WorldWideScience

Sample records for visible spectral range

  1. A New and Inexpensive Pyranometer for the Visible Spectral Range

    Directory of Open Access Journals (Sweden)

    Miguel A. Martínez

    2009-06-01

    Full Text Available This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm, whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine error minimisation and all this at a very low cost, tens of times lower than that of commercial thermopile-based devices. This new photodiode-based pyranometer overcomes traditional problems in this type of device and offers similar characteristics to those of thermopile-based pyranometers and, therefore, can be used in any installation where reliable measurement of solar irradiance is necessary, especially in those where cost is a deciding factor in the choice of a meter. This new pyranometer has been registered in the Spanish Patent and Trademark Office under the number P200703162.

  2. Broadband black phosphorus optical modulator in visible to mid-infrared spectral range

    OpenAIRE

    Zhang, Rui; Zhang, Yuxia; Yu, Haohai; Zhang, Huaijin; Yang, Ruinong; Yang, Bingchao; Liu, Zhongyuan; Jiyang WANG

    2015-01-01

    Black phosphorous (BP), a two-dimensional (2D) material, has a direct bandgap, which fills up the bandgap lacuna left by graphene topological insulators and transition-metal dichalcogenides because of its dependence on the layers and applied strains. Theoretically, the direct and tunable band gap indicates the broadband applications in optoelectronics with high efficiencies in the spectral range from visible to mid-infrared. Here, a BP broadband optical modulator is experime...

  3. Continuous Spatial Tuning of Laser Emissions in a Full Visible Spectral Range

    Directory of Open Access Journals (Sweden)

    Mi-Yun Jeong

    2011-03-01

    Full Text Available In order to achieve a continuous tuning of laser emission, the authors designed and fabricated three types of cholesteric liquid crystal cells with pitch gradient, a wedge cell with positive slope, a wedge cell with negative slope, and a parallel cell. The length of the cholesteric liquid crystal pitch could be elongated up to 10 nm, allowing the lasing behavior of continuous or discontinuous spatial tuning determined by the boundary conditions of the cholesteric liquid crystal cell. In the wedge cell with positive slope, the authors demonstrated a continuous spatial laser tuning in the near full visible spectral range, with a tuning resolution less than 1 nm by pumping with only a single 355 nm laser beam. This continuous tuning behavior is due to the fact that the concentration of pitch gradient matches the fixed helical pitch determined by the cell thickness. This characteristic continuous spatial laser tuning could be confirmed again by pumping with a 532 nm laser beam, over 90 nm in the visible spectral range. The scheme of the spatial laser tuning in the wedge cell bearing a pitch gradient enabled a route to designing small-sized optical devices that allow for a wide tunability of single-mode laser emissions.

  4. Broadband black phosphorus optical modulator in visible to mid-infrared spectral range

    CERN Document Server

    Zhang, Rui; Yu, Haohai; Zhang, Huaijin; Yang, Ruinong; Yang, Bingchao; Liu, Zhongyuan; Wang, Jiyang

    2015-01-01

    Black phosphorous (BP), a two-dimensional (2D) material, has a direct bandgap, which fills up the bandgap lacuna left by graphene topological insulators and transition-metal dichalcogenides because of its dependence on the layers and applied strains. Theoretically, the direct and tunable band gap indicates the broadband applications in optoelectronics with high efficiencies in the spectral range from visible to mid-infrared. Here, a BP broadband optical modulator is experimentally constructed and the passively modulated lasers at 639 nm (red), 1.06 um (near-infrared) and 2.1 um (mid-infrared) are realized by using the BP optical modulator as the saturable absorber in bulk lasers. The obtained results provide a promising alternative for rare broadband optical modulators and broaden the application range of BP in photonics.

  5. Detector calibration in the spectral range from vacuum-ultraviolet to visible

    International Nuclear Information System (INIS)

    The Electrotechnical Laboratory is responsible for establishing optical units in Japan. Optical units are classified into photometric units which are weighted by human eye responsivity such as candela and radiometric units which are pure physical units such as watt. In this report, the overview of the techniques to determine the radiometric scales for detectors in the spectral region from ultraviolet to visible is described. The characteristics of semiconductor photodiodes as the primary standard detector and rare gas ionization chambers as another example of the primary standard detector are discussed. For characterizing the response of detectors, quantum efficiency or responsivity is used. The definitions of both are given. In order to realize a detector standard, the calibration with a primary standard detector the use of a primary standard radiation source and an efficiency-evaluated monochromatizing component, or the extension of spectral range of an existing detector standard by using a thermal detector is carried out. Noble gas ionization chambers as the primary standard detector in vacuum ultraviolet region, the self-calibration method, and semiconductor photodiodes as the absolute detector are described. (K.I.)

  6. Luminescent properties of the ZnSe:Yb crystals in the visible spectral range

    Energy Technology Data Exchange (ETDEWEB)

    Radevici, I., E-mail: ivarad@utu.fi [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Faculty of Physics and Engineering, Moldova State University, Mateevici str. 60, MD-2009, Chisinau, Republic of Moldova (Moldova, Republic of); Sushkevich, K. [Faculty of Physics and Engineering, Moldova State University, Mateevici str. 60, MD-2009, Chisinau, Republic of Moldova (Moldova, Republic of); Sirkeli, V. [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Faculty of Physics and Engineering, Moldova State University, Mateevici str. 60, MD-2009, Chisinau, Republic of Moldova (Moldova, Republic of); Huhtinen, H. [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Nedeoglo, D. [Faculty of Physics and Engineering, Moldova State University, Mateevici str. 60, MD-2009, Chisinau, Republic of Moldova (Moldova, Republic of); Paturi, P. [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland)

    2013-11-15

    Luminescent properties of the ytterbium doped zinc selenide crystals with various concentrations of the doping impurity in 0.03–8 at % range within the temperature interval from 6 K to 300 K were studied. It was shown that ytterbium does not form any proper photoluminescence (PL) bands in the visible spectral range, but it has significant influence on the crystals luminescent properties by changing their defect composition. An attempt to determine ytterbium ion surroundings in the crystal lattice was made based on the obtained experimental results. An assumption about simultaneous compensation of donor and acceptor defects as a result of doping annealing in Zn+X at % Yb melt was made. -- Highlights: • ZnSe:Yb crystals with Yb concentration within 0.03–8 at% range were obtained • Temperature and concentration dependences of ZnSe:Yb PL properties were studied • Ytterbium impurity contribution to formation of the PL bans was determined • A model explaining Yb interaction with native and extrinsic defects was proposed.

  7. Spectral estimation of soil water content in visible and near infra-red range

    Directory of Open Access Journals (Sweden)

    Attila Nagy

    2014-08-01

    Full Text Available Soils can be examined on the basis of spectral data, using such methods with which the reflected radiation can be divided into a large number of (several hundreds small spectral channel (some nm. Based on the spectral characteristics of the soils, or the different index numbers calculated from hyperspectral data water content of soils can be well characterized. The examined soil samples were coming from different apple orchards of which soils had different physical characteristics (sandy loamy and clay. The goals of my experiments were the evaluation of spectral measurement method for soil content detection, and to carry out algorithms for fast field scale spectral evaluation of different soil water content. The spectral measuring was carried out by laboratory scale AvaSpec 2048 spectrometer at 400 – 1000 nm wavelength interval with 0.6 nm spectral resolutions and by ASD FieldSpec Junior at 350 – 2500 nm. After drying, dry soil samples were watered by 2.5 m/m% till maximal saturation, and each wetting was measured spectrally. Based on spectral properties, reflectances were decreased in the whole spectral range within the continuous wetting due to the high absorption characteristics of water. The most water sensitive spectral ranges were selected by principal component, and such algorithms were created, with which the water content can be detectable in the certain soil. The algorithms can facilitate farmers for irrigation scheduling of their orchards. These results can also be utilizable in precision water management, since it can be a basis for such integrated active sensors with LED or laser light source, measuring reflectance at the certain spectral range, which can facilitate real time water status assessment of orchards.

  8. Experimental demonstration of a non-resonant hyperlens in the visible spectral range.

    Science.gov (United States)

    Sun, Jingbo; Shalaev, Mikhail I; Litchinitser, Natalia M

    2015-01-01

    A metamaterial hyperlens offers a solution to overcome the diffraction limit by transforming evanescent waves responsible for imaging subwavelength features of an object into propagating waves. However, the first realizations of optical hyperlenses were limited by significant resonance-induced losses. Here we report the experimental demonstration of a non-resonant waveguide-coupled hyperlens operating in the visible wavelength range. A detailed investigation of various materials systems proves that a radial fan-shaped configuration is superior to the concentric layer-based configuration in that it relies on non-resonant negative dielectric response, and, as a result, enables low-loss performance in the visible range. PMID:25998241

  9. A synchrotron-radiation-based variable angle ellipsometer for the visible to vacuum ultraviolet spectral range

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, M. D., E-mail: maciej.neumann@isas.de; Cobet, C.; Esser, N. [Leibniz-Institut für Analytische Wissenschaften – ISAS – e.V., 12489 Berlin (Germany); Kaser, H.; Kolbe, M.; Gottwald, A.; Richter, M. [Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin (Germany)

    2014-05-15

    A rotating analyzer spectroscopic polarimeter and ellipsometer with a wide-range ?-2? goniometer installed at the Insertion Device Beamline of the Metrology Light Source in Berlin is presented. With a combination of transmission- and reflection-based polarizing elements and the inherent degree of polarization of the undulator radiation, this ellipsometer is able to cover photon energies from about 2 eV up to 40 eV. Additionally, a new compensator design based on a CaF{sub 2} Fresnel rhomb is presented. This compensator allows ellipsometric measurements with circular polarization in the vacuum ultraviolet spectral range and thus, for example, the characterization of depolarizing samples. The new instrument was initially used for the characterization of the polarization of the beamline. The technical capabilities of the ellipsometer are demonstrated by a cohesive wide-range measurement of the dielectric function of epitaxially grown ZnO.

  10. A synchrotron-radiation-based variable angle ellipsometer for the visible to vacuum ultraviolet spectral range

    Science.gov (United States)

    Neumann, M. D.; Cobet, C.; Kaser, H.; Kolbe, M.; Gottwald, A.; Richter, M.; Esser, N.

    2014-05-01

    A rotating analyzer spectroscopic polarimeter and ellipsometer with a wide-range ?-2? goniometer installed at the Insertion Device Beamline of the Metrology Light Source in Berlin is presented. With a combination of transmission- and reflection-based polarizing elements and the inherent degree of polarization of the undulator radiation, this ellipsometer is able to cover photon energies from about 2 eV up to 40 eV. Additionally, a new compensator design based on a CaF2 Fresnel rhomb is presented. This compensator allows ellipsometric measurements with circular polarization in the vacuum ultraviolet spectral range and thus, for example, the characterization of depolarizing samples. The new instrument was initially used for the characterization of the polarization of the beamline. The technical capabilities of the ellipsometer are demonstrated by a cohesive wide-range measurement of the dielectric function of epitaxially grown ZnO.

  11. Optical constants of liquid UO2 in the visible spectral range obtained from reflectivity measurements

    International Nuclear Information System (INIS)

    The optical constants, n,k, of liquid urania were determined from reflectivity measurements with plane-polarized light. Measurements were made with an integrating-sphere laser reflectometer in the wavelength range 450-750 nm at temperatures between 3000 and 4000 K. Consistent results have been obtained for different angles of incidence. The optical constants show little variation with the wavelength and temperature. Liquid urania proves to be opaque to radiation in the whole spectral range studied. Average values of n = 1.7 and k = 0.8 are given for the temperature range 3100-3600 K. From this result it is concluded that internal thermal radiation cannot cause a significant increase in thermal conductivity urania upon melting. (orig.)

  12. Spectral estimation of soil water content in visible and near infra-red range

    OpenAIRE

    Nagy, Attila; Riczu, Péter; Gálya, Bernadett; Tamás, János

    2014-01-01

    Soils can be examined on the basis of spectral data, using such methods with which the reflected radiation can be divided into a large number of (several hundreds) small spectral channel (some nm). Based on the spectral characteristics of the soils, or the different index numbers calculated from hyperspectral data water content of soils can be well characterized. The examined soil samples were coming from different apple orchards of which soils had different physical characteristics (sandy lo...

  13. Development of high-gain gaseous photomultipliers for the visible spectral range

    CERN Document Server

    Lyashenko, A V; Chechik, R; Santos, J M F Dos; Amaro, F D; Veloso, J F C A

    2009-01-01

    We summarize the development of visible-sensitive gaseous photomultipliers, combining a semitransparent bi-alkali photocathode with a state-of-the-art cascaded electron multiplier. The latter has high photoelectron collection efficiency and a record ion blocking capability. We describe in details the system and methods of photocathode production and characterization, their coupling with the electron multiplier and the gaseous-photomultiplier operation and characterization in a continuous mode. We present results on the properties of laboratory-produced K$_2$CsSb, Cs$_3$Sb and Na$_2$KSb photocathodes and report on their stability and QE in gas; K$_2$CsSb photocathodes yielded QE values in Ar/CH$_4$(95/5) above 30% at wavelengths of 360-400 nm. The novel gaseous photomultiplier yielded stable operation at gains of 10$^5$, in continuous operation mode, in 700 Torr of this gas; its sensitivity to single photons was demonstrated. Other properties are described. The successful detection of visible light with this g...

  14. Development of high-gain gaseous photomultipliers for the visible spectral range

    International Nuclear Information System (INIS)

    We summarize the development of visible-sensitive gaseous photomultipliers, combining a semitransparent bi-alkali photocathode with a state-of-the-art cascaded electron multiplier. The latter has high photoelectron collection efficiency and a record ion blocking capability. We describe in details the system and methods of photocathode production and characterization, their coupling with the electron multiplier and the gaseous-photomultiplier operation and characterization in a continuous mode. We present results on the properties of laboratory-produced K2CsSb, Cs3Sb and Na2KSb photocathodes and report on their stability and QE in gas; K2CsSb photocathodes yielded QE values in Ar/CH4(95/5) above 30% at wavelengths of 360-400 nm. The novel gaseous photomultiplier yielded stable operation at gains of 105, in continuous operation mode, in 700 Torr of this gas; its sensitivity to single photons was demonstrated. Other properties are described. The successful detection of visible light with this gas-photomultiplier pave ways towards further development of large-area sealed imaging detectors, of flat geometry, insensitive to magnetic fields, which might have significant impact on light detection in numerous fields.

  15. AlInP-based rolled-up microtube resonators with colloidal nanocrystals operating in the visible spectral range

    Science.gov (United States)

    Strelow, Ch.; Kietzmann, S.; Schramm, A.; Seher, R.; Penttinen, J.-P.; Hakkarainen, T. V.; Mews, A.; Kipp, T.

    2012-09-01

    We report on the realization of AlInP rolled-up microtubes that can be used as high refractive index optical resonators operating in the visible spectral range down to a wavelength of at least 530 nm. Furthermore, colloidal CdSe/CdS/ZnS core-shell-shell nanocrystals were deposited close to the microtube wall by fluid filling of the microtube and subsequent evaporation of the solvent. The optical modes of the microtube resonator are excited via coupling of the nanocrystals to the evanescent fields of the modes. By embedding the nanocrystal emitters in a polymer film, an enhanced nanocrystal stability is obtained. The film is studied by the built-in refractometer of the microtube.

  16. Photoluminescent (CdSe)ZnS quantum dot-polymethylmethacrylate polymer composite thin films in the visible spectral range

    International Nuclear Information System (INIS)

    We synthesized (CdSe)ZnS quantum dot (QD)-polymethylmethacrylate (PMMA) polymer composite and fabricated QD-polymer composite films. We produced the CdSe and (CdSe)ZnS QDs by direct colloidal chemical synthesis and the surface-passivation method-an overcoating of the dots with a larger-bandgap material. PMMA is transparent in the visible spectral range and was chosen as the embedding matrix for QDs. A 28%(wt/wt) of PMMA in MMA was the most appropriate concentration to produce a film of good quality and maximize the solubility of quantum dots without phase separation of the QDs from the matrix. We fabricated green or red light emitting (CdSe)ZnS QD-PMMA polymer composite film by combining the green or red light emitting (CdSe)ZnS dots with PMMA of high optical transparency in the visible region and spin-coating the composite solution. The fabricated green light emitting (CdSe)ZnS-PMMA composite film had a good quantum yield of 40% and a narrow emission band at 543 nm with a full width at half maximum of ?35 nm. A white light emitting device can be fabricated by combining our green/red light emitting QD-polymer composites with a blue light emitting LED as an excitation source. Our QD-polymer composites can be applied to flexible coloured filters, large-area coloured wall-papers and full colour displays

  17. Analysis of global water vapour trends from satellite measurements in the visible spectral range

    Directory of Open Access Journals (Sweden)

    S. Mieruch

    2008-02-01

    Full Text Available Global water vapour total column amounts have been retrieved from spectral data provided by the Global Ozone Monitoring Experiment (GOME flying on ERS-2, which was launched in April 1995, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY onboard ENVISAT launched in March 2002. For this purpose the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS approach has been used. The combination of the data from both instruments provides us with a long-term global data set spanning more than 11 years with the potential of extension up to 2020 by GOME-2 data on MetOp.

    Using linear and non-linear methods from time series analysis and standard statistics the trends of H2O columns and their errors have been calculated. In this study, factors affecting the trend such as the length of the time series, the magnitude of the variability of the noise, and the autocorrelation of the noise are investigated. Special emphasis has been placed on the calculation of the statistical significance of the observed trends, which reveal significant local changes from ?5% per year to +5% per year. These significant trends are distributed over the whole globe. Increasing trends have been calculated for Greenland, East Europe, Siberia and Oceania, whereas decreasing trends have been observed for the northwest USA, Central America, Amazonia, Central Africa and the Arabian Peninsular.

  18. Emission intensity in the visible and IR spectral ranges from Si-based structures formed by direct bonding with simultaneous doping with erbium (Er) and europium (Eu)

    International Nuclear Information System (INIS)

    The photo- and electroluminescence spectra of silicon-based structures formed by direct bonding with simultaneous doping with rare-earth metals are studied. It is shown that emission in the visible and IR spectral ranges can be obtained from n-Si:Er/p-Si and n-Si:Eu/p-Si structures fabricated by the method suggested in the study. The results obtained make this method promising for the fabrication of optoelectronic devices

  19. Studies in the infrared, visible and soft-X-ray range in order to prove the suitability of the BESSY electron storage ring as a standard of spectral radiant power

    International Nuclear Information System (INIS)

    The spectral radiant power of the electron storage ring BESSY has been measured absolutely in the infrared and visible, and its angular distribution in the infrared, visible and soft X-ray range. The results prove BESSY to be a standard of calculable spectral radiant power, at least for wavelengths from 0.5 nm to 1000 nm. (orig.)

  20. Optical, spectral and phase-matching properties of BIBO, BBO and LBO crystals for optical parametric oscillation in the visible and near-infrared wavelength ranges

    Science.gov (United States)

    Akbari, R.; Major, A.

    2013-03-01

    The phase-matching properties of BIBO, BBO and LBO crystals for optical parametric oscillators (OPO) with wavelength tuning in the visible and near infrared spectral ranges were numerically investigated. The phase-matching configurations with a pump wavelength of 520 nm that provide the largest effective nonlinearity in each crystal were considered and compared. In addition, dispersive characteristics, including the group velocity mismatch and group velocity dispersion, which are of significant importance in femtosecond OPOs, were calculated. Finally, the attainable gain bandwidths for each crystal were estimated.

  1. Optical, spectral and phase-matching properties of BIBO, BBO and LBO crystals for optical parametric oscillation in the visible and near-infrared wavelength ranges

    International Nuclear Information System (INIS)

    The phase-matching properties of BIBO, BBO and LBO crystals for optical parametric oscillators (OPO) with wavelength tuning in the visible and near infrared spectral ranges were numerically investigated. The phase-matching configurations with a pump wavelength of 520 nm that provide the largest effective nonlinearity in each crystal were considered and compared. In addition, dispersive characteristics, including the group velocity mismatch and group velocity dispersion, which are of significant importance in femtosecond OPOs, were calculated. Finally, the attainable gain bandwidths for each crystal were estimated. (paper)

  2. Ion-induced effects in GEM and GEM/MHSP gaseous photomultipliers for the UV and the visible spectral range

    International Nuclear Information System (INIS)

    We report on the progress in the study of cascaded GEM and GEM/MHSP gas avalanche photomultipliers operating at atmospheric pressure, with CsI and bialkali photocathodes. They have single-photon sensitivity, ns time resolution and good localization properties. We summarize operational aspects and results, with the highlight of a high-gain stable gated operation of a visible-light device. Of particular importance are the results of a recent ion-backflow reduction study in different cascaded multipliers, affecting the detector's stability and the photocathode's lifetime. We report on the significant progress in ion-blocking and provide first results on bialkali-photocathode aging under gas multiplication

  3. 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)

    Science.gov (United States)

    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 comparing the results from different spatial resolutions (7.5 x 7.5 km2, 5 x 5 km2, 2.5 x 7.5 km2, 1.25 x 3.75 km2). In addition, improved methodology to obtain aerosol products using hyper-spectral UV-VIS measurements is discussed.

  4. Spectral Aerosol Extinction (SpEx): a new instrument for in situ ambient aerosol extinction measurements across the UV/visible wavelength range

    Science.gov (United States)

    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, E. L.; Ziemba, L. D.

    2015-06-01

    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 (PSLs) 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. Extinction spectra obtained with SpEx contain more information than can be conveyed by a simple power law fit (typically represented by Ångström Exponents). Planned future improvements aim to lower detection limits and ruggedize the instrument for mobile operation.

  5. An Impurity Emission Survey in the near UV and Visible Spectral Ranges of Electron Cyclotron Heated (ECH) Plasma in the TJ-II Stellarator

    International Nuclear Information System (INIS)

    We report on a near-ultraviolet and visible spectroscopic survey (220-600 nm) of electron cyclotron resonance (ECR) heated plasmas created in the TJ-II stellarator, with central electron temperatures up to 2 keV and central electron densities up to 1.7 x 10 ''19 m''-3. Approximately 1200 lines from thirteen elements have been identified. The purpose of the work is to identify the principal impurities and spectral lines present in TJ-II plasmas, as well as their possible origin to search for transitions from highly ionised ions. This work will act as a base for identifying suitable transitions for following the evolution of impurities under different operating regimens and multiplet systems for line polarisation studies. It is intended to use the database creates as a spectral line reference for comparing spectra under different operating and plasma heating regimes. (Author)

  6. Properties of InGaAlAs/AlGaAs quantum dots for single photon emission in the near infrared and visible spectral range

    International Nuclear Information System (INIS)

    We have carried out a detailed characterization of individual self-assembled InGaAlAs/AlGaAs quantum dots grown on GaAs substrate and emitting in the 680–780 nm spectral range. Exciton, biexciton and charged exciton emission lines originating from the same quantum dot have been identified, and the biexciton and charged exciton binding energies have been derived to be equal ? 5 and ? 9 meV, respectively. The second-order photon correlation experiments allowed us to show a clear antibunching for exciton emission with a value of g(2)(0) = 0.04±0.02, confirming distinctly that such GaAs-based quantum dots can be considered as single photon quantum emitters in the abovementioned wavelength range

  7. Directional character of soil surface reflectance in the visible and near-infrared range

    OpenAIRE

    Chmiel, J.; S. Białousz; Verbrugghe, M.; Cierniewski, J.

    1995-01-01

    The paper shows the importance of directional effects on soil reflectance in the visible and near -infrared range. It includes physical principles of surface interactions with radiation in this spectral range, and examples of soil reflectance measurements performed during Polish-French cooperation.

  8. Visibility analysis of point cloud in close range photogrammetry

    Science.gov (United States)

    Alsadik, B.; Gerke, M.; Vosselman, G.

    2014-05-01

    The ongoing development of advanced techniques in photogrammetry, computer vision (CV), robotics and laser scanning to efficiently acquire three dimensional geometric data offer new possibilities for many applications. The output of these techniques in the digital form is often a sparse or dense point cloud describing the 3D shape of an object. Viewing these point clouds in a computerized digital environment holds a difficulty in displaying the visible points of the object from a given viewpoint rather than the hidden points. This visibility problem is a major computer graphics topic and has been solved previously by using different mathematical techniques. However, to our knowledge, there is no study of presenting the different visibility analysis methods of point clouds from a photogrammetric viewpoint. The visibility approaches, which are surface based or voxel based, and the hidden point removal (HPR) will be presented. Three different problems in close range photogrammetry are presented: camera network design, guidance with synthetic images and the gap detection in a point cloud. The latter one introduces also a new concept of gap classification. Every problem utilizes a different visibility technique to show the valuable effect of visibility analysis on the final solution.

  9. Globally integrated measurements of the Earth's visible spectral albedo

    CERN Document Server

    Montanes-Rodriguez, P; Goode, P R; Hickey, J; Koonin, S E

    2005-01-01

    We report spectroscopic observations of the earthshine reflected from the Moon. By applying our photometry methodology to spectroscopy, we were able to precisely determine the Earth's reflectance, and its variation as a function of wavelength through a single night as the Earth rotates. These data imply that planned regular monitoring of earthshine spectra will yield valuable, new inputs for climate models, which would be complementary to those from the more standard broadband measurements of satellite platforms. The mean spectroscopic albedo over the visible is consistent with simultaneous broadband photometric measurements. We found no evidence for an appreciable "red" or "vegetation edge" in the Earth's spectral albedo, and no evidence for changes in this spectral region (700 -740 nm) over the 40 degrees of Earth's rotation covered by our observations.

  10. Multilayer Coatings for UV Spectral Range

    Science.gov (United States)

    Miloushev, Ilko; Tenev, Tihomir; Peyeva, Rumiana; Panajotov, Krassimir

    2010-01-01

    Optical coatings for the UV spectral range play currently a significant role in the modern optical devices. For reducing of manufacturing cost the reliable design is essential. Therefore, better understanding of the optical properties of the used materials is indispensable for the proper design and manufacturing of the multilayer UV coatings. In this work we present some results on the preparation of reflective UV coatings. The implemented materials are magnesium fluoride and lanthanum fluoride. Their optical constants are determined from spectral characteristics of single layers in the 200-800 nm spectral range, obtained by thermal boat evaporation in high vacuum conditions. These results are subsequently used for the analysis of high reflection (HR) stack made of 40 layers deposited by the same deposition process.

  11. Towards isotropic negative magnetics in the visible range

    OpenAIRE

    Simovski, C. R.; Tretyakov, S. A.

    2008-01-01

    The idea of isotropic resonant magnetism in the visible range of frequencies known from precedent publications is developed having in mind achievements of the modern chemistry. Plasmonic colloidal nanoparticles covering a silica core form a cluster with resonant and isotropic magnetic response. Two approximate models giving the qualitative mutual agreement are used to evaluate the magnetic polarizability of the cluster. It is shown that the electrostatic interaction of nanoc...

  12. Brightness Control in Dynamic Range Constrained Visible Light OFDM Systems

    OpenAIRE

    Yu, Z.; Baxley, R. J.; Zhou, G. T.

    2013-01-01

    Visible light communication (VLC) systems can provide illumination and communication simultaneously via light emitting diodes (LEDs). Orthogonal frequency division multiplexing (OFDM) waveforms transmitted in a VLC system will have high peak-to-average power ratios (PAPRs). Since the transmitting LED is dynamic-range limited, OFDM signal has to be scaled and biased to avoid nonlinear distortion. Brightness control is an essential feature for the illumination function. In thi...

  13. Towards isotropic negative magnetics in the visible range

    CERN Document Server

    Simovski, C R

    2008-01-01

    The idea of isotropic resonant magnetism in the visible range of frequencies known from precedent publications is developed having in mind achievements of the modern chemistry. Plasmonic colloidal nanoparticles covering a silica core form a cluster with resonant and isotropic magnetic response. Two approximate models giving the qualitative mutual agreement are used to evaluate the magnetic polarizability of the cluster. It is shown that the electrostatic interaction of nanocolloids decreases the resonant frequency of an individual complex magnetic scatterer (nanocluster) compared to the previously studied variant of a planar circular nanocluster with same size. This means the reduction of the optical size of nanoclusters that presumably allows one to avoid strong spatial dispersion within the frequency range of the negative permeability.

  14. New fractal structures for frequencies close to the visible range

    DEFF Research Database (Denmark)

    Malureanu, Radu; Sandru, A.

    2011-01-01

    In this paper we present a new type of fractal resonator to be used in the red/NIR region of the spectra. The structure presents high-transmission band in 795-825nm range. The stop band is in the 683-731 nm range. Due to the huge difference in the spectra within such a short range, the structure can be used as an efficient sensor, both in transmission as well as in reflection. Thus, a variation of only 0.09 in the refraction index will for example change the structure’s behaviour from 90% reflection to 90% transmission. Such resonances lead to a sensitivity of 780 nm/RIU. Another advantage of this resonator is the independency of the incidence angle - in the spectral re-gion of interest; the incidence angle has very little influence over the response.

  15. Spectral Measurements of Aerosol Absorption from UV to VISIBLE

    Science.gov (United States)

    Krotkov, N. A.; Labow, G.; Herman, J.; Bhartia, P. K.; Slusser, J.; Durham, B.; Janson, G.; Wilson, C.; Disterhoft, P.; Cede, A.; Abuhassan, N.; Eck, T. F.; Holben, B.; Bais, A.; Rapsomanikis, S.

    2007-05-01

    Amount of solar radiation reaching the Earth's surface can be strongly influenced by aerosol absorption. The aerosol absorption optical thickness (AAOT) in the visible and near IR (440 nm- 1020nm) is routinely produced from almucantar measurements made by the CIMEL instruments in the AERONET network. AAOT in the UV (300nm- 368nm) have been derived from the total and diffuse hemispherical flux measurements made by UV- Multifilter Rotating Shadowband Radiometer (UV-MFRSR, Yankee Environmental Systems, Inc.) instruments. However, no direct comparisons between these two methods exist because the CIMEL wavelengths (used in almucantar retrievals) do not overlap with the UV-MFRSR wavelengths. To enable direct comparisons between the two techniques, we have modified our UV-MFRSR, part of USDA UVB Monitoring and Research Network, by replacing standard 300nm filter with 440nm filter used in AERONET network. The instrument has been deployed at Mauna Loa Observatory, at NASA GSFC in Greenbelt, MD (July 2005 - June 2006) and during SCOUT-03 field campaign in Thessaloniki, Greece in July 2006. During these deployments the instrument's calibration was monitored daily using co-located AERONET and BREWER direct sun measurements of aerosol extinction optical thickness (AOT). Between the deployments the instrument was thoroughly calibrated at the NOAA Central UV Calibration Facility in Boulder, Colorado. We find that the UV-MSFRSR instrument is highly susceptible to calibration drifts. However, these drifts can be accurately assessed using AERONET and BREWER direct sun data. After correcting for these calibration changes, the AAOT was inferred by fitting the measurements of global and diffuse atmospheric transmittances with the forward RT model independently at each spectral channel. The AOT data and ancillary measurements of aerosol column particle size distribution and refractive index in the visible wavelengths (by CIMEL sun-sky almucantar inversions), direct -sun column NO2 and ozone (by Brewer mk III spectrometer), surface pressure and albedo constrained the forward radiative transfer model input. Derived AAOT and SSA at 440nm were inter- compared with AERONET almucantar inversions at the same wavelength and with Brewer SSA measurements at 340nm during SCOUT-03 campaign. These measurements constitute the first continuous UV-VIS spectra of AAOT and SSA at two different locations in Maryland, USA and Thessaloniki, Greece.

  16. A spatially scanning vacuum ultraviolet and visible range spectrometer for spectroscopy of tokamak plasmas in ASDEX-Upgrade

    Science.gov (United States)

    Field, A. R.; Fink, J.; Dux, R.; Fussmann, G.; Wenzel, U.; Schumacher, U.

    1995-12-01

    A spatially scanning, combined vacuum-ultraviolet (VUV) and visible range spectrometer system for the spectroscopy of tokamak plasmas in the ASDEX-Upgrade experiment is described. This system is designed to allow flexible observation of about 2/3 of the boundary plasma using VUV (30-200 nm) and visible range spectrometers viewing along a common line of sight which can be scanned during the plasma discharge by means of a rotatable mirror. From successive spectra recorded using intensified, multichannel photodiode detectors and the recorded position data, spatial profiles of the plasma emission can be reconstructed. Because radiation losses from the boundary plasma can largely be attributed to line emission in the VUV spectral region, this instrument finds application in quantitative studies of radiation loss processes as well as to studies of impurity production and transport. Simultaneous observation in the visible spectral range facilitates an in situ absolute calibration of the VUV instrument by means of the ``branching-ratios'' technique.

  17. Silicon photodiode with selective Zr/Si coating for extreme ultraviolet spectral range

    Energy Technology Data Exchange (ETDEWEB)

    Aruev, P N; Barysheva, Mariya M; Ber, B Ya; Zabrodskaya, N V; Zabrodskii, V V; Lopatin, A Ya; Pestov, Alexey E; Petrenko, M V; Polkovnikov, V N; Salashchenko, Nikolai N; Sukhanov, V L; Chkhalo, Nikolai I

    2012-10-31

    The procedure of manufacturing silicon photodiodes with an integrated Zr/Si filter for extreme ultraviolet (EUV) spectral range is developed. A setup for measuring the sensitivity profile of detectors with spatial resolution better than 100 {mu}m is fabricated. The optical properties of silicon photodiodes in the EUV and visible spectral ranges are investigated. Some characteristics of SPD-100UV diodes with Zr/Si coating and without it, as well as of AXUV-100 diodes, are compared. In all types of detectors a narrow region beyond the operating aperture is found to be sensitive to the visible light. (photodetectors)

  18. Passive signatures concealed objects recorded by multispectral and hyperspectral systems in visible, infrared and terahertz range

    Science.gov (United States)

    Kastek, Mariusz; Kowalski, Marcin; Polakowski, Henryk; Lagueux, Philippe; Gagnon, Marc-André

    2014-06-01

    Risks to the safety of public zones (generally available for people) are related mainly to the presence of hidden dangerous objects (such as knives, guns, bombs etc.) and their usage. Modern system for the monitoring of such zones attempt to detect dangerous tools using multispectral cameras working in different spectral ranges: the visible radiation, near, medium and long range infrared and recently also in terahertz range. In order to develop methods and algorithms to detect hidden objects it is necessary to determine the thermal signatures of such objects of interest. The laboratory measurements were conducted to determine the thermal signatures of dangerous tools hidden under various clothes in different ambient conditions. Cameras used for measurements were working in spectral range 0.6-12.5 µm. An infrared imaging Fourier transform spectroradiometer was also used, working in spectral range 7.7-11.7 µm. Analysis of registered thermograms and hyperspectral datacubes has yielded the thermal signatures for: two types of guns, two types of knives and home-made explosive bombs. The determined thermal signatures will be used in the development of method and algorithms of image analysis implemented in proposed monitoring systems.

  19. Ultraviolet and visible range plasmonics of a topological insulator

    CERN Document Server

    Ou, Jun-Yu; Adamo, Giorgio; Sulaev, Azat; Wang, Lan; Zheludev, Nikolay I

    2014-01-01

    The development of metamaterials, data processing circuits and sensors for the visible and UV parts of the spectrum is hampered by the lack of low-loss media supporting plasmonic excitations and drives the intense search for plasmonic materials beyond noble metals. By studying plasmonic nanostructures fabricated on the surface of topological insulator $\\mbox{Bi}_{1.5}\\mbox{Sb}_{0.5}\\mbox{Te}_{1.8}\\mbox{Se}_{1.2}$ we found that it is orders of magnitude better plasmonic material than gold and silver in the blue-UV range. Metamaterial fabricated from $\\mbox{Bi}_{1.5}\\mbox{Sb}_{0.5}\\mbox{Te}_{1.8}\\mbox{Se}_{1.2}$ show plasmonic resonances from 350 nm to 550 nm while surface gratings exhibit cathodoluminescent peaks from 230 nm to 1050 nm. The negative permittivity underpinning plasmonic response is attributed to the combination of bulk interband transitions and surface contribution of the topologically protected states. The importance of our result is in the identification of new mechanisms of negative permittiv...

  20. Visible spectral power emitted from a laser produced uranium plasma

    Science.gov (United States)

    Williams, M. D.; Jalufka, N. W.

    1975-01-01

    The development of plasma-core nuclear reactors for advanced terrestrial and space-power sources is researched. Experimental measurements of the intensity and the spectral distribution of radiation from a nonfissioning uranium plasma are reported.

  1. Linear refractive index and absorption measurements of nonlinear optical liquids in the visible and near-infrared spectral region

    OpenAIRE

    Kedenburg, Stefan; Vieweg, Marius; Gissibl, Timo; Giessen, Harald

    2012-01-01

    Liquid-filled photonic crystal fibers and optofluidic devices require infiltration with a variety of liquids whose linear optical properties are still not well known over a broad spectral range, particularly in the near infrared. Hence, dispersion and absorption properties in the visible and near-infrared wavelength region have been determined for distilled water, heavy water, chloroform, carbon tetrachloride, toluene, ethanol, carbon disulfide, and nitrobenzene at a temperature of 20 °C. For...

  2. Diamagnetic nature of stratified thin metals in visible range

    OpenAIRE

    Iwanaga, Masanobu

    2007-01-01

    It is numerically demonstrated that effectively strong diamagnetic resonance emerges at visible frequencies in stratified metal-dielectric metamaterials. The effective optical constants are extracted by two-complex reflectivity method. It is clarified that the effective diamagnetic response originates from local diamagnetism at stratified thin metals. The effective diamagnetism is crucially sensitive to the sturucture of unitcell. The effective diamagnetic response is always...

  3. Quantum yields of the photodissociation of HbO2 in the visible and near IR spectral region

    Science.gov (United States)

    Mamilov, S. A.; Esman, S. S.; Asimov, M. M.; Gisbrecht, A. I.

    2015-01-01

    The efficiency of the laser radiation effect on the oxyhemoglobin in blood vessels and its dependence on the wavelength of the irradiation are investigated. In vivo experimental measurements of the quantum yield of the laser-induced photodissociation of oxyhemoglobin in cutaneous blood vessels in the visible spectral range are presented. The spectral effectiveness of the photodissociation approximately correlates with their absorption spectrum and the transmission spectrum of skin tissue. Different aspects of biomedical application of this phenomenon are discussed. Non-invasive three-wavelength technique for determination of oxyhemoglobin concentrations in blood is also developed.

  4. LASERS: High-power visible-range parametric oscillators

    Science.gov (United States)

    Begishev, I. A.; Gulamov, A. A.; Kamalov, Sh R.; Usmanov, T.; Khadzhaev, A. D.

    1995-11-01

    An investigation was made of superluminescent optical parametric oscillators generating visible light when ADP and KDP crystals were pumped with the third and fourth harmonics of a neodymium laser. The conversion efficiency was 70% and the output energy in the form of parametric waves was 0.35 J. The advantages of the third harmonic of a neodymium laser as the pump radiation, over the fourth harmonic, were demonstrated.

  5. Temperature and salinity correction coefficients for light absorption by water in the visible to infrared spectral region.

    Science.gov (United States)

    Röttgers, Rüdiger; McKee, David; Utschig, Christian

    2014-10-20

    The light absorption coefficient of water is dependent on temperature and concentration of ions, i.e. the salinity in seawater. Accurate knowledge of the water absorption coefficient, a, and/or its temperature and salinity correction coefficients, ?(T) and ?(S), respectively, is essential for a wide range of optical applications. Values are available from published data only at specific narrow wavelength ranges or at single wavelengths in the visible and infrared regions. ?(T) and ?(S) were therefore spectrophotometrically measured throughout the visible, near, and short wavelength infrared spectral region (400 to ~2700 nm). Additionally, they were derived from more precise measurements with a point-source integrating-cavity absorption meter (PSICAM) for 400 to 700 nm. When combined with earlier measurements from the literature in the range of 2600 - 14000 nm (wavenumber: 3800 - 700 cm(-1)), the coefficients are provided for 400 to 14000 nm (wavenumber: 25000 to 700 cm(-1)). PMID:25401542

  6. The electron storage ring BESSY II as a primary source standard from the visible to the X-ray range

    International Nuclear Information System (INIS)

    The Physikalisch-Technische Bundesanstalt (PTB) has used the BESSY 1 800 MeV electron storage ring as a primary source standard since 1984. The calculable spectral photon flux ?E of a bending magnet with relative uncertainties of 4 x 10-4 to 4 x 10-3 for the photon energy range 1 eV to 15 keV was used in a broad spectral range from the visible to the soft X-ray range for the calibration of radiation sources and energy-dispersive X-ray detectors. In 1998, BESSY II was brought into operation. Owing to its higher electron energy, of 1.7 GeV, the useful spectral range could be extended significantly into the X-ray region up to a photon energy of about 50 keV, while special storage-ring operation at 900 MeV results in a spectrum up to about 7 keV. The PTB has established BESSY II as a European primary source standard from the visible to the X-ray range by setting up equipment for the measurement of all storage-ring parameters and geometrical quantities involved in the calcination of ?E according to Schwinger. At BESSY II, ?E from a bending magnet can be calculated with a relative standard uncertainty of 3 x 10-4 for photon energies below 3 keV, rising to 2 x 10-3 at 50 keV. (authors)

  7. Spectral broadening and self-compression of negatively chirped visible femtosecond pulses in fused silica

    International Nuclear Information System (INIS)

    This paper describes a new effect: spectral broadening and self-compression of negatively chirped visible femtosecond pulses as a result of nonlinear interaction of large-aperture beams with fused silica. We assume that the likely mechanism of the observed spectral broadening is the combined effect of self-phase modulation and four-wave mixing. (special issue devoted to the 90th anniversary of n.g. basov)

  8. Studying soil properties using visible and near infrared spectral analysis

    Science.gov (United States)

    Moretti, S.; Garfagnoli, F.; Innocenti, L.; Chiarantini, L.

    2009-04-01

    This research is carried out inside the DIGISOIL Project, whose purposes are the integration and improvement of in situ and proximal measurement technologies, for the assessment of soil properties and soil degradation indicators, going form the sensing technologies to their integration and their application in digital soil mapping. The study area is located in the Virginio river basin, about 30 km south of Firenze, in the Chianti area, where soils with agricultural suitability have a high economic value connected to the production of internationally famous wines and olive oils. The most common soil threats, such as erosion and landslide, may determine huge economic losses, which must be considered in farming management practices. This basin has a length of about 23 km for a basin area of around 60,3 Km2. Geological formations outcropping in the area are Pliocene to Pleistocene marine and lacustrine sediments in beds with almost horizontal bedding. Vineyards, olive groves and annual crops are the main types of land use. A typical Mediterranean climate prevails with a dry summer followed by intense and sometimes prolonged rainfall in autumn, decreasing in winter. In this study, three types of VNIR and SWIR techniques, operating at different scales and in different environments (laboratory spectroscopy, portable field spectroscopy) are integrated to rapidly quantify various soil characteristics, in order to acquire data for assessing the risk of occurrence for typically agricultural practice-related soil threats (swelling, compaction, erosion, landslides, organic matter decline, ect.) and to collect ground data in order to build up a spectral library to be used in image analysis from air-borne and satellite sensors. Difficulties encountered in imaging spectroscopy, such as influence of measurements conditions, atmospheric attenuation, scene dependency and sampling representation are investigated and mathematical pre-treatments, using proper algorithms, are applied and tested. Data on detection limits of ground-based, airborne and satellite sensors are also provided. The problem of the influence of soil moisture and soil roughness on reflectance is also examined. Spectral indexes, derived from absorption features, are related to laboratory results on clay minerals, carbonate and iron content, soil moisture and organic matter amount, in order to investigate the potential of hyperspectral sensors to estimate soil properties, using empirical prediction models.

  9. Studies of the ECR plasma in the visible light range

    International Nuclear Information System (INIS)

    High resolution visible light (VL) plasma photographs were taken at the ATOMKI-ECRIS by an 8 mega-pixel digital camera. Plasmas were generated from gases of He, methane, N, O, Ne, Ar, Kr, Xe and from their mixtures. The analysis of the photo series gave many qualitative and numerous valuable physical information on the nature of ECR plasmas. VL photos convey information mainly on the cold electron component of the plasma. Cold electrons are confined in the central part of the plasma. It is a further challenging task to understand the colors of this special type of plasmas. The colors can be determined by the VL electron transitions of the plasma atoms and ions combined with the human eye sensitivity. There is a good visual agreement between the calculated normalized color and the real color of the plasmas. Through the examples of He and Xe we analyze the physical processes which affect the characteristic colors of these plasmas. The paper is followed by the slides of the presentation. (authors)

  10. A spatially scanning vacuum ultraviolet and visible range spectrometer for spectroscopy of tokamak plasmas in ASDEX-Upgrade

    International Nuclear Information System (INIS)

    A spatially scanning, combined vacuum-ultraviolet (VUV) and visible range spectrometer system for the spectroscopy of tokamak plasmas in the ASDEX-Upgrade experiment is described. This system is designed to allow flexible observation of about 2/3 of the boundary plasma using VUV (30--200 nm) and visible range spectrometers viewing along a common line of sight which can be scanned during the plasma discharge by means of a rotatable mirror. From successive spectra recorded using intensified, multichannel photodiode detectors and the recorded position data, spatial profiles of the plasma emission can be reconstructed. Because radiation losses from the boundary plasma can largely be attributed to line emission in the VUV spectral region, this instrument finds application in quantitative studies of radiation loss processes as well as to studies of impurity production and transport. Simultaneous observation in the visible spectral range facilitates an in situ absolute calibration of the VUV instrument by means of the ''branching-ratios'' technique. copyright 1995 American Institute of Physics

  11. Composition, Mineralogy, and Porosity of Multiple Asteroid Systems from Visible and Near-infrared Spectral Data

    OpenAIRE

    Lindsay, Sean S.; Marchis, Franck; Emery, Joshua P.; Enriquez, J. Emilio; Assafin, Marcelo

    2014-01-01

    We provide a taxonomic and compositional characterization of Multiple Asteroid Systems (MASs) located in the main belt (MB) using visible and near-infrared (0.45-2.5 um) spectral data of 42 MB MASs. The mineralogical analysis is applied to determine meteorite analogs for the MASs, which, in turn, are applied to the MAS density measurements of Marchis et al. (2012) to estimate the system porosity. The macroporosities are used to evaluate the primary MAS formation hypotheses. ...

  12. Short range correlations and spectral functions in asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Dynamical correlations in asymmetric infinite nuclear matter are investigated in a transport theoretical approach. Self-energies due to short range correlations and their influence on the nucleon spectral functions are described in an approach accounting for a realistic treatment of mean-field dynamics and a self-consistently derived quasiparticle interaction. Landau-Migdal theory is used to derived the short range interaction from a phenomenological Skyrme energy density functional. The spectral functions in asymmetric nuclear matter are found to follow in their gross features closely the patterns observed previously in symmetric nuclear matter. An interesting sensitivity of dynamical self-energies and spectral functions on the momentum structure of the underlying interactions is found

  13. Composition, mineralogy, and porosity of multiple asteroid systems from visible and near-infrared spectral data

    Science.gov (United States)

    Lindsay, S. S.; Marchis, F.; Emery, J. P.; Enriquez, J. E.; Assafin, M.

    2015-02-01

    We aim to provide a taxonomic and compositional characterization of Multiple Asteroid Systems (MASs) located in the main belt (MB) using visible (0.45-0.85 ?m) and near-infrared (0.7-2.5 ?m) spectral data of 42 MB MASs. The compositional and mineralogical analysis is applied to determine meteorite analogs for the MASs, which, in turn, are applied to the MAS density measurements of Marchis et al. (Marchis et al. [2012]. Icarus 221, 1130-1161) to estimate the porosity of the systems. The macroporosities are used to evaluate the primary MAS formation hypotheses. Our spectral survey consists of visible and near-infrared spectral data. The visible observing campaign includes 25 MASs obtained using the Southern Astrophysical Research (SOAR) telescope with the Goodman High Throughput Spectrometer. The infrared observing campaign includes 34 MASs obtained using the NASA Infrared Telescope Facility (IRTF) with the SpeX spectragraph. For completeness, both visible and NIR data sets are supplemented with publicly available data, and the data sets are combined where possible. The MASs are classified using the Bus-DeMeo taxonomic system. In order to determine mineralogy and meteorite analog, we perform a NIR spectral band parameter analysis using a new analysis routine, the Spectral Analysis Routine for Asteroids (SARA). The SARA routine determines band centers, areas, and depths by utilizing the diagnostic absorption features near 1- and 2-?m due to Fe2+ crystal field transitions in olivine + pyroxene and pyroxene, respectively. The band parameter analysis provides the Gaffey subtype for the S-complex MASs; the relative abundance olivine-to-pyroxene ratio; and olivine and pyroxene modal abundances for S-complex and V-type MASs. This mineralogical information is then applied to determine meteorite analogs. Through applying calibration studies, we are able to determine the H, L, and LL meteorite analogs for 15 MASs with ordinary chondrite-like (OC) mineralogies. We observe an excess (10/15) of LL-like mineralogies. Of the ten MASs with LL-like mineralogies, seven are consistent with Flora family membership, supporting the hypothesis that the Flora family is a source of LL-like NEAs and LL chondrites on Earth. Our band parameter analysis is unable to clearly distinguish between the HED subgroups for the 6 V-type MASs. Using the measured densities of the meteorite analog and the MAS densities from Marchis et al. (Marchis et al. [2012]. Icarus 221, 1130-1161), we estimate the macroporosity for 13 MASs. We find that all of the MASs with estimated macroporosities are in agreement with formation hypotheses.

  14. Composition, Mineralogy, and Porosity of Multiple Asteroid Systems from Visible and Near-infrared Spectral Data

    CERN Document Server

    Lindsay, Sean S; Emery, Joshua P; Enriquez, J Emilio; Assafin, Marcelo

    2014-01-01

    We provide a taxonomic and compositional characterization of Multiple Asteroid Systems (MASs) located in the main belt (MB) using visible and near-infrared (0.45-2.5 um) spectral data of 42 MB MASs. The mineralogical analysis is applied to determine meteorite analogs for the MASs, which, in turn, are applied to the MAS density measurements of Marchis et al. (2012) to estimate the system porosity. The macroporosities are used to evaluate the primary MAS formation hypotheses. The visible observing campaign includes 25 MASs obtained using the SOAR telescope with the Goodman High Throughput Spectrometer. The infrared observing campaign includes 34 MASs obtained using the NASA IRTF with the SpeX spectragraph. The MASs are classified using the Bus-DeMeo taxonomic system. We perform a NIR spectral band parameter analysis using a new analysis routine, the Spectral Analysis Routine for Asteroids (SARA). The SARA routine determines band centers, areas, and depths by utilizing the diagnostic absorption features near 1- ...

  15. High-sensitivity high-stability silicon photodiodes for DUV, VUV and EUV spectral ranges:

    OpenAIRE

    L. Shi; Nihtianov, S.; Scholze, F.; Gottwald, A.; Nanver, L. K.

    2011-01-01

    In this paper, the optical and electrical performance of a newly developed silicon photodiode based on pure boron CVD technology (PureB-diodes) is introduced. Due to their extremely shallow p-n junction, with the depletion zone starting only a few nanometers below the surf ce, and nm-thin pure-boron-layer coverage of the anode surface, PureB-diodes have so far demonstrated the highest reported spectral responsivity in all sub-visible ultraviolet (UV) ranges: DUV (deep ultraviolet), VUV (vacuu...

  16. The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements

    OpenAIRE

    W. Gurlit; Bösch, H.; Bovensmann, H.; Burrows, J. P.; Butz, A; Camy-peyret, C.; Dorf, M; Gerilowski, K.; Lindner, A.; Noël, S.; Platt, U.; Weidner, F.; Pfeilsticker, K.

    2004-01-01

    Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7–418 nm and the visible from 400–652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively) from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh...

  17. An Approach for Identifying of Fusarium Infected Maize Grains by Spectral Analysis in the Visible and Near Infrared Region, SIMCA Models, Parametric and Neural Classifiers

    OpenAIRE

    Tsvetelina Draganova; Plamen Daskalov; Rusin Tsonev

    2010-01-01

    An approach for identifying of Fusarium infected single maize grains based on diffuse reflectance in visible and near infrared region is proposed in the paper. Spectral characteristics were collected in the range 400-2500 nm in steps of 2 nm. Soft independent modeling of class analogy (SIMCA) is used for data processing. Maize grains classification is based on SIMCA classifier and Probabilistic neural network (PNN). Recognition accuracy which is achieved for both classes of grains is respecti...

  18. Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols

    OpenAIRE

    Lund Myhre, C. E.; Nielsen, C. J.

    2004-01-01

    Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentra...

  19. Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.

    Science.gov (United States)

    Lee, Hong-Shik; Kim, Haeng-In; Lee, Sang-Shin

    2012-06-10

    A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (?(1)=905 nm) and visible (?(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm. PMID:22695673

  20. Optical Properties of Sodium Chloride Solution Within the Spectral Range from 300 to 2500 nm at Room Temperature.

    Science.gov (United States)

    Li, Xingcan; Liu, Linhua; Zhao, Junming; Tan, Jianyu

    2015-05-01

    The optical properties of sodium chloride (NaCl) solution were experimentally determined by double optical pathlength transmission method in the spectral range from 300 to 2500 nm at the NaCl concentration range from 0 to 360 g/L. The results show that the refractive index of NaCl solution increases with NaCl concentrations and correlates nonlinearly with the concentration of NaCl solution. The absorption index of NaCl solution increases with NaCl concentrations in the visible spectral range of 300-700 nm, but varies little in the near-infrared spectral range of 700-2500 nm at room temperature. For the sake of applications, the fitted formulae of the refractive index and absorption index of NaCl solution as a function of wavelength and NaCl concentration are presented. PMID:25909772

  1. Investigation of oxygen impurity transport using the O4+ visible spectral line in the Aditya tokamak

    Science.gov (United States)

    Chowdhuri, M. B.; Ghosh, J.; Banerjee, S.; Dey, Ritu; Manchanda, R.; Kumar, Vinay; Vasu, P.; Patel, K. M.; Atrey, P. K.; Shankara Joisa, Y.; Rao, C. V. S.; Tanna, R. L.; Raju, D.; Chattopadhyay, P. K.; Jha, R.; Gupta, C. N.; Bhatt, S. B.; Saxena, Y. C.; the Aditya Team

    2013-02-01

    Intense visible lines from Be-like oxygen impurity are routinely observed in the Aditya tokamak. The spatial profile of brightness of a Be-like oxygen spectral line (2p3p 3D3-2p3d 3F4) at 650.024 nm is used to investigate oxygen impurity transport in typical discharges of the Aditya tokamak. A 1.0 m multi-track spectrometer (Czerny-Turner) capable of simultaneous measurements from eight lines of sight is used to obtain the radial profile of brightness of O4+ spectral emission. The emissivity profile of O4+ spectral emission is obtained from the spatial profile of brightness using an Abel-like matrix inversion. The oxygen transport coefficients are determined by reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional empirical impurity transport code, STRAHL. Much higher values of the diffusion coefficient compared with the neo-classical values are observed in both the high magnetic field edge region (D_inboard^{\\max}\\sim 30\\,m^{2}\\,s^{-1}) and the low magnetic field edge region (D_outboard^{\\max}\\sim 45\\,m^{2}\\,s^{-1}) of typical Aditya ohmic plasmas, which seems to be due to fluctuation-induced transport. The diffusion coefficient at the limiter radius in the low-field (outboard) region is typically ˜ twice as high as that at the limiter radius in the high-field (inboard) region.

  2. Experimental Demonstration of Non-Resonant Hyperlens in the Visible Range

    CERN Document Server

    Sun, Jingbo; Litchinitser, Natalia M

    2014-01-01

    A metamaterial hyperlens offers a unique solution to overcome the diffraction limit by transforming evanescent waves responsible for imaging subwavelength features of an object into propagating waves. However, the first realizations of optical hyperlenses were limited by a narrow working bandwidth and significant resonance-induced loss. Here, we report the first experimental demonstration of a non-resonant waveguide-coupled hyperlens operating in the visible wavelength range. A detailed investigation of various materials systems proves that a radial fan-shaped configuration is superior to the concentric layer-based configuration in that it relies on non-resonant negative dielectric response, and, as a result, enables broadband and low-loss performance in the visible range.

  3. High-order harmonic generation in a narrow spectral range

    International Nuclear Information System (INIS)

    It is proposed to use the two-component pumping of atoms by a strong low-frequency field and a high-frequency ultrashort pulse for the generation of high-order harmonics. For a fixed relative phase of the pumping fields, high-order harmonics are generated in a rather narrow spectral range. The interaction of atoms with the two-component field also determines the limiting efficiency of high-order harmonic generation. The effect can be reversed for the enhancement of high-order harmonics by using additional high-frequency pump radiation. (nonlinear optical phenomena)

  4. Design of a portable large spectral range grazing incidence instrument

    International Nuclear Information System (INIS)

    A design of a small size grazing incidence instrument is presented, which offers large spectral range and high resolution without sacrificing luminosity. The instrument is particularly suited for use at synchrotron radiation sources since it can be conveniently attached to existing experiment chambers. The basic idea of the design is the use of fixed mounted gratings of different radii and groove densities and a big two-dimensional position sensitive detector mounted on a x-y angle table. The design is discussed in some detail and performance is presented. (orig.)

  5. Visible and near-infrared spectral signatures for adulteration assessment of extra virgin olive oil

    Science.gov (United States)

    Mignani, A. G.; Ciaccheri, L.; Ottevaere, H.; Thienpont, H.; Conte, L.; Marega, M.; Cichelli, A.; Attilio, C.; Cimato, A.

    2010-04-01

    Because of its high price, the extra virgin olive oil is frequently target for adulteration with lower quality oils. This paper presents an innovative optical technique capable of quantifying the adulteration of extra virgin olive oil caused by lowergrade olive oils. It relies on spectral fingerprinting the test liquid by means of diffuse-light absorption spectroscopy carried out by optical fiber technology in the wide 400-1700 nm spectral range. Then, a smart multivariate processing of spectroscopic data is applied for immediate prediction of adulterant concentration.

  6. Attosecond broadband multilayer mirrors for the water window spectral range

    Science.gov (United States)

    Guggenmos, A.; Radünz, S.; Rauhut, R.; Hofstetter, M.; Venkatesan, S.; Wochnik, A.; Scheu, C.; Gullikson, E.; Fischer, S.; Nickel, B.; Kleineberg, U.

    2014-09-01

    Recent advances in the development of attosecond soft X-ray sources ranging into the `water window' spectral range, between the carbon 1s and oxygen 1s states (284 eV - 543 eV), are also driving the development of suited broadband multilayer optics for attosecond beam steering and dispersion management. The relatively low intensity of current High Harmonic Generation (HHG) soft X-ray sources calls for an efficient use of photons, thus the development of low-loss multilayer optics is of uttermost importance. Here, we report about the realization of atomically smooth interfaces in broadband CrSc multilayer mirrors by an optimized ion beam deposition and assisted interface polishing process.

  7. Micro- and nanophotonic structures in the visible and near infrared spectral region for optical devices

    Science.gov (United States)

    Pham, Van Hoi; Bui, Huy; Van Nguyen, Thuy; Nguyen, The Anh; Son Pham, Thanh; Cam Hoang, Thi Hong; Ngo, Quang Minh

    2013-06-01

    In this paper we present some research results on the micro and nano-photonic structures in the visible and near infrared spectral region for optical devices that have been done within the framework of Nanoscience and Nanotechnology Program of Institute of Materials Science. In the first part, we report the design and fabrication of 1D photonic structure based on porous silicon layers fabricated by electrochemical etching method and some of their potential applications such as optical filters, microcavity and optical sensors for distinguishing the content of bio-gasoline. In addition, we demonstrate some results on preparation of the 2D and 3D nanophotonic structures based on silica opal layers prepared by sol–gel and self-assembled methods. In the second part, we demonstrate the results of lasing emissions of erbium ions in the visible and near infrared zone from microcavity. The observation of emission of single-mode green light at the wavelength of 537 nm from erbium ions in the microcavity is interesting for the study of atom–photon interaction phenomenon. In the last part, we will show some new results of design and fabrication of nanocomposite based on nanoscale TiO2 and/or ZnO and nanoparticles of semiconductors and metals, which are oriented to the fabrication of energy conversion and photo-reactor devices. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2012, 30 October–2 November, 2012, Ha Long, Vietnam.

  8. Micro- and nanophotonic structures in the visible and near infrared spectral region for optical devices

    International Nuclear Information System (INIS)

    In this paper we present some research results on the micro and nano-photonic structures in the visible and near infrared spectral region for optical devices that have been done within the framework of Nanoscience and Nanotechnology Program of Institute of Materials Science. In the first part, we report the design and fabrication of 1D photonic structure based on porous silicon layers fabricated by electrochemical etching method and some of their potential applications such as optical filters, microcavity and optical sensors for distinguishing the content of bio-gasoline. In addition, we demonstrate some results on preparation of the 2D and 3D nanophotonic structures based on silica opal layers prepared by sol–gel and self-assembled methods. In the second part, we demonstrate the results of lasing emissions of erbium ions in the visible and near infrared zone from microcavity. The observation of emission of single-mode green light at the wavelength of 537 nm from erbium ions in the microcavity is interesting for the study of atom–photon interaction phenomenon. In the last part, we will show some new results of design and fabrication of nanocomposite based on nanoscale TiO2 and/or ZnO and nanoparticles of semiconductors and metals, which are oriented to the fabrication of energy conversion and photo-reactor devices. (review)

  9. Infrared Spectroscopy with Visible Light

    CERN Document Server

    Kalashnikov, Dmitry A; Kulik, Sergei P; Krivitsky, Leonid A

    2015-01-01

    Spectral measurements in the infrared (IR) optical range provide unique fingerprints of materials which are useful for material analysis, environmental sensing, and health diagnostics. Current IR spectroscopy techniques require the use of optical equipment suited for operation in the IR range, which faces challenges of inferior performance and high cost. Here we develop a spectroscopy technique, which allows spectral measurements in the IR range using visible spectral range components. The technique is based on nonlinear interference of infrared and visible photons, produced via Spontaneous Parametric Down Conversion (SPDC). The intensity interference pattern for a visible photon depends on the phase of an IR photon, which travels through the media. This allows determining properties of the media in the IR range from the measurements of visible photons. The technique can substitute and/or complement conventional IR spectroscopy techniques, as it uses well-developed optical components for the visible range.

  10. Method for detection and imaging over a broad spectral range

    Science.gov (United States)

    Yefremenko, Volodymyr (Westmont, IL); Gordiyenko, Eduard (Westmont, IL); Pishko, legal representative, Olga (Kharkov, UA); Novosad, Valentyn (Chicago, IL); Pishko, deceased; Vitalii (Westmont, IL)

    2007-09-25

    A method of controlling the coordinate sensitivity in a superconducting microbolometer employs localized light, heating or magnetic field effects to form normal or mixed state regions on a superconducting film and to control the spatial location. Electron beam lithography and wet chemical etching were applied as pattern transfer processes in epitaxial Y--Ba--Cu--O films. Two different sensor designs were tested: (i) a 3 millimeter long and 40 micrometer wide stripe and (ii) a 1.25 millimeters long, and 50 micron wide meandering-like structure. Scanning the laser beam along the stripe leads to physical displacement of the sensitive area, and, therefore, may be used as a basis for imaging over a broad spectral range. Forming the superconducting film as a meandering structure provides the equivalent of a two-dimensional detector array. Advantages of this approach are simplicity of detector fabrication, and simplicity of the read-out process requiring only two electrical terminals.

  11. The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements

    Directory of Open Access Journals (Sweden)

    W. Gurlit

    2004-12-01

    Full Text Available Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7–418 nm and the visible from 400–652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3, and NO2, the measured solar spectra are compared with previous observations. Our solar irradiance is +1.6% larger than the re-calibrated Kurucz et al. (1984 solar spectrum (Fontenla et al., 1999, called MODTRAN 3.5 in the visible spectral range (435–650 nm, +1.5% larger in the (370–415 nm wavelength interval, but ?4% smaller in the UV spectral range (316.7–370 nm, when the Kurucz spectrum is convolved to the spectral resolution of our instrument. The same comparison with the SOLSPEC solar spectrum (Thuillier et al., 1997, 1998a, b confirms the somewhat larger solar irradiance (+1.7% measured by the balloon instrument from 435–500 nm, but not from 500–650 nm, where the SOLSPEC is ?1.3% lower than MODTRAN 3.5. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (– re-calibrated by the University of Bremen – with MODTRAN 3.5 indicates an agreement of +0.2% in the visible spectral range (435–585 nm. With this calibration, the SCIAMACHY solar spectrum is congruent with the balloon observations (?1% in the 316.7–370 nm wavelength range, but both are up to ?5%/?3% smaller than MODTRAN 3.5 and SOLSPEC, respectively. In agreement with findings of Skupin et al. (2002 our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.

  12. From the infrared to the visible range: Spectroscopic studies of ytterbium doped oxyborates

    OpenAIRE

    Jubera, Ve?ronique; Sablayrolles, Jean; Guillen, Franc?ois; Decourt, Rodolphe; Couzi, Michel; Garcia, Alain

    2009-01-01

    The spectroscopic study of yttrium oxyborates doped with trivalent ytterbium is conducted in the UV-Visible and infrared range. The multiplicity of the ytterbium environments in the studied compounds leads to complex emission spectra in the infrared and excitation spectra in the ultraviolet. Different 2F5/2 and 2F7/2 transitions have been pointed out. The emission extends up to 1090 nm for one compound. A correlation was evidenced between position and de-excitation mode of a charge transfer b...

  13. [The effect of spectral range on the measurement of ozone in the atmosphere by DOAS].

    Science.gov (United States)

    Fu, Qiang; Peng, Fu-Min; Liu, Wen-Qing; Xie, Pin-Hua; Luo, Tao; Si, Fu-Qi; Li, Su-Wen

    2009-08-01

    Ozone (O3) often serves as the benchmark for the overall pollution level of a given airshed and it is critical that the measurement technique be accurate and precise, In the DOAS measurement, the accuracy of O3 concentration is determined by the selected spectral range. The present paper focuses on the effect of spectral range on the detected characteristic absorption structure of O3, and the variation of differential cross section of O3 with the change in spectral range and the source of interference in different spectral range. The effect of practical atmospheric light extinction on the light intensities of different spectral ranges was deduced; the effect of spectral range on the accuracy was determined by detecting the standard gases at different concentration and different spectral resolution. The optimized spectral range was determined for O3, which can yield high sensitivity, good selectivity and a reasonable time resolution for the accurate qualitative and quantitative analysis of O3. PMID:19839323

  14. Blackbody radiation sources for the IR spectral range

    Science.gov (United States)

    Ogarev, S. A.; Morozova, S. P.; Katysheva, A. A.; Lisiansky, B. E.; Samoylov, M. L.

    2013-09-01

    Metrological radiometric facilities for optoelectronic instruments calibration utilize in terms of standards as radiation detectors in a form of cryogenic radiometers (CR), so as radiation sources. However in practice, there are no CR working within IR spectral range. An alternative way of radiometric calibration in middle and far IR ranges is to develop a parametric series of standard radiation sources - blackbody (BB) models. The paper describes some of BBs developed at VNIIOFI for the last time [1] from cryogenic (80 K to 200 K), to low (about 200 K to 400 K) and medium (400 K to 700 K) temperature regions for calibration of the IR instruments under cryogenic-vacuum conditions. These BBs are presented by models of both types: variable-temperature and based on fixed points of Ga or In. BBs are characterized with high temperature uniformity and stability. Copper and aluminum alloys are used as the radiation cavity materials. The required value of emissivity ?? is achieved by using different black coatings. Low-temperature and cryogenic BBs are based on the principles of indirect multi-zone electric heating (with heat isolation from LN2 cooling loop, or by using an external liquid thermostat with circulating heat-transfer agent. The principles of operation, design and test results of BBs are described.

  15. Blackbody radiation sources for the IR spectral range

    International Nuclear Information System (INIS)

    Metrological radiometric facilities for optoelectronic instruments calibration utilize in terms of standards as radiation detectors in a form of cryogenic radiometers (CR), so as radiation sources. However in practice, there are no CR working within IR spectral range. An alternative way of radiometric calibration in middle and far IR ranges is to develop a parametric series of standard radiation sources - blackbody (BB) models. The paper describes some of BBs developed at VNIIOFI for the last time [1] from cryogenic (80 K to 200 K), to low (about 200 K to 400 K) and medium (400 K to 700 K) temperature regions for calibration of the IR instruments under cryogenic-vacuum conditions. These BBs are presented by models of both types: variable-temperature and based on fixed points of Ga or In. BBs are characterized with high temperature uniformity and stability. Copper and aluminum alloys are used as the radiation cavity materials. The required value of emissivity ?? is achieved by using different black coatings. Low-temperature and cryogenic BBs are based on the principles of indirect multi-zone electric heating (with heat isolation from LN2 cooling loop, or by using an external liquid thermostat with circulating heat-transfer agent. The principles of operation, design and test results of BBs are described

  16. The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements

    Directory of Open Access Journals (Sweden)

    W. Gurlit

    2005-01-01

    Full Text Available Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7-418 nm and the visible from 400-652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3 and NO2, the measured solar spectra are compared with previous observations. Our solar irradiance spectrum perfectly agrees within +0.03% with the re-calibrated Kurucz et al. (1984 solar spectrum (Fontenla et al., 1999, called MODTRAN 3.7 in the visible spectral range (415-650 nm, but it is +2.1% larger in the (370-415 nm wavelength interval, and -4% smaller in the UV-A spectral range (316.7-370 nm, when the Kurucz spectrum is convolved to the spectral resolution of our instrument. Similar comparisons of the SOLSPEC (Thuillier et al., 1997, 1998a, b and SORCE/SIM (Harder et al., 2000 solar spectra with MODTRAN 3.7 confirms our findings with the values being -0.5%, +2%, and -1.4% for SOLSPEC -0.33%, -0.47%, and -6.2% for SORCE/SIM, respectively. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (- re-calibrated by the University of Bremen - with MODTRAN 3.7 indicates an agreement within -0.4% in the visible spectral range (415-585 nm, -1.6% within the 370-415 nm, and -5.7% within 325-370 nm wavelength interval, in agreement with the results of the other sensors. In agreement with findings of Skupin et al. (2002 our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.

  17. The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements

    Science.gov (United States)

    Gurlit, W.; Bösch, H.; Bovensmann, H.; Burrows, J. P.; Butz, A.; Camy-Peyret, C.; Dorf, M.; Gerilowski, K.; Lindner, A.; Noël, S.; Platt, U.; Weidner, F.; Pfeilsticker, K.

    2005-07-01

    Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7-418 nm and the visible from 400-652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively) from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3 and NO2), the measured solar spectra are compared with previous observations. Our solar irradiance spectrum perfectly agrees within +0.03% with the re-calibrated Kurucz et al. (1984) solar spectrum (Fontenla et al., 1999, called MODTRAN 3.7) in the visible spectral range (415-650 nm), but it is +2.1% larger in the (370-415 nm) wavelength interval, and -4% smaller in the UV-A spectral range (316.7-370 nm), when the Kurucz spectrum is convolved to the spectral resolution of our instrument. Similar comparisons of the SOLSPEC (Thuillier et al., 1997, 1998a, b) and SORCE/SIM (Harder et al., 2000) solar spectra with MODTRAN 3.7 confirms our findings with the values being -0.5%, +2%, and -1.4% for SOLSPEC -0.33%, -0.47%, and -6.2% for SORCE/SIM, respectively. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (- re-calibrated by the University of Bremen -) with MODTRAN 3.7 indicates an agreement within -0.4% in the visible spectral range (415-585 nm), -1.6% within the 370-415 nm, and -5.7% within 325-370 nm wavelength interval, in agreement with the results of the other sensors. In agreement with findings of Skupin et al. (2002) our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.

  18. Infrared Spectroscopy with Visible Light

    OpenAIRE

    Kalashnikov, Dmitry A.; Paterova, Anna V.; Kulik, Sergei P.; Leonid A. Krivitsky

    2015-01-01

    Spectral measurements in the infrared (IR) optical range provide unique fingerprints of materials which are useful for material analysis, environmental sensing, and health diagnostics. Current IR spectroscopy techniques require the use of optical equipment suited for operation in the IR range, which faces challenges of inferior performance and high cost. Here we develop a spectroscopy technique, which allows spectral measurements in the IR range using visible spectral range ...

  19. Visible to Near-IR Spectral Units Along the MSL Gale Crater Traverse: Comparison of In Situ Mastcam and Orbital CRISM Observations

    Science.gov (United States)

    Wellington, D. F.; Bell, J. F., III; Godber, A.; Kinch, K. M.; Fraeman, A. A.; Ehlmann, B. L.; Arvidson, R. E.; Rice, M. S.; Johnson, J. R.

    2014-12-01

    The Mastcam instruments, comprised of left (M-34) and right (M-100) 1600 x 1200 Bayer pattern CCD cameras, are each equipped with a rotating filter wheel containing six narrow-band science filters to augment RGB color imaging and allow multispectral imaging with band centers spanning the wavelength range 445 - 1013 nm. Several hundred Mastcam multispectral observations have been acquired to date, documenting a diversity of visible to near-infrared spectral behavior observed along Curiosity's traverse toward the base of Mt. Sharp. These observations include both near-field images of materials in or near the rover workspace and also observations targeted towards the more distant central mound. Near-field observations document both outcrop and float rocks, the latter of which may include both local material as well as material transported from nearer the crater rim. Far-field observations of the central mound include the lower and upper layers of the mound as well as the encircling dune field, both of which have been noted in published studies to exhibit spectral variability in the visible to near-infrared from orbital spectral data. Float rocks with spectra distinct from local outcrops may have spectral matches at locations observed only from orbit, suggesting potential source regions. Furthermore, ground-based Mastcam observations may help "ground-truth" orbital data and in turn benefit from orbital predictions of spectral diversity along the future rover traverse. We present comparisons of CRISM and Mastcam multispectral observations of Gale Crater materials to better interpret observed spectral diversity and anticipate areas of likely opportunities for observations of spectral diversity.

  20. Subwavelength imaging in the visible range using a metal coated carbon nanotube forest

    Science.gov (United States)

    Choe, Jong-Ho; Choi, Muhan; Lee, Won Jun; Kang, Byungsoo; Kim, Jinhyung; Seo, Min-Kyo; Min, Bumki; Kim, Sang Ouk; Choi, Choon-Gi

    2014-05-01

    We demonstrate subwavelength imaging in the visible range by using a metal coated carbon nanotube forest. Under 532 nm illumination, a 160 nm separated double slit is resolved. This corresponds to the resolution of 0.3 wavelength. By controlling the growing conditions and with the help of the microtoming technique, we made a dense carbon nanotube forest layer of 400 nm thickness. The metal coated carbon nanotube forest, acting as a wire medium nanolens, delivers imaging information including details in the evanescent fields near the objects.We demonstrate subwavelength imaging in the visible range by using a metal coated carbon nanotube forest. Under 532 nm illumination, a 160 nm separated double slit is resolved. This corresponds to the resolution of 0.3 wavelength. By controlling the growing conditions and with the help of the microtoming technique, we made a dense carbon nanotube forest layer of 400 nm thickness. The metal coated carbon nanotube forest, acting as a wire medium nanolens, delivers imaging information including details in the evanescent fields near the objects. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00075g

  1. Dose dependence of visible range diffuse reflectivity for Si+ and C+ ion implanted polymers

    International Nuclear Information System (INIS)

    Detailed insight into the near-surface area of the ion beam modified polymer is supplied by the measured diffuse reflectivity spectra. The near-surface layer (50 to 150 nm) of bulk polymer samples have been implanted with silicon (Si+) and carbon (C+) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 5.1012-2.1017 cm+2). The polymer materials studied were: ultra-high-molecular-weight polyethylene (UHMWPE), poly-propylene (PP), and poly-tetra-fluor-ethylene (PTFE). The diffuse optical reflectivity spectra Rd = f(?) of the implanted samples have been measured in the visible range (? = 400 to 830 nm). In this paper the dose dependences of the size and sign of the diffuse reflectivity changes ?Rd = f(D) have been analyzed

  2. Using Visible Spectral Information to Predict Long-Wave Infrared Spectral Emissivity: A Case Study over the Sokolov Area of the Czech Republic with an Airborne Hyperspectral Scanner Sensor

    Directory of Open Access Journals (Sweden)

    Gila Notesco

    2013-11-01

    Full Text Available Remote-sensing platforms are often comprised of a cluster of different spectral range detectors or sensors to benefit from the spectral identification capabilities of each range. Missing data from these platforms, caused by problematic weather conditions, such as clouds, sensor failure, low temporal coverage or a narrow field of view (FOV, is one of the problems preventing proper monitoring of the Earth. One of the possible solutions is predicting a detector or sensor’s missing data using another detector/sensor. In this paper, we propose a new method of predicting spectral emissivity in the long-wave infrared (LWIR spectral region using the visible (VIS spectral region. The proposed method is suitable for two main scenarios of missing data: sensor malfunctions and narrow FOV. We demonstrate the usefulness and limitations of this prediction scheme using the airborne hyperspectral scanner (AHS sensor, which consists of both VIS and LWIR spectral regions, in a case study over the Sokolov area, Czech Republic.

  3. Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols

    Directory of Open Access Journals (Sweden)

    C. E. Lund Myhre

    2004-06-01

    Full Text Available Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.

  4. Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols

    Directory of Open Access Journals (Sweden)

    C. E. Lund Myhre

    2004-01-01

    Full Text Available Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.

  5. Unattended real-time re-establishment of visibility in high dynamic range video and stills

    Science.gov (United States)

    Abidi, B.

    2014-05-01

    We describe a portable unattended persistent surveillance system that corrects for harsh illumination conditions, where bright sun light creates mixed contrast effects, i.e., heavy shadows and washouts. These effects result in high dynamic range scenes, where illuminance can vary from few luxes to a 6 figure value. When using regular monitors and cameras, such wide span of illuminations can only be visualized if the actual range of values is compressed, leading to the creation of saturated and/or dark noisy areas and a loss of information in these areas. Images containing extreme mixed contrast cannot be fully enhanced from a single exposure, simply because all information is not present in the original data. The active intervention in the acquisition process is required. A software package, capable of integrating multiple types of COTS and custom cameras, ranging from Unmanned Aerial Systems (UAS) data links to digital single-lens reflex cameras (DSLR), is described. Hardware and software are integrated via a novel smart data acquisition algorithm, which communicates to the camera the parameters that would maximize information content in the final processed scene. A fusion mechanism is then applied to the smartly acquired data, resulting in an enhanced scene where information in both dark and bright areas is revealed. Multi-threading and parallel processing are exploited to produce automatic real time full motion corrected video. A novel enhancement algorithm was also devised to process data from legacy and non-controllable cameras. The software accepts and processes pre-recorded sequences and stills, enhances visible, night vision, and Infrared data, and successfully applies to night time and dark scenes. Various user options are available, integrating custom functionalities of the application into intuitive and easy to use graphical interfaces. The ensuing increase in visibility in surveillance video and intelligence imagery will expand the performance and timely decision making of the human analyst, as well as that of unmanned systems performing automatic data exploitation, such as target detection and identification.

  6. Observation of the fine structure for rovibronic spectral lines in visible part of emission spectra of $D_2$

    CERN Document Server

    Lavrov, B P; Zhukov, A S

    2011-01-01

    For the first time the fine structure of rovibronic spectral lines in visible part of emission spectra of $D_2$ molecule has been observed. Observed splitting in visible doublets is about 0.2 cm$^{-1}$ in good accordance with previous observations in the infrared part of the spectrum ($a^3\\Sigma_g^+ \\to c^3\\Pi_u$ electronic transition) by means of FTIR and laser spectroscopy. Relative intensities of the fine structure components are in agreement with our calculations of adiabatic line strengths for Hund's case "b" coupling scheme.

  7. An Approach for Identifying of Fusarium Infected Maize Grains by Spectral Analysis in the Visible and Near Infrared Region, SIMCA Models, Parametric and Neural Classifiers

    Directory of Open Access Journals (Sweden)

    Tsvetelina Draganova

    2010-08-01

    Full Text Available An approach for identifying of Fusarium infected single maize grains based on diffuse reflectance in visible and near infrared region is proposed in the paper. Spectral characteristics were collected in the range 400-2500 nm in steps of 2 nm. Soft independent modeling of class analogy (SIMCA is used for data processing. Maize grains classification is based on SIMCA classifier and Probabilistic neural network (PNN. Recognition accuracy which is achieved for both classes of grains is respectively 99.89% for healthy, and 93.7% for infected.

  8. Tailoring Metallodielectric Structures for Super Resolution and Superguiding Applications in the Visible and Near IR Ranges

    CERN Document Server

    De Ceglia, D; Cappeddu, M G; Centini, M; Akozbek, N; DOrazio, A; Haus, J W; Bloemer, M J; Scalora, M

    2008-01-01

    We discuss propagation effects in realistic, transparent, metallo-dielectric photonic band gap structures in the context of negative refraction and super-resolution in the visible and near infrared ranges. In the resonance tunneling regime, we find that for transverse-magnetic incident polarization, field localization effects contribute to a waveguiding phenomenon that makes it possible for the light to remain confined within a small fraction of a wavelength, without any transverse boundaries, due to the suppression of diffraction. This effect is related to negative refraction of the Poynting vector inside each metal layer, balanced by normal refraction inside the adjacent dielectric layer: The degree of field localization and material dispersion together determine the total momentum that resides within any given layer, and thus the direction of energy flow. We find that the transport of evanescent wave vectors is mediated by the excitation of quasi-stationary, low group velocity surface waves responsible for...

  9. Generation of pulsed light in the visible spectral region based on non-linear cavity dumping

    DEFF Research Database (Denmark)

    Johansson, Sandra; Andersen, Martin

    We propose a novel generic approach for generation of pulsed light in the visible spectrum based on sum-frequency generation between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser. For demonstration, we used a CW 1342 nm laser mixed with a passively Q-switched 1064 nm laser to generate pulsed light at 593 nm. Light sources in the yellow spectral region have several applications, e.g. dermatology, laser displays and flow cytometry. Traditionally, copper-vapor lasers at 578 nm and dye lasers are used in this spectral region. These are however bulky, inefficient and contain highly toxic gasses and liquids. Different approaches to replace these are: frequency-doubled semiconductor lasers1, sum-frequency generation between solid-state lasers in both in CW2 and Q-switched3 operation and Raman lasers4. An intra-cavity 1342 nm Nd:YVO4 laser acted as the CW light source, using a folded cavity to achieve tight focussing in the non-linear crystal which was a 11 mm long PPKTP. The pulsed light source was a Nd:YVO4 laser emitting at 1064 nm using Cr:YAG as a passive saturable absorber, resulting in a pulse length of 100 ns and a repetition frequency of 215 kHz. Both lasers were pumped with 808 nm laser diodes delivering 4 W of output power. The circulating power of the 1342 nm laser was 57 W and the peak power of the 1064 nm laser reaching the PPKTP crystal was 17 W. A peak power of approximately 4 W at 593 nm was measured. Accounting for the Fresnel losses for the outcoupling mirror, this would correspond to 5.3 W of generated 593 nm power. The pulsed yellow-orange light follows exactly the 1064 nm pulses in terms of repetition frequency and pulse width. By matching the pulse length of the passively Q-switched laser to the round-trip time of the CW intra-cavity laser, the circulating power could be more efficiently depleted. Calculations give that yellow peak powers in the order of 50 W could be reached.

  10. Polarization effects of the spectral thermal infrared and visible emission from ferromagnets

    Science.gov (United States)

    Broennimann, R.; Kneubuehl, F. K.

    Partial circular polarization of the spectral thermal emission of an axially magnetized iron rod was measured in the spectral range from 0.25 eV to 2 eV for iron-cobalt alloys. The spectra show a maximum at low energies. With increasing photon energy the polarization decreases and changes its sign at 1.35 eV, 1.50 eV, and 1.65 eV for the alloys Fe79Co21, Fe55Co45 and Fe31Co69, respectively. The dependence of the effect on wavelength and cobalt concentration is shown. The thermal radiation emitted from a ferromagnetic sample magnetized parallel to its surface is partially linearly polarized. The spectra show a shift to higher energies for increasing cobalt concentration. Polarization decreases almost linearly with rising temperature for iron and Fe31Co69. For Fe79Co21 and Fe55Co45 the polarization shows a sharp drop at the Curie temperature, associated with the phase transition from bcc to fcc. In addition, Fe55Co45 shows a hysteresis of linear polarization for rising and falling temperature, due to the order-disorder transition at 1000 K.

  11. Polylogarithmic representation of radiative and thermodynamic properties of thermal radiation in a given spectral range: II. Real-body radiation

    CERN Document Server

    Fisenko, Anatoliy I

    2015-01-01

    The general analytical expressions for the thermal radiative and thermodynamic properties of a real-body are obtained in a finite range of frequencies at different temperatures. The frequency dependence of the spectral emissivity is represented as a power series. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and total emissivity are expressed in terms of the polylogarithm functions. The general expressions for the thermal radiative and thermodynamic functions are applied for the study of thermal radiation of liquid and solid zirconium carbide. These functions are calculated using experimental data for the frequency dependence of the normal spectral emissivity in the visible-near infrared range at the melting (freezing) point. The gaps between the thermal radiative and thermodynamic functions of liquid and solid zirconium carbide are observed. The g...

  12. High-sensitivity high-stability silicon photodiodes for DUV, VUV and EUV spectral ranges

    Science.gov (United States)

    Shi, L.; Nihtianov, S.; Scholze, F.; Gottwald, A.; Nanver, L. K.

    2011-09-01

    In this paper, the optical and electrical performance of a newly developed silicon photodiode based on pure boron CVD technology (PureB-diodes) is introduced. Due to their extremely shallow p-n junction, with the depletion zone starting only a few nanometers below the surface, and nm-thin pure-boron-layer coverage of the anode surface, PureB-diodes have so far demonstrated the highest reported spectral responsivity in all sub-visible ultraviolet (UV) ranges: DUV (deep ultraviolet), VUV (vacuum ultraviolet) and EUV (extreme ultraviolet), covering a spectrum from 220 nm down to few nanometersMoreover, the measured responsivity at 13.5 nm wavelengths (EUV) approaches the theoretical maximum (~0.27A/W). PureB-diodes also maintain excellent electrical characteristics, with saturation-current values typical for high-quality silicon diodes, and a high breakdown voltage. Experimental results have demonstrated the extremely high radiation hardness of PureB-diodes when exposed to high EUV radiant exposures in the order of a few hundred kJ/cm2. No change in the responsivity is observed within the experimental uncertainty. In the more challenging DUV and especially VUV ranges, PureB-diodes demonstrate a slight initial drop of responsivity (1 to 2%), after which they stabilizes their performance.

  13. Suitability of a wall-stabilized arc as a transfer standard of spectral radiance in the spectral range 165 to 350 nm

    Science.gov (United States)

    Key, P. J.; Fu-Tian, L.; Nettleton, D. H.

    1983-04-01

    The suitability of a miniaturized wall-stabilized argon arc as a transfer standard of spectral radiance, (relative and absolute) was investigated. Arc calibration: using deuterium lamps to transfer the relative spectral radiance scale; based on synchrotron radiation; and using the absolute spectral radiance of tungsten ribbon lamps calibrated against the visible, black body radiator based emission scale is described. Tests show that the arc is satisfactory for maintaining a scale of relative spectral radiance without recourse to a primary standard.

  14. Partially Transparent Petaled Mask/Occulter for Visible-Range Spectrum

    Science.gov (United States)

    Shiri, Ron Shahram; Wasylkiwskyj, Wasyl

    2013-01-01

    The presence of the Poisson Spot, also known as the spot of Arago, has been known since the 18th century. This spot is the consequence of constructive interference of light diffracted by the edge of the obstacle where the central position can be determined by symmetry of the object. More recently, many NASA missions require the suppression of this spot in the visible range. For instance, the exoplanetary missions involving space telescopes require telescopes to image the planetary bodies orbiting central stars. For this purpose, the starlight needs to be suppressed by several orders of magnitude in order to image the reflected light from the orbiting planet. For the Earth-like planets, this suppression needs to be at least ten orders of magnitude. One of the common methods of suppression involves sharp binary petaled occulters envisioned to be placed many thousands of miles away from the telescope blocking the starlight. The suppression of the Poisson Spot by binary sharp petal tips can be problematic when the thickness of the tips becomes smaller than the wavelength of the incident beam. First they are difficult to manufacture and also it invalidates the laws of physical optics. The proposed partially transparent petaled masks/occulters compensate for this sharpness with transparency along the surface of the petals. Depending on the geometry of the problem, this transparency can be customized such that only a small region of the petal is transparent and the remaining of the surface is opaque. This feature allows easy fabrication of this type of occultation device either as a mask or occulter. A partially transparent petaled mask/ occulter has been designed for the visible spectrum range. The mask/occulter can suppress the intensity along the optical axis up to ten orders of magnitude. The design process can tailor the mask shape, number of petals, and transparency level to the near-field and farfield diffraction region. The mask/occulter can be used in space astronomy, ground-based telescope, and high-energy laser systems, and optical lithography to eliminate the Poisson Spot.

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

    Science.gov (United States)

    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.

  16. First Experiences Using Small Unmanned Aerial Vehicles for Volcano Observation in the Visible Range

    Science.gov (United States)

    Buschmann, M.; Krüger, L.; Bange, J.

    2007-05-01

    Many of the most active volcanoes in the world are located in Middle and South America. While permanently installed sensors for seismicity give reliable supervision of volcanic activities, they lack the possibility to determine occurrence and extent of surface activities. Both from the point of science and civil protection, visible documentation of activities is of great interest. While satellites and manned aircraft already offer many possibilities, they also have disadvantages like delayed or poor image data availability or high costs. The Institute of Aerospace Systems of the Technical University of Braunschweig, in collaboration with the spin-off company Mavionics, developed a family of extremely small and lightweight Unmanned Aerial Vehicles (UAV), with the smallest aircraft weighting only 550~g (19~ounces) at a wing span of 50 cm (20~inch). These aircraft are operating completely automatically, controlled by a highly miniaturized autopilot system. Flight mission is defined by a list of GPS waypoints using a conventional notebook. While in radio range, current position and status of the aircraft is displayed on the notebook and waypoints can easily be changed by the user. However, when radio connection is not available, the aircraft operates on its on, completing the flight mission automatically. This greatly increases the operating range of the system. Especially for the purpose of volcano observation in South America, the aircraft Carolo~P330 was developed, weighting 5~kg (11~pounds) at a wing span of 3.3~m ( 11~ft). The whole system can be easily carried by car and the electric propulsion system avoids handling of flammable liquids. The batteries can be recharged in the field. Carolo~P330 has an endurance of up to 90~minutes at a flight speed of 25~m/s, giving it a maximum range of 67 km (41~miles). It was especially designed to operate under harsh conditions. The payload is a digital still camera, which delivers aerial images with a resolution of up to 8~megapixel. On a field campaign in 2005, the performance of the system was evaluated at the two active Ecuadorian volcanoes Cotopaxi and El~Reventador. After hand-launch at Mt. Cotopaxi, the autopilot brought the aircraft up to 7,000~m above sea level (starting from a plateau on 4,500~m a.s.l.), with temperatures around the freezing point. At El~Reventador active lava flows were documented in the tropical montane rain forest. Since the position and attitude of the aircraft is recorded within the autopilot system, the single aerial images can be referenced automatically after the flight to form a mosaic of images. The whole processing chain from mission planning to image mosaic takes less than half a day. Besides the technical details of this cost-effective remote sensing system, the results of the measurement campaign in 2005 will be presented. An outlook will discuss the installation of other payload for thermal imaging or air sampling.

  17. The Relation Between the Spectral Synthesis of Galaxies in the Visible Region and Their UV Emission

    Science.gov (United States)

    Dantas, M. L.; Sodré, L., Jr.

    2014-10-01

    The STARLIGHT Project has analyzed almost a million spectra extracted from the Sloan Digital Sky Survey (SDSS) by using the empirical spectral synthesis approach described by Cid Fernandes et al.(2005). Spectral synthesis consists on the optical spectrum fitting by using simple stellar population libraries, such as Bruzual & Charlot (2003). It also considers the reddening caused by dust and the velocity dispersion due to the motion of the stars within the galaxy. Since the model that best fits the optical region can also be extended to the ultraviolet, we compare our predictions to the UV photometry of the same galaxies measured by the GALEX satellite, studying the systematics and nature of the differences. In this current presentation, we show the upcoming challenges in order to accomplish this investigation. The main motivation of this study is to obtain realistic spectral models from the UV to the optical regions for the study of high redshift galaxies.

  18. AlGaInP quantum dots for optoelectronic applications in the visible spectral range

    International Nuclear Information System (INIS)

    The scope of this work is the fabrication and characterization of AlGaInP quantum dots on GaP an GaAs substrates. Based on such quantum dots, semiconductor lasers have been realized, emitting between 660 nm and 730 nm at room temperature. The examination of broad-area lasers processed on these structures suggests that active layers of larger quantum dots with higher aluminium contents lead to lasers with better performance at similar emission wavelength. Additionally, quantum dots grown on GaP substrates have been characterized, that were embedded in AlGaP barriers. Since these barriers exhibit an indirect bandgap, a non-trivial band alignment within these structures is expected. In this work, numerical 3D-simulations are employed to calculate the band alignment including strain and internal fields. Also, ground state wavefunctions of charge carriers have been determined. A thorough comparison between theory and experiment connects the measured emission wavelength and luminescence intensities with calculated transition energies and wavefunction overlaps.

  19. Time-resolved photoluminescence spectroscopy of semiconductors for optical applications beyond the visible spectral range

    Energy Technology Data Exchange (ETDEWEB)

    Chernikov, Alexey A.

    2011-07-01

    The work discussed in this thesis is focused on the experimental studies regarding these three steps: (1) investigation of the fundamental effects, (2) characterization of new material systems, and (3) optimization of the semiconductor devices. In all three cases, the experimental technique of choice is photoluminescence (PL) spectroscopy. The thesis is organized as follows. Chapter 2 gives a summary of the PL properties of semiconductors relevant for this work. The first section deals with the intrinsic processes in an ideal direct band gap material, starting with a brief summary of the theoretical background followed by the overview of a typical PL scenario. In the second part of the chapter, the role of the lattice-vibrations, the internal electric fields as well as the influence of the band-structure and the dielectric environment are discussed. Finally, extrinsic PL properties are presented in the third section, focusing on defects and disorder in real materials. In chapter 3, the experimental realization of the spectroscopic studies is discussed. The time-resolved photoluminescence (TRPL) setup is presented, focusing on the applied excitation source, non-linear frequency mixing, and the operation of the streak camera used for the detection. In addition, linear spectroscopy setup for continous-wave (CW) PL and absorption measurements is illustrated. Chapter 4 aims at the study of the interactions between electrons and lattice-vibrations in semiconductor crystals relevant for the proper description of carrier dynamics as well as the heat-transfer processes. The presented discussion covers the experimental studies of many-body effects in phonon-assisted emission of semiconductors due to the carriercarrier Coulomb-interaction. The corresponding theoretical background is discussed in detail in chapter 2. The investigations are focused on the two main questions regarding electron-hole plasma contributions to the phonon-assisted light-matter interaction as well as the impact of Coulomb-correlations on the carrier-phonon scattering. The experiments presented in chapter 5 deal with the characterization of recently synthesizedmaterial systems: ZnO/(ZnMg)O heterostructures, GaN quantum wires (QWires), as well as (GaAs)Bi quantum wells (QWs). TRPL spectroscopy is applied to gain insight as well as a better understanding of the respective carrier relaxation and recombination processes crucial for the device operation. The aim of the studies is the systematic investigation of carrier dynamics influenced by disorder. The measurements are supported by kinetic Monte- Carlo simulations, providing a quantitative analysis of carrier localization effects. In chapter 6, optimization and characterization studies of semiconductor lasers, based on the well-studied (GaIn)As material system designed for NIR applications, are performed. The device under investigation is the so-called vertical-external-cavity surface emitting laser (VECSEL). The experiments focus on the study of the thermal properties of a high-power VECSEL. The distribution and removal of the excess heat as well as the optimization of the laser for increased performance are addressed applying different heat-spreading and heat-transfer approaches. Based on these investigations, the possibility for power-scaling is evaluated and the underlying restrictions are analyzed. The latter investigations are performed applying spatially-resolved PL spectroscopy. An experimental setup is designed for monitoring the spatial distribution of heat in the semiconductor structure during laser operation.

  20. Air-suspended TiO2-based HCG reflectors for visible spectral range

    Science.gov (United States)

    Hashemi, Ehsan; Bengtsson, Jörgen; Gustavsson, Johan; Carlsson, Stefan; Rossbach, Georg; Haglund, Åsa

    2015-02-01

    For GaN-based microcavity light emitters, such as vertical-cavity surface-emitting lasers (VCSELs) and resonant cavity light emitting diodes (RCLEDs) in the blue-green wavelength regime, achieving a high reflectivity wide bandwidth feedback mirror is truly challenging. The material properties of the III-nitride alloys are hardly compatible with the conventional distributed Bragg reflectors (DBRs) and the newly proposed high-contrast gratings (HCGs). Alternatively, at least for the top outcoupling mirror, dielectric materials offer more suitable material combinations not only for the DBRs but also for the HCGs. HCGs may offer advantages such as transverse mode and polarization control, a broader reflectivity spectrum than epitaxially grown DBRs, and the possibility to set the resonance wavelength after epitaxial growth by the grating parameters. In this work we have realized an air-suspended TiO2 grating with the help of a SiO2 sacrificial layer. The deposition processes for the dielectric layers were fine-tuned to minimize the residual stress. To achieve an accurate control of the grating duty cycle, a newly developed lift-off process, using hydrogen silesquioxan (HSQ) and sacrificial polymethyl-methacrylate (PMMA) resists, was applied to deposit the hard mask, providing sub-10 nm resolution. The finally obtained TiO2/air HCGs were characterized in a micro-reflectance measurement setup. A peak power reflectivity in excess of 95% was achieved for TM polarization at the center wavelength of 435 nm, with a reflectivity stopband width of about 80 nm (FWHM). The measured HCG reflectance spectra were compared to corresponding simulations obtained from rigorous coupled-wave analysis and very good agreement was found.

  1. A new list of thorium and argon spectral lines in the visible

    OpenAIRE

    Lovis, C.; Pepe, F.

    2007-01-01

    Aims. We present a new list of thorium and argon emission lines in the visible obtained by analyzing high-resolution (R=110,000) spectra of a ThAr hollow cathode lamp. The aim of this new line list is to allow significant improvements in the quality of wavelength calibration for medium- to high-resolution astronomical spectrographs. Methods. We use a series of ThAr lamp exposures obtained with the HARPS instrument (High Accuracy Radial-velocity Planet Searcher) to detect pre...

  2. Spectral absorptions on Phobos and Deimos in the visible/near infrared wavelengths and their compositional constraints

    Science.gov (United States)

    Fraeman, A. A.; Murchie, S. L.; Arvidson, R. E.; Clark, R. N.; Morris, R. V.; Rivkin, A. S.; Vilas, F.

    2014-02-01

    Absorption features on Phobos and Deimos in the visible/near infrared wavelength region (0.4-3.9 ?m) are mapped using observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Fe2+ electronic absorptions diagnostic of olivine and pyroxene are not detected. A broad absorption centered around 0.65 ?m within the red spectral units of both moons is detected, and this feature is also evident in telescopic, Pathfinder, and Phobos-2 observations of Phobos. A 2.8 ?m metal-OH combination absorption on both moons is also detected in the CRISM data, and this absorption is shallower in the Phobos blue unit than in the Phobos red unit and Deimos. The strength, position, and shape of both of the 0.65 ?m and 2.8 ?m absorptions are similar to features seen on red-sloped, low-albedo primitive asteroids. Two end-member hypotheses are presented to explain the spectral features on Phobos and Deimos. The first invokes the presence of highly desiccated Fe-phyllosilicate minerals indigenous to the bodies, and the second invokes Rayleigh scattering and absorption of small iron particles formed by exogenic space weathering processing, coupled with implantation of H from solar wind. Both end-member hypotheses may play a role, and in situ exploration will be needed to ultimately determine the underlying causes for the pair of spectral features observed on Phobos and Deimos.

  3. Transmittance and optical constants of Ca films in the 4-1000??eV spectral range.

    Science.gov (United States)

    Marcos, Luis Rodríguez-de; Larruquert, Juan I; Vidal-Dasilva, Manuela; Aznárez, José A; García-Cortés, Sergio; Méndez, José A; Poletto, Luca; Frassetto, Fabio; Marco Malvezzi, A; Bajoni, Daniele; Giglia, Angelo; Mahne, Nicola; Nannarone, Stefano

    2015-03-10

    The low expected absorption of Ca in the extreme ultraviolet (EUV) makes it an attractive material for multilayers and filters because most materials in nature strongly absorb the EUV. Few optical constant data had been reported for Ca. In this research, Ca films of various thicknesses were deposited on grid-supported C films and their transmittance measured in situ from the visible to the soft x-rays. The measurement range contains M2,3 and L2,3 absorption edges. Transmittance measurements were used to obtain the Ca extinction coefficient k. A minimum k of 0.017 was obtained at ?23??eV, which makes Ca a promising low-absorption material for EUV coatings. A second spectral range of interest for its low absorption is below the Ca L3 edge at ?343??eV. Measured k data and extrapolations were used to calculate the refractive index n using Kramers-Krönig relations. This is the first self-consistent data set on Ca covering a wide spectral range including the EUV. PMID:25968365

  4. Amorphous silicon thin film as tuneable and high sensitive photodetector in the UV and far UV spectral range

    Science.gov (United States)

    de Cesare, G.; Irrera, F.; Palma, F.; Nascetti, A.; Naletto, G.; Nicolosi, P.; Pace, E.

    1997-02-01

    We describe an innovative family of photodiodes based on a-Si:H/a-SiC:H p-i-n junction grown by Glow Discharge. The aim of this technology is to realize two-dimensional detector arrays on cheap substrates such as glass or flexible materials. Their spectral response can be tuned during the growing process to have high sensitivity in the ultraviolet and vacuum ultraviolet ranges, selecting the absorption profile in the semiconductor and the film thickness. We have performed a set of measurements at room temperature to characterize the visible and UV response of a first generation prototype, having a sensitive area of 0.17 cm 2, and an improved second generation optimized for UV photon detection.

  5. Metasurfaces based on Gallium Nitride High Contrast Gratings at Visible Range

    Science.gov (United States)

    Wang, Zhenhai; He, Shumin; Liu, Qifa; Wang, Wei; Wang, Yongjin; Zhu, Hongbo; Grünberg Research Centre Team

    2015-03-01

    Metasurfaces are currently attracting global attention due to their ability to achieve full control of light propagation. However, these metasurfaces have thus far been constructed mostly from metallic materials, which greatly limit the diffraction efficiencies because of the ohmic losses. Semiconducting metasurfaces offer one potential solution to the issue of losses. Besides, the use of semiconducting materials can broaden the applicability of metasurfaces, as they enable facile integration with electronics and mechanical systems and can benefit from mature semiconductor fabrication technologies. We have proposed visible-light metasurfaces (VLMs) capable of serving as lenses and beam deflecting elements based on gallium nitride (GaN) high contrast gratings (HCGs). By precisely manipulating the wave-fronts of the transmitted light, we theoretically demonstrate an HCG focusing lens with transmissivity of 83.0% and numerical aperture of 0.77, and a VLM with beam deflection angle of 6.03° and transmissivity as high as 93.3%. The proposed metasurfaces are promising for GaN-based visible light-emitting diodes (LEDs), which would be robust and versatile for controlling the output light propagation and polarization, as well as enhancing the extraction efficiency of the LEDs.

  6. Multi range spectral feature fitting for hyperspectral imagery in extracting oilseed rape planting area

    Science.gov (United States)

    Pan, Zhuokun; Huang, Jingfeng; Wang, Fumin

    2013-12-01

    Spectral feature fitting (SFF) is a commonly used strategy for hyperspectral imagery analysis to discriminate ground targets. Compared to other image analysis techniques, SFF does not secure higher accuracy in extracting image information in all circumstances. Multi range spectral feature fitting (MRSFF) from ENVI software allows user to focus on those interesting spectral features to yield better performance. Thus spectral wavelength ranges and their corresponding weights must be determined. The purpose of this article is to demonstrate the performance of MRSFF in oilseed rape planting area extraction. A practical method for defining the weighted values, the variance coefficient weight method, was proposed to set up criterion. Oilseed rape field canopy spectra from the whole growth stage were collected prior to investigating its phenological varieties; oilseed rape endmember spectra were extracted from the Hyperion image as identifying samples to be used in analyzing the oilseed rape field. Wavelength range divisions were determined by the difference between field-measured spectra and image spectra, and image spectral variance coefficient weights for each wavelength range were calculated corresponding to field-measured spectra from the closest date. By using MRSFF, wavelength ranges were classified to characterize the target's spectral features without compromising spectral profile's entirety. The analysis was substantially successful in extracting oilseed rape planting areas (RMSE ? 0.06), and the RMSE histogram indicated a superior result compared to a conventional SFF. Accuracy assessment was based on the mapping result compared with spectral angle mapping (SAM) and the normalized difference vegetation index (NDVI). The MRSFF yielded a robust, convincible result and, therefore, may further the use of hyperspectral imagery in precision agriculture.

  7. Thin chalcogenide capillaries as efficient waveguides in the mid-IR - THz spectral range

    CERN Document Server

    Mazhorova, Anna; Ung, Bora; Rozé, Mathieu; Gorgutsa, Stepan; Skorobogatiy, Maksim

    2011-01-01

    We present chalcogenide glass As2Se3 capillaries as efficient waveguides in the mid-IR and THz spectral ranges. The capillaries are fabricated using a double crucible glass drawing technique. The wall thickness of the glass capillary is properly designed and controlled during drawing, and we are able to produce capillaries with different wall thickness, starting from 12 \\mum and up to 130 \\mum. Such capillaries show low loss properties in the whole target wavelength region. In the mid-IR range guidance is governed by Fresnel reflection and antiguidance mechanisms (ARROWs), while in the THz spectral range thin walls capillaries guide via total internal reflection.

  8. High-speed high-precision and ultralong-range complex spectral domain dimensional metrology.

    Science.gov (United States)

    Bao, Wen; Shen, Yi; Chen, Tao; Li, Peng; Ding, Zhihua

    2015-05-01

    A precise, nondestructive dimensional metrological system is crucial to manufacturing and packaging of multi-component optical system. To this end, an orthogonal dispersive spectrometer based complex spectral domain interferometric system for high-speed high-precision and ultralong-range dimensional metrology is developed. An improved complex method based on actual spectral phase shift is proposed to achieve ultrahigh suppression of artifacts. Suppression ratios of 80 dB for DC and 60 dB for mirror images are realized, the highest ratios among existing complex methods. To ensure high-precision in distance determination, an averaged spectral phase measurement algorithm is adopted. A precision of 60 nm within a measurement range of 200 mm without axial movement of the sample is demonstrated. The measurement range is readily extendable if axial movement of the sample and range cascading are involved. The system holds potential applications in various areas for real-time nondestructive testing and evaluation. PMID:25969196

  9. Method And Apparatus For Examining A Tissue Using The Spectral Wing Emission Therefrom Induced By Visible To Infrared Photoexcitation.

    Energy Technology Data Exchange (ETDEWEB)

    Alfano, Robert R. (3777 Independence Ave., Bronx, NY 10463); Demos, Stavros G. (3550 Pacific Ave., Apt. 304, Livermore, CA 94550); Zhang, Gang (3 Rieder Rd., Edison, NJ 08817)

    2003-12-16

    Method and an apparatus for examining a tissue using the spectral wing emission therefrom induced by visible to infrared photoexcitation. In one aspect, the method is used to characterize the condition of a tissue sample and comprises the steps of (a) photoexciting the tissue sample with substantially monochromatic light having a wavelength of at least 600 nm; and (b) using the resultant far red and near infrared spectral wing emission (SW) emitted from the tissue sample to characterize the condition of the tissue sample. In one embodiment, the substantially monochromatic photoexciting light is a continuous beam of light, and the resultant steady-state far red and near infrared SW emission from the tissue sample is used to characterize the condition of the tissue sample. In another embodiment, the substantially monochromatic photoexciting light is a light pulse, and the resultant time-resolved far red and near infrared SW emission emitted from the tissue sample is used to characterize the condition of the tissue sample. In still another embodiment, the substantially monochromatic photoexciting light is a polarized light pulse, and the parallel and perpendicular components of the resultant polarized time-resolved SW emission emitted from the tissue sample are used to characterize the condition of the tissue sample.

  10. Spectral Characteristics of Tropical Anvils Obtained by Combining TRMM Precipitation Radar with Visible and Infrared Scanner Data

    Science.gov (United States)

    Yang, Yuan-Jian; Lu, Da-Ren; Fu, Yun-Fei; Chen, Feng-Jiao; Wang, Yu

    2015-06-01

    The spectral characteristics of anvils in tropical areas (25°S-25°N) have been investigated on the basis of data from the tropical rainfall measuring mission's (TRMM) precipitation radar (PR) and a visible and infrared scanner (VIRS), from 1998 to 2007. The anvils' vertical structures were captured by TRMM PR and categorized into two subtypes: ice anvils with an echo base of ?6 km and mixed anvils with an echo base between 3 and 6 km. Visible and infrared signals for the anvils, which are from reflectance at 0.63 and 1.6 ?m (hereafter referred to as RF1 and RF2, respectively) and the equivalent brightness temperatures of a black body at 3.7, 10.8, and 12.0 ?m (hereafter referred to as TB3, TB4, and TB5, respectively), were derived simultaneously by use of TRMM VIRS. The findings reveal that the normalized frequency distribution (i.e., probability density functions, PDF) of anvil tops and bases have a bimodal distribution whereas that of anvil thickness has a single-peak curve. For visible signals, the PDF distribution of RF1 (RF2) for anvils, mixed anvils, and ice anvils has an approximately symmetric distribution with a tropics-wide averages of 0.74, 072, and 0.80 (0.21, 0.21, and 0.20), respectively. It can be concluded that ice anvils are optically thicker and contain many more ice-cloud droplets at the cloud top than mixed anvils. RF1 of anvils is usually lower over land than over ocean, by ~0.1, whereas RF2 of anvils is usually higher over land than over ocean, by ~0.3. This implies that anvil clouds have thinner optical depth and their cloud tops consist of many more small ice droplets over land than over ocean. For infrared signals, TB4 is regarded as a representative channel. The PDF distribution of TB4 for anvils and mixed anvils is broad, with tropics-wide averages of 229.2 and 232 K, respectively. They contain two peaks and the secondary peak lies at a much lower value. For ice anvils, the PDF distribution of TB4 is a single-peak curve with a tropics-wide average of 219.5 K. Mean TB4 of anvils, mixed anvils, and ice anvils is usually lower over land than over ocean, by ~3.6 K, ~1.6 K, and 5 K, respectively. In addition, land-ocean differences between RF1-to-RF2 reflectance ratios are more obvious than those between TB4 and TB5 brightness temperatures. Furthermore, these spectral signals have been proved to be a potentially useful way of revealing the presence of anvils over land and ocean, and especially for separating anvils into the mixed and ice subtypes. Finally, long-term mean values reveal that the spectral signals of anvils and of stratiform and convective precipitating clouds are indeed different, and that the difference varies with different geographical location. In real time, however, uncertainty still exists when only spectral signals are used to discriminate anvils from stratiform and convective precipitating clouds, which means active satellite observations are indispensable.

  11. PtSi-n-Si Schottky-barrier photodetectors with stable spectral responsivity in the 120-250 nm spectral range

    Science.gov (United States)

    Solt, K.; Melchior, H.; Kroth, U.; Kuschnerus, P.; Persch, V.; Rabus, H.; Richter, M.; Ulm, G.

    1996-12-01

    Front-illuminated PtSi-n-Si Schottky barrier photodiodes have been developed for the ultraviolet and vacuum ultraviolet spectral range. Their spectral responsivity was determined in the 120-500 nm spectral range by use of a cryogenic electrical substitution radiometer operated with spectrally dispersed synchrotron radiation. For wavelengths below 250 nm, the spectral responsivity is about 0.03 A/W, comparable to that of GaAsP Schottky photodiodes. Unlike the GaAsP diodes, the new PtSi-n-Si diodes have a spatially uniform response which is virtually stable after prolonged exposure to short wavelength radiation. Even after a radiant exposure of 150 mJ cm-2 at wavelength 120 nm, the relative reduction in spectral responsivity remains below 0.2%. Due to these features, this type of photodiode is a promising candidate for use as secondary detector standard in the ultraviolet and vacuum ultraviolet spectral ranges.

  12. Wavelength conversion based spectral imaging

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin

    There has been a strong, application driven development of Si-based cameras and spectrometers for imaging and spectral analysis of light in the visible and near infrared spectral range. This has resulted in very efficient devices, with high quantum efficiency, good signal to noise ratio and high resolution for this spectral region. Today, an increasing number of applications exists outside the spectral region covered by Si-based devices, e.g. within cleantech, medical or food imaging. We present a technology based on wavelength conversion which will extend the spectral coverage of state of the art visible or near infrared cameras and spectrometers to include other spectral regions of interest.

  13. Determination of optical constants of zirconia and silica thin films in UV to visible range

    Science.gov (United States)

    Jin, Weihua; Jin, Chunshui; Zhu, Hongli; Liu, Lei; Yang, Huaijiang

    2007-12-01

    A curve fitting method for determining the optical constants of some dielectric thin films is described with dispersion theory in the paper. A computer program based on Matlab is developed and optimized. The fitting errors are analyzed with theoretical data, which gives very high accurate results. A program is applied to fitting the measured photometric spectra of ion sputtered zirconia and silica thin films in 200-850nm spectra range. The thickness is verified with the method of grazing x-ray diffraction. With the thickness known, the optical constants of zirconia films near the absorption range are obtained with single-wavelength method. As a result, quite good fitting results are obtained with high accuracy. Finally, an ultraviolet (UV) high-pass optical filter is designed with optical constants extracted by this method. The transmission and reflection spectra of the filter are measured and compared to designed spectra. A good coherence was derived.

  14. Large dynamic range SPR measurements in the visible using a ZnSe prism

    CERN Document Server

    Canning, John; Cook, Kevin

    2015-01-01

    Large dynamic index measurement range (n = 1 to n = 1.7) using surface plasmon resonance (SPR) shifts is demonstrated with a ZnSe prism at 632.8 nm, limited by the available high index liquid hosts. In contrast to borosilicate based SPR measurements where angular limitations restrict solvent use to water and requires considerable care dealing with Fresnel reflections, the ZnSe approach allows SPR spectroscopies to be applied to a varied range of solvents An uncertainty in angular resolution between 1.5 and 6 deg, depending on the solvent and SPR angle, was estimated. The refractive index change for a given glucose concentration in water was measured to be n = (0.114 to 0.007) per precentage C6H12O6 conc. Given the transmission properties of ZnSe the processes can be readily extended into the mid infrared.

  15. Scientometric analyses of the international visibility of German psychology researchers and their range of specialization

    OpenAIRE

    Fell, Clemens B.; Alexander von Eye; Gabriel Schui; Günter Krampen

    2012-01-01

    With reference to the role of networking, accelerated by current developments within large parts of the scientific community, the assumption is examined that the range of specialization of scientists in terms of membership in professional sections of scientific societies is related to the international impact of their publications. The sample consists of 2,788 German psychologists enrolled in the German Psychological Society (Deutsche Gesellschaft für Psychologie, DGPs). A log-linear model s...

  16. Direct milling and casting of polymer-based optical waveguides for improved transparency in the visible range

    Science.gov (United States)

    Snakenborg, D.; Perozziello, G.; Klank, H.; Geschke, O.; Kutter, J. P.

    2006-02-01

    Polymer waveguides fabricated from photoresist have an inherent high propagation loss in the short visible wavelength range caused by absorption due to the added photosensitizers. We have addressed this problem by development of two novel methods for the fabrication of microfluidic systems with integrated optical waveguides. Polymethylmethacrylate (PMMA) is dissolved in anisole and 'doped' with styrene-arcylonitrile copolymer to vary the refractive index. The doped PMMA with a higher refractive index is then spin coated onto a PMMA substrate with a lower refractive index to provide waveguide properties. Direct micromilling enabled us to fabricate 100 µm wide optical waveguides. Propagation losses of less than 1 dB cm-1 could be achieved throughout the entire visual range down to a wavelength of 400 nm. A casting process amenable to high number production of such devices was furthermore developed.

  17. Direct milling and casting of polymer-based optical waveguides for improved transparency in the visible range

    DEFF Research Database (Denmark)

    Snakenborg, Detlef; Perozziello, Gerardo

    2006-01-01

    Polymer waveguides fabricated from photoresist have an inherent high propagation loss in the short visible wavelength range caused by absorption due to the added photosensitizers. We have addressed this problem by development of two novel methods for the fabrication of microfluidic systems with integrated optical waveguides. Polymethylinethacrylate (PMMA) is dissolved in anisole and 'doped' with styrene-arcylonitrile copolymer to vary the refractive index. The doped PMMA with a higher refractive index is then spin coated onto a PMMA substrate with a lower refractive index to provide waveguide properties. Direct micromilling enabled us to fabricate 100 mu m wide optical waveguides. Propagation losses of less than 1 dB cm(-1) could be achieved throughout the entire visual range down to a wavelength of 400 nm. A casting process amenable to high number production of such devices was furthermore developed.

  18. Optical properties of human colon tissues in the 350 – 2500 nm spectral range

    Science.gov (United States)

    Bashkatov, A. N.; Genina, E. A.; Kochubey, V. I.; Rubtsov, V. S.; Kolesnikova, E. A.; Tuchin, V. V.

    2014-08-01

    We present the optical characteristics of the mucosa and submucosa of human colon tissue. The experiments are performed in vitro using a LAMBDA 950 spectrophotometer in the 350 – 2500 nm spectral range. The absorption and scattering coefficients and the scattering anisotropy factor are calculated based on the measured diffuse reflectance and total and collimated transmittance spectra using the inverse Monte Carlo method.

  19. Optical constants of ethylene glycol over an extremely wide spectral range

    Science.gov (United States)

    Sani, Elisa; Dell'Oro, Aldo

    2014-11-01

    Besides providing insights into the fundamental properties of materials, the knowledge of optical constants is required for a large variety of applications. In this work, for the first time to the best of our knowledge, an extremely wide spectral range from 181 to ?54,000 cm-1 has been explored for ethylene glycol in the liquid phase, and optical constants in the whole range have been given. The approach we propose can also be applied to different fluids.

  20. Spectral characteristics of precipitating electrons associated with visible aurora in the premidnight oval during periods of substorm activity

    International Nuclear Information System (INIS)

    Three late evening passes of the DMSP/F2 satellite over the northern auroral zone have been studied using simultaneous visible emissions and measurements from a zenith-looking, 16-channel, electron spectrometer. All three orbits occurred during periods of substorm activity; the second and third passes were consecutive. The auroral oval is conveniently divided into three latitudinal segments: a most pole-ward bright arc: a region of structured inverted-V precipitation; and the diffuse auroral region. The most poleward bright arc is characterized by directional fluxes occasionally in excess of 1010 (cm2s sr)-1 carried by two populations with temperatures of approx.100 eV and approx.600 eV. These fluxes, which apparently continue well into substorm recovery, are not easily reconciled with a simple model for pressure balance in the magnetotail. Presumably they reflect not well understood dynamic processes in the distant magnetotail. In the second regions precipitating electrons had average energies in excess of 1 keV and had spectral shapes that were either quasi-thermal or monoenergetic peaks superimposed on a secondary-electron background. Beams of low-energy (10 (cm2 sr keV)-1 were found in all three cases. We interpret these electrons as part of an originally cold plasma that became detached from the plasmasphere due to time-varying convective electric fields. The electrons were subsequently heated by the Landau damping of electromagnetic ion-cyclotron waves

  1. Intensity modulation photonic crystal fiber based refractometer in the visible wavelength range

    Science.gov (United States)

    Liu, Yun; Chen, Shimeng; Zhang, Xinpu; Gong, Zhenfeng; Peng, Wei

    2014-11-01

    A novel evanescent field refractometer based on a two-core photonic crystal fiber (TWPCF) sandwiched between multimode fibers(MMFs) is demonstrated. Through splicing a short piece of TWPCF between two MMFs, a simple structure and high sensitivity RI sensor can be constructed. Instead of using wavelength information as sensor signal, we focus more on the light intensity signal different from most PCF based RI sensor. The TWPCF section functions as a tailorable bridge between the excited high order modes and the surrounding refractive index (SRI). With a light filter inserting in the front of white light, the transmission spectrum of the light through the sensing region occurs in a welldefined wavelength bands. As a result, the peak power of the transmission light is tailored with the SRI perturbation via the MMF-TWPCF-MMF structure. The experiment result shows a quadratic relation between the light intensity and samples within RI range of 1.33-1.41 while a linear response can be achieved from the 1.33-1.35 which is a most used RI range for biologically sensing.

  2. Thin film photodetectors for the UV and vacuum UV spectral range

    Science.gov (United States)

    de Cesare, Giampiero; Irrera, Fernanda; Nicolosi, Piergiorgio

    1999-08-01

    We present the first semiconductor p-i-n photodiode with excellent sensitivity in the VUV range and high rejection of visible radiation. The device is based on the thin-film technology of amorphous silicon and silicon carbide and can be integrated in large area arrays on glass or flexible substrate. Its internal quantum efficiency is over 50 percent in the VUV and decreases with wavelength. In the visible range the sensitivity can be tuned by variations to the technology parameters. Solar blind photodiodes have been fabricated, with 1 percent quantum efficiency at 400 nm and 0.1 at 650 nm. Working bias voltage is very low since its best sensitivity is achieved when reversely biased with 0.3V. Linearity of the photocurrent was verified with incident UV light in the range 5nW to 4mW. Response times under UV illumination was tested with a N2 laser: 500 ns rise times and 6microsecond(s) FWHM were measured. The excellent behavior of the photodetector in the UV range was explained in the UV range was explained within the hypotheses that generation of hot carriers in the p-doped layer occurs and that a pure diffusion mechanism rules transport, being the thickness of the p-doped layer comparable with the effective diffusion length of electrons.

  3. Radiometric calibration of optical microscopy and microspectroscopy apparata over a broad spectral range using a special thin-film luminescence standard

    Directory of Open Access Journals (Sweden)

    J. Valenta

    2015-04-01

    Full Text Available Application capabilities of optical microscopes and microspectroscopes can be considerably enhanced by a proper calibration of their spectral sensitivity. We propose and demonstrate a method of relative and absolute calibration of a microspectroscope over an extraordinary broad spectral range covered by two (parallel detection branches in visible and near-infrared spectral regions. The key point of the absolute calibration of a relative spectral sensitivity is application of the standard sample formed by a thin layer of Si nanocrystals with stable and efficient photoluminescence. The spectral PL quantum yield and the PL spatial distribution of the standard sample must be characterized by separate experiments. The absolutely calibrated microspectroscope enables to characterize spectral photon emittance of a studied object or even its luminescence quantum yield (QY if additional knowledge about spatial distribution of emission and about excitance is available. Capabilities of the calibrated microspectroscope are demonstrated by measuring external QY of electroluminescence from a standard poly-Si solar-cell and of photoluminescence of Er-doped Si nanocrystals.

  4. Comprehensive polarimetric analysis of Spectralon white reflectance standard in a wide visible range.

    Science.gov (United States)

    Sanz, J M; Extremiana, C; Saiz, J M

    2013-08-20

    Since polarimetry has extended its use for the study of scattering from surfaces and tissues, Spectralon, a white reflectance standard, is acquiring the role of a polarimetric standard. Both the behavior of Spectralon as a Lambertian surface and its performance as a perfect depolarizer are analyzed in detail. The accuracy of our dynamic polarimeter, together with the polar decomposition to describe the Mueller matrix (MM) depolarizing action, combine to produce a powerful tool for the proper analysis of this scattering surface. Results allowed us to revisit, for confirmation or revision, the role of some MM elements, as described in the bibliography. The conditions under which it can be considered a good Lambertian surface are specified in terms of incidence and scattering angle and verified over a large wavelength range. PMID:24085010

  5. The PTB high-accuracy spectral responsivity scale in the VUV and x-ray range

    Science.gov (United States)

    Gottwald, A.; Kroth, U.; Krumrey, M.; Richter, M.; Scholze, F.; Ulm, G.

    2006-04-01

    At the electron storage ring BESSY II, the Physikalisch-Technische Bundesanstalt operates ten experimental stations at six synchrotron radiation beamlines for photon metrology in the spectral range from ultraviolet radiation to x-rays. Five of these beamlines are used to realize and disseminate a scale of spectral responsivity for photodetectors. Detector calibration is based on the use of cryogenic radiometers as primary detector standards. The current status of instrumentation and measurement capabilities is described. Best measurement capabilities (k = 2) for the calibration of photodiodes vary between 0.4% and 2.3%.

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

    International Nuclear Information System (INIS)

    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

  7. Fluorescent dye labeled DNA size standards for molecular mass detection in visible/infrared range

    Directory of Open Access Journals (Sweden)

    Sreelakshmi Yellamaraju

    2011-01-01

    Full Text Available Abstract Background Targeting Induced Local Lesions in Genomes (TILLING is a high throughput reverse genetics tool which detects mismatches (single point mutations or small indels in large number of individuals of mutagenized populations. Currently, TILLING is intensively used for genomics assisted molecular breeding of several crop plants for desired traits. Most commonly used platform for mutation detection is Li-COR DNA Analyzer, where PCR amplified products treated with single strand mismatch specific nuclease are resolved on denaturing gels. The molecular size of any cut product can be easily estimated by comparing with IR dye labeled markers of known sizes. Similar fluorescent dye labeled size markers are also used for several genotyping experiments. Currently, commercially available size standards are expensive and are restricted up to only 700 bp which renders estimation of products of sizes greater than 700 bases inaccurate. Findings A simple protocol was developed for labeling 5' end of multiple DNA size markers with fluorescent dyes. This method involves cloning a pool of different size markers of DNA in a plasmid vector. PCR amplification of plasmid using IR dye labeled universal primers generates 5' fluorescent labeled products of various sizes. The size of products constituting the ladder can be customized as per the need. The generated size markers can be used without any further purification and were found to be stable up to one year at -20°C. Conclusions A simple method was developed for generating fluorescent dye labeled size standards. This method can be customized to generate different size standards as per experimental needs. The protocol described can also be adapted for developing labeled size standards for detection on platforms other than Li-COR i.e. other than infra red range of the spectrum.

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

    Energy Technology Data Exchange (ETDEWEB)

    Murr, Patrik J., E-mail: patrik.murr@tum.de; Rauscher, Markus S.; Tremmel, Anton; Schardt, Michael; Koch, Alexander W. [Institute for Measurement Systems and Sensor Technology, Technische Universität München, Theresienstraße 90, 80333 München (Germany)

    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.

  9. Aerosol retrieval from multiangle multispectral photopolarimetric measurements: importance of spectral range and angular resolution

    Science.gov (United States)

    Wu, L.; Hasekamp, O.; van Diedenhoven, B.; Cairns, B.

    2015-03-01

    We investigated the importance of spectral range and angular resolution for aerosol retrieval from multi-angle photo-polarimetric measurements over land. For this purpose, we use an extensive set of simulated measurements for different spectral ranges and angular resolutions and subsets of real measurements of the airborne Research Scanning Polarimeter (RSP) carried out during the PODEX and SEAC4RS campaigns over continental US. Aerosol retrievals performed from RSP measurements show good agreement with ground based AERONET measurements for AOT, SSA, and refractive index. Furthermore, we found that inclusion of shortwave infrared bands (1590 and/or 2250 nm) significantly improves the retrieval of AOT, SSA and coarse mode microphysical properties. On the other hand, retrieval accuracies on aerosol properties do not improve significantly if more than 10 viewing angles are used in the retrieval.

  10. Spectral characteristics of precipitating clouds during the Meiyu over the Yangtze-Huaihe River Valley from merged TRMM precipitation radar and visible/infrared scanner data

    Science.gov (United States)

    Yang, Yuan-Jian; Fu, Yun-Fei; Chen, Feng-Jiao; Zheng, Xiao-Yi; Chen, Yi-Lun

    2014-11-01

    As the similar cross track scanning mode of the measurements of Tropical Rainfall Measuring Mission's (TRMM) Precipitation Radar (PR) and visible and infrared scanner (VIRS) results in near instantaneous synchronization in observing the same target, it is feasible to jointly use these two measurements to explore exactly the spectral characteristics of precipitating clouds (PCs). Meanwhile, it will effectively improve and extend the abilities to identify PCs using visible/infrared (VIR) measurements, because VIR sensors can be loaded aboard geostationary satellites with the opportunity of high sampling frequency. In this paper, PR and VIRS onboard TRMM are respectively used to capture PCs and identify their spectral signals during the Meiyu over the Yangtze-Huaihe River Valley from 1998 to 2007. Visible/infrared signals for PCs, which are the reflectance at 0.63?m and 1.6?m (referred to as RF1 and RF2, respectively), and the equivalent brightness temperature of a blackbody at 3.7?m, 10.8 ?m and 12.0?m (referred to as TB3, TB4 and TB5, respectively), were derived by TRMM VIRS. Firstly, characteristics of rain rate, rain top and vertical profiles for stratiform and convective precipitations are investigated during the Meiyu periods. Moreover, VIRS individual-channel signals, and multi-channel indices for PCs of the Meiyu are evaluated quantitatively. Finally, revealed by long-term mean values, the differences of spectral signals between stratiform and convective PCs and their relationships with surface rain rates are explored.

  11. Spectral distribution of UV range diffuse reflectivity for Si+ ion implanted polymers

    International Nuclear Information System (INIS)

    The analysis of the UV range spectral characteristics can supply additional information on the formed sub-surface buried layer with implanted dopants. The near-surface layer (50 to 150 nm) of bulk polymer samples have been implanted with silicon (Si+) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 1.1013 to 1, 2.1017 cm-2). The studied polymer materials were: ultra-high-molecular-weight polyethylene (UHMWPE), poly-methyl-metacrylate (PMMA) and poly-tetra-fluor-ethylene (PTFE). The diffuse optical reflectivity spectra Rd = f(?) of the ion implanted samples have been measured in the UV range (? = 220 to 350 nm). In this paper the dose dependences of the size and sign of the diffuse optical reflectivity changes ?Rd = f(D) have been analysed

  12. Infrared absolute intensities of ozone in the 10 and 5 ?m spectral range: New investigations

    International Nuclear Information System (INIS)

    Infrared high resolution spectra of ozone 16O3 have been recorded in the 10 and 5 ?m spectral ranges in order to derive their absolute intensities with a best achievable accuracy. Spectra have been recorded with the home made stepping mode FTS of GSMA (Reims). In the two spectral regions, we use UV-IR crossed beam cell. The quantification of ozone is achieved using UV cross section at 253.65 nm. A check of this UV calibration is also performed using direct pressure measurements of quasi-pure samples of O3. The intensities are derived from infrared spectra using multifit procedure already tested. In the 10 ?m range, where 12 different spectra have been recorded, 65 well selected lines led to a good agreement (better than 0.3%) with the HITRAN 2008 (or 2004) values, confirming our previous work [De Backer-Barilly MR, Barbe A. Absolute intensities of the 10 ?m bands of 16O3. J Mol Spectrosc 305:2001;43-53]. In the 5 ?m range, where 18 transitions are selected, we also note a correct agreement with HITRAN 2008, despite a slightly larger averaged value between (1.9%) experimental and theoretical (HITRAN). As conclusion, authors suggest the use of current HITRAN 2008 data for atmospheric retrievals.

  13. Pulsed, all solid-state light source in the visible spectral region based on non-linear cavity dumping

    DEFF Research Database (Denmark)

    Tidemand-Lichtenberg, Peter; Andersen, Martin

    We propose a novel generic approach for generation of pulsed light in the visible spectrum, based on SFG between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser.

  14. Low threshold, room-temperature microdisk lasers in the blue spectral range

    CERN Document Server

    Aharonovich, Igor; Russell, Kasey J; Zhu, Tongtong; Kappers, Menno J; Oliver, Rachel A; Hu, Evelyn L

    2012-01-01

    InGaN-based active layers within microcavity resonators offer the potential of low threshold lasers in the blue spectral range. Here we demonstrate optically pumped, room temperature lasing in high quality factor GaN microdisk cavities containing InGaN quantum dots (QDs) with thresholds as low as 0.28 mJ/cm2. This work, the first demonstration of lasing action from GaN microdisk cavities with QDs in the active layer, provides a critical step for the nitrides in realizing low threshold photonic devices with efficient coupling between QDs and an optical cavity.

  15. Model-Independent Sum Rule Analysis Based on Limited-Range Spectral Data

    CERN Document Server

    Kuzmenko, A B; Carbone, F; Marsiglio, F

    2007-01-01

    Partial sum rules are widely used in physics to separate low- and high-energy degrees of freedom of complex dynamical systems. Their application, though, is challenged in practice by the always finite spectrometer bandwidth and is often performed using risky model-dependent extrapolations. We show that, given spectra of the real and imaginary parts of any causal frequency-dependent response function (for example, optical conductivity, magnetic susceptibility, acoustical impedance etc.) in a limited range, the sum-rule integral from zero to a certain cutoff frequency inside this range can be safely derived using only the Kramers-Kronig dispersion relations without any extra model assumptions. This implies that experimental techniques providing both active and reactive response components independently, such as spectroscopic ellipsometry in optics, allow an extrapolation-independent determination of spectral weight 'hidden' below the lowest accessible frequency.

  16. Model-independent sum rule analysis based on limited-range spectral data

    International Nuclear Information System (INIS)

    Partial sum rules are widely used in physics to separate low- and high-energy degrees of freedom of complex dynamical systems. Their application, though, is challenged in practice by the always finite spectrometer bandwidth and is often performed using risky model-dependent extrapolations. We show that, given spectra of the real and imaginary parts of any causal frequency-dependent response function (for example, optical conductivity, magnetic susceptibility, acoustical impedance etc) in a limited range, the sum-rule integral from zero to a certain cutoff frequency inside this range can be safely derived using only the Kramers-Kronig dispersion relations without any extra model assumptions. This implies that experimental techniques providing both active and reactive response components independently, such as spectroscopic ellipsometry in optics, allow an extrapolation-independent determination of spectral weight 'hidden' below the lowest accessible frequency

  17. A Determination of the Spectral Index of Galactic Synchrotron Emission in the 1 - 10 GHz Range

    International Nuclear Information System (INIS)

    We present an analysis of simultaneous multifrequency measurements of the Galactic emission in the 1 - 10 GHz range with 18 degree angular resolution taken from a high-altitude site. Our data yield a determination of the synchrotron spectral index between 1.4 and 7.5 GHz of ?syn=2.81 ± 0.16. Combining our data with maps made by Haslam et al. and Reich and Reich, we find ?syn=2.76 ± 0.11 in the 0.4 - 7.5 GHz range. These results are in agreement with the few previously published measurements. The variation of ?syn with frequency based on our results and compared with other data found in the literature suggests a steepening of the synchrotron spectrum toward high frequencies, as expected from theory because of the steepening of the parent cosmic-ray electron energy spectrum. Comparison between the Haslam data and the 19 GHz map of Cottingham also indicates a spatial variation of the spectral index on large angular scales. Additional high-quality data are necessary to provide a serious study of these effects. copyright copyright 1998. The American Astronomical Society

  18. Optical performance of B-layer ultra-shallow-junction silicon photodiodes in the VUV spectral range:

    OpenAIRE

    L. Shi; Sarubbi, F.; Nanver, L. K.; Kroth, U.; Gottwald, A.; Nihtianov, S.

    2010-01-01

    In recent work, a novel silicon-based photodiode technology was reported to be suitable for producing radiation detectors for 193 nm deep-ultraviolet light and for the extreme-ultraviolet (EUV) spectral range. The devices were developed and fabricated at the Delft Institute of Microsystems and Nanoelectronics (DIMES), TU Delft. In this paper, we characterize the optical performance of the DIMES photo-detectors in the vacuum-ultraviolet (VUV) spectral range, in particular between 115 nm and 21...

  19. A full free spectral range tuning of p-i-n doped Gallium Nitride microdisk cavity

    CERN Document Server

    Niu, Nan; Aharonovich, Igor; Russell, Kasey J; Woolf, Alexander; Sadler, Thomas C; El-Ella, Haitham A R; Kappers, Menno J; Oliver, Rachel A; Hu, Evelyn L

    2012-01-01

    Effective, permanent tuning of the whispering gallery modes (WGMs) of p-i-n doped GaN microdisk cavity with embedded InGaN quantum dots over one free spectral range is successfully demonstrated by irradiating the microdisks with a ultraviolet laser (380nm) in DI water. For incident laser powers between 150 and 960 nW, the tuning rate varies linearly. Etching of the top surface of the cavity is proposed as the driving force for the observed shift in WGMs, and is supported by experiments. The tuning for GaN/InGaN microdisk cavities is an important step for deterministically realizing novel nanophotonic devices for studying cavity quantum electrodynamics.

  20. Circuit model optimization of a nano split ring resonator dimer antenna operating in infrared spectral range

    Energy Technology Data Exchange (ETDEWEB)

    Gneiding, N., E-mail: Natalia.Gneiding@physik.uni-erlangen.de [Erlangen Graduate School in Advanced Optical Technologies (SAOT), University of Erlangen-Nuremberg, 91052 Erlangen (Germany); Zhuromskyy, O.; Peschel, U. [Institute of Optics, Information and Photonics, University of Erlangen-Nuremberg, 91058 Erlangen (Germany); Shamonina, E. [Department of Engineering Science, University of Oxford, Parks Road, OX1 3PJ Oxford (United Kingdom)

    2014-10-28

    Metamaterials are comprised of metallic structures with a strong response to incident electromagnetic radiation, like, for example, split ring resonators. The interaction of resonator ensembles with electromagnetic waves can be simulated with finite difference or finite elements algorithms, however, above a certain ensemble size simulations become inadmissibly time or memory consuming. Alternatively a circuit description of metamaterials, a well developed modelling tool at radio and microwave frequencies, allows to significantly increase the simulated ensemble size. This approach can be extended to the IR spectral range with an appropriate set of circuit element parameters accounting for physical effects such as electron inertia and finite conductivity. The model is verified by comparing the coupling coefficients with the ones obtained from the full wave numerical simulations, and used to optimize the nano-antenna design with improved radiation characteristics.

  1. Complex Refractive Index of Ammonium Nitrate in the 2-20 micron Spectral Range

    Science.gov (United States)

    Jarzembski, Maurice A.; Norman, Mark L.; Fuller, Kirk A.; Srivastava, Vandana; Cutten, Dean R.

    2002-01-01

    Using high resolution Fourier Transform Infrared Spectroscopy (FTIR) absorbance/transmittance spectral data for ammonium sulfate (AMS), calcium carbonate (CAC) and ammonium nitrate (AMN), comparisons were made with previously published complex refractive indices data for AMS and CAC to infer experimental parameters to determine the imaginary refractive index for AMN in the infrared wavelength range from 2 to 20 microns. Kramers-Kronig mathematical relations were applied to calculate the real refractive index for the three compositions. Excellent agreement for AMS and CAC with the published values was found, validating the complex refractive indices obtained for AMN. Backscatter calculations using a lognormal size distribution for AMS, AMN, and CAC aerosols were performed to show differences in their backscattered spectra.

  2. Optically visible post-AGB/RGB stars and young stellar objects in the Small Magellanic Cloud: candidate selection, spectral energy distributions and spectroscopic examination

    CERN Document Server

    Kamath, D; Van Winckel, H

    2014-01-01

    We have carried out a search for optically visible post-AGB candidates in the Small Magellanic Cloud (SMC). We used mid-IR observations from the Spitzer Space Telescope to select optically visible candidates with a mid-IR excess. We obtained low-resolution optical spectra for 801 candidates. After removing contaminants and poor quality spectra, the final sample comprised of 63 post-AGB/RGB candidates of A - F spectral type. Using the spectra, we estimated the stellar parameters: effective temperature, surface gravity and [Fe/H]. We also estimated the reddening and deduced the luminosity using the stellar parameters combined with photometry. Based on a luminosity criterion, 42 of these 63 sources were classified as post-RGB candidates and the remaining as post-AGB candidates. From the spectral energy distributions we found that 6 of the 63 post-AGB/RGB candidates have a circumstellar shell suggesting that they are single stars, while 27 of them have a surrounding disc, suggesting that they are binaries. For th...

  3. Natural variability of bio-optical properties in Case 1 waters: attenuation and reflectance within the visible and near-UV spectral domains, as observed in South Pacific and Mediterranean waters

    Directory of Open Access Journals (Sweden)

    A. Morel

    2007-07-01

    Full Text Available The optical properties of Case 1 waters have been empirically related to the chlorophyll concentration, [Chl], historically used as an index of the trophic state and of the abundance of the biological materials. The natural variability around the mean statistical relationships is here examined by comparing the apparent optical properties (spectral downward irradiance attenuation and reflectance as a function of [Chl] which were determined in two environments, the Pacific and Mediterranean waters. These oceanic zones apparently form two extremes of the bio-optical variability range. The systematic deviations, in both directions with respect to the average laws, mainly result from the differing contents in non-algal detrital materials and dissolved colored substance for a given [Chl] level. These contents are higher and lower than the average, in the Mediterranean Sea and Pacific Ocean, respectively. The divergences between the two water bodies, detected in the visible spectral domain, are considerably accentuated in the UV domain. The bio-optical properties in this spectral domain (310–400 nm are systematically explored. Their prediction based on the sole [Chl] index is problematic; although it is probably possible on a regional scale, an ubiquitous relationship does not seem to exist for the global scale.

  4. Retrieval interval mapping, a tool to optimize the spectral retrieval range in differential optical absorption spectroscopy

    Directory of Open Access Journals (Sweden)

    L. Vogel

    2012-06-01

    Full Text Available Remote sensing via differential optical absorption spectroscopy (DOAS has become a standard technique to identify and quantify trace gases in the atmosphere. The technique is applied in a variety of configurations, commonly classified into active and passive instruments using artificial and natural light sources, respectively. Platforms range from ground based to satellite instruments and trace-gases are studied in all kinds of different environments. Due to the wide range of measurement conditions, atmospheric compositions and instruments used, a specific challenge of a DOAS retrieval is to optimize the parameters for each specific case and particular trace gas of interest. This becomes especially important when measuring close to the detection limit.

    A well chosen evaluation wavelength range is crucial to the DOAS technique. It should encompass strong absorption bands of the trace gas of interest in order to maximize the sensitivity of the retrieval, while at the same time minimizing absorption structures of other trace gases and thus potential interferences. Also, instrumental limitations and wavelength depending sources of errors (e.g. insufficient corrections for the Ring effect and cross correlations between trace gas cross sections need to be taken into account. Most often, not all of these requirements can be fulfilled simultaneously and a compromise needs to be found depending on the conditions at hand.

    Although for many trace gases the overall dependence of common DOAS retrieval on the evaluation wavelength interval is known, a systematic approach to find the optimal retrieval wavelength range and qualitative assessment is missing. Here we present a novel tool to determine the optimal evaluation wavelength range. It is based on mapping retrieved values in the retrieval wavelength space and thus visualize the consequence of different choices of retrieval spectral ranges, e.g. caused by slightly erroneous absorption cross sections, cross correlations and instrumental features.

    The technique is demonstrated using the examples of a theoretical study of BrO retrievals for stratospheric BrO measurements and for BrO measurements in volcanic plumes. However, due to the general nature of the tool, it is applicable to any type (active or passive of DOAS retrieval.

  5. Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS) in the red spectral range

    OpenAIRE

    T. Wagner; Beirle, S.; T. Deutschmann; Grzegorski, M.; Platt, U (Ulrich)

    2007-01-01

    A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm) reflectance structures (i.e. "fingerprint" structures) of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS), which is usually applied for the anal...

  6. Effect of iron impurities on the photoluminescence and photoconductivity of ZnSe crystals in the visible spectral region

    International Nuclear Information System (INIS)

    The photoconductivity and photoluminescence of ZnSe:Fe crystals in the visible spectra region are studied. The scheme of optical transitions within Fe2+ impurity centers is established. It is shown that the high-temperature photoconductivity of ZnSe:Fe crystals is controlled by optical transitions of electrons from the 5E(F) ground state to the higher levels of excited states of Fe2+ ions, with subsequent thermal activation of the electrons to the conduction band. Efficient excitation of intracenter luminescence of ZnSe:Fe crystals is attained with light corresponding to the region of intrinsic absorption in Fe2+ ions.

  7. Wave chaos in a randomly inhomogeneous waveguide: spectral analysis of the finite-range evolution operator.

    Science.gov (United States)

    Makarov, D V; Kon'kov, L E; Uleysky, M Yu; Petrov, P S

    2013-01-01

    The problem of sound propagation in a randomly inhomogeneous oceanic waveguide is considered. An underwater sound channel in the Sea of Japan is taken as an example. Our attention is concentrated on the domains of finite-range ray stability in phase space and their influence on wave dynamics. These domains can be found by means of the one-step Poincare map. To study manifestations of finite-range ray stability, we introduce the finite-range evolution operator (FREO) describing transformation of a wave field in the course of propagation along a finite segment of a waveguide. Carrying out statistical analysis of the FREO spectrum, we estimate the contribution of regular domains and explore their evanescence with increasing length of the segment. We utilize several methods of spectral analysis: analysis of eigenfunctions by expanding them over modes of the unperturbed waveguide, approximation of level-spacing statistics by means of the Berry-Robnik distribution, and the procedure used by A. Relano and coworkers [Relano et al., Phys. Rev. Lett. 89, 244102 (2002); Relano, Phys. Rev. Lett. 100, 224101 (2008)]. Comparing the results obtained with different methods, we find that the method based on the statistical analysis of FREO eigenfunctions is the most favorable for estimating the contribution of regular domains. It allows one to find directly the waveguide modes whose refraction is regular despite the random inhomogeneity. For example, it is found that near-axial sound propagation in the Sea of Japan preserves stability even over distances of hundreds of kilometers due to the presence of a shearless torus in the classical phase space. Increasing the acoustic wavelength degrades scattering, resulting in recovery of eigenfunction localization near periodic orbits of the one-step Poincaré map. PMID:23410408

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

    Science.gov (United States)

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

    2011-03-10

    A full-bandwidth k-domain linearization method for spectral-domain optical coherence tomography (SD-OCT) is demonstrated. The method uses information of the wavenumber-pixel-position provided by a translating-slit-based wavelength filter. For calibration purposes, the filter is placed either after a broadband source or at the end of the sample path, and the filtered spectrum with a narrowed line width (?0.5?nm) is incident on a line-scan camera in the detection path. The wavelength-swept spectra are co-registered with the pixel positions according to their central wavelengths, which can be automatically measured with an optical spectrum analyzer. For imaging, the method does not require a filter or a software recalibration algorithm; it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. The accuracy of k-linearization is maximized by increasing the k-linearization order, which is known to be a crucial parameter for maintaining a narrow point-spread function (PSF) width at increasing depths. The broadening effect is studied by changing the k-linearization order by undersampling to search for the optimal value. The system provides more position information, surpassing the optimum without compromising the imaging speed. The proposed full-range k-domain linearization method can be applied to SD-OCT systems to simplify their hardware/software, increase their speed, and improve the axial image resolution. The experimentally measured width of PSF in air has an FWHM of 8??m at the edge of the axial measurement range. At an imaging depth of 2.5?mm, the sensitivity of the full-range calibration case drops less than 10?dB compared with the uncompensated case. PMID:21394187

  9. Fast and enhanced broadband photoresponse of a ZnO nanowire array/reduced graphene oxide film hybrid photodetector from the visible to the near-infrared range.

    Science.gov (United States)

    Liu, Hao; Sun, Qi; Xing, Jie; Zheng, Zhiyuan; Zhang, Zhili; Lü, Zhiqing; Zhao, Kun

    2015-04-01

    In the present work, a ZnO nanowire array/reduced graphene oxide film hybrid nanostructure was realized, and the photovoltaic responses from the visible to the near-infrared range were investigated. Compared with the pure ZnO nanowire array and rGO thin film, the hybrid composite exhibited a fast and greatly enhanced broadband photovoltaic response that resulted from the formation of interfacial Schottky junctions between ZnO and rGO. PMID:25768384

  10. Estudio de la respuesta espectral en el visible de películas delgadas de ZnSe / Study of the Spectral Response in the Visible Spectral Region the ZnSe thin Films

    Scientific Electronic Library Online (English)

    A, Pardo; H.G, Castro-Lora; J, Torres; L.D, López-Carreño; H. M, Martínez; N. T, Ramírez.

    2014-07-30

    Full Text Available En este trabajo es presentado el estudio de la fotoconductividad en películas delgadas de ZnSe depositadas sobre sustratos de vidrio a diferentes temperaturas, en condiciones de alto vacío usando la técnica de evaporación térmica. El efecto de la temperatura de sustrato sobre la fotoconductividad es [...] pectral y las propiedades morfológicas de las películas delgadas de ZnSe fueron estudiados. Para las medidas de fotoconductividad se depositaron contactos de cobre sobre las muestras. Se midieron las respuestas espectrales para las muestras para el rango comprendido entre 290 y 500 nm. En todas las muestras la señal presento dos contribuciones asociadas a las transiciones con valores promedio de energía de 3,35 y 2,80 eV, respectivamente. El tiempo de respuesta de las muestras está asociado a la morfología de la muestras. En las muestras preparadas a bajas temperaturas se obtuvieron tiempos de respuesta del orden de los segundos, mientras que, el tiempo disminuye en un orden de magnitud en las muestras preparadas a temperatura de sustrato de 250°C. Abstract in english In this work are presented results in the study of photoconductivity of ZnSe thin films deposited on glass substrate. The effect of substrate temperature on the spectral photoconductivity and morphological properties of ZnSe thin films were studied. The Spectral response appeared between 290 and 500 [...] nm. In the spectral responses were found two contributions associated with transitions labeled , with energy values of 3:35 and 2:80 eV, respectively. The response time of the sample is associated with the morphology of the samples. In the samples prepared at lower temperatures were obtained response times on the order of seconds, whereas the time decreases by one magnitude order in the samples prepared at the substrate temperature of 250°C.

  11. High-power metal halide vapour lasers oscillating in deep ultraviolet, visible and middle infrared spectral ranges

    Science.gov (United States)

    Temelkov, K. A.; Slaveeva, S. I.; Kirilov, V. I.; Kostadinov, I. K.; Vuchkov, N. K.

    2012-05-01

    Middle infrared and deep ultraviolet high-power high-beam-quality stable-operating He-SrBr2 and Cu+ Ne-CuBr lasers excited in nanosecond pulsed longitudinal discharge are developed, patented and studied. Optimal discharge conditions, such as active zone diameter, vapour pressure, buffer-gas pressure, electrical excitation scheme parameters, average input power and pulse repetition frequency, are found. The highest output laser parameters are obtained for the Sr atom and Cu+ lasers, respectively. These lasers equipped with optical systems for the control of laser radiation parameters are used in a large variety of applications, such as precise material microprocessing, including biological tissues, determination of linear optical properties of different newly developed materials, laser-induced modification of conductive polymers and laser-induced fluorescence in wide-gap semiconductors, instead of free electron and excimer lasers, respectively. A master oscillator-power amplifier system, which is based on a high-beam-quality high-power CuBr vapour laser and is equipped with an optic system for laser beam control and with the X-Y stage controlled by adequate software as well, is developed and used in high-precision micromachining of samples made of nickel and tool steel.

  12. High-power metal halide vapour lasers oscillating in deep ultraviolet, visible and middle infrared spectral ranges

    International Nuclear Information System (INIS)

    Middle infrared and deep ultraviolet high-power high-beam-quality stable-operating He-SrBr2 and Cu+ Ne-CuBr lasers excited in nanosecond pulsed longitudinal discharge are developed, patented and studied. Optimal discharge conditions, such as active zone diameter, vapour pressure, buffer-gas pressure, electrical excitation scheme parameters, average input power and pulse repetition frequency, are found. The highest output laser parameters are obtained for the Sr atom and Cu+ lasers, respectively. These lasers equipped with optical systems for the control of laser radiation parameters are used in a large variety of applications, such as precise material microprocessing, including biological tissues, determination of linear optical properties of different newly developed materials, laser-induced modification of conductive polymers and laser-induced fluorescence in wide-gap semiconductors, instead of free electron and excimer lasers, respectively. A master oscillator-power amplifier system, which is based on a high-beam-quality high-power CuBr vapour laser and is equipped with an optic system for laser beam control and with the X-Y stage controlled by adequate software as well, is developed and used in high-precision micromachining of samples made of nickel and tool steel.

  13. Characterization of spectral hole depth in Tm3+:YAG within the cryogenic temperature range

    International Nuclear Information System (INIS)

    In this paper, spectral hole depth dependence on temperature below 10 K in Tm3+:YAG crystal is investigated in detail. A novel model is proposed to analyze the temperature dependence on the spectral hole. By using the proposed model, we theoretically deduce the temperature dependence of spectral hole depth. The results are compared with experimental results and they are in good agreement. According to the theoretic results, the optimum temperature in experiment can be found

  14. Spectral Characteristics of Vegetation Functional Traits across a Range of Thaw Gradients on Alaska's Seward Peninsula

    Science.gov (United States)

    Goswami, S.; Hayes, D. J.; Sloan, V. L.; Liebig, J. A.; Norby, R. J.; Wullschleger, S. D.

    2014-12-01

    The Arctic and Boreal regions are warming rapidly, leading to the thawing of the underlying permafrost and associated changes in vegetation structure and composition. The thawing of ice-rich permafrost drives land surface dynamics called thermokarst, characterized by a variety of geomorphic surface features across high latitude landscapes. The development of these thermokarst or thermo-erosional features depends on factors such as local permafrost conditions, hydrology, geomorphology, vegetation, and climate, but their degree of dependence are not well understood across scales. The structure, functions and traits of the vegetation can work as effective indicators of these landscape changes. Our ability to characterize these vegetation characteristics across a wide range of thaw gradients at the local scale could help us to better understand the dependency as well as the impacts of thermokarst processes on them. This will also help us to develop capabilities to quantify these characteristics and dependencies from local to regional scales by using remote sensing and ecosystem modeling techniques. During the months of June - July of 2013 and 2014, we conducted field surveys at various sites across the central Seward Peninsula in Alaska covering a range of thaw gradients to collect data for vegetation functional traits, ancillary data and also hyperspectral data in the 400-2500 nm range using a field spectrometer. Data were collected from plots established along 50 m transects to capture transitional states of these thaw features from the upland zone, transition zone, and thaw lake basins as well as in polygonal features. Here we discuss the characteristics of vegetation functional traits and how they relate to the ground-based spectral measurements. Some of these findings could be scaled up using airborne and satellite remote sensing data. The findings from this study can improve our understanding of disturbance patterns and their feedbacks to local scale plant and soil dynamics. Scaling up our understanding based on multi-scale remote sensing and ecosystem models over multiple spatial and temporal scales across landscapes could help us reduce uncertainties in estimating the carbon budget from local to pan-arctic scales.

  15. Spectral synthesis provides 2-D videos on a 1-D screen with 360{\\deg}-visibility and mirror-immunity

    CERN Document Server

    Grusche, Sascha

    2014-01-01

    Spatial-light-modulator (SLM)-based tunable sources have complex setups. A simpler setup, comprising an SLM-projector and a dispersive element, synthesizes light as effectively, based on a Superposition of Newtonian Spectra (SNS). As a generalization of SNS, two-dimensional (2-D) grayscale videos are spectrally encoded on a one-dimensional (1-D), translucent screen, and viewed through another dispersive element. This Projected-Image Circumlineascopy (PICS) produces semitransparent, rainbow-coloured, virtual 2-D videos that face every viewer anywhere around the 1-D screen. They are invariant under reflection of the 1-D screen in mirrors parallel to it. SNS bandwidth and PICS image geometry are calculated using geometric optics and Dispersion Diagrams.

  16. Third-harmonic generation with a more than 500?nm tunable spectral range in a step-index tellurite fiber

    International Nuclear Information System (INIS)

    We demonstrate third-harmonic generation (THG) with a tunable spectral range of more than 500?nm in a step-index tellurite fiber. Third-harmonic (TH) signals with a peak wavelength from 524 to 1043?nm are obtained in a 3?cm-long fiber when the fundamental wavelength shifts from 1560 to 3100?nm. To our knowledge, the tunable spectral range covering almost one octave is the widest tunable range of THG in fibers so far. The far-field patterns of the TH signals by 1560?nm to 2100?nm pumping are recorded by a charge coupled device camera, which are close to the fundamental mode profile. The THG in such a wide tunable range is attributable to the high nonlinearity of the tellurite fiber and the high pump peak power of the pump pulse. (letters)

  17. Portable PVS-02 spectrometer for transfer of the spectral radiance scale in the 0.4-2.5 ?m range

    Science.gov (United States)

    Belyaev, Yu. V.; Rogovets, A. V.; Khomitsevich, A. D.; Tsikman, I. M.

    2010-11-01

    We describe selection of an optical layout and calculation of the spectral sensitivity and measurement uncertainty in a portable spectrometer. The spectrometer is used for transfer of the brightness scale in the 0.4-2.5 ?m range from one brightness reference standard to another.

  18. A fast radiative transfer model for visible through shortwave infrared spectral reflectances in clear and cloudy atmospheres

    International Nuclear Information System (INIS)

    A computationally efficient radiative transfer model (RTM) for calculating visible (VIS) through shortwave infrared (SWIR) reflectances is developed for use in satellite and airborne cloud property retrievals. The full radiative transfer equation (RTE) for combinations of cloud, aerosol, and molecular layers is solved approximately by using six independent RTEs that assume the plane-parallel approximation along with a single-scattering approximation for Rayleigh scattering. Each of the six RTEs can be solved analytically if the bidirectional reflectance/transmittance distribution functions (BRDF/BTDF) of the cloud/aerosol layers are known. The adding/doubling (AD) algorithm is employed to account for overlapped cloud/aerosol layers and non-Lambertian surfaces. Two approaches are used to mitigate the significant computational burden of the AD algorithm. First, the BRDF and BTDF of single cloud/aerosol layers are pre-computed using the discrete ordinates radiative transfer program (DISORT) implemented with 128 streams, and second, the required integral in the AD algorithm is numerically implemented on a twisted icosahedral mesh. A concise surface BRDF simulator associated with the MODIS land surface product (MCD43) is merged into a fast RTM to accurately account for non-isotropic surface reflectance. The resulting fast RTM is evaluated with respect to its computational accuracy and efficiency. The simulation bias between DISORT and the fast RTM is large (e.g., relative error >5%) only when both the solar zenith angle (SZA) and the viewing zenith angle (VZA) are large (i.e., SZA>45° and VZA>70°). For general situations, i.e., cloud/aerosol layers above a non-Lambertian surface, the fast RTM calculation rate is faster than that of the 128-stream DISORT by approximately two orders of magnitude. -- Highlights: ? An efficient radiative transfer model is developed for cloud remote sensing. ? Multi-layered clouds and a non-Lambertian surface can be fully considered. ? A twisted icosahedral mesh is employed to accelerate the calculation.

  19. Photometric calibration of soft x-ray and p-terphenyl coated visible photodiodes in the 180--1500 eV range for fusion plasma spectroscopy

    International Nuclear Information System (INIS)

    The efficiencies of x-ray ultraviolet silicon, and p-terphenyl coated visible photodiodes have been measured in the 180--1500 eV range using a K radiation-Manson source. It is found that the quantum efficiency (electrons/photon) of the silicon diode varies between 25 and 400 in the above-mentioned range; the p-terphenyl coated diode is by two orders of magnitude less performing at the high-energy end of the range considered, but approaches the efficiency of the silicon diode at 100 A. Such diodes with built-in amplifiers, coated with scintillator and thin layers of metal films, can be efficiently used in spectroscopic diagnostics of magnetically confined plasmas

  20. Spectral index map of the Crab Nebula in the optical range

    International Nuclear Information System (INIS)

    Information about spatial distribution of the spectral index of the pulsar wind nebulae is important for understanding the structure of the nebulae and physical processes responsible for their formation. We present preliminary results on construction of a detailed index map of the Crab Nebula based on archival optical data obtained with the Hubble Space Telescope. Our map has much better spatial resolution than the previous one obtained by Veron-Cetty and Woltjer in 1993. It allows us to study in great details how the spectral slope of the synchrotron emission of the Crab varies along its torus and jet-like structures

  1. A Tape Method for Fast Characterization and Identification of Active Pharmaceutical Ingredients in the 2-18 THz Spectral Range

    Science.gov (United States)

    Kissi, Eric Ofosu; Bawuah, Prince; Silfsten, Pertti; Peiponen, Kai-Erik

    2015-03-01

    In order to find counterfeit drugs quickly and reliably, we have developed `tape method' a transmission spectroscopic terahertz (THz) measurement technique and compared it with a standard attenuated total reflection (ATR) THz spectroscopic measurement. We used well-known training samples, which include commercial paracetamol and aspirin tablets to check the validity of these two measurement techniques. In this study, the spectral features of some active pharmaceutical ingredients (APIs), such as aspirin and paracetamol are characterized for identification purpose. This work covers a wide THz spectral range namely, 2-18 THz. This proposed simple but novel technique, the tape method, was used for characterizing API and identifying their presence in their dosage forms. By comparing the spectra of the APIs to their dosage forms (powder samples), all distinct fingerprints present in the APIs are also present in their respective dosage forms. The positions of the spectral features obtained with the ATR techniques were akin to that obtained from the tape method. The ATR and the tape method therefore, complement each other. The presence of distinct fingerprints in this spectral range has highlighted the possibility of developing fast THz sensors for the screening of pharmaceuticals. It is worth noting that, the ATR method is applicable to flat faced tablets whereas the tape method is suitable for powders in general (e.g. curved surface tablets that require milling before measurement). Finally, we have demonstrated that ATR techniques can be used to screen counterfeit antimalarial tablets.

  2. High-accuracy detector calibration in the 3-1500 eV spectral range at the PTB radiometry laboratory.

    Science.gov (United States)

    Scholze, F; Henneken, H; Kuschnerus, P; Rabus, H; Richter, M; Ulm, G

    1998-05-01

    State-of-the-art detector calibration in the UV/VUV and soft X-ray spectral ranges at the Physikalisch-Technische Bundesanstalt (PTB) is based on the primary detector standard SYRES, a cryogenic electrical substitution radiometer capable of measuring radiant power of a few micro W. At the PTB radiometry laboratory at the synchrotron radiation facility BESSY, two dedicated beamlines are operated, providing monochromatic radiation of high spectral purity, high radiant power and tunable photon energy in the 3-1500 eV range. The spectral responsivity of detectors, e.g. photodiodes, can be measured with a relative uncertainty of about 1% by direct comparison with SYRES, as will be demonstrated for PtSi/Si and GaAsP/Au Schottky and silicon n-on-p photodiodes. The calibration of photon-counting detectors traceable to SYRES can by accomplished by exploiting the unique capability to scale the spectral photon flux over several orders of magnitude by changing the stored electron current. Calibrations of CCDs and photomultipliers are presented as examples. PMID:15263679

  3. High-accuracy detector calibration in the 3-1500 eV spectral range at the PTB radiometry laboratory

    International Nuclear Information System (INIS)

    State-of-the-art detector calibration in the UV/VUV and soft X-ray spectral ranges at the Physikalisch-Technische Bundesanstalt (PTB) is based on the primary detector standard SYRES, a cryogenic electrical substitution radiometer capable of measuring radiant power of a few ?W. At the PTB radiometry laboratory at the synchrotron radiation facility BESSY, two dedicated beamlines are operated, providing monochromatic radiation of high spectral purity, high radiant power and tunable photon energy in the 3-1500eV range. The spectral responsivity of detectors, e.g. photodiodes, can be measured with a relative uncertainty of about 1% by direct comparison with SYRES, as will be demonstrated for PtSi/Si and GaAsP/Au Schottky and silicon n-on-p photodiodes. The calibration of photon-counting detectors traceable to SYRES can by accomplished by exploiting the unique capability to scale the spectral photon flux over several orders of magnitude by changing the stored electron current. Calibrations of CCDs and photomultipliers are presented as examples

  4. THE SECOND STAGE OF FERMI at ELETTRA: A SEEDED FEL IN THE SOFT X-RAY SPECTRAL RANGE

    International Nuclear Information System (INIS)

    The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. The numerical simulations we present here show that the nominal (expected) electron-beam performance allows extension of the FEL spectral range down to 4 nm. A significant amount of third harmonic power can be also expected. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, e.g., high harmonic generation in gases.

  5. Constitutive spectral EEG peaks in the gamma range: suppressed by sleep, reduced by mental activity and resistant to sensory stimulation

    OpenAIRE

    Grummett, Tyler S.; Fitzgibbon, Sean P.; Lewis, Trent W.; DeLosAngeles, Dylan; Whitham, Emma M.; Pope, Kenneth J.; Willoughby, John O.

    2014-01-01

    Objective: In a systematic study of gamma activity in neuro-psychiatric disease, we unexpectedly observed distinctive, apparently persistent, electroencephalogram (EEG) spectral peaks in the gamma range (25–100 Hz). Our objective, therefore, was to examine the incidence, distribution and some of the characteristics of these peaks. Methods: High sample-rate, 128-channel, EEG was recorded in 603 volunteers (510 with neuropsychiatric disorders, 93 controls), whilst performing cognitive tasks,...

  6. Calculation of spectral shifts in UV–visible region and photoresponsive behaviour of fluorinated liquid crystals: Effect of solvent and substituent

    International Nuclear Information System (INIS)

    The photoresponsive behaviour of fluorinated liquid crystals p-phenylene-4-methoxy benzoate-4-trifluoromethylbenzoate (FLUORO1), and 4-propyloxyphenyl-4-(4-trifluoromethylbenzoyloxy) benzoate (FLUORO2) has been systematically investigated using the CNDO/S + CI and INDO/S + CI methods. These methods have been employed to calculate/analyze the spectral shifts, and absorbance measurements in UV–visible region of the systems. The electronic transitions, absorption wavelength, HOMO (highest occupied molecular orbital), and LUMO (lowest unoccupied molecular orbital) energies have been calculated. Further, ultraviolet (UV) stability of the molecules has been discussed in the light of absorption wavelength and electronic transition oscillator strength (f). The effect of different solvent media and substituents on transition energies, oscillator strength, and other absorption parameters have also been reported. The present article provides valuable information regarding enhancing the UV stability of molecules by marinating their conductivity. Highlights: ? The strongest bands of FLUORO molecules can be assigned as ? ? ?? transitions. ? A small red-shift indicates a weak exciton coupling of chromophores. ? No n ? ?? transition occurs due to the rigidity of the ring system of the molecules. ? The HOMO, LUMO, and Eg values have been found to be independent of solvent effect.

  7. Spectral Analysis in EUV Range for Study of Core Impurity Behavior in HL-2A

    International Nuclear Information System (INIS)

    Extreme ultraviolet (EUV) spectroscopy has been developed for impurity diagnostics in HL-2A tokamak. The EUV spectrometer consists of an entrance slit, a holographic varied-line-space (VLS) grating, a back-illuminated charge-coupled device (CCD) and a laser light source for optical alignment. Spectral lines in wavelength region of 20-500 Å observed from HL-2A plasmas were analyzed to study the impurity behavior. Spectral and temporal resolutions used for the analysis were 0.19 Å at CV (2×33.73 Å) and 6 ms, respectively. It was found that carbon, oxygen and iron impurities were usually dominant in the HL-2A plasma. They almost disappeared when the siliconization was carried out. Although the EUV spectra were entirely replaced by the silicon emissions just after the siliconization, the emissions were considerably decreased with accumulation of discharges. Aluminum and neon were externally introduced into the HL-2A plasma based on laser blow-off (LBO) and supersonic molecular beam injection (SMBI) techniques for a trial of the impurity transport study, respectively. The preliminary result is presented for time behavior of EUV spectral lines. (magnetically confined plasma)

  8. High dynamic range measurement of spectral responsivity and linearity of a radiation thermometer using a super-continuum laser and LEDs

    International Nuclear Information System (INIS)

    To realize the temperature scale above the freezing point of silver according to the definition of ITS-90, the dynamic range of the spectral responsivity is one of the most important factors which limit its uncertainty. When the residual spectral response at both side bands of a spectral band is not negligible, a significant uncertainty can be caused by a low dynamic range of the spectral responsivity measurement. In general, incandescent lamps are used to measure the spectral responsivity and the linearity. The dynamic range of the spectral responsivity measurement is often limited by a trade-off with the desired spectral resolution, which is less than 6 decades. Nonlinearity is another limiting fact of uncertainties of the temperature scale. Tungsten lamps have disadvantage in the nonlinearity measurements in terms of adjustability of radiance level and spectral selectivity. We report spectral responsivity measurements of which the measurable dynamic range is enhanced 50 times after replacing a QTH lamp with a super continuum laser. We also present a spectrally selected linearity measurement over a wide dynamic range using high-brightness light emitting diode arrays to observe a slight saturation of linearity

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

    International Nuclear Information System (INIS)

    We have studied superluminescent diodes (SLDs) and semiconductor optical amplifiers (SOAs) based on an (AlxGa1-x)As/GaAs single quantum well structure with an Al content x ? 0.1 in a 10-nm-thick active layer. Depending on the length of the active channel, the single-mode fibre coupled cw output power of the SLDs is 1 to 30 mW at a spectral width of about 50 nm. The width of the optical gain band in the active channel exceeds 40 nm. Preliminary operating life tests have demonstrated that the devices are sufficiently reliable. (lasers)

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

    OpenAIRE

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

    2011-01-01

    A full-bandwidth k-domain linearization method for spectral-domain optical coherence tomography (SD-OCT) is demonstrated. The method uses information of the wavenumber–pixel-position provided by a translating-slit-based wavelength filter. For calibration purposes, the filter is placed either after a broadband source or at the end of the sample path, and the filtered spectrum with a narrowed line width (~0.5 nm) is incident on a line-scan camera in the detection path. The wavelength-swept sp...

  11. TESIS experiment on study of solar corona in EUV spectral range (CORONAS-PHOTON project)

    International Nuclear Information System (INIS)

    A new orbital station, namely: the CORONAS-PHOTON one (to be launched in 2006) equipped with systems to explore Sun at the intensification period of the solar activity 24-th cycle and at its peak is being designed within the framework of the CORONAS National Sun Space Exploration Program. The station equipment consists of systems to observe Sun within the spectral soft X-ray and vacuum ultraviolet bands. Paper lists and describes the TESIS experiment tools designed for the CORONAS-PHOTON Project to ensure the Sun atmospheric research within short-wave band

  12. Tailoring optical properties of WO3 films in the visible to infrared range by ion bombardment and its description by an oscillator model

    International Nuclear Information System (INIS)

    Evaporated and sputtered tungstentrioxide (WO3) films were bombarded with 300-keV He+ and Ar+ ions, respectively, and the resulting changes of the real [n(?)] and imaginary [k(?)] parts of the refractive index in the visible to infrared range of the wavelength ? were determined in situ. The primary effect of an ion-induced blue coloration is directly reflected by an absorption band centered at 1100 nm, which is growing for increasing ion fluences and exponentially approaching saturation. This monotonous increase of absorption is accompanied by changes of n(?) with a characteristic fixed point n(?*) independent of the ion bombardment, while for ?>?* an ion-induced increase and for ?3 matrix and ion-induced Lorentz oscillators. While the density of these oscillators as well as their damping coefficients exhibit an exponential saturation behavior for increasing ion fluences, their eigenfrequencies as well as the matrix contribution are practically independent of the bombardment

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

    Directory of Open Access Journals (Sweden)

    J. Jung

    2010-06-01

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

  14. Infrared normal spectral emissivity of Ti-6Al-4V alloy in the 500-1150 K temperature range

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Fernandez, L. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Industria de Turbo Propulsores, S.A., Planta de Zamudio, Edificio 300, 48170 Zamudio, Bizkaia (Spain); Risueno, E. [CIC Energigune, Parque Tecnologico, Albert Einstein 48, 01510 Minano, Alava, Spain. (Spain); Perez-Saez, R.B., E-mail: raul.perez@ehu.es [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Instituto de Sintesis y Estudio de Materiales, Universidad del Pais Vasco, Apdo. 644,48080 Bilbao, Spain. (Spain); Tello, M.J. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Instituto de Sintesis y Estudio de Materiales, Universidad del Pais Vasco, Apdo. 644,48080 Bilbao, Spain. (Spain)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer First heating cycle acts as a annealing, relieving the surface stresses. Black-Right-Pointing-Pointer Stress relieving occurs mainly above 900 K. Black-Right-Pointing-Pointer Emissivity decreases between 0.35 and 0.10 in the 2.5-22 {mu}m spectral range. Black-Right-Pointing-Pointer Emissivity increases linearly with temperature, with the same slope for {lambda} > 10 {mu}m. Black-Right-Pointing-Pointer Good agreement between resistivity and emissivity by means of Hagen-Rubens relation. - Abstract: Thermal radiative emissivity is related to the optical and electrical properties of materials, and it is a key parameter required in a large number of industrial applications. In the case of Ti-6Al-4V, spectral emissivity experimental data are not available for the range of temperatures between 400 and 1200 K, where almost all industrial applications take place. The experimental results in this paper show that the normal spectral emissivity decreases with wavelength from a value of about 0.35 at 2.5 {mu}m to about 0.10 at 22 {mu}m. At the same time, the spectral emissivity shows a slight linear increase with temperature between 500 and 1150 K, with approximately the same slope for all wavelengths. Additionally, the influence of the samples thermal history on the emissivity is studied. A strong decrease in the emissivity values appears due to the effect of surface stress relaxation processes. This means that the radiative properties of this alloy strongly depend on the surface stress state. A thermal treatment to relieve the surface stress should be carried out to achieve a steady state of the radiative properties. In addition, a good qualitative agreement is found between the temperature dependence of the electrical resistivity obtained using conventional measurements and the one obtained from the emissivity experimental results by using the Hagen-Rubens equation.

  15. Infrared normal spectral emissivity of Ti–6Al–4V alloy in the 500–1150 K temperature range

    International Nuclear Information System (INIS)

    Highlights: ? First heating cycle acts as a annealing, relieving the surface stresses. ? Stress relieving occurs mainly above 900 K. ? Emissivity decreases between 0.35 and 0.10 in the 2.5–22 ?m spectral range. ? Emissivity increases linearly with temperature, with the same slope for ? > 10 ?m. ? Good agreement between resistivity and emissivity by means of Hagen–Rubens relation. - Abstract: Thermal radiative emissivity is related to the optical and electrical properties of materials, and it is a key parameter required in a large number of industrial applications. In the case of Ti–6Al–4V, spectral emissivity experimental data are not available for the range of temperatures between 400 and 1200 K, where almost all industrial applications take place. The experimental results in this paper show that the normal spectral emissivity decreases with wavelength from a value of about 0.35 at 2.5 ?m to about 0.10 at 22 ?m. At the same time, the spectral emissivity shows a slight linear increase with temperature between 500 and 1150 K, with approximately the same slope for all wavelengths. Additionally, the influence of the samples thermal history on the emissivity is studied. A strong decrease in the emissivity values appears due to the effect of surface stress relaxation processes. This means that the radiative properties of this alloy strongly depend on the surface stress state. A thermal treatment to relieve the surface stress should be carried out to be carried out to achieve a steady state of the radiative properties. In addition, a good qualitative agreement is found between the temperature dependence of the electrical resistivity obtained using conventional measurements and the one obtained from the emissivity experimental results by using the Hagen–Rubens equation.

  16. Band-pass filters for THz spectral range fabricated by laser ablation

    Science.gov (United States)

    Voisiat, B.; Bi?i?nas, A.; Kašalynas, I.; Ra?iukaitis, G.

    2011-09-01

    The terahertz resonant metal-mesh filters were fabricated using the laser direct writing technique. UV picosecond laser was employed to cut matrixes of cross-shaped holes in stainless steel foil and molybdenum layer deposited on polyimide substrate. Different laser processing strategies were developed: holes were cut through in the metal foil and the molybdenum film was removed from the polyimide by laser ablation. Band-pass filters with a different center frequency were designed and fabricated. The regular shape, smoothness of edges and sharpness of corners of the cross-shaped holes in the metal were the main attributes for quality assessment for the laser ablation process. Spectral characteristics of the filters, determined by the mesh period, cross-arm length, and its width, were investigated by terahertz time-domain spectroscopy and conventional space-domain Fourier transform spectroscopy. Experimental data were supported by three-dimensional finite-difference time-domain simulations.

  17. Effect of the volcanic ash type uncertainties on ash and SO2 retrievals from satellite multi-spectral measurements in the TIR spectral range

    Science.gov (United States)

    Corradini, Stefano; Merucci, Luca; Campion, Robin; Carboni, Elisa

    2013-04-01

    After the Eyjafjallajokull 2010 eruption the quantitative determination of the volcanic ash present in ash clouds has become more important because of the policy change from the previous zero tolerance to the new ash threshold based approach in the aviation hazard management. Volcanic SO2 has an impact on the environment and when injected at high altitudes can be oxidized to form sulphates capable of reflecting solar radiation then causing surface cooling. Observations of the volcanic degassing also yield insights into the magmatic processes which control volcanic activity during both quiescent and eruptive phases. During volcanic eruptions ash and gases are often emitted simultaneously. The plume ash particles reduce the top of atmosphere radiance in the entire thermal infrared (TIR) spectral range causing a significant SO2 columnar abundance overestimation. The ash optical properties are among the most critical parameters to set, their uncertainties cause meaningful errors on both ash and SO2 retrievals. In this work the effect effect of the volcanic ash type uncertainties on ash and SO2 retrievals from MODIS measurements in the TIR spectral range have been quantified. As test case some events of the 2010 Eyjafjallajokull (Iceland) eruption has been considered. The ash optical properties derive from the ARIA database of the Oxford University, while the MODIS SO2 and ash retrievals strategies are based on the BTD and minimization approaches using the channels centered at 8.7, 11 and 12 micron. The radiative transfer model simulations, needed for the retrievals schemes, are carried out by using MODTRAN [Corradini et al., 2009]. The MODIS SO2 retrievals have been also compared with the retrievals obtained by using IASI hyper-spectral and ASTER high spatial resolution data. The two procedures are considered less sensitive to the ash type: the ASTER retrieval scheme [Campion et al. 2010] consists of adjusting the SO2 column amount until the ratios of radiance simulated on several ASTER bands match the observations, while the IASI retrieval [Carboni et al. 2012] is an optimal estimation scheme that exploit the high resolution spectrometer measurements of the two SO2 absorption bands around 7.3 and 8.7 micron.

  18. Influence of temperature on Pr:YAlO3 laser operation in the orange and near-infrared spectral range

    Science.gov (United States)

    Fibrich, M.; Šulc, J.; Jelínková, H.

    2014-10-01

    Continuous wave Pr:YAlO3 laser behavior in the orange (622 nm) and near-infrared (747 nm) spectral range down to cryogenic temperature is reported. To minimize resonator losses, dielectric films were deposited on the crystal facets to form a microchip geometry. More than 300 mW of output power at 747 nm wavelength with a slope efficiency close to the quantum limit is demonstrated. Furthermore, the first diode-pumped Pr:YAlO3 orange laser is described, as we believe.

  19. Influence of temperature on Pr:YAlO3 laser operation in the orange and near-infrared spectral range

    International Nuclear Information System (INIS)

    Continuous wave Pr:YAlO3 laser behavior in the orange (622 nm) and near-infrared (747 nm) spectral range down to cryogenic temperature is reported. To minimize resonator losses, dielectric films were deposited on the crystal facets to form a microchip geometry. More than 300 mW of output power at 747 nm wavelength with a slope efficiency close to the quantum limit is demonstrated. Furthermore, the first diode-pumped Pr:YAlO3 orange laser is described, as we believe. (letter)

  20. A new undulator for the extension of the spectral range of the CLIO FEL

    Energy Technology Data Exchange (ETDEWEB)

    Marcouille, O.; Berset, J.M.; Glotin, F. [LURE, Orsay (France)] [and others

    1995-12-31

    We built a new undulator in order to extend the lasing range of the CLIO infrared FEL. Presently, CLIO operates in the wavelength range 2 - 17 {mu}m. Beyond 14 {mu}m, the power decreases rapidly, because of the diffraction losses of the vacuum chamber (7 mm height and 2 m long). Thus, lasing at higher wavelengths implies installing a chamber with a height approximately twice. Then the minimum gap is increased and the maximum deflection parameter, K, is reduced from 2 to 1 : the laser tunability is greatly reduced. This is why a new undulator has been built.

  1. New Measurements of the Absolute Spectral Energy Distribution of Solar Radiation in the Range Double Lambda 650-1070 NM

    Science.gov (United States)

    Burlov-Vasilev, K. A.; Vasileva, I. E.; Matveev, Yu. B.

    1996-01-01

    Spectral measurements of the solar disk centre intensity for the near-IR region have been made at he Terskol High-Altitude Station in 1992. These measurements are the continuation of the program for the solar absolute spectral energy distribution investigation. Data published earlier are extended to the longwave spectral region up to 1070 nm. The special-purpose solar telescope SEF-1 was used. We compared the disk centre brightness with brightness of the calibrated region of the standard ribbon tungsten lamp. The atmospheric extinction was taken into account by the Bouguer method with simultaneous control of the atmosphere stability. The 1-nm integrals of the disk centre intensity in the range double lamda 650-1070 nm based on 5-day measurements in March-October 1992 are given. The uncertainty of these values is 2%. In regions with strong telluric absorption by oxygen and water-vapour bands, the reductions are made, using synthetic atmospheric absorption spectra computed on the basis of molecular parameter atlas HITRAN and the standard model atmosphere. By the use of the solar limb darkening coefficients the values of the solar flux at 1 A.U. were derived. Our measurements show the best agreement with the data of Makarova, Kharitonov, and Kazachevskaya as well as with the common data from Shaw and Frohlich. For lambda greater than 850 nm our data are systematically lower than the data by Neckel and Labs.

  2. Electron storage ring BESSY as a radiometric source of calculable spectral radiant power between 0.5 and 1000 nm

    International Nuclear Information System (INIS)

    The spectral radiant power of the electron storage ring BESSY was measured absolutely in the infrared and visible, and its angular distribution in the infrared, visible, and soft-x-ray ranges. The results prove BESSY to be a standard of calculable spectral radiant power, at least for wavelengths from 0.5 to 1000 nm

  3. Spectral Content of the NLC Bunch Train due to Long Range Wakefields(LCC-0015)

    International Nuclear Information System (INIS)

    The functional specifications of the sub-train position feedback for the NLC Main Linac are determined by the expected amplitude and spectrum of distortions to the bunch train, which in turn arise from the long-range wakefields of the RF structures. We describe a method for estimating the amplitude and spectrum of the distortions due to assorted structure misalignments, and apply the method to both tilted structures and structures with a cell-to-cell misalignment determined by a random-walk model. Some implications for the sub-train feedback, such as the required system bandwidth, are considered

  4. The relationship between professional operatic soprano voice and high range spectral energy

    Science.gov (United States)

    Barnes, Jennifer J.; Davis, Pamela; Oates, Jennifer; Chapman, Janice

    2004-07-01

    Operatic sopranos need to be audible over an orchestra yet they are not considered to possess a singer's formant. As in other voice types, some singers are more successful than others at being heard and so this work investigated the frequency range of the singer's formant between 2000 and 4000 Hz to consider the question of extra energy in this range. Such energy would give an advantage over an orchestra, so the aims were to ascertain what levels of excess energy there might be and look at any relationship between extra energy levels and performance level. The voices of six operatic sopranos (national and international standard) were recorded performing vowel and song tasks and subsequently analyzed acoustically. Measures taken from vowel data were compared with song task data to assess the consistency of the approaches. Comparisons were also made with regard to two conditions of intended projection (maximal and comfortable), two song tasks (anthem and aria), two recording environments (studio and anechoic room), and between subjects. Ranking the singers from highest energy result to lowest showed the consistency of the results from both vowel and song methods and correlated reasonably well with the performance level of the subjects. The use of formant tuning is considered and examined.

  5. Image Simulation for Mingantu Ultrawide Spectral Radioheliograph in the Decimetre Wave Range

    Science.gov (United States)

    Du, Jing; Yan, Yihua; Wang, Wei; Liu, Donghao

    2015-06-01

    The MUSER is a solar-dedicated radio interferometric array, which will observe the Sun over a wide range of radio frequencies (0.4-15 GHz), and make high time, space and frequency resolution images of the Sun simultaneously. MUSER is located in Mingantu Station in Inner Mongolia of China, which is about 400 kilometres away from Beijing. MUSER consists of two arrays: MUSER-I and MUSER-II. MUSER-I contains 40 antennas with 4.5-m aperture operating at 400 MHz to 2 GHz. MUSER-II contains 60 antennas with 2-m aperture operating at 2 to 15 GHz. Currently, MUSER has already been established and entered into the stage of test observation. This work is focus on the imaging performance of MUSER-I. This paper introduces MUSER-I briefly, presents the analysis of the array configurations, and evaluates the image quality mainly using the dynamic range, fidelity index, and the peak signal-to-noise ratio, also make some actual solar model simulations with CASA, the results will be shown below.

  6. Shortwave Spectral Radiative Forcing of Cumulus Clouds from Surface Observations

    Energy Technology Data Exchange (ETDEWEB)

    Kassianov, Evgueni I.; Barnard, James C.; Berg, Larry K.; Long, Charles N.; Flynn, Connor J.

    2011-04-02

    The spectral changes of the total cloud radiative forcing (CRF) and its diffuse and direct components are examined by using spectrally resolved (visible spectral range) all-sky surface irradiances measured by Multi-Filter Rotating Shadowband Radiometer. We demonstrate: (i) the substantial contribution of the diffuse component to the total CRF, (ii) the well-defined spectral variations of total CRF in the visible spectral region, and (iii) the strong statistical relationship between spectral (500 nm) and shortwave broadband values of total CRF. Our results suggest that the framework based on the visible narrowband fluxes can provide important radiative quantities for rigorous evaluation of radiative transfer parameterizations and can be applied for estimation of the shortwave total CRF.

  7. Dielectric function in the NIR-VUV spectral range of (InxGa1?x)2O3 thin films

    International Nuclear Information System (INIS)

    We determined the dielectric function of the alloy system (InxGa1?x)2O3 by spectroscopic ellipsometry in the wide spectral range from 0.5?eV to 8.5?eV and for In contents ranging from x?=?0.02 to x?=?0.61. The predicted optical transitions for binary, monoclinic ?-Ga2O3, and cubic bcc-In2O3 are well reflected by the change of the dielectric functions' lineshape as a function of the In content. In an intermediate composition range with phase-separated material (x???0.3…0.4), the lineshape differs considerably, which we assign to the presence of the high-pressure rhombohedral InGaO3-II phase, which we also observe in Raman experiments in this range. By model analysis of the dielectric function, we derived spectra of the refractive index and the absorption coefficient and energy parameters of electronic band-band transitions. We discuss the sub-band gap absorption tail in relation to the influence of the In 4d orbitals on the valence bands. The data presented here provide a basis for a deeper understanding of the electronic properties of this technologically important material system and may be useful for device engineering

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

    Science.gov (United States)

    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.

  9. Novel SO2 spectral evaluation scheme using the 360–390 nm wavelength range

    Directory of Open Access Journals (Sweden)

    T. Wagner

    2010-03-01

    Full Text Available Differential Optical Absorption Spectroscopy (DOAS is a well established spectroscopic method to determine trace gases in the atmosphere. During the last decade, passive DOAS, which uses solar radiation scattered in the atmosphere as a light source, has become a standard tool to determine SO2 column densities and emission fluxes from volcanoes and other large sources by ground based as well as satellite measurements. For the determination of SO2 column densities, the structured absorption of the molecule in the 300–330 nm region (due to the A1B1?X1A1 transition is used. However, there are several problems limiting the accuracy of the technique in this particular application. Here we propose to use an alternative wavelength region (360–390 nm due to the spin-forbidden a3B2?X1A1 transition for the DOAS evaluation of SO2 in conditions where high SO2 column densities prevail. We show this range to have considerable advantages in such cases, in particular when the particle content of the plume is high and when measurements are performed at large distances from the area of interest.

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

    International Nuclear Information System (INIS)

    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.

  11. Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS in the red spectral range

    Directory of Open Access Journals (Sweden)

    T. Wagner

    2007-01-01

    Full Text Available A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm reflectance structures (i.e. "fingerprint" structures of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS, which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric absorptions are automatically corrected (in contrast to other algorithms. The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the results illustrate the seasonal cycles of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

  12. New methods of highly efficient controlled generation of radiation by liquid crystal nanostructures in a wide spectral range

    International Nuclear Information System (INIS)

    We report the recent results of research focused on a new kind of soft matter-the liquid-crystal nanocomposites with controllable mechanical and nonlinear optical properties. These are promising media for implementation of ultra-compact photonic devices and efficient sources of coherent radiation in a wide spectral range. We overview the technology of preparation of nematic-liquid-crystal media saturated with disclination defects. The defects were formed in different ways: by embedding nanoparticles and molecular objects, by exposure to alpha-particle flux. The defect locations were controlled by applying an electric field. We also present and discuss the recently discovered features of nematic-liquid-crystal media: a thermal orientation effect leading to the fifth-order optical nonlinearity, enormous second-order susceptibility revealed by measurements, and structural changes upon exposure to laser radiation. We report on efficient generation of harmonics, sum and difference optical frequencies in nematic-liquid-crystal media. In addition, transformation of laser radiation spectra to spectral supercontinua, and filamentation of laser beams were also observed in nematic-liquid-crystal media. We conclude that most nonlinear optical effects result from changes of the orientational order in the examined nematic liquid crystals. These changes lead to the symmetry breaking and disclination appearances.

  13. Identification of coronal sources of the solar wind from solar images in the EUV spectral range

    Science.gov (United States)

    Slemzin, V. A.; Shugai, Yu. S.

    2015-01-01

    Methods of localizing coronal sources of the solar wind (SW), such as coronal holes, quasi-stationary fluxes from active regions, and transient sources associated with small-scale active phenomena are considered based on vacuum-ultraviolet (EUV) images of the corona at low solar activity during the initial period of the 24th solar cycle (2010). It is shown that a SW velocity profile can be calculated from the relative areas of coronal holes (CH) at the central part of the disk based on the images in the ranges of 193 and 171 Å. The images in the 193 Å describe the geometry of large HCs that represent sources of fast SW well. The images in 171 Å are a better visualization of small CHs, based on which the profile of a slow SW component was calculated to a high accuracy (up to 65 km/s). According to Hinode/EIS data of October 15, 2010, using the Doppler spectroscopy method at the streamer base over the active region 11112, the source of the outgoing plasma flux with the mean velocity of 17 km/s was localized in the magnetic field region with an intensity of less than 200 Gauss. According to the estimate, the density of the plasma flux from this source is an order of magnitude greater than the value required for explaining the distinction between the calculated and measured profiles of a slow SW velocity. For finding the transient SW component based on small-scale flare activity, SW parameters were analyzed for the periods of flares accompanied by coronal mass ejections (CMEs), and for the periods without flares, according to the data obtained in 2010 from the ACE and GOES satellites and by coronagraphs on the STEREO-A and - B spacecraft. The ion ratios C+6/C+5 and O+7/O+6 and the mean charge of Fe ions for periods with flares were shown to be shifted toward large values, suggesting the presence of a hot SW component associated with flare activity. A noticeable correlation between the maximum charge of Fe ions and the peak power of a flare, previously observed for flares of a higher class, was confirmed. The mean value of the SW flux density during the periods of flares was 30% higher than that in the periods without flares, which is possibly associated also with the growth of fluxes from other sources with an increasing solar activity level. Based on the example of a series of flares of October 13-14, 2010, it was supposed that transient SW fluxes from the weak flares at low solar activity can manifest themselves in the form of interplanetary ICME-transients.

  14. Simultaneous dual free spectral range microwave photonic filter using a high-birefringence chirped grating in a Sagnac loop.

    Science.gov (United States)

    Ning, Guoxiang; Shum, Ping; Aditya, Sheel; Gong, Yandong

    2007-01-01

    We propose a continuously tunable, dual free spectral range (FSR) photonic microwave notch filter configuration using a high-birefringence linearly chirped fiber Bragg grating (Hi-Bi LCFBG) that is connected in a Sagnac loop using a Hi-Bi coupler. The configuration employs double sideband modulation and can generate two FSRs simultaneously. The larger FSR corresponds to the differential time delay of the Hi-Bi LCFBG and the Hi-Bi pigtails of the coupler; the smaller FSR corresponds to the time delay between the arms of the Sagnac loop. Measured results demonstrate dual FSR, a large notch rejection, and that the FSR is easily tunable by tuning the LCFBG. We also present the filter transfer function for the design. Experimental results agree well with the theoretical analysis. PMID:17164857

  15. Quantum efficiency of cesium iodide photocathodes in the 120-220 nm spectral range traceable to a primary detector standard

    International Nuclear Information System (INIS)

    Differently prepared CsI samples have been investigated in the 120-220 nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because this type of photodiode - unlike silicon p-on-n photodiodes - proved to be of sufficiently stable response when exposed to vacuum ultraviolet radiation. The paper reviews the experimental procedures that were employed to characterize and calibrate the GaAsP photodiode and reports the results that were obtained on the investigated CsI photocathodes

  16. Quantum efficiency of cesium iodide photocathodes in the 120-220 nm spectral range traceable to a primary detector standard

    Science.gov (United States)

    Rabus, H.; Kroth, U.; Richter, M.; Ulm, G.; Friese, J.; Gernhäuser, R.; Kastenmüller, A.; Maier-Komor, P.; Zeitelhack, K.

    1999-12-01

    Differently prepared CsI samples have been investigated in the 120-220 nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because this type of photodiode - unlike silicon p-on-n photodiodes - proved to be of sufficiently stable response when exposed to vacuum ultraviolet radiation. The paper reviews the experimental procedures that were employed to characterize and calibrate the GaAsP photodiode and reports the results that were obtained on the investigated CsI photocathodes.

  17. Quantum efficiency of cesium iodide photocathodes in the 120-220 nm spectral range traceable to a primary detector standard

    CERN Document Server

    Rabus, H; Richter, M; Ulm, G; Friese, J; Gernhäuser, R; Kastenmüller, A; Maier-Komor, P; Zeitelhack, K

    1999-01-01

    Differently prepared CsI samples have been investigated in the 120-220 nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because this type of photodiode - unlike silicon p-on-n photodiodes - proved to be of sufficiently stable response when exposed to vacuum ultraviolet radiation. The paper reviews the experimental procedures that were employed to characterize and calibrate the GaAsP photodiode and reports the results that were obtained on the investigated CsI photocathodes.

  18. Spectral counting assessment of protein dynamic range in cerebrospinal fluid following depletion with plasma-designed immunoaffinity columns

    Directory of Open Access Journals (Sweden)

    Borg Jacques

    2011-06-01

    Full Text Available Abstract Background In cerebrospinal fluid (CSF, which is a rich source of biomarkers for neurological diseases, identification of biomarkers requires methods that allow reproducible detection of low abundance proteins. It is therefore crucial to decrease dynamic range and improve assessment of protein abundance. Results We applied LC-MS/MS to compare the performance of two CSF enrichment techniques that immunodeplete either albumin alone (IgYHSA or 14 high-abundance proteins (IgY14. In order to estimate dynamic range of proteins identified, we measured protein abundance with APEX spectral counting method. Both immunodepletion methods improved the number of low-abundance proteins detected (3-fold for IgYHSA, 4-fold for IgY14. The 10 most abundant proteins following immunodepletion accounted for 41% (IgY14 and 46% (IgYHSA of CSF protein content, whereas they accounted for 64% in non-depleted samples, thus demonstrating significant enrichment of low-abundance proteins. Defined proteomics experiment metrics showed overall good reproducibility of the two immunodepletion methods and MS analysis. Moreover, offline peptide fractionation in IgYHSA sample allowed a 4-fold increase of proteins identified (520 vs. 131 without fractionation, without hindering reproducibility. Conclusions The novelty of this study was to show the advantages and drawbacks of these methods side-to-side. Taking into account the improved detection and potential loss of non-target proteins following extensive immunodepletion, it is concluded that both depletion methods combined with spectral counting may be of interest before further fractionation, when searching for CSF biomarkers. According to the reliable identification and quantitation obtained with APEX algorithm, it may be considered as a cheap and quick alternative to study sample proteomic content.

  19. Spectral counting assessment of protein dynamic range in cerebrospinal fluid following depletion with plasma-designed immunoaffinity columns

    Science.gov (United States)

    2011-01-01

    Background In cerebrospinal fluid (CSF), which is a rich source of biomarkers for neurological diseases, identification of biomarkers requires methods that allow reproducible detection of low abundance proteins. It is therefore crucial to decrease dynamic range and improve assessment of protein abundance. Results We applied LC-MS/MS to compare the performance of two CSF enrichment techniques that immunodeplete either albumin alone (IgYHSA) or 14 high-abundance proteins (IgY14). In order to estimate dynamic range of proteins identified, we measured protein abundance with APEX spectral counting method. Both immunodepletion methods improved the number of low-abundance proteins detected (3-fold for IgYHSA, 4-fold for IgY14). The 10 most abundant proteins following immunodepletion accounted for 41% (IgY14) and 46% (IgYHSA) of CSF protein content, whereas they accounted for 64% in non-depleted samples, thus demonstrating significant enrichment of low-abundance proteins. Defined proteomics experiment metrics showed overall good reproducibility of the two immunodepletion methods and MS analysis. Moreover, offline peptide fractionation in IgYHSA sample allowed a 4-fold increase of proteins identified (520 vs. 131 without fractionation), without hindering reproducibility. Conclusions The novelty of this study was to show the advantages and drawbacks of these methods side-to-side. Taking into account the improved detection and potential loss of non-target proteins following extensive immunodepletion, it is concluded that both depletion methods combined with spectral counting may be of interest before further fractionation, when searching for CSF biomarkers. According to the reliable identification and quantitation obtained with APEX algorithm, it may be considered as a cheap and quick alternative to study sample proteomic content. PMID:21906361

  20. Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 8

    Directory of Open Access Journals (Sweden)

    S. A. Buehler

    2012-07-01

    Full Text Available Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized "essential climate variable" ice water path (IWP and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8, which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  1. Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 8

    Directory of Open Access Journals (Sweden)

    S. A. Buehler

    2012-02-01

    Full Text Available Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized "essential climate variable" ice water path (IWP and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8, which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  2. Uncertainty analysis of sensor performance parameters in the shortwave infrared spectral range based on nightglow as the main lightsource

    Science.gov (United States)

    Svensson, Thomas; Bergström, David

    2014-05-01

    Images collected in the shortwave infrared (SWIR) spectral range, 1-2.5 ?m, are similar to visual (VIS) images and are easier to interpret for a human operator than images collected in the thermal infrared range, >3 ?m. The ability of SWIR radiation to penetrate ordinary glass also means that conventional lens materials can be used. The night vision capability of a SWIR camera is however dependent on external light sources. At moonless conditions the dominant natural light source is nightglow, but the intensity is varying, both locally and temporally. These fluctuations are added to variations in other parameters and therefore the real performance of a SWIR camera at moonless conditions can be quite different compared with the expected performance. Collected measured data from the literature on the temporal and local variations of nightglow are presented and the variations of the nightglow intensity and other measured parameters are quantified by computing standard and combined standard uncertainties. The analysis shows that the uncertainty contributions from the nightglow variations are significant. However, nightglow is also found to be a potentially adequate light source for SWIR applications.

  3. X-ray grating spectrometer for opacity measurements in the 50 eV to 250 eV spectral range at the LULI 2000 laser facility

    Energy Technology Data Exchange (ETDEWEB)

    Reverdin, Charles; Caillaud, T.; Gilleron, F.; Pain, J. C.; Silvert, V.; Soullie, G.; Villette, B. [CEA, DAM, DIF, 91297 Arpajon (France); Thais, Frederic; Loisel, Guillaume; Blenski, T.; Poirier, M. [CEA, DSM, IRAMIS, Service Photons, Atomes et Molecules, 91191 Gif-sur-Yvette (France); Busquet, M. [ARTEP Inc, Ellicott City, Maryland 21042 (United States); Bastiani-Ceccotti, S.; Serres, F. [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, route de Saclay, 91128 Palaiseau (France); Ducret, J. E. [CELIA, UMR5107, CEA, CNRS, Universite de Bordeaux, 33400 Talence (France); Foelsner, W. [Max Planck Instituet fuer Quantum Optik, 85748 Garching (Germany); Gilles, D.; Turck-Chieze, S. [CEA, DSM, IRFU, Service d' astrophysique, 91191 Gif-sur-Yvette (France)

    2012-10-15

    An x-ray grating spectrometer was built in order to measure opacities in the 50 eV to 250 eV spectral range with an average spectral resolution {approx} 50. It has been used at the LULI-2000 laser facility at Ecole Polytechnique (France) to measure the {Delta}n = 0, n = 3 transitions of several elements with neighboring atomic number: Cr, Fe, Ni, and Cu in the same experimental conditions. Hence a spectrometer with a wide spectral range is required. This spectrometer features one line of sight looking through a heated sample at backlighter emission. It is outfitted with one toroidal condensing mirror and several flat mirrors cutting off higher energy photons. The spectral dispersion is obtained with a flatfield grating. Detection consists of a streak camera sensitive to soft x-ray radiation. Some experimental results showing the performance of this spectrometer are presented.

  4. VERUCLAY – a new type of photo-adsorbent active in the visible light range: modification of montmorillonite surface with organic surfactant

    Science.gov (United States)

    Montmorillonite K10 was treated with VeruSOL-3, a biodegradable and food-grade surfactant mixture of coconut oil, castor oil and citrus extracts, to manufacture a benign catalytic adsorbent that is active in the visible light. Veruclay was characterized by SEM, XRD, TGA, UVDRS, a...

  5. Composite films prepared by plasma ion-assisted deposition (IAD) for design and fabrication of antireflection coatings in visible and near-infrared spectral regions

    Science.gov (United States)

    Tsai, Rung-Ywan; Ho, Fang C.

    1994-11-01

    Ion-assisted deposition (IAD) processes configured with a well-controlled plasma source at the center base of a vacuum chamber, which accommodates two independent e-gun sources, is used to deposition TiO2MgF2 and TiO2-SiO2 composite films of selected component ratios. Films prepared by this technology are found durable, uniform, and nonabsorbing in visible and near-IR regions. Single- and multilayer antireflection coatings with refractive index from 1.38 to 2.36 at (lambda) equals 550 nm are presented. Methods of enhancement in optical performance of these coatings are studied. The advantages of AR coatings formed by TiO2-MgF2 composite films over those similar systems consisting of TiO2-SiO2 composite films in both visible and near-IR regions are also presented.

  6. Spectral Imaging by Upconversion

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin; Pedersen, Christian

    2011-01-01

    We present a method to obtain spectrally resolved images using upconversion. By this method an image is spectrally shifted from one spectral region to another wavelength. Since the process is spectrally sensitive it allows for a tailored spectral response. We believe this will allow standard silicon based cameras designed for visible/near infrared radiation to be used for spectral images in the mid infrared. This can lead to much lower costs for such imaging devices, and a better performance.

  7. Human Contrast Threshold and Astronomical Visibility

    CERN Document Server

    Crumey, Andrew

    2014-01-01

    The standard visibility model in light pollution studies is the formula of Hecht (1947), as used e.g. by Schaefer (1990). However it is applicable only to point sources and is shown to be of limited accuracy. A new visibility model is presented for uniform achromatic targets of any size against background luminances ranging from zero to full daylight, produced by a systematic procedure applicable to any appropriate data set (e.g Blackwell (1946)), and based on a simple but previously unrecognized empirical relation between contrast threshold and adaptation luminance. The scotopic luminance correction for variable spectral radiance (colour index) is calculated. For point sources the model is more accurate than Hecht's formula and is verified using telescopic data collected at Mount Wilson by Bowen (1947), enabling the sky brightness at that time to be determined. The result is darker than the calculation by Garstang (2004), implying that light pollution grew more rapidly in subsequent decades than has been sup...

  8. Visible spectroscopy on ASDEX

    International Nuclear Information System (INIS)

    In this report visible spectroscopy and impurity investigations on ASDEX are reviewed and several sets of visible spectra are presented. As a basis for identification of metallic impurity lines during plasma discharges spectra from a stainless steel - Cu arc have been recorded. In a next step a spectrum overview of ASDEX discharges is shown which reveals the dominating role of lines from light impurities like carbon and oxygen throughout the UV and visible range (2000 A ? ? ? 8000 A). Metallic impurity lines of neutrals or single ionized atoms are observed near localized surfaces. The dramatic effect of impurity reduction by boronization of the vessel walls is demonstrated in a few examples. In extension to some ivesti-gations already published, further diagnostic applications of visible spectroscopy are presented. Finally, the hardware and software system used on ASDEX are described in detail. (orig.)

  9. Estimation of organic carbon deposition into forest ecosystems by determination of the spectral absorption of rainwater in range of ultraviolet radiation (SAC254)

    International Nuclear Information System (INIS)

    Organic compounds are mostly neglected within deposition measurement programs because their determination is expensive and complicated. A very simple and rapid estimation of total organic carbon (TOC) is possible by determination of the spectral absorption coefficient in the range of ultraviolet radiation at 254 nm wave-length (SAC254): TOC (mg/1) = 0,5 SAC254 (m?1) - 0,15 (author)

  10. Validation of HITEMP-2010 for carbon dioxide and water vapour at high temperatures and atmospheric pressures in 450-7600cm-1 spectral range

    DEFF Research Database (Denmark)

    Alberti, Michael; Weber, Roman

    2015-01-01

    The objective of the work is validation of HITEMP-2010 at atmospheric pressures and temperatures reaching 1770K. To this end, spectral transmissivities at 1cm-1 resolution and excellent signal-to-noise-ratio have been measured for 22 CO2/H2O/N2 mixtures. In this paper we consider the 450cm-1-7600cm-1 spectral range. The LbL calculations and their comparison with the measured spectra have clearly shown that HITEMP-2010 is an excellent database (superior to previous versions) for calculating emissivities and absorption coefficients for CO2 and H2O molecules in the 500-1770K range. Several absorption lines listed in HITEMP-2010 have not been observed in the measured spectra and/or are wrongly scaled with temperature. The complete (there are no missing bands) spectra spanning the 450-7600cm-1 range are appended as Supplementary Material.

  11. Evidence for Alteration in Chemical and Physical Properties of Water and Modulation of its Biological Functions by Sunlight Transmitted through Color Ranges of the Visible Spectrum-A Novel Study

    Directory of Open Access Journals (Sweden)

    M. Rajeswara Rao

    2005-08-01

    Full Text Available We investigated the changes in the properties of water when exposed to sunlight for 40 days. We hypothesize and prove that solar irradiation to water entraps electromagnetic radiation as potential energy, which becomes kinetic energy in various systems. It is postulated that photochemically-induced energy transfers, associated with individual spectral emission of visible spectrum of solar light, exert diverse influences on biological systems. Bottles of distilled water, individually wrapped in spectral-colored cellophane were exposed to sunlight and compared to an unwrapped bottle to determine chemical and physical changes as well as modifications of biological properties. Each bottle of water was named according to the color of cellophane paper with letter E (stands for exposed as a prefix with (E-violet, E-indigo, E-blue, E-green, E-yellow, E-orange, and Ered. E-control (without wrap was exposed to polychromatic sunlight. This study addresses two main issues viz., the chemical and physical changes in E-water and its effect on biological activities. Chemical and physical composition analysis using inductively coupled plasma atomic emission spectrometry; physical conductance by a Wheatstone Bridge type conductivity meter; osmolarity by a vapor pressure osmometer; and, salt solubility profile of 10% sodium bicarbonate were determined. Furthermore, testing the effect of E-waters on human lymphocyte proliferation, mosquito larvae hatching and seed germination determined the functional role of solar radiation through specific spectrum/s of visible light on various biological processes. We found that water exposed to visible spectral emissions of sunlight had an altered elemental composition, electrical conductance, osmolarity and salt-solubility, as well as differences in bio-modulatory effects. A gradual increase in leaching of Boron from Eviolet to E-red was noted. E-indigo showed maximal increase in electrical conductance and maximal salt solubility of sodium bicarbonate. E-blue inhibited phyto-hemagglutinin-induced immune cell proliferation and mosquito larvae hatching. E-orange stimulated root elongation in seed germination. We conclude that 40-day exposure of water to specific solar spectrum changes chemical and physical properties and influences on biological activity.

  12. General approach to high power, coherent visible and ultraviolet light sources

    OpenAIRE

    Andersen, Martin Thalbitzer; Tidemand-lichtenberg, Peter; Pedersen, Christian

    2010-01-01

    The main goal of this project is to develop a generic approach to synthesise any wavelength in the visible and UV spectral region based on sum frequency generation. The approach is based on a hybrid system combining solid state and semiconductor technology. The generation of light in the UV spectral region require nonlinear materials with a transparency range extending into the ultraviolet, the ability to sustain high photon energies and with the ability to obtain phasematch...

  13. Spectral characteristics of the second Stokes' parameter of scattered atmospheric visible light measured by the Multi-angle Polarimetric Hyper-Spectrometer (MPHS)

    Science.gov (United States)

    Jeong, U.; Lee, H.; Kim, J.; Spurr, R. J.

    2013-12-01

    Precise information on aerosol microphysical properties is necessary in order to understand various roles of the aerosols in the atmosphere. Since there are many different aerosol types and their temporal and spatial variations are considerably large, the retrieval of optical properties of the aerosols is difficult even with multiple constraints as provided by multi-spectral and multi-angle radiance measurements. Polarization measurements are highly sensitive to particle microphysics and can help to resolve this problem since they provide additional uncorrelated constraints for the retrieval. In this study, we established the Multi-angle Polarimetric Hyper-Spectrometer (MPHS) system. It measures the second Stokes parameter (Q) on the principal plane in the 400-700 nm wavelength domain with less than 1 nm spectral resolution and 0.5 degree field of view. The measurement uncertainty of Q is identified to be less than 0.5%. The measurements have been performed during the period of May - October 2012 which includes clear sky (AOD less then 0.1 with cloud free condition), cloudy sky, dust event, and haze events. The measurements were compared with aerosol optical properties from the Cimel sunphotometer. The measured Q has shown different spectral characteristics even with similar aerosol optical depth (AOD). The sensitivities of aerosol information on the measurements were also simulated with model calculations using the VLIDORT. The simulation results showed that the measurements of Q on the principal plane were highly sensitive to the aerosol size, real and imaginary refractive indices, AOD while the aerosol vertical distribution has shown negligible sensitivity on the measurements. Several inversion methods will be applied to these measurements in order to obtain more precise information on aerosols in the future study.

  14. A Novel Smart Pan/Tilt/Zoom Visible/Infrared Sensor for UAV On-Board Video Surveillance of Launch Range Project

    National Aeronautics and Space Administration — NASA has a pressing need for increasing the efficiency of launch range surveillance during mission launch operations. Difficulty in verifying a cleared range causes...

  15. Dispersive parameters for complex refractive index of p- and n-type silicon from spectrophotometric measurements in spectral range 200-2500 nm

    Science.gov (United States)

    El-Zaiat, El-Sayed Y.; Youssef, Gamal M.

    2015-01-01

    The spectral reflectance R(?) and spectral transmittance T(?) of p- and n-type silicon samples, having plane-parallel faces, are measured with a UV-vis-NIR spectrophotometer at room temperature. Measured data are introduced into analytical expressions to retrieve the complex refractive indices of silicon slabs across 200-2500 nm spectral range. The Wemple-DiDomenico dispersion model for real refractive index in the transparent region is used. Correlation between two atomic parameters and the dispersion constants of this dispersion model is established. Effects of doping on dispersion parameters, atomic parameters, the density of valence electrons, nv, coordination number, Nc, and the energy gap, Eg, are investigated. A dispersion model for the imaginary refractive index in the absorption region is investigated.

  16. AlGaInP quantum dots for optoelectronic applications in the visible spectral range; AlGaInP-Quantenpunkte fuer optoelektronische Anwendungen im sichtbaren Spektralbereich

    Energy Technology Data Exchange (ETDEWEB)

    Gerhard, Sven

    2013-01-10

    The scope of this work is the fabrication and characterization of AlGaInP quantum dots on GaP an GaAs substrates. Based on such quantum dots, semiconductor lasers have been realized, emitting between 660 nm and 730 nm at room temperature. The examination of broad-area lasers processed on these structures suggests that active layers of larger quantum dots with higher aluminium contents lead to lasers with better performance at similar emission wavelength. Additionally, quantum dots grown on GaP substrates have been characterized, that were embedded in AlGaP barriers. Since these barriers exhibit an indirect bandgap, a non-trivial band alignment within these structures is expected. In this work, numerical 3D-simulations are employed to calculate the band alignment including strain and internal fields. Also, ground state wavefunctions of charge carriers have been determined. A thorough comparison between theory and experiment connects the measured emission wavelength and luminescence intensities with calculated transition energies and wavefunction overlaps.

  17. UVMag: Space UV and visible spectropolarimetry

    CERN Document Server

    Pertenais, Martin; Pares, Laurent; Petit, Pascal; Snik, Frans; van harten, Gerard

    2014-01-01

    UVMag is a project of a space mission equipped with a high-resolution spectropolarimeter working in the UV and visible range. This M-size mission will be proposed to ESA at its M4 call. The main goal of UVMag is to measure the magnetic fields, winds and environment of all types of stars to reach a better understanding of stellar formation and evolution and of the impact of stellar environment on the surrounding planets. The groundbreaking combination of UV and visible spectropolarimetric observations will allow the scientists to study the stellar surface and its environment simultaneously. The instrumental challenge for this mission is to design a high-resolution space spectropolarimeter measuring the full-Stokes vector of the observed star in a huge spectral domain from 117 nm to 870 nm. This spectral range is the main difficulty because of the dispersion of the optical elements and of birefringence issues in the FUV. As the instrument will be launched into space, the polarimetric module has to be robust and...

  18. UVMag: Space UV and visible spectropolarimetry

    Science.gov (United States)

    Pertenais, Martin; Neiner, Coralie; Parès, Laurent P.; Petit, Pascal; Snik, Frans; van Harten, Gerard

    2014-07-01

    UVMag is a project of a space mission equipped with a high-resolution spectropolarimeter working in the UV and visible range. This M-size mission will be proposed to ESA at its M4 call. The main goal of UVMag is to measure the magnetic fields, winds and environment of all types of stars to reach a better understanding of stellar formation and evolution and of the impact of stellar environment on the surrounding planets. The groundbreaking combination of UV and visible spectropolarimetric observations will allow the scientists to study the stellar surface and its environment simultaneously. The instrumental challenge for this mission is to design a high-resolution space spectropolarimeter measuring the full- Stokes vector of the observed star in a huge spectral domain from 117 nm to 870 nm. This spectral range is the main difficulty because of the dispersion of the optical elements and of birefringence issues in the FUV. As the instrument will be launched into space, the polarimetric module has to be robust and therefore use if possible only static elements. This article presents the different design possibilities for the polarimeter at this point of the project.

  19. Spectroscopic evidence in the visible-ultraviolet energy range of surface functionalization sites in the multilayer Ti3C2 MXene

    Science.gov (United States)

    Magne, Damien; Mauchamp, Vincent; Célérier, Stéphane; Chartier, Patrick; Cabioc'h, Thierry

    2015-05-01

    Valence electron energy-loss (VEEL) spectroscopy in the transmission electron microscope is combined to ab initio calculations to investigate the dielectric properties of multilayer (ML) two-dimensional Ti3C2T2 (T ?OH or F) MXene. Besides evidencing important similarities between the ML-Ti 3C2T2 and TiC valence electron gas behaviors, a clear interband transition characteristic of the most stable site of the T functionalization groups is identified in the VEEL spectrum. This signature, highly dependent on the T -group localization on the surface, has a prominent effect on the optical properties of the ML, leading to 40 % variations in the optical conductivity in the middle of the visible spectrum. Such a dependence could be of crucial interest for optical transparent thin films or sensing applications.

  20. Simulation of a surface plasmon resonance-based fiber-optic sensor for gas sensing in visible range using films of nanocomposites

    International Nuclear Information System (INIS)

    A surface plasmon resonance-based fiber-optic sensor coated with nanocomposite film for sensing small concentrations of gases in the visible region of the electromagnetic spectrum has been analyzed. The nanocomposites considered are nanoparticles of Ag, Au and indium tin oxide (ITO) with their varying fraction dispersed in the host dielectric matrix of WO3, SnO2 and TiO2. For analysis, the effective indices of nanocomposites are calculated by adopting the Maxwell–Garnett model for nanoparticles of dimensions much smaller than the wavelength of radiation used for investigation. The effects of the volume fraction of nanoparticles in different nanocomposites and the thickness of the nanocomposite layer on the sensitivity of the sensor have been studied. It has been found that the sensor with the ITO–TiO2 coated nanocomposite with a small volume fraction and optimized film thickness possesses higher sensitivity

  1. Visible Earth

    Science.gov (United States)

    NASA's Visible Earth is a searchable directory of images, visualizations, and animations of the Earth. The images are also listed under the following categories: agriculture, atmosphere, biosphere, cryosphere, human dimensions, hydrosphere, land surface, oceans, radiance or imagery, solid earth, locations, and satellites. Accompanying each image are credits, data about the image, the satellite it was taken from, a description of what is shown, and a high-resolution viewable image.

  2. Visibility Matters

    DEFF Research Database (Denmark)

    Wildgaard, Lorna Elizabeth

    Research production, which earns universities money, is accredited publications in peer-reviewed journals and books. Increasing research productivity is one policy amongst many used by management to boost growth and income. It is time for a pat on the back, the growth of knowledge and visibility at RSLIS ranks us among the top 10 contributors to core LIS journals in a new international ranking. The management should be pleased.

  3. Visible and near-ultraviolet spectra of low-pressure rare-gas microwave discharges

    Science.gov (United States)

    Campbell, J. P.; Spisz, E. W.; Bowman, R. L.

    1971-01-01

    The spectral emission characteristics of three commercial low pressure rare gas discharge lamps wire obtained in the near ultraviolet and visible wavelength range. All three lamps show a definite continuum over the entire wavelength range from 0.185 to 0.6 micrometers. Considerable line emission is superimposed on much of the continuum for wavelengths greater than 0.35 micrometers. These sources were used to make transmittance measurements on quartz samples in the near ultraviolet wavelength range.

  4. Construction of TSL lector equipment with spectral resolution for the determination of thermally stimulated luminescence (TSL) properties of NaCl: Tl+ induced by UV-visible radiation

    International Nuclear Information System (INIS)

    A revision of physical models of thermally stimulated luminescence (TSL) in crystals induced by both ionizing and non-ionizing radiation is presented. Particular emphasis is given to the connection of TSL with other thermally stimulated processes and physico-chemical phenomena because basic information on physical mechanics for TSL can be obtained through them. Glow curves of TSL induced by UV-visible radiation in NaCl: Tl+ were measured. Additionally, the following spectrums were obtained for the same samples: optical absorption, excitation, fluorescent emission, and TSL emission. An optical absorption peak was correlated with the Thallium ion concentration. With respect to the TSL emission spectrums, some peaks associated to Thallium dimmers were at 298 and at 480 nm; others which were attributed to NaCl intrinsic properties were at 365, 430, 450 and 525 nm. Also TSL glow curves were studied as a function of the Thallium ion concentration (0.8 ppm to 14.8 ppm). They were de convoluted so as to calculate the activation energy, the frequency factor and the kinetic order for each separate TSL peak. Anomalous values were observed for some frequency factors. A method and TSL lector equipment to obtain TSL emission spectra were developed. (Author)

  5. Co2+:GGG nonlinear optical crystal for the 1.3 - 1.7 -?m spectral range

    International Nuclear Information System (INIS)

    A cobalt-doped GGG crystal is grown and its properties are studied. The absorption and fluorescence spectra in the visible and IR regions are measured. The absorption cross sections of the Co2+ ion in the GGG crystal at a wavelength of 1535 nm are determined for transitions from the ground (?gs = 4.8 x 10-20 cm2) and metastable states (?es = 1.4 x 10-20 cm2). Preliminary experimental results on Q-switching of erbium laser radiation by a Co2+:GGG passive Q-switch are presented. (active media)

  6. Broadband photon time-of-flight spectroscopy of pharmaceuticals and highly scattering plastics in the VIS and close NIR spectral ranges.

    Science.gov (United States)

    Khoptyar, Dmitry; Subash, Arman Ahamed; Johansson, Sören; Saleem, Muhammad; Sparén, Anders; Johansson, Jonas; Andersson-Engels, Stefan

    2013-09-01

    We present extended spectroscopic analysis of pharmaceutical tablets in the close near infrared spectral range performed using broadband photon time-of-flight (PTOF) absorption and scattering spectra measurements. We show that the absorption spectra can be used to perform evaluation of the chemical composition of pharmaceutical tablets without need for chemo-metric calibration. The spectroscopic analysis was performed using an advanced PTOF spectrometer operating in the 650 to 1400 nm spectral range. By employing temporal stabilization of the system we achieve the high precision of 0.5% required to evaluate the concentration of tablet ingredients. In order to further illustrate the performance of the system, we present the first ever reported broadband evaluation of absorption and scattering spectra from pure and doped Spectralon®. PMID:24103967

  7. Nondestructive assessment of fruit biological age in Brazilian mangoes by time-resolved reflectance spectroscopy in the 540-900 nm spectral range

    OpenAIRE

    Spinelli, L.; Rizzolo, A.; Vanoli, M.; Grassi, M.; Eccher Zerbini, P. C.; Meirelles Azevedo Pementel, A.; Torricelli, A.

    2013-01-01

    Time-resolved Reflectance Spectroscopy (TRS) in the 540–900 nm spectral range has been tested in order to assess nondestructively the biological age of Brazilian mangoes. To this purpose a TRS set-up has been used to measure absorption and scattering coefficients of 60 intact mango fruits (cultivar ‘Haden’), harvested in Minas Gerais, Brazil, and transported by plane to Milan, Italy. Flesh firmness, pulp color, and absorbance spectra by reflectance were determined on the same fruit, whi...

  8. Spectrometry of minor planets. Spectral curve of the 3 Juno asteroid in the 0.44-0.56 ?m range

    International Nuclear Information System (INIS)

    The absorption band near 0.5 ?m has been found in the 3 Juno spectrum obtained with ? 25 A resolution. This band is caused by d-electrons transitions of Fe2+ ion in pyroxene. Taking into account the location of the asteroid on the spectral parameters diagrams for light stony meteorites it is concluded that in the surface material of the 3 Juno olivine abundance is much less than pyroxene one and the metallic phase is probably present

  9. Spectral analysis of ICRF [Ion Cyclotron Range of Frequencies] wave field measurements in the Tara Central Cell

    International Nuclear Information System (INIS)

    A simple spectral analysis technique has been developed to analyse the digital signals from an array of magnetic probes for ICRF field measurements in the Tara Tandem Mirror central cell. The wave dispersion relations of both the applied ICRF and the Alfven Ion Cyclotron Instability have been studied and the waves have been identified as slow in cyclotron waves. The radial profiles of field amplitude and wave vectors were also generated. 9 refs., 10 figs

  10. InAs1-xSbx photodiodes for the spectral range of 3-5 ?m

    International Nuclear Information System (INIS)

    High-performance InAs1-xSbx photodiode structures (x=0.12-0.14) have been grown near lattice-matched on InAs (111) substrats by liquid phase epitaxy. Spectral response, current-voltage characteristics, differential resistance, R0 and detectivity, D*, were studied. Detector noises were calculated and compared with the experimental data. It was found that generation-recombination noises dominated at T=77-200 K

  11. Experimental investigation and simulation of the output characteristics of powerful cw diode lasers operating in the spectral range 808 nm with a total efficiency of up to 50%

    International Nuclear Information System (INIS)

    An experimental investigation was made of the main output and electrical parameters of cw diode lasers with an output of 1 W in the spectral range 808 nm at temperatures in the range 10-45 0C. The width of the stripe contact was 100 mm. A numerical simulation yielded the values of the threshold current density, of the external differential quantum efficiency, and of the total efficiency of diode lasers generating multimode radiation. The results obtained made it possible to optimise the design parameters of the cavity. (lasers, active media)

  12. Optical Properties of TiO2-SiO2 Glass Over a Wide Spectral Range

    International Nuclear Information System (INIS)

    Optical properties of vitreous SiO2 with 7.4 wt.% TiO2 are found by dispersion analysis of reflectivity measured in the infrared, visible, and ultraviolet augmented with literature values of vacuum-ultraviolet reflectivity and absorption. The principal infrared absorption associated with the titanium dopant occurs at 950 cm-1 in a deep minimum of the host silica absorption. We attribute this to a perturbation of the silica's absorption at 1076 cm-1 involving oxygen atoms bridging SiO4 and TiO4 tetrahedra. Strong ultraviolet absorptions of Ti4+ occur just below the silica exciton peak between 5.5 and 7.8 eV. We attribute these to charge-transfer transitions at TiO4 tetrahedra; i.e., bound excitons consisting of a Ti3+ ion and a hole shared by four oxygen neighbours

  13. Excited-state absorption spectroscopy of Nd3+:SrF2 crystals in the 1280 - 1320 nm spectral wavelength range

    International Nuclear Information System (INIS)

    The excited-state absorption (ESA) in Nd3+:SrF2 crystals was investigated in the 1280 - 1320 nm spectral wavelength range by selective laser excitation. It was found that, on excitation at wavelengths of 743 and 800.5 nm, there is no ESA in the ranges 1304 - 1309 and 1295 - 1297 nm. Weak ESA bands are observed in the 1297 - 1304 and 1309 - 1320 nm ranges and the differential ESA cross section does not exceed 0.3 x 10-21 cm2 . The results indicate that the ESA does not preclude the use of an Nd3+:SrF2 crystal as the amplifying medium in the wavelength range 1280 - 1320 nm. (active media)

  14. Detector calibration at the radiometry laboratory of the Physikalisch-Technische Bundesanstalt in the VUV and soft x-ray spectral ranges using synchrotron radiation

    Science.gov (United States)

    Lederer, Thomas; Rabus, Hans; Scholze, Frank; Thornagel, R.; Ulm, Gerhard

    1995-06-01

    In the vacuum ultraviolet and soft x-ray spectral ranges the radiometry laboratory of the Physikalisch-Technische Bundesanstalt at the synchrotron radiation facility BESSY offers two different methods for the calibration of radiation detectors. The electron storage ring BESSY, in combination with suitable monochromators, reproducible produces monochromatic radiation of tunable photon energy, high spectral purity, and high radiant power which can be reduced by twelve orders of magnitude. With this source of monochromatic radiation a cryogenic electrical substitution radiometer (ESR) is operated as a primary detector standard in the photon energy range from 3 eV to 1500 eV. The ESR is optimized for synchrotron radiation, capable of measuring radiant power in the order of some (mu) W with an uncertainty below 0.2%. Radiation detectors can be calibrated against the ESR with uncertainties well below 1%. Recent progress in this field will be demonstrated for the calibration of photodiodes. The electron storage ring BESSY is also used as a primary source standard, in the photon energy range from the infrared to the soft x-ray range. The spectral and spatial distribution of the broadband radiation, emitted in the range from 1 eV to 15 keV, is calculable from the known storage ring parameters with uncertainties from 0.04% to 0.35%, respectively. This allows the detection efficiency of energy-dispersive detectors such as solid-state detectors, charge- coupled devices, and others to be determined, provided the detector response function to monochromatic radiation is measured as well.

  15. Modifying ultrafast optical response of sputtered VOX nanostructures in a broad spectral range by altering post annealing atmosphere

    International Nuclear Information System (INIS)

    Nanostructured VOX thin films were grown in a dc magnetron sputter system under two different Ar:O2 gas flow ratios. The films were annealed under vacuum and various ratios of O2/N2 atmospheres. The insulator-to-metal transition properties of the thin films were investigated by temperature dependent resistance measurement. Photo induced insulator-to-metal transition properties were investigated by Z-scan and ultrafast white light continuum pump probe spectroscopy measurements. Experiments showed that not only insulator-to-metal transition, but also wavelength dependence (from NIR to VIS) and time scale (from ns to ultrafast) of nonlinear optical response of the VOX thin films could be fine tuned by carefully adjusting post annealing atmosphere despite different initial oxygen content in the production. Fabricated VO2 thin films showed reflection change in the visible region due to photo induced phase transition. The results have general implications for easy and more effective fabrication of the nanostructured oxide systems with controllable electrical, optical, and ultrafast optical responses. (paper)

  16. Photovoltaic detector based on type II heterostructure with deep AlSb/InAsSb/AlSb quantum well in the active region for the midinfrared spectral range

    International Nuclear Information System (INIS)

    Photodetectors for the spectral range 2–4 ?m, based on an asymmetric type-II heterostructure p-InAs/AlSb/InAsSb/AlSb/(p, n)GaSb with a single deep quantum well (QW) or three deep QWs at the heterointerface, have been grown by metal-organic vapor phase epitaxy and analyzed. The transport, luminescent, photoelectric, current-voltage, and capacitance-voltage characteristics of these structures have been examined. A high-intensity positive and negative luminescence was observed in the spectral range 3–4 ?m at high temperatures (300–400 K). The photosensitivity spectra were in the range 1.2–3.6 ?m (T = 77 K). Large values of the quantum yield (? = 0.6?0.7), responsivity (S? = 0.9?1.4 A W–1), and detectivity (D*? = 3.5 × 1011 to 1010 cm Hz1/2 W?1) were obtained at T = 77–200 K. The small capacitance of the structures (C = 7.5 pF at V = ?1 V and T = 300 K) enabled an estimate of the response time of the photodetector at ? = 75 ps, which corresponds to a bandwidth of about 6 GHz. Photodetectors of this kind are promising for heterodyne detection of the emission of quantum-cascade lasers and IR spectroscopy.

  17. Specific features of diffuse reflection of human face skin for laser and non-laser sources of visible and near-IR light

    Science.gov (United States)

    Dolotov, L. E.; Sinichkin, Yu P.; Tuchin, Valerii V.; Al'tshuler, G. B.; Yaroslavskii, I. V.

    2011-04-01

    The specific features of diffuse reflection from different areas of human face skin for laser and non-laser sources of visible and near-IR light have been investigated to localise the closed-eye (eyelid) region. In the visible spectral range the reflection from the eyelid skin surface can be differentiated by measuring the slope of the spectral dependence of the effective optical density of skin in the wavelength range from 650 to 700nm. In the near-IR spectral range the reflectances of the skin surface at certain wavelengths, normalised to the forehead skin reflectance, can be used as a criterion for differentiating the eyelid skin. In this case, a maximum discrimination is obtained when measuring the skin reflectances at laser wavelengths of 1310 and 1470nm, which correspond to the spectral ranges of maximum and minimum water absorption.

  18. Specific features of diffuse reflection of human face skin for laser and non-laser sources of visible and near-IR light

    International Nuclear Information System (INIS)

    The specific features of diffuse reflection from different areas of human face skin for laser and non-laser sources of visible and near-IR light have been investigated to localise the closed-eye (eyelid) region. In the visible spectral range the reflection from the eyelid skin surface can be differentiated by measuring the slope of the spectral dependence of the effective optical density of skin in the wavelength range from 650 to 700nm. In the near-IR spectral range the reflectances of the skin surface at certain wavelengths, normalised to the forehead skin reflectance, can be used as a criterion for differentiating the eyelid skin. In this case, a maximum discrimination is obtained when measuring the skin reflectances at laser wavelengths of 1310 and 1470nm, which correspond to the spectral ranges of maximum and minimum water absorption. (optical technologies in biophysics and medicine)

  19. Monitoring Urban Wastewaters’ Characteristics by Visible and Short Wave Near-Infrared Spectroscopy

    Directory of Open Access Journals (Sweden)

    Ignacio Melendez-Pastor

    2013-12-01

    Full Text Available On-line monitoring of wastewater parameters is a major scientific and technical challenge because of the great variability of wastewater characteristics and the extreme physical-chemical conditions that endure the sensors. Wastewater treatment plant managers require fast and reliable information about the input sewage and the operation of the different treatment stages. There is a great need for the development of sensors for the continuous monitoring of wastewater parameters. In this sense, several optical systems have been evaluated. This article presents an experimental laboratory-based approach to quantify commonly employed urban wastewater parameters, namely biochemical oxygen demand in five days (BOD5, chemical oxygen demand (COD, total suspended solids (TSS, and the ratio BOD5:COD, with a visible and short wave near infrared (V/SW-NIR spectrometer (400–1000 nm. Partial least square regression (PLSR models were developed in order to quantify the wastewater parameters with the recorded spectra. PLSR models were developed for the full spectral range and also for the visible and near infrared spectral ranges separately. Good PLSR models were obtained with the visible spectral range for BOD5 (RER = 9.64, COD (RER = 10.88, and with the full spectral range for the TSS (RER = 9.67. The results of this study show that V/SW-NIR spectroscopy is a suitable technique for on-line monitoring of wastewater parameters.

  20. Visible Light Communication

    Directory of Open Access Journals (Sweden)

    Rajan Sagotra, Reena Aggarwal

    2013-04-01

    Full Text Available Visible light communication (VLC is becoming an alternative choice for next-generation wireless technology by offering low cost, unregulated bandwidth and ubiquitous infrastructures support. This technology is envisioned to be used in a wide range of applications both indoor as well as outdoor. Visible Light Communication (VLC uses light emitting diodes (LEDs, for the dual role of illumination and data transmission. With this leading edge technology, data including video and audio, internet traffic etc can be transmitted at high speeds using LED light. Using LEDs is helping to drive this technology in the form of Visible Light Communication (VLC. In this paper, a visible light communications system is proposed that employs wavelength division multiplexing, to transmit multiple data streams from different data sources simultaneously andtransmission of audio song and also an image was demonstrated by using LED light. Not limit to this, multiple source signals simultaneously in different frequency bands were transmitted through the LED circuitry, and the signals were recovered successfully. This demonstrates the feasibility studies of our design in signals broadcasting

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

    International Nuclear Information System (INIS)

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

  2. Monolithic integration of InGaN segments emitting in the blue, green, and red spectral range in single ordered nanocolumns

    Energy Technology Data Exchange (ETDEWEB)

    Albert, S.; Bengoechea-Encabo, A.; Sanchez-Garcia, M. A.; Calleja, E. [ISOM and Dept. Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Kong, X.; Trampert, A. [Paul-Drude-Institut fuer Festkoeperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2013-05-06

    This work reports on the selective area growth by plasma-assisted molecular beam epitaxy and characterization of InGaN/GaN nanocolumnar heterostructures. The optimization of the In/Ga and total III/V ratios, as well as the growth temperature, provides control on the emission wavelength, either in the blue, green, or red spectral range. An adequate structure tailoring and monolithic integration in a single nanocolumnar heterostructure of three InGaN portions emitting in the red-green-blue colors lead to white light emission.

  3. Parametric modeling of the dielectric function and identification of the critical point of a CdMgTe alloy in the vacuum ultraviolet spectral range

    International Nuclear Information System (INIS)

    We report the parameters necessary to construct the dielectric functions of Cd1-xMgxTe ternary alloys at room temperature for arbitrary compositions from x = 0 to x = 0.5. The experimental spectra were measured by using vacuum ultraviolet spectroscopic ellipsometry in the spectral range from 0.7 to 9.0 eV. By performing a band structure calculation with the linear augmented Slatertype orbital method, we newly identify the four higher band gaps as E2 + ?2, E2(?), E2(?), and E'1 transitions.

  4. Full-range polarization-sensitive swept-source optical coherence tomography by simultaneous transversal and spectral modulation.

    Science.gov (United States)

    Yamanari, Masahiro; Makita, Shuichi; Lim, Yiheng; Yasuno, Yoshiaki

    2010-06-21

    Polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) is used to measure three-dimensional phase-retardation images of birefringent biological tissue in vivo. PS-SS-OCT with continuous source polarization modulation is used to multiplex the incident states of polarization in the signal frequency of each A-scan. Although it offers the advantage of measurement speed that is as high as that of standard SS-OCT, its disadvantage is low axial measurement range. To overcome this drawback, we employed the B-M-mode scan (BM-scan) method, which removes complex conjugate ambiguity by applying phase modulation along the transversal scanning direction. Since polarization modulation and BM-scan are applied in different scanning directions, these methods can be combined to make the optimum use of both full range and polarization-sensitive imaging. Phase fluctuations that cause measurement failure were numerically canceled before demodulating the B-scan oriented modulation. After removing complex conjugate artifacts, the axial measurement range was 5.35 mm, and the signal-to-conjugate ratio was 40.5 dB. We demonstrated retinal imaging using the PS-SS-OCT system with a frequency-swept laser at a center wavelength of 1064 nm and an axial resolution of 11.4 microm in tissue. Full-range polarization-sensitive retinal images showed characteristic birefringence of fibrous tissues such as retinal nerve fiber, sclera, and lamina cribrosa. PMID:20588529

  5. Spectroscopic Study of Human Teeth and Blood from Visible to Terahertz Frequencies for Clinical Diagnosis of Dental Pulp Vitality

    Science.gov (United States)

    Hirmer, Marion; Danilov, Sergey N.; Giglberger, Stephan; Putzger, Jürgen; Niklas, Andreas; Jäger, Andreas; Hiller, Karl-Anton; Löffler, Susanne; Schmalz, Gottfried; Redlich, Britta; Schulz, Irene; Monkman, Gareth; Ganichev, Sergey D.

    2012-03-01

    Transmission spectra of wet human teeth and dentin slices, together with blood of different flow rates were investigated. The measurements carried out over a wide spectral range, from visible light down to terahertz radiation. The results make it possible to find the optimum light frequency for an all-optical determination of pulpal blood flow and, consequently, for clinically diagnosis of tooth vitality.

  6. High resolution, large spectral range, in variable-included-angle soft X-ray monochromators using a plane VLS grating

    International Nuclear Information System (INIS)

    We give a unified discussion of two different approaches to the design of grazing incidence monochromators with a variable line spacing (VLS) grating for soft X-ray undulator sources. Neither one uses an entrance slit and both work with a fixed position exit slit. In one approach, being constructed at LNLS and designed for the energy range 100< E<1000eV, the choice of the VLS parameters allows for the operation at a variable c-value with a single plane grating and little sacrifice in the maximum resolving power. In this case source size limited resolving power of circa 40000 is expected at 100eV. In the second approach, for the storage ring in Wisconsin, two gratings covering the energy range 40< E<1500eV are used, one capable of delivering a resolving power larger than 20000 at 860eV and the other lower resolving power but much higher flux

  7. Simulation of laser propagation through a three-layer human skin model in the spectral range from 1000 to 1900 nm

    Science.gov (United States)

    Nasouri, Babak; Murphy, Thomas E.; Berberoglu, Halil

    2014-07-01

    For understanding the mechanisms of low-level laser/light therapy (LLLT), accurate knowledge of light interaction with tissue is necessary. We present a three-dimensional, multilayer reduced-variance Monte Carlo simulation tool for studying light penetration and absorption in human skin. Local profiles of light penetration and volumetric absorption were calculated for uniform as well as Gaussian profile beams with different spreads over the spectral range from 1000 to 1900 nm. The results showed that lasers within this wavelength range could be used to effectively and safely deliver energy to specific skin layers as well as achieve large penetration depths for treating deep tissues, without causing skin damage. In addition, by changing the beam profile from uniform to Gaussian, the local volumetric dosage could increase as much as three times for otherwise similar lasers. We expect that this tool along with the results presented will aid researchers in selecting wavelength and laser power in LLLT.

  8. Spectral evolution of star clusters in the Large Magellanic Cloud: I. Blue concentrated clusters in the age range 40-300 Myr

    CERN Document Server

    Santos, J F C; Ahumada, A V; Bica, E; Piatti, A E; Parisi, M C

    2005-01-01

    Integrated spectroscopy of a sample of 17 blue concentrated Large Magellanic Cloud (LMC) clusters is presented and its spectral evolution studied. The spectra span the range ~3600-6800A with a resolution of ~14A FWHM, being used to determine cluster ages and, in connection with their spatial distribution, to explore the LMC structure and cluster formation history. Cluster reddening values were estimated by interpolation, using the available extinction maps. We used two methods to derive cluster ages: (i) template matching, in which line strengths and continuum distribution of the cluster spectra were compared and matched to those of template clusters with known astrophysical properties, and (ii) equivalent width (EW) method, in which new age/metallicity calibrations were used together with diagnostic diagrams involving the sum of EWs of selected spectral lines (KCaII, G band (CH), MgI, Hdelta, Hgamma and Hbeta). The derived cluster ages range from 40Myr (NGC2130 and SL237) to 300Myr (NGC1932 and SL709), a goo...

  9. Incremental Visualizer for Visible Objects

    DEFF Research Database (Denmark)

    Bukauskas, Linas; BØhlen, Michael Hanspeter

    2004-01-01

    This paper discusses the integration of database back-end and visualizer front-end into a one tightly coupled system. The main aim which we achieve is to reduce the data pipeline from database to visualization by using incremental data extraction of visible objects in a fly-through scenarios. We also argue that passing only relevant data from the database will substantially reduce the overall load of the visualization system. We propose the system Incremental Visualizer for Visible Objects (IVVO) which considers visible objects and enables incremental visualization along the observer movement path. IVVO is the novel solution which allows data to be visualized and loaded on the fly from the database and which regards visibilities of objects. We run a set of experiments to convince that IVVO is feasible in terms of I/O operations and CPU load. We consider the example of data which uses visibility ranges and show that considering visibility ranges is crucial when considering incremental visible object extraction.

  10. Tailoring of the free spectral range and geometrical cavity dispersion of a microsphere by a coating layer.

    Science.gov (United States)

    Risti?, Davor; Mazzola, Maurizio; Chiappini, Andrea; Rasoloniaina, Alphonse; Féron, Patrice; Ramponi, Roberta; Righini, Giancarlo C; Cibiel, Gilles; Ivanda, Mile; Ferrari, Maurizio

    2014-09-01

    The modal dispersion of a whispering gallery mode (WGM) resonator is a very important parameter for use in all nonlinear optics applications. In order to tailor the WGM modal dispersion of a microsphere, we have coated a silica microsphere with a high-refractive-index coating in order to study its effect on the WGM modal dispersion. We used Er(3+) ions as a probe for a modal dispersion assessment. We found that, by varying the coating thickness, the geometrical cavity dispersion can be used to shift overall modal dispersion in a very wide range in both the normal and anomalous dispersion regime. PMID:25166102

  11. Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 8

    OpenAIRE

    Buehler, S. A.; Defer, E.; Evans, F.; Eliasson, S.; Mendrok, J.; Eriksson, P.; Lee, C.; Jime?nez, C.; Prigent, C.; Crewell, S.; Kasai, Y.; Bennartz, R.; Gasiewski, A. J.

    2012-01-01

    Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized "essential climate variable" ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudI...

  12. Modification of modulated plasma plumes for the quasi-phase-matching of high-order harmonics in different spectral ranges

    Science.gov (United States)

    Ganeev, R. A.; Boltaev, G. S.; Sobirov, B.; Reyimbaev, S.; Sherniyozov, H.; Usmanov, T.; Suzuki, M.; Yoneya, S.; Kuroda, H.

    2015-01-01

    We demonstrate the technique allowing the fine tuning of the distance between the laser-produced plasma plumes on the surfaces of different materials, as well as the variation of the sizes of these plumes. The modification of plasma formations is based on the tilting of the multi-slit mask placed between the heating laser beam and target surface, as well as the positioning of this mask in the telescope placed on the path of heating radiation. The modulated plasma plumes with the sizes of single plume ranging between 0.1 and 1 mm were produced on the manganese and silver targets. Modification of the geometrical parameters of plasma plumes proved to be useful for the fine tuning of the quasi-phase-matched high-order harmonics generated in such structures during propagation of the ultrashort laser pulses. We show the enhancement of some groups of harmonics along the plateau range and the tuning of maximally enhanced harmonic by variable modulation of the plasma.

  13. Resonant Visible Light Modulation with Graphene

    CERN Document Server

    Yu, Renwen; de Abajo, F Javier Garcia

    2015-01-01

    Fast modulation and switching of light at visible and near-infrared (vis-NIR) frequencies is of utmost importance for optical signal processing and sensing technologies. No fundamental limit appears to prevent us from designing wavelength-sized devices capable of controlling the light phase and intensity at gigaherts (and even terahertz) speeds in those spectral ranges. However, this problem remains largely unsolved, despite recent advances in the use of quantum wells and phase-change materials for that purpose. Here, we explore an alternative solution based upon the remarkable electro-optical properties of graphene. In particular, we predict unity-order changes in the transmission and absorption of vis-NIR light produced upon electrical doping of graphene sheets coupled to realistically engineered optical cavities. The light intensity is enhanced at the graphene plane, and so is its absorption, which can be switched and modulated via Pauli blocking through varying the level of doping. Specifically, we explor...

  14. Atmospheric aerosols, humidity, and visibility

    Energy Technology Data Exchange (ETDEWEB)

    Covert, D.S.; Waggoner, A.P.; Weiss, R.E.; Ahlquist, N.C.; Charlson, R.J.

    1980-01-01

    Aerosol properties such as particle size distribution, particle mass, and the chemical composition in the optical size range (0.1-0.2 microns in diameter), where they interact most effectively with visible light, are discussed on a physical and quantitative basis with reference to visibility reduction. It is shown that the degradation of visual range by aerosol particles is due to the accumulation mode, except in dust storms and fog relative humidity has predictable and measurable effects on visual range, which are small if relative humidity is less than 70%.

  15. Polylogarithmic representation of radiative and thermodynamic properties of thermal radiation in a given spectral range: I. Blackbody radiation

    CERN Document Server

    Fisenko, Anatoliy I

    2014-01-01

    Using polylogarithm functions the exact analytical expressions for the radiative and thermodynamic properties of blackbody radiation, such as the Wien displacement law, Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, and pressure in the finite range of frequencies are constructed. The obtained expressions allow us to tabulate these functions in various finite frequency bands at different temperatures for practical applications. As an example, the radiative and thermodynamic functions using experimental data for the monopole spectrum of the Cosmic Microwave Background (CMB) radiation measured by the COBE FIRAS instrument in the 60 - 600 GHz frequency interval at the temperature T = 2.725 K are calculated. The expressions obtained for the radiative and thermodynamic functions can be easily presented in wavelength and wavenumber domains.

  16. Dielectric function in the NIR-VUV spectral range of (In{sub x}Ga{sub 1?x}){sub 2}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt-Grund, R., E-mail: Schmidt-Grund@physik.uni-leipzig.de; Kranert, C.; Böntgen, T.; Wenckstern, H. von; Krauß, H.; Grundmann, M. [Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Universität Leipzig, Linnéstr. 5, D-04103 Leipzig (Germany)

    2014-08-07

    We determined the dielectric function of the alloy system (In{sub x}Ga{sub 1?x}){sub 2}O{sub 3} by spectroscopic ellipsometry in the wide spectral range from 0.5?eV to 8.5?eV and for In contents ranging from x?=?0.02 to x?=?0.61. The predicted optical transitions for binary, monoclinic ?-Ga{sub 2}O{sub 3}, and cubic bcc-In{sub 2}O{sub 3} are well reflected by the change of the dielectric functions' lineshape as a function of the In content. In an intermediate composition range with phase-separated material (x???0.3…0.4), the lineshape differs considerably, which we assign to the presence of the high-pressure rhombohedral InGaO{sub 3}-II phase, which we also observe in Raman experiments in this range. By model analysis of the dielectric function, we derived spectra of the refractive index and the absorption coefficient and energy parameters of electronic band-band transitions. We discuss the sub-band gap absorption tail in relation to the influence of the In 4d orbitals on the valence bands. The data presented here provide a basis for a deeper understanding of the electronic properties of this technologically important material system and may be useful for device engineering.

  17. The potential for extending the spectral range accessible to the european X-ray free electron laser in the direction of longer wavelengths

    CERN Document Server

    Saldin, E L; Yurkov, M V

    2004-01-01

    The baseline specifications of European XFEL give a range of wavelengths between 0.1 nm and 2 nm. This wavelength range at fixed electron beam energy 17.5 GeV can be covered by operating the SASE FEL with three undulators which have different period and tunable gap. A study of the potential for the extending the spectral range accessible to the XFEL in the direction of longer wavelengths is presented. The extension of the wavelength range to 6 nm would be cover the water window in the VUV region, opening the facility to a new class of experiments. There are at least two possible sources of VUV radiation associated with the X-ray FEL; the "low (2.5 GeV) energy electron beam dedicated" and the " 17.5 GeV spent beam parasitic" (or "after-burner") source modes. The second alternative, "after-burner undulator" is the one we regard as most favorable. It is possible to place an undulator as long as 80 meters after 2 nm undulator. Ultimately, VUV undulator would be able to deliver output power approaching 100 GW. A b...

  18. Salinity and spectral reflectance of soils

    Science.gov (United States)

    Szilagyi, A.; Baumgardner, M. F.

    1991-01-01

    The basic spectral response related to the salt content of soils in the visible and reflective IR wavelengths is analyzed in order to explore remote sensing applications for monitoring processes of the earth system. The bidirectional reflectance factor (BRF) was determined at 10 nm of increments over the 520-2320-nm spectral range. The effect of salts on reflectance was analyzed on the basis of 162 spectral measurements. MSS and TM bands were simulated within the measured spectral region. A strong relationship was found in variations of reflectance and soil characteristics pertaining to salinization and desalinization. Although the individual MSS bands had high R-squared values and 75-79 percent of soil/treatment combinations were separable, there was a large number of soil/treatment combinations not distinguished by any of the four highly correlated MSS bands under consideration.

  19. Recent advances in mid-IR optical fibres for chemical and biological sensing in the 2-15?m spectral range

    Science.gov (United States)

    Jha, Animesh; Jiang, Xin; Lousteau, Joris; Richards, Billy; Li, Hongxia; MacPherson, William N.; Bookey, Henry T.; Barton, James S.; Kar, Ajoy; Tsang, Yuen H.; Binks, David J.

    2009-06-01

    The invited paper explains the transmission properties of a range of near-, mid-, and far-IR optical fibres for their applications in chemical and biological sensing. Methods for the fabrication of single and multiple-core mid-IR fibres are discussed in view of controlling the thermal and viscosity properties for fibre drawing. In particular, the need for removing impurity bands in the 5000 to 1000 cm-1 range is explained. The importance of engineering multi-core fibres is also discussed for simultaneous measurements of Raman, IR and surface plasmon enhanced modes together with say, temperature using a mid-IR transmitting tellurite fibre e.g. in a chemical process. The paper explains the principles and advantages of evanescent wave coupling of light at the resonant frequency bands for chemical sensing using a fibre evanescent wave spectroscopic sensor having a GeTeSe chalcogenide fibre. Using fibre based techniques, measurements for Cr6+ ions in solution and As3+ and As5+ in solids have been characterized at visible and mid-IR regions, respectively. In this paper we also explain the importance of using mid-IR fibres for engineering novel laser and broadband sources for chemical sensing.

  20. The benefits of visibility

    International Nuclear Information System (INIS)

    The benefits of visibility improvement (or the damages with additional degradation) refer to increases (or decreases) in utility obtained in three different dimensions. The first of these is associated with the nature of the visibility change. Visual range may be improved so that features of an area become more distinct or the sky becomes clearer. Alternatively, normal features of an area may be marred, say by the site of a power plant or its plume (called plume blight). The second dimension is the location of the change: in an urban area, in a rural setting, or in a recreational area or area of particular beauty, such as the Grand Canyon. The third dimension is the type of value: use or non-use. Thus, a person who visits the Grand Canyon (or may visit it in the future) may hold use values for improving his view of the Canyon or its surroundings and may also old non-use values for improved visibility (whether for altruistic or other reasons) irrespective of present or planned visits. In all, therefore, there are 12 possible combinations of the elements in these three dimension, each of which is logically distinct from the others and which demands attention in the literature to derive willingness to pay (WTP)

  1. Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440-6810 A in the gamma Vel cluster, and calibration of spectral indices

    CERN Document Server

    Damiani, F; 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

    2014-01-01

    We study spectral diagnostics available from optical spectra with R=17000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the gamma Vel young cluster, in order to determine the fundamental parameters of these stars. We define a set of spectroscopic indices, sampling TiO bands, H-alpha core and wings, and many temperature- and gravity-sensitive lines. Combined indices tau (gamma) are also defined as Teff (log g) indicators over a wide spectral-type range. H-alpha emission-line indices are also chromospheric activity or accretion indicators. A metallicity-sensitive index is also defined. These indices enable us to find a clear difference between gravities of main-sequence and pre-main-sequence stars (as well as giant stars): the (gamma,tau) diagram is thus argued to be a promising distance-independent age measurement tool for young clusters. Our indices were quantitatively calibrated by means of photometry and literature reference spectra (from UVES-POP and ELODIE 3.1 ...

  2. The Herschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS): An overview of the 480 to 1902 GHz range

    CERN Document Server

    Kama, M; Dominik, C; Ceccarelli, C; Fuente, A; Caux, E; Higgins, R; Tielens, A G G M; Alonso-Albi, T

    2013-01-01

    Broadband spectral surveys of protostars offer a rich view of the physical, chemical and dynamical structure and evolution of star-forming regions. The Herschel Space Observatory opened up the terahertz regime to such surveys, giving access to the fundamental transitions of many hydrides and to the high-energy transitions of many other species. A comparative analysis of the chemical inventories and physical processes and properties of protostars of various masses and evolutionary states is the goal of the Herschel CHEmical Surveys of Star forming regions (CHESS) key program. This paper focusses on the intermediate-mass protostar, OMC-2 FIR 4. We obtained a spectrum of OMC-2 FIR 4 in the 480 to 1902 GHz range with the HIFI spectrometer onboard Herschel and carried out the reduction, line identification, and a broad analysis of the line profile components, excitation, and cooling. We detect 719 spectral lines from 40 species and isotopologs. The line flux is dominated by CO, H2O, and CH3OH. The line profiles ar...

  3. Demonstration of Magnetic Dipole Resonances of Dielectric Nanospheres in the Visible Region

    DEFF Research Database (Denmark)

    Evlyukhin, A. B.; Novikov, S. M.

    2012-01-01

    Strong resonant light scattering by individual spherical Si nanoparticles is experimentally demonstrated, revealing pronounced resonances associated with the excitation of magnetic and electric modes in these nanoparticles. It is shown that the low-frequency resonance corresponds to the magnetic dipole excitation. Due to high permittivity, the magnetic dipole resonance is observed in the visible spectral range for Si nanoparticles with diameters of similar to 200 nm, thereby opening a way to the realization of isotropic optical metamaterials with strong magnetic responses in the visible region.

  4. A novel collinear LiNbO3 acousto optical tunable filter with the improved range of transmission and spectral resolution

    Science.gov (United States)

    Arellanes, Adan Omar; Shcherbakov, Alexandre S.; Bertone, Emanuele

    2015-02-01

    This investigation represents a deep and advanced analysis of exploiting lithium niobate (LiNbO3) crystals for the collinear acousto-optical tunable filter (AOTF) in violet and near ultraviolet ranges. The selection of this material is motivated by its high birefringence, which is a key parameter for improving the resolution of AOTF. For this matter, we take into account all the important factors that can deteriorate the resolution in order to find extreme conditions for the best performances. In concrete, we analyze the well- known photorefraction effect accompanied by the light induced absorption in those ranges for the LiNbO3 crystals doped by selected materials. The best observed results have been obtained with magnesium (Mg) dopant in the congruent melt of LiNbO3, which also shifts the absorption edge far into the middle UV-range. This analysis had made it possible to formulate the physical criterion determining the enlarged practical limitations of the incident light power density. Together with previously studied non-uniformity and dispersion of the birefringence along the length of acousto-optical interaction in a crystal, we exploit the recently discovered and experimentally confirmed acousto-optical nonlinearity, which can improve the transmission function inherent in the collinear interaction via applying the acoustic waves of finite amplitude in the AOTF. As a result, the obtained spectral resolution is the best available for any collinear AOTF to our knowledge.

  5. The Herschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS). An overview of the 480 to 1902 GHz range

    Science.gov (United States)

    Kama, M.; López-Sepulcre, A.; Dominik, C.; Ceccarelli, C.; Fuente, A.; Caux, E.; Higgins, R.; Tielens, A. G. G. M.; Alonso-Albi, T.

    2013-08-01

    Context. Broadband spectral surveys of protostars offer a rich view of the physical, chemical and dynamical structure and evolution of star-forming regions. The Herschel Space Observatory opened up the terahertz regime to such surveys, giving access to the fundamental transitions of many hydrides and to the high-energy transitions of many other species. Aims: A comparative analysis of the chemical inventories and physical processes and properties of protostars of various masses and evolutionary states is the goal of the Herschel CHEmical Surveys of Star forming regions (CHESS) key program. This paper focusses on the intermediate-mass protostar, OMC-2 FIR 4. Methods: We obtained a spectrum of OMC-2 FIR 4 in the 480 to 1902 GHz range with the HIFI spectrometer onboard Herschel and carried out the reduction, line identification, and a broad analysis of the line profile components, excitation, and cooling. Results: We detect 719 spectral lines from 40 species and isotopologs. The line flux is dominated by CO, H2O, and CH3OH. The line profiles are complex and vary with species and upper level energy, but clearly contain signatures from quiescent gas, a broad component likely due to an outflow, and a foreground cloud. Conclusions: We find abundant evidence for warm, dense gas, as well as for an outflow in the field of view. Line flux represents 2% of the 7 L? luminosity detected with HIFI in the 480 to 1250 GHz range. Of the total line flux, 60% is from CO, 13% from H2O and 9% from CH3OH. A comparison with similar HIFI spectra of other sources is set to provide much new insight into star formation regions, a case in point being a difference of two orders of magnitude in the relative contribution of sulphur oxides to the line cooling of Orion KL and OMC-2 FIR 4. Appendix A is available in electronic form at http://www.aanda.org

  6. Ultraviolet and visible imaging and spectrographic imaging instrument.

    Science.gov (United States)

    Carbary, J F; Darlington, E H; Harris, T J; McEvaddy, P J; Mayr, M J; Peacock, K; Meng, C I

    1994-07-01

    The Ultraviolet and Visible Imaging and Spectrographic Imaging experiment consists of five spectrographic imagers and four imagers. These nine sensors provide spectrographic and imaging capabilities from 110 to 900 nm. The spectrographic imagers share an off-axis design in which selectable slits alternate fields of view (1.00° × 0.10° or 1.00° × 0.05°) and spectral resolutions between 0.5 and 4 nm. Image planes of the spectrographic imager have a programmable spectral dimension with 68, 136, or 272 pixels across each individual spectral band, and a programmable spatial dimension with 5, 10, 20, or 40 pixels across the 1° slit length. A scan mirror sweeps the slit through a second spatial dimension to generate a 1° × 1° spectrographic image once every 5, 10, or 20 s, depending on the scan rate. The four imagers provide narrow-field (1.28° × 1.59°) and wide-field (10.5° × 13.1°) viewing. Each imager has a six-position filter wheel that selects various spectral regimes and neutral densities. The nine sensors ut lize intensified CCD detectors that have an intrascene dynamic range of ~ 10(3) and an interscene dynamic range of ~ 10(5); neutral-density filters provide an additional dynamic range of ~ 10(2-3). The detector uses an automatic gain control that permits the sensors to adjust to scenes of varying intensity. The sensors have common boresights and can operate separately, simultaneously, or synchronously. To be launched aboard the Midcourse Space Experiment spacecraft in the mid-1990's, the ultraviolet and visible imaging and spectrographic imaging instrument will investigate a multitude of celestial, atmospheric, and point sources during its planned 4-yr life. PMID:20935774

  7. Visible, vacuum ultraviolet and x-ray spectroscopy using back-illuminated CCD detector

    International Nuclear Information System (INIS)

    Back-illuminated CCD detectors have been used for visible, VUV and x-ray spectroscopy. The results are compared with those generated by conventional detection systems such as the photodiode array with image intensifier or micro-channel plate. The use of the back-illuminated CCD demonstrated excellent qualities including low noise, a high level of spectral resolution and a greatly extended output dynamic range. Detailed results of the comparison are also discussed. (author)

  8. Visibly Pushdown Games

    OpenAIRE

    Loeding, Christof; Madhusudan, Parthasarathy; Serre, Olivier

    2004-01-01

    The class of visibly pushdown languages has been recently defined as a subclass of context-free languages with desirable closure properties and tractable decision problems. We study visibly pushdown games, which are games played on visibly pushdown systems where the winning condition is given by a visibly pushdown language. We establish that, unlike pushdown games with pushdown winning conditions, visibly pushdown games are decidable and are 2Exptime-complete. We also show that pushdown games...

  9. Glasses for seeing beyond visible.

    Science.gov (United States)

    Zhang, XiangHua; Bureau, Bruno; Lucas, Pierre; Boussard-Pledel, Catherine; Lucas, Jacques

    2008-01-01

    Conventional glasses based on oxides have a transparency limited by phonon absorption in the near IR region and have a limited interest for analyzing information located far beyond the visible. The IR spectral domain is nevertheless of prime interest, since it covers fundamental wavelength ranges used for thermal imaging as well as molecular vibrational signatures. Besides spectacular advances in the field of IR detectors, the main significant progresses are related to the development of IR glass optics, such as lenses or IR optical fibres. The field of IR glasses is almost totally dominated by glasses formed from heavy atoms such as the chalcogens S, Se and Te. Their transparency extends up to 12, 16 and 28 microm for sulfide-, selenide- and the new generation of telluride-based glasses, respectively. They cover the atmospheric transparency domains, 3-5 and 8-13 microm, respectively, at which the IR radiation can propagate allowing thermal imaging and night-vision operations through thick layers of atmosphere. The development of new glass compositions will be discussed on the basis of structural consideration with the objective of moulding low-cost lenses for IR cameras used, for instance, in car-driving assistance. Additionally, multimode, single-index, optical fibres operating in the 3 to 12 microm window developed for in situ remote evanescent-wave IR spectroscopy will also be mentioned. The detection of molecular IR signatures is applied to environmental monitoring for investigating the pollution of underground water with toxic molecules. The extension of this technique to the investigation of biomolecules in three different studies devoted to liver tissues analysis, bio-film formation, and cell metabolism will also be discussed. Finally we will mention the developments in the field of single-mode fibres operating around 10 mum for the Darwin space mission, which is aiming at discovering, signs of biological life in telluric earth-like exoplanets throughout the universe. PMID:18067106

  10. Spectral Tagging

    International Nuclear Information System (INIS)

    This research examines the feasibility of spectral tagging, which involves modifying the spectral signature of a target, e.g. by mixing an additive with the target's paint. The target is unchanged to the human eye, but the tag is revealed when viewed with a spectrometer. This project investigates a layer of security that is not obvious, and therefore easy to conceal. The result is a tagging mechanism that is difficult to counterfeit. Uniquely tagging an item is an area of need in safeguards and security and non-proliferation. The powdered forms of the minerals lapis lazuli and olivine were selected as the initial test tags due to their availability and uniqueness in the visible to near-infrared spectral region. They were mixed with paints and applied to steel. In order to verify the presence of the tags quantitatively, the data from the spectrometer was input into unmixing models and signal detection algorithms. The mixture with the best results was blue paint mixed with lapis lazuli and olivine. The tag had a 0% probability of false alarm and a 100% probability of detection. The research proved that spectral tagging is feasible, although certain tag/paint mixtures are more detectable than others

  11. Fabrication of multiple heterojunctions with tunable visible-light-active photocatalytic reactivity in BiOBr-BiOI full-range composites based on microstructure modulation and band structures.

    Science.gov (United States)

    Huang, Hongwei; Han, Xu; Li, Xiaowei; Wang, Shichao; Chu, Paul K; Zhang, Yihe

    2015-01-14

    The fabrication of multiple heterojunctions with tunable photocatalytic reactivity in full-range BiOBr-BiOI composites based on microstructure modulation and band structures is demonstrated. The multiple heterojunctions are constructed by precipitation at room temperature and characterized systematically. Photocatalytic experiments indicate that there are two types of heterostructures with distinct photocatalytic mechanisms, both of which can greatly enhance the visible-light photocatalytic performance for the decomposition of organic pollutants and generation of photocurrent. The large separation and inhibited recombination of electron-hole pairs rendered by the heterostructures are confirmed by electrochemical impedance spectra (EIS) and photoluminescence (PL). Reactive species trapping, nitroblue tetrazolium (NBT, detection agent of (•)O2(-)) transformation, and terephthalic acid photoluminescence (TA-PL) experiments verify the charge-transfer mechanism derived from the two types of heterostructures, as well as different enhancements of the photocatalytic activity. This article provides insights into heterostructure photocatalysis and describes a novel way to design and fabricate high-performance semiconductor composites. PMID:25525911

  12. Water vapor retrieval from OMI visible spectra

    Science.gov (United States)

    Wang, H.; Liu, X.; Chance, K.; González Abad, G.; Miller, C. Chan

    2014-06-01

    There are distinct spectral features of water vapor in the wavelength range covered by the Ozone Monitoring Instrument (OMI) visible channel. Although these features are much weaker than those at longer wavelengths, they can be exploited to retrieve useful information about water vapor. They have an advantage in that their small optical depth leads to fairly simple interpretation as measurements of the total water vapor column density. We have used the Smithsonian Astrophysical Observatory (SAO) OMI operational retrieval algorithm to derive the slant column density (SCD) of water vapor using the 430-480 nm spectral region after extensive optimization. We convert from SCD to vertical column density (VCD) using the air mass factor (AMF), which is calculated using look-up tables of scattering weights and assimilated water vapor profiles. Our Level 2 product includes not only water vapor VCD but also the associated scattering weights and AMF. In the tropics, our standard water vapor product has a median SCD of 1.3 × 1023 molecules cm-2 and a median relative uncertainty of about 11%, about a factor of 2 better than that from a similar OMI algorithm that uses a narrower retrieval window. The corresponding median VCD is about 1.2 × 1023 molecules cm-2. We have examined the sensitivities of SCD and AMF to various parameters and compared our results with those from the GlobVapour product, the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Aerosol Robotic NETwork (AERONET).

  13. Feature Point Descriptors: Infrared and Visible Spectra

    OpenAIRE

    Pablo Ricaurte; Carmen Chilán; Aguilera-Carrasco, Cristhian A.; Vintimilla, Boris X.; Sappa, Angel D.

    2014-01-01

    This manuscript evaluates the behavior of classical feature point descriptors when they are used in images from long-wave infrared spectral band and compare them with the results obtained in the visible spectrum. Robustness to changes in rotation, scaling, blur, and additive noise are analyzed using a state of the art framework. Experimental results using a cross-spectral outdoor image data set are presented and conclusions from these experiments are given.

  14. Measurement of a free spectral range of a Fabry–Perot cavity using frequency modulation and null method under off-resonance conditions

    International Nuclear Information System (INIS)

    In this paper, we discuss a method to measure the free spectral range (FSR) of a Fabry–Perot cavity (FP-cavity) using frequency modulation with one electric optical modulator (EOM) and the null method. A laser beam modulated by the EOM, to which a sine wave signal is supplied from a radio frequency (RF) oscillator, is incident on the FP-cavity. The transmitted or reflected light from the FP-cavity is observed and converted to an RF signal by a high-speed photodetector, and the RF signal is synchronously demodulated with a lock-in amplifier by referring to a cosine wave signal from the oscillator. We theoretically and experimentally demonstrate that the lock-in amplifier signal for the transmitted or reflected light becomes null with a steep slope when the modulation frequency is equal to the FSR under the condition that the carrier frequency of the laser is slightly detuned from the resonance of the FP-cavity. To reduce the measurement uncertainty for the FSR, we also discuss a selection method for laser power, a modulation index and the detuning shift of the carrier frequency, respectively

  15. Comparison between ultraviolet-visible and near-infrared elastic scattering spectroscopy of chemically induced melanomas in an animal model.

    Science.gov (United States)

    A'Amar, Ousama M; Ley, Ronald D; Bigio, Irving J

    2004-01-01

    The work reported compares elastic scattering spectroscopy (ESS) for diagnosis of pigmented skin lesions in two spectral regions: UV-visible and near infrared (NIR). Given the known strong absorption by melanin in the near-UV to mid-visible range of the spectrum, such a comparison can help determine the optimum wavelength range of ESS for diagnosis of pigmented skin lesions. For this purpose, four South American opossums are treated with dimethylbenz(a)anthracene on multiple dorsal sites to induce both malignant melanomas and benign pigmented lesions. Skin lesions are examined in vivo with ESS using both UV-visible and NIR, with wavelength ranges of 330 to 900 nm and 900 to 1700 nm, respectively. Both portable systems use the same fiber optic probe geometry. ESS measurements are made on the lesions, and spectral differences are grouped by diagnosis from standard histopathological procedure. Both ESS datasets show strong spectral trends with the histopathological assignments, and the data suggest a model for the underlying basis of the spectral distinction between benign and malignant pigmented nevi. PMID:15568954

  16. Visible Human Project

    Science.gov (United States)

    ... Sites Tools Media Productions Related Projects The Visible Human Project ® Overview The Visible Human Project ® is an outgrowth of the NLM's 1986 ... dimensional representations of the normal male and female human bodies. Acquisition of transverse CT, MR and cryosection ...

  17. Visible photon multiplication in Ce3+–Tb3+ doped borate glasses for enhanced solar cells

    Science.gov (United States)

    Yang, Peng; Chen, Baojie; Shen, Lifan; Bun Pun, Edwin Yue; Lin, Hai

    2014-11-01

    Visible photon multiplication is exposed in the Ce3+–Tb3+ doped alkaline-earth borate (LKZBSB) glass system. Efficient green and blue fluorescences originate from Tb3+ and Ce3+ emitting centres, respectively. Evaluation of absolute spectral parameters reveals that the quantum yield of Tb3+ single doped LKZBSB glasses is ~8% under UVA radiation. Furthermore, with the introduction of Ce3+ into the Tb3+ doping system, the effective excitation wavelength range and the emission intensity of Tb3+ in LKZBSB glasses are remarkably expanded and improved by a maximum sensitization factor of ~52 in the UVB spectral region. These results demonstrate that the Ce3+–Tb3+ doped LKZBSB glass system has promising potential as an efficient UV ? Visible radiation conversion layer for the enhancement of solar cell efficiency, including cells employed in outer space.

  18. The Use of UV, Visible and Near IR Solar Back Scattered Radiation to Determine Trace Gases

    Science.gov (United States)

    Richter, Andreas; Wagner, Thomas

    Satellite remote sensing in the near-IR, visible and UV spectral range makes use of absorption and emission processes of electromagnetic radiation corresponding to electronic transitions, combined with simultaneous rotational-vibrational molecular transitions. One important difference compared to atmospheric observations in the microwave and thermal IR spectral range is that, usually thermal emission can be neglected at short wavelengths (there might, however, be emissions from, for example, excited gases in the high atmosphere). Thus the observed spectral signatures can be directly related to absorption spectra of atmospheric constituents. The neglect of emission terms makes the spectral analysis in the UV/vis spectral range usually reasonably straight forward. Another important and related advantage is that from satellite observations in the UV/vis spectral region, information from all atmospheric height layers (including the near surface layers) can be obtained. This makes UV/vis satellite observations a powerful tool for the monitoring of atmospheric pollution and for the characterisation and quantification of emission sources which are usually located close to the ground. It should, however, also be noted that, in contrast to observations in the microwave or thermal IR, usually little or no information on the vertical distribution of a trace gas is obtained.

  19. The High-ORbit Ultraviolet-visible Satellite, HORUS

    Science.gov (United States)

    Scowen, Paul A.; Cooke, Brian; Beasley, Matthew; Siegmund, Oswald

    2013-09-01

    The High-ORbit Ultraviolet-visible Satellite (HORUS) is a 2.4-meter class space telescope that will conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. HORUS will provide 100× greater imaging efficiency and combines the resolution of STIS with the throughput of COS. The HORUS mission will contribute vital information on how solar systems form and whether habitable planets should be common or rare. It also will investigate the structure, evolution, and destiny of galaxies and the universe. This program relies on focused capabilities unique to space that no other planned NASA mission will provide: near-ultraviolet (UV)/visible (200-1100nm) wide-field (14' square), diffraction-limited imaging; and high-sensitivity, high-resolution FUV (100- 320nm) spectroscopy. From its baseline orbit at L2 HORUS will enjoy a stable environment for thermal and pointing control, and long-duration target visibility. The core HORUS design will provide wide field of view imagery and high efficiency point source far-ultraviolet (FUV) spectroscopy using a combination of spectral selection and field sharing.

  20. Global spectral irradiance variability and material discrimination at Boulder, Colorado.

    Science.gov (United States)

    Pan, Zhihong; Healey, Glenn; Slater, David

    2003-03-01

    We analyze 7,258 global spectral irradiance functions over 0.4-2.2 microm that were acquired over a wide range of conditions at Boulder, Colorado, during the summer of 1997. We show that low-dimensional linear models can be used to capture the variability in these spectra over both the visible and the 0.4-2.2 microm spectral ranges. Using a linear model, we compare the Boulder data with the previous study of Judd et al. [J. Opt. Soc. Am. 54, 1031 (1964)] over the visible wavelengths. We also examine the agreement of the Boulder data with a spectral database generated by using the MODTRAN 4.0 radiative transfer code. We use a database of 223 minerals to consider the effect of the spectral variability in the global spectral irradiance functions on hyperspectral material identification. We show that the 223 minerals can be discriminated accurately over the variability in the Boulder data with subspace projection techniques. PMID:12630837

  1. Performances of a CCD camera from 1- to 1100-nm spectral region

    Science.gov (United States)

    Poletto, Luca; Boscolo, Alessio; Pelizzo, Maria-Guglielmina; Placentino, Leonardo; Tondello, Giuseppe

    1997-09-01

    The performances of a CCD have been evaluated in a very wide spectral region, which comprises the near IR, the visible, the near and far UV, EUV and soft x-ray spectral regions. The CCD detector is a back illuminated one, 512 X 512 format, 24 X 24 micrometers 2 pixel. The measurements performed consist mainly on the determination of the quantum efficiency and of the uniformity of response in the 1 - 1100 nm spectral region. Three different experimental setup have been used for the various spectral range: a Czerny-Turner monochromator for the 1100 - 250 nm region, a Johnson-Onaka monochromator for the 250 - 30 nm region, and a grazing incidence monochromator for the 30 - 1 nm region. The tested CCD exhibits high values of quantum efficiency and a good uniformity of response in the analyzed spectral range.

  2. The Shining Future of UV Spectral Synthesis

    CERN Document Server

    Pellerin, Anne

    2009-01-01

    With the coming generation of instruments and telescopes capable of spectroscopy of high redshift galaxies, the spectral synthesis technique in the rest-frame UV and Far-UV range will become one of a few number of tools remaining to study their young stellar populations in detail. The rest-frame UV lines and continuum of high redshift galaxies, observed with visible and infrared telescopes on Earth, can be used for accurate line profile fitting such as PV@1118,1128A, CIII@1176A, and CIV@1550A. These lines are very precise diagnostic tools to estimate ages, metallicities, and masses of stellar populations. Here we discuss the potential for spectral synthesis of rest-frame UV spectra obtained at the Keck telescope. As an example, we study the 8 o'clock arc, a lensed galaxy at z=2.7322. We show that the poor spectral type coverage of the actual UV empirical spectral libraries limits the age and metallicity diagnostic. In order to improve our knowledge of high redshift galaxies using spectral synthesis, UV stella...

  3. Visible and UV emission spectroscopy

    International Nuclear Information System (INIS)

    Visible and ultra-violet emission spectroscopy is a well established plasma diagnostic technique extensively used in contemporary fusion experiments. Theoretical plasma models are required to derive the relevant physical parameters. These models are reviewed in the first part of this paper. They allow spectral line intensities and radiative power losses to be calculated from the knowledge of the detailed atomic physics processes occurring in the plasma. In tokamak plasma experiments, impurity contamination and transport are important concerns. Basic spectroscopic methods used in their understanding are described. They include the determination of impurity concentrations either by line emission modelling (through the use of an impurity transport code), or by direct charge-exchange recombination measurement. They also include the evaluation of neutral particle fluxes at the plasma periphery. Finally, the experimental techniques used in the derivation of impurity transport coefficients are reported

  4. About the estimation of cross sections and spectral distributions of (n, x n ? ) reaction products in the neutron energy range 10 - 20 MeV

    International Nuclear Information System (INIS)

    The excitation functions and spectral distributions of neutral products for the fast-neutron-induced reactions on nuclei 56 Fe, 93 Nb, 115 In have been calculated in the framework of the multistep statistical model with taking into account the preequilibrium processes. The influence of model prescription on the preequilibrium process contribution as well as the influence of the used level density and radiation strength functions on the energy spectra of secondary neutrons and ?-rays has been carefully examined too

  5. The Herschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS). An overview of the 480 to 1902 GHz range

    OpenAIRE

    Kama, M.; López-Sepulcre, A.; Dominik, C.; Ceccarelli, C.; Fuente, A.; Caux, E.; Higgins, R; Tielens, A. G. G. M; Alonso-Albi, T.

    2013-01-01

    Context. Broadband spectral surveys of protostars offer a rich view of the physical, chemical and dynamical structure and evolution of star-forming regions. The Herschel Space Observatory opened up the terahertz regime to such surveys, giving access to the fundamental transitions of many hydrides and to the high-energy transitions of many other species. Aims. A comparative analysis of the chemical inventories and physical processes and properties of protostars of various masses and evolut...

  6. All-fiber femtosecond Cherenkov laser at visible wavelengths

    DEFF Research Database (Denmark)

    Liu, Xiaomin; Lægsgaard, Jesper

    2013-01-01

    Fiber-optic Cherenkov radiation (CR), also known as dispersive wave generation or non-solitonic radiation, is produced in small-core photonic crystal fibers (PCF) when a soliton perturbed by fiber higher-order dispersion co-propagates with a dispersive wave fulfilling a certain phase-matching condition [1]. The resonant ultrafast wave conversion via the fiber-optic CR mechanism is instrumental for applications in biophotonics such as bio-imaging and microscopy [2]. In this work, we demonstrate a highly-stable all-fiber, fully monolithic CR system based on an Yb-fiber femtosecond laser, producing electrically tunable femtosecond CR output in the visible (VIS) spectral range of 580-630 nm, with the 3 dB spectral bandwidth not exceeding 36 nm, with average power in the milliwatt range. Relative intensity noise (RIN) of this laser, affecting the sensitivity of bio-imaging and microscopy systems, is found to be as low as -103 dBc/Hz. This is 2 orders of magnitudes lower noise as compared to spectrally-sliced supercontinuum, which is the current standard of ultrafast fiber-optic generation at visible wavelength. The layout of the laser system is shown in Fig. 1(a). The system consists of two parts: an all-fiber selfstabilized Yb-doped femtosecond laser [3,4] operating at 1035 nm central wavelength and 26.7 MHz repetition rate used as the pump source; and a spliced-on small-core nonlinear PCF NL-3.0-850 (NKT Photonics A/S) with zero-dispersion wavelength around 850 nm, used for Cherenkov wave conversion [5]. Bridge fibers are used in the CR link to enhance the conversion efficiency. Fig. 1(b) shows the far-field saturated visible images of the CR emitted from the laser system, generated as the pump power increases in the range 150 mW - 300 mW. The emitted CR spectra corresponding to different average output powers are shown in Fig. 1(c). When the average emitted CR power is increasing from 0.46 mW to 4.2 mW, the central wavelength is shifting from 630 nm to 580 nm, and the 3 dB bandwidth of the spectrum increases from14 nm to 36 nm. The physical mechanism of wavelength tunability with changing the pump power is related to different linear and nonlinear compression conditions for weaker and stronger pump laser pulses in the hollow-core pulse compressor and CR stages of the laser (Fig. 1(a)). Fig. 1 (d) shows the autocorrelation (AC) of the CR with the output power of 1.7 mW. The FWHM of the AC trace for the generated CR pulse is 160 fs. The FWHM of the AC of the input pump pulse at 1035 nm is 832 fs. The CR pulse is more than 5 times shorter than the pump pulse, as a result of the nonlinear pump pulse compression in the CR fiber link. We are currently working on achieving an even broader electrical tunability of the CR output, ideally covering the significant part of the visible spectral range.

  7. Visible Human Project®

    U.S. Department of Health & Human Services — The Visible Human Project® is the creation of complete, anatomically detailed, three-dimensional representations of the normal male and female human bodies....

  8. Predicting Visibility of Aircraft

    OpenAIRE

    Watson, Andrew; Ramirez, Cesar V.; Salud, Ellen

    2009-01-01

    Visual detection of aircraft by human observers is an important element of aviation safety. To assess and ensure safety, it would be useful to be able to be able to predict the visibility, to a human observer, of an aircraft of specified size, shape, distance, and coloration. Examples include assuring safe separation among aircraft and between aircraft and unmanned vehicles, design of airport control towers, and efforts to enhance or suppress the visibility of military and rescue vehicles. We...

  9. COLLI - a Monte Carlo program for calculating neutron spectral fluences in the energy range 10 keV to 20 MeV - description and application

    International Nuclear Information System (INIS)

    The program described can be applied to calculating the transport of neutrons through an arrangement of bodies that can be extensively varied in geometry and materials. The information obtainable by this program includes data on the spectral fluence of scattered neutrons for a set of up to 10 random measuring points. Fortran IV is the programming language. For the calculation of neutron interactions, point cross sections of the ENDF data library are used, either in the original version or in a condensed form. The data are processed for the following elements: Hydrogen, carbon, nitrogen, oxygen, aluminum, silicon, calcium, iron, copper, tungsten, and lead. (orig./HP)

  10. Two laser-produced plasmas method for absorption spectra and photoionization cross-sections measurements on light ions in the VUV and soft x-ray spectral range

    International Nuclear Information System (INIS)

    The method of using two laser produced plasmas, one acting as background continuum radiation source, the other as absorbing medium, for obtaining the absorption spectra and for measuring the photoionization cross-sections of low-Z ionic species is described. The basic principles of the experiment are discussed. The advantages of some technical solutions, like the use of stigmatic technique in VUV and XUV spectral regions, the use of detecting system using photodiode arrays, and the constrained deconvolution procedure adopted in data processing, are emphasized

  11. Two Laser-Produced Plasmas Method For Absorption Spectra And Photoionization Cross-Sections Measurements On Light Ions In The Vuv Dnd Soft X-Ray Spectral Range

    Science.gov (United States)

    Jannitti, E.; Nicolosi, P.; Tondello, G.

    1988-07-01

    The method of using two laser produced plasmas, one acting as background continuum radiation source, the other as absorbing medium, for obtaining the absorption spectra and for measuring the photoionization cross-sections of low-Z ionic species is described. The basic principles of the experiment are discussed. The advantages of some technical solutions, like the use of stigmatic technique in VUV and XUV spectral regions, the use of detecting system using photodiode arrays, and the constrained deconvolution procedure adopted in data processing, are emphasized.

  12. Frequency down-conversion of solid-state laser sources to the mid-infrared spectral range using non-oxide nonlinear crystals

    Science.gov (United States)

    Petrov, Valentin

    2015-07-01

    The development of parametric devices down-converting the laser frequency to the mid-infrared (3-30 ?m) based on non-oxide nonlinear optical crystals is reviewed. Such devices, pumped by solid-state laser systems operating in the near-infrared, fill in this spectral gap where no such lasers exist, on practically all time scales, from continuous-wave to femtosecond regime. All important results obtained so far with difference-frequency generation, optical parametric oscillation, generation and amplification are presented in a comparative manner, illustrating examples of recent achievements are given in more detail, and some special issues such as continuum and frequency comb generation or pulse shaping are also discussed. The vital element in any frequency-conversion process is the nonlinear optical crystal and this represents one of the major limitations for achieving high energies and average powers in the mid-infrared although the broad spectral tunability seems not to be a problem. Hence, an overview of the available non-oxide nonlinear optical materials, emphasizing new developments such as wide band-gap, engineered (mixed), and quasi-phase-matched crystals, is also included.

  13. Near infrared and visible luminescence of U3+-doped PbCl2 single crystals

    International Nuclear Information System (INIS)

    Good optical quality U3+-doped PbCl2 single crystals of the composition Pb0.99U0.01Cl2 have been obtained by the Bridgman-Stockbarger method. Luminescence spectra of the crystals were recorded in a wide spectral range at room and liquid nitrogen temperatures, and are discussed. Strong infrared emission was observed under 514 nm laser pumping to the 5f26d1 bands. The lifetimes of the emitting levels in the visible and near infrared region are given

  14. Visible whispering-gallery modes in ZnO microwires with varied cross sections

    Science.gov (United States)

    Dai, Guozhang; Zhang, Yongyou; Liu, Ruibin; Wan, Qiang; Zhang, Qinglin; Pan, Anlian; Zou, Bingsuo

    2011-08-01

    ZnO microwires with hexagonal, dodecagonal, and circular cross sections were achieved by a micro-environment control vapor deposition method. Laser induced micro-photoluminescence spectra of single wires showed separated emission modes in the visible range, and in which the higher the number of sides in cross section for the ZnO MWs, the more resonant modes are induced. Theoretical calculations indicated the nature of resonant whispering-gallery modes, in agreement with the spectral and mapping profiles of these modes. The results demonstrated that the as-prepared ZnO MWs can be used as high-quality microresonators to produce whispering-gallery modes.

  15. Visible photoluminescence of nanopowder of silicon, produced by silicon evaporation by powerful electron beam

    International Nuclear Information System (INIS)

    The silicon nanopowders, formed by the silicon massive sample evaporation by the electron beam in the argon atmosphere, are studied through the methods of the photoluminescence (PL) and combination light scattering (CS). The PL peak is identified at the room temperature in the visible spectral range of the powders, consisting of the silicon nanocrystals. The PL peak strong short-wave shift may be explained as the effect of the electrons and holes dimensional quantization in the silicon small-size (about 2 nm) nanocrystals. The silicon nanocrystals dimensions are determined through the analytical data on the CS photoluminescence and they coincided with the evaluations based on the photoluminescence data

  16. Measuring of spectral BRDF using fiber optic spectrometer

    Science.gov (United States)

    Zhang, Wei; Wang, Fugang; Wang, Zhile; Wang, Hongyuan

    2010-10-01

    We designed a new spectral bidirectional reflection distribution function (BRDF) measurement instrument, which can be utilized to measure isotropic materials simply in laboratory. The measurement instrument consists of a fiber optic spectrometer, a three-dimensional turntable, a halogen light source and a computer. The spectrometer acquires 696 samples in visible band. The angular range controlled by three-dimensional turntable is 0~330° and 0~80° for azimuth angle and zenith angle respectively. The halogen light source supplies a continuous spectrum with high efficiency and stability in the wavelength range from 360~1500 nm. The spectrometer and the three-dimensional turntable connect with the computer. The angle rotation and data acquisition are all controlled by the computer. The spectral BRDF measurement of three materials is conducted. The relation of spectral BRDF, wavelength and reflected zenith angle is presented. In conclusion, the designed spectral BRDF measurement system can acquire spectral BRDF data quickly and accurately, thus it is an efficient way to measure material spectral reflected properties which is need for computer rendering, target identification.

  17. Quantum dot light-emitting devices with electroluminescence tunable over the entire visible spectrum.

    Science.gov (United States)

    Anikeeva, Polina O; Halpert, Jonathan E; Bawendi, Moungi G; Bulovi?, Vladimir

    2009-07-01

    Improvements in quantum dot light-emitting device (QD-LED) performance are achieved by the choice of organic charge transporting layers, by use of different colloidal QDs for the different parts of the visible spectrum, and by utilizing a recently demonstrated robust QD deposition method. Spectrally narrow electroluminescence of our QD-LEDs is tuned over the entire visible wavelength range from lambda = 460 nm (blue) to lambda = 650 nm (deep red). By printing close-packed monolayers of different QD types inside an identical QD-LED structure, we demonstrate that different color QD-LEDs with QDs of different chemistry can be fabricated on the same substrate. We discuss mechanisms responsible for efficiency increase for green (4-fold) and orange (30%) QD-LEDs as compared to previous reports and outline challenges associated with achieving high-efficiency blue QD-LEDs. PMID:19514711

  18. Investigations of the March 2006 African dust storm using ground-based column-integrated high spectral resolution infrared (8-13 ?m) and visible aerosol optical thickness measurements: 2. Mineral aerosol mixture analyses

    Science.gov (United States)

    Thomas, M.; Gautier, C.

    2009-07-01

    The mineral aerosol mixture composition for the March 2006 Saharan dust storm is assessed in this paper on the basis of the analysis of visible to near-infrared (VIS-NIR) and infrared (IR) aerosol optical thickness (AOT) spectra obtained during the Portable Infrared Aerosol Transmission Experiment (PIRATE). The AOT spectra from 8 to 13 ?m were determined using column-integrated solar transmission measurements using a Fourier transform infrared spectrometer. To determine the mineralogy and mixture composition of the dust, we determined the expected mineralogy of dust from the Algerian source region in a dust storm environment. Then we computed the modeled VIS-IR AOT spectra using Mie theory for external and internal mixtures. We compared the modeled VIS-NIR AOT spectra and derived index of refraction and single-scattering albedo with the measured values from AERONET and compared the modeled IR AOT spectra with the values from our IR measurements. The fit between the measured and modeled values was best when we used an extinction resonance correction to the Mie theory results to better account for the exact wavelengths and shapes of some of the AOT peaks for mineral particles. The mineralogy and mixture composition of the best dust model includes external mixtures, internal mixtures, and mineralogy dominated by quartz, illite, and calcite. The modeled mean radius was determined, and several modes were computed in agreement with AERONET results.

  19. Air fluorescence measurements in the spectral range 300-420 nm using a 28.5 GeV electron beam

    CERN Document Server

    Abbasi, R; Belov, K; Belz, J; Cao, Z; Dalton, M; Fedorova, Y; Huentemeyer, P; Jones, B F; Jui, C C H; Loh, E C; Manago, N; Martens, K; Matthews, J N; Maestas, M; Smith, J; Sokolsky, P; Springer, R W; Thomas, J; Thomas, S; Chen, P; Field, C; Hast, C; Iverson, R; Ng, J S T; Odian, A; Reil, K; Walz, D; Bergman, D R; Thomson, G; Zech, A; Chang, F-Y; Chen, C-C; Chen, C-W; Huang, M A; Hwang, W-Y P; Lin, G-L

    2007-01-01

    Measurements are reported of the yield and spectrum of fluorescence, excited by a 28.5 GeV electron beam, in air at a range of pressures of interest to ultra-high energy cosmic ray detectors. The wavelength range was 300 - 420 nm. System calibration has been performed using Rayleigh scattering of a nitrogen laser beam. In atmospheric pressure dry air at 304 K the yield is 20.8 +/- 1.6 photons per MeV.

  20. Solid-phase synthesis as a platform for the discovery of new ruthenium complexes for efficient release of photocaged ligands with visible light.

    Science.gov (United States)

    Sharma, Rajgopal; Knoll, Jessica D; Ancona, Nicholas; Martin, Phillip D; Turro, Claudia; Kodanko, Jeremy J

    2015-02-16

    Ruthenium-based photocaging groups have important applications as biological tools and show great potential as therapeutics. A method was developed to rapidly synthesize, screen, and identify ruthenium-based caging groups that release nitriles upon irradiation with visible light. A diverse library of tetra- and pentadentate ligands was synthesized on polystyrene resin. Ruthenium complexes of the general formula [Ru(L)(MeCN)n](m+) (n = 1-3, m = 1-2) were generated from these ligands on solid phase and then cleaved from resin for photochemical analysis. Data indicate a wide range of spectral tuning and reactivity with visible light. Three complexes that showed strong absorbance in the visible range were synthesized by solution phase for comparison. Photochemical behavior of solution- and solid-phase complexes was in good agreement, confirming that the library approach is useful in identifying candidates with desired photoreactivity in short order, avoiding time-consuming chromatography and compound purification. PMID:25611351

  1. Pixel Dynamics Analysis of Photospheric Spectral Data

    Science.gov (United States)

    Rasca, Anthony P.; Chen, James; Pevtsov, Alexei A.

    2015-04-01

    Recent advances in solar observations have led to higher-resolution surface (photosphere) images that reveal bipolar magnetic features operating near the resolution limit during emerging flux events. Further improvements in resolution are expected to reveal even smaller dynamic features. Such photospheric features provide observable indications of what is happening before, during, and after flux emergence, eruptions in the corona, and other phenomena. Visible changes in photospheric active regions also play a major role in predicting eruptions that are responsible for geomagnetic plasma disturbances. A new method has been developed to extract physical information from photospheric data (e.g., SOLIS Stokes parameters) based on the statistics of pixel-by-pixel variations in spectral (absorption or emission) line quantities such as line profile Doppler shift, width, asymmetry, and flatness. Such properties are determined by the last interaction between detected photons and optically thick photospheric plasmas, and may contain extractable information on local plasma properties at sub-pixel scales. Applying the method to photospheric data with high spectral resolution, our pixel-by-pixel analysis is performed for various regions on the solar disk, ranging from quiet-Sun regions to active regions exhibiting eruptions, characterizing photospheric dynamics using spectral profiles. In particular, the method quantitatively characterizes the time profile of changes in spectral properties in photospheric features and provides improved physical constraints on observed quantities.

  2. UVISS preliminary visibility analysis

    DEFF Research Database (Denmark)

    Betto, Maurizio

    1998-01-01

    The goal of this work is to obtain a preliminary assessment of the sky visibility for anastronomical telescope located on the express pallet of the International SpaceStation (ISS)} taking into account the major constraints imposed on the instrument by the ISSattitude and structure. Part of the work is also to setup the kernel of a software tool for the visibility analysis thatshould be easily expandable to consider more complex strucures for future activities.This analysis is part of the UVISS assessment study and it is meant to provide elementsfor the definition and the selection of the instrument.The work done and the obtained results are drawn in this paper.

  3. USGS Digital Spectral Library splib06a

    Science.gov (United States)

    Clark, Roger N.; Swayze, Gregg A.; Wise, Richard A.; Livo, K. Eric; Hoefen, Todd M.; Kokaly, Raymond F.; Sutley, Stephen J.

    2007-01-01

    Introduction We have assembled a digital reflectance spectral library that covers the wavelength range from the ultraviolet to far infrared along with sample documentation. The library includes samples of minerals, rocks, soils, physically constructed as well as mathematically computed mixtures, plants, vegetation communities, microorganisms, and man-made materials. The samples and spectra collected were assembled for the purpose of using spectral features for the remote detection of these and similar materials. Analysis of spectroscopic data from laboratory, aircraft, and spacecraft instrumentation requires a knowledge base. The spectral library discussed here forms a knowledge base for the spectroscopy of minerals and related materials of importance to a variety of research programs being conducted at the U.S. Geological Survey. Much of this library grew out of the need for spectra to support imaging spectroscopy studies of the Earth and planets. Imaging spectrometers, such as the National Aeronautics and Space Administration (NASA) Airborne Visible/Infra Red Imaging Spectrometer (AVIRIS) or the NASA Cassini Visual and Infrared Mapping Spectrometer (VIMS) which is currently orbiting Saturn, have narrow bandwidths in many contiguous spectral channels that permit accurate definition of absorption features in spectra from a variety of materials. Identification of materials from such data requires a comprehensive spectral library of minerals, vegetation, man-made materials, and other subjects in the scene. Our research involves the use of the spectral library to identify the components in a spectrum of an unknown. Therefore, the quality of the library must be very good. However, the quality required in a spectral library to successfully perform an investigation depends on the scientific questions to be answered and the type of algorithms to be used. For example, to map a mineral using imaging spectroscopy and the mapping algorithm of Clark and others (1990a, 2003b), one simply needs a diagnostic absorption band. The mapping system uses continuum-removed reference spectral features fitted to features in observed spectra. Spectral features for such algorithms can be obtained from a spectrum of a sample containing large amounts of contaminants, including those that add other spectral features, as long as the shape of the diagnostic feature of interest is not modified. If, however, the data are needed for radiative transfer models to derive mineral abundances from reflectance spectra, then completely uncontaminated spectra are required. This library contains spectra that span a range of quality, with purity indicators to flag spectra for (or against) particular uses. Acquiring spectral measurements and performing sample characterizations for this library has taken about 15 person-years of effort. Software to manage the library and provide scientific analysis capability is provided (Clark, 1980, 1993). A personal computer (PC) reader for the library is also available (Livo and others, 1993). The program reads specpr binary files (Clark, 1980, 1993) and plots spectra. Another program that reads the specpr format is written in IDL (Kokaly, 2005). In our view, an ideal spectral library consists of samples covering a very wide range of materials, has large wavelength range with very high precision, and has enough sample analyses and documentation to establish the quality of the spectra. Time and available resources limit what can be achieved. Ideally, for each mineral, the sample analysis would include X-ray diffraction (XRD), electron microprobe (EM) or X-ray fluorescence (XRF), and petrographic microscopic analyses. For some minerals, such as iron oxides, additional analyses such as Mossbauer would be helpful. We have found that to make the basic spectral measurements, provide XRD, EM or XRF analyses, and microscopic analyses, document the results, and complete an entry of one spectral library sample, all takes about

  4. [Ultraviolet-visible (UV-Vis) and fluorescence spectral characteristics of dissolved organic matter (DOM) in soils of water-level fluctuation zones of the Three Gorges Reservoir Region].

    Science.gov (United States)

    Gao, Jie; Jiang Tao; Li, Lu-lu; Chen, Xue-shuang; Wei, Shi-qiang; Wang, Ding-yong; Yan, Jin- long; Zhao, Zheng

    2015-01-01

    Ultraviolet-visible (UV-Vis) absorption spectroscopy and three-dimensional fluorescence spectroscopy, combined with fluorescence regional integration were conducted to investigate the geochemical characteristics of DOM extracted from soils of water-level fluctuation zones of the Three Gorges Reservoir Region. The results showed that the average CDOM concentrations in soils were in order of Zhongxian > Fengdu > Fuling > Wanzhou > Wushan > Yunyang > Fengjie > Kaixian. Additionally, in Zhongxian, Fengdu and Fuling, the CDOM concentration [a (355)], aromaticity (SUVA254) and hydrophobicity (SUVA260) were all much higher than those at the other sampling sites, but the humification index (HIX) was lower. Four fluorophores were observed in all soil DOM samples, including three humic-like fluorescence peaks (A, C and M respectively) and one tryptophan-like fluorescence peak (T). Proportion of fluorescence regional integration of ultraviolet region humic-like A fluorophore was the highest as compared with the others. More importantly, tryptophan-like fluorophore (T) and a(355) showed significant correlation (r = 0.674, P < 0.01), indicating the variance of CDOM concentration was possibly dependent on T fluorophore. Meanwhile, the total integrated fluorescence intensity(TOT) of 3D- EEM was an appropriate parameter to characterize the total contributions of fluorophores in DOM. Furthermore, the humification degree of DOM in soils was low in comparison with higher biological availability. Conclusively it seemed that the influence of "alternation of wetting and drying" resulted from water-level fluctuation on the geochemical characteristics of soil DOM was not significant as expected. It might be related to local agricultural activity, littoral plant growth and DOM mineralization process. PMID:25898659

  5. Bi Youth Becoming Visible

    Science.gov (United States)

    Hutchins, Loraine

    2006-01-01

    If young people can not learn about same-sex desire at school, queer young people especially get the message loud and clear that their desire is illegitimate and, in such settings, it is much harder for them to feel real and visible, much less entitled to health and happiness. However the even stronger message, to all young people, is that…

  6. Strong Ionic Hydrogen Bonding Causes a Spectral Isotope Effect in Photoactive Yellow Protein

    OpenAIRE

    Kaledhonkar, Sandip; Hara, Miwa; Stalcup, T. Page; Xie, Aihua; Hoff, Wouter d

    2013-01-01

    Standard hydrogen bonds are of great importance for protein structure and function. Ionic hydrogen bonds often are significantly stronger than standard hydrogen bonds and exhibit unique properties, but their role in proteins is not well understood. We report that hydrogen/deuterium exchange causes a redshift in the visible absorbance spectrum of photoactive yellow protein (PYP). We expand the range of interpretable isotope effects by assigning this spectral isotope effect (SIE) to a functiona...

  7. Characterization of AlN metal-semiconductor-metal diodes in the spectral range of 44-360 nm: Photoemission assessments

    Science.gov (United States)

    BenMoussa, A.; Hochedez, J. F.; Dahal, R.; Li, J.; Lin, J. Y.; Jiang, H. X.; Soltani, A.; De Jaeger, J.-C.; Kroth, U.; Richter, M.

    2008-01-01

    The absolute responsivity of a metal-semiconductor-metal (MSM) photodiode based on high quality AlN material has been tested from the vacuum ultraviolet (vuv) to the near UV wavelength range (44-360nm). The metal finger Schottky contacts have been processed to 2?m in width with spacing between the contacts of 4?m. In the vuv wavelength region, the measurement methodology is described in order to distinguish the contribution of the photoemission current from the internal diode signal. In the wavelength range of interest, AlN MSM is sensitive and stable under brief vuv irradiation. The MSM shows a 200/360nm rejection ratio of more than four orders of magnitude and demonstrates the advantages of wide band gap material based detectors in terms of high rejection ratio and high output signal for vuv solar observation missions.

  8. The Electromagnetic Spectrum: Projecting Visible Spectra

    Science.gov (United States)

    In this activity, students study the range of colors in a visible light spectrum created from either a glass prism or holographic diffraction grating. This activity is in unit 2 of the "Space-Based Astronomy" guide that contains background information, worksheets, assessment activities, extensions, and alignment to national education standards.

  9. Thermal coagulation-induced changes of the optical properties of normal and adenomatous human colon tissues in vitro in the spectral range 400-1100 nm

    International Nuclear Information System (INIS)

    The absorption coefficients, the reduced scattering coefficients and the optical penetration depths for native and coagulated human normal and adenomatous colon tissues in vitro were determined over the range of 400-1100 nm using a spectrophotometer with an internal integrating sphere system, and the inverse adding-doubling method was applied to calculate the tissue optical properties from diffuse reflectance and total transmittance measurements. The experimental results showed that in the range of 400-1100 nm there were larger absorption coefficients (P < 0.01) and smaller reduced scattering coefficients (P < 0.01) for adenomatous colon tissues than for normal colon tissues, and there were smaller optical penetration depths for adenomatous colon tissues than for normal colon tissues, especially in the near-infrared wavelength. Thermal coagulation induced significant increase of the absorption coefficients and reduced scattering coefficients for the normal and adenomatous colon tissues, and significantly reduced decrease of the optical penetration depths for the normal and adenomatous colon tissues. The smaller optical penetration depth for coagulated adenomatous colon tissues is a disadvantage for laser-induced thermotherapy (LITT) and photodynamic therapy (PDT). It is necessary to adjust the application parameters of lasers to achieve optimal therapy

  10. Recoupled long-range C-H dipolar dephasing in solid-state NMR, and its use for spectral selection of fused aromatic rings

    Science.gov (United States)

    Mao, J.-D.; Schmidt-Rohr, K.

    2003-05-01

    This work introduces a simple new solid-state 13C NMR method for distinguishing various types of aromatic residues, e.g. those of lignin from fused rings of charcoal. It is based on long-range dipolar dephasing, which is achieved by recoupling of long-range C-H dipolar interactions, using two 1H 180° pulses per rotation period. This speeds up dephasing of unprotonated carbon signals approximately threefold compared to standard dipolar dephasing without recoupling and thus provides much more efficient differential dephasing. It also reduces the effects of spinning-speed dependent effective proton-proton dipolar couplings on the heteronuclear dephasing. Signals of unprotonated carbons with two or more protons at a two-bond distance dephase to lignin, slow dephasing is observed for the aromatic carbons in wood charcoal, and even slower for inorganic carbonate. Direct 13C polarization is used on these structurally complex samples to prevent loss of the signals of interest, which by design originate from carbons that are distant from protons and therefore crosspolarize poorly. In natural organic matter such as humic acids, this combination of recoupled dipolar dephasing and direct polarization at 7-kHz MAS enables selective observation of signals from fused rings that are characteristic of charcoal.

  11. Spectral imager based on Fabry-Perot interferometer for Aalto-1 nanosatellite

    Science.gov (United States)

    Mannila, Rami; Näsilä, Antti; Viherkanto, Kai; Holmlund, Christer; Näkki, Ismo; Saari, Heikki

    2013-09-01

    The Aalto-1 is a 3U-cubesat project coordinated by Aalto University. The satellite, Aalto-1, will be mainly built by students as project assignments and thesis works. The Aalto-1 is planned to launch on 2014. VTT Technical Research Centre of Finland is developing the main Earth observation payload, a miniaturized spectral imager unit, for the satellite. The spectral imager unit contains a spectral imager, a visible RGB-camera and control electronics of the cameras. Detailed design of the spectral imager unit has been completed and assembly of the spectral imager unit will be done in the autumn 2013. The spectral imager is based on a tunable Fabry-Perot interferometer (FPI) accompanied by an RGB CMOS image sensor. The FPI consists of two highly reflective surfaces separated by a tunable air gap and it is based on a piezo-actuated structure. The piezo-actuated FPI uses three piezo-actuators and is controlled in a closed capacitive feedback loop. The spectral resolution of the imager will be 8-15 nm at full width at half maximum and it will operate in the wavelength range 500-900 nm. Imaging resolution of the spectral imager is 1024x1024 pixels and the focal length of the optics is 32 mm and F-number is 3.4. Mass of the spectral imager unit is approximately 600 grams, and dimensions are 97 mm x 97 mm x 48 mm.

  12. Robust Epsilon Visibility

    OpenAIRE

    Duguet, Florent; Drettakis, George

    2002-01-01

    Analytic visibility algorithms, for example methods which compute a subdivided mesh to represent shadows, are notoriously unrobust and hard to use in practice. We present a new method based on a generalized definition of extremal stabbing lines, which are the extremities of shadow boundaries. We treat scenes containing multiple edges or vertices in degenerate configurations, (e.g., collinear or coplanar). We introduce a robust ? method to determine whether each generalized extremal stabbing ...

  13. Evacuation under limited visibility

    Science.gov (United States)

    Frank, Guillermo A.; Dorso, Claudio O.

    2015-06-01

    A multiplicity of situations can trigger off an evacuation of a room under panic conditions. For "normal" (with "normal" meaning absence of obstacles, perfect visibility, etc.) environmental conditions, the "faster is slower" effect dominates the dynamics of this process. It states that as the pedestrians desire to reach the exit increases, the clogging phenomena delays the time to get out of the room. But, environmental conditions are usually far from "normal." In this work, we consider that pedestrians have to find their way out under low visibility conditions. Some of them might switch to a herding-like behavior if they do not remember where the exit was. Others will just trust on their memory. Our investigation handles the herding and memory effects on the evacuation of a single exit room with no obstacles. We also include a section on how signaling devices affect the evacuation process. Unexpectedly, some low visibility situations may enhance the evacuation performance. This can be resumed as a second paradoxical result, since we demonstrated in an earlier investigation that "clever is not always better" G. A. Frank and C. O. Dorso, Physica A 390, 2135 (2011).

  14. Quantitative analysis and classification of tongue inspection based on the visible reflection spectrum

    Directory of Open Access Journals (Sweden)

    Meng Kong

    2011-01-01

    Full Text Available Objective: In this study, optical data on color of tongue tips were collected by using a visible reflection spectrum system. Quantitative method of tongue inspection and classification of tongue states including pale, pale red, red and crimson manifestations were investigated. Methods: Chromaticity coordinates of the tongue tips from 98 subjects were calculated on the basis of the visible reflection spectrum. The tongue color was quantified and classified by the visible reflection spectrum in the range from 590 nm to 780 nm, based on the higher red-band energy distribution on the tongue tip color. Results: It was found that comparison and analysis of tongue tip color from different samples would be well-suited after spectrum vector normalization, and the difference of tongue tip color between different samples could be observed easily when the tongue tip optical data were sited in CIE 1931 chromaticity diagram. The tongue tip colors were analyzed quantitatively and classified by the spectral energy intensity at the wavelength of 670 nm and (or spectral energy ratio of red bank from 590 nm to 780 nm. The results of classification showed that there was sound corresponding accuracy with the clinical diagnosis of pale tongue, pale red tongue, red tongue and crimson tongue.Conclusion: In this study, based on the collection of the information data on tongue tip characteristics with the visible spectrum from 380 nm to 780 nm, the quantitative analysis of tongue inspection for pale tongue, pale red tongue, red tongue and crimson tongue was established. The quantitative value for tongue tip color is an effective method for classification of the condition of the tongue tip, which provides a useful tool for the modernization of tongue inspection in traditional Chinese medicine.

  15. Spectral curves of surface reflectance in some Antarctic regions

    Energy Technology Data Exchange (ETDEWEB)

    Lupi, A.; Tomasi, C.; Orsini, A.; Cacciari, A.; Vitale, V.; Georgiadis, T. [Consiglio Nazionale delle Ricerche, Institute of Atmospheric and Oceanic Sciences, Bologna (Italy); Casacchia, R.; Salvatori, R. [Consiglio Nazionale delle Ricerche, Institute for Atmospheric Pollution, Monterotondo Scalo, Rome (Italy); Salvi, S. [National Institute of Geophysics, Remote Sensing Laboratory, Rome (Italy)

    2001-04-01

    Four surface reflectance models of solar radiation were determined by examining several sets of field measurements taken for clear-sky conditions at various sites in Antarctica. Each model consists of the mean spectral curve of surface reflectance in the 0.25-2.7 {mu}m wavelength range and of the dependence curve of total abedo on the solar elevation angle h, within the range from 5{sup 0} to 55{sup 0}. The TNB (Terra Nova Bay) model refers to a rocky terrain where granites are predominant; the NIS (Nansen Ice Sheet) model to a glacier surface made uneven by sastrugi and streaked by irregular fractures; the HAP (High Altitude Plateau) model to a flat ice surface covered by fresh snow and scored by light sastrugi; and the RIS (Ross Ice Shelf) model to an area covered by the sea ice pack presenting many discontinuities in the reflectance features, due to melt water lakes, puddles, refrozen ice and snow pots. The reflectance curve obtained for the TNB model presents gradually increasing values as wavelength increases through the visible spectral range and almost constant values at infrared wavelengths, giving a total albedo value equal to 0.264 at = 30{sup 0}, which increases by about 80% through the lower range of h and decreases by 12% through the upper range. The reflectance curves of the NIS, HAP and RIS models are all peaked at visible wavelengths and exhibit decreasing values throughout the infrared spectral range, giving values of total albedo equal to 0.464, 0.738 and 0.426 at h 30{sup 0}, respectively. These values were estimated to increase by 8-14% as h decreases from 30{sup 0} to 5{sup 0} and to decrease by 2-4% only as h increases from 30{sup 0} to 55{sup 0}.

  16. Photon path depth in tissue phantoms: a comparison of visible and near-infrared (NIR) wavelengths

    Science.gov (United States)

    Asplund, Karin M.; Schenkman, Kenneth A.; Ciesielski, Wayne A.; Arakaki, Lorilee S. L.

    2014-03-01

    Optical spectroscopy is being used increasingly in medical applications to noninvasively investigate tissues below the skin. In order to assure adequate sampling of tissues underlying the skin, photon penetration depth must be known. Photon penetration in tissues has been studied with near-infrared (NIR) light, but experimental study of visible light propagation in tissue has been limited. In this study, a micro-motion system coupled with a reflectance spectroscopy system was used to determine the penetration depth of visible-range and NIR photons (535-800 nm) in phantoms composed of Intralipid and hemoglobin. An absorbing target was placed at intervals of 0.1mm along a 15mm line perpendicular to and bisecting the line between the ends of the source and detector optical fiber bundles. Comparisons between detected light intensities at different target positions were used to determine the most probable photon path depths at 576 nm and at 760 nm. Scattering coefficients, hemoglobin concentrations, and source-detector separations were varied to evaluate their effects on the penetration depth of photons. Results from phantoms containing Intralipid only showed that the most-probable penetration depth at 576 nm was comparable to that at 760 nm. Larger sourcedetector separations resulted in deeper photon penetration depths for both spectral regions. Changes in scattering over a 4-fold range did not affect the photon path depth appreciably. In the presence of hemoglobin with a source-detector separation of 13 mm, the most probable depth of photon penetration in the visible range was greater than 2.5 mm, and was within 1 mm of the most probable depth of photon penetration in the NIR. This study demonstrates the feasibility of using the visible and NIR regions in transcutaneous reflectance spectroscopy.

  17. Some new possibilities in direct visible and x ray measurements

    International Nuclear Information System (INIS)

    Subnanosecond photodetection measurements in visible and X ray range with vacuum cell and very thin microchannel plate phototube (coupled with a fast scintillator or not) in conjunction with fast oscilloscope (5 GHz) are presented. They are compared to those given by a visible or a gold photocathode X-ray streak camera (temporal resolution better than 20 ps). (author)

  18. Thioxanthone based 9-[2-(methyl-phenyl-amino)-acetyl]-thia-naphthacene-12-one as a visible photoinitiator

    International Nuclear Information System (INIS)

    Photoinitiators that operate in the visible range of the electromagnetic spectrum have widespread applications. Thioxanthone based 9-[2-(methyl-phenyl-amino)-acetyl]-thia-naphthacene-12-one (TX-MPA) was synthesized and the characterization of this initiator was confirmed by spectral analysis methods. TX-MPA has excellent absorption properties in the visible range (?480nm=3576 L/mol.cm). Photophysical studies; fluorescence quantum yield (?f=0.22, DPA), phosphorescence lifetime (?p=115 ms) and triplet lifetime (?=190 ns) were explored. To explore the initiation mechanism of TX-MPA, besides the photophysical and photochemical studies, the polymer (PMMA) obtained from the photopolymerization studies was subjected to a phosphorescence study and ?p was found to be 105 ms compared to 115 ms for the initiator TX-MPA which proved attachment of the initiator to the polymer. Possibly both intermolecular and intramolecular hydrogen abstraction, occur during the initiation stage depending on the concentration of the initiator. Highlights: ? Synthesis and photophysical properties of a visible photoinitiator (TX-MPA) are proposed. ? TX-MPA has high molar absorption values in the visible region. ? TX-MPA can initiate photopolymerization of methylmethacrylate monomer under UV and sunlight. ? Inter or intramolecular hydrogen abstraction mechanisms occur depending on initiator concentration

  19. Spectroscopy of 14NH3 and 15NH3 in the 2.3 ?m spectral range with a new VECSEL laser source

    International Nuclear Information System (INIS)

    A spectroscopic study of ammonia molecule in the 2.3 ?m water atmospheric window is presented. Compared to previous experimental works a narrow, broadly tunable, continuous laser source was applied in order to obtain high resolution spectra in this range. It was the first application of the newly developed Vertical External Cavity Surface Emitting Laser (VECSEL). The analysis of the absorption spectra of two different isotopologue admixtures allowed to identify 336 14NH3 and 244 15NH3 lines in the studied region from 4275 to 4340 cm?1. These data were compared to previous line list based on experimental data – the HITRAN database and the work of Urban et al., as well as to the theoretical predictions by Yurchenko et al. and Huang et al. Together for 235 14NH3 and 183 15NH3 lines a complete assignment was proposed. From those 63 14NH3 and 114 15NH3 transitions were newly assigned. The complete peaklist of transitions containing ro-vibrational state identifications is presented in Supplementary materials. - Highlights: • A spectroscopic study of the 14NH3 and 15NH3 in the 2.3 ?m region was performed. • The newly developed Vertical External Cavity Surface Laser (VECSEL) was applied. • The transitions line positions and relative intensities have been measured. • 235 from 336 observed 14NH3 lines were assigned (63 for the first time). • 183 from 244 observed 15NH3 lines were assigned (114 for the first time)

  20. Non-Euclidean visibility problems

    CERN Document Server

    Chamizo, F

    2006-01-01

    We consider the analog of visibility problems in hyperbolic plane (represented by Poincar\\'{e} half-plane model H), replacing the standard lattice $Z\\times Z$ by the orbit $z=i$ under the full modular group $z$. We prove a visibility criterion and study orchard problem and the cardinality of visible points in large circles

  1. Linearisation of RGB camera responses for quantitative image analysis of visible and UV photography: a comparison of two techniques.

    Science.gov (United States)

    Garcia, Jair E; Dyer, Adrian G; Greentree, Andrew D; Spring, Gale; Wilksch, Philip A

    2013-01-01

    Linear camera responses are required for recovering the total amount of incident irradiance, quantitative image analysis, spectral reconstruction from camera responses and characterisation of spectral sensitivity curves. Two commercially-available digital cameras equipped with Bayer filter arrays and sensitive to visible and near-UV radiation were characterised using biexponential and Bézier curves. Both methods successfully fitted the entire characteristic curve of the tested devices, allowing for an accurate recovery of linear camera responses, particularly those corresponding to the middle of the exposure range. Nevertheless the two methods differ in the nature of the required input parameters and the uncertainty associated with the recovered linear camera responses obtained at the extreme ends of the exposure range. Here we demonstrate the use of both methods for retrieving information about scene irradiance, describing and quantifying the uncertainty involved in the estimation of linear camera responses. PMID:24260244

  2. Visible Spectrum Incandescent Selective Emitter

    Energy Technology Data Exchange (ETDEWEB)

    Sonsight Inc.

    2004-04-30

    The purpose of the work performed was to demonstrate the feasibility of a novel bi-layer selective emitter. Selective emitters are incandescent radiant bodies with emissivities that are substantially larger in a selected part of the radiation spectrum, thereby significantly shifting their radiated spectral distribution from that of a blackbody radiating at the same temperature. The major research objectives involved answering the following questions: (1) What maximum VIS/NIR radiant power and emissivity ratios can be attained at 2650 K? (2) What is the observed emitter body life and how does its performance vary with time? (3) What are the design tradeoffs for a dual heating approach in which both an internally mounted heating coil and electrical resistance self-heating are used? (4) What are the quantitative improvements to be had from utilizing a bi-layer emitter body with a low emissivity inner layer and a partially transmissive outer layer? Two approaches to obtaining selective emissivity were investigated. The first was to utilize large optical scattering within an emitter material with a spectral optical absorption that is much greater within the visible spectrum than that within the NIR. With this approach, an optically thick emitter can radiate almost as if optically thin because essentially, scattering limits the distance below the surface from which significant amounts of internally generated radiation can emerge. The performance of thin emitters was also investigated (for optically thin emitters, spectral emissivity is proportional to spectral absorptivity). These emitters were fabricated from thin mono-layer emitter rods as well as from bi-layer rods with a thin emitter layer mounted on a substrate core. With an initially estimated energy efficiency of almost three times that of standard incandescent bulbs, a number of energy, economic and environmental benefits such as less energy use and cost, reduced CO{sub 2} emissions, and no mercury contamination was initially projected. The work performed provided answers to a number of important questions. The first is that, with the investigated approaches, the maximum sustained emitter efficiencies are about 1.5 times that of a standard incandescent bulb. This was seen to be the case for both thick and thin emitters, and for both mono-layer and bi-layer designs. While observed VIS/NIR ratios represent improvements over standard incandescent bulbs, it does not appear sufficient to overcome higher cost (i.e. up to five times that of the standard bulb) and ensure commercial success. Another result is that high temperatures (i.e. 2650 K) are routinely attainable without platinum electrodes. This is significant for reducing material costs. A novel dual heating arrangement and insulated electrodes were used to attain these temperatures. Another observed characteristic of the emitter was significant grain growth soon after attaining operating temperatures. This is an undesirable characteristic that results in substantially less optical scattering and spectral selectivity, and which significantly limits emitter efficiencies to the values reported. Further work is required to address this problem.

  3. Liquid-Crystal Coats Help Make Flows Visible

    Science.gov (United States)

    Holmes, Bruce J.; Obara, Clifford J.

    1991-01-01

    Visible indication of transition of boundary layer from laminar to turbulent flow plays important role in aerodynamic tests in wind tunnels and in flight. In newly developed method, liquid-crystal coats used to make visible such features of boundary-layer flows as transitions, separations, and locations of shocks. Changes of color rapid and reversible. For flight applications, provides capability for making transitions visible throughout almost entire altitude and speed ranges of subsonic aircraft. Also applicable to visible indication of supersonic flows and suitable for general use in high- and low-speed wind-tunnel and water-tunnel testing.

  4. Comportamento espectral de folhas de Eucalyptus globulus (Labill.) atacadas por Mycosphaerella spp. nas regiões do visível e do infravermelho próximo do espectro eletromagnético / Spectral behavior of Eucalyptus globulus (Labill.) leaves attacked by Mycosphaerella spp. in regions of visible and infrared near the electromagnetic spectrum

    Scientific Electronic Library Online (English)

    Diogo Belmonte, Lippert; Ana Caroline Paim, Benedetti; Marlove Fatima Brião, Muniz; Rudiney Soares, Pereira; Carlos Alberto, Biernaski Junior; Elder, Finkenauer; Elias Fernando, Berra.

    2015-03-01

    Full Text Available O trabalho tem como objetivo analisar o comportamento espectral de folhas de Eucalyptus globulus atacadas em quatro diferentes níveis de severidade pelo fungo Mycosphaerella spp. em diferentes posições na copa da árvore, nas quatro estações climáticas, considerando duas regiões do espectro eletromag [...] nético: visível e infravermelho próximo. Foram realizadas coletas de material vegetativo em todas as estações climáticas, em diferentes posições na árvore (base, meio e extrato superior da copa). Em laboratório, as folhas foram classificadas em quatro níveis de severidade (sadio, pouco, medianamente e muito atacado) e posteriormente efetuadas as medidas de reflectância espectral com auxílio de um espectrorradiômetro. O comportamento espectral das folhas de Eucalyptus globulus é característico de acordo com o nível de severidade da doença, diferindo dos demais principalmente em altos níveis de infecção por Mycosphaerella spp. e diferenciam-se principalmente de folhas sadias e de folhas pouco atacadas, em ambas as regiões do espectro eletromagnético, esse comportamento ocorre para as diferentes posições da copa e estações climáticas variando a quantidade de energia refletida. Conclui-se que a reflectância das folhas de Eucalyptus globulus atacadas por Mycosphaerella spp. difere de acordo com a posição na copa da árvore e a estação climática em que foram coletadas e níveis avançados da severidade da doença. Abstract in english The study aims to analyze the spectral behavior of leaves of Eucalyptus globulus attacked in four different severity levels by Mycosphaerella spp. in different positions in the canopy of the tree in the four seasons, considering two regions of the electromagnetic spectrum: visible and near infrared. [...] The plant material was collected in all seasons, in different positions in the tree (base, middle and top of the canopy extract). In the laboratory, leaves were classified into four levels of severity (healthy, little, medium and heavy fire) and then made ??measurements of spectral reflectance measured with a spectroradiometer. The spectral behavior of Eucalyptus globules leaves is characteristic according to the severity degree of the disease, differing primarily in the other high levels of infection by Mycosphaerella spp. and differ mainly of healthy leaves and leaves which are little attacked, in both regions of the electromagnetic spectrum, this behavior occurs for different treetop positions and climate seasons, varying the amount of reflected energy. It is concluded that the reflectance of the Eucalyptus globules leaves attacked by Mycosphaerella spp. differs according to the position in the tree crown and the weather station when they were collected and to the advanced levels of disease severity.

  5. Miniaturized spectral imager for Aalto-1 nanosatellite

    Science.gov (United States)

    Mannila, Rami; Näsilä, Antti; Praks, Jaan; Saari, Heikki; Antila, Jarkko

    2011-11-01

    The Aalto-1 is a 3U-cubesat project coordinated by Aalto University. The satellite, Aalto-1, will be mainly built by students as project assignments and thesis works. VTT Technical Research Centre of Finland will develop the main Earth observation payload, a miniaturized spectral imager, for the satellite. It is a novel highly miniaturized tunable filter type spectral imager. Mass of the spectral imager will be less than 400 grams, and dimensions will be approximately 80 mm x 80 mm x 45 mm. The spectral imager is based on a tunable Fabry-Pérot interferometer (FPI) accompanied by an RGB CMOS image sensor. The FPI consists of two highly reflective surfaces separated by a tunable air gap and it is based either on a microelectromechanical (MEMS) or piezo-actuated structure. The MEMS FPI is a monolithic device, i.e. it is made entirely on one substrate in a batch process, without assembling separate pieces together. The gap is adjusted by moving the upper mirror with electrostatic force. Benefits of the MEMS FPI are low mass and small size. However, large aperture (2-10 mm) MEMS FPIs are currently under development, thus it is not yet known if their performance is adequate. The piezo-actuated FPI uses three piezo-actuators and is controlled in a closed capacitive feedback loop. The drawback of the piezo-actuated FPI is its higher mass. However, it has a large aperture which enables a shorter exposure times. Selection of the FPI type will be done after thorough evaluation. Depending on the selected FPI type, the spectral resolution of the imager will be 5 - 10 nm at full width at half maximum and it will operate in the visible and/or near infrared range.

  6. Spectral characterisation and discrimination of burnt areas

    OpenAIRE

    Pereira, Jose?; Sa?, Ana; Sousa, Ade?lia; Santos, Teresa; Carreiras, Joa?o

    1999-01-01

    Spectral properties of recent burns charaterised, in the visible, near infrared, mid-infrared, thermal infrared, and microwave spectral domains. Fire-induced reflectance changes are also compared for varios ecosystems and biomes, and discussed in terms of the cological effects of phytomass combustion. The spectral signaturess of combustion products and of burnt areas are compared with those of various plant material and land cover types, in order to graphically represent relevant aspects of b...

  7. Visible Earth: Coastal Processes

    Science.gov (United States)

    Kevin Ward

    This web page is part of Visible Earth, the National Atmospheric and Space Agency (NASA) web site, a searchable directory of images, visualizations, and animations of the Earth. Subtopics of Oceans: Coastal Processes are: Barrier Islands, Coral Reefs, Deltas, Estuaries, Fjords, Lagoons, Sea Level Rise, Sea Surface Height, Sediment Transport, Sedimentation, and Shoreline Displacement. At the time of cataloging, most items were images. For the Advanced search, users may search by Sensor (usually a satellite), Location, Other terms, or by Dates; they may also set retrieval for animations only. This database solicits additional material from users.

  8. Visibility of comet nuclei

    International Nuclear Information System (INIS)

    Photography of the nucleus of comet Halley is the goal of several planned space missions. The nucleus of a comet is surrounded by a cloud of dust particles. If this cloud is optically thick, it will prevent observation of the nuclear surface. Broadband photometry of nine comets has been analyzed to determine the visibility of their nuclei. Only in the case of comet West near perihelion was the dust dense enough to interfere with imaging. Comparison of the visual brightness of the well-observed comets with that of Halley in 1910 leads to the conclusion that the nucleus of Halley can be imaged without significant obscuration by the dust

  9. Atmospheric Visibility Monitoring Using Digital Image Analysis Techniques

    Science.gov (United States)

    Liaw, Jiun-Jian; Lian, Ssu-Bin; Huang, Yung-Fa; Chen, Rung-Ching

    Atmospheric visibility is a standard of human visual perception of the environment. It is also directly associated with air quality, polluted species and climate. The influence of urban atmospheric visibility affects not only human health but also traffic safety and human life quality. Visibility is traditionally defined as the maximum distance at which a selected target can be recognized. To replace the traditional measurement for atmospheric visibility, digital image processing schemes provide good visibility data, established by numerical index. The performance of these techniques is defined by the correlation between the observed visual range and the obtained index. Since performance is affected by non-uniform illumination, this paper proposes a new procedure to estimate the visibility index with a sharpening method. The experimental results show that the proposed procedure obtains a better correlation coefficient than previous schemes.

  10. [Complex refractive index measurement of fly ash particles using suspension spectral transmission method].

    Science.gov (United States)

    Xing, Jian; Sun, Xiao-Gang; Zhou, Chen; Yuan, Gui-Bin; Zhang, Zhi-Lin

    2010-12-01

    Spectral complex refractive index of fly ash particles is an important parameter in the processing of scattering properties calculation. On the basis of theory about inversion of complex refraction index using transimission method, a novel method was proposed, in which fly ash particles were dispersed in the water to compose turbid liquid, and spectral transmissivity of turbid liquid was measured using visible spectrophotometer. Particles size distribution was measured using laser particles sizing. So complex refraction index of fly ash particles was inverted simply. The result indicated that no signifcant absorption appeared in the visible wavelength range for fly ash particles, but transmittance decreased with wavelength increasing. The inversion results from the proposed method agreed with KBr sampling method. The proposed method is simpler, and has fewer constraints, meanwhile the inverion wavelength will be expanded if using infrared spectrophotometer. PMID:21322243

  11. Crescent Visibility in Indonesia

    Science.gov (United States)

    Djamaluddin, T.

    2000-10-01

    Research on crescent visibility in Indonesia has not been conducted yet systematically based on astronomical analysis to obtain the criteria of possibility of crescent sighting. While, the criteria are needed in determining the beginning of Islamic calendar, especially for Ramadhan, Shawal, and Zulhijjah. This analysis is conducted to overcome such a problem, by using documentation of crescent sighting during 1962-1997 in Indonesia. The results can be concluded as follows: Crescent sighting with low altitude tends to be reported from less then 3 location, likely due to misjudging of foreground object (e.g. lamp) considered as crescent. Misjudging of the crescent due to misidentification. of planet Venus or Mercury is proved for low altitude crescent sighting. After eliminating foreground and background objects, it is obtained the criteria of crescent visibility in Indonesia: (1). Moon age should be greater than 8 hours. (2). Moon-Sun angle should be greater than 5,6 deg. (3). Moon-Sun altitude difference should be greater than 3 deg (crescent's altitude greater than 2 deg) for Moon-Sun azimuth difference of approx. 6 deg, while for Moon-Sun azimuth difference less than 6 deg, it is needed more altitude difference. For Moon-Sun azimuth difference of about 0 deg, the altitude difference should be greater than 9 deg.

  12. In-flight intercalibration of FY-3C visible channels with AQUA MODIS

    Science.gov (United States)

    Xu, Na; Chen, Lin; Wu, Ronghua; Hu, Xiuqing; Sun, Ling; Zhang, Peng

    2014-11-01

    Intercalibration against a well-calibrated instrument at Low Earth Orbit (LEO) is a common method which has been widely used to assess the in-flight calibration of a new instrument. Different instruments on LEO spacecraft with similar spectral channels can be compared with each other using their simultaneous nadir observations (SNO). The postlaunch calibrations of Medium Resolution Spectral Imager (MERSI) and the Visible Infrared Radiometer (VIRR) in visible channels which are two major multi-spectral imaging radiometers onboard FY-3C are addressed based on SNO intercalibration method. Collection 6 reflectance products of AQUA MODIS are used as reference. The spectral difference impacts of matching channels are simulated and adjusted using GOME-2 hyperspectral measurements. As monitoring the stability of monthly forcing fits, it is found the linear fitting slopes of MERSI VIS channel 1~12 are scene reflectance dependence with relative differences greater than 20%, while the monthly forcing fits of VIRR show well agreement in VIS channels. This is proved to attribute to the nonlinear response of MERSI as the monthly measurements cover different dynamic ranges. A new radiometric calibration equation considering nonlinear correction is proposed based on an on orbit linear adjustment to prelaunch quadratic calibration. The new calibrations are more consistent with SNO samples, and greatly improve the performance over high reflective scene comparing with linear results verified by statistical measurements over Deep Convective Clouds targets. It is demonstrated that other reference is necessary in ocean color channels as MODIS reflectance is within 10% where the nonlinear feature is likely much serious. It is an invaluable lesson that the temporal variation of calibration slope not always indicates the detector's degradation, but maybe is the valuable information that helps to expose undiscovered characters of instrument.

  13. Spectral plasma diagnostics in welding with CO2 lasers

    International Nuclear Information System (INIS)

    The spectral emission of the laser induced plasma is investigated during the welding process of steel. In this study, emission spectroscopy in the visible spectral range is used. A method is presented for determining the electron temperature, the electron density as well as the density of the neutral atoms in the welding plasma. In these metallic studies the relative line intensity technique was used, in which the radiation from a pair of spectral lines is compared as a function of electron temperature. The technique eliminates the need for a calibration source and can be used easily in the plasma monitoring applications. Some examples of the estimations of the plasma temperature, the electron and the neutral atom density are demonstrated. Time and space resolved measurements of the keyhole emission are presented. The application of the spectral diagnostic during the keyhole formation at the beginning of the metal sheet as well as at the end of the welding process at the end of the sheet is shown. The results help to explain the plasma absorption inside the keyhole. Some aspects of the spectral diagnostic as a basic method for a welding control are discussed

  14. Electrically tunable selective reflection of light from ultraviolet to visible and infrared by heliconical cholesterics

    CERN Document Server

    Xiang, Jie; Li, Quan; Paterson, Daniel A; Storey, John M D; Imrie, Corrie T; Lavrentovich, Oleg D

    2015-01-01

    Cholesteric liquid crystals with helicoidal molecular architecture are known for their ability to selectively reflect light with the wavelength that is determined by the periodicity of molecular orientations. Here we demonstrate that by using a cholesteric with oblique helicoidal(heliconical) structure, as opposed to the classic right-angle helicoid, one can vary the wavelength of selectively reflected light in a broad spectral range, from ultraviolet to visible and infrared (360-1520 nm for the same chemical composition) by simply adjusting the electric field applied parallel to the helicoidal axis. The effect exists in a wide temperature range (including the room temperatures) and thus can enable many applications that require dynamically controlled transmission and reflection of electromagnetic waves, from energy-saving smart windows to tunable organic lasers, reflective color display, and transparent see-through displays.

  15. On spectropolarimetric measurements with visible lines

    CERN Document Server

    Iniesta, J C del Toro; Rubio, L R Bellot

    2010-01-01

    The ability of new instruments for providing accurate inferences of vector magnetic fields and line-of-sight velocities of the solar plasma depends a great deal on the sensitivity to these physical quantities of the spectral lines chosen to be measured. Recently, doubts have been raised about visible Stokes profiles to provide a clear distinction between weak fields and strong ones filling a small fraction of the observed area. The goal of this paper is to give qualitative and quantitative arguments that help in settling the debate since several instruments that employ visible lines are either operating or planned for the near future. The sensitivity of the Stokes profiles is calculated through the response functions (e.g. Ruiz Cobo & Del Toro Iniesta, 1994). Both theoretical and empirical evidences are gathered in favor of the reliability of visible Stokes profiles. The response functions are used as well for estimating the uncertainties in the physical quantities due to noise in the observations. A usef...

  16. UVMag: stellar formation, evolution, structure and environment with space UV and visible spectropolarimetry

    CERN Document Server

    Neiner, C; Fullerton, A; Gry, C; Hussain, G; Lebre, A; Morin, J; Petit, P; Sundqvist, J O; ud-Doula, A; Vidotto, A A; Wade, G A

    2014-01-01

    Important insights into the formation, structure, evolution and environment of all types of stars can be obtained through the measurement of their winds and possible magnetospheres. However, this has hardly been done up to now mainly because of the lack of UV instrumentation available for long periods of time. To reach this aim, we have designed UVMag, an M-size space mission equipped with a high-resolution spectropolarimeter working in the UV and visible spectral range. The UV domain is crucial in stellar physics as it is very rich in atomic and molecular lines and contains most of the flux of hot stars. Moreover, covering the UV and visible spectral domains at the same time will allow us to study the star and its environment simultaneously. Adding polarimetric power to the spectrograph will multiply tenfold the capabilities of extracting information on stellar magnetospheres, winds, disks, and magnetic fields. Examples of science objectives that can be reached with UVMag are presented for pre-main sequence,...

  17. Effects of Dopant Concentrations on Thin Films with Coherent Formulation at Visible Wavelengths

    Directory of Open Access Journals (Sweden)

    M. Omidpanah

    2012-01-01

    Full Text Available Semiconductor materials with coatings have a wide range of applications in MEMS and NEMS. This work uses transfer-matrix method for calculating the radiative properties. Dopped silicon is used and the coherent formulation is applied. The Drude model for the optical constants of doped silicon is employed. Results showed that for the visible wavelengths, more emittance occurs in high concentrations and the reflectance decreases as the concentration increases. In these wavelengths, transmittance is negligible. Donars and acceptors act similar in visible wavelengths. The effect of wave interference can be understood by plotting the spectral properties such as reflectance or transmittance of a thin dielectric film versus the film thickness and analyzing the oscillations of properties due to constructive and destructive interferences. But this effect has not been shown at visible wavelengths. At room temperature, the scattering process is dominated by lattice scattering for lightly doped silicon, and the impurity scattering becomes important for heavily doped silicon when the dopant concentration exceeds 1018cm-3.

  18. Inactivation of viruses by coherent excitations with a low power visible femtosecond laser

    Directory of Open Access Journals (Sweden)

    Wu T-C

    2007-06-01

    Full Text Available Abstract Background Resonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. Results and discussion By using a very low power (as low as 0.5 nj/pulse visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser. Conclusion Our experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system.

  19. Improved low visibility forecasts at Amsterdam Airport

    Science.gov (United States)

    Wijngaard, J.; Vogelezang, D.; Maat, N.; van Bruggen, H.

    2009-09-01

    Accurate, reliable and unambiguous information concerning the actual and expected (low) visibility conditions at Amsterdam Airport Schiphol is very important for the available operational flow capacity. Therefore visibility forecast errors can have a negative impact on safety and operational expenses. KNMI has performed an update of the visibility forecast system in close collaboration with the main users of the forecasts (Air Traffic Control, the airport authorities and KLM airlines). This automatic forecasting system consists of a Numerical Weather Prediction Model (Hirlam) with a statistical post processing module on top of it. Output of both components is supplied to a human forecaster who issues a special probabilistic forecast bulletin. This bulletin is tailored to the specific requirements of the airport community. The improvements made to the forecast system are twofold: 1) In addition to the Meteorological Optical Range (MOR) values, RVR (Runway Visual Range) is forecasted. Since RVR depends on both MOR and the local Background Luminance, a (deterministic) statistical forecast for the latter has been developed. 2) Another improvement was achieved by calculating joint probabilities for specific combinations of visibility and cloud base height for thresholds which have direct impact on the flow capacity at the airport. The development of this new visibility forecast will be presented briefly. Also a few verification results will be shown to demonstrate the improvements made. Finally, the importance of explaining the user the use of the forecast information, in relation to their decision making process, will be discussed. For that reason, a simple guideline model to make a cost-optimal choice will be introduced.

  20. ON SPECTROPOLARIMETRIC MEASUREMENTS WITH VISIBLE LINES

    International Nuclear Information System (INIS)

    The ability of new instruments for providing accurate inferences of vector magnetic fields and line-of-sight velocities of the solar plasma depends a great deal on the sensitivity to these physical quantities of the spectral lines chosen to be measured. Recently, doubts have been raised about visible Stokes profiles to provide a clear distinction between weak fields and strong ones filling a small fraction of the observed area. The goal of this paper is to give qualitative and quantitative arguments that help in settling the debate since several instruments that employ visible lines are either operating or planned for the near future. The sensitivity of the Stokes profiles is calculated through the response functions (RFs), for e.g., by Ruiz Cobo and Del Toro Iniesta. Both theoretical and empirical evidences are gathered in favor of the reliability of visible Stokes profiles. The RFs are also used for estimating the uncertainties in the physical quantities due to noise in observations. A useful formula has been derived that takes into account the measurement technique (number of polarization measurements, polarimetric efficiencies, and number of wavelength samples), the model assumptions (number of free parameters and the filling factor), and the radiative transfer (RFs). We conclude that a scenario with a weak magnetic field can reasonably be distinguished with visible lines from another with a strong field but a similar Stokes V amplitude, provided that the Milne-Edes V amplitude, provided that the Milne-Eddington approximation is good enough to describe the solar atmosphere and the polarization signal is at least 3 or 4 times larger than the typical rms noise of 10-3 Ic reached in the observations.

  1. Efficient generation of 3.9 W of diffraction-limited green light with spectrally combined tapered diode lasers

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin

    We propose an efficient concept increasing the power of diode laser systems in the visible spectral range. In comparison with second harmonic generation of single emitters, spectral beam combining with subsequent sum-frequency generation enhances the available power significantly. Combining two 1060 nm tapered diode lasers, we achieve a 2.5-3.2 fold increase of green light with a maximum power of 3.9 Watts in a diffraction-limited beam. At this level, diode lasers have a high application potential, for example, within the biomedical field. In order to enhance the power even further, our concept can be expanded combining multiple diode lasers.

  2. Tunable synchronously-pumped fiber Raman laser in the visible and near-infrared exploiting MOPA-generated rectangular pump pulses.

    Science.gov (United States)

    Lin, Dejiao; Alam, Shaif-ul; Teh, Peh Siong; Chen, Kang Kang; Richardson, David J

    2011-06-01

    We report a tunable synchronously pumped fiber Raman laser (SPFRL) in the near-infrared (NIR) and visible wavebands pumped by a pulsed, all-fiber PM 1060 nm master oscillator power amplifier (MOPA) and its frequency-doubled output, respectively. The seed was adaptively shaped to deliver rectangular output pulses, thereby enabling selective excitation of individual Raman Stokes lines. Using filtered synchronous feedback of the desired Raman Stokes line, the linewidth of the SPFRL was reduced by a factor of 4 and the extinction ratio of the desired Raman Stokes was improved by more than 3 dB relative to a simple single-pass conversion scheme. A continuous tuning range of 2.2 THz was obtained for each of the Raman Stokes orders in the visible (spanning from green to orange-first to fifth Stokes lines). A larger 5.0 THz tunable range was achieved in the NIR spectral region. PMID:21633445

  3. Ultrahigh Resolution Spectroscopy Across the Visible to Infrared Spectrum Using Multi-Mode Interference in a Compact Tapered Fiber

    CERN Document Server

    Wan, Noel H; Shiue, Ren-Jye; Chen, Edward H; Schröder, Tim; Englund, Dirk

    2014-01-01

    Optical spectroscopy is a fundamental tool in numerous areas of science and technology. Much effort has focused on miniaturizing spectrometers, but thus far at the cost of high spectral resolution and broad operating range. Here, we describe a compact spectrometer without this trade-off. The device relies on imaging multi-mode interference from leaky modes along a highly multimode tapered optical fiber, resulting in spectrally distinguishable images that form a basis for reconstructing an incident light spectrum. This tapered fiber multimode interference spectrometer enables the acquisition of broadband spectra in a single camera exposure with a measured resolution of 40 pm in the visible spectrum and 10 pm in the infrared spectrum, which are comparable to the performance of grating spectrometers. Spectroscopy from 500 nm to 1600 nm is demonstrated, though operation across the entire transparency window of silica fibers is possible. Multimode interference spectroscopy of leaky modes is suitable in a variety o...

  4. Quantum efficiency measurement on a CCD detector in the 0.3- to 1100-nm spectral region

    Science.gov (United States)

    Poletto, Luca; Boscolo, Alessio; Pelizzo, M. G.; Placentino, Leonardo; Tondello, Giuseppe

    1997-10-01

    The performances of a CCD have been evaluated in a very wide spectral region, which comprises near IR, visible, near and far UV, EUV and soft x-ray spectral regions. The CCD detector is a back illuminated one, 512 by 512 format, 24 by 24 micrometer squared pixel. The performed measurements consist mainly on the determination of the quantum efficiency in the 0.3 - 1100 nm (4.5 keV - 1 eV) spectral region. Three different experimental setup have been used: a Czerny-Turner monochromator for the 1100 - 250 nm region, a Johnson-Onaka monochromator for the 250 - 30 nm region, and a grazing incidence Rowland monochromator for the 25 - 0.3 nm region. The tested CCD exhibits high values of quantum efficiency in the analyzed spectral range, representing a very useful detector of radiation in the extended optical domain.

  5. Multicenters in Ce3+ visible emission of YAG ceramics

    Science.gov (United States)

    Lupei, A.; Lupei, V.; Gheorghe, C.; Hau, S.; Ikesue, A.

    2014-11-01

    New aspects on the Ce3+ in YAG transparent ceramics, obtained from absorption and emission spectra in the 10-300 K range, under different visible excitation wavelengths, along with emission decays are presented. The spectra and lifetime of regular CeY3+ center are similar to those reported for single crystals. In the attempt to reveal perturbed Ce3+ centers by defects, the 5d ? 4f emission spectra under pulsed 532 nm (5 ns) excitation (below the Ce3+ absorption band) were recorded. The spectra and decays (at different wavelengths) are function on temperature, revealing at least three types of Ce3+ new emitting centers. The low temperature spectra, different from those of CeY3+ center, are dominated by a set of strongly perturbed centers with very short lifetimes. At least two other types of perturbed centers were separated by using wavelength and temperature dependences of decays. The spectral characteristics of these perturbed Ce3+ centers by lattice defects are analyzed in terms of the effects of the structural changes induced by Ce3+ doping on the interaction with defects, by using recent reported results.

  6. Measurement of the refractive index dispersion of As2Se3 bulk glass and thin films prior to and after laser irradiation and annealing using prism coupling in the near- and mid-infrared spectral range

    International Nuclear Information System (INIS)

    The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5-10.6 ?m range. The instrumental error was found to be ±0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.

  7. Point-focus spectral splitting solar concentrator for multiple cells concentrating photovoltaic system

    CERN Document Server

    Maragliano, Carlo; Stefancich, Marco

    2015-01-01

    In this paper we present and experimentally validate a low-cost design of a spectral splitting concentrator for the efficient conversion of solar energy. The optical device consists of a dispersive prismatic lens made of polycarbonate designed to simultaneously concentrate the solar light and split it into its spectral components. With respect to our previous implementation, this device concentrates the light along two axes and generates a light pattern compatible with the dimensions of a set of concentrating photovoltaic cells while providing a higher concentration ratio. The mathematical framework and the constructive approach used for the design are presented and the device performance is simulated using ray-tracing software. We obtain spectral separation in the visible range within a 3x1 cm2 area and a maximum concentration of 210x for a single wavelength. The device is fabricated by injection molding and its performance is experimentally investigated. We measure an optical transmissivity above 90% in the...

  8. Spectral imaging for contamination detection in food

    DEFF Research Database (Denmark)

    Carstensen, Jens Michael Technical University of Denmark,

    Spectral imaging is a technique with a big potential for surface chemistry mapping of heterogeneous samples. It works by making a spectrum in every pixel of an image, and this spectrum may under the right circumstances be transformed into abundance maps for chemical components. One important application of the technique is finding anomalies I supposedly homogeneous matter or homogeneous mixtures. This application occurs frequently in the food industry when different types of contamination are to be detected. Contaminants could be e.g. foreign matter, process-induced toxins, and microbiological spoilage. Many of these contaminants may be detected in the wavelength range visible to normal silicium-based camera sensors i.e. 350-1050 nm with proper care during sample preparation, sample presentation, image acquisition and analysis. This presentation will give an introduction to the techniques behind the VideometerLab instrument, that implements the thoughts above, and show examples including fusarium detection inbarley, measuring microbial meat spoilage, and making humidity maps. It will also illustrate methodology for spectral image analysis.

  9. Spectral Signatures of Leaf Fall Diseases in Hevea Brasiliensis Using a Handheld Spectroradiometer

    Directory of Open Access Journals (Sweden)

    Hj.Kamaruzaman Jusoff

    2010-01-01

    Full Text Available Subtle sensitive changes in leaf canopy reflectance of a disease infected trees can be detected by a spectroradiometer. A typical method of detecting tree stress caused by diseases or pest infestations includes the analysis of spectroradiometry. Early detection of forest tree stress would be useful to minimize tree losses especially in a forest plantation area.  The main purpose of this study is to develop the spectral library of individual rubber trees being attacked by diseases using a ground-based handheld field spectroradiometer. The specific objective is to identify the spectral signature characteristics of healthy (control and “unhealthy” or stressed rubber trees due to leaf diseases as causal factors. The spectral reflectance of each infected rubber tree was separated according to the different wavelength and percent reflectance. The spectral signatures of rubber trees being attacked by diseases were characterized by a low reflectance probably due to the low chlorophyll content in the leaves leading to the tree under stress, thus easily separated from the healthy rubber. Results indicated that three groups of infected trees were well separated at the 530 - 650 nm (visible wavelength averaging from 0 – 30 percent reflectance. The spectral reflectances of rubber trees with leaf disease in visible (VIS wavelength were not consistently separable. However, the spectral reflectance of leaf diseases can be well separated at the near infrared range region covering from 700 - 850 nm wavelength with a 30 – 80 percent reflectance for leaf diseases, respectively. The study implies that leaf diseases for rubber trees can only be identified successfully at the NIR range of wavelength from 700 – 850 nm with a 20-80 percent reflectance. The development of such signature library profile of disease affecting rubber trees will certainly assists in the development of an early disease warning system using an airborne hyperspectral imaging system technology being currently developed in UPM’s Forest Geospatial Information & Survey Laboratory, at Lebuh Silikon, Universiti Putra Malaysia, Serdang.

  10. Visible light communication for advanced driver assistant systems

    OpenAIRE

    Kumar, Navin; Nero, Luis Alves; Aguiar, Rui L.

    2009-01-01

    VIsible light communication for advanced Driver Assistant Systems (VIDAS) is an outdoor application using the visible spectrum of light emitting diodes (LED). A simple traffic light set up based on LED traffic lights for traffic information transmission has been analyzed in this paper. Various important design parameters have been optimized through intensive investigation based on gain variation over 100 m of transmission range. This process is expected to simplify the front-end receiver desi...

  11. A visible metamaterial fabricated by self-assembly method

    OpenAIRE

    Boyi Gong; Xiaopeng Zhao; Zhenzhen Pan; Sa Li; Xiaonong Wang; Yan Zhao; Chunrong Luo

    2014-01-01

    A visible negative-index metamaterial was fabricated by adopting a template-assisted and self-assembled electrochemical deposition method. Originating from the inherent characteristic of bottom-up fabrication, it has been demonstrated by the effective medium theory that the metamaterial resonance could realize a negative index at visible wavelengths if the degree of asymmetry is kept in a moderate range. This was experimentally substantiated by fabricating an asymmetric Ag–polyvinyl alcohol...

  12. Fast calculations of the spectral diffuse-to-global ratios for approximating spectral irradiance at the street canyon level

    Science.gov (United States)

    Carrasco-Hernandez, Roberto; Smedley, Andrew R. D.; Webb, Ann R.

    2015-05-01

    Two radiative transfer models are presented that simplify calculations of street canyon spectral irradiances with minimum data input requirements, allowing better assessment of urban exposures than can be provided by standard unobstructed radiation measurements alone. Fast calculations improve the computational performance of radiation models, when numerous repetitions are required in time and location. The core of the models is the calculation of the spectral diffuse-to-global ratios (DGR) from an unobstructed global spectral measurement. The models are based on, and have been tested against, outcomes of the SMARTS2 algorithm (i.e. Simple Model of the Atmospheric Radiative Transfer of Sunshine). The modelled DGRs can then be used to partition global spectral irradiance values into their direct and diffuse components for different solar zenith angles. Finally, the effects of canyon obstructions can be evaluated independently on the direct and diffuse components, which are then recombined to give the total canyon irradiance. The first model allows ozone and aerosol inputs, while the second provides a further simplification, restricted to average ozone and aerosol contents but specifically designed for faster calculations. To assess the effect of obstructions and validate the calculations, a set of experiments with simulated obstructions (simulated canyons) were performed. The greatest source of uncertainty in the simplified calculations is in the treatment of diffuse radiation. The measurement-model agreement is therefore dependent on the region of the sky obscured and ranges from <5 % at all wavelengths to 20-40 % (wavelength dependent) when diffuse sky only is visible from the canyon.

  13. Spectral Ranking

    OpenAIRE

    Vigna, Sebastiano

    2009-01-01

    This note tries to attempt a sketch of the history of spectral ranking, a general umbrella name for techniques that apply the theory of linear maps (in particular, eigenvalues and eigenvectors) to matrices that do not represent geometric transformations, but rather some kind of relationship between entities. Albeit recently made famous by the ample press coverage of Google's PageRank algorithm, spectral ranking was devised more than sixty years ago, almost exactly in the sam...

  14. Spectral stratigraphy

    Science.gov (United States)

    Lang, Harold R.

    1991-01-01

    A new approach to stratigraphic analysis is described which uses photogeologic and spectral interpretation of multispectral remote sensing data combined with topographic information to determine the attitude, thickness, and lithology of strata exposed at the surface. The new stratigraphic procedure is illustrated by examples in the literature. The published results demonstrate the potential of spectral stratigraphy for mapping strata, determining dip and strike, measuring and correlating stratigraphic sequences, defining lithofacies, mapping biofacies, and interpreting geological structures.

  15. ICRAF-ISRIC Soil VNIR Spectral Library

    OpenAIRE

    World Agroforestry Centre (ICRAF); ISRIC

    2010-01-01

    The ICRAF-ISRIC Soil VNIR Spectral Library contains visible near infrared spectra of 4,438 soils selected from the Soil Information System (ISIS) of the International Soil Reference and Information Centre (ISRIC). The samples consist of all physically archived samples at ISRIC in 2004 for which soil attribute data was available. The spectra were measured at the World Agroforestry Center's (ICRAF) ... Soil and Plant Spectral Diagnostic Laboratory. The samples are from 58 countries spanning Afr...

  16. Spectral Evolution of an Earth-Like Planet

    CERN Document Server

    Kaltenegger, L; Jucks, K W

    2006-01-01

    We have developed a characterization of the geological evolution of the Earths atmosphere and surface in order to model the observable spectra of an Earth-like planet through its geological history. These calculations are designed to guide the interpretation of an observed spectrum of such a planet by future instruments that will characterize exoplanets. Our models focus on spectral features that either imply habitability or are required for habitability. These features are generated by H2O, CO2, CH4, O2, O3, N2O, and vegetation-like surface albedos. We chose six geological epochs to characterize. These epochs exhibit a wide range in abundance for these molecules, ranging from a CO2 rich early atmosphere, to a CO2/CH4-rich atmosphere around 2 billion years ago to a present-day atmosphere. We analyzed the spectra to quantify the strength of each important spectral feature in both the visible and thermal infrared spectral regions, and the resolutions required to unambiguously observe the features for each epoch...

  17. Skyglow effects in UV and visible spectra: Radiative fluxes

    Science.gov (United States)

    Kocifaj, Miroslav; Solano Lamphar, Hector Antonio

    2013-09-01

    Several studies have tried to understand the mechanisms and effects of radiative transfer under different night-sky conditions. However, most of these studies are limited to the various effects of visible spectra. Nevertheless, the invisible parts of the electromagnetic spectrum can pose a more profound threat to nature. One visible threat is from what is popularly termed skyglow. Such skyglow is caused by injudiciously situated or designed artificial night lighting systems which degrade desired sky viewing. Therefore, since lamp emissions are not limited to visible electromagnetic spectra, it is necessary to consider the complete spectrum of such lamps in order to understand the physical behaviour of diffuse radiation at terrain level. In this paper, the downward diffuse radiative flux is computed in a two-stream approximation and obtained ultraviolet spectral radiative fluxes are inter-related with luminous fluxes. Such a method then permits an estimate of ultraviolet radiation if the traditionally measured illuminance on a horizontal plane is available. The utility of such a comparison of two spectral bands is shown, using the different lamp types employed in street lighting. The data demonstrate that it is insufficient to specify lamp type and its visible flux production independently of each other. Also the UV emissions have to be treated by modellers and environmental scientists because some light sources can be fairly important pollutants in the near ultraviolet. Such light sources can affect both the living organisms and ambient environment.

  18. Skyglow effects in UV and visible spectra: radiative fluxes.

    Science.gov (United States)

    Kocifaj, Miroslav; Solano Lamphar, H A

    2013-09-30

    Several studies have tried to understand the mechanisms and effects of radiative transfer under different night-sky conditions. However, most of these studies are limited to the various effects of visible spectra. Nevertheless, the invisible parts of the electromagnetic spectrum can pose a more profound threat to nature. One visible threat is from what is popularly termed skyglow. Such skyglow is caused by injudiciously situated or designed artificial night lighting systems which degrade desired sky viewing. Therefore, since lamp emissions are not limited to visible electromagnetic spectra, it is necessary to consider the complete spectrum of such lamps in order to understand the physical behaviour of diffuse radiation at terrain level. In this paper, the downward diffuse radiative flux is computed in a two-stream approximation and obtained ultraviolet spectral radiative fluxes are inter-related with luminous fluxes. Such a method then permits an estimate of ultraviolet radiation if the traditionally measured illuminance on a horizontal plane is available. The utility of such a comparison of two spectral bands is shown, using the different lamp types employed in street lighting. The data demonstrate that it is insufficient to specify lamp type and its visible flux production independently of each other. Also the UV emissions have to be treated by modellers and environmental scientists because some light sources can be fairly important pollutants in the near ultraviolet. Such light sources can affect both the living organisms and ambient environment. PMID:23792881

  19. Morphological, structural, and spectral characteristics of amorphous iron sulfates

    Science.gov (United States)

    Sklute, E. C.; Jensen, H. B.; Rogers, A. D.; Reeder, R. J.

    2015-04-01

    Current or past brine hydrologic activity on Mars may provide suitable conditions for the formation of amorphous ferric sulfates. Once formed, these phases would likely be stable under current Martian conditions, particularly at low- to mid-latitudes. Therefore, we consider amorphous iron sulfates (AIS) as possible components of Martian surface materials. Laboratory AIS were created through multiple synthesis routes and characterized with total X-ray scattering, thermogravimetric analysis, scanning electron microscopy, visible/near-infrared (VNIR), thermal infrared (TIR), and Mössbauer techniques. We synthesized amorphous ferric sulfates (Fe(III)2(SO4)3 · ~ 6-8H2O) from sulfate-saturated fluids via vacuum dehydration or exposure to low relative humidity (<11%). Amorphous ferrous sulfate (Fe(II)SO4 · ~ 1H2O) was synthesized via vacuum dehydration of melanterite. All AIS lack structural order beyond 11 Å. The short-range (<5 Å) structural characteristics of amorphous ferric sulfates resemble all crystalline reference compounds; structural characteristics for the amorphous ferrous sulfate are similar to but distinct from both rozenite and szomolnokite. VNIR and TIR spectral data for all AIS display broad, muted features consistent with structural disorder and are spectrally distinct from all crystalline sulfates considered for comparison. Mössbauer spectra are also distinct from crystalline phase spectra available for comparison. AIS should be distinguishable from crystalline sulfates based on the position of their Fe-related absorptions in the visible range and their spectral characteristics in the TIR. In the NIR, bands associated with hydration at ~1.4 and 1.9 µm are significantly broadened, which greatly reduces their detectability in soil mixtures. AIS may contribute to the amorphous fraction of soils measured by the Curiosity rover.

  20. Highly Visible, Curiously Intangible

    Science.gov (United States)

    G. A. Clark (Arizona State University; Department of Anthropology)

    1999-03-26

    Is it just lack of data that limits our understanding of modern human origins, or are we not looking at the existing data with an open mind? Clark uses the transition from the Middle to the Upper Paleolithic in Europe, between 35,000 and 45,000 years before present, to illustrate his view that blinkered vision rather than lack of data are holding us back. He maintains that research traditions are reinforcing perceived differences between modern humans and neandertals, rather than allowing for a range of paleolithic adaptations held in common by all circum-Mediterranean hominids.

  1. Visible-frequency hyperbolic metasurface.

    Science.gov (United States)

    High, Alexander A; Devlin, Robert C; Dibos, Alan; Polking, Mark; Wild, Dominik S; Perczel, Janos; de Leon, Nathalie P; Lukin, Mikhail D; Park, Hongkun

    2015-06-11

    Metamaterials are artificial optical media composed of sub-wavelength metallic and dielectric building blocks that feature optical phenomena not present in naturally occurring materials. Although they can serve as the basis for unique optical devices that mould the flow of light in unconventional ways, three-dimensional metamaterials suffer from extreme propagation losses. Two-dimensional metamaterials (metasurfaces) such as hyperbolic metasurfaces for propagating surface plasmon polaritons have the potential to alleviate this problem. Because the surface plasmon polaritons are guided at a metal-dielectric interface (rather than passing through metallic components), these hyperbolic metasurfaces have been predicted to suffer much lower propagation loss while still exhibiting optical phenomena akin to those in three-dimensional metamaterials. Moreover, because of their planar nature, these devices enable the construction of integrated metamaterial circuits as well as easy coupling with other optoelectronic elements. Here we report the experimental realization of a visible-frequency hyperbolic metasurface using single-crystal silver nanostructures defined by lithographic and etching techniques. The resulting devices display the characteristic properties of metamaterials, such as negative refraction and diffraction-free propagation, with device performance greatly exceeding those of previous demonstrations. Moreover, hyperbolic metasurfaces exhibit strong, dispersion-dependent spin-orbit coupling, enabling polarization- and wavelength-dependent routeing of surface plasmon polaritons and two-dimensional chiral optical components. These results open the door to realizing integrated optical meta-circuits, with wide-ranging applications in areas from imaging and sensing to quantum optics and quantum information science. PMID:26062510

  2. No-visible-scar cholecystectomy

    Directory of Open Access Journals (Sweden)

    Tadeusz M. Wróblewski

    2010-12-01

    Full Text Available Introduction: Single incision laparoscopic surgery (SILS is a laparoscopic method providing a good cosmetic effect,but requiring the application of special ports and instruments enabling the surgeon to perform the procedure.We report three-ports cholecystectomy through umbilical and suprapubic incisions performed with typical laparos -copic instruments which calls no-visible-scar cholecystectomy (NVSC.Material and methods: Twenty patients with symptomatic cholelithiasis were qualified for NVSC. Typical CO2 pneumoperitoneumwas done after umbilical skin incision. Two ports of 5 mm were inserted in the maximum externaledges of this incision. After cystic duct and cystic artery dissection the right one was exchanged for a port of 11 mm.The second incision for the 11-mm trocar for the laparoscope was done in the suprapubic median line within the hairarea.Results: Cholecystectomies were performed without any conversion to classical laparoscopic cholecystectomy (LCHor open surgery. They were not technically identical due to the gradual improvement in the access and manipulationof instruments. The time of the intervention ranged from 2 hours during the introduction of the new method to 50 minfor the last procedures. No postoperative complications were observed and all patients were discharged not later thanafter conventional LCH.Conclusions: NVSC is a three-port laparoscopic intervention performed with typical laparoscopic instruments. It ismore convenient for the surgeon than single incision LCH, because the placement of the optic in the suprapubic regiongives more space for the instruments. It also provides a very good cosmetic effect of the intervention. The describedprocedure is easy to learn and in case of technical problems additional ports can be applied (as in typical LCH.

  3. Studying the spectral characteristics of 121 impact craters on Mercury

    Science.gov (United States)

    D'Incecco, Piero; Helbert, Jörn; D'Amore, Mario; Maturilli, Alessandro; Ferrari, Sabrina; Head, James W.; Klima, Rachel L.; Izenberg, Noam R.; McClintock, William E.; Solomon, Sean C.

    2014-05-01

    We have characterized the spectral reflectance of 121 complex impact craters on Mercury. To do so, we have combined Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Visible and Infrared Spectrograph (VIRS) data with Mercury Dual Imaging System (MDIS) images, both acquired from orbit by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. The MASCS spectra were taken from the DLR database, which currently contains several million MASCS VIRS spectra normalized at 700 nm wavelength to provide a first-order correction for variations in observing conditions. The craters for this study were selected on the basis of geological and physical criteria from the MDIS global dataset. For each impact crater, we mapped as independent geological units the central peak, floor deposits, wall deposits, and external ejecta from 1 to 10 crater radii outward of the crater rim (at a sampling step of 1 radius). From the DLR database, we retrieved MASCS VIRS observations for each geological unit of the 121 impact craters. We explored two different classification schemes. In the first scheme we included all reflectance observations, even those shared between units for different craters. In the second scheme, we excluded spectra that are shared by multiple areas. Under the first scheme, therefore, the same spectral unit can be assigned to two or more craters, whereas under the second scheme spectral units are uniquely linked to a single crater. Preliminary results of our study show a range of distinctive spectra for the crater central peaks. Spectral variations are also seen among crater floor deposits. The goal of the study is to complete a global spectral map as a basis for improving our understanding of crustal stratigraphy on Mercury using impact craters as stratigraphic markers.

  4. Correlation of Spectral Solar Irradiance with solar activity as measured by VIRGO

    CERN Document Server

    Wehrli, C; Shapiro, A I

    2013-01-01

    Context. The variability of Solar Spectral Irradiance over the rotational period and its trend over the solar activity cycle are important for understanding the Sun-Earth connection as well as for observational constraints for solar models. Recently the SIM experiment on SORCE has published an unexpected negative correlation with Total Solar Irradiance of the visible spectral range. It is compensated by a strong and positive variability of the near UV range. Aims. We aim to verify whether the anti-correlated SIM/SORCE-trend in the visible can be confirmed by independent observations of the VIRGO experiment on SOHO. The challenge of all space experiments measuring solar irradiance are sensitivity changes of their sensors due to exposure to intense UV radiation, which are difficult to assess in orbit. Methods. We analyze a 10-year time series of VIRGO sun photometer data between 2002 and 2012. The variability of Spectral Solar Irradiance is correlated with the variability of the Total Solar Irradiance, which is...

  5. Visible spectroscopy of the new ESO Large Program on trans-Neptunian objects and Centaurs: final results

    CERN Document Server

    Fornasier, S; de Bergh, C; Alvarez-Candal, A; DeMeo, F; Merlin, F; Perna, D; Guilbert, A; Delsanti, A; Dotto, E; Doressoundiram, A

    2009-01-01

    A second large programme (LP) for the physical studies of TNOs and Centaurs, started at ESO Cerro Paranal on October 2006 to obtain high-quality data, has recently been concluded. In this paper we present the spectra of these pristine bodies obtained in the visible range during the last two semesters of the LP. We investigate the spectral behaviour of the TNOs and Centaurs observed, and we analyse the spectral slopes distribution of the full data set coming from this LP and from the literature. We computed the spectral slope for each observed object, and searched for possible weak absorption features. A statistical analysis was performed on a total sample of 73 TNOs and Centaurs to look for possible correlations between dynamical classes, orbital parameters, and spectral gradient. We obtained new spectra for 28 bodies, 15 of which were observed for the first time. All the new presented spectra are featureless, including 2003 AZ84, for which a faint and broad absorption band possibly attributed to hydrated sil...

  6. Apparatus for measuring the emittance of materials from far infrared to visible wavelengths in extreme conditions of temperature

    Science.gov (United States)

    De Sousa Meneses, D.; Melin, P.; del Campo, L.; Cosson, L.; Echegut, P.

    2015-03-01

    A computer controlled circular turntable equipped with a blackbody reference and an integrated axisymmetric heating system based on a CO2 laser is at the heart of the reported device. It allows performing emittance measurements in the spectral domain ranging from far infrared up to visible light and in a wide range of temperature. The apparatus includes two spectrometers and was built to achieve optimal experimental conditions of measurement, i.e. environmental stability and single optical path for the acquisition of the thermal fluxes. The specific design of the apparatus is firstly described; applied procedures for the characterization of the blackbody reference, laser heating and the retrieval of the emittance spectra are given after. Finally measurements obtained for ruby, NdGaO3 and platinum are presented to illustrate the capacities of the apparatus.

  7. Spectral Ranking

    CERN Document Server

    Vigna, Sebastiano

    2009-01-01

    This note tries to attempt a sketch of the history of spectral ranking, a general umbrella name for techniques that apply the theory of linear maps (in particular, eigenvalues and eigenvectors) to matrices that do not represent geometric transformations, but rather some kind of relationship between entities. Albeit recently made famous by the ample press coverage of Google's PageRank algorithm, spectral ranking was devised more than fifty years ago, almost exactly in the same terms, and has been studied in psychology and social sciences. I will try to describe it in precise and modern mathematical terms, highlighting along the way the contributions given by previous scholars.

  8. Visible light scatter as quantitative information source on milk constituents

    DEFF Research Database (Denmark)

    Melentieva, Anastasiya; Kucheryavskiy, Sergey

    2012-01-01

    VISIBLE LIGHT SCATTER AS A QUANTITATIVE INFORMATION SOURCE ON MILK CONSTITUENTS A. Melenteva 1, S. Kucheryavski 2, A. Bogomolov 1,31Samara State Technical University, Molodogvardeyskaya Street 244, 443100 Samara, Russia. 2Aalborg University, campus Esbjerg, Niels Bohrs vej 8, 6700 Esbjerg, Denmark. 3J&M Analytik AG, Willy-Messerschmitt-Strasse 8, 73457 Essingen, Germany. bogomolov@j-m.de Fat and protein are two major milk nutrients that are routinely analyzed in the dairy industry. Growing food quality requirements promote the dissemination of spectroscopic analysis, enabling real-time monitoring of processes and products. Optical analysis is generally performed in near and middle infrared (NIR and MIR) regions and relies on the component absorbance and Beer’s Law. The light scatter effect is therefore considered as a disturbance to be avoided during the measurement or eliminated at the data analysis stage. The region of visible (Vis) light (400-800 nm) is economically attractive, because it offers a range of inexpensive light sources, optics and detectors. At present, however, it is commonly considered useless, because of the light scatter by fat globules (1-10 ?m) and protein micelles (80-200 ?m) that strongly dominates; therefore, making the classical absorbance analysis hardly applicable. At the same time, diffused light by itself delivers information on the milk composition, specifically, fat content as illustrated in Fig. 1, and can potentially be used for the quantitative analysis. The main task here is to extract individual quantitative information on milk fat and total protein content from spectral data. This is particularly challenging problem in the case of raw natural milk, where the fat globule sizes may essentially differ depending on source. Fig. 1. Spots of light transmitted through homogenized milk samples with different fat content. The preceding research [1] has shown that individual scatter patterns of fat and protein in non-homogenized milk can be distinguished, thus, enabling their quantitative multivariate analysis. In the present study, a representative designed set of raw milk samples with simultaneously varying fat, total protein and particle size distribution has been analyzed in the Vis spectral region. The feasibility of raw milk analysis by PLS regression on spectral data has been proved. The root mean-square errors below 0.10% and 0.04% for fat and protein, respectively, have been obtained. PLS components were interpreted in terms of captured information. The results obtained provide a basis for the replacement of traditional spectroscopy by custom optical analyzers, optimized for the purpose of milk analysis. Preliminary achievements in this new research area are presented and discussed. References: [1] A. Bogomolov, S. Dietrich, B. Boldrini, R.W. Kessler, Food Chemistry (2012), doi:10.1016/j.foodchem.2012.02.077.

  9. Multispectral antireflection coating simultaneously effective in visible, diode laser, Nd-YAG and eye safe laser wavelength

    International Nuclear Information System (INIS)

    Multi-spectral antireflection coating effective in visible region for sighting system, Nd-YAG laser wavelength for designator/seeker system, both diode laser and eye safe laser wavelength for ranging purpose can use common objective/receiver optics highly useful for state of art laser instrumentation. In this paper, design and fabrication of antireflection coating simultaneously effective in visible region (500 to 650nm), diode laser at 904±25nm and Nd-YAG laser at 1064±25nm, and erbium-glass laser wavelength at 1540±25nm has been reported. Inhomogeneous refractive index profile as suggested by Southwell was used to design this coating. The inhomogeneous profile was then approximated with eleven steps from substrate to air medium in order to obtain desirable antireflection property in the visible and laser wavelengths. These steps were then converted into the available coating materials (titanium-di-oxide and magnesium fluoride) of twenty-two layer stack. The multilayer stack was fabricated by using electron beam gun evaporation system in Balzers BAK-600 vacuum coating unit. The result achieved were less than 2% average reflection (98% average transmission) from 500 to 650nm, 1.5% reflection (98.5% average transmission) at 904nm, 1064nm and 1540nm. The coated samples successfully passed the specifications of MIL-C-14806 tests

  10. Two-dimensional solar spectropolarimetry with the KIS/IAA Visible Imaging Polarimeter

    Science.gov (United States)

    Beck, C.; Bellot Rubio, L. R.; Kentischer, T. J.; Tritschler, A.; Del Toro Iniesta, J. C.

    2010-09-01

    Context. Spectropolarimetry at high spatial and spectral resolution is a basic tool to characterize the magnetic properties of the solar atmosphere. Aims: We introduce the KIS/IAA Visible Imaging Polarimeter (VIP), a new post-focus instrument that upgrades the TESOS spectrometer at the German Vacuum Tower Telescope (VTT) into a full vector polarimeter. VIP is a collaboration between the Kiepenheuer Institut für Sonnenphysik (KIS) and the Instituto de Astrofísica de Andalucía (IAA-CSIC). Methods: We describe the optical setup of VIP, the data acquisition procedure, and the calibration of the spectropolarimetric measurements. We show examples of data taken between 2005 and 2008 to illustrate the potential of the instrument. Results: VIP is capable of measuring the four Stokes profiles of spectral lines in the range from 420 to 700 nm with a spatial resolution better than 0farcs5. Lines can be sampled at 40 wavelength positions in 60 s, achieving a noise level of about 2 × 10-3 with exposure times of 300 ms and pixel sizes of 0farcs17 × 0farcs17 (2 × 2 binning). The polarization modulation is stable over periods of a few days, ensuring high polarimetric accuracy. The excellent spectral resolution of TESOS allows the use of sophisticated data analysis techniques such as Stokes inversions. One of the first scientific results of VIP presented here is that the ribbon-like magnetic structures of the network are associated with a distinct pattern of net circular polarization away from disk center. Conclusions: VIP performs spectropolarimetric measurements of solar magnetic fields at a spatial resolution that is only slightly worse than that of the Hinode spectropolarimeter, while providing a 2D field field of view and the possibility to observe up to four spectral regions sequentially with high cadence. VIP can be used as a stand-alone instrument or in combination with other spectropolarimeters and imaging systems of the VTT for extended wavelength coverage.

  11. Growth, spectral and thermal studies of an efficient NLO material: Diaquadicinnamatocadmium(II)

    International Nuclear Information System (INIS)

    A nonlinear metal–organic crystal, diaquadicinnamatocadmium(II) has been grown by controlled gel diffusion technique. Sodium metasilicate was used to prepare the gel. The chemical composition of the crystal has been determined by CHN analysis. Powder X-ray diffraction studies confirm the crystalline nature of the grown crystal. Functional groups present in the compound were identified by FT-IR spectral analysis. The thermal decomposition of the compound was studied using thermogravimetry (TG). The optical transparency range and the lower cut-off wavelength were identified from the UV-Visible-NIR spectrum. The NLO activity of the grown crystal was confirmed using Kurtz and Perry powder test

  12. Aqueous alteration on main belt primitive asteroids: results from visible spectroscopy

    CERN Document Server

    Fornasier, S; Barucci, M A; Lazzarin, M

    2014-01-01

    This work focuses on the study of the aqueous alteration process which acted in the main belt and produced hydrated minerals on the altered asteroids. The aqueous alteration is particularly important for unraveling the processes occurring during the earliest times of the Solar System history, as it can give information both on the asteroids thermal evolution and on the localization of water sources in the asteroid belt. We present new spectral observations in the visible region of 80 asteroids belonging to the primitive classes C, G, F, B and P. We combine the present observations with the visible spectra of asteroids available in the literature for a total of 600 primitive main belt asteroids. Our analysis shows that the aqueous alteration sequence starts from the P-type objects, practically unaltered, and increases through the F, B, C, and G asteroids. Around 50% of the observed C-type asteroids show absorption features in the vis. range due to hydrated silicates, implying that more than 70% of them will ha...

  13. A versatile femtosecond stimulated Raman spectroscopy setup with tunable pulses in the visible to near infrared

    Science.gov (United States)

    Zhu, Liangdong; Liu, Weimin; Fang, Chong

    2014-07-01

    We demonstrate a versatile and efficient setup to perform femtosecond stimulated Raman spectroscopy (FSRS). Technical innovations are implemented to achieve the wavelength tunability for both the picosecond narrowband Raman pump pulse and femtosecond broadband Raman probe pulse. Using a simplified one-grating scheme in a home-built second harmonic bandwidth compressor followed by a two-stage noncollinear optical parametric amplifier, we tune the Raman pump pulse from ca. 480 to 750 nm. To generate the suitable Raman probe pulse in tandem, we rely on our recently demonstrated broadband up-converted multicolor array technique that readily provides tunable broadband laser sidebands across the visible to near-infrared range. This unique setup has unparalleled flexibility for conducting FSRS. We measure the ground-state Raman spectra of a cyclohexane standard using tunable pump-probe pairs at various wavelengths across the visible region. The best spectral resolution is ˜12 cm-1. By tuning the pump wavelength closer to the electronic absorption band of a photoacid pyranine in water, we observe the pre-resonantly enhanced Raman signal. The stimulated Raman gain of the 1627 cm-1 mode is increased by over 15 times.

  14. A versatile femtosecond stimulated Raman spectroscopy setup with tunable pulses in the visible to near infrared

    International Nuclear Information System (INIS)

    We demonstrate a versatile and efficient setup to perform femtosecond stimulated Raman spectroscopy (FSRS). Technical innovations are implemented to achieve the wavelength tunability for both the picosecond narrowband Raman pump pulse and femtosecond broadband Raman probe pulse. Using a simplified one-grating scheme in a home-built second harmonic bandwidth compressor followed by a two-stage noncollinear optical parametric amplifier, we tune the Raman pump pulse from ca. 480 to 750?nm. To generate the suitable Raman probe pulse in tandem, we rely on our recently demonstrated broadband up-converted multicolor array technique that readily provides tunable broadband laser sidebands across the visible to near-infrared range. This unique setup has unparalleled flexibility for conducting FSRS. We measure the ground-state Raman spectra of a cyclohexane standard using tunable pump-probe pairs at various wavelengths across the visible region. The best spectral resolution is ?12?cm?1. By tuning the pump wavelength closer to the electronic absorption band of a photoacid pyranine in water, we observe the pre-resonantly enhanced Raman signal. The stimulated Raman gain of the 1627?cm?1 mode is increased by over 15 times.

  15. Generation of tunable few optical-cycle pulses by visible-to-infrared frequency conversion

    Science.gov (United States)

    Darginavi?ius, J.; Tamošauskas, G.; Piskarskas, A.; Valiulis, G.; Dubietis, A.

    2012-07-01

    We demonstrate a simple method for infrared few optical-cycle pulse generation, which is based on collinear visible-to-infrared frequency conversion and involves difference-frequency generation and subsequent two-step optical parametric amplification. The numerical simulations and experiments using BBO crystals show an efficient frequency down conversion of visible ˜20 fs pulses from a commercial blue-pumped noncollinear optical parametric amplifier yielding 1.2-2.4 ?m tunable sub-100 ?J pulses with duration of 3 to 5 optical-cycles. The proposed method could be readily extended to generate few optical-cycle pulses in the mid-infrared spectral range (up to 5.5 ?m) using, e.g., LiIO3 and LiNbO3 crystals, as demonstrated by the numerical simulations. In these crystals, even shorter, two-optical-cycle mid-infrared pulses could be obtained at particular wavelengths where group velocity matching between the signal and idler waves is achieved.

  16. Spectral Experiments+

    CERN Document Server

    Rivin, Igor

    2014-01-01

    We describe extensive computational experiments on spectral properties of random objects - random cubic graphs, random planar triangulations, and Voronoi and Delaunay diagrams of random (uniformly distributed) point sets on the sphere). We look at bulk eigenvalue distribution, eigenvalue spacings, and locality properties of eigenvectors. In all cases we discover completely new (at least to this author) phenomena.

  17. Integrated infrared and visible image sensors

    Science.gov (United States)

    Fossum, Eric R. (Inventor); Pain, Bedabrata (Inventor)

    2000-01-01

    Semiconductor imaging devices integrating an array of visible detectors and another array of infrared detectors into a single module to simultaneously detect both the visible and infrared radiation of an input image. The visible detectors and the infrared detectors may be formed either on two separate substrates or on the same substrate by interleaving visible and infrared detectors.

  18. Revisiting visibility in the plane

    DEFF Research Database (Denmark)

    Wilkinson, Bryan Thomas

    Abstract We consider two closely related problems: computing the region visible from a point amid simple polygonal obstacles and computing the lower envelope of a set of disjoint segments. Visibility problems such as these were proposed and promptly solved in the late'80s and early'90s before the widespread popularity of the word RAM model. All previously published algorithms thus run in ? (n log n) time, although they can be sped up in the word RAM model to some extent by substituting appropriate word RAM data structures

  19. Retrieval of spheroid particle size distribution from spectral extinction data in the independent mode using PCA approach

    International Nuclear Information System (INIS)

    An improved anomalous diffraction approximation (ADA) method is presented for calculating the extinction efficiency of spheroids firstly. In this approach, the extinction efficiency of spheroid particles can be calculated with good accuracy and high efficiency in a wider size range by combining the Latimer method and the ADA theory, and this method can present a more general expression for calculating the extinction efficiency of spheroid particles with various complex refractive indices and aspect ratios. Meanwhile, the visible spectral extinction with varied spheroid particle size distributions and complex refractive indices is surveyed. Furthermore, a selection principle about the spectral extinction data is developed based on PCA (principle component analysis) of first derivative spectral extinction. By calculating the contribution rate of first derivative spectral extinction, the spectral extinction with more significant features can be selected as the input data, and those with less features is removed from the inversion data. In addition, we propose an improved Tikhonov iteration method to retrieve the spheroid particle size distributions in the independent mode. Simulation experiments indicate that the spheroid particle size distributions obtained with the proposed method coincide fairly well with the given distributions, and this inversion method provides a simple, reliable and efficient method to retrieve the spheroid particle size distributions from the spectral extinction data. -- Highlights: ? Improved ADA is presented for calculating the extinction efficiency of spheroids. ? Selection principle about spectral extinction data is developed based on PCA. ? Improved Tikhonov iteration method is proposed to retrieve the spheroid PSD.

  20. Wavelength discrimination in the ‘visible’ and ultraviolet spectrum by pigeons

    OpenAIRE

    Emmerton, Jacky; Delius, Juan

    1980-01-01

    Using operant conditioning methods, the pigeon's wavelength discrimination abilities were assessed in two experiments to generate discrimination functions. Both these functions showed three minima at 460, 530 and 595 nm. In the second wavelength discrimination experiment, extending measurements into the UV spectral region, pigeons also maintained good discrimination between wavelengths within the UV range tested. A fourth minimum was indicated at the lower end of the spectral range tested (36...

  1. Innovative monolithic detector for tri-spectral (THz, IR, Vis) imaging

    Science.gov (United States)

    Pocas, S.; Perenzoni, M.; Massari, N.; Simoens, F.; Meilhan, J.; Rabaud, W.; Martin, S.; Delplanque, B.; Imperinetti, P.; Goudon, V.; Vialle, C.; Arnaud, A.

    2012-10-01

    Fusion of multispectral images has been explored for many years for security and used in a number of commercial products. CEA-Leti and FBK have developed an innovative sensor technology that gathers monolithically on a unique focal plane arrays, pixels sensitive to radiation in three spectral ranges that are terahertz (THz), infrared (IR) and visible. This technology benefits of many assets for volume market: compactness, full CMOS compatibility on 200mm wafers, advanced functions of the CMOS read-out integrated circuit (ROIC), and operation at room temperature. The ROIC houses visible APS diodes while IR and THz detections are carried out by microbolometers collectively processed above the CMOS substrate. Standard IR bolometric microbridges (160x160 pixels) are surrounding antenna-coupled bolometers (32X32 pixels) built on a resonant cavity customized to THz sensing. This paper presents the different technological challenges achieved in this development and first electrical and sensitivity experimental tests.

  2. General approach to high power, coherent visible and ultraviolet light sources

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer

    2009-01-01

    The main goal of this project is to develop a generic approach to synthesise any wavelength in the visible and UV spectral region based on sum frequency generation. The approach is based on a hybrid system combining solid state and semiconductor technology. The generation of light in the UV spectral region require nonlinear materials with a transparency range extending into the ultraviolet, the ability to sustain high photon energies and with the ability to obtain phasematching for the desired nonlinear conversion process. In this project experiments are conducted using three differently co-doped GdCOB crystals. The crystals are optimized for noncritical phasematching in the blue-UV spectral region through co-doping with Lu and Sc, a nonlinear coefficient for these crystals of 0.78, 0.81 and 0.89 pm/V are measured, which is comparable to LBO. The ability to adjust the noncritical phasematching by co-doping of these crystals makes them promising candidates for generation of light in the blue-UV region. A novelmethod for cavity dumping based on nonlinear frequency conversion is investigated. A high finesse laser is constructed with an intracavity nonlinear material inserted in a beam waist. The nonlinear material is phasematched to support sum frequency generation between the 1342nm circulating field in the cavity and a single pass passively Q-Switched 1064nm laser, effectively converting the circulating power whenever a single pass pulse is present. Furthermore the Q-Switched laser can easily be frequency doubled in a single pass configuration, therefore the nonlinear cavity dumping approach is suggested for the generation of 340nm UV light, using 532nm pulses to cavity dump a 946nm Nd:YAG laser. Furthermore experiments are conducted tripling a Q-switched 1064nm laser to 355nm by cascaded second harmonic and sum frequency generation using periodically poled KTP and BBO for the SHG and SFG process, respectively. The 355nm light is used to promote different photo induced reactions. The main limitation of reaching any desired wavelength in the visible spectrum using sum frequency generation is the limited laser lines available from efficient solid state lasers. One fundamental way to overcome this limitation is to use semiconductor lasers to provide one of the fundamental fields. The problem of using semiconductor lasers for nonlinear frequency conversion has previously been the lag of coherence of these devices. This problem can, however, to a large extent be solved using external cavity tapered diode lasers, which allows for the generation of coherent radiation at the watt power level. Using differently doped semiconductor materials these devices can potentially cover the wavelength range from the red and into the infrared spectral range. These devices are very efficient, however, the available devices in the visible region are still very inefficient, therefore a generic approach using high finesse solid state lasers with intracavity nonlinear materials and single pass tapered diode was sought to cover the shorter wavelength range. In this project more then 300mW of 488nm power is generated by direct sum frequency mixing of a solid state laser and a single pass external cavity tapered diode laser. The performance of the device is compared to systems where the output of the tapered diode laser is spatially filtered and to an all solid state laser system based on mixing with a single frequency Ti:Sapphire laser. Finally experiments with a semiconductor disk laser used as the high finesse cavity laser and sum frequency mixing with a single pass solid state laser is coniv ducted. These experiments show that it is possible to design systems exploiting the benefits of semiconductor based lasers and nonlinear sum frequency generation to cover large parts of the optical spectrum, which has previously been difficult to access due to the lag of efficient, coherent light sources

  3. Search for Olivine Spectral Signatures on the Surface of Vesta

    Science.gov (United States)

    Palomba, E.; De Sanctis, M. C.; Ammannito, E.; Capaccioni, F.; Capria, M. T.; Farina, M.; Frigeri, A.; Longobardo, A.; Tosi, F.; Zambon, F.; McSween, H. Y.; Mittlefehldt, D. W.; Russell, C. T.; Raymond, C. A.; Sunshine, J.; McCord, T. B.

    2012-01-01

    The occurrence of olivines on Vesta were first postulated from traditional petrogenetic models which suggest the formation of olivine as lower crustal cumulates. An indirect confirmation is given by their presence as a minor component in some samples of diogenite meteorites, the harzburgitic diogenites and the dunitic diogenites, and as olivine mineral clasts in howardites. Another indication for this mineral was given by interpretations of groundbased and Hubble Space Telescope observations that suggested the presence of local olivine-bearing units on the surface of Vesta. The VIR instrument onboard the DAWN mission has been mapping Vesta since July 2011. VIR acquired hyperspectral images of Vesta s surface in the wavelength range from 0.25 to 5.1 m during Approach, Survey and High Altitude Mapping (HAMO) orbits that allowed a 2/3 of the entire asteroid surface to be mapped. The VIR operative spectral interval, resolution and coverage is suitable for the detection and mapping of any olivine rich regions that may occur on the Vesta surface. The abundance of olivine in diogenites is typically lower than 10% but some samples richer in olivine are known. However, we do not expect to have extensive exposures of olivine-rich material on Vesta. Moreover, the partial overlap of olivine and pyroxene spectral signatures will make olivine difficult to detect. Different spectral parameters have been used to map olivine on extraterrestrial bodies, and here we discuss the different approaches used, and develop new ones specifically for Vesta. Our new methods are based on combinations of the spectral parameters relative to the 1 and 2 micron bands (the most prominent spectral features of Vesta surface in the visible and the infrared), such as band center locations, band depths, band areas, band area ratios. Before the direct application to the VIR data, the efficiency of each approach is evaluated by means of analysis of laboratory spectra of HED meteorites, pyroxenes, olivines and their mixtures.

  4. Visibility Management and the Body

    Science.gov (United States)

    Lasser, Jon; Wicker, Nichole

    2008-01-01

    The authors employed grounded theory to explore the high school experiences of gay, lesbian, and bisexual students in Central Texas. The central phenomenon that emerged from the study was Visibility Management, or decisions made regarding the disclosure of invisible traits. This article reviews the results of this research with an emphasis on the…

  5. NITRATE DETERMINATION IN CHILEAN CALICHE SAMPLES BY UV-VISIBLE ABSORBANCE MEASUREMENTS AND MULTIVARIATE CALIBRARON

    Scientific Electronic Library Online (English)

    MANUEL, BRAVO; ALEJANDRO C, OLWIERT; BEATRIZ, OELCKERS.

    Full Text Available Multivariate calibration of UV-visible spectral data using partial least-squares (PLS) has been applied to the determination of the nitrate content in Chilean Caliche samples, in the concentration range from 1 to 20% NaNO3 The multivariate approach is required since the samples do also contain unkno [...] wn interferences which are spectrally active in the useful wavelength region for nitrate quantitation (near 301 nm). A set of fifteen calibration samples was employed to build the multivariate model, selected using the Kennard-Stone methodology, starting from real Caliche samples whose nitrate content was previously determined using the reference Devarda method. The figures of merit of the multivariate model were satisfactory (the limit of detection and quantitation reached 0.04% and 0.12 % of NaNO3, respectively, with an average error of prediction of 0.3 % of NaNO3). Then, the PLS model was then applied to a set of independent Caliche samples. The results were compared with a univariate UV approach, and with the nitrate content determined by the reference method, using the linear regression of predicted vs. reference concentration values, together with the elliptical joint confidence region test for the slope and intercept of the latter regression. The results indícate that the univariate method is unsuitable for analyzing the presently studied samples, unlike the multivariate model. Finally, the analytical methodology proposed appears as reliable and cheap alternative for routine analysis of a large number of caliche samples.

  6. Visible light emission in highly charged Kr13+ ions colliding with an Al surface

    International Nuclear Information System (INIS)

    The visible light emissions from the sputtered Al species and the neutralized projectiles during Kr13+ ions bombarding the Al surface have been measured in the wavelength range of 300–600 nm. The three spectral lines belonging to transitions of Al I 3p 2P3/2o–3d 2D5/2 at 309.0, Al II 3d 3D1–4f 2F2o at 358.5 and Al I 3p 2P3/2o–4s 2S1/2 at 396.1 nm have been observed, as well as five spectral lines from the incident ion attributing to transitions of Kr I 5s 2[3/2]1o–5p 2[1/2]1 at 587.9, Kr II 4d 4D1/2–5p 2S1/2 at 485.8, Kr II 4d 3D2o–5p 3D3 at 434.3, Kr II 5s 2P3/2–5p 4S3/2o at 430.1 and Kr II 5s 4P1/2–5p 2D3/2o at 409.9 nm

  7. Two-dimensional solar spectropolarimetry with the KIS/IAA Visible Imaging Polarimeter

    CERN Document Server

    Beck, C; Kentischer, T J; Tritschler, A; Iniesta, J C del Toro

    2010-01-01

    Spectropolarimetry at high spatial and spectral resolution is a basic tool to characterize the magnetic properties of the solar atmosphere. We introduce the KIS/IAA Visible Imaging Polarimeter (VIP), a new post-focus instrument that upgrades the TESOS spectrometer at the German VTT into a full vector polarimeter. VIP is a collaboration between the KIS and the IAA. We describe the optical setup of VIP, the data acquisition procedure, and the calibration of the spectropolarimetric measurements. We show examples of data taken between 2005 and 2008 to illustrate the potential of the instrument. VIP is capable of measuring the four Stokes profiles of spectral lines in the range from 420 to 700 nm with a spatial resolution better than 0.5". Lines can be sampled at 40 wavelength positions in 60 s, achieving a noise level of about 2 x 10E-3 with exposure times of 300 ms and pixel sizes of 0.17" x 0.17" (2 x 2 binning). The polarization modulation is stable over periods of a few days, ensuring high polarimetric accura...

  8. Models for Estimating the Physical Properties of Paddy Soil Using Visible and Near Infrared Reflectance Spectroscopy

    Science.gov (United States)

    Gholizadeh, A.; Amin, M. S. M.; Bor?vka, L.; Saberioon, M. M.

    2014-07-01

    A fast and convenient soil analytical technique is needed for soil quality assessment and precision soil management. The main objective of this study was to evaluate the ability of visible (Vis) and near-infrared (NIR) refl ectance spectroscopy to predict paddy soil properties in a typical Malaysian paddy fi eld. To assess the utility of spectroscopy for soil physical characteristics (bulk density, moisture content, clay, silt and sand) prediction, 118 soil samples were used for laboratory analysis and optical measurement in the Vis-NIR region using an analytical spectral device (ASD) FieldSpec spectroradiometer (350-2500 nm). The Savitzky-Golay algorithm and stepwise multiple linear regression (SMLR) were then applied to preprocess, model, and predict the properties on the basis of their spectral refl ectance within the Vis-NIR range. One-third of the samples (40 samples) were withheld for validation purposes. The study revealed that Vis and NIR spectroscopy calibration models for all the measured soil physical characteristics provided a good fi t (R2 > 0.78); hence Vis and NIR (specifi cally NIR refl ectance) can be considered to be a reliable tool to assess soil physical properties of Malaysian paddy fi elds. The results of this study could contribute signifi cantly to developing site-specifi c management.

  9. Search for spectral features in transiting planets with GAPS project

    Science.gov (United States)

    Benatti, S.; Claudi, R. U.; Erculiani, M. S.; Rubio, A. G.; Borsa, F.; Bonavita, M.; Covino, E.; Desidera, S.; Gratton, R.; Lanza, A. F.; Maggio, A.; Micela, G.; Pagano, I.; Piotto, G.; Poretti, E.; Sozzetti, A.

    2014-03-01

    The GAPS Project (Global Architecture of Planetary Systems) is the result of a concerted collaborative effort of a large fraction ofthe Italian community interested in exoplanets and of a few well known experts abroad. The observational large program of GAPSis specifically designed to characterize the global architectural properties of exoplanetary systems, taking advantage of thecapabilities provided by HARPS-N spectrograph, mounted at the TNG (La Palma, Canary Island). GAPS is organized in subprograms,each focused on different aims. The spectra obtained for the Rossiter-McLaughlin (RML) and Asteroseismology(AST)/Star-Planet Interaction (SPI) subprograms provide useful data to search and analyse spectral features in the visible range,in order to characterize the atmospheres of planets in transit.

  10. [Research on the progress in the light-emitting mechanism of ZnO in the visible region].

    Science.gov (United States)

    Wang, Ji-hong; Xu, Chang-shan; Xue, Xiang-xin; Zhao, Bing

    2014-12-01

    In the past few years we have witnessed a revival of, and subsequent rapid expansion in, the research on zinc oxide (ZnO). We present a review of current research on the optical properties of ZnO. The wide range of useful properties displayed by ZnO has been recognized for a long time. The high electron mobility, high thermal conductivity, wide and direct band gap and large exciton binding energy make ZnO suitable for a wide range of devices, including two light-emitting tubes, transparent thin-film transistors, laser diodes that operate in the blue and ultraviolet region of the spectrum, and ultraviolet detector. Optically pumped lasing has been reported in ZnO platelets, ZnO thin films, and clusters consisting of ZnO nanocrystals and ZnO nanowires. Up to now, a number of synthetic methods including electrospinning, hydrothermal, sol-hydrothermal, chemical vapor deposition, spin coating and electrochemical deposition have been used to prepare ZnO nanomaterials such as nanofibers, nanowires, nanorods and so on. The growth and properties of ZnO nanostructures have been extensively studied, but the photoluminescence mechanism in the visible range has seldom been summarized. The photoluminescence spectra can reflect some important information such as surface defects and oxygen vacancies, surface states, photo-induced charge carrier separation and recombination processes in nano-sized semiconductor materials. The optical emission of ZnO is equally complex, with a variety of defect emission states whose structural origins remain controversial. A detailed discussion of photoluminescence, in the visible spectral range, is provided. In this review, we provided a detailed overview on the luminescence mechanism of ZnO nanostructures in the visible range. The review detail exhibits the following four mechanisms of the optical properties of ZnO in the visible range: the influence of the quantum confinement effect, the band edge modulation that has effect of photoluminescence, the influence of surface modification, and the control of defects' concentration. PMID:25881409

  11. A titanium nitride based metamaterial for applications in the visible

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Saha, Bivas

    2013-01-01

    Epitaxially grown TiN/Al0.6Sc0.4N superlattice behaves as a hyperbolic metamaterial (HMM) in the visible range. Since HMMs enhance photonic-density-of-states and reduce lifetime of an emitter, we observed nine times decrease in lifetime of a dye molecule placed close to this HMM. © 2013 The Optical Society.

  12. New Spectral Observations of the Variable Galaxy Kaz 163

    Science.gov (United States)

    Karapetyan, Emilia L.

    2014-07-01

    Kaz 163 is a close double galaxy. Its southern component S is compact, with a very blue nucleus, in which heated active processes take place. From time to time gas formations are ejected from it, which behave themselves like emission components around the main emission lines H? and H?, around both from their long-wave and short-wave sides. This paper presents the spectral data of new observations, which were carried out with the 2.6m telescope at the Byurakan Astrophysical Observatory in September 2011. During the former observation in October 1981, lines [NII] ?? 6584,6548 were not visible in the spectrum of the component S. In 2001 they were already visible on the spectrum, and on the spectrum obtained in 2011 they already surpassed the intensity of H?. The magnitude of the component S is also changing: its nucleus is very blue and its U-B = -0 m .63. In the soft X-ray spectral range (0.1-2 keV) the flux of the radiation changed by 45% during 55,000 sec, and in the hard one (2-10keV) it changed up to 3.4 times. Photoindices ? for the soft and hard ranges in the spectrum of galaxy S, unlike other objects, do not so much differ from each other. The mean value for the first interval is approximately 2.5 and is equal -2.0 for the second one. On the histogram of redshifts Kaz 163 corresponds to the first big peak of the distribution. It is concluded that the component S of the galaxy Kaz 163 is a NLS1 galaxy, with the development of their evolution, is in the preliminary stage. Component N is a normal elliptical galaxy with no activity.

  13. Visible spectroscopy in the DIII-D divertor

    International Nuclear Information System (INIS)

    Spectroscopy measurements in the DIII-D divertor have been carried out with a survey spectrometer which provides simultaneous registration of the visible spectrum over the region 400--900 nm with a resolution of 0.2 nm. Broad spectral coverage is achieved through use of a fiberoptic transformer assembly to map the curved focal plane of a fast (f/3) Rowland spectrograph into a rastered format on the rectangular sensor area of a two-dimensional CCD camera. Vertical grouping of pixels during CCD readout integrates the signal intensity over the height of each spectral segment in the rastered image, minimizing readout time. For the full visible spectrum, readout time is 50 ms. Faster response time (< 10 ms) may be obtained by selecting for readout just a small number of the twenty spectral segments in the image on the CCD. Simultaneous recording of low charge states of carbon, oxygen and injected impurities has yielded information about gas recycling and impurity behavior at the divertor strike points. Transport of lithium to the divertor region during lithium pellet injection has been studied, as well as cumulative deposition of lithium on the divertor targets from pellet injection over many successive discharges

  14. UV Radiation and Visible Light Induce hsp70 Gene Expression in the Antarctic Psychrophilic Ciliate Euplotes focardii.

    Science.gov (United States)

    Fulgentini, Lorenzo; Passini, Valerio; Colombetti, Giuliano; Miceli, Cristina; La Terza, Antonietta; Marangoni, Roberto

    2015-08-01

    The psychrophilic ciliate Euplotes focardii inhabits the shallow marine coastal sediments of Antarctica, where, over millions of years of evolution, it has reached a strict molecular adaptation to such a constant-temperature environment (about -2 °C). This long evolution at sub-zero temperatures has made E. focardii unable to respond to heat stress with the activation of its heat shock protein (hsp) 70 genes. These genes can, however, be expressed in response to other stresses, like the oxidative one, thus indicating that the molecular adaptation has exclusively altered the heat stress signaling pathways, while it has preserved hsp70 gene activation in response to other environmental stressors. Since radiative stress has proved to be affine to oxidative stress in several organisms, we investigated the capability of UV radiation to induce hsp70 transcription. E. focardii cell cultures were exposed to several different irradiation regimes, ranging from visible only to a mixture of visible, UV-A and UV-B. The irradiation values of each spectral band have been set to be comparable with those recorded in a typical Antarctic spring. Using Northern blot analysis, we measured the expression level of hsp70 immediately after irradiation (0-h-labeled samples), 1 h, and 2 h from the end of the irradiation. Surprisingly, our results showed that besides UV radiation, the visible light was also able to induce hsp70 expression in E. focardii. Moreover, spectrophotometric measurements have revealed no detectable endogenous pigments in E. focardii, making it difficult to propose a possible explanation for the visible light induction of its hsp70 genes. Further research is needed to conclusively clarify this point. PMID:25666535

  15. Infrared Spectra and Visibilities as Probes of the Outer Atmospheres of Red Supergiant Stars

    OpenAIRE

    Tsuji, Takashi

    2006-01-01

    In the light of the recent results of the stellar interferometry, we examine the nature of the extra molecular layer outside the photosphere of red super- giant stars, so far studied mostly with the use of the infrared spectra. Although the visibility data are more direct probes of the spatial structure of the outer atmosphere, it is essential that they are analyzed in combination with the spectral data of a wide spectral coverage. In the case of the M2 supergiant mu Cephei,...

  16. Self-referenced spectral interferometry theory

    OpenAIRE

    Oksenhendler, Thomas

    2012-01-01

    Self-referenced spectral interferometry, a newly introduced ultrafast pulse characterization is described and reviewed theoretically. Validity range, temporal dynamic, resolution and precision are detailed in the scope of different experimental set-ups. Ultimate performances for ultrashort pulses in terms of minimal or maximal pulse durations, distortions, spectral bandwidth, temporal dynamic and range are estimated, simulated and explained in detail.

  17. Recent variability of the solar spectral irradiance and its impact on climate modelling

    CERN Document Server

    Ermolli, I; de Wit, T Dudok; Krivova, N A; Tourpali, K; Weber, M; Unruh, Y C; Gray, L; Langematz, U; Pilewskie, P; Rozanov, E; Schmutz, W; Shapiro, A; Solanki, S K; Woods, T N

    2013-01-01

    The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of recent chemistry-climate model (CCM) simulations have shown that this might have significant implications on the Earth's atmosphere. Motivated by these results, we summarize here our current knowledge of SSI variability and its impact on Earth's climate. We present a detailed overview of existing SSI measurements and provide thorough comparison of models available to date. SSI changes influence the Earth's atmosphere, both directly, through changes in shortwave (SW) heating and therefore, temp...

  18. Visible/Near-Infrared Spectra of Experimentally Shocked Plagioclase Feldspars

    Science.gov (United States)

    Johnson, J. R.

    2003-01-01

    Minerals subjected to high shock pressures exhibit structural changes with increasing pressure (e.g., fractures, deformations, formation of diaplectic glass, and complete melting [1-6]). Petrologic and thermal infrared spectroscopic studies have shown that diaplectic glass (maskelynite) formation in feldspars occurs between 25-45 GPa, while significant melting occurs above 45 GPa [7- 12]. Past studies of visible/near-infrared spectra of shocked plagioclase feldspars demonstrated few variations in spectral features with pressure except for a decrease in the absorption feature near 1250 nm and an overall decrease in albedo [13-17]. We report new visible/near-infrared spectra of albite- and anorthiterich rocks experimentally shocked from 17-56 GPa.

  19. No-visible-scar cholecystectomy

    OpenAIRE

    Tadeusz M. Wróblewski; Sebastian Piotrowicz; Marcin Kotulski; Piotr Gierej; Bogna Ziarkiewicz-Wróblewska

    2010-01-01

    Introduction: Single incision laparoscopic surgery (SILS) is a laparoscopic method providing a good cosmetic effect,but requiring the application of special ports and instruments enabling the surgeon to perform the procedure.We report three-ports cholecystectomy through umbilical and suprapubic incisions performed with typical laparos -copic instruments which calls no-visible-scar cholecystectomy (NVSC).Material and methods: Twenty patients with symptomatic cholelithiasis were qualified for N...

  20. Visual quality beyond artifact visibility

    Science.gov (United States)

    Redi, Judith A.

    2013-03-01

    The Electronic imaging community has devoted a lot of effort to the development of technologies that can predict the visual quality of images and videos, as a basis for the delivery of optimal visual quality to the user. These systems have been based for the most part on a visibility-centric approach, assuming the more artifacts are visible, the higher is the annoyance they provoke, the lower the visual quality. Despite the remarkable results achieved with this approach, recently a number of studies suggested that the visibility-centric approach to visual quality might have limitations, and that other factors might influence the overall quality impression of an image or video, depending on cognitive and affective mechanisms that work on top of perception. In particular, interest in the visual content, engagement and context of usage have been found to impact on the overall quality impression of the image/video. In this paper, we review these studies and explore the impact that affective and cognitive processes have on the visual quality. In addition, as a case study, we present the results of an experiment investigating on the impact of aesthetic appeal on visual quality, and we show that users tend to be more demanding in terms of visual quality judging beautiful images.

  1. Automatic visible watermarking of images

    Science.gov (United States)

    Rao, A. Ravishankar; Braudaway, Gordon W.; Mintzer, Frederick C.

    1998-04-01

    Visible image watermarking has become an important and widely used technique to identify ownership and protect copyrights to images. A visible image watermark immediately identifies the owner of an image, and if properly constructed, can deter subsequent unscrupulous use of the image. The insertion of a visible watermark should satisfy two conflicting conditions: the intensity of the watermark should be strong enough to be perceptible, yet it should be light enough to be unobtrusive and not mar the beauty of the original image. Typically such an adjustment is made manually, and human intervention is required to set the intensity of the watermark at the right level. This is fine for a few images, but is unsuitable for a large collection of images. Thus, it is desirable to have a technique to automatically adjust the intensity of the watermark based on some underlying property of each image. This will allow a large number of images to be automatically watermarked, this increasing the throughput of the watermarking stage. In this paper we show that the measurement of image texture can be successfully used to automate the adjustment of watermark intensity. A linear regression model is used to predict subjective assessments of correct watermark intensity based on image texture measurements.

  2. Visible and Near-Infrared Multispectral Analysis of Rocks at Meridiani Planum, Mars, by the Mars Exploration Rover Opportunity

    OpenAIRE

    Knoll, Andrew; Yen, Albert S.; Watters, Wesley A.; Thompson, Shane D.; Soderblom, Jason; Morris, Richard V.; Grotzinger, John P.; Squyres, Steven W.; McLennan, Scott M.; Jolliff, Bradley L.; Johnson, Jeffrey R; Bell, James F. III; Farrand, William H.

    2007-01-01

    [1] Multispectral measurements in the visible and near infrared of rocks at Meridiani Planum by the Mars Exploration Rover Opportunity's Pancam are described. The Pancam multispectral data show that the outcrops of the Burns formation consist of two main spectral units which in stretched 673, 535, 432 nm color composites appear buff- and purple-colored. These units are referred to as the HFS and LFS spectral units based on higher and lower values of 482 to 535 nm slope. Spectral characteristi...

  3. Injection- Seeded Optoplasmonic Amplifier in the Visible

    Science.gov (United States)

    Gartia, Manas Ranjan; Seo, Sujin; Kim, Junhwan; Chang, Te-Wei; Bahl, Gaurav; Lu, Meng; Liu, Gang Logan; Eden, J. Gary

    2014-08-01

    A hybrid optoplasmonic amplifier, injection-seeded by an internally-generated Raman signal and operating in the visible (563-675 nm), is proposed and evidence for amplification is presented. Comprising a gain medium tethered to a whispering gallery mode (WGM) resonator with a protein, and a plasmonic surface, the optical system described here selectively amplifies a single (or a few) Raman line(s) produced within the WGM resonator and is well-suited for routing narrowband optical power on-a-chip. Over the past five decades, optical oscillators and amplifiers have typically been based on the buildup of the field from the spontaneous emission background. Doing so limits the temporal coherence of the output, lengthens the time required for the optical field intensity to reach saturation, and often is responsible for complex, multiline spectra. In addition to the spectral control afforded by injection-locking, the effective Q of the amplifier can be specified by the bandwidth of the injected Raman signal. This characteristic contrasts with previous WGM-based lasers and amplifiers for which the Q is determined solely by the WGM resonator.

  4. Visible Imaging Diagnostic on Tore-Supra

    International Nuclear Information System (INIS)

    Full text of publication follows: Research for thermonuclear fusion aims at energy production using fusion reactions between deuterium and tritium nuclei. To this end, a deuterium/tritium mixture has to be heated to a very high temperature (about 100 millions degrees). Chemical and physical sputtering erodes the plasma facing components (PFC), leading to an impurity influx to the plasma. Estimating this erosion source is important both for the PFC lifetime and the quality of the confinement. In fact, impurities reaching the plasma core radiate energy and dilute the fuel. In this contribution, we describe an erosion diagnostic operated on the Tore Supra tokamak, consisting in the combination of visible spectroscopy and filtered imaging over a full TPL (Toroidal Pumped Limiter) sector. Quantitative measurements of spectral lines brightness on four spectrometer chords monitoring the TPL top are used to process the corresponding filtered images, namely to remove background emission or unwanted lines. The particle influx from the TPL's vicinity is obtained from photon fluxes measurements [1], which require absolute calibration in intensity of the system. Filtered images provide the spatial pattern of erosion, from which the total eroded carbon flux is reconstructed. The variation of the particle influx with the input power is studied by analyzing a dedicated experimental campaign. References: [1] Behringer K. et al. Plasma Physics and Controlled Fusion, Vol. 31, No. 14, ppand Controlled Fusion, Vol. 31, No. 14, pp. 2059 to 2099, 1989. (authors)

  5. Aerosol-induced correlation between visibility and atmospheric electricity.

    OpenAIRE

    Harrison, R. G.

    2012-01-01

    Atmospheric aerosol acts to both reduce the background concentration of natural cluster ions, and to attenuate optical propagation. Hence, the presence of aerosol has two consequences, the reduction of the air’s electrical conductivity and the visual range. Ion-aerosol theory and Koschmieder’s visibility theory are combined here to derive the related non-linear variation of the atmospheric electric potential gradient with visual range. A substantial sensitivity is found under poor visual ...

  6. Polarization dependent visible supercontinuum generation in the nanoweb fiber.

    Science.gov (United States)

    Yan, Peiguang; Shu, Jie; Ruan, Shuangchen; Zhao, Jian; Zhao, Junqing; Du, Chenlin; Guo, Chunyu; Wei, Huifeng; Luo, Jie

    2011-03-14

    We have fabricated a novel nanoweb fiber with web-like bundle of the fused-silica membranes with different thickness in its cross section. We pumped the 0.55-?m-thick membrane with 200-fs laser pulse at 800-nm just adjacent to its second-zero-dispersion wavelength, and demonstrated the polarization dependent visible supercontinuum (SC). The mode patterns were recorded in detail and analyzed at different polarization angles of incident pulse. The broadband spectrum range from ~350 nm to 950 nm is achieved for TM mode excitation. The tunable visible SC in the nanoweb fiber may be used in the substrate integrated waveguide for sensing. PMID:21445134

  7. Visible and infrared spectroscopy to evaluate soil quality in degraded sites: an applicative study in southern Italy

    Science.gov (United States)

    Ancona, Valeria; Matarrese, Raffaella; Salvatori, Rosamaria; Salzano, Roberto; Regano, Simona; Calabrese, Angelantonio; Campanale, Claudia; Felice Uricchio, Vito

    2014-05-01

    Land degradation processes like organic matter impoverishment and contamination are growing increasingly all over the world due to a non-rational and often sustainable spread of human activities on the territory. Consequently the need to characterize and monitor degraded sites is becoming very important, with the aim to hinder such main threats, which could compromise drastically, soil quality. Visible and infrared spectroscopy is a well-known technique/tool to study soil properties. Vis-NIR spectral reflectance, in fact, can be used to characterize spatial and temporal variation in soil constituents (Brown et al., 2006; Viscarra Rossel et al., 2006), and potentially its surface structure (Chappell et al., 2006, 2007). It is a rapid, non-destructive, reproducible and cost-effective analytical method to analyse soil properties and therefore, it can be a useful method to study land degradation phenomena. In this work, we present the results of proximal sensing investigations of three degraded sites (one affected by organic and inorganic contamination and two affected by soil organic matter decline) situated southern Italy close to Taranto city (in Apulia Region). A portable spectroradiometer (ASD-FieldSpec) was used to measure the reflectance properties in the spectral range between 350-2500 nm of the soil, in the selected sites, before and after a recovery treatment by using compost (organic fertilizer). For each measurement point the soil was sampled in order to perform chemical analyses to evaluate soil quality status. Three in-situ campaigns have been carried out (September 2012, June 2013, and September 2013), collecting about 20 soil samples for each site and for each campaign. Chemical and spectral analyses have been focused on investigating soil organic carbon, carbonate content, texture and, in the case of polluted site, heavy metals and organic toxic compounds. Statistical analyses have been carried out to test a prediction model of different soil quality indicators based on the spectral signatures behaviour of each sample ranging.

  8. Borescope Inspects With Visible Or Ultraviolet Light

    Science.gov (United States)

    Molina, Orlando G.

    1989-01-01

    Quartz optical fibers improve performance at ultraviolet wavelengths. Borescope used to inspect interior of small-diameter tubing by visible light and ultraviolet light. Employs quartz fibers to conduct ultraviolet light and visible light with high efficiency.

  9. Beyond Language Equivalence on Visibly Pushdown Automata

    DEFF Research Database (Denmark)

    Srba, Jiri

    2009-01-01

    We study (bi)simulation-like preorder/equivalence checking on the class of visibly pushdown automata and its natural subclasses visibly BPA (Basic Process Algebra) and visibly one-counter automata. We describe generic methods for proving complexity upper and lower bounds for a number of studied preorders and equivalences like simulation, completed simulation, ready simulation, 2-nested simulation preorders/equivalences and bisimulation equivalence. Our main results are that all the mentioned equivalences and preorders are EXPTIME-complete on visibly pushdown automata, PSPACE-complete on visibly one-counter automata and P-complete on visibly BPA. Our PSPACE lower bound for visibly one-counter automata improves also the previously known DP-hardness results for ordinary one-counter automata and one-counter nets. Finally, we study regularity checking problems for visibly pushdown automata and show that they can be decided in polynomial time.

  10. Visible and near UV light-induced scattering of LiNbO3:Fe crystals and material characterization

    Science.gov (United States)

    Ellabban, Mostafa A.

    2015-01-01

    We present an experimental study of reconstructing parasitic gratings that produce simultaneous wide-angle polarization-anisotropic and -isotropic light induced scattering. The gratings were recorded in lithium niobate crystals doped with iron (LiNbO3:Fe) using an ordinary-polarized pump beam in the visible and the near UV spectral ranges. The reconstruction was performed at different readout angles, wavelengths and linear polarization states. The main features of reconstructing the parasitic gratings at different readout conditions are qualitatively explained by a simple phenomenological model based on the Ewald sphere construction. The obtained results and the scattering pattern were applied to determine the birefringence, its sign and further to estimate the relative contribution of diffusion and bulk photovoltaic effect to the photorefractive effect, as well as the ratios of product of the Pockels and the photovoltaic tensors components that contribute to the readout of the gratings at different readout polarizations.

  11. Evaluations of particulate mass loading from visibility observations and atmospheric turbidity measurements: Pt. 1

    International Nuclear Information System (INIS)

    Two extinction models for continental and rural particles were defined by using a very accurate computer programme based on Mie extinction theory for spherical particles. The first extinction model gives several sets of volume extinction coefficients at seven visible and near-infra-red wave-lengths, calculated for twenty-seven Junge-type size distribution curves (with Junge parameter ranging from 1.8 to 4.4) and for eight relative-humidity values of the air. This model also gives the corresponding values of Aangstroem's exponent ? and mean particle mass. The second extinction model gives similar sets of data, calculated for two log-normal size distribution curves of tropospheric and large rural particles at five relative-humidity values of the air. These monomodal models can be used to determine bimodal extinction models consisting of variable number fractions of tropospherics and rural particles. Evaluations of the particulate mass loading can be obtained from measurements of visual range and atmospheric turbidity, choosing the most appropriate extinction model on the basis of the spectral features characterizing atmospheric attenuation. Measurements of visibility and atmospheric turbidity in two rural localities of the Po valley were examined by employing both the present extinction models and other extinction models commonly used. The comparison of the results shows that the Junge-type extinction model can be reliably used in cases in which the exponent Junge-typein cases in which the exponent Junge-type extinction model and bimodal model were found to give realistic evaluations of the lower and upper limits of particulate mass loading

  12. Nanoantennas for visible and infrared radiation

    International Nuclear Information System (INIS)

    Nanoantennas for visible and infrared radiation can strongly enhance the interaction of light with nanoscale matter by their ability to efficiently link propagating and spatially localized optical fields. This ability unlocks an enormous potential for applications ranging from nanoscale optical microscopy and spectroscopy over solar energy conversion, integrated optical nanocircuitry, opto-electronics and density-of-states engineering to ultra-sensing as well as enhancement of optical nonlinearities. Here we review the current understanding of metallic optical antennas based on the background of both well-developed radiowave antenna engineering and plasmonics. In particular, we discuss the role of plasmonic resonances on the performance of nanoantennas and address the influence of geometrical parameters imposed by nanofabrication. Finally, we give a brief account of the current status of the field and the major established and emerging lines of investigation in this vivid area of research.

  13. Huanglongbing (Citrus Greening Detection Using Visible, Near Infrared and Thermal Imaging Techniques

    Directory of Open Access Journals (Sweden)

    Reza Ehsani

    2013-02-01

    Full Text Available This study demonstrates the applicability of visible-near infrared and thermal imaging for detection of Huanglongbing (HLB disease in citrus trees. Visible-near infrared (440–900 nm and thermal infrared spectral reflectance data were collected from individual healthy and HLB-infected trees. Data analysis revealed that the average reflectance values of the healthy trees in the visible region were lower than those in the near infrared region, while the opposite was the case for HLB-infected trees. Moreover, 560 nm, 710 nm, and thermal band showed maximum class separability between healthy and HLB-infected groups among the evaluated visible-infrared bands. Similarly, analysis of several vegetation indices indicated that the normalized difference vegetation index (NDVI, Vogelmann red-edge index (VOG and modified red-edge simple ratio (mSR demonstrated good class separability between the two groups. Classification studies using average spectral reflectance values from the visible, near infrared, and thermal bands (13 spectral features as input features indicated that an average overall classification accuracy of about 87%, with 89% specificity and 85% sensitivity could be achieved with classification models such as support vector machine for trees with symptomatic leaves.

  14. Estimation of low-resolution visible spectra from RGB imagery

    Science.gov (United States)

    Schau, H. C.

    2009-05-01

    While able to measure the red, green, and blue channels, color imagers are not true spectral imagers capable of spectral measurements. In this paper we present a processing technique for estimating low resolution visible spectra from (RGB) imagery components. Such a methodology will find application in separating reflectivity components from source illumination as performed in Retinex or Linear Models. Numerical processing is discussed and formulated within non-regulated iterative restoration methodology. Numerical stability and convergence are considered relative to speed and accuracy as well as calibration data effects on overall results. Implementation is demonstrated together with several suggestions for real time processing. Imager calibration methodology is presented together with several results. Limitations of the method are discussed as well as directions for further investigations.

  15. A sampling approach for predicting the eating quality of apples using visible - near infrared spectroscopy

    DEFF Research Database (Denmark)

    Martinez Vega, Mabel Virginia; Sharifzadeh, Sara

    2013-01-01

    BACKGROUND Visible–near infrared spectroscopy remains a method of increasing interest as a fast alternative for the evaluation of fruit quality. The success of the method is assumed to be achieved by using large sets of samples to produce robust calibration models. In this study we used representative samples of an early and a late season apple cultivar to evaluate model robustness (in terms of prediction ability and error) on the soluble solids content (SSC) and acidity prediction, in the wavelength range 400–1100?nm. RESULTS A total of 196 middle–early season and 219 late season apples (Malus domestica Borkh.) cvs ‘Aroma’ and ‘Holsteiner Cox’ samples were used to construct spectral models for SSC and acidity. Partial least squares (PLS), ridge regression (RR) and elastic net (EN) models were used to build prediction models. Furthermore, we compared three sub-sample arrangements for forming training and test sets (‘smooth fractionator’, by date of measurement after harvest and random). Using the ‘smooth fractionator’ sampling method, fewer spectral bands (26) and elastic net resulted in improved performance for SSC models of ‘Aroma’ apples, with a coefficient of variation CVSSC = 13%. The model showed consistently low errors and bias (PLS/EN: R2cal?=?0.60/0.60; SEC = 0.88/0.88°Brix; Biascal?=?0.00/0.00; R2val?=?0.33/0.44; SEP = 1.14/1.03; Biasval?=?0.04/0.03). However, the prediction acidity and for SSC (CV = 5%) of the late cultivar ‘Holsteiner Cox’ produced inferior results as compared with ‘Aroma’. CONCLUSION It was possible to construct local SSC and acidity calibration models for early season apple cultivars with CVs of SSC and acidity around 10%. The overall model performance of these data sets also depend on the proper selection of training and test sets. The ‘smooth fractionator’ protocol provided an objective method for obtaining training and test sets that capture the existing variability of the fruit samples for construction of visible–NIR prediction models. The implication is that by using such ‘efficient’ sampling methods for obtaining an initial sample of fruit that represents the variability of the population and for sub-sampling to form training and test sets it should be possible to use relatively small sample sizes to develop spectral predictions of fruit quality. Using feature selection and elastic net appears to improve the SSC model performance in terms of R2, RMSECV and RMSEP for ‘Aroma’ apples. © 2013 Society of Chemical Industry

  16. A sampling approach for predicting the eating quality of apples using visible-near infrared spectroscopy

    DEFF Research Database (Denmark)

    Martínez Vega, Mabel V.; Sharifzadeh, Sara

    2013-01-01

    BACKGROUND: Visible-near infrared spectroscopy remains a method of increasing interest as a fast alternative for the evaluation of fruit quality. The success of the method is assumed to be achieved by using large sets of samples to produce robust calibration models. In this study we used representative samples of an early and a late season apple cultivar to evaluate model robustness (in terms of prediction ability and error) on the soluble solids content (SSC) and acidity prediction, in the wavelength range 400-1100nm. RESULTS: A total of 196 middle-early season and 219 late season apples (Malus domestica Borkh.) cvs 'Aroma' and 'Holsteiner Cox' samples were used to construct spectral models for SSC and acidity. Partial least squares (PLS), ridge regression (RR) and elastic net (EN) models were used to build prediction models. Furthermore, we compared three sub-sample arrangements for forming training and test sets ('smooth fractionator', by date of measurement after harvest and random). Using the 'smooth fractionator' sampling method, fewer spectral bands (26) and elastic net resulted in improved performance for SSC models of 'Aroma' apples, with a coefficient of variation CVSSC = 13%. The model showed consistently low errors and bias (PLS/EN: R2 cal=0.60/0.60; SEC = 0.88/0.88°Brix; Biascal=0.00/0.00; R2 val=0.33/0.44; SEP = 1.14/1.03; Biasval=0.04/0.03). However, the prediction acidity and for SSC (CV = 5%) of the late cultivar 'Holsteiner Cox' produced inferior results as compared with 'Aroma'. CONCLUSION: It was possible to construct local SSC and acidity calibration models for early season apple cultivars with CVs of SSC and acidity around 10%. The overall model performance of these data sets also depend on the proper selection of training and test sets. The 'smooth fractionator' protocol provided an objective method for obtaining training and test sets that capture the existing variability of the fruit samples for construction of visible-NIR prediction models. The implication is that by using such 'efficient' sampling methods for obtaining an initial sample of fruit that represents the variability of the population and for sub-sampling to form training and test sets it should be possible to use relatively small sample sizes to develop spectral predictions of fruit quality. Using feature selection and elastic net appears to improve the SSC model performance in terms of R2, RMSECV and RMSEP for 'Aroma' apples. © 2013 Society of Chemical Industry.

  17. A sampling approach for predicting the eating quality of apples using visible–near infrared spectroscopy

    DEFF Research Database (Denmark)

    Vega, Mabel V Martínez; Sharifzadeh, Sara

    2013-01-01

    BACKGROUND Visible–near infrared spectroscopy remains a method of increasing interest as a fast alternative for the evaluation of fruit quality. The success of the method is assumed to be achieved by using large sets of samples to produce robust calibration models. In this study we used representative samples of an early and a late season apple cultivar to evaluate model robustness (in terms of prediction ability and error) on the soluble solids content (SSC) and acidity prediction, in the wavelength range 400–1100?nm. RESULTS A total of 196 middle–early season and 219 late season apples (Malus domestica Borkh.) cvs ‘Aroma’ and ‘Holsteiner Cox’ samples were used to construct spectral models for SSC and acidity. Partial least squares (PLS), ridge regression (RR) and elastic net (EN) models were used to build prediction models. Furthermore, we compared three sub-sample arrangements for forming training and test sets (‘smooth fractionator’, by date of measurement after harvest and random). Using the ‘smoothfractionator’ sampling method, fewer spectral bands (26) and elastic net resulted in improved performance for SSC models of ‘Aroma’ apples, with a coefficient of variation CVSSC = 13%. The model showed consistently low errors and bias (PLS/EN: R2cal?=?0.60/0.60; SEC = 0.88/0.88°Brix; Biascal?=?0.00/0.00; R2val?=?0.33/0.44; SEP = 1.14/1.03; Biasval?=?0.04/0.03). However, the prediction acidity and for SSC (CV = 5%) of the late cultivar ‘Holsteiner Cox’ produced inferior results as compared with ‘Aroma’. CONCLUSION It was possible to construct local SSC and acidity calibration models for early season apple cultivars with CVs of SSC and acidity around 10%. The overall model performance of these data sets also depend on the proper selection of training and test sets. The ‘smooth fractionator’ protocol provided an objective method for obtaining training and test sets that capture the existing variability of the fruit samples for construction of visible–NIR prediction models. The implication is that by using such ‘efficient’ sampling methods for obtaining an initial sample of fruit that represents the variability of the population and for sub-sampling to form training and test sets it should be possible to use relatively small sample sizes to develop spectral predictions of fruit quality. Using feature selection and elastic net appears to improve the SSC model performance in terms of R2, RMSECV and RMSEP for ‘Aroma’ apples. © 2013 Society of Chemical Industry

  18. Multijunction organic photovoltaics with a broad spectral response.

    Science.gov (United States)

    Macko, Jill A; Lunt, Richard R; Osedach, Timothy P; Brown, Patrick R; Barr, Miles C; Gleason, Karen K; Bulovic, Vladimir

    2012-11-14

    We demonstrate series-integrated multijunction organic photovoltaics fabricated monolithically by vapor-deposition in a transposed subcell order with the near-infrared-absorbing subcell in front of the green-absorbing subcell. This transposed subcell order is enabled by the highly complementary absorption spectra of a near-infrared-absorbing visibly-transparent subcell and a visible-absorbing subcell and motivated by the non-spatially-uniform optical intensity in nanoscale photovoltaics. The subcell order and thicknesses are optimized via transfer-matrix formalism and short-circuit current simulations. An efficient charge recombination zone consisting of layers of BCP/Ag/MoOx leads to negligible voltage and series-resistance losses. Under 1-sun illumination the multijunction solar cells exhibit a power conversion efficiency of 5.5 ± 0.2% with an FF of 0.685 ± 0.002 and a V(OC) of 1.65 ± 0.02 V, corresponding to the sum of the V(OC) of the component subcells. These devices exhibit a broad spectral response (in the wavelength range of 350 nm to 850 nm) but are limited by subcell external quantum efficiencies between 20% and 30% over the photoactive spectrum. PMID:23014483

  19. Energy-resolved visibility analysis of grating interferometers operated at polychromatic X-ray sources.

    Science.gov (United States)

    Hipp, A; Willner, M; Herzen, J; Auweter, S; Chabior, M; Meiser, J; Achterhold, K; Mohr, J; Pfeiffer, F

    2014-12-15

    Grating interferometry has been successfully adapted at standard X-ray tubes and is a promising candidate for a broad use of phase-contrast imaging in medical diagnostics or industrial testing. The achievable image quality using this technique is mainly dependent on the interferometer performance with the interferometric visibility as crucial parameter. The presented study deals with experimental investigations of the spectral dependence of the visibility in order to understand the interaction between the single contributing energies. Especially for the choice which type of setup has to be preferred using a polychromatic source, this knowledge is highly relevant. Our results affirm previous findings from theoretical investigations but also show that measurements of the spectral contributions to the visibility are necessary to fully characterize and optimize a grating interferometer and cannot be replaced by only relying on simulated data up to now. PMID:25606986

  20. Stellar spectral classification of previously unclassified stars GSC 4461-698 and GSC 4466-870

    Science.gov (United States)

    Grau, Darren Moser

    Stellar spectral classification is one of the first efforts undertaken to begin defining the physical characteristics of stars. However, many stars lack even this basic information, which is the foundation for later research to constrain stellar effective temperatures, masses, radial velocities, the number of stars in the system, and age. This research obtained visible-? stellar spectra via the testing and commissioning of a Santa Barbara Instruments Group (SBIG) Self-Guiding Spectrograph (SGS) at the UND Observatory. Utilizing a 16-inch-aperture telescope on Internet Observatory #3, the SGS obtained spectra of GSC 4461-698 and GSC 4466-870 in the low-resolution mode using an 18-µm wide slit with dispersion of 4.3 Å/pixel, resolution of 8 Å, and a spectral range from 3800-7500 Å. Observational protocols include automatic bias/dark frame subtraction for each stellar spectrum obtained. This was followed by spectral averaging to obtain a combined spectrum for each star observed. Image calibration and spectral averaging was performed using the software programs, Maxim DL, Image J, Microsoft Excel, and Winmk. A wavelength calibration process was used to obtain spectra of an Hg/Ne source that allowed the conversion of spectrograph channels into wavelengths. Stellar emission and absorption lines, such as those for hydrogen (H) and helium (He), were identified, extracted, and rectified. Each average spectrum was compared to the MK stellar spectral standards to determine an initial spectral classification for each star. The hope is that successful completion of this project will allow long-term stellar spectral observations to begin at the UND Observatory.

  1. Superconducting nanowire single-photon detectors (SNSPDs) on SOI for near-infrared range

    International Nuclear Information System (INIS)

    Superconducting nanowire single-photon detectors are promising devices for photon detectors with high count rates, low dark count rates and low dead times. At wavelengths beyond the visible range, the detection efficiency of today's SNSPDs drops significantly. Moreover, the low absorption in ultra-thin detector films is a limiting factor over the entire spectral range. Solving this problem requires approaches for an enhancement of the absorption range in feeding the light to the detector element. A possibility to obtain a better absorption is the use of multilayer substrate materials for photonic waveguide structures. We present results on development of superconducting nanowire single-photon detectors made from niobium nitride on silicon-on-insulator (SOI) multilayer substrates. Optical and superconducting properties of SNSPDs on SOI will be discussed and compared with the characteristics of detectors on common substrates.

  2. Spectral indices in quantitative spectral classification from stellar libraries

    Science.gov (United States)

    Malyuto, V.; Schmidt-Kaler, Th.

    With the use of modern detectors stellar spectral classification libraries have been extended from the photographic regime to the near IR at 11 000 Angstroms. We have defined new spectral indices within this extended wavelength-range that can be used to determine the luminosity classification for G-K-M stars. An advantage of the new indices, which sample the stellar flux in and out of selected spectral features, is that they are insensitive to catalog differences. This facilitates the use of many catalogs, with varying resolution, different reddening corrections, and calibrations, hence extending the total number of stellar standards available. Furthermore, we demonstrate that the indices can be used to infer absolute magnitudes with good accuracy. The indices should prove useful for analysis of spectra from distant clusters, galaxies, and in particular for problems involving spectral synthesis of stellar populations of galaxies.

  3. Ultraviolet and visible photometry of asteroid (21) Lutetia using the Hubble Space Telescope

    CERN Document Server

    Weaver, H A; Merline, W J; Mutchler, M J; A'Hearn, M F; Bertaux, J -L; Feaga, L M; Parker, J W; Slater, D C; Steffl, A J; Drummond, J D; Stern, S A

    2009-01-01

    The asteroid (21) Lutetia is the target of a planned close encounter by the Rosetta spacecraft in July 2010. To prepare for that flyby, Lutetia has been extensively observed by a variety of astronomical facilities. We used the Hubble Space Telescope (HST) to determine the albedo of Lutetia over a wide wavelength range, extending from ~150 nm to ~700 nm. Using data from a variety of HST filters and a ground-based visible light spectrum, we employed synthetic photometry techniques to derive absolute fluxes for Lutetia. New results from ground-based measurements of Lutetia's size and shape were used to convert the absolute fluxes into albedos. We present our best model for the spectral energy distribution of Lutetia over the wavelength range 120-800 nm. There appears to be a steep drop in the albedo (by a factor of ~2) for wavelengths shorter than ~300 nm. Nevertheless, the far ultraviolet albedo of Lutetia (~10%) is considerably larger than that of typical C-chondrite material (~4%). Lutetia's reflectivity is n...

  4. Spectral Classification Using Restricted Boltzmann Machine

    OpenAIRE

    Chen, Fuqiang; Wu, Yan; Bu, Yude; Zhao, Guodong

    2013-01-01

    In this study, a novel machine learning algorithm, restricted Boltzmann machine (RBM), is introduced. The algorithm is applied for the spectral classification in astronomy. RBM is a bipartite generative graphical model with two separate layers (one visible layer and one hidden layer), which can extract higher level features to represent the original data. Despite generative, RBM can be used for classification when modified with a free energy and a soft-max function. Before s...

  5. Fiber-integrated second harmonic generation modules for visible and near-visible picosecond pulse generation

    Science.gov (United States)

    Legg, Thomas; Robertson, Andrew; Eckardt, Robert; Runcorn, Timothy; Hu, Dora; Murray, Robert; Kelleher, Edmund; Popov, Sergei; Taylor, James

    2015-02-01

    Second harmonic generation (SHG) is a ubiquitous technique for extending the spectral coverage of laser sources into regions that would otherwise be technologically challenging to access. SHG schemes typically rely on the use of bulk optical components, resulting in systems with large footprints requiring precise optical alignment. Integration of the SHG components into a single unit facilitates the implementation of compact, robust and turn-key sources, suitable for applications in biophotonic imaging, amongst others. We report on the development of fiber-coupled frequency doubling modules and their application to novel fiberintegrated picosecond pulse sources in the visible and near-visible. The modules employ a simple, single-pass configuration using a periodically-poled lithium niobate (PPLN) crystal as the nonlinear conversion medium. They are readily adaptable for different fiber pump laser configurations and are configurable with either fiber-coupled or collimated free-space outputs. Two sources using the modules are presented, operating at 780 nm and 560 nm. The 780 nm source utilizes an erbium master oscillator power fiber amplifier (MOPFA) scheme. SHG was performed in a 35 mm long crystal, generating 3.5 W of 780 nm radiation with a pulse duration of 410 ps at 50 MHz and conversion efficiencies exceeding 20%. Results of this source being used for parametric wavelength conversion in photonic crystal fiber are discussed. The 560 nm source was based on SHG of a Raman amplified CW diode pumped by a pulsed ytterbium-fiber MOPFA. This source generated 450 mW of average power with conversion efficiencies greater than 20%.

  6. A visibility and total suspended dust relationship

    Science.gov (United States)

    Baddock, M. C.; Strong, C. L.; Leys, J. F.; Heidenreich, S. K.; Tews, E. K.; McTainsh, G. H.

    2014-06-01

    This study reports findings on observed visibility reductions and associated concentrations of mineral dust from a detailed Australian case study. An understanding of the relationship between visibility and dust concentration is of considerable utility for wind erosion and aeolian dust research because it allows visibility data, which are available from thousands of weather observation stations worldwide, to be converted into dust concentrations. Until now, this application of visibility data for wind erosion/dust studies has been constrained by the scarcity of direct measurements of co-incident dust concentration and visibility measurements. While dust concentrations are available from high volume air samplers, these time-averaged data cannot be directly correlated with instantaneous visibility records from meteorological observations. This study presents a new method for deriving instantaneous values of total suspended dust from time averaged (filter-based) samples, through reference to high resolution PM10 data. The development and testing of the model is presented here as well as a discussion of the derived expression in relation to other visibility-dust concentration predictive curves. The current study is significant because the visibility-dust concentration relationship produced is based on visibility observations made 10-100 km from the dust sources. This distance from source makes the derived relationship appropriate for a greater number of visibility recording stations than widely-used previous relationships based on observations made directly at eroding sources. Testing of the new formula performance against observed total suspended dust concentrations demonstrates that the model predicts dust concentration relatively well (r2 = 0.6) from visibility. When considered alongside previous studies, the new relationship fits into the continuum of visibility-dust concentration outcomes existing for increasing distance-from-source. This highlights the important influence that distance to source has on the visibility-dust concentration relationship.

  7. A Femtosecond Visible/Visible and Visible/Mid-Infrared Transient Absorption Study of the Light Harvesting Complex II

    OpenAIRE

    Stahl, Andreas D.; Di Donato, Mariangela; van Stokkum, Ivo; Grondelle, Rienk van; Groot, Marie Louise

    2009-01-01

    Light harvesting complex II (LHCII) is the most abundant protein in the thylakoid membrane of higher plants and green algae. LHCII acts to collect solar radiation, transferring this energy mainly toward photosystem II, with a smaller amount going to photosystem I; it is then converted into a chemical, storable form. We performed time-resolved femtosecond visible pump/mid-infrared probe and visible pump/visible probe absorption difference spectroscopy on purified LHCII to gain insight into the...

  8. Visible and near-infrared reflectance spectra of thermally processed synthetic sulfides as a potential analog for the hollow forming materials on Mercury

    Science.gov (United States)

    Helbert, Jörn; Maturilli, Alessandro; D'Amore, Mario

    2013-05-01

    We have obtained reflectance spectra in the visible spectral range of magnesium, calcium and manganese sulfides before and after thermal processing at Mercury dayside temperatures in vacuum conditions. All measurements were made at the Planetary Emissivity Laboratory (PEL) at DLR. These experiments are motivated by the recent findings of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission of hollows on Mercury and the notion that sulfides might be a candidate material for their formation. From these new measurements, we infer that all sulfides studied here display a diagnostic feature at or near 0.6 ?m. The spectral contrast of this diagnostic feature can be strongly affected by heating of the samples to Mercury daytime temperatures of approximately 500 °C in a vacuum environment. Both the spectral slope and the color observed before and after thermal processing showed significant changes. The laboratory work also indicates that sulfides can be thermally decomposed at temperature below 500 °C, well below their melting point. Our results are consistent with models explaining hollows on Mercury's surface by the thermal decomposition of sulfides.

  9. 46 CFR 112.45-1 - Visible indicators.

    Science.gov (United States)

    2010-10-01

    ...2010-10-01 2010-10-01 false Visible indicators. 112.45-1 Section 112.45-1...EMERGENCY LIGHTING AND POWER SYSTEMS Visible Indicators § 112.45-1 Visible indicators. There must be visible indicators...

  10. New observation strategies for the solar UV spectral irradiance

    Directory of Open Access Journals (Sweden)

    Kretzschmar Matthieu

    2012-09-01

    Full Text Available Many applications in space weather and in space situational awareness require continuous solar spectral irradiance measurements in the UV, and to a lesser degree in the visible band. Most space-borne solar radiometers are made out of two different parts: (i a front filter that selects the passband and (ii a detector that is usually based on silicon technology. Both are prone to degradation, which may be caused either by the degradation of the filter coating due to local deposition or to structural changes, or by the degradation of the silicon detector by solar radiative and energetic particle fluxes. In this study, we provide a theoretical analysis of the filter degradation that is caused by structural changes such as pinholes; contamination-induced degradation will not be considered. We then propose a new instrumental concept, which is expected to overcome, at least partially, these problems. We show how most of the solar UV spectrum can be reconstructed from the measurement of only five spectral bands. This instrumental concept outperforms present spectrometers in terms of degradation. This new concept in addition overcomes the need for silicon-based detectors, which are replaced by wide band gap material detectors. Front filters, which can contribute to in-flight degradation, therefore are not required, except for the extreme-UV (EUV range. With a small weight and a low telemetry, this concept may also have applications in solar physics, in astrophysics and in planetology.

  11. Spectral Characteristics of Magnetic Field Emergence in the Photosphere

    Science.gov (United States)

    Chen, James; Rasca, Anthony P.

    2015-04-01

    The photosphere is the innermost visible layer of the solar atmosphere, where the medium makes a transition from an optically thick to optically thin state. All forms of solar energy ultimately must traverse the photosphere from the solar interior. An important component of the energy budget is the magnetic energy, which is presumed to be generated deep in the convection zone by the solar dynamo. Recent high-resolution observations have revealed that the emergence of active regions is manifested as the rapid appearance of small bipolar magnetic features. It is expected that future observations with higher spatial and temporal resolution will show magnetic features on smaller spatial and faster temporal scales that are currently unresolved. It is therefore important to establish the quantitative relationship between the magnetic energy flux through the surface and observational data directly accessible by remote-sensing techniques. In order to achieve this, we construct a generic model in which an ensemble of magnetic flux ropes is prescribed to rise through the photosphere. The ensemble consists of flux ropes on a range of scales extending to sub-pixel levels, and potentially observable spectral properties are related to the magnetic energy flux of the ensemble. The model is applied to photospheric absorption lines, and the magnetic energy flux implied by the data (e.g., SOLIS data) is calculated using a statistical method based on the pixel fluctuations in the spectral data (Stokes parameters) (Rasca et al. 2015).Rasca, A., Chen, J., and Pevtsov, A., this meeting, 2015.

  12. Visible/near-infrared spectra of experimentally shocked plagioclase feldspars

    Science.gov (United States)

    Johnson, J.R.; Horz, F.

    2003-01-01

    High shock pressures cause structural changes in plagioclase feldspars such as mechanical fracturing and disaggregation of the crystal lattice at submicron scales, the formation of diaplectic glass (maskelynite), and genuine melting. Past studies of visible/ near-infrared spectra of shocked feldspars demonstrated few spectral variations with pressure except for a decrease in the depth of the absorption feature near 1250-1300 nm and an overall decrease in reflectance. New visible/near-infrared spectra (400-2500 nm) of experimentally shocked (17-56 GPa) albite- and anorthite-rich rock powders demonstrate similar trends, including the loss of minor hydrated mineral bands near 1410, 1930, 2250, and 2350 nm. However, the most interesting new observations are increases in reflectance at intermediate pressures, followed by subsequent decreases in reflectance at higher pressures. The amount of internal scattering and overall sample reflectance is controlled by the relative proportions of micro-fractures, submicron grains, diaplectic glass, and melts formed during shock metamorphism. We interpret the observed reflectance increases at intermediate pressures to result from progressively larger proportions of submicron feldspar grains and diaplectic glass. The ensuing decreases in reflectance occur after diaplectic glass formation is complete and the proportion of genuine melt inclusions increases. The pressure regimes over which these reflectance variations occur differ between albite and anorthite, consistent with thermal infrared spectra of these samples and previous studies of shocked feldspars. These types of spectral variations associated with different peak shock pressures should be considered during interpretation and modeling of visible/near-infrared remotely sensed spectra of planetary and asteroidal surfaces.

  13. Lazy visibility evaluation for exact soft shadows

    OpenAIRE

    Mora, Frédéric; Aveneau, Lilian; Apostu, Oana Livia; Ghazanfarpour, Djamchid

    2013-01-01

    This report presents a novel approach to compute high quality and alias-free soft shadows using exact visibility computations. This work relies on a theoritical framework allowing to group lines according to the geometry they intersect. From this study, we derive a new algorithm encoding lazily the visibility from a polygon. Contrary to previous works on from-polygon visibility, our approach is very robust and straightforward to implement. We apply this algorithm to solve exactly and efficien...

  14. Visible spectrophotometric methods for estimation of repaglinide in tablet formulation

    OpenAIRE

    Goyal Anju; Singhvi I

    2006-01-01

    Two simple, economical, precise and reproducible visible spectrophotometric methods have been developed for the estimation of repaglinide in tablet formulation. The developed methods are based on the formation of chloroform extractable complex of repaglinide with zincon and methylthymol blue in acidic medium. The extracted complex with zincon shows absorbance maxima at 533.0 nm and linearity in the concentration range of 50-250 µg/ml. The extracted complex with methylthymol blue shows ...

  15. Reflection beamshifts of visible light due to graphene

    CERN Document Server

    Hermosa, N

    2015-01-01

    I present theoretical calculations of reflection beamshifts, Goos-H\\"anchen and Imbert-Fedorov shifts, due to the presence of a monolayer graphene on a dielectric media when using a beam with wavelength in the visible range. Specifically, I look at beamshifts for different polarization states (p, s, $45^0$, $\\sigma^+$). The Goos-H\\"anchen shifts I calculated are in good agreement with results of a recent experiment. I will discuss other possible experimental routes to determine beamshifts in graphene.

  16. Visible array waveguide gratings for applications of optical neural probes

    Science.gov (United States)

    Segev, Eran; Fowler, Trevor; Faraon, Andrei; Roukes, Michael L.

    2015-03-01

    In this paper we propose using Array Waveguide Gratings (AWGs), working in the visible range, in order to implement the technique of Wavelength-Division-(de)Multiplexing for multi-point stimulation of deep-brain neurons. We've developed a CMOS compatible fabrication process and fabricated two sets of AWGs, working in the red and blue wavelengths. Experimental data demonstrating the functionality of these AWGs is presented.

  17. Spectral Reflectance Response of Three Turfgrasses to Leaf Dehydration

    OpenAIRE

    Qian, Y. L.; Alshammary, S. F.; Suplick-ploense, M. R.

    2011-01-01

    Spectral reflectance assessment of turfgrass canopies is likely to enhance our ability to refine irrigation management technology. Reliable spectral detection of water stress is dependent upon knowledge of wavelengths most sensitive to leaf water content. The purposes of this study were (1) to determine wavelengths at which turfgrass canopy reflectance is most sensitive to progressive dehydration in the visible and near infrared portions of the spectrum and (2) to investigate whether differen...

  18. DAVINCI: Dilute Aperture VIsible Nulling Coronagraphic Imager

    Science.gov (United States)

    Shao, Michael; Levine, B. M.; Vasisht, G.; Lane, B. F.; Woodruff, R.; Vasudevan, G.; Samuele, R.; Lloyd, C. A.; Clampin, M.; Lyon, R.; Guyon, O.

    2008-01-01

    This slide presentation gives an overview of DAVINCI (Dilute Aperture VIsible Nulling Coronagraphic Imager). The presentation also includes information about dilute aperture coronagraph, and lyot efficiency.

  19. Convex domains and K-spectral sets

    OpenAIRE

    Badea, Catalin; Crouzeix, Michel; Delyon, Bernard

    2005-01-01

    Let $\\Omega$ be an open convex domain of the complex plane. We study constants K such that $\\Omega$ is K-spectral or complete K-spectral for each continuous linear Hilbert space operator with numerical range included in $\\Omega$. Several approaches are discussed.

  20. Spectral concentration in the nonrelativistic limit

    International Nuclear Information System (INIS)

    First order relativistic corrections to the Schroedinger operator according to Foldy and Wouthuysen are rigorously discussed in the framework of singular perturbation theory. For Coulomb plus short-range interactions we investigate the corresponding spectral properties and prove spectral concentration and existence of first order pseudoeigenvalues in the nonrelativistic limit. (Author)

  1. Hyperspectral visible-near infrared imaging for the detection of waxed rice

    Science.gov (United States)

    Zhao, Mantong

    2014-11-01

    Presently, unscrupulous traders in the market use the industrial wax to wax the rice. The industrial wax is a particularly hazardous substance. Visible-near infrared hyperspectral images (400-1,000 nm) can be used for the detection of the waxed rice and the non-waxed rice. This study was carried out to find effective testing methods based on the visible-near infrared imaging spectrometry to detect whether the rice was waxed or not. An imaging spectroscopy system was assembled to acquire hyperspectral images from 80 grains of waxed rice and 80 grains of non-waxed rice over visible and near infrared spectral region. Spectra of 100 grains of rice were analyzed by principal component analysis (PCA) to extract the information of hyperspectral images. PCA provides an effective compressed representation of the spectral signal of each pixel in the spectral domain. We used PCA to acquire the effective wavelengths from the spectra. Based on the effective wavelengths, the predict models were set up by using partial least squares (PLS) analysis and linear discriminant analysis (LDA). Also, compared with the PLS of 80% for the waxed rice and 86.7% for the non-waxed rice detection rate, LDA gives 93.3% and 96.7% detection rate. The results demonstrated that the LDA could detect the waxed rice better, while illustrating the hyperspectral imaging technique with the visible-near infrared region could be a reliable method for the waxed rice detection.

  2. Visible light and ultraviolet observations of coronal structures: physical properties of an equatorial streamer and modelling of the F corona

    Science.gov (United States)

    Dolei, S.; Spadaro, D.; Ventura, R.

    2015-05-01

    The present work studies the characteristics of an equatorial streamer visible above the east limb of the Sun on March 2008, during the most recent minimum of solar activity. We analysed the visible light coronagraphic images of SOHO/LASCO and the ultraviolet observations in the H I Ly? spectral line obtained by SOHO/UVCS, and exploited the Doppler dimming effect of the coronal Ly? line to derive the outflow velocity profile of the scattering neutral hydrogen atoms in the streamer region. Taking advantage of the synergy between visible light and ultraviolet observations, we were able to determine all the properties of the coronal structure. In particular, the actual extent of the streamer along the line of sight has been evaluated for the first time. In so doing, the solar wind outflow velocity turned out to be the only free parameter in the theoretical modelling of the Ly? intensity. We found nearly static conditions below 3.5 R? along the streamer axis, whereas the solar wind flows at velocities from 40 km s-1 to 140 km s-1 in the altitude range 2.5-5.0 R? along the southern boundary of the streamer. We also derived the intensity distribution of the F coronal component in the LASCO C2 field of view, by combining total and polarized brightness data. Finally, we investigated the dependence of the Ly? resonant scattering process on the kinetic temperature of the coronal neutral hydrogen atoms and found that the value of this temperature mostly affects the scattering process at low heliocentric distances, where the solar wind flows with low velocity.

  3. Online Evaluation of Yellow Peach Quality by Visible and Near-Infrared Spectroscopy

    Directory of Open Access Journals (Sweden)

    Ligang Fang

    2013-05-01

    Full Text Available To evaluate the possibility of using visible and near-infrared spectroscopy for the determination of SSC, TSC, TAC and water content in yellow peach, 60 yellow peaches with different maturity were hand-harvested from an orchard in Suzhou city, China and spectral measurements were done with an ASD FieldSpec 3 Portable Spectroradiometer (The wavelengths range of 350-2500 nm, on 17 August 2011. In this study, the contents of internal quality with different maturity differ greatly; Total Sugar Content (TSC is 3.828-26.37%, Total Acid Content (TAC is 0.383-0.961%, Soluble Solids Content (SSC is 9.1-12.9° Brix and water content is 81.211-90.752%. We analyzed the correlation between TSC, TAC, SSC and water content and the two indices of spectral data. These were the reciprocal-logarithm-transformed reflectance (log (1/R and the first-order derivative of reciprocal-logarithm-transformed reflectance (dlog (1/R. The results showed that the spectra of yellow peach had common spectral characteristics and the pattern of the absorption curves was similar to that for other fruits. The first-order derivative of reciprocal-logarithm-transformed reflectance (dlog (1/R showed stronger correlation for some wavelengths. These wavelengths with stronger correlation were selected for the sensitive wavelengths and were used for the model calibration based on Multiple Linear Regression (MLR. TSC, TAC, SSC and water content of yellow peach were predicted at each sampling point using the multiple line models. Overall, although the TAC determination still needs to be improved, the determination of TSC, SSC and water content in yellow peach fruits by ASD near-infrared spectral analysis (350-2500 nm was still successful (R2>0.61 and the corresponding RMSEs of 2.32, 0.44 and 0.85%, respectively, showing that the spectroscopy has the ability to rapidly and non-destructively determine the internal quality of yellow peach.

  4. Visible photocatalytic properties of vanadium doped zinc oxide aerogel nanopowder

    International Nuclear Information System (INIS)

    Vanadium-doped zinc oxide nanoparticles have been synthesized by sol-gel method. In our approach the water for hydrolysis used in the synthesis of nanopowder was slowly released followed by a thermal drying in ethyl alcohol at 250 deg. C. The obtained nanopowder was characterized by various techniques such as particle size analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and photoluminescence (PL). In the as-prepared state, the powder with an average particle size of 25 nm presents a strong luminescence band in the visible range. From photoluminescence excitation (PLE) the energy position of the obtained PL band depends on the excitation wavelength and this PL band can be also observed under visible excitations. This result is very promising for visible photo catalysis applications, which was confirmed by methylene blue photo-degradation using visible lamp as a light source. - Research Highlights: ? We explore the impact of plot size on estimation of a small watershed outputs. ? Different lengths and fixed width plots were installed on two slope aspects. ? The performance of two similar sets of experimental plots was examined. ? The optimal lengths for estimation of sediment and runoff were finally found.

  5. Multicolor, visible-light nanolithography

    Science.gov (United States)

    Fourkas, John T.; Tomova, Zuleykhan

    2015-03-01

    Traditional approaches to improving photolithographic resolution rely on using shorter and shorter wavelengths of electromagnetic radiation. This approach faces ever greater challenges each time the operating wavelength is decreased. Recently, alternative approaches to nanoscale photolithography have been introduced that employ photoresists that are sensitive to multiple colors of visible light. One or more colors of light activate the photoresist, and one or more colors of light can subsequently deactivate it. By controlling the spatial patterns of the colors, it is possible to create features with sizes that are far below the diffraction limit. This approach has been demonstrated for laboratory-based fabrication using multiphoton-absorption-based fabrication, but with improvements in materials it shows great promise for semiconductor lithography as well. A number of approaches to two-color photolithography have been demonstrated. A next generation of schemes that involve a third color of light has the potential to improve the performance of multicolor lithography substantially. The basic premises of both two-color and three-color lithography are discussed, and experimental examples of each type of approach are presented.

  6. A database for spectral image quality

    Science.gov (United States)

    Le Moan, Steven; George, Sony; Pedersen, Marius; Blahová, Jana; Hardeberg, Jon Yngve

    2015-01-01

    We introduce a new image database dedicated to multi-/hyperspectral image quality assessment. A total of nine scenes representing pseudo-at surfaces of different materials (textile, wood, skin. . . ) were captured by means of a 160 band hyperspectral system with a spectral range between 410 and 1000nm. Five spectral distortions were designed, applied to the spectral images and subsequently compared in a psychometric experiment, in order to provide a basis for applications such as the evaluation of spectral image difference measures. The database can be downloaded freely from http://www.colourlab.no/cid.

  7. Spectral solar radiation data base documentation

    Energy Technology Data Exchange (ETDEWEB)

    Riordan, C.J.; Myers, D.R.; Hulstrom, R.L.

    1990-01-01

    The Solar Energy Research Institute (SERI), Electric Power Research Institute, Florida Solar Energy Center, and Pacific Gas and Electric Company cooperated to produce a spectral solar radiation data base representing a range of atmospheric conditions. These data will help to characterize the neutral variability in the spectral (color) content to outdoor solar radiation so that the sensitivity of spectrally selective solar devices (such as photovoltaics) to these variations can be studied quantitatively. Volume 1 of this report documents the history, approach, content, and format of the data base; Volume 2 contains graphs and field notes for each of the spectral data sets. The data reside on magnetic tape at SERI.

  8. Long baseline interferometry in the visible: the FRIEND project

    Science.gov (United States)

    Berio, P.; Bresson, Y.; Clausse, J. M.; Mourard, D.; Dejonghe, J.; Duthu, A.; Lagarde, S.; Meilland, A.; Perraut, K.; Tallon-Bosc, Isabelle; Nardetto, N.; Spang, A.; Bailet, C.; Marcotto, A.; Chesneau, O.; Stee, P.; Feautrier, P.; Balard, P.; Gach, J. L.

    2014-07-01

    In the next 2 or 3 years, the two major interferometric arrays, VLTI and CHARA, will equip their telescopes of 1.8m and 1m respectively with Adaptive Optics (AO hereafter) systems. This improvement will permit to apply with a reasonable e_ciency in the visible domain, the principle of spatial filtering with single mode fibers demonstrated in the near-infrared. It will clearly open new astrophysical fields by taking benefit of an improved sensitivity and state-of-the-art precision and accuracy on interferometric observables. To prepare this future possibility, we started the development of a demonstrator called FRIEND (Fibered and spectrally Resolved Interferometric Experiment - New Design). FRIEND combines the beams coming from 3 telescopes after injection in single mode optical fibers and provides some spectral capabilities for characterization purposes as well as photometric channels. It operates in the R spectral band (from 600nm to 750nm) and uses the world's fastest and more sensitive analogic detector OCAM2. Tests on sky at the focus of the CHARA interferometer are scheduled for December 2014. In this paper, we present the first interferometric tests of the OCAM2 detector performed on CHARA in November 2012 and the concept, the expected performance and the opto-mechanical design of FRIEND.

  9. Rendering Visible: Painting and Sexuate Subjectivity

    Science.gov (United States)

    Daley, Linda

    2015-01-01

    In this essay, I examine Luce Irigaray's aesthetic of sexual difference, which she develops by extrapolating from Paul Klee's idea that the role of painting is to render the non-visible rather than represent the visible. This idea is the premise of her analyses of phenomenology and psychoanalysis and their respective contributions to understanding…

  10. The challenge of improving visibility in Beijing

    Science.gov (United States)

    Zhang, Q. H.; Zhang, J. P.; Xue, H. W.

    2010-08-01

    The "Blue Sky Project" was proposed in 1998 to investigate by how much emissions should be reduced to increase blue sky frequency in Beijing, which hosted the Summer Olympics in 2008. This paper focuses on the temporal variation of visibility and its dependence on meteorological conditions and suspended particles at Beijing using the hourly observed visibility data at Beijing Capital International Airport (BCIA) from 1999 to 2007. It has been found that about 47.8% (24.2%) of the hours in Beijing are "bad" ("good") hours with visibility below 10 km (equal or higher than 20 km) between 1999 and 2007. Due to the high Relative Humidity (RH), summer is the season with the lowest mean visibility in a year. Although PM10 index was reported in a decreasing trend (Chan and Yao, 2008), the increase of RH has resulted in a decreasing trend of visibility over BCIA in the summer from 1999 to 2007. To ensure blue sky ("good" visibility) for Olympics 2008, daily mean PM10 index should have been reduced from 81 to 44. This requires that not only vehicle emissions, but also other emissions should be limited. Observations verify that blue-sky-hour rate increased significantly after mean PM10 index was reduced to 53 during Olympics 2008, however, the visibility of 2009 returned to the mean level from 1999 to 2007 during the period 8-24 August. RH (aerosol) contribute 24% (76%) of the improvement of visibility during August 2008.

  11. Impaired visibility: the air pollution people see

    Science.gov (United States)

    Hyslop, Nicole Pauly

    Almost every home and office contains a portrayal of a scenic landscape whether on a calendar, postcard, photograph, or painting. The most sought after locations boast a scenic landscape right outside their window. No matter what the scene - mountains, skyscrapers, clouds, or pastureland - clarity and vividness are essential to the image. Air pollution can degrade scenic vistas, and in extreme cases, completely obscure them. Particulate matter suspended in the air is the main cause of visibility degradation. Particulate matter affects visibility in multiple ways: obscures distant objects, drains the contrast from a scene, and discolors the sky. Visibility is an environmental quality that is valued for aesthetic reasons that are difficult to express or quantify. Human psychology and physiology are sensitive to visual input. Visibility has been monitored throughout the world but there are few places where it is a protected resource. Existing health-based regulations are weak in terms of visibility protection. Various techniques, including human observation, light transmission measurements, digital photography, and satellite imaging, are used to monitor visibility. As with air pollution, trends in visibility vary spatially and temporally. Emissions from the developing world and large scale events such as dust storms and wildfires affect visibility around much of the globe.

  12. Quiet Sun magnetic fields from simultaneous inversions of visible and infrared spectropolarimetric observations

    CERN Document Server

    Cerdena, I D; Kneer, F; Almeida, Jorge Sanchez; Cerdena, Itahiza Dominguez; Kneer, Franz

    2006-01-01

    We study the quiet Sun magnetic fields using spectropolarimetric observations of the infrared and visible Fe I lines at 6301.5, 6302.5, 15648 and 15653 A. Magnetic field strengths and filling factors are inferred by the simultaneous fit of the observed Stokes profiles under the MISMA hypothesis. The observations cover an intra-network region at the solar disk center. We analyze 2280 Stokes profiles whose polarization signals are above noise in the two spectral ranges, which correspond to 40% of the field of view. Most of these profiles can be reproduced only with a model atmosphere including 3 magnetic components with very different field strengths, which indicates the co-existence of kG and sub-kG fields in our 1.5" resolution elements. We measure an unsigned magnetic flux density of 9.6 G considering the full field of view. Half of the pixels present magnetic fields with mixed polarities in the resolution element. The fraction of mixed polarities increases as the polarization weakens. We compute the probabi...

  13. Non-destructive detection of pesticide residues in cucumber using visible/near-infrared spectroscopy.

    Science.gov (United States)

    Jamshidi, Bahareh; Mohajerani, Ezeddin; Jamshidi, Jamshid; Minaei, Saeid; Sharifi, Ahmad

    2015-06-01

    The feasibility of using visible/near-infrared (Vis/NIR) spectroscopy was assessed for non-destructive detection of diazinon residues in intact cucumbers. Vis/NIR spectra of diazinon solution and cucumber samples without and with different concentrations of diazinon residue were analysed at the range of 450-1000 nm. Partial least squares-discriminant analysis (PLS-DA) models were developed based on different spectral pre-processing techniques to classify cucumbers with contents of diazinon below and above the MRL as safe and unsafe samples, respectively. The best model was obtained using a first-derivative method with the lowest standard error of cross-validation (SECV = 0.366). Moreover, total percentages of correctly classified samples in calibration and prediction sets were 97.5% and 92.31%, respectively. It was concluded that Vis/NIR spectroscopy could be an appropriate, fast and non-destructive technology for safety control of intact cucumbers by the absence/presence of diazinon residues. PMID:25789964

  14. Structure in the visible absorption bands of jet-cooled phenylperoxy radicals.

    Science.gov (United States)

    Freel, Keith A; Sullivan, Michael N; Park, J; Lin, M C; Heaven, Michael C

    2013-08-15

    The visible absorption bands of the phenylperoxy radical in the gas phase have been investigated using cavity ring-down spectroscopy. Jet-cooling was used to reduce the spectral congestion. Structured spectra spanning the range from 17,500 to 19,000 cm(-1) are reported for the first time. Analyses of these data have been guided by the results from time-dependent density functional calculations. The observed spectrum was found to be dominated by the bands of the B?(2)A?-X?(2)A? transition. An analysis of the rotational contour for the origin band yielded a homogeneous line width of 2.2 cm(-1), corresponding to a decay rate of 4.1 × 10(11) s(-1). The results provide a rationale for the lack of structure in room temperature spectra that have been previously attributed to phenylperoxy. They also indicate that the lower energy region of the spectrum may show resolvable structure at room temperature. If so, this would provide a more definitive signature for monitoring phenylperoxy in kinetic measurements. PMID:23590572

  15. Optimization of the visible CXRS measurements of TESPEL diagnostics in LHD

    International Nuclear Information System (INIS)

    A model for calculations of Charge eXchange Recombination (CXR) signals of impurity nuclei injected in high temperature plasma has been developed. For that purpose, the simplified collisional-radiative model for calculations of CXR signal and the corona equilibrium set of equations for ionization balance were solved taking into account the main physical processes involved. Scaling laws of partial CX cross sections with respect to both principal and angular quantum numbers of captured electron have been established on the basis of the results of Classical Trajectory Monte Carlo (CTMC) calculations. The CXR signals for a Li tracer in TESPEL experiments on LHD and CHS machines have been calculated. The difference of about two orders of magnitude in the calculated signals is due to the difference of both NBI neutral flux density and capture-radiation cross-sections and explains the lack of Li3+ CXR signals in the measurements on LHD. Calculations of the CXR signals for various injected impurities have been performed for LHD conditions. The operational limits of the use of TESPEL diagnostics in the visible spectral range on LHD have been determined. For Te=1-2 keV (PNBI=3 MW) and Ne=(2-5) x 1013 cm-3, injection of F, Mg and Al as tracer materials is proposed. (author)

  16. Numerical study of extinction of visible and infrared radiation transformed by preferentially oriented plate crystals

    International Nuclear Information System (INIS)

    Extinction properties of an ensemble of semi-transparent plate crystals in preferred orientation are studied at wavelengths of visible and infrared ranges using the physical optics method. The work illustrates some calculations of the differential scattering coefficient in the near-forward and the exact forward directions. The features of energy and polarization characteristics of directly transmitted radiation through a set of particles are discussed, as depended on parameters of medium and the incident radiation. It is shown that the effect of polarization on extinction by large plates at certain combination of microphysical parameters of medium and the wavelength can be pronounced even for clean ice. By increasing the real part of complex refractive index, the polarized effect can be increased a few times. It is illustrated as an influence of flutter of plates on the considered characteristics. -- Highlights: ? At coherent sum of diffracted and refracted fields, physical optics method is used. ? Pronounced spectral behavior of extinction of optical radiation is analyzed. ? Polarized features of extinction are investigated for set of oriented plates. ? Peculiarities of scattering near the forward direction are shown

  17. Visible spectrophotometric methods for estimation of repaglinide in tablet formulation

    Directory of Open Access Journals (Sweden)

    Goyal Anju

    2006-01-01

    Full Text Available Two simple, economical, precise and reproducible visible spectrophotometric methods have been developed for the estimation of repaglinide in tablet formulation. The developed methods are based on the formation of chloroform extractable complex of repaglinide with zincon and methylthymol blue in acidic medium. The extracted complex with zincon shows absorbance maxima at 533.0 nm and linearity in the concentration range of 50-250 µg/ml. The extracted complex with methylthymol blue shows absorbance maxima at 427.0 nm and linearity in the concentration range of 100-500 µg/ml. Results of analysis for both the methods were validated statistically and by recovery studies.

  18. New nonlinear laser effects in ?-quartz: generation of a two-octave Stokes and anti-Stokes comb and cascaded lasing in the spectral range of the second and third harmonics

    International Nuclear Information System (INIS)

    Crystals that are simultaneously ?(2)- and ?(3)-active offer a wide range of possibilities for the generation of new coherent wavelengths of light. Frequency conversion processes such as stimulated Raman scattering, second and third harmonic generation, or parametric sum and difference frequency mixing can be combined effectively in the same noncentrosymmetric crystal in cascaded ?(3) ? ?(2) lasing processes. We present several new manifestations of these effects under picosecond laser excitation in ?-quartz (SiO2), the oldest nonlinear-laser crystal. Among them are 45 Stokes and anti-Stokes wavelength comb generation of more than two octaves (from 0.3692 ?m to 1.5142 ?m) and self-conversion of Raman-generation frequencies into the wavelength region of the second and third harmonics of one-micron pumping via many-step cascaded ?(3) ? ?(2) processes. (instruments and methods of investigation)

  19. New plasmonic materials in visible spectrum through electrical charging

    Science.gov (United States)

    Cao, Jiangrong; Balachandran, Rajesh; Keswani, Manish; Muralidharan, Krishna; Laref, Slimane; Ziolkowski, Richard; Runge, Keith; Deymier, Pierre; Raghavan, Srini; Miyawaki, Mamoru

    2013-02-01

    Due to their negative permittivity, plasmonic materials have found increasing number of applications in advanced photonic devices and metamaterials, ranging from visible wavelength through microwave spectrum. In terms of intrinsic loss and permittivity dispersion, however, limitations on available plasmonic materials remain a serious bottleneck preventing practical applications of a few novel nano-photonic device and metamaterial concepts in visible and nearinfrared spectra. To overcome this obstacle, efforts have been made and reported in literature to engineer new plasmonic materials exploring metal alloys, superconductors, graphene, and heavily doped oxide semiconductors. Though promising progress in heavily doped oxide semiconductors was shown in the near-infrared spectrum, there is still no clear path to engineer new plasmonic materials in the visible spectrum that can outperform existing choices noble metals, e.g. gold and silver, due to extremely high free electron density required for high frequency plasma response. This study demonstrates a path to engineer new plasmonic materials in the visible spectrum by significantly altering the electronic properties in existing noble metals through high density charging/discharging and its associated strong local bias effects. A density functional theory model revealed that the optical properties of thin gold films (up to 7 nm thick) can be altered significantly in the visible, in terms of both plasma frequency (up to 12%) and optical permittivity (more than 50%). These corresponding effects were observed in our experiments on surface plasmon resonance of a gold film electrically charged via a high density double layer capacitor induced by a chemically non-reacting electrolyte.

  20. Linearisation of RGB Camera Responses for Quantitative Image Analysis of Visible and UV Photography: A Comparison of Two Techniques

    OpenAIRE

    Jair E. Garcia; Adrian G. Dyer; Greentree, Andrew D.; Spring, Gale; Wilksch, Philip A.

    2013-01-01

    Linear camera responses are required for recovering the total amount of incident irradiance, quantitative image analysis, spectral reconstruction from camera responses and characterisation of spectral sensitivity curves. Two commercially-available digital cameras equipped with Bayer filter arrays and sensitive to visible and near-UV radiation were characterised using biexponential and Bézier curves. Both methods successfully fitted the entire characteristic curve of the tested devices, allowi...

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

    Science.gov (United States)

    von Hoyningen-Huene, W.; Yoon, J.; Vountas, M.; Istomina, L. G.; Rohen, G.; Dinter, T.; Kokhanovsky, A. A.; Burrows, J. P.

    2011-02-01

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

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

    Directory of Open Access Journals (Sweden)

    W. von Hoyningen-Huene

    2010-05-01

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

  3. Development of tunable Fabry-Perot spectral camera and light source for medical applications

    Science.gov (United States)

    Kaarre, M.; Kivi, S.; Panouillot, P. E.; Saari, H.; Mäkynen, J.; Sorri, I.; Juuti, M.

    2013-05-01

    VTT has developed a fast, tunable Fabry-Perot (FP) filter component and applied it in making small, lightweight spectral cameras and light sources. One application field where this novel technology is now tested is medical field. A demonstrator has been made to test the applicability of FP based spectral filtering in the imaging of retina in visible light wavelength area.

  4. Eye safe laser range finders

    International Nuclear Information System (INIS)

    During the 1970's, Ruby (Q switched) laser based range finders with a wavelength of 694nm were first used. These lasers operated in a pulse mode within the visible light range and produced a risk for the eye retina. The laser beam striking the macula could damage the eye and might cause blindness. Over the years, Nd:YAG (Q switched) lasers were developed (operating at 1064nm) for range finding and designation uses. The wavelength of these lasers, operating in the near Infra-Red range (invisible), is also focused tightly on the retina. The human eye does not respond to the invisible light so there is no natural protection (eye blink reflex) as in the visible light. The operation of these lasers worldwide, especially when the laser beam is exposed, causes occasional eye accidents. Another risk is stemming from the use of observation systems with a high optical gain, in the laser operation areas, which enlarge the range of risk quite significantly. Therefore, research and development efforts were invested in order to introduce eye safe lasers. One of the solutions for this problem is presented in following document

  5. The challenge of improving visibility in Beijing

    Directory of Open Access Journals (Sweden)

    Q. Zhang

    2010-03-01

    Full Text Available The "Blue Sky Project" was proposed in 1998 to investigate by how much emissions should be reduced to increase blue sky frequency in Beijing, which hosted the Summer Olympics in 2008. This paper focuses on the temporal variation of visibility and its dependence on meteorological conditions and suspended particles at Beijing using the hourly observed visibility data in Beijing Capital International Airport (BCIA from 1999 to 2007. It has been found that about 47.8% (24.2% of the hours in Beijing are "bad" ("good" hours with visibility below 10 km (equal or higher than 20 km between 1999 and 2007. Due to the high Relative Humidity (RH, summer is the season with the lowest mean visibility in a year. Although PM10 index was reported in a decreasing trend, the increase of RH has resulted in a decreasing trend of visibility over BCIA in the summer from 1999 to 2007. To ensure blue sky ("good" visibility for Olympics 2008, daily mean PM10 index should be reduced to 44 from 86.5. This requires that not only vehicle emissions, but also other emissions should be limited. Observations during Olympics 2008 verify that blue-sky-hour rate has been increased significantly after mean PM10 index was reduced to 56, however, the visibility during the same period of 2009 has returned to the mean standard before 2008.

  6. Spectral Classification Beyond M

    CERN Document Server

    Leggett, S K; Burgasser, A J; Jones, H R A; Marley, M S; Tsuji, T

    2004-01-01

    Significant populations of field L and T dwarfs are now known, and we anticipate the discovery of even cooler dwarfs by Spitzer and ground-based infrared surveys. However, as the number of known L and T dwarfs increases so does the range in their observational properties, and difficulties have arisen in interpreting the observations. Although modellers have made significant advances, the complexity of the very low temperature, high pressure, photospheres means that problems remain such as the treatment of grain condensation as well as incomplete and non-equilibrium molecular chemistry. Also, there are several parameters which control the observed spectral energy distribution - effective temperature, grain sedimentation efficiency, metallicity and gravity - and their effects are not well understood. In this paper, based on a splinter session, we discuss classification schemes for L and T dwarfs, their dependency on wavelength, and the effects of the parameters T_eff, f_sed, [m/H] and log g on optical and infra...

  7. Colored visible light metamaterials based on random dendritic cells

    CERN Document Server

    Song, K; Liu, B Q; Zhao, X P

    2011-01-01

    Optical metamaterials(OMs) at visible wavelengths have been extensively developed. OMs reported presently are all composed of periodic structure, and fabricated by top-down approaches. Here, the colored visible light frequencies metamaterials composed of double layer array disordered and geometrical variational dendritic cells are demonstrated, fabricating by a novel bottom-up approach. The experiment demonstrated that the OMs composed of random silver dendritic cells caused the appearance of multiple transmission passbands at red and yellow light frequencies. The slab focusing experiment reveals a clear point image in the range of half-wavelength with an intensity of 5% higher than that of the light source. Proposed colored OMs will open a new way to prepare the cloak and the perfect lens suitable for optical frequency.

  8. The NPOESS VIIRS Day/Night Visible Sensor.

    Science.gov (United States)

    Lee, Thomas E.; Miller, Steven D.; Turk, F. Joseph; Schueler, Carl; Julian, Richard; Deyo, Steve; Dills, Patrick; Wang, Sherwood

    2006-02-01

    The National Polar-orbiting Operational Environmental Satellite System (NPOESS) will feature the Visible-Infrared Imager-Radiometer Suite (VIIRS), a 22-channel imager that will contribute to nearly half of the NPOESS environmental data records. Included on VIIRS will be the Day/Night band (DNB), a visible channel designed to image the Earth and its atmosphere in all conditions ranging from bright solar illumination, to nocturnal lunar illumination, and negligible external illumination. Drawing heritage from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) instruments orbiting since the late 1960s, the DNB will be used to detect clouds at night, understand patterns of urban development based on the emissions of cities, monitor fires, and image scenes of snow and ice at the surface of the Earth. Thanks to significant engineering improvements, the DNB will produce superior capabilities to the OLS for a number of new applications.

  9. Freestanding GaN grating couplers at visible wavelengths

    Science.gov (United States)

    Liu, Qifa; Shi, Zheng; Zhu, Gangyi; Wang, Wei; Wang, Zhenhai; Wang, Yongjin

    2015-04-01

    A freestanding GaN grating coupler is proposed for planar photonic applications within the visible-wavelength spectrum. This freestanding device was produced by double-sided fabrication, combining GaN front patterning with Si substrate back releasing and GaN slab back thinning. Transverse-electric (TE) and transverse-magnetic (TM) light-wave conversion into and out of the membrane through grating coupling was determined by optical measurement. The maximum coupling efficiency is up to 69% for TE waves and 66% for TM waves at each particular wavelength according to the finite element method (FEM) simulation results. The experimental results were also supported by reflective simulation based on rigorous coupled-wave analysis (RCWA). This work opens the way for freestanding GaN planar photonic devices operating within the visible-wavelength range. It also provides the possibility of monolithic integration of planar photonic and light sources on III-nitride active platforms.

  10. Spectral-luminescent properties of zirconium orthosilicate prepared by hydrothermal method

    International Nuclear Information System (INIS)

    Spectral-luminescent properties of nominally pure zircons and zircons activated with r.e.e., Ti, Nb, Hf ions prepared by the method of hydrothermal synthesis are studied and interpreted. Effect of p-T conditions of synthesis, composition of charge, mineralizer, pH medium, experiment duration on parameters of natural and some impurity luminescence centers is studied. It is shown that variation of synthesis temperature and introduction of TiO2, KF, NaF, CaF2 addition enable to change essentially spectral composition of natural glow, shifting it to the 250-300 or 350-400 nm wavelength range. Possibility of evaluation of a degree of structural sample perfection from natural glow band width in roentgenoluminescence spectra is established. Intensive luminescence in the visible spectrum range is defined for zircons with Nb, Eu, Tb, Dy and for samples with Gd - in the UV spectrum range. The Shtark structure of Eusup(3+) ion multiplet transitions is under consideration. Three luminescence centers nonequivalent in respect to structure are isolated, and the course of their formation as a function of zircon synthesis conditions is observed

  11. Bunching visibility of optical parametric emission in a semiconductor microcavity

    Science.gov (United States)

    Ardizzone, Vincenzo; Abbarchi, Marco; Lemaitre, Aristide; Sagnes, Isabelle; Senellart, Pascale; Bloch, Jacqueline; Delalande, Claude; Tignon, Jerome; Roussignol, Philippe

    2012-07-01

    The statistic of parametric photon emission in a one-dimensional semiconductor microcavity optical parametric oscillator is reported. We perform photon-counting experiments on signal and idler beams by means of a Hanbury Brown and Twiss setup for studying the second-order coherence. Under pulsed laser excitation at normal incidence, energy-degenerate signal and idler beams are emitted in a mirror-symmetric configuration and share the same excitonic/photonic composition. Moreover the two emissions share the same intensity and the same coherence properties. We show that the bunching visibility [i.e., the value of g(2)(?=0)] changes across the parametric threshold and it is associated both to different spectral composition of the emission and to the buildup of coherence at high injection. Nevertheless, different from conventional optical parametric oscillators, a full coherence is never recovered.

  12. A Carpet Cloak Device for Visible Light

    CERN Document Server

    Gharghi, Majid; Zentgraf, Thomas; Liu, Yongmin; Yin, Xiaobo; Valentine, Jason; Zhang, Xiang

    2011-01-01

    We report an invisibility carpet cloak device, which is capable of making an object undetectable by visible light. The cloak is designed using quasi conformal mapping and is fabricated in a silicon nitride waveguide on a specially developed nano-porous silicon oxide substrate with a very low refractive index. The spatial index variation is realized by etching holes of various sizes in the nitride layer at deep subwavelength scale creating a local effective medium index. The fabricated device demonstrates wideband invisibility throughout the visible spectrum with low loss. This silicon nitride on low index substrate can also be a general scheme for implementation of transformation optical devices at visible frequency.

  13. Comparison of UV-RSS spectral measurements and TUV model runs for clear skies for the May 2003 ARM aerosol intensive observation period

    Directory of Open Access Journals (Sweden)

    J. J. Michalsky

    2007-11-01

    Full Text Available The first successful deployment of the fully-operational ultraviolet rotating shadow-band spectroradiometer occurred during the May 2003 U.S. Department of Energy's Atmospheric Radiation Measurement program's Aerosol Intensive Observation Period. The aerosol properties in the visible range were characterized using redundant measurements with several instruments to determine the column aerosol optical depth, the single scattering albedo, and the asymmetry parameter needed as input for radiative transfer calculations of the downwelling direct normal and diffuse horizontal solar irradiance in clear-sky conditions. The Tropospheric Ultraviolet and Visible (TUV radiative transfer model developed by Madronich and his colleagues at the U.S. National Center for Atmospheric Research was used for the calculations of the spectral irradiance between 300–360 nm. Since there are few ultraviolet measurements of aerosol properties, most of the input aerosol data for the radiative transfer model are based on the assumption that UV input parameters can be extrapolated from the visible portion of the spectrum. Disagreements between available extraterrestrial spectra, which are discussed briefly, suggested that instead of comparing irradiances that measured and modeled spectral transmittances between 300–360 nm should be compared for the seven cases studied. These cases included low to moderate aerosol loads and low to high solar-zenith angles. A procedure for retrieving single scattering albedo in the ultraviolet based on the comparisons of direct and diffuse transmittance is outlined.

  14. Direct correlation between aromatization of carbon- rich organic matter and its visible electronic absorption edge

    OpenAIRE

    Ferralis, Nicola; Liu, Yun; Bake, Kyle D.; Pomerantz, Andrew E.; Grossman, Jeffrey C.

    2015-01-01

    The evolution of the electronic absorption edge of type I, II and III kerogen is studied by diffuse reflectance UV-Visible absorption spectroscopy. The functional form of the electronic absorption edge for all kerogens measured is in excellent agreement with the "Urbach tail" phenomenology. The Urbach decay width extracted from the exponential fit within the visible range is strongly correlated with the aliphatic/aromatic ratio in isolated kerogen, regardless of the kerogen ...

  15. Quantitative Prediction of Beef Quality Using Visible and NIR Spectroscopy with Large Data Samples Under Industry Conditions

    Science.gov (United States)

    Qiao, T.; Ren, J.; Craigie, C.; Zabalza, J.; Maltin, Ch.; Marshall, S.

    2015-03-01

    It is well known that the eating quality of beef has a significant influence on the repurchase behavior of consumers. There are several key factors that affect the perception of quality, including color, tenderness, juiciness, and flavor. To support consumer repurchase choices, there is a need for an objective measurement of quality that could be applied to meat prior to its sale. Objective approaches such as offered by spectral technologies may be useful, but the analytical algorithms used remain to be optimized. For visible and near infrared (VISNIR) spectroscopy, Partial Least Squares Regression (PLSR) is a widely used technique for meat related quality modeling and prediction. In this paper, a Support Vector Machine (SVM) based machine learning approach is presented to predict beef eating quality traits. Although SVM has been successfully used in various disciplines, it has not been applied extensively to the analysis of meat quality parameters. To this end, the performance of PLSR and SVM as tools for the analysis of meat tenderness is evaluated, using a large dataset acquired under industrial conditions. The spectral dataset was collected using VISNIR spectroscopy with the wavelength ranging from 350 to 1800 nm on 234 beef M. longissimus thoracis steaks from heifers, steers, and young bulls. As the dimensionality with the VISNIR data is very high (over 1600 spectral bands), the Principal Component Analysis (PCA) technique was applied for feature extraction and data reduction. The extracted principal components (less than 100) were then used for data modeling and prediction. The prediction results showed that SVM has a greater potential to predict beef eating quality than PLSR, especially for the prediction of tenderness. The infl uence of animal gender on beef quality prediction was also investigated, and it was found that beef quality traits were predicted most accurately in beef from young bulls.

  16. Visible-near infrared spectra of hydrous carbonates, with implications for the detection of carbonates in hyperspectral data of Mars

    Science.gov (United States)

    Harner, Patrick L.; Gilmore, Martha S.

    2015-04-01

    We present visible-near infrared (VNIR, 0.35-5 ?m) spectra for a suite of hydrous carbonates that may be relevant to the surface of Mars. This includes VNIR spectra for ikaite, nesquehonite, synthetic monohydrocalcite and lansfordite over the 0.35-2.5 ?m range that are new to the literature. The spectral features of the hydrous carbonates are dominated by absorptions at ?1.0, 1.2, 1.4-1.5, 1.9 and 2.8 ?m that are due to overtones and combinations of fundamental water and hydroxyl vibrations. Absorptions due to (CO3)2-, Mg-OH, Fe-OH, and/or water are seen at ?2.3-2.5, 3.4, and 3.9 ?m in hydrous Mg and Mg-Fe3+ carbonates containing hydroxyl groups, but are weaker than in the common anhydrous carbonates. When present in the hydrous carbonates, the positions of the centers of the 2.3 ?m and/or 2.5 ?m absorptions are often shifted relative to the anhydrous carbonates, which may be diagnostic. Some or all of the (CO3)2- absorptions typical of anhydrous carbonates are weak to absent in the hydrous carbonates, and thus this group may be difficult to distinguish from other hydrous minerals like sulfates, phyllosilicates or chlorides in Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data using standard spectral search parameters for anhydrous carbonates. We present strategies for recognizing hydrous carbonates in CRISM data using combinations of spectral parameters that measure the intensity and shape of the water-related absorptions in these minerals.

  17. Solar surface albedo estimation using remotely sensed spectral data

    Science.gov (United States)

    Toll, David L.

    1989-01-01

    A solar albedo model based on converting narrow-band satellite-derived reflectance to four major spectral regions (ultraviolet, visible, near-infrared, and shortwave middle-infrared) and weighted by the relative supply of global solar radiation is studied and developed. Narrow-band to broad-band conversions within visible and near-infrared regions are shown to be accurate; however, the transformations are indicated to be surface-feature dependent. Atmospheric aerosol and illumination effects are indicated to be nearly insensitive to spectral region integrations for solar albedo estimation, but are shown to be significant factors affecting the spectral and canopy albedo. The erectophile and spherical canopy albedos were sensitive to atmospheric and illumination condition, whereas the planophile was relatively insensitive. The contribution of a shortwave middle-infrared reflectance to the canopy albedo is shown to be an important component, accounting for albedo changes to 16 percent with increasing vegetation.

  18. Infrared-to-visible upconversion luminescence in neodymium-doped bismuth-borate glass

    Energy Technology Data Exchange (ETDEWEB)

    Oprea, Isabella-Ioana; Hesse, Hartmut; Betzler, Klaus [Fachbereich Physik, Universitaet Osnabrueck, 49069 Osnabrueck (Germany)

    2005-10-01

    The upconversion luminescence in Nd{sup 3+}-doped bismuth-borate glass, excited by 0.8 {mu}m light, was studied in the visible spectral region. Four distinct emission bands were found. From their kinetics, two mechanisms can be shown to be responsible for all four lines: energy-transfer upconversion, slightly dominating, and excited state absorption. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Two-dimensional solar spectropolarimetry with the KIS/IAA Visible Imaging Polarimeter

    OpenAIRE

    C. Beck; Rubio, L. R. Bellot; Kentischer, T J; Tritschler, A.; Iniesta, J. C. del Toro

    2010-01-01

    Spectropolarimetry at high spatial and spectral resolution is a basic tool to characterize the magnetic properties of the solar atmosphere. We introduce the KIS/IAA Visible Imaging Polarimeter (VIP), a new post-focus instrument that upgrades the TESOS spectrometer at the German VTT into a full vector polarimeter. VIP is a collaboration between the KIS and the IAA. We describe the optical setup of VIP, the data acquisition procedure, and the calibration of the spectropolarime...

  20. Canopy spectral invariants, Part 2: Application to classification of forest types from hyperspectral data

    International Nuclear Information System (INIS)

    Many studies have been conducted to demonstrate the ability of hyperspectral data to discriminate plant dominant species. Most of them have employed the use of empirically based techniques, which are site specific, requires some initial training based on characteristics of known leaf and/or canopy spectra and therefore may not be extendable to operational use or adapted to changing or unknown land cover. In this paper we propose a physically based approach for separation of dominant forest type using hyperspectral data. The radiative transfer theory of canopy spectral invariants underlies the approach, which facilitates parameterization of the canopy reflectance in terms of the leaf spectral scattering and two spectrally invariant and structurally varying variables-recollision and directional escape probabilities. The methodology is based on the idea of retrieving spectrally invariant parameters from hyperspectral data first, and then relating their values to structural characteristics of three-dimensional canopy structure. Theoretical and empirical analyses of ground and airborne data acquired by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) over two sites in New England, USA, suggest that the canopy spectral invariants convey information about canopy structure at both the macro- and micro-scales. The total escape probability (one minus recollision probability) varies as a power function with the exponent related to the number of nested hierarchical levels the number of nested hierarchical levels present in the pixel. Its base is a geometrical mean of the local total escape probabilities and accounts for the cumulative effect of canopy structure over a wide range of scales. The ratio of the directional to the total escape probability becomes independent of the number of hierarchical levels and is a function of the canopy structure at the macro-scale such as tree spatial distribution, crown shape and size, within-crown foliage density and ground cover. These properties allow for the natural separation of dominant forest classes based on the location of points on the total escape probability vs the ratio log-log plane.

  1. Canopy Spectral Invariants. Part 2; Application to Classification of Forest Types from Hyperspectral Data

    Science.gov (United States)

    Schull, M. A.; Knyazikhin, Y.; Xu, L.; Samanta, A.; Carmona, P. L.; Lepine, L.; Jenkins, J. P.; Ganguly, S.; Myneni, R. B.

    2011-01-01

    Many studies have been conducted to demonstrate the ability of hyperspectral data to discriminate plant dominant species. Most of them have employed the use of empirically based techniques, which are site specific, requires some initial training based on characteristics of known leaf and/or canopy spectra and therefore may not be extendable to operational use or adapted to changing or unknown land cover. In this paper we propose a physically based approach for separation of dominant forest type using hyperspectral data. The radiative transfer theory of canopy spectral invariants underlies the approach, which facilitates parameterization of the canopy reflectance in terms of the leaf spectral scattering and two spectrally invariant and structurally varying variables - recollision and directional escape probabilities. The methodology is based on the idea of retrieving spectrally invariant parameters from hyperspectral data first, and then relating their values to structural characteristics of three-dimensional canopy structure. Theoretical and empirical analyses of ground and airborne data acquired by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) over two sites in New England, USA, suggest that the canopy spectral invariants convey information about canopy structure at both the macro- and micro-scales. The total escape probability (one minus recollision probability) varies as a power function with the exponent related to the number of nested hierarchical levels present in the pixel. Its base is a geometrical mean of the local total escape probabilities and accounts for the cumulative effect of canopy structure over a wide range of scales. The ratio of the directional to the total escape probability becomes independent of the number of hierarchical levels and is a function of the canopy structure at the macro-scale such as tree spatial distribution, crown shape and size, within-crown foliage density and ground cover. These properties allow for the natural separation of dominant forest classes based on the location of points on the total escape probability vs the ratio log-log plane.

  2. Measurement and calculation of the spatial and spectral distribution of wavelength shifter radiation at BESSY

    International Nuclear Information System (INIS)

    Calculable synchrotron radiation (SR) from BESSY dipole magnets has been used by PTB for radiometry from the visible to the soft x-ray region with very low uncertainties for many years. The use of wavelength shifter (WLS) radiation bears the potential of extending the usable spectral range for radiometry with calculable SR to higher photon energies. Initial investigations on the feasibility of this approach have been performed: an energy dispersive high-purity germanium detector (HPGe) was used to characterize the radiation of the new BESSY WLS with a magnetic field of B=3.2 T. The HPGe detector has previously been calibrated and so the absolute spectral photon flux could be determined. The measured spectral photon flux was then compared to calculations and good agreement was found in the order of ±5%. Although this is to our knowledge the best agreement demonstrated so far for an absolute comparison of measured WLS radiation to calculations, further improvements are needed for a future radiometric use of WLS radiation. This will be discussed. copyright 1996 American Institute of Physics

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

    International Nuclear Information System (INIS)

    Recently, we developed a number of high quality noncollinear acousto-optic tunable filter (AOTF) cells in different birefringent materials with UV imaging capability. Cells based on a single crystal of KDP (potassium dihydrophosphate) had the best transmission efficiency and the optical throughput needed to acquire high quality spectral images at wavelengths above 220 nm. One of the main limitations of these imaging filters was their small angular aperture in air, limited to about 1.0°. In this paper, we describe an improved imaging KDP AOTF operating from the deep UV to the visible region of the spectrum. The linear and angular apertures of the new filter are 10 × 10 mm2 and 1.8°, respectively. The spectral tuning range is 205–430 nm with a 60 cm?1 spectral resolution. We describe the filter and present experimental results on imaging using both a broadband source and a number of light emitting diodes (LEDs) in the UV, and include the measured spectra of these LEDs obtained with a collinear SiO2 filter-based spectrometer operating above 255 nm. (paper)

  4. Visible Light Communications: Challenges and potential

    OpenAIRE

    O'Brien, DC

    2011-01-01

    Visible Light Communications uses modern solid-state lighting sources for free-space communication, and can also provide other functions such as illumination and information display. This paper outlines some the challenges, and potential of this technique. © 2011 IEEE.

  5. AUTOMATION OF AN ULTRAVIOLET-VISIBLE SPECTROMETER

    Science.gov (United States)

    This report is an overview of the functional description and major features of an automated ultraviolet-visible spectrometer system intended for environmental measurements application. As such, it defines functional specifications and requirements which are divided into the chlor...

  6. Variations of images to increase their visibility

    CERN Document Server

    Sparavigna, Amelia Carolina

    2012-01-01

    The calculus of variations applied to the image processing requires some numerical models able to perform the variations of images and the extremization of appropriate actions. To produce the variations of images, there are several possibilities based on the brightness maps. Before a numerical model, I propose an experimental approach, based on a tool of Gimp, GNU Image Manipulation Program, in order to visualize how the image variations can be. After the discussion of this tool, which is able to strongly increase the visibility of images, the variations and a possible functional for the visibility are proposed in the framework of a numerical model. The visibility functional is analogous to the fringe visibility of the optical interference.

  7. Brightness temperature constraints from interferometric visibilities

    CERN Document Server

    Lobanov, Andrei

    2014-01-01

    The brightness temperature is an effective parameter that describes the physical properties of emitting material in astrophysical objects. It is commonly determined by imaging and modeling the structure of the emitting region and estimating its flux density and angular size. Reliable approaches for visibility-based estimates of brightness temperature are needed for interferometric experiments in which poor coverage of spatial frequencies prevents successful imaging of the source structure, for example, in interferometric measurements made at millimeter wavelengths or with orbiting antennas. Such approaches can be developed by analyzing the relations between brightness temperature and visibility amplitude and its r.m.s. error. A method is introduced for directly calculating the lower and upper limits of the brightness temperature from visibility measurements. The visibility-based brightness temperature estimates are shown to agree well with the image-based estimates obtained in the 2\\,cm MOJAVE survey and the ...

  8. Spectral analysis of signals the missing data case

    CERN Document Server

    Wang, Yanwei

    2006-01-01

    Spectral estimation is important in many fields including astronomy, meteorology, seismology, communications, economics, speech analysis, medical imaging, radar, sonar, and underwater acoustics. Most existing spectral estimation algorithms are devised for uniformly sampled complete-data sequences. However, the spectral estimation for data sequences with missing samples is also important in many applications ranging from astronomical time series analysis to synthetic aperture radar imaging with angular diversity. For spectral estimation in the missing-data case, the challenge is how to extend t

  9. New Criterion for Lunar Crescent Visibility

    Science.gov (United States)

    Odeh, Mohammad Sh.

    2004-04-01

    A new criterion for lunar crescent visibility has been established using 737 observations, almost half of them obtained by the Islamic Crescent Observation Project (ICOP). This criterion is based on two variables, viz. the topocentric arc of vision and the topocentric crescent width. The new model is able to predict the visibility of the lunar crescent both for naked eye and optically aided observations. From the database we found a Danjon limit of 6.4 degrees.

  10. The challenge of improving visibility in Beijing

    Directory of Open Access Journals (Sweden)

    Q. H. Zhang

    2010-08-01

    Full Text Available The "Blue Sky Project" was proposed in 1998 to investigate by how much emissions should be reduced to increase blue sky frequency in Beijing, which hosted the Summer Olympics in 2008. This paper focuses on the temporal variation of visibility and its dependence on meteorological conditions and suspended particles at Beijing using the hourly observed visibility data at Beijing Capital International Airport (BCIA from 1999 to 2007. It has been found that about 47.8% (24.2% of the hours in Beijing are "bad" ("good" hours with visibility below 10 km (equal or higher than 20 km between 1999 and 2007. Due to the high Relative Humidity (RH, summer is the season with the lowest mean visibility in a year. Although PM10 index was reported in a decreasing trend (Chan and Yao, 2008, the increase of RH has resulted in a decreasing trend of visibility over BCIA in the summer from 1999 to 2007. To ensure blue sky ("good" visibility for Olympics 2008, daily mean PM10 index should have been reduced from 81 to 44. This requires that not only vehicle emissions, but also other emissions should be limited. Observations verify that blue-sky-hour rate increased significantly after mean PM10 index was reduced to 53 during Olympics 2008, however, the visibility of 2009 returned to the mean level from 1999 to 2007 during the period 8?24 August. RH (aerosol contribute 24% (76% of the improvement of visibility during August 2008.

  11. Earth's curvature and visibility between two points

    OpenAIRE

    Mirko A. Borisov; Radoje D. Bankovi?

    2012-01-01

    In this study, the Earth's curvature is analyzed from numerous aspects as well as the visibility between two points on the Earth's surface. It also describes the way and the size of the Earth's part which can be approximated in the plane depending on the graphical precision and the scale of topographic maps. It equally considers the possibility of visibility between two points on the Earth's surface depending on the relief shapes and the curvature of the Earth's surface applying both classica...

  12. Aerosol single scattering albedo retrieved from ground-based measurements in the UV and visible region

    Directory of Open Access Journals (Sweden)

    V. Buchard

    2011-01-01

    Full Text Available Estimates of Aerosol Single Scattering Albedo (SSA from ground-based spectral measurements in the UV-visible are conducted at Villeneuve d'Ascq (VdA in France. In order to estimate this parameter, measurements of global and diffuse UV-visible solar irradiances performed under cloud-free conditions since 2003 with a spectroradiometer operated by the Laboratoire d'Optique Atmosphérique (LOA are used. The technique consists in comparing the measured irradiance values to modelled irradiances computed for various SSA. The retrieval is restricted to the 330–450 nm range to avoid ozone influence.

    For validation purpose, the retrieved values of SSA at 440 nm are compared to the ones obtained from sunphotometer measurements of the AERONET/PHOTONS network available on the LOA site. The results are rather satisfying: for the period 2003–2006 the Root Mean Square (RMS of the differences is about 0.05, this value is within the uncertainty domain of retrieval of both products. Distinction between days characterized by different aerosol content, by means of the aerosol optical thickness (AOT retrieved from ground-based measurements at the same wavelength, shows that the comparisons between both products are better when AOT are higher. Indeed in case AOT are greater than 0.2, the RMS is 0.031 compared to 0.060 for days with an AOT lower than 0.2. The SSA estimated at 340 and 380 nm from ground-based spectra are also studied, though no validation can be carried out with sunphotometer data (440 nm is the shortest wavelength at which the SSA is provided by the network. The good comparisons observed at 440 nm can let assume that the SSA retrieved from spectroradiometer measurements at the two other wavelengths are also obtained with a good confidence level. Thus these values in the UV range can be used to complete aerosol data provided by AERONET/PHOTONS at VdA. Moreover they can be used for a best knowledge of the aerosol absorption that is necessary to quantify the error on surface UV irradiances estimated from satellites.

  13. Aerosol Single Scattering Albedo retrieved from ground-based measurements in the UV-visible

    Directory of Open Access Journals (Sweden)

    V. Buchard

    2010-07-01

    Full Text Available Estimates of Aerosol Single Scattering Albedo (SSA from ground-based spectral measurements in the UV-visible are conducted at Villeneuve d'Ascq (VdA in France. In order to estimate this parameter, measurements of global and diffuse UV-visible solar irradiances performed under cloud-free conditions since 2003 with a spectroradiometer operated by the Laboratoire d'Optique Atmosphérique (LOA are used. The technique consists in comparing the measured irradiance values to modelled irradiances computed for various SSA. The retrieval is restricted to the 330–450 nm range to avoid ozone influence.

    For validation purpose, the retrieved values of SSA at 440 nm are compared to the ones obtained from sunphotometer measurements of the AERONET/PHOTONS network available on the LOA site. The results are rather satisfying: in 2003 and 2005–2006 the Root Mean Square (RMS of the differences are about 0.05, these values are within the uncertainty domain of retrieval of both products. Distinction between days characterized by different aerosol content, by means of the aerosol optical thickness (AOT retrieved from ground-based measurements at the same wavelength, shows that the comparisons between both products are better when AOT are higher. Indeed in case AOT are greater than 0.2, the RMS is 0.027 in 2003 and 0.035 in 2005–2006. The SSA estimated at 340 and 380 nm from ground-based spectra are also studied, though no validation can be carried out with sunphotometer data (440 nm is the shortest wavelength at which the SSA is provided by the network. The good comparisons observed at 440 nm can let assume that the SSA retrieved from spectroradiometer measurements at the two other wavelengths are also obtained with a good confidence level. Thus these values in the UV range can be used to complete aerosol data provided by AERONET/PHOTONS at VdA. Moreover they can be used for a best knowledge of the aerosol absorption that is necessary to quantify the error on surface UV irradiances estimated from satellite.

  14. Unsupervised spectral learning of FSTs

    OpenAIRE

    Bailly, Raphae?l; Carreras Pe?rez, Xavier; Quattoni, Ariadna Julieta

    2013-01-01

    Finite-State Transducers (FST) are a standard tool for modeling paired input output sequences and are used in numerous applications, ranging from computational biology to natural language processing. Recently Balle et al. [4] presented a spectral algorithm for learning FST from samples of aligned input-output sequences. In this paper we address the more realistic, yet challenging setting where the alignments are unknown to the learning algorithm. We frame FST learning as finding a low rank Ha...

  15. Rotationally Resolved Spectroscopy of Asteroid Pairs: No Spectral Variation Suggests Fission is followed by Settling of Dust

    CERN Document Server

    Polishook, David; DeMeo, Francesca; Binzel, Richard P

    2014-01-01

    We examine the spectral properties of asteroid pairs that were disrupted in the last 2 Myrs to examine whether the site of the fission can be revealed. We studied the possibility that the sub-surface material, perhaps on one hemisphere, has spectral characteristics differing from the original weathered surface, by performing rotationally-resolved spectroscopic observations to look for local variations as the asteroid rotates. We observed 11 asteroids in pairs in the near-IR and visible range. Photometry was also conducted to determine the rotational phases of a spectrum on the asteroid lightcurves. We do not detect any rotational spectral variations within the signal-to-noise, which allow us to constrain the extent of any existing surface heterogeneity. For each observed spectrum of a longitudinal segment of an asteroid, we estimate the maximal size of an un-detected "spot" with a spectral signature different than the average. For 5 asteroids the maximal diameter of such a spot is smaller by a factor of two t...

  16. An integrated model of soil-canopy spectral radiance observations, photosynthesis, fluorescence, temperature and energy balance

    Directory of Open Access Journals (Sweden)

    C. van der Tol

    2009-06-01

    Full Text Available This paper presents the model SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes, which is a vertical (1-D integrated radiative transfer and energy balance model. It calculates the radiation and the energy balance of a vegetated land surface at the level of single leaves as well as at canopy level, and the spectrum of the outgoing radiation in the viewing direction, at a high spectral resolution over the range from 0.4 to 50 ?m, thus including the visible, near and shortwave infrared, as well as the thermal domain. A special routine is dedicated to the calculation of chlorophyll fluorescence. The calculation of radiative transfer and the energy balance is fully integrated, allowing for feedback between surface temperatures, leaf chlorophyll fluorescence and radiative fluxes. Model simulations were evaluated against observations reported in the literature. The model may serve as a theoretical ground truth to derive relationships between observed spectra and physical processes at the land surface.

  17. MTF and PSF measurements of the CCD273-84 detector for the Euclid visible channel

    Science.gov (United States)

    Swindells, I.; Wheeler, R.; Darby, S.; Bowring, S.; Burt, D.; Bell, R.; Duvet, L.; Walton, D.; Cole, R.

    2014-08-01

    The European Space Agency (ESA) and e2v, together with the Euclid Imaging Consortium, have designed and manufactured pre-development models of a novel imaging detector for the visible channel of the Euclid space telescope. The new detector is an e2v back-illuminated, 4k x 4k, 12 micron square pixel CCD designated CCD273-84. The backilluminated detectors have been characterised for many critical performance parameters such as read noise, charge transfer efficiency, quantum efficiency, Modulation Transfer Function and Point Spread Function. Initial analysis of the MTF and PSF performance of the detectors has been performed by e2v and at MSSL and the results have enabled the Euclid VIS CCD project to move in to the C/D or flight phase delivery contract. This paper describes the CCD273-84 detector, the test method used for MTF measurements at e2v and the test method used for PSF measurements at MSSL. Results are presented for MTF measurements at e2v over all pre development devices. Also presented is a cross comparison of the data from the MTF and PSF measurement techniques on the same device. Good agreement between the measured PSF Full Width Half Maximum and the equivalent Full Width Half Maximum derived from the MTF images and test results is shown, with results that indicate diffusion FWHM values at or below 10 micron for the CCD273-84 detectors over the spectral range measured. At longer wavelengths the diffusion FWHM is shown to be in the 6-8 micron range.

  18. [Multi-wavelength spectral aerosol scale height in inshore in contrast with that in inland].

    Science.gov (United States)

    Han, Yong; Rao, Rui-Zhong; Wang, Ying-Jian

    2009-01-01

    In the present paper, based on the exponential attenuation of atmospheric aerosol concentration with height, so using continuous spectrum sun-photometer, forward scatter visibility sensor and hygrothermograph, the authors measured the atmosphere column optical characteristic and plane spectral extinction coefficient on earth on the base of two experiments at some edge of ocean at the same time, respectively, set up the calculative method of multi-wavelength spectral aerosol scale height. Firstly, the authors obtained atmospheric horizontal extinction coefficient with forward scattering visibility sensor, which subtracted molecular extinction coefficient, and could get aerosol extinction coefficient near ground; Then, selecting sea salt model, using OPAC software, the authors also could calculate the aerosol extinction coefficient under different humidity (0%, 50%, 70%, 80%, 90%, 95%, 98% and 99%) and different wavelength (400, 450, 500, 550, 600, 650, 700 and 750 nm), the aerosol extinction coefficient was detected by visibility sensor, using interpolation method, respectively; Finally, using the data of atmospheric columniation optical thickness detected by continuous spectral sun-photometer and subtracted molecular optical thickness corresponding wavelengths were accounted out by Modtran 4. 0. The authors obtained the characteristic of spectral aerosol scale height of visible light (wavelength is 400, 440, 532, 550 and 690 nm): with wavelength increments, and spectral aerosol scale height was found to decline neither in inland nor in inshore in China; Spectral aerosol scale height in winter is higher than in summer in southeast inshore; but spectral aerosol scale height in winter is smaller in summer than in inland. PMID:19385200

  19. General spectral utility metric for spectral imagery

    Science.gov (United States)

    Simmons, Rulon E.; Elder, Timothy D.; Stewart, David J.; Cincotta, Eric J.; Kennedy, Carolyn S.; Van Nostrand, R. Craig

    2005-06-01

    Published approaches to assessing and predicting spectral image utility are generally based on regression methods which fit coefficients to an equation with terms representing spatial scale, spectral fidelity, and signal-to-noise. Such approaches are patterned after the National Imagery Interpretability Rating Scale General Image Quality Equation (NIIRS GIQE) designed for use with remotely-sensed panchromatic imagery. Preliminary testing of these approaches suggests that they will work for some subsets of spectral imagery applications but are not generally applicable to all spectral imaging problems. We present here an approach that gets at the heart of the general problem-assessing the confidence of an image analyst in performing a specified task with a specific spectral image. While applicable in other areas such as health imaging, our approach to spectral utility assessment is presented in this paper from a remote sensing point of view. Our approach allows trade-offs in tasking and system design across the "spectrum" of imagers including panchromatic, multispectral, hyperspectral, and even ultraspectral. Our approach is based on a fusion concept called "semantic transformation." We assume that spectral and spatial information are largely separable with both contributing to the overall utility of the image. The "semantic transformation" combines the spatial and spectral information in a common term (in our case confidence) to give an overall confidence in performing the specified task. Addressing the spatial and spectral information separately allows us the freedom to assess the information contained in each in ways that the information is actually assimilated (i.e., usually spatial information in exploited visually while spectral information consisting of more than three or four bands is usually exploited by computer algorithms). For the spectral information, we can use either generic exploitation algorithms or the specific algorithms that the image analyst would be expected to use. Testing of our approach was done with a parametric set of simulated imagery where Ground Sampled Distance (GSD) and the number of spectral bands were varied. Our initial test led to some refinements of our approach, which are discussed.

  20. Detecting and quantifying sunflower oil adulteration in extra virgin olive oils from the eastern mediterranean by visible and near-infrared spectroscopy.

    Science.gov (United States)

    Downey, Gerard; McIntyre, Peter; Davies, Antony N

    2002-09-25

    One hundred and thirty-eight oil samples have been analyzed by visible and near-infrared transflectance spectroscopy. These comprised 46 pure extra virgin olive oils and the same oils adulterated with 1% (w/w) and 5% (w/w) sunflower oil. A number of multivariate mathematical approaches were investigated to detect and quantify the sunflower oil adulterant. These included hierarchical cluster analysis, soft independent modeling of class analogy (SIMCA method), and partial least squares regression (PLS). A number of wavelength ranges and data pretreatments were explored. The accuracy of these mathematical models was compared, and the most successful models were identified. Complete classification accuracy was achieved using 1st derivative spectral data in the 400-2498 nm range. Prediction of adulterant content was possible with a standard error equal to 0.8% using 1st derivative data between 1100 and 2498 nm. Spectral features and chemical literature were studied to isolate the structural basis for these models. PMID:12236673