temperatures at a local area of the machining point and determining an integrated value. In order to determine the proper welding quality and the absence of defects, such as temperature induced stress cracks, it is necessary to do time and space resolved measurements before, during and after the production process. The system under development consists of a beam splitting unit which divides the electromagnetic radiation of the heated component on two different sensor types. For high temperatures, a sensor is used which is sensitive in the visible spectrum and has a dynamic range of 120dB.1 Thus, very high intensity differences can be displayed and a direct analysis of the temperature profile of the weld spots is possible.2 A second sensor is operating in the wavelength range from 1 micron to 5 microns and allows the determination of temperatures from approximately 200°C.3 At the beginning of a welding process, the heat-up phase of the metal is critical to the resultant weld quality. If a defined temperature range exceeded too fast, the risk of cracking is significantly increased.4 During the welding process the thermal supervision of the central processing location is decisive for a high secure weld. In the border areas as well as in connection of the welding process especially cooling processes are crucial for the homogeneity of the results. In order to obtain sufficiently accurate resolution of the dynamic heating- and cooling-processes, the system can carry out up to 500 frames per second.

  18. SWOC: Spectral Wavelength Optimization Code

    NASA Astrophysics Data System (ADS)

    Ruchti, G. R.

    2016-06-01

    SWOC (Spectral Wavelength Optimization Code) determines the wavelength ranges that provide the optimal amount of information to achieve the required science goals for a spectroscopic study. It computes a figure-of-merit for different spectral configurations using a user-defined list of spectral features, and, utilizing a set of flux-calibrated spectra, determines the spectral regions showing the largest differences among the spectra.

  19. Interference comparator for laser diode wavelength and wavelength instability measurement.

    PubMed

    Dobosz, Marek; Kożuchowski, Mariusz

    2016-04-01

    Method and construction of a setup, which allows measuring the wavelength and wavelength instability of the light emitted by a laser diode (or a laser light source with a limited time coherence in general), is presented. The system is based on Twyman-Green interferometer configuration. Proportions of phases of the tested and reference laser's interference fringe obtained for a set optical path difference are a measure of the unknown wavelength. Optical path difference in interferometer is stabilized. The interferometric comparison is performed in vacuum chamber. The techniques of accurate fringe phase measurements are proposed. The obtained relative standard uncertainty of wavelength evaluation in the tested setup is about 2.5 ⋅ 10(-8). Uncertainty of wavelength instability measurement is an order of magnitude better. Measurement range of the current setup is from 500 nm to 650 nm. The proposed technique allows high accuracy wavelength measurement of middle or low coherence sources of light. In case of the enlarged and complex frequency distribution of the laser, the evaluated wavelength can act as the length master in interferometer for displacement measurement. PMID:27131662

  20. Interference comparator for laser diode wavelength and wavelength instability measurement

    NASA Astrophysics Data System (ADS)

    Dobosz, Marek; KoŻuchowski, Mariusz

    2016-04-01

    Method and construction of a setup, which allows measuring the wavelength and wavelength instability of the light emitted by a laser diode (or a laser light source with a limited time coherence in general), is presented. The system is based on Twyman-Green interferometer configuration. Proportions of phases of the tested and reference laser's interference fringe obtained for a set optical path difference are a measure of the unknown wavelength. Optical path difference in interferometer is stabilized. The interferometric comparison is performed in vacuum chamber. The techniques of accurate fringe phase measurements are proposed. The obtained relative standard uncertainty of wavelength evaluation in the tested setup is about 2.5 ṡ 10-8. Uncertainty of wavelength instability measurement is an order of magnitude better. Measurement range of the current setup is from 500 nm to 650 nm. The proposed technique allows high accuracy wavelength measurement of middle or low coherence sources of light. In case of the enlarged and complex frequency distribution of the laser, the evaluated wavelength can act as the length master in interferometer for displacement measurement.

  1. Effect of Surface Oxidization on the Spectral Normal Emissivity of Aluminum 3A21 at the Wavelength of 1.5 m Over the Temperature Range from 800 K to 910 K

    NASA Astrophysics Data System (ADS)

    Shi, Deheng; Zou, Fenghui; Wang, Shuai; Zhu, Zunlue; Sun, Jinfeng

    2015-04-01

    This study explores the dependence of the spectral emissivity on the temperature ranging from 800 K to 910 K for an oxidizing surface of aluminum 3A21. In this experiment, the infrared radiation stemming from the specimen is received by an InGaAs photodiode detector, which operates at the wavelength of 1.5 m with a bandwidth of about 20 nm. The temperature of the specimen surface is determined by averaging the two R-type platinum-rhodium thermocouples, which are tightly welded on the specimen surface. The spectral emissivity is reported before the first measurement over the temperature range from 800 K to 910 K. The variation of the spectral emissivity with the heating time is evaluated at a given temperature. The variation of the spectral emissivity with temperature is discussed for a given heating time. Oscillations of the spectral emissivity have been observed, which are affirmed to be connected with the thickness of the oxidization layer on the specimen surface, and formed by the interference effect between the radiation coming from the oxidization layer and the radiation stemming from the substrate. The effect of surface oxidization on the spectral emissivity of aluminum 3A21 is evaluated, and compared with that of SPHC steel. Analytical expressions of the spectral emissivity of aluminum 3A21 versus the temperature are derived at some given heating times. A conclusion is obtained that the experimental results obtained at a given heating time from 800 K to 910 K abide by the same functional form.

  2. Optimized wavelength selection for molecular absorption thermometry.

    PubMed

    An, Xinliang; Caswell, Andrew W; Lipor, John J; Sanders, Scott T

    2015-04-01

    A differential evolution (DE) algorithm is applied to a recently developed spectroscopic objective function to select wavelengths that optimize the temperature precision of water absorption thermometry. DE reliably finds optima even when many-wavelength sets are chosen from large populations of wavelengths (here 120 000 wavelengths from a spectrum with 0.002 cm(-1) resolution calculated by 16 856 transitions). Here, we study sets of fixed wavelengths in the 7280-7520 cm(-1) range. When optimizing the thermometer for performance within a narrow temperature range, the results confirm that the best temperature precision is obtained if all the available measurement time is split judiciously between the two most temperature-sensitive wavelengths. In the wide temperature range case (thermometer must perform throughout 280-2800 K), we find (1) the best four-wavelength set outperforms the best two-wavelength set by an average factor of 2, and (2) a complete spectrum (all 120 000 wavelengths from 16 856 transitions) is 4.3 times worse than the best two-wavelength set. Key implications for sensor designers include: (1) from the perspective of spectroscopic temperature sensitivity, it is usually sufficient to monitor two or three wavelengths, depending on the sensor's anticipated operating temperature range; and (2) although there is a temperature precision penalty to monitoring a complete spectrum, that penalty may be small enough, particularly at elevated pressure, to justify the complete-spectrum approach in many applications.

  3. Aerial perches and free-range laying hens: the effect of access to aerial perches and of individual bird parameters on keel bone injuries in commercial free-range laying hens.

    PubMed

    Donaldson, C J; Ball, M E E; O'Connell, N E

    2012-02-01

    The aim of this trial was to determine the effect of aerial perches on keel bone injuries and tibia bone characteristics in free-range laying hens. The relationship between keel bone injuries and individual bird parameters, such as weight, girth, wing:girth ratio, feather coverage, and tibia bone characteristics, was also assessed. Five commercial free-range houses, each containing between 7,000 and 8,000 birds, were used. The houses and range areas were divided in half; in half of the house, birds had access to aerial perches (P) and in the other half, they did not (NP). On 13 occasions between 17 and 70 wk of age, 20 birds per treatment were randomly selected from the slatted area and palpated for keel bone injury. At 72 wk of age, 30 birds per treatment in each of 4 houses were selected at random, weighed, and then euthanized. Girth and wing area and feather coverage were measured. The keel and left tibia bones were removed and keel bones were scored for injury. Tibia bones were weighed and diameter, length, breaking strength, and ash content recorded. Results indicated that access to aerial perches did not affect tibia bone measures (P > 0.05). Average palpated keel bone score increased with age of the hens (P < 0.001) but was not significantly affected by perch treatment (P > 0.05). There was a significant interaction between treatment and farm on keel bone injuries measured at dissection (P < 0.05), with the probability of birds having high keel-damage scores increasing in the perched treatment in some farms but not others. In general, as the keel bone injury score measured at dissection increased, the breaking strength (P < 0.001) and ash content (P < 0.05) of the tibia bone decreased. It is suggested that individual variation in bone strength contributes to differences in susceptibility to keel injury. No relationship existed between keel-injury score measured at dissection and individual parameters, such as weight, girth, or wing:girth ratio (P > 0

  4. Dual Wavelength Lasers

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.

    2010-01-01

    Dual wavelength lasers are discussed, covering fundamental aspects on the spectroscopy and laser dynamics of these systems. Results on Tm:Ho:Er:YAG dual wavelength laser action (Ho at 2.1 m and Er at 2.9 m) as well as Nd:YAG (1.06 and 1.3 m) are presented as examples of such dual wavelength systems. Dual wavelength lasers are not common, but there are criteria that govern their behavior. Based on experimental studies demonstrating simultaneous dual wavelength lasing, some general conclusions regarding the successful operation of multi-wavelength lasers can be made.

  5. Quadrature wavelength scanning interferometry.

    PubMed

    Moschetti, Giuseppe; Forbes, Alistair; Leach, Richard K; Jiang, Xiang; O'Connor, Daniel

    2016-07-10

    A novel method to double the measurement range of wavelength scanning interferometery (WSI) is described. In WSI the measured optical path difference (OPD) is affected by a sign ambiguity, that is, from an interference signal it is not possible to distinguish whether the OPD is positive or negative. The sign ambiguity can be resolved by measuring an interference signal in quadrature. A method to obtain a quadrature interference signal for WSI is described, and a theoretical analysis of the advantages is reported. Simulations of the advantages of the technique and of signal errors due to nonideal quadrature are discussed. The analysis and simulation are supported by experimental measurements to show the improved performances. PMID:27409307

  6. Jupiter before Juno: State of the atmosphere at cloud level in 2016 from PlanetCam observations in the 0.4-1.7 microns wavelength range and amateur observations in the visible

    NASA Astrophysics Data System (ADS)

    Hueso, Ricardo; Sanchez-Lavega, Agustin; Perez-Hoyos, Santiago; Rojas, Jose Felix; Iñurrigarro, Peio; Mendikoa, Iñigo; Go, Christopher; PVOL-IOPW Team

    2016-10-01

    The arrival of Juno to Jupiter provides a unique opportunity to link findings of the inner structure of the planet with astronomical observations of its meteorology at cloud level. Long time base observations of Jupiter's atmosphere before and during the Juno mission are critical in providing context to Junocam observations and may benefit the interpretation of the MWR data on the lower atmosphere structure as well as Juno data on the depth of the zonal winds. We have performed a long campaign of observations in the visible with the PlanetCam lucky imaging instrument in the 2.2m telescope at Calar Alto Observatory in Spain with observations obtained in December 2015 and in March, May, June and July 2016. In observations under good atmospheric seeing, the instrument allows to obtain images with a spatial resolution of 0.05'' in the visible and 0.1'' from 1.0 to 1.7 microns. The later is an interesting range of wavelengths for observing Jupiter because of the existence of several strong and weak methane absorption bands not generally used in high-resolution ground-based observations of the planet. A combination of images using narrow filters centered in methane absorption bands and their adjacent continuum allows studying the vertical structure of the clouds at horizontal spatial scales of 350-1000 km over the planet depending on the atmospheric seeing and filter used. The best images can be further processed showing features at spatial resolutions of about 150 km. We have also monitored the state of the atmosphere with images obtained by amateur astronomers contributing to the Planetary Virtual Observatory Laboratory database (http://pvol.ehu.eus). Based on both datasets we present zonal winds from -70 to +75 deg with an accuracy of 10 m/s in the low latitudes and 25 m/s in subpolar latitudes. Relative altitude maps of features observed in bands J, H and others with different methane absorption will be presented.

  7. The RoF-WDM-PON for Wireless and Wire Layout with Multi-wavelength Fiber Laser and Carrier Reusing

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Zheng, Zhuowen

    2013-09-01

    In this paper, we design a WDM-RoF-PON based on multi-wavelength fiber laser and CSRZ-DPSK, which can achieve wire-line and wireless access synchronously without any RF source in ONU. The multi-wavelength fiber laser is the union light source of WDM-PON. By the RSOA and downstream light source reusing, the ONU can also omit laser source and makes the WDM-PON to be colorless. The networking has the credible transmission property, including wireless access and fiber transmission. The networking also has excellent covering range.

  8. Review of short wavelength lasers

    SciTech Connect

    Hagelstein, P.L.

    1985-03-18

    There has recently been a substantial amount of research devoted to the development of short wavelength amplifiers and lasers. A number of experimental results have been published wherein the observation of significant gain has been claimed on transitions in the EUV and soft x-ray regimes. The present review is intended to discuss the main approaches to the creation of population inversions and laser media in the short wavelength regime, and hopefully aid workers in the field by helping to provide access to a growing literature. The approaches to pumping EUV and soft x-ray lasers are discussed according to inversion mechanism. The approaches may be divided into roughly seven categories, including collisional excitation pumping, recombination pumping, direct photoionization and photoexcitation pumping, metastable state storage plus optical pumping, charge exchange pumping, and finally, the extension of free electron laser techniques into the EUV and soft x-ray regimes. 250 references.

  9. Free range rearing of pigs with access to pasture grazing - effect on fatty acid composition and lipid oxidation products.

    PubMed

    Nilzén, V; Babol, J; Dutta, P C; Lundeheim, N; Enfält, A C; Lundström, K

    2001-07-01

    The influence of free-range rearing, RN genotype and sex on different pig meat quality traits, including intramuscular fatty acid composition and levels of lipid oxidation products, were studied. A total of 60 Hampshire crossbred pigs were reared outdoors for two months with access to green feed, while 60 others were kept indoors, in a 120-m(2)-large pen, throughout the rearing period. From these 120 animals a subsample of 44 animals was chosen for meat quality analysis. Of the three factors studied, the RN genotype had the largest influence on basic technological meat quality traits, whereas the rearing conditions and sex had limited effects. However, outdoor rearing resulted in higher levels of polyunsaturated fatty acids in the intramuscular fat (P=0.026) and in an increased level of vitamin E (P=0.030) compared with the pigs that had been reared indoors. The sex and RN genotype of the animals also had an effect on the fatty acid profile: females had higher levels of unsaturated fatty acids (P=0.003) as well as lower levels of saturated fatty acids (P=0.011) than castrated males. Carriers of the RN(-) allele expressed a higher sum of omega-3 fatty acids (P=0.047) and C22:5 (P=0.012) than did the non-carriers. In a storage study where meat from free-range and indoor reared pigs was stored for 3 months at-20°C, it was shown that the lipid oxidation product malondialdehyde was formed at increased levels in animals that had a higher lean meat percentage than others, i.e. females that were carriers of the RN(-) gene and that were reared outdoors. PMID:22062255

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

    PubMed Central

    Jirauschek, Christian; Huber, Robert

    2015-01-01

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

  11. Wavelength independent interferometer

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  12. Effective wavelength for multicolor/pyrometry.

    PubMed

    Gardner, J L

    1980-09-15

    The concept of a temperature varying effective wavelength has recently been applied in multiwavelength pyrometry. The effective wavelength is shown to be discontinuous at a particular temperature, and the properties of the effective wavelength over a wide temperature range are explained. It is shown that a simple relationship is sufficient to calculate the effective wavelength and hence radiance at a given temperature without resorting to a convolution integration, in particular where broad filters are used to improve signal levels in a pyrometer. PMID:20234565

  13. A novel burst-mode all-optical wavelength converter based on gain-clamping structure

    NASA Astrophysics Data System (ADS)

    Zhao, B.; Ke, C. J.; Zhao, Y.; Liu, D. M.

    2011-02-01

    A novel gain-clamped wavelength converter (GCWC) is proposed to make the hybrid TDM-WDM PON architecture based on wavelength conversion feasible, and its operation principle is also demonstrated. The power budget of this network is measured to identify the architecture can support 4096 users who share 40Gbit/s accessing capacity on a single trunk fiber. And optical power equalization functionality and burst transparency characteristic of GCWC is experimentally evaluated, and the results show that the GCWC makes burst signals from different transmitters with up to 5 dB dynamic range equalized and is transparency for burst signals.

  14. Wavelength Anomalies in UV-Vis Spectrophotometry

    NASA Astrophysics Data System (ADS)

    Tellinghuisen, J.

    2012-06-01

    Commercial spectrophotometers are great tools for recording absorption spectra of low-to-moderate resolution and high photometic quality. However, in the case of at least one such instrument, the Shimadzu UV-2101PC (and by assumption, similar Shimadzu models), the wavelength accuracy may not match the photometric accuracy. In fact the wavelength varies with slit width, spectral sampling interval, and even the specified range, with a smoothing algorithm invoked any time the spectrum includes more than 65 sampled wavelengths. This behavior appears not to be documented anywhere, but it has been present for at least 20 years and persists even in the latest software available to run the instrument. The wavelength shifts can be as large as 1 nm, so for applications where wavelength accuracy better than this is important, wavelength calibration must be done with care to ensure that the results are valid for the parameters used to record the target spectra.

  15. Big Data, Small Data: Accessing and Manipulating Geoscience Data Ranging From Repositories to Student-Collected Data Sets Using GeoMapApp

    NASA Astrophysics Data System (ADS)

    Goodwillie, A. M.

    2015-12-01

    We often demand information and data to be accessible over the web at no cost, and no longer do we expect to spend time labouriously compiling data from myriad sources with frustratingly-different formats. Instead, we increasingly expect convenience and consolidation. Recent advances in web-enabled technologies and cyberinfrastructure are answering those calls by providing data tools and resources that can transform undergraduate education. By freeing up valuable classroom time, students can focus upon gaining deeper insights and understanding from real-world data. GeoMapApp (http://www.geomapapp.org) is a map-based data discovery and visualisation tool developed at Lamont-Doherty Earth Observatory. GeoMapApp promotes U-Learning by working across all major computer platforms and functioning anywhere with internet connectivity, by lowering socio-economic barriers (it is free), by seamlessly integrating thousands of built-in research-grade data sets under intuitive menus, and by being adaptable to a range of learning environments - from lab sessions, group projects, and homework assignments to in-class pop-ups. GeoMapApp caters to casual and specialist users alike. Contours, artificial illumination, 3-D displays, data point manipulations, cross-sectional profiles, and other display techniques help students better grasp the content and geospatial context of data. Layering capabilities allow easy data set comparisons. The core functionality also applies to imported data sets: Student-collected data can thus be imported and analysed using the same techniques. A new Save Session function allows educators to preserve a pre-loaded state of GeoMapApp. When shared with a class, the saved file allows every student to open GeoMapApp at exactly the same starting point from which to begin their data explorations. Examples of built-in data sets include seafloor crustal age, earthquake locations and focal mechanisms, analytical geochemistry, ocean water physical properties, US and

  16. Long-wavelength photonic integrated circuits and avalanche photodetectors

    NASA Astrophysics Data System (ADS)

    Tsou, Yi-Jen D.; Zaytsev, Sergey; Pauchard, Alexandre; Hummel, Steve; Lo, Yu-Hwa

    2001-10-01

    Fast-growing internet traffic volume require high data communication bandwidth over longer distances. Access network bottlenecks put pressure on short-range (SR) telecommunication systems. To effectively address these datacom and telecom market needs, low-cost, high-speed laser modules at 1310 to 1550 nm wavelengths and avalanche photodetectors are required. The great success of GaAs 850nm VCSEls for Gb/s Ethernet has motivated efforts to extend VCSEL technology to longer wavelengths in the 1310 and 1550 nm regimes. However, the technological challenges associated with materials for long wavelength VCSELs are tremendous. Even with recent advances in this area, it is believed that significant additional development is necessary before long wavelength VCSELs that meet commercial specifications will be widely available. In addition, the more stringent OC192 and OC768 specifications for single-mode fiber (SMF) datacom may require more than just a long wavelength laser diode, VCSEL or not, to address numerous cost and performance issues. We believe that photonic integrated circuits (PICs), which compactly integrate surface-emitting lasers with additional active and passive optical components with extended functionality, will provide the best solutions to today's problems. Photonic integrated circuits have been investigated for more than a decade. However, they have produced limited commercial impact to date primarily because the highly complicated fabrication processes produce significant yield and device performance issues. In this presentation, we will discuss a new technology platform of InP-based PICs compatible with surface-emitting laser technology, as well as a high data rate externally modulated laser module. Avalanche photodetectors (APDs) are the key component in the receiver to achieve high data rate over long transmission distance because of their high sensitivity and large gain- bandwidth product. We have used wafer fusion technology to achieve In

  17. Millimeter wavelength propagation studies

    NASA Technical Reports Server (NTRS)

    Hodge, D. B.

    1974-01-01

    The investigations conducted for the Millimeter Wavelength Propagation Studies during the period December, 1966, to June 1974 are reported. These efforts included the preparation for the ATS-5 Millimeter Wavelength Propagation Experiment and the subsequent data acquisition and data analysis. The emphasis of the OSU participation in this experiment was placed on the determination of reliability improvement resulting from the use of space diversity on a millimeter wavelength earth-space communication link. Related measurements included the determination of the correlation between radiometric temperature and attenuation along the earth-space propagation path. Along with this experimental effort a theoretical model was developed for the prediction of attenuation statistics on single and spatially separated earth space propagation paths. A High Resolution Radar/Radiometer System and Low Resolution Radar System were developed and implemented for the study of intense rain cells in preparation for the ATS-6 Millimeter Wavelength Propagation Experiment.

  18. GHRS Cycle 5 Echelle Wavelength Monitor

    NASA Astrophysics Data System (ADS)

    Soderblom, David

    1995-07-01

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

  19. High-power frequency comb in the range of 2-2.15  μm based on a holmium fiber amplifier seeded by wavelength-shifted Raman solitons from an erbium-fiber laser.

    PubMed

    Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluca

    2014-03-15

    We demonstrate a room-temperature high-power frequency comb source covering the spectral region from 2 to 2.15 μm. The source is based on a femtosecond erbium-fiber laser operating at 1.55 μm with a repetition rate of 250 MHz, wavelength-shifted up to 2.06 μm by the solitonic Raman effect, seeding a large-mode-area holmium (Ho) fiber amplifier pumped by a thulium (Tm) fiber laser emitting at 1.94 μm. The frequency comb has an integrated power of 2 W, with overall power fluctuations as low as 0.3%. The beatnote between the comb and a high-spectral-purity, single-frequency Tm-Ho laser has a linewidth of 32 kHz over 1 ms observation time, with a signal-to-noise ratio in excess of 30 dB.

  20. Photodissociation of van der Waals clusters of isoprene with oxygen, C{sub 5}H{sub 8}-O{sub 2}, in the wavelength range 213-277 nm

    SciTech Connect

    Vidma, Konstantin V.; Frederix, Pim W. J. M.; Parker, David H.; Baklanov, Alexey V.

    2012-08-07

    The speed and angular distribution of O atoms arising from the photofragmentation of C{sub 5}H{sub 8}-O{sub 2}, the isoprene-oxygen van der Waals complex, in the wavelength region of 213-277 nm has been studied with the use of a two-color dissociation-probe method and the velocity map imaging technique. Dramatic enhancement in the O atoms photo-generation cross section in comparison with the photodissociation of individual O{sub 2} molecules has been observed. Velocity map images of these 'enhanced' O atoms consisted of five channels, different in their kinetic energy, angular distribution, and wavelength dependence. Three channels are deduced to be due to the one-quantum excitation of the C{sub 5}H{sub 8}-O{sub 2} complex into the perturbed Herzberg III state ({sup 3}{Delta}{sub u}) of O{sub 2}. This excitation results in the prompt dissociation of the complex giving rise to products C{sub 5}H{sub 8}+O+O when the energy of exciting quantum is higher than the complex photodissociation threshold, which is found to be 41740 {+-} 200 cm{sup -1} (239.6{+-}1.2 nm). This last threshold corresponds to the photodissociation giving rise to an unexcited isoprene molecule. The second channel, with threshold shifted to the blue by 1480 {+-} 280 cm{sup -1}, corresponds to dissociation with formation of rovibrationally excited isoprene. A third channel was observed at wavelengths up to 243 nm with excitation below the upper photodissociation threshold. This channel is attributed to dissociation with the formation of a bound O atom C{sub 5}H{sub 8}-O{sub 2}+hv{yields} C{sub 5}H{sub 8}-O{sub 2}({sup 3}{Delta}{sub u}) {yields} C{sub 5}H{sub 8}O + O and/or to dissociation of O{sub 2} with borrowing of the lacking energy from incompletely cooled complex internal degrees of freedom C{sub 5}H{sub 8}{sup *}-O{sub 2}+hv{yields} C{sub 5}H{sub 8}{sup *}-O{sub 2}({sup 3}{Delta}{sub u}) {yields} C{sub 5}H{sub 8}+ O + O. The kinetic energy of the O atoms arising in two other observed channels

  1. Exploiting the short wavelength gain of silica-based thulium-doped fiber amplifiers.

    PubMed

    Li, Z; Jung, Y; Daniel, J M O; Simakov, N; Tokurakawa, M; Shardlow, P C; Jain, D; Sahu, J K; Heidt, A M; Clarkson, W A; Alam, S U; Richardson, D J

    2016-05-15

    Short wavelength operation (1650-1800 nm) of silica-based thulium-doped fiber amplifiers (TDFAs) is investigated. We report the first demonstration of in-band diode-pumped silica-based TDFAs working in the 1700-1800 nm waveband. Up to 29 dB of small-signal gain is achieved in this spectral region, with an operation wavelength accessible by diode pumping as short as 1710 nm. Further gain extension toward shorter wavelengths is realized in a fiber laser pumped configuration. A silica-based TDFA working in the 1650-1700 nm range with up to 29 dB small-signal gain and noise figure as low as 6.5 dB is presented. PMID:27176961

  2. The radio-on-fiber-wavelength-division-multiplexed-passive-optical network (WDM-RoF-PON) for wireless and wire layout with linearly-polarized dual-wavelength fiber laser and carrier reusing

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Chang, Jun

    2013-07-01

    In this paper, we design a WDM-RoF-PON based on linearly-polarized dual-wavelength fiber laser and CSRZ-DPSK, which can achieve wire-line and wireless access synchronously. With the CSRZ-DPSK modulation, the wireless access in ONU can save RF source and the frequency of radio carrier can be controlled by OLT. The dual-wavelength fiber laser is the union light source of WDM-PON with polarization multiplexing. By the RSOA and downstream light source reusing, the ONU can save omit laser source and makes the WDM-PON to be colorless. The networking has the credible transmission property, including wireless access and fiber transmission. The networking also has excellent covering range.

  3. Wavelength tunable alexandrite regenerative amplifier

    SciTech Connect

    Harter, D.J.; Bado, P.

    1988-11-01

    We describe a wavelength tunable alexandrite regenerative amplifier which is used to amplify nanosecond slices from a single-frequency cw dye laser or 50-ps pulses emitted by a diode laser to energies in the 10-mJ range. The amplified 5-ns slices generated by the cw-pumped line narrowed dye laser are Fourier transform limited. The 50-ps pulses emitted by a gain-switched diode laser are amplified by more than 10 orders of magnitude in a single stage.

  4. Short wavelength laser

    DOEpatents

    Hagelstein, P.L.

    1984-06-25

    A short wavelength laser is provided that is driven by conventional-laser pulses. A multiplicity of panels, mounted on substrates, are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path. When the panels are illuminated by the conventional-laser pulses, single pass EUV or soft x-ray laser pulses are produced.

  5. Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440-6810 Å in the γ Velorum cluster, and calibration of spectral indices

    NASA Astrophysics Data System (ADS)

    Damiani, F.; Prisinzano, L.; Micela, G.; Randich, S.; Gilmore, G.; Drew, J. E.; Jeffries, R. D.; Frémat, Y.; Alfaro, E. J.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Lanzafame, A. C.; Pancino, E.; Recio-Blanco, A.; Sacco, G. G.; Smiljanic, R.; Jackson, R. J.; de Laverny, P.; Morbidelli, L.; Worley, C. C.; Hourihane, A.; Costado, M. T.; Jofré, P.; Lind, K.; Maiorca, E.

    2014-06-01

    We present a study of spectral diagnostics available from optical spectra with R = 17 000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the γ Vel young cluster, with the purpose of classifying these stars and finding their fundamental parameters. We define several spectroscopic indices, sampling the amplitude of TiO bands, the Hα line core and wings, and temperature- and gravity-sensitive sets of lines, each useful as a Teff or log g indicator over a limited range of stellar spectral types. Hα line indices are also useful as chromospheric activity or accretion indicators. Furthermore, we use all indices to define additional global Teff- and log g-sensitive indices τ and γ, valid for the entire range of types in the observed sample. We find a clear difference between gravity indices of main-sequence and pre-main-sequence stars, as well as a much larger difference between these and giant stars. The potentially great usefulness of the (γ,τ) diagram as a distance-independent age measurement tool for young clusters is discussed. We discuss the effect on the defined indices of classical T Tauri star veiling, which is however detected in only a few stars in the present sample. Then, we present tests and calibrations of these indices, on the basis of both photometry and literature reference spectra, from the UVES Paranal Observatory Projectand the ELODIE 3.1 Library. The known properties of these stars, spanning a wide range of stellar parameters, enable us to obtain a good understanding of the performances of our new spectral indices. For non-peculiar stars with known temperature, gravity, and metallicity, we are able to calibrate quantitatively our indices, and derive stellar parameters for a wide range of stellar types. To this aim, a new composite index is defined, providing a good metallicity indicator. The ability of our indices to select peculiar, or otherwise rare classes of stars is also established. For pre

  6. Short wavelength FELs using the SLAC linac

    SciTech Connect

    Winick, H.; Bane, K.; Boyce, R.

    1993-08-01

    Recent technological developments have opened the possibility to construct a device which we call a Linac Coherent Light Source (LCLS); a fourth generation light source, with brightness, coherence, and peak power far exceeding other sources. Operating on the principle of the free electron laser (FEL), the LCLS would extend the range of FEL operation to much aborter wavelength than the 240 mn that has so far been reached. We report the results of studies of the use of the SLAC linac to drive an LCLS at wavelengths from about 3-100 nm initially and possibly even shorter wavelengths in the future. Lasing would be achieved in a single pass of a low emittance, high peak current, high energy electron beam through a long undulator. Most present FELs use an optical cavity to build up the intensity of the light to achieve lasing action in a low gain oscillator configuration. By eliminating the optical cavity, which is difficult to make at short wavelengths, laser action can be extended to shorter wavelengths by Self-Amplified-Spontaneous-Emission (SASE), or by harmonic generation from a longer wavelength seed laser. Short wavelength, single pass lasers have been extensively studied at several laboratories and at recent workshops.

  7. High-speed random access laser tuning

    SciTech Connect

    Thompson, D.C.; Busch, G.E.; Hewitt, C.J.; Remelius, D.K.; Shimada, T.; Strauss, C.E.; Wilson, C.W.; Zaugg, T.J.

    1999-04-01

    We have developed a technique for laser tuning at rates of 100 kHz or more using a pair of acousto-optic modulators. In addition to all-electronic wavelength control, the same modulators also can provide electronically variable {ital Q}-switching, cavity length and power stabilization, chirp and linewidth control, and variable output coupling, all at rates far beyond what is possible with conventional mechanically tuned components. Tuning rates of 70 kHz have been demonstrated on a radio-frequency-pumped CO{sub 2} laser, with random access to over 50 laser lines spanning a 17{percent} range in wavelength and with wavelength discrimination better than 1 part in 1000. A compact tuner and {ital Q}-switch has been deployed in a 5{endash}10-kHz pulsed lidar system. The modulators each operate at a fixed Bragg angle, with the acoustic frequency determining the selected wavelength. This arrangement doubles the wavelength resolution without introducing an undesirable frequency shift. {copyright} 1999 Optical Society of America

  8. Short wavelength laser

    DOEpatents

    Hagelstein, Peter L.

    1986-01-01

    A short wavelength laser (28) is provided that is driven by conventional-laser pulses (30, 31). A multiplicity of panels (32), mounted on substrates (34), are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path (42). When the panels (32) are illuminated by the conventional-laser pulses (30, 31), single pass EUV or soft x-ray laser pulses (44, 46) are produced.

  9. Observations of Venus at 1-meter wavelength

    NASA Astrophysics Data System (ADS)

    Butler, Bryan J.

    2014-11-01

    Radio wavelength observations of Venus (including from the Magellan spacecraft) have been a powerful method of probing its surface and atmosphere since the 1950's. The emission is generally understood to come from a combination of emission and absorption in the subsurface, surface, and atmosphere at cm and shorter wavelengths [1]. There is, however, a long-standing mystery regarding the long wavelength emission from Venus. First discovered at wavelengths of 50 cm and greater [2], the effect was later confirmed to extend to wavelengths as short as 13 cm [1,3]. The brightness temperatures are depressed significantly 50 K around 10-20 cm, increasing to as much as 200 K around 1 m) from what one would expect from a "normal" surface (e.g., similar to the Moon or Earth) [1-3].No simple surface and subsurface model of Venus can reproduce these large depressions in the long wavelength emission [1-3]. Simple atmospheric and ionospheric models fail similarly. In an attempt to constrain the brightness temperature spectrum more fully, new observations have been made at wavelengths that cover the range 60 cm to 1.3 m at the Very Large Array, using the newly available low-band receiving systems there [4]. The new observations were made over a very wide wavelength range and at several Venus phases, with that wide parameter space coverage potentially allowing us to pinpoint the cause of the phenomenon. The observations and potential interpretations will be presented and discussed.[1] Butler et al. 2001, Icarus, 154, 226. [2] Schloerb et al. 1976, Icarus, 29, 329; Muhleman et al. 1973, ApJ, 183, 1081; Condon et al. 1973, ApJ, 183, 1075; Kuzmin 1965, Radiophysics. [3] Butler & Sault 2003, IAUSS, 1E, 17B. [4] Intema et al. 2014, BASI, 1.

  10. Wavelength agile holmium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Simakov, N.; Daniel, J. M. O.; Ward, J.; Clarkson, W. A.; Hemming, A.; Haub, J.

    2016-03-01

    For the first time, an electronically-controlled, wavelength-agile tuneable holmium-doped fibre laser is presented. A narrow-band acousto-optic tuneable filter was characterized and used as the wavelength selective element to avoid any inertial effects associated with opto-mechanical tuning mechanisms. We demonstrate operation over a 90 nm wavelength range spanning 2040 - 2130 nm. The laser produced >150 mW over this entire range with a signal-to-noise ratio of >45 dB and line-width of ~0.16 nm. Switching times of ~35 μs and sweep rates of up to 9 nm/ms were also demonstrated.

  11. SDIO long wavelength infrared detector requirements

    NASA Technical Reports Server (NTRS)

    Duston, Dwight

    1990-01-01

    The Strategic Defense Initiative Organization (SDIO) has a significant requirement for infrared sensors for surveillance, tracking and discrimination of objects in space. Projected SDIO needs cover the range from short wavelengths out to 30 microns. Large arrays are required, and producibility and cost are major factors. The SDIO is pursuing several approaches including innovative concepts based on semiconductors and superconductors.

  12. The effect of a diet containing grasshoppers and access to free-range on carcase and meat physicochemical and sensory characteristics in broilers.

    PubMed

    Sun, T; Long, R J; Liu, Z Y

    2013-01-01

    1. Research was conducted to evaluate the impact of a diet containing grasshoppers on the carcase, physicochemical and sensory characteristics in a free-range, grassland-based broiler production system. 2. A total of 80, 28-d-old male broilers were reared on grassland containing a large population of grasshoppers (treatment PB). Control birds were reared intensively on a maize-soybean diet (treatment CB). At 91 d of age, 24 birds from each treatment were slaughtered to evaluate carcase, meat and sensory characteristics. 3. Treatment PB produced birds with significantly lower live weights, breast, wing, thigh and drum weights, and higher dressing percentage and breast percentage of carcase, compared with CB. Treatment PB produced breast meat with significantly higher redness values, shear force and protein content, and lower pH values, cooking loss, moisture and fat content compared with CB. Sensory panel results for breast and thigh meats showed no treatment effect on colour and juiciness, but significantly higher scores for chewiness, flavour, aroma and overall appreciation, and lower scores for tenderness from treatment PB compared with CB. 4. Rearing chickens on rangeland may provide an alternative way to produce poultry meat which is considered superior by modern consumers.

  13. Comets at radio wavelengths

    NASA Astrophysics Data System (ADS)

    Crovisier, Jacques; Bockelée-Morvan, Dominique; Colom, Pierre; Biver, Nicolas

    2016-11-01

    Comets are considered as the most primitive objects in the Solar System. Their composition provides information on the composition of the primitive solar nebula, 4.6 Gyr ago. The radio domain is a privileged tool to study the composition of cometary ices. Observations of the OH radical at 18 cm wavelength allow us to measure the water production rate. A wealth of molecules (and some of their isotopologues) coming from the sublimation of ices in the nucleus have been identified by observations in the millimetre and submillimetre domains. We present an historical review on radio observations of comets, focusing on the results from our group, and including recent observations with the Nançay radio telescope, the IRAM antennas, the Odin satellite, the Herschel space observatory, ALMA, and the MIRO instrument aboard the Rosetta space probe. xml:lang="fr"

  14. Nonlinear-laser effects in NH4H2PO4 (ADP) and ND4D2PO4 (DADP) single crystals: almost two-octave multi-wavelength Stokes and anti-Stokes combs, cascaded lasing in UV and visible ranges with the involving of the second and third harmonic generation

    NASA Astrophysics Data System (ADS)

    Kaminskii, A. A.; Dolbinina, V. V.; Rhee, H.; Eichler, H. J.; Ueda, K.; Takaichi, K.; Shirakawa, A.; Tokurakawa, M.; Dong, J.; Jaque, D.

    2008-07-01

    We report the experimental investigation of nonlinear cascaded lasing χ(3) leftrightarrow χ(2) effects in UV and visible ranges and high-order Stokes and anti-Stokes generation covering spectral space of about 18000 cm-1 by stimulated Raman scattering and multi-wave mixing processes under one-micron picosecond pumping in the paraelectric state of NH4H2PO4 and ND4D2PO4 single crystals. All recorded Raman induced laser wavelengths are identified and attributed to their SRS-promoting vibration modes. Brief review of nonlinear-laser processes in non-centrosymmetric phosphates of KH2PO4-family and some physical properties of NH4H2PO4 and ND4D2PO4 are given as well.

  15. GHRS Ech-B Wavelength Monitor -- Cycle 4

    NASA Astrophysics Data System (ADS)

    Soderblom, David

    1994-01-01

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

  16. An integrated high-performance ratio-metric wavelength measurement device on glass

    NASA Astrophysics Data System (ADS)

    Wang, Gencheng; Yang, Bing; Shen, Ao; Pei, Chongyang; Yang, Longzhi; Yu, Hui; Jiang, Xiaoqing; Li, Yubo; Hao, Yinlei; Yang, Jianyi

    2015-10-01

    The measurable wavelength range and the resolution of the ratio-metric wavelength monitor are limited by each other in a conventional structure. To solve this problem we designed and fabricated a high-performance integrated double ratio-metric wavelength measurement device on glass by the method of ion-exchange. It consists of four unbalanced Mach-Zehnder interferometers (MZIs) to form a rough wavelength measurement with a wide range and a fine wavelength measurement with high resolution. The highest measured resolution can reach 10 pm in a 1.6 nm-wide wavelength range for the fine wavelength measurement together with a 45 nm-wide wavelength range for the rough measurement. By heating the unbalanced MZI, the performance of the fine wavelength monitor can be improved.

  17. Plasmonic All-Optical Tunable Wavelength Shifter

    SciTech Connect

    Flugel, B.; Macararenhas, A.; Snoke, D. W.; Pfeiffer, L. N.; West, K.

    2007-12-01

    At present, wavelength-division-multiplexed fibre lines routinely operate at 10 Gbit s{sup -1} per channel. The transition from static-path networks to true all-optical networks encompassing many nodes, in which channels are added/dropped and efficiently reassigned, will require improved tools for all-optical wavelength shifting. Specifically, one must be able to shift the carrier wavelength (frequency) of an optical data signal over tens of nanometres (a THz range) without the bottleneck of electrical conversion. Popular approaches to this problem make use of the nonlinear interaction between two wavelengths within a semiconductor optical amplifier whereas more novel methods invoke terahertz-frequency electro-optic modulation and polaritons. Here we outline the principles and demonstrate the use of optically excited plasmons as a tunable frequency source that can be mixed with a laser frequency through Raman scattering. The scheme is all-optical and enables dynamical control of the output carrier wavelength simply by varying the power of a control laser.

  18. Wavelength-conserving grating router for intermediate wavelength density

    DOEpatents

    Deri, Robert J.; Patel, Rajesh R.; Bond, Steven W.; Bennett, Cory V.

    2007-03-20

    A wavelength router to be used for fiber optical networking router is based on a diffraction grating which utilizes only N wavelengths to interconnect N inputs to N outputs. The basic approach is to augment the grating with additional couplers or wavelength selective elements so than N-1 of the 2N-1 outputs are combined with other N outputs (leaving only N outputs). One embodiment uses directional couplers as combiners. Another embodiment uses wavelength-selective couplers. Another embodiment uses a pair of diffraction gratings to maintain parallel propagation of all optical beams. Also, beam combining can be implemented either by using retroflection back through the grating pair or by using couplers.

  19. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Frequency and wavelength bands. (a) The radio spectrum shall be subdivided into nine frequency bands, which... 47 Telecommunication 1 2011-10-01 2011-10-01 false Frequency and wavelength bands. 2.101 Section 2... GHz: For frequencies above 10 500 MHz. Band number Symbols Frequency range (lower limit...

  20. Wavelength control of visible light laser diodes

    NASA Astrophysics Data System (ADS)

    Goto, N.; Fujii, T.; Nemoto, K.; Suzuki, H.; Nakagawa, K.; Otsu, M.

    1990-04-01

    Wavelength control of visible light laser diodes was studied. By combining an interferometer and a diffraction grating, it became possible to control the wavelength of continuous oscillation in the range of 664 to 673nm, the frequency fine control range being 2GHz. And the spectral linewidth was narrowed to about 44kHz (10 exp minus 7 nm). With the use of a collimator lens, the beam expansion was narrowed to 2mrad. It was confirmed that the pulse output of continuous oscillation visible light laser diodes can be amplified by the YAG laser excitation dye laser. In the case of pulse oscillation, oscillation of 1GHz spectral width was obtained at the wavelength of 0.8 micro m by using an injection synchronization method. In the injection synchronization method, other laser beam is injected in an oscillator and a superior laser beam of synchronized components alone is obtained. As the wavelength control method is now stabilized and satisfies the conditions of narrow band, it has the prospect to be applied to the laser uranium enrichment technology.

  1. Smoke optical depths - Magnitude, variability, and wavelength dependence

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Russell, P. B.; Colburn, D. A.; Ackerman, T. P.; Allen, D. A.

    1988-01-01

    An airborne autotracking sun-photometer has been used to measure magnitudes, temporal/spatial variabilities, and the wavelength dependence of optical depths in the near-ultraviolet to near-infrared spectrum of smoke from two forest fires and one jet fuel fire and of background air. Jet fuel smoke optical depths were found to be generally less wavelength dependent than background aerosol optical depths. Forest fire smoke optical depths, however, showed a wide range of wavelength depedences, such as incidents of wavelength-independent extinction.

  2. Broadband Wavelength Spanning Holographic Polymer Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Rai, Kashma; Shriyan, Sameet; Fontecchio, Adam

    2008-03-01

    Broadened interaction wavelength of holographic polymer dispersed liquid crystals (HPDLCs) have extensive applications in beam steering for instrument clusters, hyperspectral imaging, wavelength filtering and construction of lightweight optics. A novel simultaneous time and spatial multiplexing formation configuration is proposed here, to increase narrow wavelength reflecting notch to broad range wavelength spanning device. HPDLC films have electro-optic controllability by applying field. No moving parts, light weight, small footprint compared to prisms and lenses, high color purity make the broadband wavelength HPDLCs desirable for the above applications. Varying the incident laser beam exposure angles using motorized rotating stage, during formation is the key step here for their formation in a single medium. The fabricated broadband wavelength sensitive HPDLCs are characterized for the uniformity of the reflected peak and electro optic response. Their output wavefront is analyzed using wavefront analysis technique.

  3. Ultra-short wavelength operation of a thulium fibre laser in the 1660-1750 nm wavelength band.

    PubMed

    Daniel, J M O; Simakov, N; Tokurakawa, M; Ibsen, M; Clarkson, W A

    2015-07-13

    Ultra-short wavelength operation of a thulium fibre laser is investigated. Through use of core pumping and high feedback efficiency wavelength selection, a continuously-tunable fibre laser source operating from 1660 nm to 1720 nm is demonstrated in a silica host. We discuss the range of applications within this important wavelength band such as polymer materials processing and medical applications targeting characteristic C-H bond resonance peaks. As a demonstration of the power scalability of thulium fibre lasers in this band, fixed wavelength operation at 1726 nm with output power up 12.6 W and with slope efficiency > 60% is also shown. PMID:26191883

  4. The Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Taylor, G. B.

    2006-08-01

    The Long Wavelength Array (LWA) will be a new, open, user-oriented astronomical instrument operating in the poorly explored window from 20-80 MHz at arcsecond level resolution and mJy level sensitivity. Key science drivers include (1) acceleration, propagation, and turbulence in the ISM, including the space-distribution and spectrum of Galactic cosmic rays, supernova remnants, and pulsars; (2) the high redshift universe, including the most distant radio galaxies and clusters - tools for understanding the earliest black holes and the cosmological evolution of Dark Matter and Dark Energy; (3) planetary, solar, and space science, including space weather prediction and extra-solar planet searches; and (4) the radio transient universe: including the known (e.g., SNe, GRBs) and the unknown. Because the LWA will explore one of the last and least investigated regions of the spectrum, the potential for new discoveries, including new classes of physical phenomena, is high, and there is a strong synergy with exciting new X-ray and Gamma-ray measurements, e.g. for cosmic ray acceleration, transients, and galaxy clusters. Operated by the University of New Mexico on behalf of the South West Consortium (SWC) the LWA will also provide a unique training ground for the next generation of radio astronomers. Students may also put skills learned on the LWA to work in computer science, electrical engineering, and the communications industry, among others. The development of the LWA will follow a phased build, which benefits from lessons learned at each phase. Four university-based Scientific Testing and Evaluation (ST&E) teams with different areas of concentration (1. High resolution imaging and particle acceleration; 2. Wide field imaging and large scale structures; 3. Ionosphere, and 4. RFI suppression and transient detection) will provide the feedback needed to assure that science objectives are met as the build develops. Currently in its first year of construction funding, the LWA

  5. Source of coherent short wavelength radiation

    DOEpatents

    Villa, Francesco

    1990-01-01

    An apparatus for producing coherent radiation ranging from X-rays to the far ultraviolet (i.e., 1 Kev to 10 eV) utilizing the Compton scattering effect. A photon beam from a laser is scattered on a high energy electron bunch from a pulse power linac. The short wavelength radiation produced by such scattering has sufficient intensity and spatial coherence for use in high resolution applications such as microscopy.

  6. Radiative flux calculations at UV and visible wavelengths

    SciTech Connect

    Grossman, A.S.; Grant, K.E.; Wuebbles, D.J.

    1993-10-01

    A radiative transfer model to calculate the short wavelength fluxes at altitudes between 0 and 80 km has been developed at LLNL. The wavelength range extends from 175--735 nm. This spectral range covers the UV-B wavelength region, 250--350 nm, with sufficient resolution to allow comparison of UV-B measurements with theoretical predictions. Validation studies for the model have been made for both UV-B ground radiation calculations and tropospheric solar radiative forcing calculations for various ozone distributions. These studies indicate that the model produces results which agree well with respect to existing UV calculations from other published models.

  7. AWG Filter for Wavelength Interrogator

    NASA Technical Reports Server (NTRS)

    Black, Richard J. (Inventor); Costa, Joannes M. (Inventor); Faridian, Fereydoun (Inventor); Moslehi, Behzad (Inventor); Sotoudeh, Vahid (Inventor)

    2015-01-01

    A wavelength interrogator is coupled to a circulator which couples optical energy from a broadband source to an optical fiber having a plurality of sensors, each sensor reflecting optical energy at a unique wavelength and directing the reflected optical energy to an AWG. The AWG has a detector coupled to each output, and the reflected optical energy from each grating is coupled to the skirt edge response of the AWG such that the adjacent channel responses form a complementary pair response. The complementary pair response is used to convert an AWG skirt response to a wavelength.

  8. High-speed wavelength-swept lasers

    NASA Astrophysics Data System (ADS)

    Hsu, Kevin

    2006-05-01

    High-speed wavelength-swept lasers capable of providing wide frequency chirp and flexible temporal waveforms could enable numerous advanced functionalities for defense and security applications. Powered by high spectral intensity at rapid sweep rates across a wide wavelength range in each of the 1060nm, 1300nm, and 1550nm spectral windows, these swept-laser systems have demonstrated real-time monitoring and superior signal-to-noise ratio measurements in optical frequency domain imaging, fiber-optic sensor arrays, and near-IR spectroscopy. These same capabilities show promising potentials in laser radar and remote sensing applications. The core of the high-speed swept laser incorporates a semiconductor gain module and a high-performance fiber Fabry- Perot tunable filter (FFP-TF) to provide rapid wavelength scanning operations. This unique design embodies the collective advantages of the semiconductor amplifier's broad gain-bandwidth with direct modulation capability, and the FFP-TF's wide tuning ranges (>200nm), high finesse (1000 to 10,000), low-loss (<3dB), and fast scan rates reaching 20KHz. As a result, the laser can sweep beyond 100nm in 25μsec, output a scanning peak power near mW level, and exhibit excellent peak signal-to-spontaneous-emission ratio >80dB in static mode. When configured as a seed laser followed by post amplification, the swept spectrum and power can be optimized for Doppler ranging and remote sensing applications. Furthermore, when combined with a dispersive element, the wavelength sweep can be converted into high-speed and wide-angle spatial scanning without moving parts.

  9. Planarian Phototactic Assay Reveals Differential Behavioral Responses Based on Wavelength

    PubMed Central

    Paskin, Taylor R.; Jellies, John; Bacher, Jessica; Beane, Wendy S.

    2014-01-01

    Planarians are free-living aquatic flatworms that possess a well-documented photophobic response to light. With a true central nervous system and simple cerebral eyes (ocelli), planarians are an emerging model for regenerative eye research. However, comparatively little is known about the physiology of their photoreception or how their behavior is affected by various wavelengths. Most phototactic studies have examined planarian behavior using white light. Here, we describe a novel planarian behavioral assay to test responses to small ranges of visible wavelengths (red, blue, green), as well as ultraviolet (UV) and infrared (IR) which have not previously been examined. Our data show that planarians display behavioral responses across a range of wavelengths. These responses occur in a hierarchy, with the shortest wavelengths (UV) causing the most intense photophobic responses while longer wavelengths produce no effect (red) or an apparent attraction (IR). In addition, our data reveals that planarian photophobia is comprised of both a general photophobic response (that drives planarians to escape the light source regardless of wavelength) and wavelength-specific responses that encompass specific behavioral reactions to individual wavelengths. Our results serve to improve the understanding of planarian phototaxis and suggest that behavioral studies performed with white light mask a complex behavioral interaction with the environment. PMID:25493551

  10. Accessibility Videos.

    PubMed

    Kurppa, Ari; Nordlund, Marika

    2016-01-01

    It can be difficult to understand accessibility, if you do not have the personal experience. The Accessibility Centre ESKE produced short videos which demonstrate the meaning of accessibility in different situations. Videos will raise accessibility awareness of architects, other planners and professionals in the construction field and maintenance. PMID:27534282

  11. A color sensor wavelength meter

    NASA Astrophysics Data System (ADS)

    Durfee, Dallin; Jackson, Jarom; Otterstrom, Nils; Jones, Tyler; Archibald, James

    2016-05-01

    We will discuss a laser wavelength meter based on a commercial color sensor chip consisting of an array of photodiodes with different absorptive color filters. By comparing the relative amplitudes of light on the photodiodes, the wavelength of light can be determined with picometer-level precision and with picometer-scale calibration drift over a period longer than a month. This work was supported by NSF Grant Number PHY-1205736.

  12. Long Wavelength Ripples in the Nearshore

    NASA Astrophysics Data System (ADS)

    Alcinov, T.; Hay, A. E.

    2008-12-01

    Sediment bedforms are ubiquitous in the nearshore environment, and their characteristics and evolution have a direct effect on the hydrodynamics and the rate of sediment transport. The focus of this study is long wavelength ripples (LWR) observed at two locations in the nearshore at roughly 3m water depth under combined current and wave conditions in Duck, North Carolina. LWR are straight-crested bedforms with wavelengths in the range of 20-200cm, and steepness of about 0.1. They occur in the build up and decay of storms, in a broader range of values of the flow parameters compared to other ripple types. The main goal of the study is to test the maximum gross bedform-normal transport (mGBNT) hypothesis, which states that the orientation of ripples in directionally varying flows is such that the gross sediment transport normal to the ripple crest is maximized. Ripple wavelengths and orientation are measured from rotary fanbeam images and current and wave conditions are obtained from electromagnetic (EM) flowmeters and an offshore pressure gauge array. Preliminary tests in which transport direction is estimated from the combined flow velocity vectors indicate that the mGBNT is not a good predictor of LWR orientation. Results from tests of the mGBNT hypothesis using a sediment transport model will be presented.

  13. Towards short wavelengths FELs workshop

    SciTech Connect

    Ben-Zvi, I.; Winick, H.

    1993-12-01

    This workshop was caged because of the growing perception in the FEL source community that recent advances have made it possible to extend FEL operation to wavelengths about two orders of magnitude shorter than the 240 nm that has been achieved to date. In addition short wavelength FELs offer the possibilities of extremely high peak power (several gigawatts) and very short pulses (of the order of 100 fs). Several groups in the USA are developing plans for such short wavelength FEL facilities. However, reviewers of these plans have pointed out that it would be highly desirable to first carry out proof-of-principle experiments at longer wavelengths to increase confidence that the shorter wavelength devices will indeed perform as calculated. The need for such experiments has now been broadly accepted by the FEL community. Such experiments were the main focus of this workshop as described in the following objectives distributed to attendees: (1) Define measurements needed to gain confidence that short wavelength FELs will perform as calculated. (2) List possible hardware that could be used to carry out these measurements in the near term. (3) Define a prioritized FEL physics experimental program and suggested timetable. (4) Form collaborative teams to carry out this program.

  14. Evaluation of wavelength groups for discrimination of agricultural cover types

    NASA Technical Reports Server (NTRS)

    Kumar, R.

    1978-01-01

    Multispectral scanner data in twelve spectral channels, in the wavelength range 0.46 to 11.7 microns, acquired in July, 1971, for three flightlines, were analyzed by applying automatic pattern recognition techniques. These twelve spectral channels were divided into four wavelength groups (W1, W2, W3 and W4), each consisting of three wavelength groups - with respect to their estimated probability of correct classification (Pc) - in discriminating agricultural cover types. The same analysis was also done for the data acquired in August, to investigate the effect of time on these results. The effect of deletion of each of the wavelength groups on Pc, in the subsets of one to nine channels, is given. Values of Pc for all possible combinations of wavelength groups, in the subsets of one to eleven channels, are also given.

  15. Middle infrared (wavelength range: 8 μm-14 μm) 2-dimensional spectroscopy (total weight with electrical controller: 1.7 kg, total cost: less than 10,000 USD) so-called hyperspectral camera for unmanned air vehicles like drones

    NASA Astrophysics Data System (ADS)

    Yamamoto, Naoyuki; Saito, Tsubasa; Ogawa, Satoru; Ishimaru, Ichiro

    2016-05-01

    We developed the palm size (optical unit: 73[mm]×102[mm]×66[mm]) and light weight (total weight with electrical controller: 1.7[kg]) middle infrared (wavelength range: 8[μm]-14[μm]) 2-dimensional spectroscopy for UAV (Unmanned Air Vehicle) like drone. And we successfully demonstrated the flights with the developed hyperspectral camera mounted on the multi-copter so-called drone in 15/Sep./2015 at Kagawa prefecture in Japan. We had proposed 2 dimensional imaging type Fourier spectroscopy that was the near-common path temporal phase-shift interferometer. We install the variable phase shifter onto optical Fourier transform plane of infinity corrected imaging optical systems. The variable phase shifter was configured with a movable mirror and a fixed mirror. The movable mirror was actuated by the impact drive piezo-electric device (stroke: 4.5[mm], resolution: 0.01[μm], maker: Technohands Co.,Ltd., type:XDT50-45, price: around 1,000USD). We realized the wavefront division type and near common path interferometry that has strong robustness against mechanical vibrations. Without anti-mechanical vibration systems, the palm-size Fourier spectroscopy was realized. And we were able to utilize the small and low-cost middle infrared camera that was the micro borometer array (un-cooled VOxMicroborometer, pixel array: 336×256, pixel pitch: 17[μm], frame rate 60[Hz], maker: FLIR, type: Quark 336, price: around 5,000USD). And this apparatus was able to be operated by single board computer (Raspberry Pi.). Thus, total cost was less than 10,000 USD. We joined with KAMOME-PJ (Kanagawa Advanced MOdule for Material Evaluation Project) with DRONE FACTORY Corp., KUUSATSU Corp., Fuji Imvac Inc. And we successfully obtained the middle infrared spectroscopic imaging with multi-copter drone.

  16. Systematic wavelength selection for improved multivariate spectral analysis

    DOEpatents

    Thomas, Edward V.; Robinson, Mark R.; Haaland, David M.

    1995-01-01

    Methods and apparatus for determining in a biological material one or more unknown values of at least one known characteristic (e.g. the concentration of an analyte such as glucose in blood or the concentration of one or more blood gas parameters) with a model based on a set of samples with known values of the known characteristics and a multivariate algorithm using several wavelength subsets. The method includes selecting multiple wavelength subsets, from the electromagnetic spectral region appropriate for determining the known characteristic, for use by an algorithm wherein the selection of wavelength subsets improves the model's fitness of the determination for the unknown values of the known characteristic. The selection process utilizes multivariate search methods that select both predictive and synergistic wavelengths within the range of wavelengths utilized. The fitness of the wavelength subsets is determined by the fitness function F=.function.(cost, performance). The method includes the steps of: (1) using one or more applications of a genetic algorithm to produce one or more count spectra, with multiple count spectra then combined to produce a combined count spectrum; (2) smoothing the count spectrum; (3) selecting a threshold count from a count spectrum to select these wavelength subsets which optimize the fitness function; and (4) eliminating a portion of the selected wavelength subsets. The determination of the unknown values can be made: (1) noninvasively and in vivo; (2) invasively and in vivo; or (3) in vitro.

  17. Nonstoichiometric Laser Materials: Designer Wavelengths in Neodymium Doped Garnets

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.; Barnes, Norman P.

    2008-01-01

    The tunable nature of lasers provides for a wide range of applications. Most applications rely on finding available laser wavelengths to meet the needs of the research. This article presents the concept of compositional tuning, whereby the laser wavelength is designed by exploiting nonstoichiometry. For research where precise wavelengths are required, such as remote sensing, this is highly advantageous. A theoretical basis for the concept is presented and experimental results in spectroscopic measurements support the theoretical basis. Laser operation nicely demonstrates the validity of the concept of designer lasers.

  18. Free-space wavelength-multiplexed optical scanner.

    PubMed

    Yaqoob, Z; Rizvi, A A; Riza, N A

    2001-12-10

    A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large- diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan range for a given diffraction order and grating period. Limitations include beam-spreading effects based on the varying scanner aperture sizes and the instantaneous information bandwidth of the data-carrying laser beam.

  19. Free-space wavelength-multiplexed optical scanner.

    PubMed

    Yaqoob, Z; Rizvi, A A; Riza, N A

    2001-12-10

    A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large- diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan range for a given diffraction order and grating period. Limitations include beam-spreading effects based on the varying scanner aperture sizes and the instantaneous information bandwidth of the data-carrying laser beam. PMID:18364951

  20. Access to modern contraception.

    PubMed

    Welsh, Michael J; Stanback, John; Shelton, James

    2006-06-01

    Access to modern contraception has become a recognized human right, improving the health and well-being of women, families and societies worldwide. However, contraceptive access remains uneven. Irregular contraceptive supply, limited numbers of service delivery points and specific geographic, economic, informational, psychosocial and administrative barriers (including medical barriers) undermine access in many settings. Widening the range of providers enabled to offer contraception can improve contraceptive access, particularly where resources are most scarce. International efforts to remove medical barriers include the World Health Organization's Medical Eligibility Criteria. Based on the best available evidence, these criteria provide guidance for weighing the risks and benefits of contraceptive choice among women with specific clinical conditions. Clinical job aids can also improve access. More research is needed to further elucidate the pathways for expanding contraceptive access. Further progress in removing medical barriers will depend on systems for improving provider education and promoting evidence-based contraceptive service delivery. PMID:16443395

  1. Sub-wavelength plasmon laser

    DOEpatents

    Bora, Mihail; Bond, Tiziana C.

    2016-04-19

    A plasmonic laser device has resonant nanocavities filled with a gain medium containing an organic dye. The resonant plasmon frequencies of the nanocavities are tuned to align with both the absorption and emission spectra of the dye. Variables in the system include the nature of the dye and the wavelength of its absorption and emission, the wavelength of the pumping radiation, and the resonance frequencies of the nanocavities. In addition the pumping frequency of the dye is selected to be close to the absorption maximum.

  2. Integration of both dense wavelength-division multiplexing and coarse wavelength-division multiplexing demultiplexer on one photonic crystal chip

    NASA Astrophysics Data System (ADS)

    Tian, Huiping; Shen, Guansheng; Liu, Weijia; Ji, Yuefeng

    2013-07-01

    An integrated model of photonic crystal (PC) demultiplexer that can be used to combine dense wavelength-division multiplexing (DWDM) and coarse wavelength-division multiplexing (CWDM) systems is first proposed. By applying the PC demultiplexer, dense channel spacing 0.8 nm and coarse channel spacing 20 nm are obtained at the same time. The transmission can be improved to nearly 90%, and the crosstalk can be decreased to less than -18 dB by enlarging the width of the bus waveguide. The total size of the device is 21×42 μm2. Four channels on one side of the demultiplexer can achieve DWDM in the wavelength range between 1575 and 1578 nm, and the other four channels on the other side can achieve CWDM in the wavelength range between 1490 and 1565 nm, respectively. The demonstrated demultiplexer can be applied in the future CWDM and DWDM system, and the architecture costs can be significantly reduced.

  3. Interferometric Sensor of Wavelength Detuning Using a Liquid Crystalline Polymer Waveplate.

    PubMed

    Wierzba, Paweł

    2016-01-01

    Operation of a polarization interferometer for measurement of the wavelength changes of a tunable semiconductor laser was investigated. A λ/8 waveplate made from liquid crystalline polymer is placed in one of interferometers' arms in order to generate two output signals in quadrature. Wavelength was measured with resolution of 2 pm in the wavelength range 628-635 nm. Drift of the interferometer, measured in the period of 500 s, was 8 nm, which corresponded to the change in the wavelength of 1.3 pm. If needed, wavelength-dependent Heydemann correction can be used to expand the range of operation of such interferometer. PMID:27171082

  4. Interferometric Sensor of Wavelength Detuning Using a Liquid Crystalline Polymer Waveplate

    PubMed Central

    Wierzba, Paweł

    2016-01-01

    Operation of a polarization interferometer for measurement of the wavelength changes of a tunable semiconductor laser was investigated. A λ/8 waveplate made from liquid crystalline polymer is placed in one of interferometers’ arms in order to generate two output signals in quadrature. Wavelength was measured with resolution of 2 pm in the wavelength range 628–635 nm. Drift of the interferometer, measured in the period of 500 s, was 8 nm, which corresponded to the change in the wavelength of 1.3 pm. If needed, wavelength-dependent Heydemann correction can be used to expand the range of operation of such interferometer. PMID:27171082

  5. High performance optical wavelength multiplexer-demultiplexer.

    PubMed

    Dobrowolski, J A; Hara, E H; Sullivan, B T; Waldorf, A J

    1992-07-01

    The principle of an optical wavelength multiplexer-demultiplexer is described in which the signals undergo repeated reflections from special filter elements that can be designed for a wide range of cross-talk ratios. The insertion losses of these units can be quite small and they can be implemented to provide simultaneous multichannel two-way transmission. In a preliminary investigation of an experimental prototype an insertion loss of 0.5 dB and a cross talk of -35 dB were demonstrated. The multiplexer-demultiplexer is expected to have a long life and high reliability.

  6. Quantum cascade lasers designed toward shorter wavelengths

    NASA Astrophysics Data System (ADS)

    Xu, Jilian; Liu, Lei; Li, Bing Hui; Zhang, Zhenzhong; Ma, Jian; Liu, Kewei; He, Jun; Shen, D. Z.

    2016-02-01

    Quantum cascade lasers (QCLs) are normally based on one-dimensional confined quantum wells. In this scheme, it is still a challenge to produce lasing with a frequency higher than mid-infrared. Here, we discuss the possibility to extend the spectral range of QCLs to the higher frequency region by adding another dimensional confinement. Taking the ZnO/MgO system as an example, we demonstrate theoretically that such a two-dimensional confined QCL can operate at wavelengths from the near-infrared λ =2.95 μm, 1.57 μm, 1.13 μm to the visible 734 nm.

  7. Quantum cascade lasers designed toward shorter wavelengths.

    PubMed

    Xu, Jilian; Liu, Lei; Li, Bing Hui; Zhang, Zhenzhong; Ma, Jian; Liu, Kewei; He, Jun; Shen, D Z

    2016-02-17

    Quantum cascade lasers (QCLs) are normally based on one-dimensional confined quantum wells. In this scheme, it is still a challenge to produce lasing with a frequency higher than mid-infrared. Here, we discuss the possibility to extend the spectral range of QCLs to the higher frequency region by adding another dimensional confinement. Taking the ZnO/MgO system as an example, we demonstrate theoretically that such a two-dimensional confined QCL can operate at wavelengths from the near-infrared [Formula: see text] μm, 1.57 μm, 1.13 μm to the visible 734 nm.

  8. Wavelength-modulated photocapacitance spectroscopy

    NASA Technical Reports Server (NTRS)

    Kamieniecki, E.; Lagowski, J.; Gatos, H. C.

    1980-01-01

    Derivative deep-level spectroscopy was achieved with wavelength-modulated photocapacitance employing MOS structures and Schottky barriers. The energy position and photoionization characteristics of deep levels of melt-grown GaAs and the Cr level in high-resistivity GaAs were determined. The advantages of this method over existing methods for deep-level spectroscopy are discussed.

  9. Solid colloidal optical wavelength filter

    DOEpatents

    Alvarez, Joseph L.

    1992-01-01

    A solid colloidal optical wavelength filter includes a suspension of spheal particles dispersed in a coagulable medium such as a setting plastic. The filter is formed by suspending spherical particles in a coagulable medium; agitating the particles and coagulable medium to produce an emulsion of particles suspended in the coagulable medium; and allowing the coagulable medium and suspended emulsion of particles to cool.

  10. Wavelength-shifted Cherenkov radiators

    NASA Technical Reports Server (NTRS)

    Krider, E. P.; Jacobson, V. L.; Pifer, A. E.; Polakos, P. A.; Kurz, R. J.

    1976-01-01

    The scintillation and Cherenkov responses of plastic Cherenkov radiators containing different wavelength-shifting fluors in varying concentrations have been studied in beams of low energy protons and pions. For cosmic ray applications, where large Cherenkov to scintillation ratios are desired, the optimum fluor concentrations are 0.000025 by weight or less.

  11. Web Accessibility and Accessibility Instruction

    ERIC Educational Resources Information Center

    Green, Ravonne A.; Huprich, Julia

    2009-01-01

    Section 508 of the Americans with Disabilities Act (ADA) mandates that programs and services be accessible to people with disabilities. While schools of library and information science (SLIS*) and university libraries should model accessible Web sites, this may not be the case. This article examines previous studies about the Web accessibility of…

  12. Dynamic sensor interrogation using wavelength-swept laser with a polygon-scanner-based wavelength filter.

    PubMed

    Kwon, Yong Seok; Ko, Myeong Ock; Jung, Mi Sun; Park, Ik Gon; Kim, Namje; Han, Sang-Pil; Ryu, Han-Cheol; Park, Kyung Hyun; Jeon, Min Yong

    2013-07-29

    We report a high-speed (~2 kHz) dynamic multiplexed fiber Bragg grating (FBG) sensor interrogation using a wavelength-swept laser (WSL) with a polygon-scanner-based wavelength filter. The scanning frequency of the WSL is 18 kHz, and the 10 dB scanning bandwidth is more than 90 nm around a center wavelength of 1,540 nm. The output from the WSL is coupled into the multiplexed FBG array, which consists of five FBGs. The reflected Bragg wavelengths of the FBGs are 1,532.02 nm, 1,537.84 nm, 1,543.48 nm, 1,547.98 nm, and 1,553.06 nm, respectively. A dynamic periodic strain ranging from 500 Hz to 2 kHz is applied to one of the multiplexed FBGs, which is fixed on the stage of the piezoelectric transducer stack. Good dynamic performance of the FBGs and recording of their fast Fourier transform spectra have been successfully achieved with a measuring speed of 18 kHz. The signal-to-noise ratio and the bandwidth over the whole frequency span are determined to be more than 30 dB and around 10 Hz, respectively. We successfully obtained a real-time measurement of the abrupt change of the periodic strain. The dynamic FBG sensor interrogation system can be read out with a WSL for high-speed and high-sensitivity real-time measurement.

  13. Dynamic Sensor Interrogation Using Wavelength-Swept Laser with a Polygon-Scanner-Based Wavelength Filter

    PubMed Central

    Kwon, Yong Seok; Ko, Myeong Ock; Jung, Mi Sun; Park, Ik Gon; Kim, Namje; Han, Sang-Pil; Ryu, Han-Cheol; Park, Kyung Hyun; Jeon, Min Yong

    2013-01-01

    We report a high-speed (∼2 kHz) dynamic multiplexed fiber Bragg grating (FBG) sensor interrogation using a wavelength-swept laser (WSL) with a polygon-scanner-based wavelength filter. The scanning frequency of the WSL is 18 kHz, and the 10 dB scanning bandwidth is more than 90 nm around a center wavelength of 1,540 nm. The output from the WSL is coupled into the multiplexed FBG array, which consists of five FBGs. The reflected Bragg wavelengths of the FBGs are 1,532.02 nm, 1,537.84 nm, 1,543.48 nm, 1,547.98 nm, and 1,553.06 nm, respectively. A dynamic periodic strain ranging from 500 Hz to 2 kHz is applied to one of the multiplexed FBGs, which is fixed on the stage of the piezoelectric transducer stack. Good dynamic performance of the FBGs and recording of their fast Fourier transform spectra have been successfully achieved with a measuring speed of 18 kHz. The signal-to-noise ratio and the bandwidth over the whole frequency span are determined to be more than 30 dB and around 10 Hz, respectively. We successfully obtained a real-time measurement of the abrupt change of the periodic strain. The dynamic FBG sensor interrogation system can be read out with a WSL for high-speed and high-sensitivity real-time measurement. PMID:23899934

  14. Dynamic sensor interrogation using wavelength-swept laser with a polygon-scanner-based wavelength filter.

    PubMed

    Kwon, Yong Seok; Ko, Myeong Ock; Jung, Mi Sun; Park, Ik Gon; Kim, Namje; Han, Sang-Pil; Ryu, Han-Cheol; Park, Kyung Hyun; Jeon, Min Yong

    2013-01-01

    We report a high-speed (~2 kHz) dynamic multiplexed fiber Bragg grating (FBG) sensor interrogation using a wavelength-swept laser (WSL) with a polygon-scanner-based wavelength filter. The scanning frequency of the WSL is 18 kHz, and the 10 dB scanning bandwidth is more than 90 nm around a center wavelength of 1,540 nm. The output from the WSL is coupled into the multiplexed FBG array, which consists of five FBGs. The reflected Bragg wavelengths of the FBGs are 1,532.02 nm, 1,537.84 nm, 1,543.48 nm, 1,547.98 nm, and 1,553.06 nm, respectively. A dynamic periodic strain ranging from 500 Hz to 2 kHz is applied to one of the multiplexed FBGs, which is fixed on the stage of the piezoelectric transducer stack. Good dynamic performance of the FBGs and recording of their fast Fourier transform spectra have been successfully achieved with a measuring speed of 18 kHz. The signal-to-noise ratio and the bandwidth over the whole frequency span are determined to be more than 30 dB and around 10 Hz, respectively. We successfully obtained a real-time measurement of the abrupt change of the periodic strain. The dynamic FBG sensor interrogation system can be read out with a WSL for high-speed and high-sensitivity real-time measurement. PMID:23899934

  15. Long wavelength vertical-cavity light-emitting devices

    NASA Astrophysics Data System (ADS)

    Christenson, Gina Lee

    Long wavelength tunable transmitters are essential in the field of optical communications. Wavelength control and cost reduction are very important issues, especially in applications such as wavelength division multiplexing (WDM) networks, where several closely spaced wavelengths are transmitted and processed simultaneously. This thesis introduces a transmitter design that can alleviate these problems. This work involves the development, fabrication, and characterization of a narrowband tunable resonant cavity light-emitting diode (LED). The emission is centered at 1.51 mum, an important wavelength for optical communications. The linewidth is only 4 nm and the tuning range covers 75 nm. Wafer bonding and surface micromachining techniques have been integrated in the design to produce a structure that combines the assets of each technology. Wafer bonding is used to build the base for a vertical cavity surface emitting laser (VCSEL) structure, which is composed of an InP-based active layer on a GaAs-based mirror. Surface micromachining is then used to fabricate the suspended top mirror of the VCSEL, in place of the traditional top mirror that is grown directly on the VCSEL structure. The suspended mirror moves towards the substrate with the application of a voltage, thus changing the Fabry-Perot cavity length and providing the wavelength tunability of the device. This transmitter design relaxes the need for preset wavelengths in VCSEL processing by allowing the user to adjust the central wavelength after processing. Arrays of transmitters with identical wavelengths for high power applications or with gradually decreasing emission wavelengths across a wafer can also be achieved. The tunability of the devices allows for real time wavelength monitoring and tracking to ensure stability of the wavelengths with temperature or environmental changes, as well as compensating for shifts in wavelength due to degradation of the devices over time. Due to the monolithic, vertical

  16. Using Dual-wavelength Fiber Bragg Gratings for Temperature and Strain Sensing at Cryogenic Temperature

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.; Rogowski, Robert S.; DeHaven, Stanton L.

    2003-01-01

    By using dual-wavelength fiber-optic Bragg gratings, a new technique has been developed for sensing both temperature and strain simultaneously in cryogenic temperature range. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a dual-wavelength sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. These coefficients were used to construct the elements of the K matrix, which enables to determine inversely the strain and temperature changes by measuring the wavelength shifts of the dual-wavelength Bragg grating. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found from about 70 K to 140 K. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. Several alternatives are proposed to resolve this problem. The effectiveness and sensitivities of these measurements in different temperature ranges are discussed. The separation of two wavelengths for the dual-wavelength Bragg grating has been widened to increase the sensitivities of measurement; however, this separation can still be covered in the scanning range from single scanning laser.

  17. Short-wavelength ablation of solids: pulse duration and wavelength effects

    NASA Astrophysics Data System (ADS)

    Juha, Libor; Bittner, Michal; Chvostova, Dagmar; Letal, Vit; Krasa, Josef; Otcenasek, Zdenek; Kozlova, Michaela; Polan, Jiri; Prag, Ansgar R.; Rus, Bedrich; Stupka, Michal; Krzywinski, Jacek; Andrejczuk, Andrzej; Pelka, Jerzy B.; Sobierajski, Ryszard H.; Ryc, Leszek; Feldhaus, Josef; Boody, Frederick P.; Fiedorowicz, Henryk; Bartnik, Andrzej; Mikolajczyk, Janusz; Rakowski, Rafal; Kubat, P.; Pina, Ladislav; Grisham, Michael E.; Vaschenko, Georgiy O.; Menoni, Carmen S.; Rocca, Jorge J. G.

    2004-11-01

    For conventional wavelength (UV-Vis-IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, ablation (etch) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various short-wavelength (l < 100 nm) lasers emitting pulses with durations ranging from ~ 10 fs to ~ 1 ns have recently been put into a routine operation. This makes it possible to investigate how the ablation characteristics depend on the pulse duration in the XUV spectral region. 1.2-ns pulses of 46.9-nm radiation delivered from a capillary-discharge Ne-like Ar laser (Colorado State University, Fort Collins), focused by a spherical Sc/Si multilayer-coated mirror were used for an ablation of organic polymers and silicon. Various materials were irradiated with ellipsoidal-mirror-focused XUV radiation (λ = 86 nm, τ = 30-100 fs) generated by the free-electron laser (FEL) operated at the TESLA Test Facility (TTF1 FEL) in Hamburg. The beam of the Ne-like Zn XUV laser (λ = 21.2 nm, τ < 100 ps) driven by the Prague Asterix Laser System (PALS) was also successfully focused by a spherical Si/Mo multilayer-coated mirror to ablate various materials. Based on the results of the experiments, the etch rates for three different pulse durations are compared using the XUV-ABLATOR code to compensate for the wavelength difference. Comparing the values of etch rates calculated for short pulses with those measured for ultrashort pulses, we can study the influence of pulse duration on XUV ablation efficiency. Ablation efficiencies measured with short pulses at various wavelengths (i.e. 86/46.9/21.2 nm from the above-mentioned lasers and ~ 1 nm from the double stream gas-puff Xe plasma source driven by PALS) show that the wavelength influences the etch rate mainly through the different attenuation lengths.

  18. Laser wavelengths and oral implantology.

    PubMed

    Romanos, George E; Gutknecht, Norbert; Dieter, Sandra; Schwarz, Frank; Crespi, Roberto; Sculean, Anton

    2009-11-01

    In modern implant dentistry there are several clinical indications for laser surgery. Different laser systems have a considerable spectrum of application in soft and hard peri-implant tissues. The literature was searched for clinical application of different laser wavelengths in peri-implant tissues: second-stage surgery of submerged implants, treatment of infrabony defects, removal of peri-implant hyperplastic overgrowths, and, possibly, the preparation of bone cavities for implant placement. This report describes the state-of-the-art application of different laser systems in modern implant dentistry for the treatment of peri-implant lesions and decontamination of implant surfaces. Our study evaluated in vitro examinations, clinical experience and long-term clinical studies. The exact selection of the appropriate laser system and wavelength was dependent on the scientific evaluation of recent literature and the level of changes in implant and tissue temperatures during laser application. The significant reduction in bacteria on the implant surface and the peri-implant tissues during irradiation and the cutting effects associated with the coagulation properties of the lasers are the main reasons for laser application in the treatment of peri-implant lesions and the successful long-term prognosis of failing oral implants. The various applications of lasers in implant dentistry are dependent on the wavelength and laser-tissue interactions.

  19. Wavelength stabilized multi-kW diode laser systems

    NASA Astrophysics Data System (ADS)

    Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens

    2015-03-01

    We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.

  20. New scheme of variable optical buffer for IP packets used in access control of HORNET

    NASA Astrophysics Data System (ADS)

    Fang, Nian; Wang, Lutang; Huang, Zhaoming

    2002-09-01

    A new scheme of variable optical buffer for IP packets is reported. It may be used in access control of HORNET (Hybrid Optoelectronic Ring NETwork), to avoid collision of added packet and the packet already on the ring and improve the loss ratio of the packets. In this scheme, a new multi-wavelength fiber loop memory technique is employed. This architecture uses the wavelength converter (WC) to specify the packets delay and wavelength conversion is accomplished by the technique of four-wave-mixing (FWM) with a semiconductor optical amplifier (SOA). The range of delay is 10 to 9990 bytes periods. First, architecture, operation principle, characteristics and applications of this scheme of variable optical buffer are introduced. Next, a new unslotted CSMA/CA MAC scheme based on the variable optical buffer is briefly introduced too. Finally, the simulation results are presented.

  1. Access Denied

    ERIC Educational Resources Information Center

    Villano, Matt

    2008-01-01

    Building access control (BAC)--a catchall phrase to describe the systems that control access to facilities across campus--has traditionally been handled with remarkably low-tech solutions: (1) manual locks; (2) electronic locks; and (3) ID cards with magnetic strips. Recent improvements have included smart cards and keyless solutions that make use…

  2. Open Access

    ERIC Educational Resources Information Center

    Suber, Peter

    2012-01-01

    The Internet lets us share perfect copies of our work with a worldwide audience at virtually no cost. We take advantage of this revolutionary opportunity when we make our work "open access": digital, online, free of charge, and free of most copyright and licensing restrictions. Open access is made possible by the Internet and copyright-holder…

  3. Design, demonstration and analysis of a modified wavelength-correlating receiver for incoherent OCDMA system.

    PubMed

    Zhou, Heng; Qiu, Kun; Wang, Leyang

    2011-03-28

    A novel wavelength-correlating receiver for incoherent Optical Code Division Multiple Access (OCDMA) system is proposed and demonstrated in this paper. Enabled by the wavelength conversion based scheme, the proposed receiver can support various code types including one-dimensional optical codes and time-spreading/wavelength-hopping two dimensional codes. Also, a synchronous detection scheme with time-to- wavelength based code acquisition is proposed, by which code acquisition time can be substantially reduced. Moreover, a novel data-validation methodology based on all-optical pulse-width monitoring is introduced for the wavelength-correlating receiver. Experimental demonstration of the new proposed receiver is presented and low bit error rate data-receiving is achieved without optical hard limiting and electronic power thresholding. For the first time, a detailed theoretical performance analysis specialized for the wavelength-correlating receiver is presented. Numerical results show that the overall performance of the proposed receiver prevails over conventional OCDMA receivers.

  4. Effect of wavelength on cutaneous pigment using pulsed irradiation

    SciTech Connect

    Sherwood, K.A.; Murray, S.; Kurban, A.K.; Tan, O.T.

    1989-05-01

    Several reports have been published over the last two decades describing the successful removal of benign cutaneous pigmented lesions such as lentigines, cafe au lait macules' nevi, nevus of Ota, and lentigo maligna by a variety of lasers such as the excimer (351 nm), argon (488,514 nm), ruby (694 nm), Nd:YAG (1060 nm), and CO/sub 2/ (10,600 nm). Laser treatment has been applied to lesions with a range of pigment depths from superficial lentigines in the epidermis to the nevus of Ota in the reticular dermis. Widely divergent laser parameters of wavelength, pulse duration, energy density, and spotsizes have been used, but the laser parameters used to treat this range of lesions have been arbitrary, with little effort focused on defining optimal laser parameters for removal of each type. In this study, miniature black pig skin was exposed to five wavelengths (504, 590, 694, 720, and 750 nm) covering the absorption spectrum of melanin. At each wavelength, a range of energy densities was examined. Skin biopsies taken from laser-exposed sites were examined histologically in an attempt to establish whether optimal laser parameters exist for destroying pigment cells in skin. Of the five wavelengths examined, 504 nm produced the most pigment specific injury; this specificity being maintained even at the highest energy density of 7.0 J/cm2. Thus, for the destruction of melanin-containing cells in the epidermal compartment, 504 nm wavelength appears optimal.

  5. Wavelength-selective orbital-angular-momentum beam generation using MEMS tunable Fabry-Perot filter.

    PubMed

    Paul, Sujoy; Lyubopytov, Vladimir S; Schumann, Martin F; Cesar, Julijan; Chipouline, Arkadi; Wegener, Martin; Küppers, Franko

    2016-07-15

    We demonstrate an on-chip device capable of wavelength-selective generation of vortex beams, which is realized by a spiral phase plate integrated onto a microelectromechanical system (MEMS) tunable filter. This vortex MEMS filter, being capable of functioning simultaneously in both wavelength and orbital-angular-momentum (OAM) domains at the 1550 nm wavelength regime, is considered as a compact, robust, and cost-effective solution for simultaneous OAM- and wavelength-division multiplexed optical communications. The experimental OAM spectra for azimuthal orders 1, 2, and 3 show an OAM state purity >92% across a wavelength range of more than 30 nm. PMID:27420507

  6. Wavelength-selective orbital-angular-momentum beam generation using MEMS tunable Fabry-Perot filter.

    PubMed

    Paul, Sujoy; Lyubopytov, Vladimir S; Schumann, Martin F; Cesar, Julijan; Chipouline, Arkadi; Wegener, Martin; Küppers, Franko

    2016-07-15

    We demonstrate an on-chip device capable of wavelength-selective generation of vortex beams, which is realized by a spiral phase plate integrated onto a microelectromechanical system (MEMS) tunable filter. This vortex MEMS filter, being capable of functioning simultaneously in both wavelength and orbital-angular-momentum (OAM) domains at the 1550 nm wavelength regime, is considered as a compact, robust, and cost-effective solution for simultaneous OAM- and wavelength-division multiplexed optical communications. The experimental OAM spectra for azimuthal orders 1, 2, and 3 show an OAM state purity >92% across a wavelength range of more than 30 nm.

  7. Experimental demonstration of a low-cost tunable semiconductor DFB laser for access networks

    NASA Astrophysics Data System (ADS)

    Li, Lianyan; Tang, Song; Huang, Long; Zhang, Tingting; Li, Simin; Shi, Yuechun; Chen, Xiangfei

    2014-09-01

    A low-cost tunable semiconductor distributed feedback (DFB) laser design in access networks is proposed and experimentally demonstrated. It covers 9 nm continuous tuning range by changing the temperature. The side mode suppression ratios are above 42 dB over the tuning range. The current and temperature coefficients of wavelength tuning are 0.0124 nm mA-1 and 0.0875 nm °C, respectively. The results indicate that the reconstruction-equivalent-chirp (REC) technique is promising to fabricate low-cost tunable DFB lasers meeting the requirement of wavelength-division-multiplexing passive optical networks (WDM-PONs). It should be also noted that the tuning range can be easily extended by using more sections.

  8. Note: Laser wavelength precision measurement based on a laser synthetic wavelength interferometer

    NASA Astrophysics Data System (ADS)

    Yan, Liping; Chen, Benyong; Zhang, Shihua; Liu, Pengpeng; Zhang, Enzheng

    2016-08-01

    A laser wavelength precision measurement method is presented based on the laser synthetic wavelength interferometer (LSWI). According to the linear relation between the displacements of measurement and reference arms in the interferometer, the synthetic wavelength produced by an unknown wavelength and a reference wavelength can be measured by detecting the phase coincidences of two interference signals. The advantage of the method is that a larger synthetic wavelength resulting from an unknown wavelength very close to the reference wavelength can be easily determined according to the linear relation in the interferometer. Then the unknown wavelength is derived according to the one-to-one corresponding relationship between single wavelength and synthetic wavelength. Wavelengths of an external cavity diode laser and two He-Ne lasers were determined experimentally. The experimental results show that the proposed method is able to realize a relative uncertainty on the order of 10-8.

  9. Note: Laser wavelength precision measurement based on a laser synthetic wavelength interferometer.

    PubMed

    Yan, Liping; Chen, Benyong; Zhang, Shihua; Liu, Pengpeng; Zhang, Enzheng

    2016-08-01

    A laser wavelength precision measurement method is presented based on the laser synthetic wavelength interferometer (LSWI). According to the linear relation between the displacements of measurement and reference arms in the interferometer, the synthetic wavelength produced by an unknown wavelength and a reference wavelength can be measured by detecting the phase coincidences of two interference signals. The advantage of the method is that a larger synthetic wavelength resulting from an unknown wavelength very close to the reference wavelength can be easily determined according to the linear relation in the interferometer. Then the unknown wavelength is derived according to the one-to-one corresponding relationship between single wavelength and synthetic wavelength. Wavelengths of an external cavity diode laser and two He-Ne lasers were determined experimentally. The experimental results show that the proposed method is able to realize a relative uncertainty on the order of 10(-8). PMID:27587172

  10. Coherence techniques at extreme ultraviolet wavelengths

    SciTech Connect

    Chang, Chang

    2002-10-01

    The renaissance of Extreme Ultraviolet (EUV) and soft x-ray (SXR) optics in recent years is mainly driven by the desire of printing and observing ever smaller features, as in lithography and microscopy. This attribute is complemented by the unique opportunity for element specific identification presented by the large number of atomic resonances, essentially for all materials in this range of photon energies. Together, these have driven the need for new short-wavelength radiation sources (e.g. third generation synchrotron radiation facilities), and novel optical components, that in turn permit new research in areas that have not yet been fully explored. This dissertation is directed towards advancing this new field by contributing to the characterization of spatial coherence properties of undulator radiation and, for the first time, introducing Fourier optical elements to this short-wavelength spectral region. The first experiment in this dissertation uses the Thompson-Wolf two-pinhole method to characterize the spatial coherence properties of the undulator radiation at Beamline 12 of the Advanced Light Source. High spatial coherence EUV radiation is demonstrated with appropriate spatial filtering. The effects of small vertical source size and beamline apertures are observed. The difference in the measured horizontal and vertical coherence profile evokes further theoretical studies on coherence propagation of an EUV undulator beamline. A numerical simulation based on the Huygens-Fresnel principle is performed.

  11. Plasmonic lens for ultraviolet wavelength

    NASA Astrophysics Data System (ADS)

    Takeda, Minoru; Tanimoto, Takuya; Inoue, Tsutomu; Aizawa, Kento

    2016-09-01

    A plasmonic lens (PL) is one of the promising photonic devices utilizing the surface plasmon wave. In this study, we have newly developed a PL with a 3.5 µm diameter for a wavelength of 375 nm (ultraviolet region). It is composed of multiple circular slit apertures milled in aluminum (Al) thin film. We have simulated the electric field distribution of the PL, and confirmed that a tightly focused beam spot of subwavelength size in the far-field region was attained. We have also measured the focusing characteristics of the PL using a near-field scanning optical microscope (NSOM) and compared them with the calculated results.

  12. Far-field measurements of short-wavelength surface plasmons

    SciTech Connect

    Blau, Yochai; Gjonaj, Bergin; David, Asaf; Dolev, Shimon; Shterman, Doron; Bartal, Guy

    2015-03-23

    We present direct far-field measurements of short-wavelength surface plasmon polaritons (SPP) by conventional optics means. Plasmonic wavelength as short as 231 nm was observed for 532 nm illumination on a Ag−Si{sub 3}N{sub 4} platform, demonstrating the capability to characterize SPPs well below the optical diffraction limit. This is done by scaling a sub-wavelength interferometric pattern to a far-field resolvable periodicity. These subwavelength patterns are obtained by coupling light into counter-propagating SPP waves to create a standing-wave pattern of half the SPP wavelength periodicity. Such patterns are mapped by a scattering slit, tilted at an angle so as to increase the periodicity of the intensity pattern along it to more than the free-space wavelength, making it resolvable by diffraction limited optics. The simplicity of the method as well as its large dynamic range of measurable wavelengths make it an optimal technique to characterize the properties of plasmonic devices and high-index dielectric waveguides, to improve their design accuracy and enhance their functionality.

  13. Gaining Access.

    ERIC Educational Resources Information Center

    Kennedy, Mike

    2000-01-01

    Discusses issues schools and universities have encountered in complying with the Americans with Disabilities Act (ADA) and making their facilities more accessible to the disabled. The ADA's vagueness and the architect's need for understanding the regulations is highlighted. (GR)

  14. Equal Access.

    ERIC Educational Resources Information Center

    De Patta, Joe

    2003-01-01

    Presents an interview with Stephen McCarthy, co-partner and president of Equal Access ADA Consulting Architects of San Diego, California, about designing schools to naturally integrate compliance with the Americans with Disabilities Act (ADA). (EV)

  15. Capital access.

    PubMed

    Towne, Jennifer

    2004-06-01

    To maintain their viability, hospitals are being compelled to invest in big capital projects such as information technology and renovation and construction. This gatefold examines the trends in credit and capital, and how they affect hospitals' access to money.

  16. A new algorithm for optimizing the wavelength coverage for spectroscopic studies: Spectral Wavelength Optimization Code (SWOC)

    NASA Astrophysics Data System (ADS)

    Ruchti, G. R.; Feltzing, S.; Lind, K.; Caffau, E.; Korn, A. J.; Schnurr, O.; Hansen, C. J.; Koch, A.; Sbordone, L.; de Jong, R. S.

    2016-09-01

    The past decade and a half has seen the design and execution of several ground-based spectroscopic surveys, both Galactic and Extragalactic. Additionally, new surveys are being designed that extend the boundaries of current surveys. In this context, many important considerations must be done when designing a spectrograph for the future. Among these is the determination of the optimum wavelength coverage. In this work, we present a new code for determining the wavelength ranges that provide the optimal amount of information to achieve the required science goals for a given survey. In its first mode, it utilizes a user-defined list of spectral features to compute a figure-of-merit for different spectral configurations. The second mode utilizes a set of flux-calibrated spectra, determining the spectral regions that show the largest differences among the spectra. Our algorithm is easily adaptable for any set of science requirements and any spectrograph design. We apply the algorithm to several examples, including 4MOST, showing the method yields important design constraints to the wavelength regions.

  17. Multi-wavelength fluorescence tomography

    NASA Astrophysics Data System (ADS)

    Kwong, Tiffany C.; Lo, Pei-An; Cho, Jaedu; Nouizi, Farouk; Chiang, Huihua K.; Kim, Chang-Seok; Gulsen, Gultekin

    2016-03-01

    The strong scattering and absorption of light in biological tissue makes it challenging to model the propagation of light, especially in deep tissue. This is especially true in fluorescent tomography, which aims to recover the internal fluorescence source distribution from the measured light intensities on the surface of the tissue. The inherently ill-posed and underdetermined nature of the inverse problem along with strong tissue scattering makes Fluorescence Tomography (FT) extremely challenging. Previously, multispectral detection fluorescent tomography (FT) has been shown to improve the image quality of FT by incorporating the spectral filtering of biological tissue to provide depth information to overcome the inherent absorption and scattering limitations. We investigate whether multi-wavelength fluorescent tomography can be used to distinguish the signals from multiple fluorophores with overlapping fluorescence spectrums using a unique near-infrared (NIR) swept laser. In this work, a small feasibility study was performed to see whether multi-wavelength FT can be used to detect subtle shifts in the absorption spectrum due to differences in fluorophore microenvironment.

  18. Making Displaced Holograms At Two Wavelengths

    NASA Technical Reports Server (NTRS)

    Witherow, William K.; Ecker, Andreas

    1989-01-01

    Two-wavelength holographic system augmented with pair of prisms to introduce small separation between holograms formed simultaneously at two wavelengths on holographic plate. Principal use in study of flows. Gradients in index of refraction of fluid caused by variations in temperature, concentration, or both. Holography at one wavelength cannot be used to distinguish between two types of variations. Difference between spacings of fringes in photographs reconstructed from holograms taken simultaneously at two different wavelengths manipulated mathematically to determine type of variation.

  19. AJ/LPI at millimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Tiffany, G. B.; Bleck, D. T.; Boatman, R. K.

    The AJ/LPI advantages of millimeter wavelength communication at or near the 60-GHz oxygen line have been apparent to researchers for many years. Realizing the full extent of these advantages in a system appropriate for field operation requires more than simply designing a conventional communications link for operation at 60 GHz. Very low sidelobe, narrow beamwidth antennas of rugged construction and the use of frequency agility and spread spectrum modulation are also necessary. Construction of short range, clear weather tactical communication systems exploiting tropospheric oxygen absorption in the 50- to 70-GHz region appears feasible with current state-of-the-art solid-state components. The critical design parameters for achieving all weather jamming resistance and covertness are frequency selection, power management, waveform design, and antenna side- and back-lobe performance.

  20. Alerting effects of short-wavelength (blue) and long-wavelength (red) lights in the afternoon.

    PubMed

    Sahin, Levent; Figueiro, Mariana G

    2013-05-27

    Light has an acute effect on neuroendocrine responses, performance, and alertness. Most studies to date have linked the alerting effects of light to its ability to suppress melatonin, which is maximally sensitive to short-wavelength light. Recent studies, however, have shown alerting effects of white or narrowband short-wavelength lights during daytime, when melatonin levels are low. While the use of light at night to promote alertness is well understood, it is important to develop an understanding of how light impacts alertness during the daytime, especially during the post-lunch hours. The aim of the current study was to investigate how 48-minute exposures to short-wavelength (blue) light (40 lux, 18.9 microWatts/cm(2) λ(max) = 470 nanometers [nm]) or long-wavelength (red) light (40 lux, 18.9 microWatts/cm(2) λ(max) = 630 nm) close to the post-lunch dip hours affect electroencephalogram measures in participants with regular sleep schedules. Power in the alpha, alpha theta, and theta ranges was significantly lower (p<0.05) after participants were exposed to red light than after they remained in darkness. Exposure to blue light reduced alpha and alpha theta power compared to darkness, but these differences did not reach statistical significance (p>0.05). The present results extend those performed during the nighttime, and demonstrate that light can be used to increase alertness in the afternoon, close to the post-lunch dip hours. These results also suggest that acute melatonin suppression is not needed to elicit an alerting effect in humans. PMID:23535242

  1. Multiple Access Trade Study

    NASA Technical Reports Server (NTRS)

    Motamedi, Masoud

    1990-01-01

    The Personal Access Satellite System (PASS) strawman design uses a hybrid Time Division Multiple Access (TDMA)/Frequency Division Multiple Access (FDMA) implementation. TDMA is used for the forward direction (from Suppliers to Users), and FDMA for the return direction (from Users to Suppliers). An alternative architecture is proposed that will require minimal real time coordination and yet provide a fast access method by using random access Code Division Multiple Access (CDMA). The CDMA system issues are addressed such as connecting suppliers and users, both of whom may be located anywhere in the CONUS, when the user terminals are constrained in size and weight; and providing efficient traffic routing under highly variable traffic requirements. It is assumed that bandwidth efficiency is not of paramount importance. CDMA or Spread Spectrum Multiple Access (SSMA) communication is a method in which a group of carriers operate at the same nominal center frequency but are separable from each other by the low cross correlation of the spreading codes used. Interference and multipath rejection capability, ease of selective addressing and message screening, low density power spectra for signal hiding and security, and high resolution ranging are among the benefits of spread spectrum communications.

  2. Accessibility and assistive products

    PubMed Central

    Rodríguez-Porrero, Cristina

    2009-01-01

    Introduction Accessibility and assistive products and technologies are needed to ensure the rights of persons with disabilities and older persons. Many developments have been implemented in laws, standards, markets and from the consumers perspective, at international, European and national levels. The real issue is that not all the potential users benefit from the use of assistive products or accessible measures. Discussion Innovative methods are needed to allow all potential users to have real advantage of assistive technologies and accessible and design for all facilities. Best practices will be presented and existing gaps and recommendations will be discussed. Cost-benefits aspects will also be presented. Conclusion In order to get advantages from opportunities of globalization, hard work and responsibilities of all stakeholders are needed, so that assistive products and accessibility reach a whole range of situations and environments and contribute to ensure quality of life in a society for all.

  3. Extra- and intrathoracic access.

    PubMed

    Lazarides, Miltos K; Georgakarakos, Efstratios I; Schoretsanitis, Nikolaos

    2014-01-01

    The most complex patients requiring vascular access are those with bilateral central vein occlusions. Endovascular repair of the central lesions when feasible allow upper extremity use for access. When endovascular repair is not feasible, femoral vein transposition should be the next choice. When lower limb access sites have been exhausted or are contraindicated as in obese patients and in patients with peripheral arterial obstructive disease, a range of extrathoracic "exotic" extra-anatomic access procedures as the necklace cross-chest arteriovenous (AV) grafts, the ipsilateral axillo-axillary loops, the brachial-jugular AV grafts, the axillo-femoral AV grafts or even intra-thoracic ones as the right atrial AV bypasses represent the vascular surgeon's last resort. The selection among those extra-anatomical chest-wall procedures should be based upon each patient's anatomy or patient-specific factors. PMID:24817469

  4. Sub-microsecond wavelength stabilization of tunable lasers with the internal wavelength locker

    NASA Astrophysics Data System (ADS)

    Kimura, Ryoga; Tatsumoto, Yudai; Sakuma, Kazuki; Onji, Hirokazu; Shimokozono, Makoto; Ishii, Hiroyuki; Kato, Kazutoshi

    2016-08-01

    We proposed a method of accelerating the wavelength stabilization after wavelength switching of the tunable distributed amplification-distributed feedback (TDA-DFB) laser using the internal wavelength locker to reduce the size and the cost of the wavelength control system. The configuration of the wavelength stabilization system based on this locker was as follows. At the wavelength locker, the light intensity after an optical filter is detected as a current by the photodiodes (PDs). Then, for estimating the wavelength, the current is processed by the current/voltage-converting circuit (IVC), logarithm amplifier (Log Amp) and field programmable gate array (FPGA). Finally, the laser current is tuned to the desired wavelength with reference to the estimated wavelength. With this control system the wavelength is stabilized within 800 ns after wavelength switching, which is even faster than that with the conventional control system.

  5. Procedures for Wavelength Calibration and Spectral Response Correction of CCD Array Spectrometers

    PubMed Central

    Gaigalas, A. K.; Wang, Lili; He, Hua-Jun; DeRose, Paul

    2009-01-01

    This work describes a procedure for acquiring a spectrum of an analyte over an extended range of wavelengths and validating the wavelength and intensity assignments. To acquire a spectrum over an extended range of wavelengths with a spectrometer with a charge coupled device (CCD) array detector, it is necessary to acquire many partial spectra, each at a different angular position of the grating, and splice the partial spectra into a single extended spectrum. The splicing procedure exposes instrument dependent artifacts. It is demonstrated that by taking a spectrum of a reference irradiance source and making spectral correction, the artifacts exposed by the splicing are removed from the analyte spectrum. This is because the irradiance reference spectrum contains the same artifacts as the analyte spectrum. The artifacts exposed by the splicing depend on the wavelength of the splice; therefore it is important to measure the irradiance reference spectrum for the same range of wavelengths used to measure the spectrum of the analyte solution. In other words, there is no general spectral correction factor which is applicable to spectra taken for different range of wavelengths. The wavelength calibration is also carried out by splicing many partial spectra from a source like a krypton lamp. However the wavelength assignments are not sensitive to the splicing procedure and the same wavelength calibration can be used for spectra acquired over different extended wavelength ranges. The wavelength calibration checks the validity of the setting of the grating angular position, and the assignment of wavelengths to individual pixels on the CCD array detector. The procedure is illustrated by measuring the spectrum of an orange glass and the spectrum of a suspension of microalgae. PMID:27504223

  6. Laser Ranging Simulation Program

    NASA Technical Reports Server (NTRS)

    Piazolla, Sabino; Hemmati, Hamid; Tratt, David

    2003-01-01

    Laser Ranging Simulation Program (LRSP) is a computer program that predicts selected aspects of the performances of a laser altimeter or other laser ranging or remote-sensing systems and is especially applicable to a laser-based system used to map terrain from a distance of several kilometers. Designed to run in a more recent version (5 or higher) of the MATLAB programming language, LRSP exploits the numerical and graphical capabilities of MATLAB. LRSP generates a graphical user interface that includes a pop-up menu that prompts the user for the input of data that determine the performance of a laser ranging system. Examples of input data include duration and energy of the laser pulse, the laser wavelength, the width of the laser beam, and several parameters that characterize the transmitting and receiving optics, the receiving electronic circuitry, and the optical properties of the atmosphere and the terrain. When the input data have been entered, LRSP computes the signal-to-noise ratio as a function of range, signal and noise currents, and ranging and pointing errors.

  7. Measurements of Eavesdropping in a Wavelength/Time Optical CDMA (O-CDMA) System, with Data Confidentiality Implications

    SciTech Connect

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

    2005-07-29

    We report measurements on what an eavesdropper ''sees'' when tapping into a wavelength/time O-CDMA system in which 16 of 32 codes are ''lit''. Severe multi-access interference (MAI) provides some data confidentiality.

  8. Optical add/drop filter for wavelength division multiplexed systems

    DOEpatents

    Deri, Robert J.; Strand, Oliver T.; Garrett, Henry E.

    2002-01-01

    An optical add/drop filter for wavelength division multiplexed systems and construction methods are disclosed. The add/drop filter includes a first ferrule having a first pre-formed opening for receiving a first optical fiber; an interference filter oriented to pass a first set of wavelengths along the first optical fiber and reflect a second set of wavelengths; and, a second ferrule having a second pre-formed opening for receiving the second optical fiber, and the reflected second set of wavelengths. A method for constructing the optical add/drop filter consists of the steps of forming a first set of openings in a first ferrule; inserting a first set of optical fibers into the first set of openings; forming a first set of guide pin openings in the first ferrule; dividing the first ferrule into a first ferrule portion and a second ferrule portion; forming an interference filter on the first ferrule portion; inserting guide pins through the first set of guide pin openings in the first ferrule portion and second ferrule portion to passively align the first set of optical fibers; removing material such that light reflected from the interference filter from the first set of optical fibers is accessible; forming a second set of openings in a second ferrule; inserting a second set of optical fibers into the second set of openings; and positioning the second ferrule with respect to the first ferrule such that the second set of optical fibers receive the light reflected from the interference filter.

  9. Retinal spot size with wavelength

    NASA Astrophysics Data System (ADS)

    Rockwell, Benjamin A.; Hammer, Daniel X.; Kennedy, Paul K.; Amnotte, Rodney E.; Eilert, Brent; Druessel, Jeffrey J.; Payne, Dale J.; Phillips, Shana L.; Stolarski, David J.; Noojin, Gary D.; Thomas, Robert J.; Cain, Clarence P.

    1997-06-01

    We have made an indirect in-vivo determination of spot size focusing in the rhesus monkey model. Measurement of the laser induced breakdown threshold both in-vitro and in-vivo allow correlation and assignment of a spot size after focusing through the living eye. We discuss and analyze the results and show how trends in minimum visible lesion data should be assessed in light of chromatic aberration. National laser safety standards are based on minimal visual lesion (MVL) threshold studies in different animal models. The energy required for a retinal lesion depends upon may parameters including wavelength and retinal spot size. We attempt to explain trends in reported MVL threshold studies using a model of the eye which allows calculation of changes in retinal spot size due to chromatic aberration.

  10. Bolometric Arrays for Millimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Castillo, E.; Serrano, A.; Torres-Jácome, A.

    2009-11-01

    During last years, semiconductor bolometers using thin films have been developed at INAOE, specifically boron-doped hydrogenated amorphous silicon films. The characteristics shown by these devices made them attractive to be used in astronomical instrumentation, mainly in two-dimentional arrays. These detector arrays used at the Large Millimeter Telescope will make possible to obtain astronomical images in millimeter and sub-millimeter wavelengths. With this in mind, we are developing a method to produce, with enough reliability, bolometer arrays at INAOE. Until now, silicon nitride diaphragm arrays, useful as radiation absorbers, have succesfully been obtained. Sizes going from one to four millimeter by element in a consistent way; however we have not tested thermometers and metallic contact deposition yet. At the same time, we are working on two possible configurations for the readout electronics; one of them using commercial components while the other will be an integrated circuit specifically designed for this application. Both versions will work below 77K.

  11. Aluminum nitride nanophotonic circuits operating at ultraviolet wavelengths

    SciTech Connect

    Stegmaier, M.; Ebert, J.; Pernice, W. H. P.; Meckbach, J. M.; Ilin, K.; Siegel, M.

    2014-03-03

    Aluminum nitride (AlN) has recently emerged as a promising material for integrated photonics due to a large bandgap and attractive optical properties. Exploiting the wideband transparency, we demonstrate waveguiding in AlN-on-Insulator circuits from near-infrared to ultraviolet wavelengths using nanophotonic components with dimensions down to 40 nm. By measuring the propagation loss over a wide spectral range, we conclude that both scattering and absorption of AlN-intrinsic defects contribute to strong attenuation at short wavelengths, thus providing guidelines for future improvements in thin-film deposition and circuit fabrication.

  12. Three Dimensional Imaging with Multiple Wavelength Speckle Interferometry

    SciTech Connect

    Bernacki, Bruce E.; Cannon, Bret D.; Schiffern, John T.; Mendoza, Albert

    2014-05-28

    We present the design, modeling, construction, and results of a three-dimensional imager based upon multiple-wavelength speckle interferometry. A surface under test is illuminated with tunable laser light in a Michelson interferometer configuration while a speckled image is acquired at each laser frequency step. The resulting hypercube is Fourier transformed in the frequency dimension and the beat frequencies that result map the relative offsets of surface features. Synthetic wavelengths resulting from the laser tuning can probe features ranging from 18 microns to hundreds of millimeters. Three dimensional images will be presented along with modeling results.

  13. Collecting EUV mask images through focus by wavelength tuning

    SciTech Connect

    Goldberg, Kenneth A.; Mochi, Iacopo; Huh, Sungmin

    2009-02-23

    Using an extreme-ultraviolet (EUV) microscope to produce high-quality images of EUV reticles, we have developed a new wavelength tuning method to acquire through-focus data series with a higher level of stability and repeatability than was previously possible. We utilize the chromatic focal-length dependence of a diffractive Fresnel zoneplate objective lens, and while holding the mask sample mechanically still, we tune the wavelength through a narrow range, in small steps. In this paper, we demonstrate the method and discuss the relative advantages that this data collection technique affords.

  14. Optimal laser wavelength for photoacoustic imaging of breast microcalcifications

    NASA Astrophysics Data System (ADS)

    Kang, Jeeun; Kim, Eun-Kyung; Young Kwak, Jin; Yoo, Yangmo; Song, Tai-Kyong; Ho Chang, Jin

    2011-10-01

    This paper presents photoacoustic imaging (PAI) for real-time detection of micro-scale calcifications (e.g., <1 mm) in the breast, which are an indicator of the cancer occurrence. Optimal wavelength of incident laser for the microcalcification imaging was ascertained through ex vivo experiments with seven breast specimens of volunteers. In the ex vivo experiments, the maximum amplitude of photoacoustic signals from the microcalcifications occurred when the laser wavelength ranged from 690 to 700 nm. This result demonstrated that PAI can serve as a real-time imaging and guidance tool for diagnosis and biopsy of the breast microcalcifications.

  15. Femtosecond laser color marking stainless steel surface with different wavelengths

    NASA Astrophysics Data System (ADS)

    Li, Guoqiang; Li, Jiawen; Hu, Yanlei; Zhang, Chenchu; Li, Xiaohong; Chu, Jiaru; Huang, Wenhao

    2015-03-01

    The femtosecond laser color marking stainless steel surfaces with different incident wavelengths were investigated theoretically and experimentally. It indicates that the spectral regions of the colors firstly increase and then reduce with increasing spatial periods of the ripples induced by laser irradiation. Additionally, the colors are gradually changed from blue to red due to the elongation of the diffracted light wavelengths. As a result, the color effects are distinctly different. This study offers a new controllable parameter to produce diverse colors, which may find a wide range of applications in the laser color marking, art designing and so on.

  16. A New Wavelength Calibration Method for LAMOST Based on Piecewise Fitting

    NASA Astrophysics Data System (ADS)

    Ye, Gen-hong; Ye, Zhong-fu; Zhu, Jia

    2014-04-01

    The traditional methods of wavelength calibration for the LAM-OST (Large Area Multi-Object Fiber Spectroscopic Telescope) usually use a fifth-order polynomial to perform fitting and calibration in a broad wavelength range. Obviously, it is unable to reflect very well the local dispersion relations by using only one polynomial to fit the whole waveband. In order to reflect accurately the dispersion characteristics of local wavebands, a new wavelength calibration method based on piecewise fitting is proposed. In this method, the entire wavelength range is divided into several sub-bands according to certain principles, and a proper polynomial is used to perform fitting and calibration for each sub-band separately. Compared with the traditional methods of wave-length calibration, the experimental results show that this new method can get a more precise description of the dispersion characteristics of local wavebands. Therefore, the accuracy of wavelength calibration in the whole waveband will be further improved.

  17. Hemodialysis access - self care

    MedlinePlus

    Kidney failure - chronic-hemodialysis access; Renal failure - chronic-hemodialysis access; Chronic renal insufficiency - hemodialysis access; Chronic kidney failure - hemodialysis access; Chronic renal failure - hemodialysis access; dialysis - hemodialysis access

  18. Wavelength-multiplexing phase-sensitive surface plasmon imaging sensor.

    PubMed

    Shao, Yonghong; Li, Yan; Gu, Dayong; Zhang, Kai; Qu, Junle; He, Jianan; Li, Xuejin; Wu, Shu-Yuen; Ho, Ho-Pui; Somekh, Michael G; Niu, Hanben

    2013-05-01

    A wavelength-multiplexing phase-sensitive surface plasmon resonance (SPR) imaging sensor offering wide dynamic detection range and microarray capability is reported. Phase detection is accomplished by performing self-interference between the s- and p- polarizations within the signal beam. A liquid crystal tunable filter is used to sequentially select the SPR excitation wavelength from a white light source. This wavelength-multiplexing approach enables fast detection of the sensor's SPR phase response over a wide range of wavelengths, thereby covering literally any regions of interest within the SPR dip and thus maintaining the highest sensitivity point at all times. The phase-sensitive approach is particularly important for imaging SPR sensing applications because of its less stringent requirements for intensity signal-to-noise ratio, which also means the possibility of using uncooled modest resolution analog-to-digital conversion imaging devices. Experimental results demonstrate a resolution of 2.7×10(-7) RIU with a dynamic range of 0.0138 RIU. PMID:23632487

  19. The Effects of Space Weathering at UV Wavelengths: S-Class Asteroids

    NASA Technical Reports Server (NTRS)

    Hendrix, Amanda R.; Vilas, Faith

    2006-01-01

    We present evidence that space weathering manifests itself at near-UV wavelengths as a bluing of the spectrum, in contrast with the spectral reddening that has been seen at visible-near-IR wavelengths. Furthermore, the effects of space weathering at UV wavelengths tend to appear with less weathering than do the longer wavelength effects, suggesting that the UV wavelength range is a more sensitive indicator of weathering, and thus age. We report results from analysis of existing near-UV (approx.220-350 nm) measurements of S-type asteroids from the International Ultraviolet Explorer and the Hubble Space Telescope and comparisons with laboratory measurements of meteorites to support this hypothesis. Composite spectra of S asteroids are produced by combining UV spacecraft data with ground-based longer wavelength data. At visible-near-IR wavelengths, S-type asteroids are generally spectrally redder (and darker) than ordinary chondrite meteorites, whereas the opposite is generally true at near-UV wavelengths. Similarly, laboratory measurements of lunar samples show that lunar soils (presumably more weathered) are spectrally redder at longer wavelengths, and spectrally bluer at near-UV wavelengths, than less weathered crushed lunar rocks. The UV spectral bluing may be a result of the addition of nanophase iron to the regolith through the weathering process. The UV bluing is most prominent in the 300-400 nm range, where the strong UV absorption edge is degraded with weathering.

  20. Narrow-band radiation wavelength measurement by processing digital photographs in RAW format

    SciTech Connect

    Kraiskii, A V; Mironova, T V; Sultanov, T T

    2012-12-31

    The technique of measuring the mean wavelength of narrow-band radiation in the 455 - 625-nm range using the image of the emitting surface is presented. The data from the camera array unprocessed by the built-in processor (RAW format) are used. The method is applied for determining the parameters of response of holographic sensors. Depending on the wavelength and brightness of the image fragment, the mean square deviation of the wavelength amounts to 0.3 - 3 nm. (experimental techniques)

  1. Two-wavelength laser-diode heterodyne interferometry with one phasemeter

    NASA Astrophysics Data System (ADS)

    Onodera, Ribun; Ishii, Yukihiro

    1995-12-01

    A two-wavelength laser-diode interferometer that is based on heterodyne detection with one phasemeter has been constructed. Two laser diodes are frequency modulated by mutually inverted sawtooth currents on an unbalanced interferometer. One can measure the tested phase at a synthetic wavelength from the sum of the interference beat signals by synchronizing them with the modulation frequency. The experimental result presented shows a phase-measurement range with a 4.7- mu m synthetic wavelength.

  2. Space-charge impedance calculations in long-wavelength approximation

    NASA Astrophysics Data System (ADS)

    Kurennoy, Sergey S.

    1999-12-01

    Space-charge impedance calculations for smooth vacuum chambers with an arbitrary cross-section and perfectly conducting walls are considered in the long-wavelength approximation, when ωb/(βγc)≪1, where b is a typical transverse size. For the SNS beam energies βγ⩽1.8, and the wavelengths are long when λ≫b. Within the long-wavelength approximation, the fields can be found by solving a 2-D electrostatic problem. Two examples are presented: the space-charge impedance of screening wires (RF-cage) and of a ceramic chamber with inner metal stripes. In addition, we explore the transverse space-charge impedance of a circular pipe with account of betatron oscillations in a wide frequency range.

  3. Multi-wavelength holography with a single spatial light modulator for ultracold atom experiments.

    PubMed

    Bowman, David; Ireland, Philip; Bruce, Graham D; Cassettari, Donatella

    2015-04-01

    We demonstrate a method to independently and arbitrarily tailor the spatial profile of light of multiple wavelengths and we show possible applications to ultracold atoms experiments. A single spatial light modulator is programmed to create a pattern containing multiple spatially separated structures in the Fourier plane when illuminated with a single wavelength. When the modulator is illuminated with overlapped laser beams of different wavelengths, the position of the structures is wavelength-dependent. Hence, by designing their separations appropriately, a desired overlap of different structures at different wavelengths is obtained. We employ regional phase calculation algorithms and demonstrate several possible experimental scenarios by generating light patterns with 670 nm, 780 nm and 1064 nm laser light which are accurate to the level of a few percent. This technique is easily integrated into cold atom experiments, requiring little optical access.

  4. Intersubband transitions in nonpolar GaN/Al(Ga)N heterostructures in the short- and mid-wavelength infrared regions

    SciTech Connect

    Lim, C. B.; Beeler, M.; Ajay, A.; Lähnemann, J.; Bellet-Amalric, E.; Monroy, E.; Bougerol, C.

    2015-07-07

    This paper assesses nonpolar m- and a-plane GaN/Al(Ga)N multi-quantum-wells grown on bulk GaN for intersubband optoelectronics in the short- and mid-wavelength infrared ranges. The characterization results are compared to those for reference samples grown on the polar c-plane, and are verified by self-consistent Schrödinger-Poisson calculations. The best results in terms of mosaicity, surface roughness, photoluminescence linewidth and intensity, as well as intersubband absorption are obtained from m-plane structures, which display room-temperature intersubband absorption in the range from 1.5 to 2.9 μm. Based on these results, a series of m-plane GaN/AlGaN multi-quantum-wells were designed to determine the accessible spectral range in the mid-infrared. These samples exhibit tunable room-temperature intersubband absorption from 4.0 to 5.8 μm, the long-wavelength limit being set by the absorption associated with the second order of the Reststrahlen band in the GaN substrates.

  5. Easy Access

    ERIC Educational Resources Information Center

    Gettelman, Alan

    2009-01-01

    School and university restrooms, locker and shower rooms have specific ADA accessibility requirements that serve the needs of staff, students and campus visitors who are disabled as a result of injury, illness or age. Taking good care of them is good for the reputation of a sensitive community institution, and fosters positive public relations.…

  6. Access Denied

    ERIC Educational Resources Information Center

    Raths, David

    2012-01-01

    As faculty members add online and multimedia elements to their courses, colleges and universities across the country are realizing that there is a lot of work to be done to ensure that disabled students (and employees) have equal access to course material and university websites. Unfortunately, far too few schools consider the task a top priority.…

  7. Expanding Access

    ERIC Educational Resources Information Center

    Roach, Ronald

    2007-01-01

    There is no question that the United States lags behind most industrialized nations in consumer access to broadband Internet service. For many policy makers and activists, this shortfall marks the latest phase in the struggle to overcome the digital divide. To remedy this lack of broadband affordability and availability, one start-up firm--with…

  8. Wavelength measurement of tunable TEA CO2 laser

    NASA Astrophysics Data System (ADS)

    Qu, Yanchen; Ren, Deming; Hu, Xiaoyong; Liu, Fengmei; Zhang, Lili; Chen, Chunyu

    2005-01-01

    Due to their interesting physical and chemical parameters, tunable transversely excited atmospheric-pressure(TEA) CO2 lasers are widely utilized in scientific and industrial applications. The CO2 differential absorption lidar (DIAL) is an effective tool for remote measurement of pollutant gaseous concentration of the atmosphere over large areas. Many pollutant gases have strong absorption lines within the spectral range of CO2 laser wavelength tuning. In addition, the radiation of CO2 laser is well distributed in the atmosphere, coinciding with the "transparency window" of the atmosphere. Therefore the wavelength tunable TEA CO2 laser is an ideal optical source for DIAL. Most existing instruments for measuring the laser wavelength are only suitable for the measurement of continuous wave and stable frequency output. With the attempt of measuring the wavelength of pulsed TEA CO2 laser, an experimental setup is established which consists of two main portions, namely auto-scanning grating monochromator as the color dispersion system and Boxcar integrator. In the experiment of tuning TEA CO2 laser, the wavelength of CO2 laser is observed and measured by means of integrating method. The accuracy of measurement in the mid-infrared region attains 1nm.

  9. Aerosol-induced laser breakdown thresholds: wavelength dependence.

    PubMed

    Pinnick, R G; Chylek, P; Jarzembski, M; Creegan, E; Srivastava, V; Fernandez, G; Pendleton, J D; Biswas, A

    1988-03-01

    Aerosol-induced loser breakdown thresholds have been measured for liquid droplets at wavelengths lambda= 1.064, 0.532, 0.355, 0.266 microm using a Nd:YAG laser with 5-10-ns pulse duration. Breakdown thresholds are 2-3 orders of magnitude below those for clean air and range from 4 x 10(7) to 3 x 10(9) W cm(-2) for nominal 50-microm diam droplets, depending on laser wavelength and droplet composition. Thresholds decrease with decreasing wavelength; they also decrease for droplets having a higher real refractive index. For water droplets the breakdown threshold intensity varies approximately as lambda(0.5). The wavelength dependence of breakdown thresholds can be qualitatively explained by considering (1) the effect of enhancement of internal fields and energy density within and near droplets and (2) the increasing importance of multiphoton absorption processes at shorter wavelengths. Laser transmission losses through the breakdown plasma and observations of the suppression of stimulated Raman scattering by the addition of small quantitites of absorbing material to water and carbon tetrachloride droplets are also reported.

  10. Terahertz ambipolar dual-wavelength quantum cascade laser.

    PubMed

    Lever, L; Hinchcliffe, N M; Khanna, S P; Dean, P; Ikonic, Z; Evans, C A; Davies, A G; Harrison, P; Linfield, E H; Kelsall, R W

    2009-10-26

    Terahertz frequency quantum cascade lasers (THz QCLs) are compact solid-state sources of terahertz radiation that were first demonstrated in 2002. They have a broad range of potential applications ranging from gas sensing and non-destructive testing, through to security and medical imaging, with many polycrystalline compounds having distinct fingerprint spectra in the terahertz frequency range. In this article, we demonstrate an electrically-switchable dual-wavelength THz QCL which will enable spectroscopic information to be obtained within a THz QCL-based imaging system. The device uses the same active region for both emission wavelengths: in forward bias, the laser emits at 2.3 THz; in reverse bias, it emits at 4 THz. The corresponding threshold current densities are 490 A/cm(2) and 330 A/cm(2), respectively, with maximum operating temperatures of 98K and 120 K.

  11. Laser System for Precise, Unambiguous Range Measurements

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, Oliver

    2005-01-01

    The Modulation Sideband Technology for Absolute Range (MSTAR) architecture is the basis of design of a proposed laser-based heterodyne interferometer that could measure a range (distance) as great as 100 km with a precision and resolution of the order of 1 nm. Simple optical interferometers can measure changes in range with nanometer resolution, but cannot measure range itself because interference is subject to the well-known integer-multiple-of-2 -radians phase ambiguity, which amounts to a range ambiguity of the order of 1 m at typical laser wavelengths. Existing rangefinders have a resolution of the order of 10 m and are therefore unable to resolve the ambiguity. The proposed MSTAR architecture bridges the gap, enabling nanometer resolution with an ambiguity range that can be extended to arbitrarily large distances. The MSTAR architecture combines the principle of the heterodyne interferometer with the principle of extending the ambiguity range of an interferometer by using light of two wavelengths. The use of two wavelengths for this purpose is well established in optical metrology, radar, and sonar. However, unlike in traditional two-color laser interferometry, light of two wavelengths would not be generated by two lasers. Instead, multiple wavelengths would be generated as sidebands of phase modulation of the light from a single frequency- stabilized laser. The phase modulation would be effected by applying sinusoidal signals of suitable frequencies (typically tens of gigahertz) to high-speed electro-optical phase modulators. Intensity modulation can also be used

  12. Simultaneous Temperature and Strain Sensing for Cryogenic Applications Using Dual-Wavelength Fiber Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Wu, Meng-Chou; Prosser, William H.

    2003-01-01

    A new technique has been developed for sensing both temperature and strain simultaneously by using dual-wavelength fiber-optic Bragg gratings. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. This enables the simultaneous measurement of temperature and strain. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. The effectiveness and sensitivities of these measurements in different temperature ranges are also discussed.

  13. Accessibility in E-Assessment

    ERIC Educational Resources Information Center

    Ball, Simon

    2009-01-01

    E-assessment offers many opportunities to broaden the range of tools at the assessor's disposal and thereby improve the overall accessibility of the assessment experience. In 2006, TechDis commissioned a report, produced by Edexcel, on the state of guidance on accessibility at the various stages of the assessment process--question design,…

  14. How long wavelengths can one extract from silica-core fibers?

    PubMed Central

    Lægsgaard, Jesper; Tu, Haohua

    2014-01-01

    The generation of wavelengths above 3 μm by nonlinear processes in short silica photonic crystal fibers is investigated numerically. It was found that wavelengths in the 3–3.5 μm range may be generated quite efficiently in centimeter-long fiber pieces when pumping with femtosecond pulses in the 1.55–2 μm range. Wavelengths in the range of 3.5–4 μm can in principle be generated, but these require shorter fiber lengths for efficient extraction. The results indicate that useful 3 μm sources may be fabricated with existing silica-based fiber technology. PMID:24177134

  15. Laser wavelength meter: analysis of measurement uncertainties

    NASA Astrophysics Data System (ADS)

    Skrzeczanowski, Wojciech; Zyczkowski, Marek; Dlugaszek, Andrzej

    1999-08-01

    Principle of operation of laser radiation wavelength meter based on Fabry-Perot interferometer and linear CCD camera is presented in the paper. A dependence, on the base of which laser wavelength can be calculated, is found and a way of defining of all component uncertainties of a measurement is shown. An analysis of an influence and examples of definition of uncertainties of a measurement for four wavelength meter structural sets of different objective focal lengths are presented.

  16. Wavelength-doubling optical parametric oscillator

    DOEpatents

    Armstrong, Darrell J.; Smith, Arlee V.

    2007-07-24

    A wavelength-doubling optical parametric oscillator (OPO) comprising a type II nonlinear optical medium for generating a pair of degenerate waves at twice a pump wavelength and a plurality of mirrors for rotating the polarization of one wave by 90 degrees to produce a wavelength-doubled beam with an increased output energy by coupling both of the degenerate waves out of the OPO cavity through the same output coupler following polarization rotation of one of the degenerate waves.

  17. Optimizing constant wavelength neutron powder diffractometers

    NASA Astrophysics Data System (ADS)

    Cussen, Leo D.

    2016-06-01

    This article describes an analytic method to optimize constant wavelength neutron powder diffractometers. It recasts the accepted mathematical description of resolution and intensity in terms of new variables and includes terms for vertical divergence, wavelength and some sample scattering effects. An undetermined multiplier method is applied to the revised equations to minimize the RMS value of resolution width at constant intensity and fixed wavelength. A new understanding of primary spectrometer transmission (presented elsewhere) can then be applied to choose beam elements to deliver an optimum instrument. Numerical methods can then be applied to choose the best wavelength.

  18. Long-wavelength shift and enhanced room temperature photoluminescence efficiency in GaAsSb/InGaAs/GaAs-based heterostructures emitting in the spectral range of 1.0–1.2 μm due to increased charge carrier's localization

    SciTech Connect

    Kryzhkov, D. I. Yablonsky, A. N.; Morozov, S. V.; Aleshkin, V. Ya.; Krasilnik, Z. F.; Zvonkov, B. N.; Vikhrova, O. V.

    2014-11-28

    In this work, a study of the photoluminescence (PL) temperature dependence in quantum well GaAs/GaAsSb and double quantum well InGaAs/GaAsSb/GaAs heterostructures grown by metalorganic chemical vapor deposition with different parameters of GaAsSb and InGaAs layers has been performed. It has been demonstrated that in double quantum well InGaAs/GaAsSb/GaAs heterostructures, a significant shift of the PL peak to a longer-wavelength region (up to 1.2 μm) and a considerable reduction in the PL thermal quenching in comparison with GaAs/GaAsSb structures can be obtained due to better localization of charge carriers in the double quantum well. For InGaAs/GaAsSb/GaAs heterostructures, an additional channel of radiative recombination with participation of the excited energy states in the quantum well, competing with the main ground-state radiative transition, has been revealed.

  19. High power pumped mid-IR wavelength systems using nonlinear frequency mixing (NFM) devices

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    1999-01-01

    Laser diode pumped mid-IR wavelength systems include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  20. High power pumped MID-IR wavelength devices using nonlinear frequency mixing (NFM)

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  1. Hemodialysis access procedures

    MedlinePlus

    Kidney failure - chronic-dialysis access; Renal failure - chronic-dialysis access; Chronic renal insufficiency-dialysis access; Chronic kidney failure-dialysis access; Chronic renal failure-dialysis access

  2. Touch the Invisible Sky: A Multi-Wavelength Braille Book Featuring Tactile NASA Images

    NASA Astrophysics Data System (ADS)

    Grice, N.; Steel, S.; Daou, D.

    2008-06-01

    According to the American Foundation for the Blind and the National Federation of the Blind, there are approximately 10 million blind and visually impaired people in the United States. Because astronomy is often visually based, many people assume that it cannot be made accessible. A new astronomy book, Touch the Invisible Sky, makes wavelengths not visible to human eyes, accessible to all audiences through text in print and Braille and with pictures that are touchable and in color.

  3. An improved light source for laser ranging

    NASA Technical Reports Server (NTRS)

    Hamal, Karel; Richardson, Martin

    1993-01-01

    The development of a new laser material, Cr-doped LiSAF, makes possible the development of a laser source for satellite ranging systems that is more superior in performance capabilities than current Nd:YAG-based laser sources. This new material offers the potential of shorter pulses and more preferable wavelengths (850 and 425 nm) than multiwavelength Nd:YAG systems, leading to superior ranging resolution and greater detection sensitivity. We are embarking on a feasibility study of a two-wavelength, mode-locked laser system based on Cr:LiSAF, providing shorter pulses for improved ranging resolution.

  4. Widening Access to Higher Education: An Evaluative Case Study of a Foundation Year Alternative to Access

    ERIC Educational Resources Information Center

    Reddy, Peter A.; Moores, Elisabeth

    2008-01-01

    Universities are encouraged to widen access to a broad range of applicants, including mature students taking Access qualifications. Admissions tutors can find it difficult to compare and choose between Access and A-level applications, and Access applicants for popular courses may be disadvantaged relative to students with good A-levels. In this…

  5. Semiconductor laser with multiple lasing wavelengths

    DOEpatents

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-07-29

    A new class of multi-terminal vertical-cavity semiconductor laser components has been developed. These multi-terminal laser components can be switched, either electrically or optically, between distinct lasing wavelengths, or can be made to lase simultaneously at multiple wavelengths.

  6. Optical wavelength modulation in free electron lasers

    SciTech Connect

    Mabe, R.M.; Wong, R.K.; Colson, W.B.

    1995-12-31

    An attribute of the free electron laser (FEL) is the continuous tunability of the optical wavelength by modulation of the electron beam energy. The variation of the wavelength and power of the optical beam is studied as a function of FEL operating parameters. These results will be applied to the Stanford SCA FEL and Boeing FEL.

  7. B12-Mediated, Long Wavelength Photopolymerization of Hydrogels

    PubMed Central

    Rodgers, Zachary L.; Hughes, Robert M.; Doherty, Laura M.; Shell, Jennifer R.; Molesky, Brian P.; Brugh, Alexander M.; Forbes, Malcolm D. E.; Moran, Andrew M.; Lawrence, David S.

    2015-01-01

    Medical hydrogel applications have expanded rapidly over the past decade. Implantation in patients by noninvasive injection is preferred, but this requires hydrogel solidification from a low viscosity solution to occur in vivo via an applied stimuli. Transdermal photo-cross-linking of acrylated biopolymers with photoinitiators and lights offers a mild, spatiotemporally controlled solidification trigger. However, the current short wavelength initiators limit curing depth and efficacy because they do not absorb within the optical window of tissue (600–900 nm). As a solution to the current wavelength limitations, we report the development of a red light responsive initiator capable of polymerizing a range of acrylated monomers. Photoactivation occurs within a range of skin type models containing high biochromophore concentrations. PMID:25697508

  8. B(12)-mediated, long wavelength photopolymerization of hydrogels.

    PubMed

    Rodgers, Zachary L; Hughes, Robert M; Doherty, Laura M; Shell, Jennifer R; Molesky, Brian P; Brugh, Alexander M; Forbes, Malcolm D E; Moran, Andrew M; Lawrence, David S

    2015-03-11

    Medical hydrogel applications have expanded rapidly over the past decade. Implantation in patients by noninvasive injection is preferred, but this requires hydrogel solidification from a low viscosity solution to occur in vivo via an applied stimuli. Transdermal photo-cross-linking of acrylated biopolymers with photoinitiators and lights offers a mild, spatiotemporally controlled solidification trigger. However, the current short wavelength initiators limit curing depth and efficacy because they do not absorb within the optical window of tissue (600-900 nm). As a solution to the current wavelength limitations, we report the development of a red light responsive initiator capable of polymerizing a range of acrylated monomers. Photoactivation occurs within a range of skin type models containing high biochromophore concentrations.

  9. Early Results from the Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Taylor, Gregory B.; LWA Collaboration

    2012-01-01

    The Long Wavelength Array (LWA) will be a new multi-purpose radio telescope operating in the frequency range 10-88 MHz. Scientific programs include pulsars, supernova remnants, general transient searches, radio recombination lines, solar and Jupiter bursts, investigations into the "dark ages" using redshifted hydrogen, and ionospheric phenomena. Upon completion, LWA will consist of 53 phased array "stations” distributed accross a region over 400 km in diameter. Each station consists of 256 pairs of dipole-type antennas whose signals are formed into beams, with outputs transported to a central location for high-resolution aperture synthesis imaging. The resulting image sensitivity is estimated to be a few mJy (5sigma, 8 MHz, 2 polarizations, 1 h, zenith) from 20-80 MHz; with angular resolution of a few arcseconds. Additional information is online at http://lwa.unm.edu. Partners in the LWA project include LANL, JPL, NRAO, NRL, UNM, NMT, and Virginia Tech. The first station of the LWA, called "LWA1", is located near the center of the EVLA and has recently begun scientific operations. The LWA1 images the sky in realtime using the "transient buffer - narrowband” (TBN) system which is operational with 257 dipoles, and a bandwidth of 70 kHz. The LWA1 can also form up to 4 beams on the sky simultaneously with 16 MHz bandwidth in each of two tuning and full polarization. Early results include observations of pulsars, the Sun, and Jupiter.

  10. Radar scattering laws and wavelength dependence of the lunar surface

    NASA Technical Reports Server (NTRS)

    Simpson, R. A.

    1978-01-01

    Data from Apollo lunar bistatic radar experiments have been processed to give probability density functions for surface slopes. These show best agreement with a Hagfors scattering law, though data having both gaussian and exponential characteristics also exist. Surface roughness estimates range from 4 deg in maria to at least 8 deg in highlands, values which are appropriate to 25 m horizontal scales and which are areal averages over tens of square kilometers. Roughness varies with wavelength, most strongly in maria.

  11. Optical properties of silicon germanium waveguides at telecommunication wavelengths.

    PubMed

    Hammani, Kamal; Ettabib, Mohamed A; Bogris, Adonis; Kapsalis, Alexandros; Syvridis, Dimitris; Brun, Mickael; Labeye, Pierre; Nicoletti, Sergio; Richardson, David J; Petropoulos, Periklis

    2013-07-15

    We present a systematic experimental study of the linear and nonlinear optical properties of silicon-germanium (SiGe) waveguides, conducted on samples of varying cross-sectional dimensions and Ge concentrations. The evolution of the various optical properties for waveguide widths in the range 0.3 to 2 µm and Ge concentrations varying between 10 and 30% is considered. Finally, we comment on the comparative performance of the waveguides, when they are considered for nonlinear applications at telecommunications wavelengths.

  12. Quantitative comparison of wavelength dependence on penetration depth and imaging contrast for ultrahigh-resolution optical coherence tomography using supercontinuum sources at five wavelength regions

    NASA Astrophysics Data System (ADS)

    Ishida, S.; Nishizawa, N.

    2012-01-01

    Optical coherence tomography (OCT) is a non invasive optical imaging technology for micron-scale cross-sectional imaging of biological tissue and materials. We have been investigating ultrahigh resolution optical coherence tomography (UHR-OCT) using fiber based supercontinuum sources. Although ultrahigh longitudinal resolution was achieved in several center wavelength regions, its low penetration depth is a serious limitation for other applications. To realize ultrahigh resolution and deep penetration depth simultaneously, it is necessary to choose the proper wavelength to maximize the light penetration and enhance the image contrast at deeper depths. Recently, we have demonstrated the wavelength dependence of penetration depth and imaging contrast for ultrahigh resolution OCT at 0.8 μm, 1.3 μm, and 1.7 μm wavelength ranges. In this paper, additionally we used SC sources at 1.06 μm and 1.55 μm, and we have investigated the wavelength dependence of UHR-OCT at five wavelength regions. The image contrast and penetration depth have been discussed in terms of the scattering coefficient and water absorption of samples. Almost the same optical characteristics in longitudinal and lateral resolution, sensitivity, and incident optical power at all wavelength regions were demonstrated. We confirmed the enhancement of image contrast and decreased ambiguity of deeper epithelioid structure at longer wavelength region.

  13. An Update on the Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Taylor, Gregory B.; Tremblay, S. E.; Pihlstrom, Y.; Craig, J.; Rickard, L.; Dowell, J.; Kassim, N.; Clarke, T.; Hicks, B.; Polisensky, E.; Ray, P.; Schmitt, H.; Woods, D.; Hartman, J.; Ellingson, S.; Wolfe, C.; Navarro, R.; Sigman, E.; Soriano, M.; Owen, F.

    2011-01-01

    The Long Wavelength Array (LWA), a SKA Pathfinder, will be a new multi-purpose radio telescope operating in the frequency range 10-88 MHz. Scientific programs include pulsars, supernova remnants, general transient searches, radio recombination lines, solar and Jupiter bursts, investigations into the "dark ages" using redshifted hydrogen, and ionospheric phenomena. Upon completion, LWA will consist of 53 phased array "stations” distributed across a region over 400 km in diameter. Each station consists of 256 pairs of dipole-type antennas whose signals are formed into beams, with outputs transported to a central location for high-resolution aperture synthesis imaging. The resulting image sensitivity is estimated to be a few mJy (5sigma, 8 MHz, 2 polarizations, 1 h, zenith) from 20-80 MHz; with angular resolution of a few arcseconds. A technical overview of the LWA project is available (Ellingson etal. 2009, Proc. IEEE, 97, 1421), and additional information is online at http://lwa.unm.edu. Partners in the LWA project include LANL, JPL, NRAO, NRL, UNM, NMT, and Virginia Tech. The first station of the LWA, called "LWA-1", is located near the center of the EVLA and is expected to achieve initial operational capability in early 2011. As of September 2010, all antennas have been installed as well as a subset of the "production” versions of receivers, digital electronics, data recorders, and monitoring and control system. The "transient buffer - wideband” (TBW) capability is operational with 20 dipoles, and provides the ability to capture simultaneous raw 196 MSPS A/D output over the entire 10-88 MHz tuning range in 61 ms bursts. Other operating modes are in the final stages of implementation. Some early results obtained with LWA-1 will be presented. Funding for the LWA has been provided by the Office of Naval Research.

  14. Design of a wavelength frame multiplication system using acceptance diagrams

    NASA Astrophysics Data System (ADS)

    Nekrassov, D.; Zendler, C.; Lieutenant, K.

    2013-07-01

    The concept of Wavelength Frame Multiplication (WFM) was developed to extend the usable wavelength range on long pulse neutron sources for instruments using pulse shaping choppers. For some instruments, it is combined with a pulse shaping double chopper, which defines a constant wavelength resolution, and a set of frame overlap choppers that prevent spurious neutrons from reaching the detector thus avoiding systematic errors in the calculation of wavelength from time of flight. Due to its complexity, the design of such a system is challenging and there are several criteria that need to be accounted for. In this work, the design of the WFM chopper system for a potential future liquids reflectometer at the European Spallation Source (ESS) is presented, which makes use of acceptance diagrams. They prove to be a powerful tool for understanding the work principle of the system and recognizing potential problems. The authors assume that the presented study can be useful for design or upgrade of further instruments, in particular the ones planned for the ESS.

  15. 40nm tunable multi-wavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Jia, Qingsong; Wang, Tianshu; Zhang, Peng; Dong, Keyan; Jiang, Huilin

    2014-12-01

    A Brillouin-Erbium multi-wavelength tunable fiber laser at C-band is demostrated. A 10 km long singlemode fiber(SMF), a 6 m long Erbium-doped fiber, two couplers, a wavelength division multiplexer, a isolator, an optical circulator, a 980nm pump laser and a narrow linewidth tunable laser are included in the structure. A segment of 10 km-long single-mode fiber (SMF) between the two ports of a 1×2 coupler is used as Brillouin gain. Ebiumdoped fiber amplifier (EDFA) consists of a segment of 6m er-doped fiber pumped by 980nm laser dioder . A narrow linewidth tunable laser from 1527 to 1607 nm as Brillouin bump, At the Brillouin pump power of 8mW and the 980 nm pump power of 400 mw, 16 output channels with 0.08 nm spacing and tuning range of 40 nm from 1527 nm to 1567 nm are achieved. We realize the tunable output of wavelength by adjusting the 980 nm pump power and the Brillouin pump wavelength. Stability of the multiwavelength fiber laser is also observed.

  16. CO Ice Photodesorption: A Wavelength-dependent Study

    NASA Astrophysics Data System (ADS)

    Fayolle, Edith C.; Bertin, Mathieu; Romanzin, Claire; Michaut, Xavier; Öberg, Karin I.; Linnartz, Harold; Fillion, Jean-Hugues

    2011-10-01

    UV-induced photodesorption of ice is a non-thermal evaporation process that can explain the presence of cold molecular gas in a range of interstellar regions. Information on the average UV photodesorption yield of astrophysically important ices exists for broadband UV lamp experiments. UV fields around low-mass pre-main-sequence stars, around shocks and in many other astrophysical environments are however often dominated by discrete atomic and molecular emission lines. It is therefore crucial to consider the wavelength dependence of photodesorption yields and mechanisms. In this work, for the first time, the wavelength-dependent photodesorption of pure CO ice is explored between 90 and 170 nm. The experiments are performed under ultra high vacuum conditions using tunable synchrotron radiation. Ice photodesorption is simultaneously probed by infrared absorption spectroscopy in reflection mode of the ice and by quadrupole mass spectrometry of the gas phase. The experimental results for CO reveal a strong wavelength dependence directly linked to the vibronic transition strengths of CO ice, implying that photodesorption is induced by electronic transition (DIET). The observed dependence on the ice absorption spectra implies relatively low photodesorption yields at 121.6 nm (Lyα), where CO barely absorbs, compared to the high yields found at wavelengths coinciding with transitions into the first electronic state of CO (A1Π at 150 nm); the CO photodesorption rates depend strongly on the UV profiles encountered in different star formation environments.

  17. In-service communication channel sensing based on reflectometry for dynamic wavelength assigned wavelength- and time-division multiplexed passive optical network systems

    NASA Astrophysics Data System (ADS)

    Iida, Daisuke; Kuwano, Shigeru; Terada, Jun

    2015-04-01

    In future radio access systems, base stations will be mainly accommodated in wavelength- and time-division multiplexing passive optical network (PON) based mobile backhaul and fronthaul networks, and in such networks, failed connections in an optical network unit (ONU) wavelength channel will severely degrade mobile system performance. A cost-effective in-service ONU wavelength channel monitor is essential to ensure proper system operation without failed connections. To address this issue, we propose a reflectometry-based remote sensing method that provides ONU wavelength channel information with the optical line terminal-ONU distance. The proposed method enables real-time monitoring of ONU wavelength channels without data signal quality degradation and is also able to determine if the ONUs are connected to the PON. Experimental results show that it achieves wavelength channel distinction with a high distance resolution (˜10 m). Additionally, with the method, the distance resolution for distinguishing the ONUs after the PON splitter is determined by the received signal bandwidth or the test light modulation speed rather than by the pulse width as in conventional optical time-domain reflectometry.

  18. Wavelengths effective in induction of malignant melanoma

    SciTech Connect

    Setlow, R.B.; Grist, E.; Thompson, K.; Woodhead, A.D. )

    1993-07-15

    It is generally agreed that sunlight exposure is one of the etiologic agents in malignant melanoma of fair-skinned individuals. However, the wavelengths responsible for tumorigenesis are not known, although DNA is assumed to be the target because individuals defective in the repair of UV damage to DNA are several thousandfold more prone to the disease than the average population. Heavily pigmented back-cross hybrids of the genus Xiphophorus (platyfish and swordtails) are very sensitive to melanoma induction by single exposures to UV. The authors irradiated groups of five 6-day-old fish with narrow wavelength bands at 302, 313, 365, 405, and 436 nm and score the irradiated animals for melanomas 4 months later. They used several exposures at each wavelength to obtain estimates of the sensitivity for melanoma induction as a function of exposure and wavelength. The action spectrum (sensitivity per incident photon as a function of wavelength) for melanoma induction shows appreciable sensitivity at 365, 405, and probably 436 nm, suggesting that wavelengths not absorbed directly in DNA are effective in induction. They interpret the results as indicating that light energy absorbed in melanin is effective in inducing melanomas in this animal model and that, in natural sunlight, 90-95% of melanoma induction may be attributed to wavelengths >320 nm-the UV-A and visible spectral regions. 25 refs., 4 figs., 1 tab.

  19. Experimental verification of acoustic trace wavelength enhancement.

    PubMed

    Cray, Benjamin A

    2015-12-01

    Directivity is essentially a measure of a sonar array's beamwidth that can be obtained in a spherically isotropic ambient noise field; narrow array mainbeam widths are more directive than broader mainbeam widths. For common sonar systems, the directivity factor (or directivity index) is directly proportional to the ratio of an incident acoustic trace wavelength to the sonar array's physical length (which is always constrained). Increasing this ratio, by creating additional trace wavelengths for a fixed array length, will increase array directivity. Embedding periodic structures within an array generates Bragg scattering of the incident acoustic plane wave along the array's surface. The Bragg scattered propagating waves are shifted in a precise manner and create shorter wavelength replicas of the original acoustic trace wavelength. These replicated trace wavelengths (which contain identical signal arrival information) increase an array's wavelength to length ratio and thus directivity. Therefore, a smaller array, in theory, can have the equivalent directivity of a much larger array. Measurements completed in January 2015 at the Naval Undersea Warfare Center's Acoustic Test Facility, in Newport, RI, verified, near perfectly, these replicated, shorter, trace wavelengths. PMID:26723331

  20. Wavelengths Effective in Induction of Malignant Melanoma

    NASA Astrophysics Data System (ADS)

    Setlow, Richard B.; Grist, Eleanor; Thompson, Keith; Woodhead, Avril D.

    1993-07-01

    It is generally agreed that sunlight exposure is one of the etiologic agents in malignant melanoma of fair-skinned individuals. However, the wavelengths responsible for tumorigenesis are not known, although DNA is assumed to be the target because individuals defective in the repair of UV damage to DNA are several thousandfold more prone to the disease than the average population. Heavily pigmented backcross hybrids of the genus Xiphophorus (platyfish and swordtails) are very sensitive to melanoma induction by single exposures to UV. We irradiated groups of five 6-day-old fish with narrow wavelength bands at 302, 313, 365, 405, and 436 nm and scored the irradiated animals for melanomas 4 months later. We used several exposures at each wavelength to obtain estimates of the sensitivity for melanoma induction as a function of exposure and wavelength. The action spectrum (sensitivity per incident photon as a function of wavelength) for melanoma induction shows appreciable sensitivity at 365, 405, and probably 436 nm, suggesting that wavelengths not absorbed directly in DNA are effective in induction. We interpret the results as indicating that light energy absorbed in melanin is effective in inducing melanomas in this animal model and that, in natural sunlight, 90-95% of melanoma induction may be attributed to wavelengths > 320 nm-the UV-A and visible spectral regions.

  1. Multiple Wavelength Observations of Flaring Active Regions

    NASA Astrophysics Data System (ADS)

    Lang, Kenneth R.

    The radio emission of quiescent active regions at 6 cm wavelength marks the legs of magnetic dipoles, and the emission at 20 cm wavelength delineates the radio wavelength counterpart of the coronal loops previously detected at X-ray wavelengths. At both wavelengths the temperatures have coronal values of a few million degrees. The polarization of the radio emission specifies the structure and strength of the coronal magnetic field (H ≈ 600 Gauss at heights h ≈ 4 x 109 cm above sunspot umbrae). At 6 cm and 20 cm wavelength the solar bursts have angular sizes between 5" and 30", brightness temperatures between 2 x 107 K and 2 x 108 K, and degrees of circular polarization between 10% and 90%. The location of the burst energy release is specified with second-of-arc accuracy. At radio wavelengths the bursts occur within the central regions of magnetic loops, while the flaring Ha kernels are located at the loop footpoints. Coronal loops exhibit enhanced radio emission (preburst heating) a few minutes before the release of burst energy. The radio polarization data indicate magnetic changes before and during solar bursts.

  2. Experimental verification of acoustic trace wavelength enhancement.

    PubMed

    Cray, Benjamin A

    2015-12-01

    Directivity is essentially a measure of a sonar array's beamwidth that can be obtained in a spherically isotropic ambient noise field; narrow array mainbeam widths are more directive than broader mainbeam widths. For common sonar systems, the directivity factor (or directivity index) is directly proportional to the ratio of an incident acoustic trace wavelength to the sonar array's physical length (which is always constrained). Increasing this ratio, by creating additional trace wavelengths for a fixed array length, will increase array directivity. Embedding periodic structures within an array generates Bragg scattering of the incident acoustic plane wave along the array's surface. The Bragg scattered propagating waves are shifted in a precise manner and create shorter wavelength replicas of the original acoustic trace wavelength. These replicated trace wavelengths (which contain identical signal arrival information) increase an array's wavelength to length ratio and thus directivity. Therefore, a smaller array, in theory, can have the equivalent directivity of a much larger array. Measurements completed in January 2015 at the Naval Undersea Warfare Center's Acoustic Test Facility, in Newport, RI, verified, near perfectly, these replicated, shorter, trace wavelengths.

  3. Wavelength initialization employing wavelength recognition scheme in WDM-PON based on tunable lasers

    NASA Astrophysics Data System (ADS)

    Mun, Sil-Gu; Lee, Eun-Gu; Lee, Jong Hyun; Lee, Sang Soo; Lee, Jyung Chan

    2015-01-01

    We proposed a simple method to initialize the wavelength of tunable lasers in WDM-PON employing wavelength recognition scheme with an optical filter as a function of wavelength and accomplished plug and play operation. We also implemented a transceiver based on our proposed wavelength initialization scheme and then experimentally demonstrated the feasibility in WDM-PON configuration guaranteeing 16 channels with 100 GHz channel spacing. Our proposal is a cost-effective and easy-to-install method to realize the wavelength initialization of ONU. In addition, this method will support compatibility with all kind of tunable laser regardless of their structures and operating principles.

  4. Multi-wavelength transmission spectroscopy revisited for micron and submicron particle characterization.

    PubMed

    Smith, Jennifer M; Roth, Alison; Huffman, Debra E; Serebrennikova, Yulia M; Lindon, Jack; García-Rubio, Luis H

    2012-10-01

    Multi-wavelength transmission (MWT) ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy, a technique underappreciated for particle characterization, is systematically explored using a set of NIST traceable standards over the nominal size range of 20 to 20,000 nm. Experimental results demonstrate that the particle size distributions obtained from MWT spectral data are in excellent agreement with the values reported by the manufacturer. In addition, it is shown that quantitative information on the particle concentration can be obtained--which is not currently accessible from commercially available light scattering instrumentation. The results validate that MWT UV-Vis-NIR spectroscopy has a considerable dynamic range for particle size measurements and offers significant advantages over other particle characterization techniques. Among these are the simplicity of the instrumentation and the measurements and the wealth of quantitative information contained in the MWT spectra. Most importantly, with standardized measurement protocols and standardized spectrometer configurations, MWT measurements can be used to provide the user and the manufacturer of particles with traceable data (i.e., the spectra and the quantitative analysis) for quality assurance.

  5. Mapping chemical concentration in binary thin organic films via multi-wavelength scanning absorption microscopy (MWSAM)

    NASA Astrophysics Data System (ADS)

    Berriman, Garth; Routley, Ben; Holdsworth, John; Zhou, Xiaojing; Belcher, Warwick; Dastoor, Paul

    2014-09-01

    The composition and thickness of binary thin organic films is determined by measuring the optical absorption at multiple wavelengths across the film surface and performing a component analysis fit to absorption standards for the materials. The multiple laser wavelengths are focused onto the surface using microscope objectives and raster scanned across the film surface using a piezo-electric actuator X-Y stage. All of the wavelengths are scanned simultaneously with a frequency division multiplexing system used to separate the individual wavelength response. The composition values are in good quantitative agreement with measurements obtained by scanning transmission x-ray microscopy (STXM). This new characterization technique extends quantitative compositional mapping of thin films to thickness regimes beyond that accessible by STXM.

  6. Touch the Invisible Sky: A multi-wavelength Braille book featuring NASA images

    NASA Astrophysics Data System (ADS)

    Steel, S.; Grice, N.; Daou, D.

    2008-06-01

    Multi-wavelength astronomy - the study of the Universe at wavelengths beyond the visible, has revolutionised our understanding and appreciation of the cosmos. Hubble, Chandra and Spitzer are examples of powerful, space-based telescopes that complement each other in their observations spanning the electromagnetic spectrum. While several Braille books on astronomical topics have been published, to this point, no printed material accessible to the sight disabled or Braille reading public has been available on the topic of multi-wavelength astronomy. Touch the Invisible Sky presents the first printed introduction to modern, multi-wavelength astronomy studies to the disabled sight community. On a more fundamental level, tactile images of a Universe that had, until recently, been invisible to all, sighted or non-sighted, is an important learning message on how science and technology broadens our senses and our understanding of the natural world.

  7. Engineering reverse saturable absorbers for desired wavelengths

    NASA Astrophysics Data System (ADS)

    Band, Yehuda B.; Scharf, Benjamin

    1986-06-01

    A variety of applications exist for reverse saturable absorbers (RSAs) in laser science (RSAs are substances whose excited-state absorption cross section is larger than their ground-state absorption cross section at a given wavelength and possess a number of other properties). We propose an approach to designing RSAs at a desired wavelength by construction of dimers of dye molecules which absorb near the wavelength of interest. The dimer ground-state absorption is to a state in which the excitation is spread over both monomeric units and the excited-state absorption commences from this state to the doubly excited electronic state in which both monomeric units are excited.

  8. Magic wavelengths for terahertz clock transitions

    SciTech Connect

    Zhou Xiaoji; Xu Xia; Chen Xuzong; Chen Jingbiao

    2010-01-15

    Magic wavelengths for laser trapping of boson isotopes of alkaline-earth metal atoms Sr, Ca, and Mg are investigated while considering terahertz clock transitions between the {sup 3}P{sub 0}, {sup 3}P{sub 1}, and {sup 3}P{sub 2} metastable triplet states. Our calculation shows that magic wavelengths for laser trapping do exist. This result is important because those metastable states have already been used to make accurate clocks in the terahertz frequency domain. Detailed discussions for magic wavelengths for terahertz clock transitions are given in this article.

  9. Optical amplification at the 1. 31 wavelength

    DOEpatents

    Cockroft, N.J.

    1994-02-15

    An optical amplifier operating at the 1.31 [mu]m wavelength for use in such applications as telecommunications, cable television, and computer systems is described. An optical fiber or other waveguide device is doped with both Tm[sup 3+] and Pr[sup 3+] ions. When pumped by a diode laser operating at a wavelength of 785 nm, energy is transferred from the Tm[sup 3+] ions to the Pr[sup 3+] ions, causing the Pr[sup 3+] ions to amplify at a wavelength of 1.31. 1 figure.

  10. Laser wavelength metrology with color sensor chips.

    PubMed

    Jones, Tyler B; Otterstrom, Nils; Jackson, Jarom; Archibald, James; Durfee, Dallin S

    2015-12-14

    We present a laser wavelength meter based on a commercial color sensor chip. The chip consists of an array of photodiodes with different absorptive color filters. By comparing the relative amplitudes of light on the photodiodes, the wavelength of light can be determined. In addition to absorption in the filters, etalon effects add additional spectral features which improve the precision of the device. Comparing the measurements from the device to a commercial wavelength meter and to an atomic reference, we found that the device has picometer-level precision and picometer-scale drift over a period longer than a month. PMID:26699036

  11. Multimode fiber optic wavelength division multiplexing

    NASA Technical Reports Server (NTRS)

    Spencer, J. L.

    1982-01-01

    Optical wavelength division multiplexing (WDM) systems, with signals transmitted on different wavelengths through a single optical fiber, can have increased bandwidth and fault isolation properties over single wavelength optical systems. Two WDM system designs that might be used with multimode fibers are considered and a general description of the components which could be used to implement the system are given. The components described are sources, multiplexers, demultiplexers, and detectors. Emphasis is given to the demultiplexer technique which is the major developmental component in the WDM system.

  12. On-Line Wavelength Calibration of Pulsed Laser for CO2 Differential Absorption LIDAR

    NASA Astrophysics Data System (ADS)

    Xiang, Chengzhi; Ma, Xin; Han, Ge; Liang, Ailin; Gong, Wei

    2016-06-01

    Differential absorption lidar (DIAL) remote sensing is a promising technology for atmospheric CO2 detection. However, stringent wavelength accuracy and stability are required in DIAL system. Accurate on-line wavelength calibration is a crucial procedure for retrieving atmospheric CO2 concentration using the DIAL, particularly when pulsed lasers are adopted in the system. Large fluctuations in the intensities of a pulsed laser pose a great challenge for accurate on-line wavelength calibration. In this paper, a wavelength calibration strategy based on multi-wavelength scanning (MWS) was proposed for accurate on-line wavelength calibration of a pulsed laser for CO2 detection. The MWS conducted segmented sampling across the CO2 absorption line with appropriate number of points and range of widths by using a tunable laser. Complete absorption line of CO2 can be obtained through a curve fitting. Then, the on-line wavelength can be easily found at the peak of the absorption line. Furthermore, another algorithm called the energy matching was introduced in the MWS to eliminate the backlash error of tunable lasers during the process of on-line wavelength calibration. Finally, a series of tests was conducted to elevate the calibration precision of MWS. Analysis of tests demonstrated that the MWS proposed in this paper could calibrate the on-line wavelength of pulsed laser accurately and steadily.

  13. Near infrared imaging of teeth at wavelengths between 1200 and 1600 nm

    NASA Astrophysics Data System (ADS)

    Chung, Soojeong; Fried, Daniel; Staninec, Michal; Darling, Cynthia L.

    2011-03-01

    Near-IR (NIR) imaging is a new technology that is currently being investigated for the detection and assessment of dental caries without the use of ionizing radiation. Several papers have been published on the use of transillumination and reflectance NIR imaging to detect early caries in enamel. The purpose of this study was to investigate alternative near infrared wavelengths besides 1300-nm in the range from 1200- 1600-nm to determine the wavelengths that yield the highest contrast in both transmission and reflectance imaging modes. Artificial lesions were created on thirty tooth sections of varying thickness for transillumination imaging. NIR images at wavelengths from the visible to 1600-nm were also acquired for fifty-four whole teeth with occlusal lesions using a tungsten halogen lamp with several spectral filters and a Ge-enhanced CMOS image sensor. Cavity preparations were also cut into whole teeth and Z250 composite was used as a restorative material to determine the contrast between composite and enamel at NIR wavelengths. Slightly longer NIR wavelengths are likely to have better performance for the transillumination of occlusal caries lesions while 1300-nm appears best for the transillumination of proximal surfaces. Significantly higher performance was attained at wavelengths that have higher water absorption, namely 1460-nm and wavelengths greater than 1500-nm and these wavelength regions are likely to be more effective for reflectance imaging. Wavelengths with higher water absorption also provided higher contrast of composite restorations.

  14. A near infrared optimal wavelength imaging method for detection of foreign materials

    NASA Astrophysics Data System (ADS)

    Lu, De-Hao

    2008-03-01

    The objective of this research was to develop an optimal wavelength imaging system for detecting foreign materials in the NIR (near infrared) region from 750 nm to 2500 nm. This method is based on the principle that different fibers have different spectral absorptions and reflectance characteristic. When submitted to a source of illumination at different wavelength, foreign materials present different reflectance values in comparison to those from cotton fibers. For simultaneously discriminating several types of foreign materials from cotton, the optimal wavelength evaluation function for describing the cotton/foreign materials absorption discrimination was set up. Through the Fourier transform spectrometer experiment, the optimal wavelength for these detected foreign materials was determined and accordingly an optimal wavelength imaging system was developed. The wavelength selection experiment showed that the 940 nm wavelength was the most appropriate for detection of a wide range of foreign materials in cotton, and the 940 nm wavelength imaging system gave the clear image features of these foreign materials. The result suggests that use of NIR optimal wavelength imaging technique is a feasible and effective method to detect foreign materials in cotton, which are currently difficult for sorting.

  15. Measuring atmospheric dispersion with WLRS in multiple wavelength mode

    NASA Technical Reports Server (NTRS)

    Schreiber, Ulrich; Haufe, K. H.; Dassing, Reiner

    1993-01-01

    The WLRS (Wettzell Laser Ranging System) allows the simultaneous tracking of satellites on two different wavelengths. These are the fundamental frequency of Nd:YAG at 1.064 microns and the second harmonic at 532 nm. Range measurements to the satellite LAGEOS were carried out with different experimental set-ups, after developing a detector unit based on a silicon avalanche photodiode in Geiger mode, which is sufficiently sensitive in the infrared domain. An approach towards a quantitative interpretation of the data is suggested and discussed briefly.

  16. Superconductor Semiconductor Research for NASA's Submillimeter Wavelength Missions

    NASA Technical Reports Server (NTRS)

    Crowe, Thomas W.

    1997-01-01

    Wideband, coherent submillimeter wavelength detectors of the highest sensitivity are essential for the success of NASA's future radio astronomical and atmospheric space missions. The critical receiver components which need to be developed are ultra- wideband mixers and suitable local oscillator sources. This research is focused on two topics, (1) the development of reliable varactor diodes that will generate the required output power for NASA missions in the frequency range from 300 GHZ through 2.5 THz, and (2) the development of wideband superconductive mixer elements for the same frequency range.

  17. All-fiber wavelength swept ring laser based on Fabry-Perot filter for optical frequency domain imaging.

    PubMed

    Jun, Changsu; Villiger, Martin; Oh, Wang-Yuhl; Bouma, Brett E

    2014-10-20

    Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral range. The design can easily be optimized to meet a range of operating specifications while yielding robust and stable performance. As an example, we demonstrate 240 kHz operation with 125 nm sweep range and >70 mW of average output power and demonstrate high quality frequency domain OCT imaging. The complete component list and directions for assembly of the laser are posted on-line at www.octresearch.org.

  18. All-fiber wavelength swept ring laser based on Fabry-Perot filter for optical frequency domain imaging

    PubMed Central

    Jun, Changsu; Villiger, Martin; Oh, Wang-Yuhl; Bouma, Brett E.

    2014-01-01

    Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral range. The design can easily be optimized to meet a range of operating specifications while yielding robust and stable performance. As an example, we demonstrate 240 kHz operation with 125 nm sweep range and >70 mW of average output power and demonstrate high quality frequency domain OCT imaging. The complete component list and directions for assembly of the laser are posted on-line at www.octresearch.org. PMID:25401614

  19. All-fiber wavelength swept ring laser based on Fabry-Perot filter for optical frequency domain imaging.

    PubMed

    Jun, Changsu; Villiger, Martin; Oh, Wang-Yuhl; Bouma, Brett E

    2014-10-20

    Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral range. The design can easily be optimized to meet a range of operating specifications while yielding robust and stable performance. As an example, we demonstrate 240 kHz operation with 125 nm sweep range and >70 mW of average output power and demonstrate high quality frequency domain OCT imaging. The complete component list and directions for assembly of the laser are posted on-line at www.octresearch.org. PMID:25401614

  20. Multiple wavelength photolithography for preparing multilayer microstructures

    SciTech Connect

    Dentinger, Paul Michael; Krafcik, Karen Lee

    2003-06-24

    The invention relates to a multilayer microstructure and a method for preparing thereof. The method involves first applying a first photodefinable composition having a first exposure wavelength on a substrate to form a first polymeric layer. A portion of the first photodefinable composition is then exposed to electromagnetic radiation of the first exposure wavelength to form a first pattern in the first polymeric layer. After exposing the first polymeric layer, a second photodefinable composition having a second exposure wavelength is applied on the first polymeric layer to form a second polymeric layer. A portion of the second photodefinable composition is then exposed to electromagnetic radiation of the second exposure wavelength to form a second pattern in the second polymeric layer. In addition, a portion of each layer is removed according to the patterns to form a multilayer microstructure having a cavity having a shape that corresponds to the portions removed.

  1. Multiple-Wavelength Pyrometry Independent Of Emissivity

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1996-01-01

    Multiple-wavelength pyrometric method provides for determination of two sequential temperatures of same surface or temperatures of two surfaces made of same material. Temperatures measured, without knowing emissivity, by uncalibrated spectral radiometer.

  2. Controllable Dual-Wavelength Fiber Laser

    NASA Astrophysics Data System (ADS)

    Li, Zhen; Zhou, Jun; He, Bing; Liu, Hou-Kang; Liu, Chi; Wei, Yun-Rong; Dong, Jing-Xing; Lou, Qi-Hong

    2012-07-01

    We demonstrate a controllable dual-wavelength fiber laser which contains a master laser and a slave laser. The master laser is a kind of ring cavity laser which can be injected into by the slave laser. The output laser wavelength is controlled by injected power of the slave laser; both single- and dual-wavelength operation can be achieved. Under free running, the master laser generates 1064 nm laser output. Here the slave laser is a 1072 nm fiber laser. The 1064 nm and 1072 nm laser coexist in output spectrum for relatively low injected power. Dual-wavelength and power-ratio-tunable operation can be achieved. If the injected power of the slave laser is high enough, the 1064 nm laser is extinguished automatically and there is only 1072 nm laser output.

  3. Wavelength mismatch effect in electromagnetically induced absorption

    NASA Astrophysics Data System (ADS)

    Bharti, Vineet; Wasan, Ajay; Natarajan, Vasant

    2016-07-01

    We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch-near-perfect match where all three wavelengths are approximately equal; partial mismatch where the wavelength of one control field is less than the other fields; and complete mismatch where all three wavelengths are unequal. We present probe absorption profiles with Doppler averaging at room temperature to account for experiments in a room temperature Rb vapor cell. Our analysis shows that EIA resonances can be studied using Rydberg states excited with diode lasers.

  4. Grating cavity dual wavelength dye laser.

    PubMed

    Zapata-Nava, Oscar Javier; Rodríguez-Montero, Ponciano; Iturbe-Castillo, M David; Treviño-Palacios, Carlos Gerardo

    2011-02-14

    We report simultaneous dual wavelength dye laser emission using Littman-Metcalf and Littrow cavity configurations with minimum cavity elements. Dual wavelength operation is obtained by laser operation in two optical paths inside the cavity, one of which uses reflection in the circulating dye cell. Styryl 14 laser dye operating in the 910 nm to 960 nm was used in a 15%:85% PC/EG solvent green pumped with a Q-switched doubled Nd3+:YAG laser. PMID:21369171

  5. Silicon photonic crystal thermal emitter at near-infrared wavelengths

    PubMed Central

    O’Regan, Bryan J.; Wang, Yue; Krauss, Thomas F.

    2015-01-01

    Controlling thermal emission with resonant photonic nanostructures has recently attracted much attention. Most of the work has concentrated on the mid-infrared wavelength range and/or was based on metallic nanostructures. Here, we demonstrate the experimental operation of a resonant thermal emitter operating in the near-infrared (≈1.5 μm) wavelength range. The emitter is based on a doped silicon photonic crystal consisting of a two dimensional square array of holes and using silicon-on-insulator technology with a device-layer thickness of 220 nm. The device is resistively heated by passing current through the photonic crystal membrane. At a temperature of ≈1100 K, we observe relatively sharp emission peaks with a Q factor around 18. A support structure system is implemented in order to achieve a large area suspended photonic crystal thermal emitter and electrical injection. The device demonstrates that weak absorption together with photonic resonances can be used as a wavelength-selection mechanism for thermal emitters, both for the enhancement and the suppression of emission. PMID:26293111

  6. Monolithic Fabry-Perot Wavelength Tunable Filter with Electrothermal Actuation

    NASA Astrophysics Data System (ADS)

    Kim, Chang Kyu; Lee, Myung Lae; Jun, Chi-Hoon; Choi, Chang Auck

    2005-02-01

    We report on a micromachined monolithic Fabry-Perot wavelength tunable filter with a thick moving structure operated by an electrothermal actuation. The monolithic structure simplifies the fabrication process and the electrothermal actuation mechanism reduces the required operation voltage. For the wet etching of the AlGaAs sacrificial layer, an HCl-based solution rather than a HF-based one was used because it results in a larger selectivity between the AlxGa1-xAs layers and less damage to the suspended structure. The wavelength tuning range of the 7.64-μm-thick structure was 47 nm for the power consumption of 5 mW, which results in the high tuning efficiency of ˜9.9 nm/mW. The wide tuning range of 81.2 nm for the 5.2-μm-thick structure, that is not possible with an electrostatic actuation mechanism due to the occurrence of breakdown, is achieved at the driving voltage below 5.7 V. Due to the simplicity of fabrication and the ease of integration, this structure is advantageous for use in wavelength tunable light sources and photodetectors.

  7. Silicon photonic crystal thermal emitter at near-infrared wavelengths.

    PubMed

    O'Regan, Bryan J; Wang, Yue; Krauss, Thomas F

    2015-08-21

    Controlling thermal emission with resonant photonic nanostructures has recently attracted much attention. Most of the work has concentrated on the mid-infrared wavelength range and/or was based on metallic nanostructures. Here, we demonstrate the experimental operation of a resonant thermal emitter operating in the near-infrared (≈1.5 μm) wavelength range. The emitter is based on a doped silicon photonic crystal consisting of a two dimensional square array of holes and using silicon-on-insulator technology with a device-layer thickness of 220 nm. The device is resistively heated by passing current through the photonic crystal membrane. At a temperature of ≈1100 K, we observe relatively sharp emission peaks with a Q factor around 18. A support structure system is implemented in order to achieve a large area suspended photonic crystal thermal emitter and electrical injection. The device demonstrates that weak absorption together with photonic resonances can be used as a wavelength-selection mechanism for thermal emitters, both for the enhancement and the suppression of emission.

  8. Measurement of the shape of objects by two wavelength interferometry

    NASA Astrophysics Data System (ADS)

    Pavlíček, Pavel; Naik, Dinesh N.

    2013-06-01

    We propose a fast and precise optical 3D measurement method. The principle is similar to that of white-light interferometry. The broad-band light source of white-light interferometry is replaced by two lasers with different wavelengths. The object to be measured is placed into one arm of a Michelson interferometer and moved along the optical axis. The intensity measured at the output of the interferometer is equal to the field autocorrelation. In the case of two wavelengths, the autocorrelation is a periodical function with peaks as a result of their beating. The period can be adjusted by the choice of the wavelength difference. By choosing a short period, a fast and precise measurement is performed in the range of a single beat. However, such a measurement is ambiguous if the object has structures deeper than the beat period. The ambiguity is removed by a fast auxiliary measurement with a long beat period covering the whole depth range of the object. The auxiliary measurement need not be precise and can be completed quickly with a large sampling step.

  9. Sensor Technology at Submillimeter Wavelengths for Space Applications

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Goutam

    2007-01-01

    Our universe is most luminous at far-infrared and submillimeter wavelengths (100 GHz - 10 THz) after the Cosmic Microwave Background (CMB) radiation. This region of the electromagnetic spectrum provides critical tracers for the study of a wide range of astrophysical and planetary phenomena. This spectral range contains information on the origin of the planets, stars, galaxies, and clusters; the geometry and matter/energy content of the Universe, atmospheric constituents and dynamics of the planets and comets and tracers for global monitoring and the ultimate health of the Earth. Sensors at far-infrared and submillimeter wavelengths provide unprecedented sensitivity for astrophysical, planetary, and earth observing instruments. Very often, for a spaced based platform where the instruments are not limited by atmospheric losses and absorption, the overall instrument sensitivity is dictated by the sensitivity of the sensors themselves. Moreover, some of the cryogenic sensors at submillimeter wavelengths provide almost quantum-limited sensitivity. This paper provides an overview of the submillimeter-wave sensors and their performance and capabilities for space applications.

  10. Phase determination by wavelength-modulated diffraction. I. Centrosymmetric case.

    PubMed

    Koganezawa, T; Yoshimura, Y; Nakamura, N; Iwasaki, H

    2001-05-01

    Wavelength-modulated diffraction was developed by Iwasaki, Yurugi & Yoshimura [Acta Cryst. (1999), A55, 864-870] as a method for phase determination, in which the intensity of Bragg reflections is recorded using radiation whose wavelength is changing continually over a range in the vicinity of the absorption edge of an atom in the crystal. Using a ferrocene derivative crystal (chemical formula C36H32O7Fe, space group P2(1)/a) with the Fe atoms chosen as anomalous scatterers, measurements were made of the intensity gradient dI/d lambda of the reflections with an imaging plate as a detector on a synchrotron radiation source at Ritsumeikan University. In the case of a centrosymmetric crystal, the phase of the structure factor could be derived by measuring only the sign of dI/d lambda at one wavelength in the range. Of 104 reflections measured, the correct phase was assigned to 101 reflections. A discussion is given on the errors involved and on the limits of application of the method.

  11. Dual-Wavelength Terahertz Metasurfaces with Independent Phase and Amplitude Control at Each Wavelength

    NASA Astrophysics Data System (ADS)

    Ding, Jun; Xu, Ningning; Ren, Han; Lin, Yuankun; Zhang, Weili; Zhang, Hualiang

    2016-09-01

    We have designed, fabricated and characterized dual-wavelength metasurfaces that function at two assigned terahertz wavelengths with independent phase and amplitude control at each wavelength. Specifically, we have designed a dual-wavelength achromatic metasurface-based deflector deflecting the incident wave to the same direction at two selected wavelengths, which has circumvented the critical limitation of strong wavelength dependence in the planar metasurface-based devices caused by the resonant nature of the plasmonic structures. As a proof of concept demonstration, the designed dual-wavelength achromatic deflector has been fabricated, and characterized experimentally. The numerical simulations, theoretical predictions, and experimental results agree very well with each other, demonstrating the property of independently manipulating the phase profiles at two wavelengths. Furthermore, another unique feature of the designed metasurface is that it can independently tailor both the phase and amplitude profiles at two wavelengths. This property has been numerically validated by engineering a metasurface-based device to simultaneously generate two diffraction orders at two desired wavelengths.

  12. Dual-Wavelength Terahertz Metasurfaces with Independent Phase and Amplitude Control at Each Wavelength

    PubMed Central

    Ding, Jun; Xu, Ningning; Ren, Han; Lin, Yuankun; Zhang, Weili; Zhang, Hualiang

    2016-01-01

    We have designed, fabricated and characterized dual-wavelength metasurfaces that function at two assigned terahertz wavelengths with independent phase and amplitude control at each wavelength. Specifically, we have designed a dual-wavelength achromatic metasurface-based deflector deflecting the incident wave to the same direction at two selected wavelengths, which has circumvented the critical limitation of strong wavelength dependence in the planar metasurface-based devices caused by the resonant nature of the plasmonic structures. As a proof of concept demonstration, the designed dual-wavelength achromatic deflector has been fabricated, and characterized experimentally. The numerical simulations, theoretical predictions, and experimental results agree very well with each other, demonstrating the property of independently manipulating the phase profiles at two wavelengths. Furthermore, another unique feature of the designed metasurface is that it can independently tailor both the phase and amplitude profiles at two wavelengths. This property has been numerically validated by engineering a metasurface-based device to simultaneously generate two diffraction orders at two desired wavelengths. PMID:27659800

  13. Semiconductor plasmonic metamaterials for near-infrared and telecommunication wavelength

    NASA Astrophysics Data System (ADS)

    Naik, Gururaj V.; Shalaev, Vladimir M.; Boltasseva, Alexandra

    2010-08-01

    Plasmonic materials have conventionally been gold and silver in optical frequencies. However, these conventional metals in the near-infrared (NIR) and visible spectral ranges suffer from problems such as large losses. With the advent of metamaterials, these metals pose a serious bottle-neck in the performances of metamaterial-based devices not only due to the large losses associated with them in the NIR and visible wavelengths, but also their magnitudes of real permittivity are too large. Both of these problems could be solved by using semiconductors as plasmonic materials. Heavily doped zinc oxide and indium oxide can exhibit losses that are nearly four times smaller than silver at the telecommunication wavelength with small negative real permittivity. In this paper, we present the development of a low loss semiconductor plasmonic material, aluminum doped zinc oxide (AZO).

  14. The albedos of Pluto and Charon - Wavelength dependence

    NASA Technical Reports Server (NTRS)

    Marcialis, Robert L.; Lebofsky, Larry A.; Disanti, Michael A.; Fink, Uwe; Tedesco, Edward F.; Africano, John

    1992-01-01

    The March 3, 1987 occultation of Charon by Pluto was monitored simultaneously with three telescopes. Each site covered a distinct wavelength interval with the total range spanning 0.44-2.4 microns. Observing the same event ensures an identical sun-Pluto-earth geometry for all three sites, and minimizes the assumptions which must be made to combine results. This spectrophotometry is used to derive the individual geometric albedos of Pluto and Charon over a factor of at least 5 in wavelength. Combining the results with those of Binzel (1988) improved (B - V) color estimates (on the 'Johnson Pluto' system) are obtained for the components of the system at rotational phase 0.75: (Pluto + Charon) = 0.843 +/- 0.006; Pluto alone = 0.866 +/- 0.007; and Charon alone = 0.702 +/- 0.010.

  15. The effects of wavelength on coherent Doppler lidar performance

    NASA Technical Reports Server (NTRS)

    Lawrence, T. R.

    1985-01-01

    Hitherto, long-range wind-sensing coherent (heterodyne) lidars have utilized CO2 lasers (operating at a 10-micrometer wavelength) since these were the only high-power single-mode (spatial and axial) pulsed sources available. This property ensures temporal coherence over the required spatial resolution, e.g., the pulse length. Recent developments in Nd:YAG lasers makes possible the consideration of a 1.06-micrometer source (Kane et al., 1984). The relative merit of operation at various wavelengths is a function of system parameter, backscattering cross section, signal processing, beam propagation, and practical and eye safety considerations. These factors are discussed in the context of a global wind-sensing coherent lidar.

  16. Switchable multi-wavelength fiber laser based on modal interference

    NASA Astrophysics Data System (ADS)

    Ma, Lin; Jiang, Sun; Qi, Yan-Hui; Kang, Ze-Xin; Jian, Shui-Sheng

    2015-08-01

    A comb fiber filter based on modal interference is proposed and demonstrated in this paper. Here two cascaded up-tapers are used to excite the cladding mode, and a core-offset jointing point is used to act as an interference component. Experimental results show that this kind of structure possesses a comb filter property in a range of the C-band. The measured extinction ratio is better than 12 dB with an insertion loss of about 11 dB. A switchable multi-wavelength erbium-doped fiber laser based on this novel comb filter is demonstrated. By adjusting the polarization controller, the output laser can be switched among single-, dual-, and three-wavelengths with a side mode suppression ratio of better than 45 dB.

  17. MULTI-WAVELENGTH AFTERGLOWS OF FAST RADIO BURSTS

    SciTech Connect

    Yi, Shuang-Xi; Gao, He; Zhang, Bing

    2014-09-01

    The physical origin of fast radio bursts (FRBs) is unknown. Detecting electromagnetic counterparts to FRBs in other wavelengths is essential to measure their distances and to determine their physical origin. Assuming that at least some of them are of cosmological origin, we calculate their afterglow light curves in multiple wavelengths (X-rays, optical, and radio) by assuming a range of total kinetic energies and redshifts. We focus on forward shock emission, but also consider the possibility that some of the FRBs might have bright reverse shock emission. In general, FRB afterglows are too faint to be detected by current detectors. Only if an FRB has a very low radiative efficiency in radio (hence, a very large kinetic energy), and when it is close enough to observe can its afterglow be detected in the optical and radio bands. We discuss observational strategies for detecting these faint afterglows using future telescopes such as Large Synoptic Survey Telescope and Expanded Very Large Array.

  18. Bichromophoric Dyes for Wavelength Shifting of Dye-Protein Fluoromodules

    PubMed Central

    Pham, Ha H.; Szent-Gyorgyi, Christopher; Brotherton, Wendy L.; Schmidt, Brigitte F.; Zanotti, Kimberly J.; Waggoner, Alan S.

    2015-01-01

    Dye-protein fluoromodules consist of fluorogenic dyes and single chain antibody fragments that form brightly fluorescent noncovalent complexes. This report describes two new bichromophoric dyes that extend the range of wavelengths of excitation or emission of existing fluoromodules. In one case, a fluorogenic thiazole orange (TO) was attached to an energy acceptor dye, Cy5. Upon binding to a protein that recognizes TO, red emission due to efficient energy transfer from TO to Cy5 replaces the green emission observed for monochromophoric TO bound to the same protein. Separately, TO was attached to a coumarin that serves as an energy donor. The same green emission is observed for coumarin-TO and TO bound to a protein, but efficient energy transfer allows violet excitation of coumarin-TO, versus longer wavelength, blue excitation of monochromophoric TO. Both bichromophores exhibit low nanomolar KD values for their respective proteins, >95% energy transfer efficiency and high fluorescence quantum yields. PMID:25679477

  19. Short wavelength limits of current shot noise suppression

    SciTech Connect

    Nause, Ariel; Dyunin, Egor; Gover, Avraham

    2014-08-15

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

  20. Displacement interferometry with stabilization of wavelength in air.

    PubMed

    Lazar, Josef; Holá, Miroslava; Cíp, Ondřej; Cížek, Martin; Hrabina, Jan; Buchta, Zdeněk

    2012-12-01

    We present a concept of suppression of the influence of variations of the refractive index of air in displacement measuring interferometry. The principle is based on referencing of wavelength of the coherent laser source in atmospheric conditions instead of traditional stabilization of the optical frequency and indirect evaluation of the refractive index of air. The key advantage is in identical beam paths of the position measuring interferometers and the interferometer used for the wavelength stabilization. Design of the optical arrangement presented here to verify the concept is suitable for real interferometric position sensing in technical practice especially where a high resolution measurement within some limited range in atmospheric conditions is needed, e.g. in nanometrology.

  1. Evaluation of wavelength groups for discrimination of agricultural cover types. [remote sensing of environment in INDIANA

    NASA Technical Reports Server (NTRS)

    Kumar, R.

    1978-01-01

    Multispectral scanner data in twelve spectral channels, in the wavelength range 0.46 to 11.7 mm, acquired in July 1971 for three flightlines, were analyzed by applying automatic pattern recognition techniques. These twelve spectral channels were divided into four wavelength groups (W1, W2, W3 and W4), each consisting of three wavelength channels -- with respect to their estimated probability of correct classification (P sub c) in discriminating agricultural cover types. The same analysis was also done for the data acquired in August, to investigate the effect of time on these results. The effect of deletion of each of the wavelength groups on P sub C in the subsets of one to nine channels, is given. Values of P sub C for all possible combinations of wavelength groups, in the subsets of one to eleven channels are also given.

  2. Fast wavelength calibration method for spectrometers based on waveguide comb optical filter

    SciTech Connect

    Yu, Zhengang; Huang, Meizhen Zou, Ye; Wang, Yang; Sun, Zhenhua; Cao, Zhuangqi

    2015-04-15

    A novel fast wavelength calibration method for spectrometers based on a standard spectrometer and a double metal-cladding waveguide comb optical filter (WCOF) is proposed and demonstrated. By using the WCOF device, a wide-spectrum beam is comb-filtered, which is very suitable for spectrometer wavelength calibration. The influence of waveguide filter’s structural parameters and the beam incident angle on the comb absorption peaks’ wavelength and its bandwidth are also discussed. The verification experiments were carried out in the wavelength range of 200–1100 nm with satisfactory results. Comparing with the traditional wavelength calibration method based on discrete sparse atomic emission or absorption lines, the new method has some advantages: sufficient calibration data, high accuracy, short calibration time, fit for produce process, stability, etc.

  3. Mechanism of wavelength conversion in polystyrene doped with benzoxanthene: emergence of a complex

    PubMed Central

    Nakamura, Hidehito; Shirakawa, Yoshiyuki; Kitamura, Hisashi; Sato, Nobuhiro; Shinji, Osamu; Saito, Katashi; Takahashi, Sentaro

    2013-01-01

    Fluorescent guest molecules doped in polymers have been used to convert ultraviolet light into visible light for applications ranging from optical fibres to filters for the cultivation of plants. The wavelength conversion process involves the absorption of light at short wavelengths followed by fluorescence emission at a longer wavelength. However, a precise understanding of the light conversion remains unclear. Here we show light responses for a purified polystyrene base substrates doped with fluorescent benzoxanthene in concentrations varied over four orders of magnitude. The shape of the excitation spectrum for fluorescence emission changes significantly with the concentration of the benzoxanthene, indicating formation of a base substrate/fluorescent molecule complex. Furthermore, the wavelength conversion light yield increases in three stages depending on the nature of the complex. These findings identify a mechanism that will have many applications in wavelength conversion materials. PMID:23974205

  4. Wavelength dependence of mycosporine-like amino acid synthesis in Gyrodinium dorsum.

    PubMed

    Klisch, M; Häder, D-P

    2002-02-01

    The synthesis or accumulation of mycosporine-like amino acids (MAAs) is an important UV tolerance mechanism in aquatic organisms. To investigate the wavelength dependence of MAA synthesis in the marine dinoflagellate Gyrodinium dorsum, the organism was exposed to polychromatic radiation (PAR and UV) from a solar simulator for up to 72 h. Different irradiance spectra were produced by inserting various cut-off filters between lamp and samples. A polychromatic action spectrum for the synthesis of MAA synthesis was constructed. PAR and long wavelength UV-A radiation showed almost no effect while the most effective wavelength range was around 310 nm. Shorter wavelengths where less effective in the induction of MAA synthesis. Wavelengths below 300 nm damaged the organisms severely as indicated by a decrease in chlorophyll a absorption.

  5. Wavelength tunable integrated add-drop filter with 10.6 nm bandwidth adjustability.

    PubMed

    Boroojerdi, M T; Ménard, M; Kirk, A G

    2016-09-19

    We present the design and characterization of a silicon-on-insulator based bandwidth and wavelength-tunable add-drop filter. The tunability of the device is achieved by independently controlling the central wavelength of two cascaded contra-directional grating assisted couplers. The device was fabricated using e-beam lithography and the tuning is demonstrated using the thermo-optic effect, which was obtained with metal heaters fabricated by a lift-off process. It is experimentally demonstrated that within the wavelength range of 1555 nm to 1573 nm the transmission bandwidth of the device can be tuned from 1.1 nm to 11.7 nm. Moreover, more than 4 nm of central wavelength tuning is demonstrated. The tunability of the central wavelength is limited by the breakdown current of the metal heaters. PMID:27661939

  6. The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence

    SciTech Connect

    Newman, D.E.

    1993-09-01

    Because of the ubiquitous nature of turbulence and the vast array of different systems which have turbulent solutions, the study of turbulence is an area of active research. Much present day understanding of turbulence is rooted in the well established properties of homogeneous Navier-Stokes turbulence, which, due to its relative simplicity, allows for approximate analytic solutions. This work examines a group of turbulent systems with marked differences from Navier-Stokes turbulence, and attempts to quantify some of their properties. This group of systems represents a variety of drift wave fluctuations believed to be of fundamental importance in laboratory fusion devices. From extensive simulation of simple local fluid models of long wavelength drift wave turbulence in tokamaks, a reasonably complete picture of the basic properties of spectral transfer and saturation has emerged. These studies indicate that many conventional notions concerning directions of cascades, locality and isotropy of transfer, frequencies of fluctuations, and stationarity of saturation are not valid for moderate to long wavelengths. In particular, spectral energy transfer at long wavelengths is dominated by the E {times} B nonlinearity, which carries energy to short scale in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade dynamics of Kolmogorov, energy is efficiently passed between modes separated by the entire spectrum range in a correlation time. At short wavelengths, transfer is dominated by the polarization drift nonlinearity. While the standard dual cascade applies in this subrange, it is found that finite spectrum size can produce cascades that are reverse directed and are nonconservative in enstrophy and energy similarity ranges. In regions where both nonlinearities are important, cross-coupling between the nolinearities gives rise to large no frequency shifts as well as changes in the spectral dynamics.

  7. Detection of foreign fibers in cotton using near-infrared optimal wavelength imaging

    NASA Astrophysics Data System (ADS)

    Jia, Dongyao; Ding, Tianhuai

    2005-07-01

    The objective of this research was to develop an optimal wavelength imaging system for detecting foreign fibers in the near infrared (NIR) region from 750 to 2500 nm. This method is based on the principle that different fibers have different spectral absorptions and reflectance characteristics. When subjected to a source of illumination at different wavelengths, foreign fibers present different reflectance values from those of cotton fibers. For simultaneously discriminating several types of foreign fibers from cotton, an optimal wavelength evaluation function for describing the cotton-foreign-fiber absorption discrimination was set up. Through a Fourier transform spectrometer experiment, the optimal wavelength for detecting these foreign fibers was determined and accordingly an optimal wavelength imaging system was developed. The wavelength selection experiment showed that 940 nm was the most appropriate wavelength for detection of a wide range of foreign fibers in cotton, and the 940-nm imaging system gave clear image features of these foreign fibers. The result suggests that NIR optimal wavelength imaging is a feasible and effective method to detect foreign fibers in cotton, which are currently difficult to detect.

  8. Polarized thermal radiation by layer-by-layer metallic emitters with sub-wavelength grating.

    PubMed

    Lee, Jae-Hwang; Leung, Wai; Kim, Tae Guen; Constant, Kristen; Ho, Kai-Ming

    2008-06-01

    Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 mum, as well as high emissivity up to 0.65 at a wavelength of 3.7 microm. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization. PMID:18545587

  9. Cryogenic Amplifier Based Receivers at Submillimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Goutam; Reck, Theodore and; Schlecht, Erich; Lin, Robert; Deal, William

    2012-01-01

    The operating frequency of InP high electron mobility transistor (HEMT) based amplifiers has moved well in the submillimeter-wave frequencies over the last couple of years. Working amplifiers with usable gain in waveguide packages has been reported beyond 700 GHz. When cooled cryogenically, they have shown substantial improvement in their noise temperature. This has opened up the real possibility of cryogenic amplifier based heterodyne receivers at submillimeter wavelengths for ground-based, air-borne, and space-based instruments for astrophysics, planetary, and Earth science applications. This paper provides an overview of the science applications at submillimeter wavelengths that will benefit from this technology. It also describes the current state of the InP HEMT based cryogenic amplifier receivers at submillimeter wavelengths.

  10. Integrated nonlinear interferometer with wavelength multicasting functionality.

    PubMed

    Yang, Weili; Yu, Yu; Zhang, Xinliang

    2016-08-01

    Nonlinear interference based on four wave mixing (FWM) is extremely attractive due to its phase sensitivity. On the other hand, wavelength multicasting, which supports data point-to-multipoint connections, is a key functionality to increase the network efficiency and simplify the transmitter and receiver in the wavelength-division multiplexing systems. We propose and experimentally demonstrate a nonlinear interferometer with wavelength multicasting functionality based on single-stage FWM in an integrated silicon waveguide. With a three-pump and dual-signal input, four phase sensitive idlers are obtained at the interferometer output. For a proof-of-concept application, we further theoretically demonstrate the multicasting logic exclusive-OR (XOR) gate for both intensity and phase modulated signals. The proposed scheme would be potentially applied in various on-chip applications for future optical communication system. PMID:27505786

  11. Device for wavelength-selective imaging

    SciTech Connect

    Frangioni, John V.

    2010-09-14

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

  12. Mechanisms and Methods for Selective Wavelength Filtering

    NASA Technical Reports Server (NTRS)

    Tuma, Margaret (Inventor); Brown, Thomas G. (Inventor); Gruhlke, Russell (Inventor)

    2007-01-01

    An optical filter includes a dielectric waveguide layer, supporting waveguide modes at specific wavelengths and receiving incident light, a corrugated film layer, composed of one of a metal and a semiconductor and positioned adjacent to a second surface of the waveguide layer and a sensor layer, wherein the sensor layer is capable of absorbing optical energy and generating a corresponding electrical signal. The metal film layer supports a plurality of plasmons, the plurality of plasmons producing a first field and is excited by a transverse mode of the waveguide modes at a wavelength interval. The first field penetrates the sensor layer and the sensor layer generates an electrical signal corresponding to an intensity of received incident light within the wavelength interval.

  13. Dynamic polarizabilities and magic wavelengths for dysprosium

    SciTech Connect

    Dzuba, V. A.; Flambaum, V. V.; Lev, Benjamin L.

    2011-03-15

    We theoretically study dynamic scalar polarizabilities of the ground and select long-lived excited states of dysprosium, a highly magnetic atom recently laser cooled and trapped. We demonstrate that there is a set of magic wavelengths of the unpolarized lattice laser field for each pair of states, which includes the ground state and one of these excited states. At these wavelengths, the energy shift due to laser field is the same for both states, which can be useful for resolved sideband cooling on narrow transitions and precision spectroscopy. We present an analytical formula that, near resonances, allows for the determination of approximate values of the magic wavelengths without calculating the dynamic polarizabilities of the excited states.

  14. Debunking the recurring myth of a magic wavelength for free-space optics

    NASA Astrophysics Data System (ADS)

    Korevaar, Eric J.; Kim, Isaac I.; McArthur, Bruce

    2002-12-01

    Free-Space Optics (FSO) is a proven, reliable technology for last mile telecommunications applications, used worldwide for both enterprise network building-to-building connections and for wireless access to more traditional land line communications networks. In most mid-latitude coastal cities, link availability at distances above a few hundred meters is primarily affected by fog and low clouds. At longer distances, heavy rain and snow can also affect the link. The most mature technology used in FSO equipment relies on low cost semiconductor lasers or LED"s operating in the near infrared at wavelengths of 785 nm or 850 nm. In the past few years, systems operating at 1550 nm have also been developed. At first the vendors of these systems claimed that the 1550 nm wavelength had better propagation characteristics in severe weather than the 785 nm wavelength. With further analysis and research, those claims were withdrawn. Now there are claims that even longer wavelengths near 10 microns will solve the FSO link availability issues associated with severe weather. Hype about such magic wavelengths for FSO is both a disservice to the investors who will lose the money they are investing based on exaggerated claims, and to the rest of the FSO industry which should be creating realistic expectations for the capability of its equipment. In the weather conditions which normally cause the highest attenuation for FSO systems, namely coastal fog and low clouds, 10 microns offers no propagation advantage over shorter wavelengths.

  15. [Dual-wavelength Mie lidar observations of tropospheric aerosols].

    PubMed

    Chi, Ru-Li; Wu, De-Cheng; Liu, Bo; Zhou, Jun

    2009-06-01

    A new dual-wavelength Mie lidar (DWL) is introduced. The DWL can be used to monitor the optical properties of tropospheric aerosol at 532 and 1 064 nm wavelength and their spatial and temporal variations, and to research aerosol size distribution with altitude. This lidar adopted four channels to receive the far and near range backscattering signal at 532 and 1 064 nm wavelength respectively. In order to enhance the capability of daytime measurement, the system employed a narrow band interference filter to separate the main backscattering signal of lidar return, including Mie backscattering signal and Rayleigh backscattering signal from the total backscattering signal including non-elastic scattering signal and solar spectrum, by cooperating with an iris to depress the majority of sky background noise. Overall structure and specifications of the lidar, as well as data processing method, were described. The lidar system has been operated in Hefei (117. 16 degrees E, 31.90 degrees N). The profile of extinction coefficient of tropospheric aerosol and its temporal-spatial distribution were obtained. Angstrom exponent and optical depth of aerosol were also discussed. The observational results have shown that this lidar works well both during the day and at night and has the ability to measure the tropospheric aerosols and to manifest the temporal and spatial distributions of the aerosols with high precision.

  16. Wavelength selection of fingering instability inside Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Kurowski, Pascal; Limat, Laurent; Petitjeans, Philippe; Fernandez, Juan

    2001-11-01

    Fingering instabilities between fluids confined between two plates sometimes involve a typical wavelength λ proportional to the gap h. This unexplained behavior is investigated in the case of the Rayleigh-Taylor instability between two liquids of same viscosity. Using linear stability analysis based on a simplified model of hydrodynamics (Darcy-Stokes equation), we show in particular that, in the miscible case, the wavelength λ of the instability normalized by the gap b of the cell and the dimensionless growth rate Σ remain constant when the Péclet number Pe = fracb^3 Δρ12η D is large ( η viscosity, g gravitational acceleration, D diffusivity, Δρ density difference). The same result holds in the immiscible case for large capillary number C_a=fracb^2Δρ12γ (γ surface tension). In this saturation regime, the dominant wavelength is given by λ=2.3b, while in the opposite limit (low Pe or low C_a) λ scales respectively as fracbPe or fracbC_a^1/2. These theoretical solutions are then compared to experimental measurements for a wide range of Peclet numbers (more than 4 orders of magnitude) : a very good agreement is observed in particular for viscous fluids.

  17. Raman Shifting a Tunable ArF Excimer Laser to Wavelengths of 190 to 240 nm With a Forced Convection Raman Cell

    NASA Technical Reports Server (NTRS)

    Balla, R. Jeffrey; Herring, G. C.

    2000-01-01

    Tunable radiation, at ultraviolet wavelengths, is produced by Raman shifting a modified 285-mJ ArF excimer laser. Multiple Stokes outputs are observed in H2, CH4, D2, N2, SF6, and CF4 (20, 22, 53, 21, 2.1, and 0.35 percent, respectively). Numbers in parentheses are the first Stokes energy conversion efficiencies. We can access 70 percent of the frequency range 42000-52000 cm (exp -1) (190-240 nm) with Stokes energies that vary from 0.2 microJoule to 58 mJ inside the Raman cell. By using 110 mJ of pump energy and D 2 , the tunable first Stokes energy varies over the 29-58 mJ range as the wavelength is tuned over the 204-206 nm range. Dependence on input energy, gas pressure, He mixture fraction, and circulation of the gas in the forced convection Raman cell is discussed; Stokes conversion is also discussed for laser repetition rates from 1 to 100 Hz. An empirical equation is given to determine whether forced convection can improve outputs for a given repetition rate.

  18. On the wavelength of self-organized shoreline sand waves

    NASA Astrophysics Data System (ADS)

    Falqués, A.; van den Berg, N.; Ribas, F.; Caballeria, M.; Calvete, D.

    2012-04-01

    Shoreline sand waves are undulations of the shoreline that extend into the bathymetry up to a certain depth. Here we will focus on self-organized sand waves that form due to shoreline instability in case of very oblique wave incidence (Ashton et al., 2001). The model of Ashton and co-authors did not predict any wavelength selection for the emerging sand waves whereas Falqués and Calvete (2005) predicted a wavelength selection in the range 4-15 km. This difference is attributable to that Falqués and Calvete (2005) computed wave refraction and shoaling over the actual curvilinear depth contours while Ashton et al. (2001) assumed locally rectilinear and parallel contours. Although there exist shoreline features at a larger scale (Ashton et al. 2001; Falqués et al. 2011) sand waves at a few km scale are more common (Ruessink and Jeuken, 2002; Davidson-Arnott and van Heyningen, 2003; Falqués et al., 2011; Medellin et al., 2008) . While their characteristic wavelength is a robust model output (Falqués and Calvete, 2005; Uguccioni et al., 2006; van den Berg et al., 2011) the physical reasons for the existence of a wavelength selection are still unknown. Furthermore, the parameter dependence of the dominant wavelength, Lm, is largely unexplored. In particular, the disparity between the large length scale of sand waves and the relevant length scales of the problem: width of the surf zone, water wave wavelength, etc. is intriguing. The aim of the present contribution is to gain insight into those physical reasons and the dependence of Lm on beach profile and water wave properties. The essence of sandwave behaviour can be captured with the simple one-line shoreline modelling concept by looking at the alongshore position of the maximum in total transport rate Q, which is here investigated with both the linearized model of Falqués and Calvete (2005) and the nonlinear model of van den Berg et al. (2011) . It is found that the position of that maximum is largely controlled

  19. Variable wavelength selection devices: Physics and applications

    NASA Astrophysics Data System (ADS)

    Xianyu, Haiqing

    Variable wavelength selection (VWS) achieved by implementing tunability to wavelength discriminating devices has generated great interest in basic science, applied physics, and technology. This thesis focuses on the underlying physics and application of several novel wavelength discriminating devices. Holographical polymer dispersed liquid crystals (HPDLCs) are switchable volume gratings formed by exposing a photopolymerizable monomer and liquid crystal mixture to interfering monochromatic light beams. An HPDLCs wavelength discriminating ability along with its switchability, allow it to be utilized in VWS devices. A novel mode HPDLC, total internal reflection (TIR) HPDLC, has been developed as a wavelength selective filter. The grating planes in this device are tilted so that the diffracted light experiences total internal reflection at the glass-air interface and is trapped in the cell until it eventually escapes from an edge. A VWS device is demonstrated by stacking TIR HPDLCs operating at different wavelengths. Converging or diverging recording beams are employed to fabricate chirped reflection HPDLCs with a pitch gradient along the designated direction, creating chirped switchable reflection gratings (CSRGs). A pixelated version of the CSRG is developed herein, and a dynamic spectral equalizer is presented by combining the pixelated CSRG with a prism (for wavelength discrimination). A switchable circular to point converter (SCPC), which enables the random selection of the wavelength bands divided by the Fabry-Perot interferometer utilizing the controllable beam steering capability of transmission HPDLCs, is demonstrated. A random optical cross-switch (TIROL) can be created by integrating a Fabry-Perot interferometer with a stack of SCPC units. The in-plane electric field generated by the interdigitated electrodes is utilized to elongate the helical pitch of a cholesteric liquid crystal and thereby induces a red shift of the transmission reflection peak

  20. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    Schlueter, R.

    1994-08-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  1. Effects of Laser Wavelength on Ablator Testing

    NASA Technical Reports Server (NTRS)

    White, Susan M.

    2014-01-01

    Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

  2. Miniature integrated-optical wavelength analyzer chip

    NASA Astrophysics Data System (ADS)

    Kunz, R. E.; Dübendorfer, J.

    1995-11-01

    A novel integrated-optical chip suitable for realizing compact miniature wavelength analyzers with high linear dispersion is presented. The chip performs the complete task of converting the spectrum of an input beam into a corresponding spatial irradiance distribution without the need for an imaging function. We demonstrate the feasibility of this approach experimentally by monitoring the changes in the mode spectrum of a laser diode on varying its case temperature. Comparing the results with simultaneous measurements by a commercial spectrometer yielded a rms wavelength deviation of 0.01 nm.

  3. Modulation compression for short wavelength harmonic generation

    SciTech Connect

    Qiang, J.

    2010-01-11

    Laser modulator is used to seed free electron lasers. In this paper, we propose a scheme to compress the initial laser modulation in the longitudinal phase space by using two opposite sign bunch compressors and two opposite sign energy chirpers. This scheme could potentially reduce the initial modulation wavelength by a factor of C and increase the energy modulation amplitude by a factor of C, where C is the compression factor of the first bunch compressor. Such a compressed energy modulation can be directly used to generate short wavelength current modulation with a large bunching factor.

  4. An economic Fabry-Perot wavelength reference

    NASA Astrophysics Data System (ADS)

    Fżrész, Gábor; Glenday, Alex; Latham, Christian

    2014-07-01

    Precision radial velocity (PRV) measurements are key in studying exoplanets, and so are wavelength calibrators in PRV instruments. ThAr lamps offer an affordable but somewhat limited solution for the visible passband. Laser frequency combs are ideal calibrators, except the (still) narrow wavelength coverage and large price tag. White light Fabry-Perot (FP) calibrators offer frequency-comb like properties in a more affordable and less complicated package1. Using a commercial solid FP etalon and off-the shelf components we have constructed an economic FP calibrator suitable for observatories on a smaller budget.

  5. A Novel Portable Multi-Wavelength Laser System

    NASA Astrophysics Data System (ADS)

    Charlton, Andy; Dickinson, B.

    There is an established need for a portable and affordable Q-switched laser system for use in studio conservation and small scale field use. The ideal system would be capable of producing a variety of wavelengths ranging from the ultraviolet to the infrared with sufficient energy per pulse to treat a wide range of materials including stone, marble, terracotta, wood, organic materials, bone, parchment, textiles, and metals. In this paper we report on such a system which is capable of delivering Q-switched output at 1,064nm in excess of 300mJ per pulse and at repetition rates of up to 25 Hz. Additional outputs are also reported at 266 nm, 355 nm, 532 nm, and 2.94 μm. Preliminary cleaning results on a small range of objects using the Q-switched 1,064nm output are presented.

  6. Volcano monitoring by short wavelength infrared satellite remote sensing

    NASA Technical Reports Server (NTRS)

    Rothery, D. A.; Francis, P. W.; Wood, C. A.

    1988-01-01

    The use of short wavelength IR Landsat TM data for volcano monitoring is examined. By determining the pixel-integrated from the TM data, it is possible to estimate the temperature and size of hot areas which occupy less than one complete pixel. Examples of volcano monitoring with remote sensing data are discussed. It is suggested that the entire volcanic temperature range (100-1200 C) could be accomplished by decreasing the band 6 gain by just one order of magnitude so that it was sensitive to radiance from 1 to 100 mW/sq cm/sr/micron.

  7. Penetration depth at green wavelengths in turbid waters

    NASA Technical Reports Server (NTRS)

    Whitlock, C. H.; Witte, W. G.; Usry, J. W.; Gurganus, E. A.

    1978-01-01

    A laboratory and field measurement program was conducted to determine apparent remote sensing penetration depths at a wavelength of 520 nm. Tests were made for various types of sediments under controlled conditions in a laboratory. Field tests were conducted in several different water bodies over a wide range of solar elevation angles. Laboratory results indicate that apparent penetration depth is significantly influenced by mineral content and/or size of suspended sediments. Field measurements show wide variation in apparent penetration depth, even when suspended solids concentration is nearly constant. Apparent penetration depth does not appear to be a strong function of solar elevation angle so long as the water mixture remains constant.

  8. Multi-Wavelength Observations of Nearby Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Janice

    2015-08-01

    Do cycles of violent, intense, but short-lived bursts constitute a significant mode of global star formation in present-day galaxies? Such events can have a profound effect on galaxies, particularly those with shallow potential wells, and observational measures of their prevalence inform our understanding of a wide range of issues in galaxy evolution. I will highlight what we have learned about starbursts from multi-wavelength observations of galaxies in the local volume on both galactic and smaller scales, and explore how connections with the study of the deaths of massive stars may further our understanding of open issues in galaxy evolution.

  9. Resonant tunneling diodes as sources for millimeter and submillimeter wavelengths

    NASA Technical Reports Server (NTRS)

    Vanbesien, O.; Bouregba, R.; Mounaix, P.; Lippens, D.; Palmateer, L.; Pernot, J. C.; Beaudin, G.; Encrenaz, P.; Bockenhoff, E.; Nagle, J.

    1992-01-01

    High-quality Resonant Tunneling Diodes have been fabricated and tested as sources for millimeter and submillimeter wavelengths. The devices have shown excellent I-V characteristics with peak-to-valley current ratios as high as 6:1 and current densities in the range of 50-150 kA/cm(exp 2) at 300 K. Used as local oscillators, the diodes are capable of state of the art output power delivered by AlGaAs-based tunneling devices. As harmonic multipliers, a frequency of 320 GHz has been achieved by quintupling the fundamental oscillation of a klystron source.

  10. Dual-wavelength erbium-doped fiber laser with tunable wavelength spacing using a twin core fiber-based filter

    NASA Astrophysics Data System (ADS)

    Yin, Guolu; Lou, Shuqin; Wang, Xin; Han, Bolin

    2014-05-01

    A dual-wavelength erbium-doped fiber laser with tunable wavelength spacing was proposed and experimentally demonstrated by using a twin core fiber (TCF)-based filter. Benefiting from the polarization dependence of the TCF-based filter, the laser operated in dual-wavelength oscillation with two orthogonal polarization states. By adjusting the polarization controller, the wavelength spacing was tuned from 0.1 nm to 1.2 nm without shifting the centre position of the two wavelengths. By stretching the TCF, the two wavelengths were simultaneously tuned with fixed wavelength spacing. Such a dual-wavelength fiber laser could find applications in optical fiber sensors and microwave photonics generation.

  11. Discrete wavelength-locked external cavity laser

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  12. Superiority of half-wavelength helicon antennae

    NASA Astrophysics Data System (ADS)

    Porte, L.; Yun, S. M.; Arnush, D.; Chen, F. F.

    2003-05-01

    Plasma densities produced by half- and full-wavelength (HW and FW) helical antennae in helicon discharges are compared. It is found that HW antennae are more efficient than FW ones in producing plasma downstream from the antenna. The measured wave amplitudes and the apparent importance of downstream ionization do not agree with computations.

  13. Resolving the Moth at Millimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Ricarte, Angelo; Moldvai, Noel; Hughes, A. Meredith; Duchêne, Gaspard; Williams, Jonathan P.; Andrews, Sean M.; Wilner, David J.

    2013-09-01

    HD 61005, also known as "The Moth," is one of only a handful of debris disks that exhibit swept-back "wings" thought to be caused by interaction with the ambient interstellar medium (ISM). We present 1.3 mm Submillimeter Array observations of the debris disk around HD 61005 at a spatial resolution of 1.''9 that resolve the emission from large grains for the first time. The disk exhibits a double-peaked morphology at millimeter wavelengths, consistent with an optically thin ring viewed close to edge-on. To investigate the disk structure and the properties of the dust grains we simultaneously model the spatially resolved 1.3 mm visibilities and the unresolved spectral energy distribution (SED). The temperatures indicated by the SED are consistent with expected temperatures for grains close to the blowout size located at radii commensurate with the millimeter and scattered light data. We also perform a visibility-domain analysis of the spatial distribution of millimeter-wavelength flux, incorporating constraints on the disk geometry from scattered light imaging, and find suggestive evidence of wavelength-dependent structure. The millimeter-wavelength emission apparently originates predominantly from the thin ring component rather than tracing the "wings" observed in scattered light. The implied segregation of large dust grains in the ring is consistent with an ISM-driven origin for the scattered light wings.

  14. RESOLVING THE MOTH AT MILLIMETER WAVELENGTHS

    SciTech Connect

    Ricarte, Angelo; Moldvai, Noel; Hughes, A. Meredith; Duchene, Gaspard; Williams, Jonathan P.; Andrews, Sean M.; Wilner, David J.

    2013-09-01

    HD 61005, also known as ''The Moth'', is one of only a handful of debris disks that exhibit swept-back ''wings'' thought to be caused by interaction with the ambient interstellar medium (ISM). We present 1.3 mm Submillimeter Array observations of the debris disk around HD 61005 at a spatial resolution of 1.''9 that resolve the emission from large grains for the first time. The disk exhibits a double-peaked morphology at millimeter wavelengths, consistent with an optically thin ring viewed close to edge-on. To investigate the disk structure and the properties of the dust grains we simultaneously model the spatially resolved 1.3 mm visibilities and the unresolved spectral energy distribution (SED). The temperatures indicated by the SED are consistent with expected temperatures for grains close to the blowout size located at radii commensurate with the millimeter and scattered light data. We also perform a visibility-domain analysis of the spatial distribution of millimeter-wavelength flux, incorporating constraints on the disk geometry from scattered light imaging, and find suggestive evidence of wavelength-dependent structure. The millimeter-wavelength emission apparently originates predominantly from the thin ring component rather than tracing the ''wings'' observed in scattered light. The implied segregation of large dust grains in the ring is consistent with an ISM-driven origin for the scattered light wings.

  15. Laser wavelength comparison by high resolution interferometry.

    PubMed

    Layer, H P; Deslattes, R D; Schweitzer, W G

    1976-03-01

    High resolution interferometry has been used to determine the wavelength ratio between two molecularly stabilized He-Ne lasers, one locked to a methane absorption at 3.39 microm and the other locked to the k peak of (129)I(2) at 633 nm. An optical beat frequency technique gave fractional orders while a microwave sideband method yielded the integer parts. Conventional (third derivative) peak seeking servoes stabilized both laser and cavity lengths. Reproducibility of the electronic control system and optics was a few parts in 10(12), while systematic errors associated with curvature of the cavity mirrors limited the accuracy of the wavelength ratio measurement to 2 parts in 10(10). The measured wavelength ratio of the methane stabilized He-Ne laser at 3.39 microm [P(7) line, nu(3) band] to the (129)I(2) (k peak) stabilized He-Ne laser at 633 nm was 5.359 049 260 6 (0.000 2 ppm). This ratio agrees with that calculated from the (lower accuracy) results of earlier wavelength measurements made relative to the (86)Kr standard. Its higher accuracy thus permits a provisional extension of the frequency scale based on the cesium oscillator into the visible spectrum.

  16. The wavelength dependence of Triton's light curve

    NASA Technical Reports Server (NTRS)

    Hillier, J.; Veverka, J.; Helfenstein, P.; Mcewen, A.

    1991-01-01

    Using Voyager observations, it is demonstrated that Triton's orbital light curve is strongly wavelength-dependent, a characteristic which readily explains some of the apparent discrepancies among pre-Voyager telescopic measurements. Specifically, a light curve amplitude (peak to peak) is found that decreases systematically with increasing wavelength from about 0.08 magnitude (peak to peak) near 200 nm to less than 0.02 magnitude near 1000 nm. Peak brightness occurs near 90 deg orbital longitude (leading hemisphere). The brightness variation across this hemisphere is close to sinusoidal; the variation across the darker hemisphere is more complex. The decrease in light curve amplitude with increasing wavelength appears to be due to a decrease in contrast among surface markings, rather than to atmospheric obscuration. The model also explains the observed decrease in the amplitude of Triton's light curve at visible wavelengths over the past decade, a decrease related to the current migration of the subsolar latitude toward the south pole; it is predicted that this trend will continue into the 1990s.

  17. Two-wavelength spatial-heterodyne holography

    DOEpatents

    Hanson, Gregory R.; Bingham, Philip R.; Simpson, John T.; Karnowski, Thomas P.; Voelkl, Edgar

    2007-12-25

    Systems and methods are described for obtaining two-wavelength differential-phase holograms. A method includes determining a difference between a filtered analyzed recorded first spatially heterodyne hologram phase and a filtered analyzed recorded second spatially-heterodyned hologram phase.

  18. Devices for wavelength switching in optical networks

    SciTech Connect

    d`Alessandro, A.; Baran, J.E.; Smith, D.A.

    1994-12-31

    Wavelength routing crossconnects are considered the core of WDM optical networks. They consist of optical switches independently rearrangeable for each wavelength channel and for any input-output configuration so that any path can be chosen almost arbitrarily by the network users. In general the implementation of the wavelength routing function requires complex switch arrays. Very simple wavelength-selection crossconnects can be realized by using acousto-optic switches (AOS), because of their unique ability of processing several optical signals simultaneously and their low driving power consumption, less than 10 mW/channel. AOS`s can be considered a particular evolution of acousto-optical tunable filters, whose integrated optic version on lithium niobate has been developed in several research institutions around the world in the past decade. This paper reviews the last accomplishments of AOS`s, whose specifications are directly tied with optical network requirements, the foremost challenge being a strong suppression of crosstalk. Dilated AOS`s can reduce interport crosstalk to below {minus}30 dB and apodization of acousto-optic interaction can reduce interchannel crosstalk to below {minus}15 dB during multiwavelength operation.

  19. Electricity and short wavelength radiation generator

    DOEpatents

    George, E.V.

    1985-08-26

    Methods and associated apparati for use of collisions of high energy atoms and ions of He, Ne, or Ar with themselves or with high energy neutrons to produce short wavelength radiation (lambda approx. = 840-1300 A) that may be utilized to produce cathode-anode currents or photovoltaic currents.

  20. Self Calibration of a 2-wavelength Pyrometer

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1998-01-01

    Pyrometers require calibrations to determine their instrument constants before they can be used in remote temperature measurements. These constants reflect the combined effects of detector response, the transmissivities of intervening optical media (windows and gases) and the emissivity of the measured surface. We describe here the principal and the demonstration of self calibrating 2-wavelength pyrometer.

  1. United States Access Board

    MedlinePlus

    ... Communications & IT Access to information and communication technology (ICT) is addressed by Board standards and guidelines issued ... Engineer (November 3) Access Board Approves Rules on ICT Refresh and Medical Diagnostic Equipment (September 14) Access ...

  2. Multi-mode fiber coarse WDM grating router using broadband add/drop filters for wavelength re-use

    SciTech Connect

    Patel, R R; Bond, S W; Larson, M C; Pocha, M D; Lowry, M E; Deri, R J

    1999-06-01

    We demonstrate a grating-router with 37nm channel spacing and 6nm FWHM in the 800-900nm range for WDM over multimode fiber. Broadband thin-film add/drop filters provide wavelength re-use enabling NxN fully non-blocking interconnection with N wavelengths.

  3. Variations in the short wavelength cut-off of the solar UV spectra.

    PubMed

    Parisi, A V; Turner, J

    2006-03-01

    Cloud and solar zenith angle (SZA) are two major factors that influence the magnitude of the biologically damaging UV (UVBD) irradiances for humans. However, the effect on the short wavelength cut-off due to SZA and due to clouds has not been investigated for biologically damaging UV for cataracts. This research aims to investigate the influence of cloud and SZA on the short wavelength cut-off of the spectral UVBD for cataracts. The spectral biologically damaging UV for cataracts on a horizontal plane was calculated by weighting the spectral UV measured with a spectroradiometer with the action spectrum for the induction of cataracts in a porcine lens. The UV spectra were obtained on an unshaded plane at a latitude of 29.5 degrees S. The cut-off wavelength (lambdac) was defined as the wavelength at which the biologically damaging spectral irradiance was 0.1% of the maximum biologically damaging irradiance for that scan. For the all sky conditions, the short wavelength cut-off ranged by 12 nm for the SZA range of 5 to 80 degrees and the maximum in the spectral UVBD ranged by 15 nm. Similarly, for the cloud free cases, the short wavelength cut-off ranged by 9 nm for the same SZA range. Although, cloud has a large influence on the magnitude of the biologically damaging UV for cataracts, the influence of cloud on the short wavelength cut-off for the biologically damaging UV for cataracts is less than the influence of the solar zenith angle.

  4. Effect of laser-pulse structure and wavelength on wound healing

    NASA Astrophysics Data System (ADS)

    Fortune, D. S.; Huang, Shan; Bryant, G. L.; Garrett, C. Gaelyn; Reinisch, Lou

    1998-07-01

    We have investigated wound healing of incisions in the buccal mucosa of a canine model created with the Vanderbilt Free Electron Laser tuned to 6.1, 6.45 and 6.8 microns. We have also used a carbon dioxide laser, continuous wave and with a short-pulse structure (100 microseconds) to access wavelength and pulse structure components to wound healing from laser incisions. The tissue was evaluated histologically and with tensiometry acutely and at post operative days 3, 7, and 14. The data indicate that shorter laser pulse durations create less lateral thermal injury and wounds with greater tensile strength, resulting in earlier wound healing. Wound healing was only slightly dependent upon the wavelength of the laser. These results demonstrate that surgical carbon dioxide lasers with a short-pulse structure of approximately 100 microseconds or less could offer more prompt wound healing while maintaining the advantages of a 10.6 micron wavelength laser.

  5. Dielectric properties of doped titanates of transition metals in the millimeter-wavelength range

    NASA Astrophysics Data System (ADS)

    Rinkevich, A. B.; Perov, D. V.; Kuznetsov, E. A.; Pakhomov, Ya. A.; Ryabkov, Yu. I.

    2016-06-01

    Dielectric properties of ceramic titanates of nickel, cobalt, and manganese and their isomorphically substituted solid solutions are studied. Iron and magnesium are used as dopants. Original methods for solid-state synthesis of titanates allow variations in the dispersity of products. The structure and phase composition of products are analyzed. Microwave measurements of permittivity are performed in a frequency interval of 12-38 GHz. Real and imaginary parts of the permittivities of titanates are determined.

  6. Investigation of the lithium 670.7 nm wavelength range in the solar spectrum

    NASA Astrophysics Data System (ADS)

    Caffau, Elisabetta; Mott, Alessandro; Harutyunyan, Gohar; Malherbe, Jean-Marie; Steffen, Matthias

    2016-07-01

    Lithium is a key chemical element, with a chemical evolution that is different from that of most other elements. It is also very fragile, as it is destroyed by nuclear reactions with protons at temperatures higher than about 2.5 million K. According to standard Big Bang nucleosynthesis, only the isotope 7Li is produced in significant amounts, while the primordial abundance of the lighter isotope 6Li is negligible. Lithium is not produced by nucleosynthesis in normal stars, except in peculiar phases of stellar evolution (e.g. in AGB stars and Novae). Lithium may also be formed as a result of flares in the atmospheres of young, active stars. To investigate the history of Li production and depletion in the Galaxy, it is necessary to analyse stars of all ages, including those at solar metallicity. In this case, the spectroscopic determination of the Li abundance is complicated by the presence of other spectral lines overlapping with the Li doublet at 670.7 nm. The correct identification and knowledge of the atomic parameters of these blend lines is critical, especially if the 6LI/7Li isotopic ratio is to be derived. In this investigation, we consider several line lists of the blending components available in the literature and use them to compute synthetic spectra, performing the line formation computations both for the classical 1D Holweger-Mueller model and a CO5BOLD 3D hydrodynamical simulation of the solar atmosphere. The synthetic spectra are then compared to the solar spectrum observed at different limb angles. This allows us to check the quality of existing line lists, to find potentially misidentified blend lines, and to construct an optimized line list for solar-type stars.

  7. Studies of Saturn's Main Rings at Multiple Wavelengths

    NASA Astrophysics Data System (ADS)

    Spilker, L. J.; Deau, E.; Filacchione, G.; Morishima, R.; Hedman, M. M.; Nicholson, P. D.; Colwell, J. E.; Bradley, E. T.; Showalter, M.; Pilorz, S.; Brooks, S. M.

    2015-12-01

    A wealth of information about the characteristics of Saturn's ring particles and their regolith can be obtained by modeling the changes in their brightness, color and temperature with changing viewing geometry over a wide range of wavelengths, from ultraviolet through the thermal infrared. Data from Cassini's Composite Infrared Spectrometer (CIRS), Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS) and Ultraviolet Imaging Spectrograph (UVIS) are jointly studied using data from the lit and unlit main rings at multiple geometries and solar elevations over 11 years of the Cassini mission. Using multi-wavelength data sets allow us to test different thermal models by combining the effects of particle albedo, regolith grain size and surface roughness with thermal emissivity and inertia, particle spin rate and spin axis orientation. The CIRS temperature and ISS color variations are confined primarily to phase angle over a range of solar elevations with only small differences from changing spacecraft elevation. Color and temperature dependence with varying solar elevation angle are also observed. Brightness dependence with changing solar elevation angle and phase angle is observed with UVIS. VIMS observations show that the IR ice absorption band depths are a very weak function of phase angle, out to ~140 deg phase, suggesting that interparticle light scattering is relatively unimportant except at very high phase angles. These results imply that the individual properties of the ring particles may play a larger role than the collective properties of the rings, in particular at visible wavelengths. The temperature and color variation with phase angle may be a result of scattering within the regolith and on possibly rough surfaces of the clumps, as well as a contribution from scattering between individual particles in a many-particle-thick layer. Preliminary results from our joint studies will be presented. This research was carried out in part at

  8. Tunable dual-wavelength fiber laser with ultra-narrow linewidth based on Rayleigh backscattering.

    PubMed

    Zhu, Tao; Zhang, Baomei; Shi, Leilei; Huang, Shihong; Deng, Ming; Liu, Jianguo; Li, Xiong

    2016-01-25

    Dual-wavelength fiber lasers with ultra-narrow linewidth find wide applications in high-speed optical communications, fiber optic sensors, high resolution measurements and medical instruments and microwave or terahertz generation systems. Based on the linewidth compression mechanism due to Rayleigh backscattering, this paper adopts a simple ring structure cooperated with two fiber Bragg gratings centered at 1550 nm and 1530 nm respectively, achieving a dual-wavelength fiber laser with ultra-narrow linewidth, with a 3dB linewidth of ~700 Hz for each wavelength, and the SNR of 60dB. Tuning the center wavelength of one of the two FBGs while the other one keeps unchanged, the fiber laser keeps stable dual-wavelength lasing and the linewidth is still ~700 Hz. It can be seen that the compression for the linewidth based on the Rayleigh backscattering can be used in multi-wavelength laser systems, and because of the characteristic of the Rayleigh backscattering, the method has great potential in the application of wide wavelength range linewidth compression from the ultraviolet to the far infrared. PMID:26832513

  9. Detection Wavelength Control of Uncooled Infrared Sensors Using Two-Dimensional Lattice Plasmonic Absorbers †

    PubMed Central

    Takagawa, Yousuke; Ogawa, Shinpei; Kimata, Masafumi

    2015-01-01

    Wavelength-selective uncooled infrared (IR) sensors are highly promising for a wide range of applications, such as fire detection, gas analysis and biomedical analysis. We have recently developed wavelength-selective uncooled IR sensors using square lattice two-dimensional plasmonic absorbers (2-D PLAs). The PLAs consist of a periodic 2-D lattice of Au-based dimples, which allow photons to be manipulated using surface plasmon modes. In the present study, a detailed investigation into control of the detection wavelength was conducted by varying the PLA lattice structure. A comparison was made between wavelength-selective uncooled IR sensors with triangular and square PLA lattices that were fabricated using complementary metal oxide semiconductor and micromachining techniques. Selective enhancement of the responsivity could be achieved, and the detection wavelength for the triangular lattice was shorter than that for the square lattice. The results indicate that the detection wavelength is determined by the reciprocal-lattice vector for the PLAs. The ability to control the detection wavelength in this manner enables the application of such PLAs to many types of thermal IR sensors. The results obtained here represent an important step towards multi-color imaging in the IR region. PMID:26067198

  10. Theoretical investigation of all-metal-based mushroom plasmonic metamaterial absorbers at infrared wavelengths

    NASA Astrophysics Data System (ADS)

    Ogawa, Shinpei; Fujisawa, Daisuke; Kimata, Masafumi

    2015-12-01

    High-performance wavelength-selective infrared (IR) sensors require small pixel structures, a low-thermal mass, and operation in the middle-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) regions for multicolor IR imaging. All-metal-based mushroom plasmonic metamaterial absorbers (MPMAs) were investigated theoretically and were designed to enhance the performance of wavelength-selective uncooled IR sensors. All components of the MPMAs are based on thin layers of metals such as Au without oxide insulators for increased absorption. The absorption properties of the MPMAs were investigated by rigorous coupled-wave analysis. Strong wavelength-selective absorption is realized over a wide range of MWIR and LWIR wavelengths by the plasmonic resonance of the micropatch and the narrow-gap resonance, without disturbance from the intrinsic absorption of oxide insulators. The absorption wavelength is defined mainly by the micropatch size and is longer than its period. The metal post width has less impact on the absorption properties and can maintain single-mode operation. Through-holes can be formed on the plate area to reduce the thermal mass. A small pixel size with reduced thermal mass and wideband single-mode operation can be realized using all-metal-based MPMAs.

  11. Detection Wavelength Control of Uncooled Infrared Sensors Using Two-Dimensional Lattice Plasmonic Absorbers.

    PubMed

    Takagawa, Yousuke; Ogawa, Shinpei; Kimata, Masafumi

    2015-06-10

    Wavelength-selective uncooled infrared (IR) sensors are highly promising for a wide range of applications, such as fire detection, gas analysis and biomedical analysis. We have recently developed wavelength-selective uncooled IR sensors using square lattice two-dimensional plasmonic absorbers (2-D PLAs). The PLAs consist of a periodic 2-D lattice of Au-based dimples, which allow photons to be manipulated using surface plasmon modes. In the present study, a detailed investigation into control of the detection wavelength was conducted by varying the PLA lattice structure. A comparison was made between wavelength-selective uncooled IR sensors with triangular and square PLA lattices that were fabricated using complementary metal oxide semiconductor and micromachining techniques. Selective enhancement of the responsivity could be achieved, and the detection wavelength for the triangular lattice was shorter than that for the square lattice. The results indicate that the detection wavelength is determined by the reciprocal-lattice vector for the PLAs. The ability to control the detection wavelength in this manner enables the application of such PLAs to many types of thermal IR sensors. The results obtained here represent an important step towards multi-color imaging in the IR region.

  12. Shared Access Optical Networks For The Local Loop

    NASA Astrophysics Data System (ADS)

    Payne, D. B.; Stern, J. R.

    1988-09-01

    The application of single mode fibre to the local network environment opens up major opportunities for service provision via shared access networks. Previous technologies (copper pair, coaxial cable and multimode fibre) had bandwidth limitation problems that placed a severe restriction on both the level of resource sharing and the service package that could be delivered. The enormous bandwidth capability of single mode fibre can be used to provide significant resource sharing without incurring fundamental restrictions on the capacity of the services carried. The paper briefly outlines some of the activities within British Telecom on shared access systems. Early systems concepts were either based on fibre feeders to remote multiplexers for the delivery of telephony and data services to large customers or the use of advanced wavelength multiplexing techniques over passive optical networks for the transmission of wideband services to business and residential customers. Recently activity has concentrated on a passive optical network that shows good potential for the economic provision of telephony services. The structure of the network allows the later addition of broadband services via additional wavelengths without disturbing existing telephony/data customers. The basic network has a fibre feeder from the exchange to passive optical splitters housed at the Cabinet and Distribution Points (DP). Each customer receives a fibre from DP and via this a TDM multiplex broadcast from the exchange which carries the customer's traffic. The customer equipment accesses the time slots destined for the customer and delivers the data via a suitable interface to provide the services required. Customers transmit back to the exchange in a time multiplex synchronised by a ranging protocol that sets an appropriate delay in the customer equipment to avoid collisions at the optical combiners in the DPs and Cabinet. Present studies are considering a total optical split of 128 ways with a

  13. Constraining the wavelength dependence of polarization for various asteroid taxonomies

    NASA Astrophysics Data System (ADS)

    Maleszewski, Chester; Smith, Paul S.; McMillan, Robert S.

    2016-10-01

    The polarization of sunlight reflected from asteroids is known to be inversely proportional to geometric albedo (Umov 1905). However, that was mainly derived from observations in the V-filter. Preliminary observations of the wavelength dependence were conducted by Belskaya et al. (2009) in the major asteroid taxonomic classes. The limited UBVRI data revealed trends of spectral slope vs. phase angle. To study the wavelength dependence of asteroid polarization more robustly, we have used the SPOL spectropolarimeter at the 2.3-m Bok and 1.6-m Kuiper telescopes. The finer spectral resolution of spectropolarimetry is needed to confirm the linearity of the wavelength dependence of polarization.We present polarization spectra from four asteroid taxonomic groups: B-, C-, S-, and X-types. Across the observed wavelength range (0.45 to 0.7 microns), the linear trend described by Belskaya et al. is confirmed and we determined the best-fit linear slope of each spectrum. For the S-type asteroids, the slope of the polarization spectra becomes more negative as the phase angle increases. The rate at which the polarization slope changes increases at phase angles greater than the inversion angle. C-type asteroids behave differently from the S-types in two ways. First, the polarization spectra for the C-types are positively sloped as opposed to negative (also noted in Belskaya et al.). Also, as you observe the C-types closer to the inversion angle (~20 degrees phase angle), the polarization slopes tend to flatten as opposed to steepen. The polarization spectra of B-type asteroids are positively sloped, but the tendency to flatten near the inversion angle like the C-type spectra is not evident. Our observations of low albedo X-types exhibit positive polarization slopes, while the high albedo observations exhibit negative slopes. Differences in the wavelength dependencies of polarization between various asteroid types appear to be driven by differences in their geometric albedos. Better

  14. Choice of the proper wavelength for photochemotherapy

    NASA Astrophysics Data System (ADS)

    Moan, Johan; Iani, Vladimir; Ma, LiWei

    1996-01-01

    All photosensitizers applied in experimental- and clinical-photochemotherapy (PCT) have broad absorption spectra stretching from the ultraviolet up to 6 - 700 nm. Light of wavelengths in the red part of the spectrum is chosen for PCT even though the extinction coefficients of the sensitizers are usually smaller in this wavelength region than at shorter wavelengths. Thus, if one wants to treat superficial tumors or skin disorders, this may be a wrong choice. Two pieces of information are needed in order to make a proper choice of wavelength to treat a lesion of a given depth: the wavelength dependence of the optical penetration depth into tissue, and the action spectrum for tumor destruction. Additionally, the skin photosensitivity induced by the drug should be considered. We have non-invasively measured the optical penetration spectra of human tissues in vivo and the fluorescence excitation spectra for several sensitizers, including protoporphyrin (PpIX), in cells. Assuming that the action spectrum for cell inactivation can be approximated by the fluorescence excitation spectrum of the sensitizer -- which is indeed the case for a number of sensitizers in cells in vitro -- we have considered the situation for 5-aminolevulinic acid-induced PpIX in human tissue. All the way down to about 2 mm below the surface light in the Soret band (-410 nm) would give the largest cell inactivation, while at depth exceeding 2 mm, the conventional 635 nm light would be optimal. Light at the argon laser wavelength 514.5 nm is more efficient than light at 635 nm down to 1 mm. From the surface and down to 6 mm, the 635 nm peak of the excitation spectrum of PpIX, as evaluated per photon incident on the skin surface, is redshifted by less than 2 nm. In some cases photosensitizing photoproducts are formed during PCT, such as photoprotoporphyrin during PCT with PpIX. In such cases it may be advantageous to apply a broad-band light source with a spectrum that covers also part of the action

  15. Technology developments toward large format long wavelength bolometer arrays

    NASA Astrophysics Data System (ADS)

    Allen, Christine A.; Benford, Dominic J.; Miller, Timothy M.; Moseley, S. Harvey; Staguhn, Johannes G.; Wollack, Edward J.

    2007-09-01

    We are developing a kilopixel, filled bolometer array for infrared astronomy. The array consists of three individual components, to be merged into a single, working unit; 1) a transition edge sensor (TES) bolometer array, operating in the milliKelvin regime, 2) quarter-wave resonance backshorts, and 3) superconducting quantum interference device (SQUID) multiplexer readout. The detector array is a filled, square-grid of suspended, silicon membrane bolometers with superconducting thermistors. The spacing of the backshort beneath the detector grid can be set from ~30-300 microns by adjusting two process parameters during fabrication. We have produced prototype, monolithic arrays having 1 mm and 2 mm pitch detectors. The key technologies required for kilopixel arrays of detectors to be hybridized to SQUID multiplexer readout circuits have been demonstrated. Mechanical models of large-format detector grids have been indium bump-bonded to dummy multiplexer readouts to study electrical continuity. A monolithic array of 1 mm pitch detectors has been mated to a backshort grid optimized for a 350 micron resonant wavelength. Through-wafer microvias, for electroplated, low-resistance electrical connection of detector elements, have been prototyped using deep reactive ion etching. The ultimate goal of this work is to develop large-format (thousands of pixels) bolometer array architecture with background-limited sensitivity, suitable for a wide range of long wavelengths and a wide range of astronomical applications such as imaging, spectroscopy, and polarimetry and applicable for ground-based, suborbital, and space-based instruments.

  16. Silicon-carbide-based extreme environment temperature sensor using wavelength-tuned signal processing.

    PubMed

    Riza, Nabeel A; Sheikh, Mumtaz

    2008-05-15

    A wavelength-tuned signal-processing approach is proposed for enabling direct unambiguous temperature measurement in a free-space targeted single-crystal silicon carbide (SiC) temperature sensor. The approach simultaneously exploits the 6H SiC fundamental Sellmeier equation-based wavelength-sensitive refractive index change in combination with the classic temperature-dependent refractive index change and the material thermal-expansion path-length change to encode SiC chip temperature with wavelength. Presently, the technique is useful for fast coarse temperature measurement as demonstrated from room temperature to 1000 degrees C using a 10-peak count wavelength-tuned measurement with a 0.31 nm total wavelength change. This coarse technique can be combined with the previously presented two-wavelength signal-processing temperature measurement approach to simultaneously deliver a wide temperature range and a high-resolution temperature sensor. Applications for the sensor range from power plants to materials processing facilities.

  17. Feasibility Demonstration of a Massively Parallelizable Near-Field Sensor for Sub-Wavelength Defect Detection and Imaging

    NASA Astrophysics Data System (ADS)

    Mostafavi, Mahkamehossadat

    To detect and resolve sub-wavelength features at optical frequencies, beyond the diffraction limit, requires sensors that interact with the electromagnetic near-field of those features. Most instruments operating in this modality scan a single detector element across the surface under inspection because the scattered signals from a multiplicity of such elements would end up interfering with each other. However, an alternative massively parallelized configuration, consisting of a remotely interrogating array of dipoles, capable of interrogating multiple adjacent areas of the surface at the same time, was proposed in 2002. In the present work a remotely interrogating slot antenna inside a 60nm silver slab is designed which increases the signal to noise ratio of the original system. The antenna is tuned to resonance at 600nm range by taking advantage of the plasmon resonance properties of the metal's negative permittivity and judicious shaping of the slot element. Full-physics simulations show the capability of detecting an 8nm particle using red light illumination. The sensitivity to the lambda/78 particle is attained by detecting the change induced on the antenna's far field signature by the proximate particle, a change that is 15dB greater than the scattering signature of the particle by itself. To verify the capabilities of this technology in a readily accessible experimental environment, a radiofrequency scale model is designed using a meta-material to mimic the optical properties of silver in the 2GHz to 5GHz range. Various approaches to the replication of the metal's behavior are explored in a trade-off between fidelity to the metal's natural plasmon response, desired bandwidth of the demonstration, and ii manufacturability of the meta-material. The simulation and experimental results successfully verify the capability of the proposed near-field sensor in sub-wavelength detection and imaging not only as a proof of concept for optical frequencies but also as a

  18. Simple Line Access Protocol Version 1.0

    NASA Astrophysics Data System (ADS)

    Osuna, Pedro; Salgado, Jesus; Guainazzi, Matteo; Barbarisi, Isa; Dubernet, Marie-Lise; Tody, Doug; Osuna, Pedro; Salgado, Jesus

    2010-12-01

    The Simple Line Access Protocol (SLAP) is an IVOA Data Access protocol which defines a protocol for retrieving spectral lines coming from various Spectral Line Data Collections through a uniform interface within the VO framework. These lines can be either observed or theoretical and will be typically used to identify emission or absorption features in astronomical spectra. It makes use of the Simple Spectral Line Data Model (SSLDM [1]) to characterize spectral lines through the use of uTypes [14]. Physical quantities of units are described by using the standard Units DM [15]. SLAP services can be registered in an IVOA Registry of Resources using the VOResource [12] Extension standard, having a unique ResourceIdentifier [13] in the Registry. The SLAP interface is meant to be reasonably simple to implement by service providers. A basic query will be done in a wavelength range for the different services. The service returns a list of spectral lines formatted as a VOTable. Thus, an implementation of the service may support additional search parameters (some which may be custom to that particular service) to more finely control the selection of spectral lines. The specification also describes how the search on extra parameters has to be done, making use of the support provided by the Simple Spectral Line Data Model (SSLDM [1])

  19. Fiber-coupled diode laser modules with wavelengths around 2 μm

    NASA Astrophysics Data System (ADS)

    Haverkamp, Mark; Wieching, Kristin; Traub, Martin; Boucke, Konstantin

    2007-02-01

    The common wavelength regime for high-power diode laser modules is the range between 800 nm and 1000 nm. However, there are also many applications that demand for a wavelength of around 2 μm. This wavelength range is extremely interesting for applications such as the processing of plastics, medical applications as well as environmental analytics. The interest in lasers with this wavelength is based on the special absorption characteristics of different types of material: Numerous plastics possess an intrinsic absorption around 2 μm, so that the use of additives is no longer necessary. This is of great value especially for medical-technical products, where additives require a separate approval. Furthermore the longer wavelength allows the processing of plastics which are clear and transparent at the visible. In addition, water, which is an essential element of biologic soft tissue, absorbs radiation at the wavelength about 2 μm very efficiently. As radiation of this wavelength can be guided by glass fibers, this wavelength may be very helpful for laser surgery. Currently available lasers at the spectral range about 2 μm are solid-state lasers based on Ho- and Tmdoped crystals. These systems suffer from high purchase costs as well as size and weight. In contrast to this, diode lasers can be built more compact, are much cheaper and more efficient. For this background, GaSb based high-power laser diodes for the wavelength regime of 1.9 - 2.3 μm are developed at the Fraunhofer Institute for Solid State Physics (IAF). At the Fraunhofer Institute for Laser Technology (ILT), fiber-coupled laser diode modules based on these laser bars are designed and realized. A first module prototype uses two laser bars with a wavelength of 1.9 μm to provide an output power of approx. 15 W from a 600 μm, NA 0.22 fiber. The module setup as well as the characteristics of the laser bars at 1.9 μm wavelength are described in this paper.

  20. Wavelength interrogation of fiber Bragg grating sensors using tapered hollow Bragg waveguides.

    PubMed

    Potts, C; Allen, T W; Azar, A; Melnyk, A; Dennison, C R; DeCorby, R G

    2014-10-15

    We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10  pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1  mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated. PMID:25361125

  1. Wavelength interrogation of fiber Bragg grating sensors using tapered hollow Bragg waveguides.

    PubMed

    Potts, C; Allen, T W; Azar, A; Melnyk, A; Dennison, C R; DeCorby, R G

    2014-10-15

    We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10  pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1  mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated.

  2. Long-wavelength PTSI infrared detectors and method of fabrication thereof

    NASA Technical Reports Server (NTRS)

    Lin, True-Lon (Inventor); Park, Jin S. (Inventor); Gunapala, Sarath D. (Inventor); Jones, Eric W. (Inventor); Del Castillo, Hector M. (Inventor)

    1997-01-01

    Extended cutoff wavelengths of PtSi Schottky infrared detectors in the long wavelength infrared (LWIR) regime have been demonstrated for the first time. This result was achieved by incorporating a 1-nm-thick p+ doping spike at the PtSi/Si interface. The extended cutoff wavelengths resulted from the combined effects of an increased electric field near the silicide/Si interface due to the p+ doping spike and the Schottky image force. The p+ doping spikes were grown by molecular beam epitaxy at 450 degrees Celsius using elemental boron as the dopant source, with doping concentrations ranging from 1.times.10.sup.19 to 1.times.10.sup.21 cm.sup.-3. The cutoff wavelengths were shown to increase with increasing doping concentrations of the p+ spikes.

  3. Development and operation of a high-throughput accurate-wavelength lens-based spectrometer

    NASA Astrophysics Data System (ADS)

    Bell, Ronald E.

    2014-11-01

    A high-throughput spectrometer for the 400-820 nm wavelength range has been developed for charge exchange recombination spectroscopy or general spectroscopy. A large 2160 mm-1 grating is matched with fast f/1.8 200 mm lenses, which provide stigmatic imaging. A precision optical encoder measures the grating angle with an accuracy ≤0.075 arc sec. A high quantum efficiency low-etaloning CCD detector allows operation at longer wavelengths. A patch panel allows input fibers to interface with interchangeable fiber holders that attach to a kinematic mount at the entrance slit. Computer-controlled hardware allows automated control of wavelength, timing, f-number, automated data collection, and wavelength calibration.

  4. Narrow band wavelength selective filter using grating assisted single ring resonator

    SciTech Connect

    Prabhathan, P. Murukeshan, V. M.

    2014-09-15

    This paper illustrates a filter configuration which uses a single ring resonator of larger radius connected to a grating resonator at its drop port to achieve single wavelength selectivity and switching property with spectral features suitable for on-chip wavelength selection applications. The proposed configuration is expected to find applications in silicon photonics devices such as, on-chip external cavity lasers and multi analytic label-free biosensors. The grating resonator has been designed for a high Q-factor, high transmittivity, and minimum loss so that the wavelength selectivity of the device is improved. The proof-of-concept device has been demonstrated on a Silicon-on-Insulator (SOI) platform through electron beam lithography and Reactive Ion Etching (RIE) process. The transmission spectrum shows narrow band single wavelength selection and switching property with a high Free Spectral Range (FSR) ∼60 nm and side band rejection ratio >15 dB.

  5. Development and Operation of High-throughput Accurate-wavelength Lens-based Spectrometer

    SciTech Connect

    Bell, Ronald E

    2014-07-01

    A high-throughput spectrometer for the 400-820 nm wavelength range has been developed for charge exchange recombination spectroscopy or general spectroscopy. A large 2160 mm-1 grating is matched with fast f /1.8 200 mm lenses, which provide stigmatic imaging. A precision optical encoder measures the grating angle with an accuracy < 0.075 arc seconds. A high quantum efficiency low-etaloning CCD detector allows operation at longer wavelengths. A patch panel allows input fibers to interface with interchangeable fiber holders that attach to a kinematic mount behind the entrance slit. Computer-controlled hardware allows automated control of wavelength, timing, f-number, automated data collection, and wavelength calibration.

  6. Detection of foreign materials in cotton using a multi-wavelength imaging method

    NASA Astrophysics Data System (ADS)

    Jia, D. Y.; Ding, T. H.

    2005-06-01

    Technologies currently in use cannot effectively detect foreign materials in cotton because they appear the same as the cotton fibres. The objective of this research was to develop a multiwavelength imaging system (MIS) for detecting foreign materials in the spectral region from 405 nm to 940 nm. This method is based on the principle that different materials have different spectral absorptions and reflectance characteristics. Through experiments, we determined an optimal wavelength for detecting each particular kind of foreign material. Then multi-wavelength images of foreign materials were captured using a CCD camera at different optimal wavelengths for each source of illumination. An image fusion algorithm based on wavelet analysis was created to acquire complete information on foreign materials. Imaging results showed that a combination of the wavelengths 405 nm and 850 nm was the most appropriate for detection of a wide range of foreign materials, and this provided an effective method for the detection of these foreign materials in cotton.

  7. Development and operation of a high-throughput accurate-wavelength lens-based spectrometera)

    DOE PAGES

    Bell, Ronald E.

    2014-07-11

    A high-throughput spectrometer for the 400-820 nm wavelength range has been developed for charge exchange recombination spectroscopy or general spectroscopy. A large 2160 mm-1 grating is matched with fast f /1.8 200 mm lenses, which provide stigmatic imaging. A precision optical encoder measures the grating angle with an accuracy ≤ 0.075 arc seconds. A high quantum efficiency low-etaloning CCD detector allows operation at longer wavelengths. A patch panel allows input fibers to interface with interchangeable fiber holders that attach to a kinematic mount behind the entrance slit. The computer-controlled hardware allows automated control of wavelength, timing, f-number, automated data collection,more » and wavelength calibration.« less

  8. Reference Ultraviolet Wavelengths of Cr III Measured by Fourier Transform Spectrometry

    NASA Technical Reports Server (NTRS)

    Smillie, D.G.; Pickering, J.C.; Smith, P.L.

    2008-01-01

    We report Cr III ultraviolet (UV) transition wavelengths measured using a high-resolution Fourier transform spectrometer (FTS), for the first time, available for use as wavelength standards. The doubly ionized iron group element spectra dominate the observed opacity of hot B stars in the UV, and improved, accurate, wavelengths are required for the analysis of astronomical spectra. The spectrum was excited using a chromium-neon Penning discharge lamp and measured with the Imperial College vacuum ultraviolet FTS. 140 classified 3d(exp 3)4s- 3d(exp 3)4p Cr III transition lines, in the spectral range 38,000 to 49,000 cm(exp -1) (2632 to 2041 A), the strongest having wavelength uncertainties less than one part in 10(exp 7), are presented.

  9. Interference based square lattice photonic crystal logic gates working with different wavelengths

    NASA Astrophysics Data System (ADS)

    D'souza, Nirmala Maria; Mathew, Vincent

    2016-06-01

    We propose a new configuration of interference based OR, XOR, NOT and AND optical logic gates on a two dimensional square lattice photonic crystal (PhC) platform. The working of these devices was analyzed by the FDTD method and the operating frequency range was explored using the plane wave expansion method. The XOR and NOT gates have high contrast ratio which is more than 35 dB between high and low logic states, for a particular wavelength. All these devices are operating with multiple wavelengths. The impact of structural parameter like radius on the operating wavelength and Contrast Ratio (CR) was analyzed. It is found that the optimization of structural parameters makes it possible to obtain the operating wavelength allowed by band structure. These proposed devices were made up of linear waveguides and square ring resonator waveguides, without using nonlinear materials, optical amplifiers and external phase shifters.

  10. Wavelength readout system constructed of fiber Fabry-Perot tunable filter and virtual instrument

    NASA Astrophysics Data System (ADS)

    Lü, Chengang; Zhang, Ruifeng; Cheng, Pengfei; Li, Kejia; Wu, Xing; Ge, Chunfeng

    2010-08-01

    The wavelength readout system reported in this paper is chiefly constructed of fiber Fabry-Perot tunable filter (FFP-TF), data acquisition card and a virtual instrument with programmable NI Labview. By combining the dynamic scanning of FFP-TF in C waveband (1520nm-1570nm) with 50nm free spectral range (FSR) and 4000 standard finesse value, the wavelength of a tested laser diode (LD) could be detected accurately, while the spectrum is displayed on line with the help of a virtual instrument to make the spectroscopy quick analysis possible. Furthermore, the scheme can also be applied for wavelength interrogation in fiber Bragg grating (FBG) sensing system. Considering the practibility and economical efficiency of such a system, it will be of great significance to adopt such a wavelength readout system in fiber sensors used for construction, mining, aerospace,etc.

  11. Development and operation of a high-throughput accurate-wavelength lens-based spectrometer

    SciTech Connect

    Bell, Ronald E.

    2014-11-15

    A high-throughput spectrometer for the 400–820 nm wavelength range has been developed for charge exchange recombination spectroscopy or general spectroscopy. A large 2160 mm{sup −1} grating is matched with fast f/1.8 200 mm lenses, which provide stigmatic imaging. A precision optical encoder measures the grating angle with an accuracy ≤0.075 arc sec. A high quantum efficiency low-etaloning CCD detector allows operation at longer wavelengths. A patch panel allows input fibers to interface with interchangeable fiber holders that attach to a kinematic mount at the entrance slit. Computer-controlled hardware allows automated control of wavelength, timing, f-number, automated data collection, and wavelength calibration.

  12. Ultra-wide wavelength tuning of a cascaded Raman random fiber laser.

    PubMed

    Zhang, Lei; Jiang, Huawei; Yang, Xuezong; Pan, Weiwei; Feng, Yan

    2016-01-15

    An ultra-broadband tunable cascaded Raman random fiber laser pumped by a tunable (1020-1080 nm) ytterbium-doped fiber laser is investigated. By continuously adjusting the pump laser wavelength, the Raman random laser tunes accordingly due to the Raman gain competition. By increasing the pump power, up to the 5th order Raman random laser is achieved. As a result, 300 nm of continuous wavelength tuning from 1070 to 1370 nm is achieved by adjusting the pump wavelength and power altogether. The highest output power is 1.8 W at 1360 nm with an optical efficiency of 15% from 1080 nm. To the best of our knowledge, this is the widest wavelength tuning range reported for a random fiber laser so far. PMID:26766677

  13. Separability of agricultural cover types in spectral channels and wavelength regions

    NASA Technical Reports Server (NTRS)

    Kumar, R.

    1977-01-01

    Spectral channels and wavelength regions (visible, near infrared, middle infrared and thermal infrared) were evaluated with respect to their estimated probability of correct classification (Pc) in discriminating agricultural cover types. Multispectral scanner data in twelve spectral channels in the wavelength range of 0.4 to 11.7 microns acquired in the middle of July for three flightlines, were analyzed by applying automatic pattern recognition techniques. The same analysis was performed for the data acquired in the middle of August, 1971, over the same three flightlines, to investigate the effect of time on the results. The effect of deletion of each spectral channel as well as each wavelength region on Pc is given. Values of Pc for all possible combinations of wavelength regions in the subsets of one to twelve spectral channels are also given. The overall values of Pc were found to be greater for the data of the middle of August than the data of the middle of July.

  14. Fibre Optic Temperature Sensor Using Wavelength Distribution Of Fluorescence Emission

    NASA Astrophysics Data System (ADS)

    Grattan, K. T.; Selli, R. K.; Palmer, A. W.

    1987-09-01

    A novel fibre-optic temperature sensor using the red fluorescent emission from ruby crystal, wavelength separated to provide a temperature variant region and a self-generated reference region is described. The principle of this device relies on separating optically the R-line, the variant quantity, from the total emission, which is used to supply the reference. The ratio of the two quantities is then taken to give an accurate temperature measurement which is then calibrated against a standard thermometer. From the calibration curve, a linear profile is seen in the temperature range 293 to 433K and the accuracy of the probe was recorded to be +3K with the response time limited by the mechanical construction in this early work. The upper range level is limited by deviation in the quantum efficiency about 500K.

  15. MAGELLAN: High resolution spectroscopy at FUV and EUV wavelengths

    NASA Technical Reports Server (NTRS)

    Grewing, M.; Alighieri, S. D.; Burton, W.; Coleman, C. I.; Hoekstra, R.; Jamar, C.; Labeque, A.; Laurent, C.; Vidal-Madjar, A.; Rafanelli, P.

    1982-01-01

    The aim of ESA's MAGELLAN mission is to provide high resolution spectra of celestial sources down to sixteenth magnitude over the extreme ultraviolet wavelength range (between 50 and 140 nm). This range extends from studies of interstellar matter in the disc and halo of this and other galaxies, to stellar envelopes, hot and evolved stars, clusters, intergalactic matter, nuclei of galaxies, quasars, and, finally, planets and satellites. The instrument has a nonconventional optical design using only one reflecting surface; a high groove density concave grating collects the star light, diffracts it and focuses its spectrum into a bidimensional windowless detector operated in a photon counting mode. The slitless configuration provides the spectra of all the sources (point like and extended) in the field of view of the grating. This field of view is limited by a grid collimator to reduce the diffuse background, the stray light and the probability of overlapping spectra in crowded fields.

  16. Multi-spectral laser detection and ranging for range profiling and surface characterization

    NASA Astrophysics Data System (ADS)

    Wallace, A. M.; Buller, G. S.; Sung, R. C. W.; Harkins, R. D.; McCarthy, A.; Hernandez-Marin, S.; Gibson, G. J.; Lamb, R.

    2005-06-01

    We describe a new multi-spectral system for range profiling and surface characterization based on time-correlated single photon counting (TCSPC). This system has six laser diode sources with discrete wavelengths in the range 630-972 nm arranged around the circumference of the aperture of a receiving Schmidt-Cassegrain telescope that focuses the multiple wavelength return onto an optical fibre. Single photon avalanche diodes are used to detect the six independent wavelength channels, separated by an optical routing module. We also describe two methods for detecting the numbers, positions, heights and shape parameters of signal returns in the spectra returned from several surfaces within the sensor field of view. The first method has two principal stages, non-parametric bump hunting and maximum likelihood estimation using Poisson statistics. Recently we have adopted a reversible jump Markov chain Monte Carlo approach that has the potential for better detecting hidden or closely overlapping returns.

  17. Multi-Wavelength Observations of Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Williams, B.

    2012-01-01

    Supernova remnants (SNRs) provide a laboratory for studying various astrophysical processes, including particle acceleration, thermal and non thermal emission processes across the spectrum, distribution of heavy elements, the physics of strong shock waves, and the progenitor systems and environments of supernovae. Long studied in radio and X-rays, the past decade has seen a dramatic increase in the detection and subsequent study of SNRs in the infrared and gamma-ray regimes. Understanding the evolution of SNRs and their interaction with the interstellar medium requires a multi-wavelength approach. I will review the various physical processes observed in SNRs and how these processes are intertwined. In particular, I will focus on X-ray and infrared observations, which probe two very different but intrinsically connected phases of the ISM: gas and dust. I will discuss results from multi-wavelength studies of several SNRs at various stages of evolution, including Kepler, RCW 86, and the Cygnus Loop.

  18. WAVELENGTH CALIBRATION OF THE HAMILTON ECHELLE SPECTROGRAPH

    SciTech Connect

    Pakhomov, Yu. V.; Zhao, G.

    2013-10-01

    We present the wavelength calibration of the Hamilton Echelle Spectrograph at Lick Observatory. The main problem with the calibration of this spectrograph arises from the fact that thorium lines are absent in the spectrum of the presumed ThAr hollow-cathode lamp now under operation; numerous unknown strong lines, which have been identified as titanium lines, are present in the spectrum. We estimate the temperature of the lamp's gas which permits us to calculate the intensities of the lines and to select a large number of relevant Ti I and Ti II lines. The resulting titanium line list for the Lick hollow-cathode lamp is presented. The wavelength calibration using this line list was made with an accuracy of about 0.006 Å.

  19. Dual-wavelength laser with topological charge

    NASA Astrophysics Data System (ADS)

    Yu, Haohai; Xu, Miaomiao; Zhao, Yongguang; Wang, Yicheng; Han, Shuo; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang

    2013-09-01

    We demonstrate the simultaneous oscillation of different photons with equal orbital angular momentum in solid-state lasers for the first time to our knowledge. Single tunable Hermite-Gaussian (HG0,n) (0 ≤ n ≤ 7) laser modes with dual wavelength were generated using an isotropic cavity. With a mode-converter, the corresponding Laguerre-Gaussian (LG0,n) laser modes were obtained. The oscillating laser modes have two types of photons at the wavelengths of 1077 and 1081 nm and equal orbital angular momentum of nħ per photon. These results identify the possibility of simultaneous oscillation of different photons with equal and controllable orbital angular momentum. It can be proposed that this laser should have promising applications in many fields based on its compact structure, tunable orbital angular momentum, and simultaneous oscillation of different photons with equal orbital angular momentum.

  20. The Long Wavelength Array Software Library

    NASA Astrophysics Data System (ADS)

    Dowell, Jayce; Wood, Daniel; Stovall, Kevin; Ray, Paul S.; Clarke, Tracy; Taylor, Gregory

    2012-12-01

    The Long Wavelength Array Software Library (LSL) is a Python module that provides a collection of utilities to analyze and export data collected at the first station of the Long Wavelength Array, LWA1. Due to the nature of the data format and large-N (≳100 inputs) challenges faced by the LWA, currently available software packages are not suited to process the data. Using tools provided by LSL, observers can read in the raw LWA1 data, synthesize a filter bank, and apply incoherent de-dispersion to the data. The extensible nature of LSL also makes it an ideal tool for building data analysis pipelines and applying the methods to other low frequency arrays.

  1. Aperture-synthesis interferometry at optical wavelengths

    NASA Technical Reports Server (NTRS)

    Burke, Bernard F.

    1987-01-01

    The prospects for applying aperture-synthesis interferometry to the optical domain are reviewed. The radio examples such as the VLA provide a model, since the concepts are equally valid for radio and optical wavelengths. If scientific problems at the milliarc-second resolution level (or better) are to be addressed, a space-based optical array seems to be the only practical alternative, for the same reasons that dictated array development at radio wavelengths. One concept is examined, and speculations are offered concerning the prospects for developing real systems. Phase-coherence is strongly desired for a practical array, although self-calibration and phase-closure techniques allow one to relax the restriction on absolute phase stability. The design of an array must be guided by the scientific problems to be addressed.

  2. Coordinated observations of PHEMU at radio wavelengths.

    NASA Astrophysics Data System (ADS)

    Pluchino, S.; Schillirò, F.; Salerno, E.; Pupillo, G.; Kraus, A.; Mack, K.-H.

    We present preliminary results for our study of mutual phenomena of the Galilean satellites performed at radio wavelengths with the Medicina and Noto antennas of the Istituto di Radioastronomia \\textendash{} INAF, and with the Effelsberg 100-m radio telescope of the Max-Planck-Institute for Radioastronomy. Measurements of the radio flux density variation occurred during the mutual occultations of Io by Europa and Ganymede were carried out during the PHEMU09 campaign at K- and Q-band. Flux density variations observed for the first time at radio wavelengths are consistent with the typical optical patterns measured when partial occultations occurred. The flux density drops indicate a non-linear dependence with the percentage of overlapped area.

  3. A Theory of Access

    ERIC Educational Resources Information Center

    Ribot, Jesse C.; Peluso, Nancy Lee

    2003-01-01

    The term "access" is frequently used by property and natural resource analysts without adequate definition. In this paper we develop a concept of access and examine a broad set of factors that differentiate access from property. We define access as "the "ability" to derive benefits from things," broadening from property's classical definition as…

  4. Short wavelength striations on expanding plasma clouds

    SciTech Connect

    Winske, D.; Gary, S.P.

    1989-01-01

    The growth and evolution of short wavelength (

  5. Deformable mirror for short wavelength applications

    DOEpatents

    Chapman, Henry N.; Sweeney, Donald W.

    1999-01-01

    A deformable mirror compatible with short wavelength (extreme ultraviolet) radiation that can be precisely controlled to nanometer and subnanometer accuracy is described. Actuators are coupled between a reaction plate and a face plate which has a reflective coating. A control system adjusts the voltage supplied to the actuators; by coordinating the voltages supplied to the actuators, the reflective surface of the mirror can be deformed to correct for dimensional errors in the mirror or to produce a desired contour.

  6. Tuning the Activation Wavelength of Photochromic Oxazines.

    PubMed

    Swaminathan, Subramani; Garcia-Amorós, Jaume; Thapaliya, Ek Raj; Nonell, Santi; Captain, Burjor; Raymo, Françisco M

    2016-06-17

    The activation wavelength of a photochromic oxazine can be shifted bathochromically with the introduction of a methoxy substituent on the chromophore responsible for initiating the photochemical transformation. This structural modification permits switching under mild illumination conditions, enhances the photoisomerization quantum yield and ensures outstanding fatigue resistance. Thus, these results can guide the design of new members of this family of photoresponsive molecular switches with improved photochemical and photophysical properties. PMID:27003328

  7. Tuning the Activation Wavelength of Photochromic Oxazines.

    PubMed

    Swaminathan, Subramani; Garcia-Amorós, Jaume; Thapaliya, Ek Raj; Nonell, Santi; Captain, Burjor; Raymo, Françisco M

    2016-06-17

    The activation wavelength of a photochromic oxazine can be shifted bathochromically with the introduction of a methoxy substituent on the chromophore responsible for initiating the photochemical transformation. This structural modification permits switching under mild illumination conditions, enhances the photoisomerization quantum yield and ensures outstanding fatigue resistance. Thus, these results can guide the design of new members of this family of photoresponsive molecular switches with improved photochemical and photophysical properties.

  8. Effective wavelength scaling of rectangular aperture antennas.

    PubMed

    Chen, Yuanyuan; Yu, Li; Zhang, Jiasen; Gordon, Reuven

    2015-04-20

    We investigate the resonances of aperture antennas from the visible to the terahertz regime, with comparison to comprehensive simulations. Simple piecewise analytic behavior is found for the wavelength scaling over the entire spectrum, with a linear regime through the visible and near-IR. This theory will serve as a useful and simple design tool for applications including biosensors, nonlinear plasmonics and surface enhanced spectroscopies. PMID:25969079

  9. Varactor diodes for millimeter and submillimeter wavelengths

    NASA Technical Reports Server (NTRS)

    Rizzi, Brian J.; Hesler, Jeffrey L.; Dossal, Hasan; Crowe, Thomas W.

    1992-01-01

    Whisker-contacted GaAs Schottky barrier varactor diodes are the most common high-frequency multiplier element in use today. They are inherently simple devices that have very high frequency response and have been used to supply local oscillator power for Schottky heterodyne receivers to frequencies approaching 700 GHz. This paper discusses the development of improved varactor diode technology for space based applications at millimeter and submillimeter wavelengths.

  10. Small Satellite Access of the Space Network

    NASA Technical Reports Server (NTRS)

    Horan, Stephen; Minnix, Timothy O.; Vigil, J. S.

    1999-01-01

    Small satellites have been perceived as having limited access to NASA's Space Network (SN). The potential for satellite access of the space network when the design utilizes a fixed antenna configuration and low-power, coded transmission is analyzed. From the analysis, satellites using this configuration in high-inclination orbits are shown to have a daily data throughput in the 100 to 1000 Mbit range using the multiple access communications service.

  11. Broadly tunable dual-wavelength erbium-doped ring fiber laser based on a high-birefringence fiber loop mirror

    NASA Astrophysics Data System (ADS)

    Sun, H. B.; Liu, X. M.; Gong, Y. K.; Li, X. H.; Wang, L. R.

    2010-02-01

    A broadly tunable dual-wavelength erbium-doped ring fiber laser based on a high-birefringence fiber loop mirror (HiBi-FLM) and a polarization controller is demonstrated experimentally. The measured transmission spectrum of HiBi-FLM covers a wide range from 1525 to 1575 nm. The wavelength of proposed laser can be flexibly tunable during this range of ˜50 nm by adjusting the polarization controller. In addition, the spacing of two wavelengths is adjustable by changing the length of HiBi fiber. The dual-wavelength lasers with the HiBi fiber length of 1 and 2 m are experimentally demonstrated and compared. The experimental results show that the proposed laser can stably operate on two wavelengths simultaneously at room temperature, and the output peak power variation is about 0.5 dB during 40 min.

  12. Two-wavelength lidar inversion algorithm.

    PubMed

    Kunz, G J

    1999-02-20

    Potter [Appl. Opt. 26, 1250 (1987)] has presented a method to determine profiles of the atmospheric aerosol extinction coefficients by use of a two-wavelength lidar with the assumptions of a constant value for the extinction-to-backscatter ratio for each wavelength and a constant value for the ratio between the two extinction coefficients at the two wavelengths. Triggered by this idea, Ackermann [Appl. Opt. 36, 5134 (1997)] expanded this method to consider lidar returns that are a composition of scattering by atmospheric aerosols and molecules, assuming that the molecular scattering is known. In both papers the method is based on the well-known solutions of Bernoulli's differential equation in an iterative scheme with an unknown boundary transmission condition. This boundary condition is less sensitive to noise than boundary extinction conditions. My main purpose is to critically consider the principle behind Potter's method, because it seems that there are several reasons why the number of solutions is not limited to one, as suggested by his original work.

  13. Wavelength switching in an optical klystron

    SciTech Connect

    Berryman, K.W.; Smith, T.I.

    1995-12-31

    A symmetric optical klystron consists of two identical undulator sections separated a dispersive section. For a device of a given length, an optical klystron is capable of producing much more bunching, and therefore more gain, than a traditional undulator. Another consequence of introducing dispersion between two undulator sections is that the overall spontaneous radiation pattern results from the interference between the two undulator sections, and as such resembles a standard undulator radiation pattern modulated by a sinusoidal interference term. The presence of several wavelength peaks in the spontaneous lineshape implies an equal number of peaks in the gain spectrum. If the strength of the dispersion section is adjusted to provide nearly equal gain on the two largest of these peaks, then they will compete, and the FEL may switch wavelengths based on noise, cavity length, or other perturbations. We provide the first observations of this behavior, using the FIREFLY system at the Stanford Picosecond FEL Center. In FIREFLY, relative wavelength switching by more than 3%--more than twice the laser linewidth-has been observed by varying dispersion section strength, while at intermediate points stable switching has also been observed as a function of cavity length.

  14. Multiple wavelength X-ray monochromators

    DOEpatents

    Steinmeyer, Peter A.

    1992-11-17

    An improved apparatus and method is provided for separating input x-ray radiation containing first and second x-ray wavelengths into spatially separate first and second output radiation which contain the first and second x-ray wavelengths, respectively. The apparatus includes a crystalline diffractor which includes a first set of parallel crystal planes, where each of the planes is spaced a predetermined first distance from one another. The crystalline diffractor also includes a second set of parallel crystal planes inclined at an angle with respect to the first set of crystal planes where each of the planes of the second set of parallel crystal planes is spaced a predetermined second distance from one another. In one embodiment, the crystalline diffractor is comprised of a single crystal. In a second embodiment, the crystalline diffractor is comprised of a stack of two crystals. In a third embodiment, the crystalline diffractor includes a single crystal that is bent for focussing the separate first and second output x-ray radiation wavelengths into separate focal points.

  15. Multiple wavelength X-ray monochromators

    DOEpatents

    Steinmeyer, P.A.

    1992-11-17

    An improved apparatus and method is provided for separating input x-ray radiation containing first and second x-ray wavelengths into spatially separate first and second output radiation which contain the first and second x-ray wavelengths, respectively. The apparatus includes a crystalline diffractor which includes a first set of parallel crystal planes, where each of the planes is spaced a predetermined first distance from one another. The crystalline diffractor also includes a second set of parallel crystal planes inclined at an angle with respect to the first set of crystal planes where each of the planes of the second set of parallel crystal planes is spaced a predetermined second distance from one another. In one embodiment, the crystalline diffractor is comprised of a single crystal. In a second embodiment, the crystalline diffractor is comprised of a stack of two crystals. In a third embodiment, the crystalline diffractor includes a single crystal that is bent for focusing the separate first and second output x-ray radiation wavelengths into separate focal points. 3 figs.

  16. Peripheral detection and resolution with mid-/long-wavelength and short-wavelength sensitive cone systems.

    PubMed

    Zhu, Hai-Feng; Zele, Andrew J; Suheimat, Marwan; Lambert, Andrew J; Atchison, David A

    2016-08-01

    This study compared neural resolution and detection limits of the human mid-/long-wavelength and short-wavelength cone systems with anatomical estimates of photoreceptor and retinal ganglion cell spacings and sizes. Detection and resolution limits were measured from central fixation out to 35° eccentricity across the horizontal visual field using a modified Lotmar interferometer. The mid-/long-wavelength cone system was studied using a green (550 nm) test stimulus to which S-cones have low sensitivity. To bias resolution and detection to the short-wavelength cone system, a blue (450 nm) test stimulus was presented against a bright yellow background that desensitized the M- and L-cones. Participants were three trichromatic males with normal visual functions. With green stimuli, resolution showed a steep central-peripheral gradient that was similar between participants, whereas the detection gradient was shallower and patterns were different between participants. Detection and resolution with blue stimuli were poorer than for green stimuli. The detection of blue stimuli was superior to resolution across the horizontal visual field and the patterns were different between participants. The mid-/long-wavelength cone system's resolution is limited by midget ganglion cell spacing and its detection is limited by the size of the M- and L-cone photoreceptors, consistent with previous observations. We found that no such simple relationships occur for the short-wavelength cone system between resolution and the bistratified ganglion cell spacing, nor between detection and the S-cone photoreceptor sizes.

  17. Peripheral detection and resolution with mid-/long-wavelength and short-wavelength sensitive cone systems.

    PubMed

    Zhu, Hai-Feng; Zele, Andrew J; Suheimat, Marwan; Lambert, Andrew J; Atchison, David A

    2016-08-01

    This study compared neural resolution and detection limits of the human mid-/long-wavelength and short-wavelength cone systems with anatomical estimates of photoreceptor and retinal ganglion cell spacings and sizes. Detection and resolution limits were measured from central fixation out to 35° eccentricity across the horizontal visual field using a modified Lotmar interferometer. The mid-/long-wavelength cone system was studied using a green (550 nm) test stimulus to which S-cones have low sensitivity. To bias resolution and detection to the short-wavelength cone system, a blue (450 nm) test stimulus was presented against a bright yellow background that desensitized the M- and L-cones. Participants were three trichromatic males with normal visual functions. With green stimuli, resolution showed a steep central-peripheral gradient that was similar between participants, whereas the detection gradient was shallower and patterns were different between participants. Detection and resolution with blue stimuli were poorer than for green stimuli. The detection of blue stimuli was superior to resolution across the horizontal visual field and the patterns were different between participants. The mid-/long-wavelength cone system's resolution is limited by midget ganglion cell spacing and its detection is limited by the size of the M- and L-cone photoreceptors, consistent with previous observations. We found that no such simple relationships occur for the short-wavelength cone system between resolution and the bistratified ganglion cell spacing, nor between detection and the S-cone photoreceptor sizes. PMID:27580041

  18. Wavelength optimization using available laser diodes in spectral near-infrared optical tomography.

    PubMed

    Chen, Liang-Yu; Pan, Min-Cheng; Yan, Chung-Chen; Pan, Min-Chun

    2016-07-20

    For employing optimized wavelengths, a near-infrared (NIR) tomographic imaging system with multiwavelengths in a continuous wave (CW) enables us to provide accurate information of chromophores. In this paper, we discuss wavelength optimization with a selection from commercial laser diodes. Through theoretical analysis, the residual norm (R) and the condition number (κ) represent the uniqueness of a matrix problem and the smooth singular-value distribution of each chromophore, respectively. The optimum wavelengths take place for large R and small κ. We considered a total of 38 wavelengths of laser diodes in the range of 633-980 nm commercially available to discover optimum sets for a broad range of chromophore combinations. In the 38 wavelengths, there exists 501,942 (C538), 2,760,681 (C638), and 12,620,256 (C738) combinations of five, six, and seven wavelength sets, respectively, for accurately estimating chromophores (HbO2, HbR, H2O, and lipids), water, lipids, and the scattering prefactor A. With the numerical calculation, the top 10 wavelength sets were selected based on the principle of large R and small κ. In the study, the chromophore concentration for young and elderly women are investigated; finally, choosing the laser diodes with a wavelength of 650, 690, 705, 730, 870/880, 915, and 937 nm is recommended either for young or elderly women to construct a spectral NIR tomographic imaging system in the CW domain. Simulated data were used to validate the claims.

  19. Wavelength optimization using available laser diodes in spectral near-infrared optical tomography.

    PubMed

    Chen, Liang-Yu; Pan, Min-Cheng; Yan, Chung-Chen; Pan, Min-Chun

    2016-07-20

    For employing optimized wavelengths, a near-infrared (NIR) tomographic imaging system with multiwavelengths in a continuous wave (CW) enables us to provide accurate information of chromophores. In this paper, we discuss wavelength optimization with a selection from commercial laser diodes. Through theoretical analysis, the residual norm (R) and the condition number (κ) represent the uniqueness of a matrix problem and the smooth singular-value distribution of each chromophore, respectively. The optimum wavelengths take place for large R and small κ. We considered a total of 38 wavelengths of laser diodes in the range of 633-980 nm commercially available to discover optimum sets for a broad range of chromophore combinations. In the 38 wavelengths, there exists 501,942 (C538), 2,760,681 (C638), and 12,620,256 (C738) combinations of five, six, and seven wavelength sets, respectively, for accurately estimating chromophores (HbO2, HbR, H2O, and lipids), water, lipids, and the scattering prefactor A. With the numerical calculation, the top 10 wavelength sets were selected based on the principle of large R and small κ. In the study, the chromophore concentration for young and elderly women are investigated; finally, choosing the laser diodes with a wavelength of 650, 690, 705, 730, 870/880, 915, and 937 nm is recommended either for young or elderly women to construct a spectral NIR tomographic imaging system in the CW domain. Simulated data were used to validate the claims. PMID:27463930

  20. On the Capability of Artificial Neural Networks to Compensate Nonlinearities in Wavelength Sensing

    PubMed Central

    Hafiane, Mohamed Lamine; Dibi, Zohir; Manck, Otto

    2009-01-01

    An intelligent sensor for light wavelength readout, suitable for visible range optical applications, has been developed. Using buried triple photo-junction as basic pixel sensing element in combination with artificial neural network (ANN), the wavelength readout with a full-scale error of less than 1.5% over the range of 400 to 780 nm can be achieved. Through this work, the applicability of the ANN approach in optical sensing is investigated and compared with conventional methods, and a good compromise between accuracy and the possibility for on-chip implementation was thus found. Indeed, this technique can serve different purposes and may replace conventional methods. PMID:22574051