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1

Semiconductor emitters in the visible and near IR spectral range  

Science.gov (United States)

Semiconductor emitters for the spectral domain covering the visible (from 560 nm) to the near IR are treated. Junction semiconductors from groups 3 and 5 are the starting materials for semiconductor emitters. The emission wavelengths can be varied by the production of mixed crystals of variable composition (GaxAS1-x P, Aly GA 1-y As). The components, developed as p-m-diodes, emit radiation if they are operated in the forward direction. By the development of heterostructures with different materials (GaAs and AlGaAs, InP and InGaAs) components with an exceptionally favorable emission characteristic curve of the coupling in optical systems or fibers can be produced, such as emitter LED's and semiconductor lasers, the peculiarities of which are discussed with a view to applications in measurement techniques.

Wagner, E.; Gillessen, K.

2

Compact solid-state lasers in the near-infrard and visible spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The subject of this thesis is the exploration of new concepts for compact solid-state lasers in the visible and near-infrared spectral range using new components such as volume Bragg gratings for wavelength stabilisation and wavelength tuning. Also single-walled carbon nanotubes for mode-locking and Q-switching of lasers have been studied.We have developed a new method for the tuning of solid-state lasers by replacing a dielectric mirror with a transversally chirped volume Bragg grating, whic...

Seger, Kai

2013-01-01

3

Silicon nitride PhC nanocavities as versatile platform for visible spectral range devices  

Science.gov (United States)

We propose silicon nitride two-dimensional photonic crystal resonators as flexible platform to realize photonic devices based on spontaneous emission engineering of nanoemitters in the visible spectral range. The versatility of our approach is demonstrated by coupling the two dipole-like modes of a closed band gap H1 nanocavity with: (i) DNA strands marked with Cyanine 3 organic dyes, (ii) antibodies bounded to fluorescent proteins and (iii) colloidal semiconductor nanocrystals localized in the maximum of the resonant electric field. The experimental results are in good agreement with the numerical simulations, highlighting the good coupling of the nanocavities with both organic and inorganic light emitters.

Pisanello, F.; Martiradonna, L.; Qualtieri, A.; Stomeo, T.; Grande, M.; Pompa, P. P.; Cingolani, R.; Bramati, A.; De Vittorio, M.

2012-06-01

4

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

Directory of Open Access Journals (Sweden)

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.

Mi-Yun Jeong

2011-03-01

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)

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.

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

7

Thermo-optical response of photonic crystal cavities operating in the visible spectral range  

International Nuclear Information System (INIS)

In this paper we study thermo-optical effects in gallium phosphite photonic crystal cavities in the visible range. By measuring the shift of narrow resonances, we derive the temperature dependency of the local refractive index of gallium phosphide in an attoliter volume over a temperature range between 5 and 300 K at a wavelength of about 605 nm. Additionally, the potential of photonic crystal cavities for thermo-optical switching of visible light is investigated. As an example we demonstrate thermo-optical switching with 13 dB contrast. (paper)

8

Investigation of silicon nitride based two-dimensional photonic crystals for the visible spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main topics of this thesis included the fabrication and experimental investigation of silicon nitride based 2D photonic crystals in the visible range of the electromagnetic spectrum. For this purpose, a fabrication process capable of patterning silicon nitride with an ultimate resolution of 25 nm as well as an investigation technique based on non-coherent white light transmission measurements were successfully developed. Using these techniques, photonic crystals with square and hexagonal ...

Kouba, Josef

2008-01-01

9

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

Science.gov (United States)

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.

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

2014-05-01

10

Multiwavelength sun-photometers for accurate measurements of atmospheric extinction in the visible and near-IR spectral range.  

Science.gov (United States)

A new multiwavelength sun-photometer has been developed to obtain accurate measurements of the atmospheric attenuation of direct solar radiation at seven window wavelengths in the visible and near-infrared spectral range. The instrument's optical features and performance are described. The photometer was calibrated by following a careful procedure based on the Langley method. An additional eighth bandpass filter was used to obtain measurements of the precipitable water. Five examples of this instrument have been constructed and calibrated for a network of mountain stations in Southern Italy to monitor Sahara dust transport episodes. PMID:18195838

Tomasi, C; Prodi, F; Sentimenti, M; Cesari, G

1983-02-15

11

Phase and microstructure investigations of boron nitride thin films by spectroscopic ellipsometry in the visible and infrared spectral range  

International Nuclear Information System (INIS)

Spectroscopic ellipsometry over the spectral range from 700 to 3000 cm-1 and from 1.5 to 3.5 eV is used to simultaneously determine phase and microstructure of polycrystalline hexagonal and cubic boron nitride thin films deposited by magnetron sputtering on (100) silicon. The results are obtained from a single microstructure-dependent model for both infrared and visible-light thin-film anisotropic dielectric functions. The optical behavior of high c-BN content thin films is described by an effective medium approximation. We obtain the amount of h-BN within high c-BN content thin films. A thin oriented nucleation layer between the silicon substrate and the high c-BN content layer is demonstrated. The preferential arrangement of the grain c axes within the h-BN thin films are found to be dependent on the growth parameters. The results from the infrared and visible spectral range ellipsometry model are compared to each other and found to be highly consistent. copyright 1997 American Institute of Physics

12

Evidence for graphene plasmons in the visible spectral range probed by molecules  

CERN Document Server

Graphene is considered to be plasmon active only up to the infrared based on combined tight binding model and random phase approximation calculations. Here we show that the optical properties of graphene as measured by ellipsometry and simulated by density functional theory imply the existence of strongly localized graphene plasmons in the visible with a line width of 0.1 eV. Using small emitters that provide the high wavevectors necessary to excite graphene plasmons at optical frequencies we demonstrate graphene plasmon induced excitation enhancement by nearly 3 orders of magnitude.

Lange, Philipp; Severin, Nikolai; Benson, Oliver; Rabe, Jürgen P

2014-01-01

13

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

CERN Document Server

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...

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

2009-01-01

14

MEMS-based optical mini- and microspectrometers for the visible and infrared spectral range  

Science.gov (United States)

Miniaturized free-field based optical microspectrometers have huge potential for application in industry, science, medicine, agriculture and biology. State-of-the-art is the micro-assembly of micromachined optical components on a mini-bench and the trend is towards fully integrated optical microsystems. Complete silicon IC compatible MEMS-based opto-electrical microsystems on a single chip may offer huge cost benefits in these potentially high-volume applications. On-chip integration does, however, impose limitations. The required process compatibility and limited choice of acceptable materials does not necessarily give optimum optical performance. Also, the dimensional downscaling is not generally an optical advantage. This overview discusses grating-based and interferometer-based mini- and microspectrometers, shows performances already reported, the trends, the potential, the limitations and approaches to obtain a sufficient optical performance, in terms of spectral resolution and throughput, for serving the majority of applications.

Wolffenbuttel, R. F.

2005-07-01

15

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

Directory of Open Access Journals (Sweden)

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 contents 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 of water vapour columns distributed over the whole globe.

S. Mieruch

2007-08-01

16

Asymmetric one-dimensional photonic crystal for optical sensing in the visible spectral range  

Science.gov (United States)

A gas sensor based on an asymmetric one-dimensional (1D) photonic band gap structure with one defect layer was designed and fabricated through layer-by-layer deposition of spin-coated poly methyl methacrylate (PMMA) and vacuum-deposited As2S3. Initially, the thickness variations, ?d, were determined of the thin films resulting from the poly methyl methacrylate exposure to chloroform vapor in the concentration range 100 - 9000 ppm. It was found that the value of ?d depends on the gas concentration and the exposure time. A two-layer structure was prepared consisting of PMMA and vacuum-deposited As2S3. Further, the permeability of thin As2S3 films to chloroform vapors was investigated. The asymmetric photonic structure consisted of 11 alternating layers of As2S3 and PMMA. The defect PMMA layer was located before the last high-refractive-index film of chalcogenide glass. The thickness of the defect layer of PMMA was pre-calculated so that the pass band be centered at the wavelength of 550 nm. An offset was observed of the position of the pass band to the larger wavelengths after exposure to chloroform vapor. The multilayered structure proposed is promising for optical sensor applications.

Lalova, A.; Todorov, R.

2014-05-01

17

TiN/(Al,Sc)N metal/dielectric superlattices and multilayers as hyperbolic metamaterials in the visible spectral range  

Science.gov (United States)

Hyperbolic metamaterials (HMMs) based on metal/dielectric multilayers have garnered attention in recent years due to their extraordinary optical properties emanating from hyperbolic dispersion of isofrequency surfaces. We have developed a new class of epitaxial metal/dielectric superlattice HMMs based on transition-metal nitrides—titanium nitride (TiN) and aluminum scandium nitride (AlxSc1-xN)—that could potentially lead to better HMM performance without requiring any traditional plasmonic materials such as gold (Au) and silver (Ag). Our results suggest that the TiN/(Al,Sc)N superlattices grown on (001) MgO substrates are nominally monocrystalline and pseudomorphic, exhibiting sharp interfaces with interface roughnesses of about one to two atomic layers. HMMs deposited on (0001) sapphire substrates grow in 111 orientation with local epitaxy inherent to individual grains, while on (001) Si substrates, the HMMs are polycrystalline. The HMM properties extracted with effective medium theory along with nonlocal field corrections indicate that the TiN/(Al,Sc)N superlattices grown on MgO substrates have both transverse negative (type-I) and transverse positive (type-II) hyperbolic dispersion of the isofrequency surfaces in the visible to near-IR spectral regions. The carrier concentration of TiN layers was varied deliberately by tuning the deposition conditions, thereby shifting the spectral range of both type-I and type-II HMM dispersions. The epitaxial thin-film-based HMMs developed here mark the beginning of a new generation of optical metamaterials with enhanced electromagnetic properties.

Saha, Bivas; Naik, Gururaj V.; Saber, Sammy; Akatay, Cem; Stach, Eric A.; Shalaev, Vladimir M.; Boltasseva, Alexandra; Sands, Timothy D.

2014-09-01

18

Radiative transfer model STORM for full Stokes vector calculations in the visible and near infrared spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available Based on the Matrix-Operator Method the radiative transfer code STORM (STOkes vector Radiative transfer Model is introduced, which was developed in a joint project of DLR and Institut f{ü}r Weltraumwissenschaften-Freie Universität Berlin. STORM calculates the Stokes parameters (I, Q, U, V in a plane parallel, multi layered atmosphere in the visible and near infrared spectral range. The scattering characteristics of aerosols are determined by Mie theory. The surface represents a Lambertian reflector or a wind ruffled water surface described by Cox-Munk model. The results of one calculation are the upward and downward directed Stokes parameters for one wavelength at a desired number of sun incident and viewing angles at varying altitudes in the principal plane and other azimuth angles. STORM is applied for an analysis in view of designing downward looking Earth observing optical remote sensing systems and values of the degree of polarization are presented as generic basis for remote sensing system design and data processing.

U. Böttger

2006-01-01

19

Dielectric function of cubic InN from the mid-infrared to the visible spectral range  

International Nuclear Information System (INIS)

The complex dielectric function for cubic InN is determined by spectroscopic ellipsometry from the mid-infrared into the visible spectral region. Films were grown by molecular beam epitaxy on c-GaN/3C-SiC pseudo-substrates. The high electron densities above 1019 cm?3 cause pronounced Burstein–Moss shifts at the gap. Taking into account the non-parabolicity and the filling of the conduction band, data analysis yields renormalized band edges between 0.43 and 0.455 eV. Including carrier-induced band-gap renormalization, we estimate a zero-density band gap of ?0.595 eV for c-InN which is about 85 meV lower than for hexagonal InN. Values for the electron effective mass, the static and high-frequency dielectric constant are reported

20

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

CERN Document Server

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 liftime. We report on the significant progress in ion-blocking and provide first results on bialkali-photocathode aging under gas multiplication.

Breskin, Amos; Lyashenko, A; Chechik, R; Amaro, F D; Maia, J M; Veloso, J F C; Dos Santos, J M F

2005-01-01

 
 
 
 
21

System for time resolved spectral studies of pulsed atmospheric discharges in the visible to vacuum ultraviolet range.  

Science.gov (United States)

Vacuum ultraviolet (VUV) emission is believed to play a major role in the development of plasma streamers in pulsed atmospheric discharges, but detection of VUV light is difficult in pulsed experiments at atmospheric pressures. Since VUV light is absorbed in most standard optical materials as well, careful attention must be given to the selection of the lens and mirror optics used in these studies. Of highest interest is the VUV emission during the initial stage of pulsed atmospheric discharges, which has a typical duration in the nanosecond regime. An experiment was designed to study this fast initial stage of VUV emission coupled with fast optical imaging of streamer propagation, both with temporal resolution on the order of nanoseconds. A repetitive solid-state high voltage pulser was constructed which produces triggered flashover discharges with low jitter and consistent pulse amplitude. VUV emission is captured utilizing both photomultiplier and intensified charge-coupled device detectors during the fast stage of streamer propagation. These results are discussed in context with the streamer formation photographed in the visible wavelength regime with 3 ns exposure time. PMID:20815599

Laity, G; Neuber, A; Rogers, G; Frank, K

2010-08-01

22

System for time resolved spectral studies of pulsed atmospheric discharges in the visible to vacuum ultraviolet range  

International Nuclear Information System (INIS)

Vacuum ultraviolet (VUV) emission is believed to play a major role in the development of plasma streamers in pulsed atmospheric discharges, but detection of VUV light is difficult in pulsed experiments at atmospheric pressures. Since VUV light is absorbed in most standard optical materials as well, careful attention must be given to the selection of the lens and mirror optics used in these studies. Of highest interest is the VUV emission during the initial stage of pulsed atmospheric discharges, which has a typical duration in the nanosecond regime. An experiment was designed to study this fast initial stage of VUV emission coupled with fast optical imaging of streamer propagation, both with temporal resolution on the order of nanoseconds. A repetitive solid-state high voltage pulser was constructed which produces triggered flashover discharges with low jitter and consistent pulse amplitude. VUV emission is captured utilizing both photomultiplier and intensified charge-coupled device detectors during the fast stage of streamer propagation. These results are discussed in context with the streamer formation photographed in the visible wavelength regime with 3 ns exposure time.

23

System for time resolved spectral studies of pulsed atmospheric discharges in the visible to vacuum ultraviolet range  

Energy Technology Data Exchange (ETDEWEB)

Vacuum ultraviolet (VUV) emission is believed to play a major role in the development of plasma streamers in pulsed atmospheric discharges, but detection of VUV light is difficult in pulsed experiments at atmospheric pressures. Since VUV light is absorbed in most standard optical materials as well, careful attention must be given to the selection of the lens and mirror optics used in these studies. Of highest interest is the VUV emission during the initial stage of pulsed atmospheric discharges, which has a typical duration in the nanosecond regime. An experiment was designed to study this fast initial stage of VUV emission coupled with fast optical imaging of streamer propagation, both with temporal resolution on the order of nanoseconds. A repetitive solid-state high voltage pulser was constructed which produces triggered flashover discharges with low jitter and consistent pulse amplitude. VUV emission is captured utilizing both photomultiplier and intensified charge-coupled device detectors during the fast stage of streamer propagation. These results are discussed in context with the streamer formation photographed in the visible wavelength regime with 3 ns exposure time.

Laity, G.; Neuber, A.; Rogers, G.; Frank, K. [Department of Electrical and Computer Engineering and Department of Physics, Center for Pulsed Power and Power Electronics, Texas Tech University, Lubbock, Texas 79409 (United States)

2010-08-15

24

System for time resolved spectral studies of pulsed atmospheric discharges in the visible to vacuum ultraviolet range  

Science.gov (United States)

Vacuum ultraviolet (VUV) emission is believed to play a major role in the development of plasma streamers in pulsed atmospheric discharges, but detection of VUV light is difficult in pulsed experiments at atmospheric pressures. Since VUV light is absorbed in most standard optical materials as well, careful attention must be given to the selection of the lens and mirror optics used in these studies. Of highest interest is the VUV emission during the initial stage of pulsed atmospheric discharges, which has a typical duration in the nanosecond regime. An experiment was designed to study this fast initial stage of VUV emission coupled with fast optical imaging of streamer propagation, both with temporal resolution on the order of nanoseconds. A repetitive solid-state high voltage pulser was constructed which produces triggered flashover discharges with low jitter and consistent pulse amplitude. VUV emission is captured utilizing both photomultiplier and intensified charge-coupled device detectors during the fast stage of streamer propagation. These results are discussed in context with the streamer formation photographed in the visible wavelength regime with 3 ns exposure time.

Laity, G.; Neuber, A.; Rogers, G.; Frank, K.

2010-08-01

25

Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula  

Science.gov (United States)

A better understanding of the aerosol radiative properties is a crucial challenge for climate change studies. This study aims to provide a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW) solar spectrum. For this purpose, long-term datasets of aerosol properties from six AERONET stations located in the Iberian Peninsula (Southwestern Europe) are analyzed in term of climatology characterization and trends. Aerosol information is used as input to the libRadtran model in order to determine the aerosol radiative effect at the surface in the ultraviolet (AREUV), visible (AREVIS), near-infrared (ARENIR), and the entire SW range (ARESW) under cloud-free conditions. Over the whole Iberian Peninsula, aerosol radiative effects in the different spectral ranges are: -1.1 < AREUV < -0.7 W m-2, -5.7 < AREVIS < -3.8 W m-2, -2.8 < ARENIR < -1.7 W m-2, and -9.5 < ARESW < -6.1 W m-2. The four variables showed positive statistically significant trends between 2004 and 2012, e.g., ARESW increased +3.6 W m-2 per decade. This fact is linked to the decrease in the aerosol load, which presents a trend of -0.04 per unit of aerosol optical depth at 500 nm per decade, hence a reduction of aerosol effect on solar radiation at the surface is seen. Monthly means of ARE show a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE), ARE per unit of aerosol optical depth, is also evaluated in the four spectral ranges. AFE exhibits a dependence on single scattering albedo and a weaker one on Ångström exponent. AFE is larger (in absolute value) for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency vary with the aerosol types. Aerosol size determines the fractions of AFEVIS/AFESW and AFENIR/AFESW. VIS range is the dominant region for all types, although non-absorbing large particles cause a more equal contribution of VIS and NIR intervals. The AFEUV / AFESW ratio shows a higher contribution for absorbing fine particles.

Mateos, D.; Antón, M.; Toledano, C.; Cachorro, V. E.; Alados-Arboledas, L.; Sorribas, M.; Costa, M. J.; Baldasano, J. M.

2014-04-01

26

Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula  

Directory of Open Access Journals (Sweden)

Full Text Available A better understanding of the aerosol radiative properties is a crucial challenge for climate change studies. This study aims to provide a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW solar spectrum. For this purpose, long-term datasets of aerosol properties from six AERONET stations located in the Iberian Peninsula (Southwestern Europe are analyzed in term of climatology characterization and trends. Aerosol information is used as input to the libRadtran model in order to determine the aerosol radiative effect at the surface in the ultraviolet (AREUV, visible (AREVIS, near-infrared (ARENIR, and the entire SW range (ARESW under cloud-free conditions. Over the whole Iberian Peninsula, aerosol radiative effects in the different spectral ranges are: ?1.1 UV ?2, ?5.7 VIS ?2, ?2.8 NIR ?2, and ?9.5 SW ?2. The four variables showed positive statistically significant trends between 2004 and 2012, e.g., ARESW increased +3.6 W m?2 per decade. This fact is linked to the decrease in the aerosol load, which presents a trend of ?0.04 per unit of aerosol optical depth at 500 nm per decade, hence a reduction of aerosol effect on solar radiation at the surface is seen. Monthly means of ARE show a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE, ARE per unit of aerosol optical depth, is also evaluated in the four spectral ranges. AFE exhibits a dependence on single scattering albedo and a weaker one on Ångström exponent. AFE is larger (in absolute value for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency vary with the aerosol types. Aerosol size determines the fractions of AFEVIS/AFESW and AFENIR/AFESW. VIS range is the dominant region for all types, although non-absorbing large particles cause a more equal contribution of VIS and NIR intervals. The AFEUV / AFESW ratio shows a higher contribution for absorbing fine particles.

D. Mateos

2014-04-01

27

Role of Al coordination in barium phosphate glasses on the emission features of Ho{sup 3+} ion in the visible and IR spectral ranges  

Energy Technology Data Exchange (ETDEWEB)

The glasses of the composition (39-x)BaO-xAl{sub 2}O{sub 3}-60P{sub 2}O{sub 5}:1.0Ho{sub 2}O{sub 3} (in mol%) with x value ranging from 1.0 to 4.0 have been synthesized. The IR spectral studies of these glasses have indicated that there is a gradual transformation of Al{sup 3+} ions from tetrahedral to octahedral with increase in the concentration of Al{sub 2}O{sub 3} up to 3.0 mol%. Optical absorption and fluorescence spectra (in the visible and NIR regions) of these glasses have been recorded at room temperature. The Judd-Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of Ho{sup 3+} ions in these glasses. From the luminescence spectra, various radiative properties like transition probability A, branching ratio beta{sub r}, the radiative lifetime tau{sub r} and emission cross-section sigma{sup E} for various emission levels of these glasses have been evaluated. The radiative lifetime of the {sup 5}S{sub 2}->{sup 5}I{sub 8} (green emission) transition has also been measured. The variations observed in these parameters have been discussed in the light of varying co-ordinations (tetrahedral and octahedral positions) of Al{sup 3+} ions in the glass network. The influence of hydroxyl groups on the luminescence efficiency of the transition {sup 5}S{sub 2}->{sup 5}I{sub 8} has also been discussed. Finally the optimum concentration of Al{sub 2}O{sub 3} for getting maximum luminescence output has also been identified and reported.

Satyanarayana, T.; Kalpana, T.; Ravi Kumar, V. [Department of Physics, Acharya Nagarjuna University-Nuzvid Campus, Nuzvid-521 201, A.P. (India); Veeraiah, N., E-mail: nvr8@rediffmail.co [Department of Physics, Acharya Nagarjuna University-Nuzvid Campus, Nuzvid-521 201, A.P. (India)

2010-03-15

28

Role of Al coordination in barium phosphate glasses on the emission features of Ho3+ ion in the visible and IR spectral ranges  

International Nuclear Information System (INIS)

The glasses of the composition (39-x)BaO-xAl2O3-60P2O5:1.0Ho2O3 (in mol%) with x value ranging from 1.0 to 4.0 have been synthesized. The IR spectral studies of these glasses have indicated that there is a gradual transformation of Al3+ ions from tetrahedral to octahedral with increase in the concentration of Al2O3 up to 3.0 mol%. Optical absorption and fluorescence spectra (in the visible and NIR regions) of these glasses have been recorded at room temperature. The Judd-Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of Ho3+ ions in these glasses. From the luminescence spectra, various radiative properties like transition probability A, branching ratio ?r, the radiative lifetime ?r and emission cross-section ?E for various emission levels of these glasses have been evaluated. The radiative lifetime of the 5S2?5I8 (green emission) transition has also been measured. The variations observed in these parameters have been discussed in the light of varying co-ordinations (tetrahedral and octahedral positions) of Al3+ ions in the glass network. The influence of hydroxyl groups on the luminescence efficiency of the transition 5S2?5I8 has also been discussed. Finally the optimum con discussed. Finally the optimum concentration of Al2O3 for getting maximum luminescence output has also been identified and reported.

29

Proton and electron impact on molecular and atomic oxygen: I. High resolution fluorescence spectra in the visible and VUV spectral range and emission cross-sections for dissociative ionisation and excitation of O2  

International Nuclear Information System (INIS)

For pt.II see ibid., vol.11, p.45-58, 2000. Molecular oxygen O2 was dissociated in collisions with protons and electrons in the intermediate velocity range (p+-energies: 17-800 keV, e--energies: 0.2-2 keV). Fluorescence from excited atomic and singly ionised fragments and from singly ionised molecules was detected in the VUV and in the visible and near UV spectral range. Highly resolved spectra are presented for the VUV (46-131 nm) and the near UV/visible (340-605 nm) spectral range. Absolute emission cross-sections have been determined for dissociative ionisation and excitation leading to fluorescence in the VUV. Results are compared with published data. (orig.)

30

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

31

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

Energy Technology Data Exchange (ETDEWEB)

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{sup (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.

Dusanowski, ?.; Syperek, M.; S?k, G.; Misiewicz, J. [Institute of Physics, Wroc?aw University of Technology, 50-370 Wroc?aw (Poland); Golnik, A.; Suffczy?ski, J.; Nawrocki, M. [Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 00-681 Warsaw (Poland); Schlereth, T. W.; Schneider, C.; Höfling, S.; Kamp, M.; Forchel, A. [Technische Physik, Universität Würzburg, Am Hubland, D-97074 Würzburg (Germany)

2013-12-04

32

Electromagnetic cloaking in the visible frequency range  

CERN Document Server

Electromagnetic metamaterials provide unprecedented freedom and flexibility to introduce new devices, which control electromagnetic wave propagation in very unusual ways. Very recently theoretical design of an "invisibility cloak" has been suggested, which has been realized at microwave frequencies in a two-dimensional cylindrical geometry. In this communication we report on the experimental realization of the dielectric permittivity distribution required for non-magnetic cloaking in the visible frequency range.

Smolyaninov, I I; Davis, C C

2007-01-01

33

Coloring elimination in Sr1 - x Ce x F2 + x crystals in the visible spectral range during growth from melt  

Science.gov (United States)

Crystals of the Sr1 - x Ce x F2 + x compositions close to the congruent one ( x ˜ 0.3) are fabricated by the vertical directional crystallization. It is shown that the use of CF4 to form a fluorinating atmosphere during growth leads to additional spurious absorption in the crystals in the range 350-600 nm. The use of PbF2 and ZnF2 for fluorination makes it possible to obtain colorless Sr1 - x Ce x F2 + x crystals of the desired optical quality from melt. The thermal conductivity of crystal with x ˜ 0.28 in the temperature range 80-500 K lies within 1.50 ± 0.03 W m-1 K-1. High ionic conductivity makes the Sr1 - x Ce x F2 + x crystals promising for application in solid-state ionics.

Karimov, D. N.; Ivanovskaya, N. A.; Samsonova, N. V.; Sorokin, N. I.; Sobolev, B. P.; Popov, P. A.

2013-09-01

34

Decomposing numerical ranges along with spectral sets  

CERN Document Server

This note is to indicate the new sphere of applicability of the method developed by Mlak as well as by the author. Restoring those ideas is summoned by current developments concerning $K$-spectral sets on numerical ranges.

Szafraniec, F H

2009-01-01

35

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.

J. Chmiel

1995-06-01

36

[Visible-NIR spectral feature of citrus greening disease].  

Science.gov (United States)

Citrus greening (Huanglongbing, or HLB) is a devastating disease caused by Candidatus liberibacter which uses psyllids as vectors. It has no cure till now, and poses a huge threat to citrus industry around the world. In order to diagnose, assess and further control this disease, it is of great importance to first find a quick and effective way to detect it. Spectroscopy method, which was widely considered as a fast and nondestructive way, was adopted here to conduct a preliminary exploration of disease characteristics. In order to explore the spectral differences between the healthy and HLB infected leaves and canopies, this study measured the visible-NIR spectral reflectance of their leaves and canopies under lab and field conditions, respectively. The original spectral data were firstly preprocessed with smoothing (or moving average) and cluster average procedures, and then the first derivatives were also calculated to determine the red edge position (REP). In order to solve the multi-peak phenomenon problem, two interpolation methods (three-point Lagrangian interpolation and four-point linear extrapolation) were adopted to calculate the REP for each sample. The results showed that there were, obvious differences at the visible & NIR spectral reflectance between the healthy and HLB infected classes. Comparing with the healthy reflectance, the HLB reflectance was higher at the visible bands because of the yellowish symptoms on the infected leaves, and lower at NIR bands because the disease blocked water transportation to leaves. But the feature at NIR bands was easily affected by environmental factors such as light, background, etc. The REP was also a potential indicator to distinguish those two classes. The average REP was slowly moving toward red bands while the infection level was getting higher. The gap of the average REPs between the healthy and HLB classes reached to a maximum of 20 nm. Even in the dataset with relatively lower variation, the classification accuracy of threshold segmentation method by the REP could reach to more than 90%. The four-point linear extrapolation method had slightly better result than the three-point Lagrangian interpolation method. This study provided useful theoretical foundation to detect HLB by spectral reflectance. PMID:25358163

Li, Xiu-hua; Li, Min-zan; Won Suk, Lee; Reza, Ehsani; Ashish, Ratn Mishra

2014-06-01

37

Brightness Control in Dynamic Range Constrained Visible Light OFDM Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2013-01-01

38

A database of high dynamic range visible and near-infrared multispectral images  

Science.gov (United States)

Simulation of the imaging pipeline is an important tool for the design and evaluation of imaging systems. One of the most important requirements for an accurate simulation tool is the availability of high quality source scenes. The dynamic range of images depends on multiple elements in the imaging pipeline including the sensor, digital signal processor, display device, etc. High dynamic range (HDR) scene spectral information is critical for an accurate analysis of the effect of these elements on the dynamic range of the displayed image. Also, typical digital imaging sensors are sensitive well beyond the visible range of wavelengths. Spectral information with support across the sensitivity range of the imaging sensor is required for the analysis and design of imaging pipeline elements that are affected by IR energy. Although HDR scene data information with visible and infrared content are available from remote sensing resources, there are scarcity of such imagery representing more conventional everyday scenes. In this paper, we address both these issues and present a method to generate a database of HDR images that represent radiance fields in the visible and near-IR range of the spectrum. The proposed method only uses conventional consumer-grade equipment and is very cost-effective.

Parmar, Manu; Imai, Francisco; Park, Sung Ho; Farrell, Joyce

2008-02-01

39

Wide range excitation of visible luminescence in nanosilica  

Science.gov (United States)

The visible luminescence of nanometer-sized silica particles (7 nm mean diameter) was investigated using time resolved spectroscopy. This luminescence is characterized by a wide excitation in the visible and ultraviolet range. The emission spectrum is centred at 2.72 eV with a full width at half maximum of 0.70 eV when excited above 3.5 eV, whereas it progressively empties on the high energy side when excited below 3.5 eV. Moreover, the lifetime falls in the ns timescale and decreases on increasing the emission energy. These features are due to the exceptionally broad inhomogeneous distribution of the emitting centres peculiar to the silica nanoparticles.

Vaccaro, L.; Vaccaro, G.; Agnello, S.; Buscarino, G.; Cannas, M.

2010-12-01

40

The refractive index of human hemoglobin in the visible range  

Energy Technology Data Exchange (ETDEWEB)

Because the refractive index of hemoglobin in the visible range is sensitive to the hemoglobin concentration, optical investigations of hemoglobin are important for medical diagnostics and treatment. Direct measurements of the refractive index are, however, challenging; few such measurements have previously been reported, especially in a wide wavelength range. We directly measured the refractive index of human deoxygenated and oxygenated hemoglobin for nine wavelengths between 400 and 700 nm for the hemoglobin concentrations up to 140 g l{sup -1}. This paper analyzes the results and suggests a set of model functions to calculate the refractive index depending on the concentration. At all wavelengths, the measured values of the refractive index depended on the concentration linearly. Analyzing the slope of the lines, we determined the specific refraction increments, derived a set of model functions for the refractive index depending on the concentration, and compared our results with those available in the literature. Based on the model functions, we further calculated the refractive index at the physiological concentration within the erythrocytes of 320 g l{sup -1}. The results can be used to calculate the refractive index in the visible range for arbitrary concentrations provided that the refractive indices depend on the concentration linearly.

Zhernovaya, O; Tuchin, V [International Research-Educational Center of Optical Technologies for Industry and Medicine ' Photonics' , Saratov State University, 83 Astrakhanskaya str., 410012 Saratov (Russian Federation); Sydoruk, O [Optical and Semiconductor Devices Group, Department of Electrical and Electronic Engineering, South Kensington Campus, Imperial College London, London SW7 2AZ (United Kingdom); Douplik, A, E-mail: alexandre.douplik@aot.uni-erlangen.de [Medical Photonics Engineering Group, Chair of Photonic Technologies, Friedrich-Alexander University Erlangen-Nuremberg, Paul-Gordan-Strasse 3, 91052 Erlangen (Germany)

2011-07-07

 
 
 
 
41

Towards isotropic negative magnetics in the visible range  

CERN Document Server

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.

Simovski, C R

2008-01-01

42

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

International Nuclear Information System (INIS)

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 ?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)

43

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

44

New fractal structures for frequencies close to the visible range  

DEFF Research Database (Denmark)

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.

Malureanu, Radu; Andryieuski, Andrei

2011-01-01

45

Highly efficient broadband sum-frequency generation in the visible wavelength range.  

Science.gov (United States)

We report on efficient broadband sum-frequency generation, converting a 140 THz near-infrared bandwidth to the visible regime with photon conversion efficiency greater than 90%. Using a 20-mm-long aperiodically adiabatively poled KTP crystal, the spectral range 660-990 nm was converted to 405-500 nm using a strong pump wave at 1030 nm. The photon conversion efficiency was confirmed to be 92±0.5% when pumped with an intensity of 0.94??GW/cm2. Our experimental results agreed very well with analytic predictions and numerical simulations. PMID:24978235

Cankaya, Huseyin; Calendron, Anne-Laure; Suchowski, Haim; Kärtner, Franz X

2014-05-15

46

Visible and near infrared fluorescence spectral flow cytometry.  

Science.gov (United States)

There is a long standing interest in measuring complete emission spectra from individual cells in flow cytometry. We have developed flow cytometry instruments and analysis approaches to enable this to be done routinely and robustly. Our spectral flow cytometers use a holographic grating to disperse light from single cells onto a CCD for high speed, wavelength-resolved detection. Customized software allows the single cell spectral data to be displayed and analyzed to produce new spectra-derived parameters. We show that familiar reference and calibration beads can be employed to quantitatively assess instrument performance. We use microspheres stained with six different quantum dots to compare a virtual bandpass filter approach with classic least squares (CLS) spectral unmixing, and then use antibody capture beads and CLS unmixing to demonstrate immunophenotyping of peripheral blood mononuclear cells using spectral flow cytometry. Finally, we characterize and evaluate several near infrared (NIR) emitting fluorophores for use in spectral flow cytometry. Spectral flow cytometry offers a number of attractive features for single cell analysis, including a simplified optical path, high spectral resolution, and streamlined approaches to quantitative multiparameter measurements. The availability of robust instrumentation, software, and analysis approaches will facilitate the development of spectral flow cytometry applications. PMID:23225549

Nolan, John P; Condello, Danilo; Duggan, Erika; Naivar, Mark; Novo, David

2013-03-01

47

Wide-spectral-range laser refractometer.  

Science.gov (United States)

We present refractometric measurements made in the 266-1064-nm spectral region with a pulsed Nd:YAG laser, and the second, third, and fourth harmonics of the laser's fundamental wavelength. The critical angle is determined by the disappearance of the diffraction orders from a metal grating, forming a microcuvette with the prism's reflecting wall. A fused-silica measuring prism is used in the experiments. PMID:12737464

Sainov, Simeon; Sarov, Yanko; Kurtev, Stoyan

2003-05-01

48

Ultraviolet and visible range plasmonics of a topological insulator  

CERN Document Server

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...

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

2014-01-01

49

INVITED PAPER: Investigation into the ways of tuning parametric oscillators of visible and IR ranges  

Science.gov (United States)

Different versions of optical parametric oscillator (OPO) schemes were experimentally realised and investigated, which utilise AgGaS2, LiNbO3 and HgGa2S4 single crystals as well as an Hg1-xCdxGa2S4 solid solution. The OPOs generate radiation in the 1.2-5.7-?m range and make use of different ways of output wavelength tuning, including fast wavelength tuning (in a time shorter than 0.1 ms) with the help of an acoustooptical deflector. The output spectral line was narrowed by means of an intracavity acoustooptical filter. An OPO for the visible range with an electrodynamic tuning to an arbitrary wavelength in this range in a time of 5ms was implemented employing a BBO single crystal.

Andreev, S. A.; Andreeva, N. P.; Barashkov, M. S.; Badikov, Valerii V.; Demkin, V. K.; Don, A. K.; Epikhin, V. M.; Krymskii, M. I.; Kalinnikov, Yu K.; Mitin, Konstantin V.; Seregin, A. M.; Sinaiskii, V. V.; Talalaev, M. A.; Chistyakov, A. A.; Shchebetova, N. I.; Shchetinkina, T. A.

2010-06-01

50

Spectral Methodology for the Rapid Discrimination of Kimberlite Indicator Minerals using Reflected Light in the Visible Spectral Region  

Science.gov (United States)

Exploration methods for potentially diamond bearing kimberlites involve the analysis for specific transition metals within mantle related indicator minerals using electron microprobe. The chemistry of each indicator mineral is characterized primarily on the basis of the transition metal geochemistry. These transition metals included within the grains crystal lattice produce absorption bands at specific wavelengths in the visible spectral region. Reflection spectra of kimberlite indicator minerals (pyrope garnet, chrome diopside) as well as genetically related minerals (almandine, uvarovite) have been examined. Laboratory spectra of each grain have been measured in 5 orientations in the 380 - 900 nm range. Preliminary data has suggested that: 1) First series transition metals (Fe, Mn, Cr, etc.) are evident within the spectrum of each grain as absorption bands each varying in depth, width and slope according to molecular proportions. 2) The absorption band at 690nm can be used to determine the approximate molar chromium contents of the pyrope, almandine and uvarovite phases of garnet. 3) Spectra in all 5 orientations are consistent in band depth, width and slope indicating that only one or two measurements are required for accurate results. 4) Measurements in each orientation take only a few seconds which allows for rapid identification of relevant kimberlite indicator minerals. The composition of each grain will be determined using electron microprobe and micro XRD equipment. The results will then be compared to absorption band depths and widths to determine how much of a transition metal such as chromium is necessary to intensify the spectral feature.

McMahon, M. J.; Budkewitsch, P.; Fueten, F.

2009-12-01

51

A Spectral Learning Approach to Range-Only SLAM  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a novel spectral learning algorithm for simultaneous localization and mapping (SLAM) from range data with known correspondences. This algorithm is an instance of a general spectral system identification framework, from which it inherits several desirable properties, including statistical consistency and no local optima. Compared with popular batch optimization or multiple-hypothesis tracking (MHT) methods for range-only SLAM, our spectral approach offers guarantee...

Boots, Byron; Gordon, Geoffrey J.

2012-01-01

52

Spectral Aging Model Applied to Meteosat First Generation Visible Band  

Directory of Open Access Journals (Sweden)

Full Text Available The Meteosat satellites have been operational since the early eighties, creating so far a continuous time period of observations of more than 30 years. In order to use this data for climate data records, a consistent calibration is necessary between the consecutive instruments. Studies have shown that the Meteosat First Generation (MFG satellites (1982–2006 suffer from in-flight degradation which is spectral of nature and is not corrected by the official calibration of EUMETSAT. Continuing on previous published work by the same authors, this paper applies the spectral aging model to a set of clear-sky and cloudy targets, and derives the model parameters for all six MFG satellites (Meteosat-2 to -7. Several problems have been encountered, both due to the instrument and due to geophysical occurrences, and these are discussed and illustrated here in detail. The paper shows how the spectral aging model is an improvement compared to the EUMETSAT calibration method with a stability of 1%–2% for Meteosat-4 to -7, which increases up to 6% for ocean sites using the full MFG time period.

Ilse Decoster

2014-03-01

53

Refined approximations for the distortion visibility function and mu-type spectral distortions  

CERN Document Server

The physical processes affecting the thermalization of cosmic microwave background spectral distortions are very simple and well understood. This allows us to make precise predictions for the distortions signals caused by various energy release scenarios, where the theoretical uncertainty is largely dominated by the physical ingredients that are used for the calculation. Here, we revisit various approximations for the distortion visibility function -- defined using the fraction of the released energy that does not thermalize -- and early $\\mu$-type distortions. Our approach is based on a perturbative expansion, which allows us to identify and clarify the origin of different improvements over earlier approximations. It provides a better than ~0.1%-1% description of our numerical results over a wide range of parameters. In particular, we are able to capture the high-frequency part of the mu-distortion, which directly depends on the time-derivative of the electron temperature. We also include lowest order double...

Chluba, Jens

2013-01-01

54

Spectral long-range interaction of temporal incoherent solitons.  

Science.gov (United States)

We study the interaction of temporal incoherent solitons sustained by a highly noninstantaneous (Raman-like) nonlinear response. The incoherent solitons exhibit a nonmutual interaction, which can be either attractive or repulsive depending on their relative initial distance. The analysis reveals that incoherent solitons exhibit a long-range interaction in frequency space, which is in contrast with the expected spectral short-range interaction described by the usual approach based on the Raman-like spectral gain curve. Both phenomena of anomalous interaction and spectral long-range behavior of incoherent solitons are described in detail by a long-range Vlasov equation. PMID:24487873

Xu, Gang; Garnier, Josselin; Picozzi, Antonio

2014-02-01

55

Passive ranging of dynamic rocket plumes using infrared and visible oxygen attenuation  

Science.gov (United States)

Atmospheric oxygen absorption bands in observed spectra of boost phase missiles can be used to accurately estimate range from sensor to target. One method is to compare observed values of band averaged absorption to radiative transfer models. This is most effective using bands where there is a single absorbing species. This work compares spectral attenuation of two oxygen absorption bands in the near-infrared (NIR) and visible (Vis) spectrum, centered at 762 nm and 690 nm, to passively determine range. Spectra were observed from a static test of a full-scale solid rocket motor at a 900m range. The NIR O2 band provided range estimates accurate to within 3%, while the Vis O2 band had a range error of 15%. A Falcon 9 rocket launch at an initial range of 13km was also tracked and observed for 90 seconds after ignition. The NIR O2 band provided in-flight range estimates accurate to within 2% error for the first 30 seconds of tracked observation. The Vis O2 band also provided accurate range estimates with an error of approximately 4%. Rocket plumes are expected to be significantly brighter at longer wavelengths, but absorption in the NIR band is nearly ten times stronger than the Vis band, causing saturation at shorter path lengths. An atmospheric band is considered saturated when all the in-band frequencies emitted from the rocket plume are absorbed before reaching the sensor.

Vincent, R. Anthony; Hawks, Michael R.

2011-05-01

56

A Wide Spectral Range Reflectance and Luminescence Imaging System  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we introduce a wide spectral range (200–2500 nm imaging system with a 250 ?m minimum spatial resolution, which can be freely modified for a wide range of resolutions and measurement geometries. The system has been tested for reflectance and luminescence measurements, but can also be customized for transmittance measurements. This study includes the performance results of the developed system, as well as examples of spectral images. Discussion of the system relates it to existing systems and methods. The wide range spectral imaging system that has been developed is however highly customizable and has great potential in many practical applications.

Tapani Hirvonen

2013-10-01

57

Refined approximations for the distortion visibility function and ?-type spectral distortions  

Science.gov (United States)

The physical processes affecting the thermalization of cosmic microwave background spectral distortions are very simple and well understood. This allows us to make precise predictions for the distortions signals caused by various energy release scenarios, where the theoretical uncertainty is largely dominated by the physical ingredients that are used for the calculation. Here, we revisit various approximations for the distortion visibility function - defined using the fraction of the released energy that does not thermalize - and early ?-type distortions. Our approach is based on a perturbative expansion, which allows us to identify and clarify the origin of different improvements over earlier approximations. It provides a better than ?0.1-1 per cent description of our numerical results over a wide range of parameters. In particular, we are able to capture the high-frequency part of the ?-distortion, which directly depends on the time derivative of the electron temperature. We also include lowest order double Compton and Compton scattering relativistic corrections, finding that because of cancellation they increase the thermalization efficiency in the tail of the distortion visibility function by only ?10 per cent (at z ? 6 × 106), although individually their effect can reach ?20-40 per cent.

Chluba, J.

2014-05-01

58

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

Energy Technology Data Exchange (ETDEWEB)

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)

Aristov, A I; Grudtsyn, Ya V; Mikheev, L D; Polivin, A V; Stepanov, S G; Trofimov, V A; Yalovoi, V I

2012-12-31

59

Application of spectral derivative data in visible and near-infrared spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

The use of the spectral derivative method in visible and near-infrared optical spectroscopy is presented, whereby instead of using discrete measurements around several wavelengths, the difference between nearest neighbouring spectral measurements is utilized. The proposed technique is shown to be insensitive to the unknown tissue and fibre contact coupling coefficients providing substantially increased accuracy as compared to more conventional techniques. The self-calibrating nature of the spectral derivative techniques increases its robustness for both clinical and industrial applications, as is demonstrated based on simulated results as well as experimental data.

Dehghani, Hamid [School of Computer Science, University of Birmingham, Birmingham B15 2TT (United Kingdom); Leblond, Frederic; Pogue, Brian W [Thayer School of Engineering, Dartmouth College, NH 03755 (United States); Chauchard, Fabien, E-mail: h.dehghani@cs.bham.ac.u [Indatech, 385 Avenues des Baronnes, Prades Le Lez (France)

2010-06-21

60

Application of spectral derivative data in visible and near-infrared spectroscopy  

International Nuclear Information System (INIS)

The use of the spectral derivative method in visible and near-infrared optical spectroscopy is presented, whereby instead of using discrete measurements around several wavelengths, the difference between nearest neighbouring spectral measurements is utilized. The proposed technique is shown to be insensitive to the unknown tissue and fibre contact coupling coefficients providing substantially increased accuracy as compared to more conventional techniques. The self-calibrating nature of the spectral derivative techniques increases its robustness for both clinical and industrial applications, as is demonstrated based on simulated results as well as experimental data.

 
 
 
 
61

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

62

Lunar Resources Using Moderate Spectral Resolution Visible and Near-infrared Spectroscopy: Al/si and Soil Maturity  

Science.gov (United States)

Modern visible and near-infrared detectors are critically important for the accurate identification and relative abundance measurement of lunar minerals; however, even a very small number of well-placed visible and near-infrared bandpass channels provide a significant amount of general information about crucial lunar resources. The Galileo Solid State Imaging system (SSI) multispectral data are an important example of this. Al/Si and soil maturity will be discussed as examples of significant general lunar resource information that can be gleaned from moderate spectral resolution visible and near-infrared data with relative ease. Because quantitative-albedo data are necessary for these kinds of analyses, data such as those obtained by Galileo SSI are critical. SSI obtained synoptic digital multispectral image data for both the nearside and farside of the Moon during the first Galileo Earth-Moon encounter in December 1990. The data consist of images through seven filters with bandpasses ranging from 0.40 microns in the ultraviolet to 0.99 microns in the near-infrared. Although these data are of moderate spectral resolution, they still provide information for the following lunar resources: (1) titanium content of mature mare soils based upon the 0.40/0.56-micron (UV/VIS) ratio; (2) mafic mineral abundance based upon the 0.76/0.99-micron ratio; and (3) the maturity or exposure age of the soils based upon the 0.56-0.76-micron continuum and the 0.76/0.99-micron ratio. Within constraints, these moderate spectral resolution visible and near-infrared reflectance data can also provide elemental information such as Al/Si for mature highland soils.

Fischer, Erich M.; Pieters, Carle M.; Head, James W.

1992-01-01

63

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

CERN Document Server

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- ...

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

2014-01-01

64

Full-range spectral domain Doppler optical coherence tomography  

Science.gov (United States)

Spectral domain optical coherence tomography (SD-OCT) systems achieve higher sensitivities compared to time domain OCT systems. However, one of the main challenges in SD-OCT is the obscuring object structure called "ghost image" or "mirror image" that arises from the Fourier transform of a real function. We have designed and developed a phaseshifting- based full-range SD-OCT system that we refer to as the dual detection full range SD-OCT. The proposed technique simultaneously obtains the quadrature components of a complex spectral interference. Therefore, the technique enables full range imaging without any loss of speed and is intrinsically less sensitive to movements of the subject. In this paper, we demonstrate that the dual detection technique can be applied to Doppler imaging without loss in the velocity dynamic range since the phase information of the acquired spectra is preserved. The dual detection full range SD-OCT provides a superior signal-to-noise ratio over a conventional SD-OCT since the most sensitive region around the zero path delay is usable. This capability improves the image quality of not only the structural image but also the Doppler image.

Meemon, P.; Lee, K. S.; Rolland, J. P.

2010-02-01

65

Polarized spectral properties of Sm3+:LiLuF4 crystal for visible laser application  

Science.gov (United States)

A Sm3+-doped LiLuF4 single crystal was grown by the vertical Bridgman-Stockbarge technique. Polarized absorption spectra, polarized fluorescence spectra, and fluorescence lifetime of the Sm3+:LiLuF4 crystal were recorded at room temperature. Based on the Judd-Ofelt theory, spectral parameters of the Sm3+:LiLuF4 crystal were calculated. Emission cross sections for the 4G5/2 ? 6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions with special interest for visible laser application were obtained by the Füchtbauer-Ladenburg formula. The results indicate that the Sm3+:LiLuF4 crystal may be a potential laser gain medium operating in visible region pumped by diode lasers around 401 nm.

Wang, G. Q.; Gong, X. H.; Lin, Y. F.; Chen, Y. J.; Huang, J. H.; Luo, Z. D.; Huang, Y. D.

2014-11-01

66

Spectrograms of the visible region in the JT-60 tokamak (wavelength range from 2210 A to 5250 A)  

International Nuclear Information System (INIS)

In order to obtain the basically spectroscopic data for the investigation of impurity behavior in JT-60 tokamak, the spectrographic measurement of the visible spectral lines in ohmically heated plasma were performed by 0.5 m Czerny-Turner type spectrometer which covered the wave length range from 2210 A to 5250 A. The low ionized spectral lines of oxygen and carbon up to four times, titanium up to three times, and chromium and nickel up to one times were observed. And also two forbidden lines of highly ionized titanium (Ti XVII 3834.4 A, Ti XIX 2344.6 A) which were useful for the measurement of titanium density, local ion temperature and plasma rotation were identified. (author)

67

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.)

68

Experimental demonstration of a broadband array of invisibility cloaks in the visible frequency range  

Science.gov (United States)

Since the first experimental demonstration in the microwave and visible ranges, invisibility cloaks stimulated considerable progress in the fields of metamaterials and transformation optics. Arrays of invisibility cloaks may find important applications in low-interference communication, noninvasive probing, sensing and communication networks, etc. We report on the first experimental realization of such an array of broadband invisibility cloaks, which operates in the visible frequency range. Wavelength and angular dependencies of the cloak array performance will be demonstrated. Potential biochemical sensing applications will be discussed.

Smolyaninova, Vera; Smolyaninov, Igor; Ermer, Kurt

2013-03-01

69

Design and fabrication of an ultraviolet-visible coded aperture snapshot spectral imager  

Science.gov (United States)

We describe the design and performance of a coded aperture spectral imager with a wide spectral range of 320 to 700 nm over 87 channels and 1988-by-1988 pixels of spatial resolution. A custom-designed relay lens was designed and built for the system, including a dispersive prism element in the collimated space of the relay lens. The optical design process, prescription, and performance are reported for the entire system, including calibration and alignment. Simulations of high-resolution spectral images are conducted to verify the reconstruction algorithm and relative resolution of the instrument compared to ground truth data. Measured data were taken with the instrument using both a random coded aperture and standard slit for spatial resolution comparisons. Finally, reconstructed spectral images from the instrument are presented of a sunlight-illuminated flower from 360 to 700 nm.

Kittle, David S.; Marks, Daniel L.; Brady, David J.

2012-07-01

70

Continuum radiation of the upper atmosphere in the visible and the near infrared ranges of the spectrum  

Science.gov (United States)

On the basis of the analysis of the airglow measurement data obtained by various geophysical stations located in different parts of the globe and the orbital space station "Mir", research of features of characteristics of continuous spectral distribution of intensity (continuum) of radiation and regularities of its variations for various heliogeophysical conditions was performed. Necessity of this similar research is caused by the large integrated intensity of the continuum radiating of the upper atmosphere which is comparable with integrated radiation of the stellar component in the visible region of the spectrum, despite of small spectral density of the continuum radiation. Systematization of data and their subsequent processing and analysis have revealed a broad continuum emission peak near 600 nm. The intensity of this maximum on the average is 10-15 Rayleigh nm-1. In the ultraviolet and infrared spectral ranges the continuum emission intensity decrease was revealed. Empirical regularities of variations of intensity of the continuum, features of its spectral distribution and the altitude distribution of the continuum intensity at heights of the mesopause and lower thermosphere were obtained. The work is supported by RFBR Grant 13-05-00108.

Semenov, Anatoly; Medvedeva, Irina; Shefov, Nikolay; Sidash, Valentina

71

Anomalous aggregation growth of palladium nanosphere with SPR band in visible range  

International Nuclear Information System (INIS)

The morphology and properties of nanostructures are significantly influenced by the chemical coordination during their growth procedure. Using small molecule N-vinyl pyrolidone as stabilizer, this paper introduces a new strategy for synthesis of palladium nanospheres, which has a novel surface plasmon resonance band in the visible range. An aggregation growth mode was observed in the growth process. More specifically, the growth rate increases with increasing concentration of stabilizer. The absorption in visible region suggests new optical applications for these Pd nanospheres, such as photocatalysis, photothermal heating and surface enhanced Raman scattering

72

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

Science.gov (United States)

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.

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

2010-04-01

73

Wide-range optical spin orientation in Ge from near-infrared to visible light  

Science.gov (United States)

Ge-based spin-photodiodes have been employed to investigate the spectral dependence of optical spin orientation in germanium, in the range 400-1550 nm. We found the expected maximum in the spin polarization of photocarriers for excitation at the direct gap in ? (1550 nm) and a second sizable peak due to photogeneration in the L valleys (530 nm). Data suggest distinct spin depolarization mechanisms for excitation at ? and L, with shorter spin relaxation times whether the X point is involved. These devices can be used as integrated photon-helicity detectors over a wide spectral range.

Rinaldi, C.; Cantoni, M.; Marangoni, M.; Manzoni, C.; Cerullo, G.; Bertacco, R.

2014-10-01

74

On mimicking diffuse reflectance spectra in the visible and near-infrared ranges for tissue-like phantom design  

Science.gov (United States)

A novel methodology is presented to mimic diffuse reflectance spectra of arbitrary biological tissues in the visible and near-infrared ranges. The prerequisite for this method is that the spectral information of basic components is sufficient to mimic an arbitrary tissue. Using a sterile disposable fiber optic probe the diffuse reflectance spectrum of a tissue (either in vivo or ex vivo) is measured, which forms the target spectrum. With the same type of fiber probe, a wide variety of basic components (ingredients) has been previously measured and all together forms a spectral database. A "recipe" for the optimal mixture of ingredients can then be derived using an algorithm that fits the absorption and scattering behavior of the target spectrum using the spectra of the basic components in the database. The spectral mimicking accuracy refines by adding more ingredients to the database. The validity of the principle is demonstrated by mimicking an arbitrary mixture of components. The method can be applied with different kinds of materials, e.g. gelatins, waxes and silicones, thus providing the possibility of mimicking the mechanical properties of target tissues as well. The algorithm can be extended from single point contact spectral measurement to contactless multi- and hyper-spectral camera acquisition. It can be applied to produce portable and durable tissue-like phantoms that provides consistent results over time for calibration, demonstration, comparison of instruments or other such tasks. They are also more readily available than living tissue or a cadaver and are not so limited by ease of handling and legislation; hence they are highly useful when developing new devices.

Debernardi, N.; Dunias, P.; van El, B.; Statham, A. E.

2014-03-01

75

Effect of Aerosols on Ultraviolet and Visible Spectral Irradiance at Barrow, Alaska  

Science.gov (United States)

Solar ultraviolet (UV) and visible irradiance has been measured with a spectroradiometer at Barrow, Alaska, (71° N) since 1991. The instrument is part of the National Science Foundation's Arctic Observing Network and measures downwelling spectral irradiance between 280 and 600 nm with a resolution of 1 nm. Data are correlated with aerosol optical depth (AOD) measurements performed with a Carter-Scott sunphotometer that is operated by NOAA's Global Monitoring Division (GMD) at Barrow. In addition, data from a Cimel sunphotometer are used. This instrument is part of NASA's AERONET network and located at Barrow's Atmospheric Radiation Measurement (ARM) Climate Research Facility operated by the U.S. Department of Energy (DOE). Intensive aerosol properties such as aerosol single scattering albedo and asymmetry parameter are used from AERONET almucantar retrievals and in-situ measurements provided by GMD. Sources of aerosols for times of high AOD are determined with back-trajectory calculations. The effect of the various aerosol parameters on cloud-free irradiance measurements is quantified with radiative transfer calculations using the libRadtran/UVSPEC model. Results indicate that aerosols reduce UV and visible irradiance by typically 5% with maximum reductions of up to 20%. The aerosol effect is more pronounced in spring when Arctic haze events are frequent.

Bernhard, G. H.; Stone, R.; Jefferson, A.; Wagener, R.; Frederick, J. E.

2013-12-01

76

Blackbody radiation sources for the IR spectral range  

Science.gov (United States)

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.

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

2013-09-01

77

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

78

Study of impurity radiation in ASDEX Upgrade with a spatially scanning spectrometer for the VUV and visible ranges  

International Nuclear Information System (INIS)

A combined visible and vacuum ultraviolet (VUV) scanning spectrometer for the investigation of the boundary layer of ASDEX Upgrade has been developed. A rotating mirror is used for poloidal scanning. This mirror can be tilted perpendicular to its rotation axis, enabling observation in the toroidal direction too. The broad spectral range opens a variety of investigation possibilities. Here we present poloidal radiation profiles of different ion species in the VUV. Regions of special interest such as the divertor for target erosion studies and the upper boundary for the estimation of ion penetration depths were investigated with high spatial resolution. Additionally, the application of this instrument is shown for measuring the spatial distributions of impurities injected for radiation cooling. (orig.)

79

Spectral anisotropy of solar wind turbulence in the inertial range and dissipation range  

International Nuclear Information System (INIS)

Wavelet analysis is a tool that can simultaneously analyze spacecraft data in both time and frequency. This enables the magnetic energy spectrum (trace spectrum) to be measured for different angles between the local mean magnetic field B0 and the direction of the mean flow within a single data set. Examples obtained around solar minimum using Ulysses data at high latitudes and Stereo data for high-speed streams in the ecliptic plane show that the spectral exponent in the inertial range varies nearly monotonically from approximately 1.6 when B0 is perpendicular to the flow to 2.0 when B0 is parallel to the flow, roughly consistent with anisotropic theories of incompressible MHD turbulence. This and other new information about the 3D wavector spectrum of solar wind fluctuations in the inertial range and the dissipation range are briefly discussed.

80

Spectral Weight Oracle: Model-Independent Sum Rule Analysis Based on Limited-Range Spectral Data  

Science.gov (United States)

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 ellipsometry in optics or simultaneous measurement of attenuation and speed of sound in acoustics, allow an extrapolation-independent determination of spectral weight 'hidden' below the lowest accessible frequency.

Kuzmenko, Alexey; van der Marel, Dirk; Carbone, Fabrizio; Marsiglio, Frank

2007-03-01

 
 
 
 
81

A visibility matching tone reproduction operator for high dynamic range scenes  

Energy Technology Data Exchange (ETDEWEB)

The authors present a tone reproduction operator that preserves visibility in high dynamic range scenes. The method introduces a new histogram adjustment technique, based on the population of local adaptation luminances in a scene. To match subjective viewing experience, the method incorporates models for human contrast sensitivity, glare, spatial acuity and color sensitivity. They compare the results to previous work and present examples the techniques applied to lighting simulation and electronic photography.

Larson, G.W. [Lawrence Berkeley National Lab., CA (United States); Rushmeier, H. [International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center; Piatko, C. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1997-01-15

82

A feasibility study for the retrieval of the total column precipitable water vapor from satellite observations in the blue spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available We present a new algorithm for satellite retrievals of the atmospheric water vapor column in the blue spectral range. The water vapor absorption cross section in the blue spectral range is much weaker than in the red spectral range. Thus the detection limit and the uncertainty of individual observations is systematically larger than for retrievals at longer wavelengths. Nevertheless, water vapor retrievals in the blue spectral range have also several advantages: since the surface albedo in the blue spectral range is similar over land and ocean, water vapor retrievals are more consistent than for longer wavelengths. Compared to retrievals at longer wavelengths, over ocean the sensitivity for atmospheric layers close to the surface is higher due to the (typically 2 to 3 times higher ocean albedo in the blue. Water vapor retrievals in the blue spectral range are also possible for satellite sensors, which do not measure at longer wavelengths of the visible spectral range like the Ozone Monitoring instrument (OMI. We investigated details of the water vapor retrieval in the blue spectral range based on radiative transfer simulations and observations from the Global Ozone Monitoring Experiment 2 (GOME-2 and OMI. It is demonstrated that it is possible to retrieve the atmospheric water vapor column density in the blue spectral range over most parts of the globe. The findings of our study are of importance also for future satellite missions like e.g. Sentinel 4 and 5.

T. Wagner

2013-04-01

83

A feasibility study for the retrieval of the total column precipitable water vapour from satellite observations in the blue spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available We present a new algorithm for satellite retrievals of the atmospheric water vapour column in the blue spectral range. The water vapour absorption cross section in the blue spectral range is much weaker than in the red spectral range. Thus the detection limit and the uncertainty of individual observations are systematically larger than for retrievals at longer wavelengths. Nevertheless, water vapour retrievals in the blue spectral range have also several advantages: since the surface albedo in the blue spectral range is similar over land and ocean, water vapour retrievals are more consistent than for longer wavelengths. Compared to retrievals at longer wavelengths, the sensitivity for atmospheric layers close to the surface is higher due to the (typically 2 to 3 times higher ocean albedo in the blue. Water vapour retrievals in the blue spectral range are also possible for satellite sensors, which do not measure at longer wavelengths of the visible spectral range like the Ozone Monitoring Instrument (OMI. We investigated details of the water vapour retrieval in the blue spectral range based on radiative transfer simulations and observations from the Global Ozone Monitoring Experiment 2 (GOME-2 and OMI. It is demonstrated that it is possible to retrieve the atmospheric water vapour column density in the blue spectral range over most parts of the globe. The findings of our study are of importance also for future satellite missions (e.g. Sentinel 4 and 5.

T. Wagner

2013-10-01

84

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)

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.

Gila Notesco

2013-11-01

85

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

DEFF Research Database (Denmark)

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.

Andersen, Martin; Tidemand-Lichtenberg, Peter

86

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 suggests that the citation pattern of DGPs members with no citations of their papers published in 2000 or 2005 respectively in the time intervals 2000-2004 or 2005-2009 generally differs from that of their colleagues across four ranges of specialization categories. Configural Frequency Analysis led to the identification of distinct subgroups of scientific specialization and international visibility, i.e., citations by others. Specifically, for those individuals who enjoy international visibility, one key to success seems to be multiple professional specializations with reference to different subdisciplines of psychology.

Clemens B. Fell

2012-06-01

87

Spectral Behavior of Hematite at Visible/Near Infrared and Midinfrared Wavelengths  

Science.gov (United States)

The oxide mineral hematite alpha-Fe2O3) is present on Mars as evidenced by spectroscopy using visible/near infrared (VNIR) and midinfrared (MIR) wavelengths. The physical nature of this surficial hematite varies from fine-grained, crystalline red hematite (red-Hm) in certain martian bright regions, to coarser-grained, crystalline gray hematite (gray-Hm) in the Sinus Meridiani equatorial site discovered in the Mars Global Surveyor Thermal Emission Spectrometer (MGS-TES) data. The VNIR spectra require that the red hematite is present in amounts subordinate to a second ferric pigment, which accounts for the general shape and position of the martian ferric absorption edge. By analogy with palagonitic tephra and synthetic samples, the pigment is a nanophase ferric oxide, possibly nanophase hematite (np-Hm). The purpose of this abstract is to document the physicospectral properties of hematite in the VNIR (0.35 to 2.2 mm) and MIR (5 to 25 mm) with respect to the terms "nanophase" and "crystalline", "red" and "gray", and "fine-grained" and "coarse-grained". We will show that different "types" of hematite (np-, red-, and gray-Hm) have different spectral responses in the VNIR and MIR regions and that these differences are important for inferring the types of hematite and their relative proportions from remotely sensed spectra of Mars. Because hematite is an alteration product that forms through many different geologic processes, determination of the type of hematite provides important clues about the style and diversity of martian weathering processes. Additional information is contained in the original extended abstract.

Lane, M. D.; Morris, R. V.; Christensen, P. R.

1999-01-01

88

Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator  

International Nuclear Information System (INIS)

We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical parametric oscillator (OPO) using a periodically-poled lithium niobate (PPLN) as the nonlinear material in combination with a lithium triborate (LBO) as the doubling crystal. A Kerr-lens-mode-locked (KLM) Ti:sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624–672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech2 pulse profile. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

89

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)

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.

Tsvetelina Draganova

2010-08-01

90

Carrier transfer and recombination dynamics of a long-lived and visible range emission from multi-stacked GaN/AlGaN quantum dots  

International Nuclear Information System (INIS)

We have investigated the optical properties of multi-stacked GaN/AlGaN self-assembled quantum dots (QDs) grown by molecular beam epitaxy. The QDs that emit visible light have a broad spectral range without incorporation of indium alloy because of the quantum-confined Stark effect. We found differences in the structural and optical properties between the layers of multi-stacked QDs. The carriers are more effectively transferred from the AlGaN barrier to the low energy side of the GaN QD emission than to the high energy side. We also observed long-lived carrier recombination dynamics for the visible range emission from QDs.

91

The influence of thermal treatment of the porous glass plates on the character of their scattering in visible spectral region  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The pore structure and light transmission of the high-silica porous glasses in visible spectral region are investigated depending on a temperature of their thermal treatment and composition of the initial two-phase alkali borosilicate glasses. The character of light transmission in porous glasses is analyzed considering the features of their pore space structure and processes occurring in porous glass upon heating. It is shown that with an increase in temperature of thermal treatment of the p...

Antropova, Tatyana V.; Anfimova, Irina N.

2010-01-01

92

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

Science.gov (United States)

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.

Abidi, B.

2014-05-01

93

Origin of the optical absorption of In2O3 thin films in the visible range  

International Nuclear Information System (INIS)

Optical absorption of thin films of In2O3 obtained by spray pyrolysis was studied in the visible part of the spectrum, using a numerical procedure for extraction of different contributions in the absorption coefficient. One contribution from a direct forbidden (3.29 eV) and three indirect allowed transitions (2.09 eV, 3.42 eV and 3.58 eV) were identified. They were attributed to the transitions from the valence band to the two lowest minima in the conduction band separated from the valence band by gaps ?2 eV and 3.3 eV large, in agreement with the results of ab intiio calculations done in Erhart et al (2007 Phys. Rev. B 75 153205). The fundamental absorption edge that has been observed at ?4 eV in many earlier experimental works is attributed to the transitions ?8??1, where ?1 is the lowest minimum in the conduction band at ? point and ?8 is a maximum substantially lower than the highest maximum in the valence band (?4) (Walsh et al 2008 Phys. Rev. Lett. 100 167402). Therefore, the high conductivity of In2O3 is due to the generation of carriers by transitions from the valence band in the two lowest maxima of the conduction band, going along with a high transmission in the visible range, up to the photon energies of ?4 eV, at which direct allowed transitions occur, leading to strong absorption

94

Ultra low-loss hypocycloid-core Kagome hollow-core photonic crystal fiber for green spectral-range applications.  

Science.gov (United States)

We report on the development of a hypocycloidal-core Kagome hollow-core photonic crystal fiber guiding, with low transmission loss in the 450-650 nm visible spectral range. Transmission loss records have been achieved with 70??dB/km at 600 nm, and 130??dB/km at 532 nm. As a demonstration of the fiber potential applications, we report on a compact 600 THz wide Raman comb generator, centered around 532 nm, and on a 10 W average power frequency-doubled Yb-fiber picosecond laser beam delivery, along with its use for organic material laser micro-processing. PMID:25361325

Debord, B; Alharbi, M; Benoît, A; Ghosh, D; Dontabactouny, M; Vincetti, L; Blondy, J-M; Gérôme, F; Benabid, F

2014-11-01

95

Photocatalysis in the visible range of sub-stoichiometric anatase films prepared by MOCVD  

International Nuclear Information System (INIS)

Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2 eV) it is not viable to use sunlight as an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380 nm is required. This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO2 thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters

96

Photocatalysis in the visible range of sub-stoichiometric anatase films prepared by MOCVD  

Energy Technology Data Exchange (ETDEWEB)

Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2 eV) it is not viable to use sunlight as an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380 nm is required. This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO{sub 2} thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters.

Justicia, I. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Garcia, G. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain)]. E-mail: gemma@icmab.es; Battiston, G.A. [ICIS/CNR, Corso Stati Uniti 4, 35127 Padova (Italy); Gerbasi, R. [ICIS/CNR, Corso Stati Uniti 4, 35127 Padova (Italy); Ager, F. [CNA/CSIC Parque Tecnologico Cartuja 93, Avda Thomas A, Edison, 41092 Sevilla (Spain); Guerra, M. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Caixach, J. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Pardo, J.A. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Rivera, J. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Figueras, A. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Instituto de Fisica, UNAM, Campus UNAM Juriquilla, 76230 Queretaro (Mexico)

2005-08-25

97

Chemical and environmental implications of visible and near-infrared spectral features of salt crusts formed from different brines.  

Science.gov (United States)

This work describes a laboratory experiment intended to study the formation and spectral reflectance properties of stratified salt crusts that cause severe environmental degradations to soil and water resources in arid regions. Salt crusts were prepared by evaporating three types of saline solutions consisting of i) NaCl - Na2SO4, ii) Na2SO4 - MgSO4, and iii) NaCl - MgSO4 at an initial concentrations of 50 mmol L(-1). They were examined for evaporite mineralogy using X-ray diffraction, optical and reflected microscopes, and for spectral reflectance with a high-resolution spectroradiometer (GER 3700) in the visible and near-infrared regions (400-2500 nm). The study documented chemical and environmental implications of the spectral properties of salt formed from the studied saline-systems. The reported results can be used to understand remotely sensed signatures of salt crusts and their implications. PMID:15242096

Howari, Fares M

2004-04-01

98

Visibilidad de Alcance Limitado en Polígonos Escalera / Visibility of limited range in staircase polygons  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish La definición de visibilidad en el Problema de Galerías de Arte utiliza guardias o luces que pueden ver o iluminar sin limitación en el alcance. En este artículo consideramos luces que tienen un alcance limitado L . Presentamos algunos resultados sobre polígonos escalera con luces situadas en sus vé [...] rtices. En el resultado principal se demuestra que si P es un polígono escalera con n vértices, [n/4]+O(l) luces vértice de alcance L son siempre suficiente y a veces necesarias para iluminar P con L[r/2,r), donde r es el radio de P . Abstract in english The usual definition of visibility in Art Gallery Problems uses guards or light sources that can watch or illuminate with unlimited range. In this paper we consider light sources having a limited range L . We present some results about staircase polygons with light sources placed in its vertices. Th [...] e main result that we prove is that if P is a staircase polygon of n vertices, then [n/4]+O(l) vertex light sources with range L are always sufficient and sometimes necessary to illuminate P when L [r/,2r), where r is the radius of P .

Santiago, Canales Cano; Gregorio, Hernández Peñalver.

2009-06-01

99

Fabrication of photonic crystals for applications in the visible range by Nanoimprint Lithography  

Science.gov (United States)

The integration of photonic crystals into optical circuits is a decisive factor for further development of photonic crystal applications. The feasibility of these applications depends on fabrication technologies suitable for mass production. In this work, we used Nanoimprint Lithography (NIL) for the fabrication of photonic crystal structures for applications in the visible range. The photonic crystals were integrated into waveguides in order to characterize the created system. The waveguides have dimensions of up to 50 ?m whereas the holes in the photonic crystals have dimensions of 80 nm. Due to parameter optimization photonic crystal structures and the corresponding waveguides could be replicated with high accuracy. For the fabrication of the photonic crystal structures a Si substrate with an oxide and a nitride layer was used. A poly-methyl-methacrylate (PMMA) layer was spincoated onto this substrate. A stamp containing the negative structures was fabricated using Electron Beam Lithography (EBL). This stamp was used for imprinting the structures into the PMMA layer. The structures were than transferred into the nitride layer using reactive ion etching (RIE). The underlying oxide layer was used as a sacrificial layer to achieve a nitride membrane. The fabricated structures were characterized by measuring the transmission spectra. The results were compared favorably to a simulation and a photonic band gap (PBG) in the range of 670 nm to 780 nm has been observed.

Senn, T.; Bischoff, J.; Nüsse, N.; Schoengen, M.; Löchel, B.

2011-07-01

100

Practical Atmospheric Correction Algorithms for a Multi-Spectral Sensor From the Visible Through the Thermal Spectral Regions  

Energy Technology Data Exchange (ETDEWEB)

Deriving information about the Earth's surface requires atmospheric corrections of the measured top-of-the-atmosphere radiances. One possible path is to use atmospheric radiative transfer codes to predict how the radiance leaving the ground is affected by the scattering and attenuation. In practice the atmosphere is usually not well known and thus it is necessary to use more practical methods. The authors will describe how to find dark surfaces, estimate the atmospheric optical depth, estimate path radiance and identify thick clouds using thresholds on reflectance and NDVI and columnar water vapor. The authors describe a simple method to correct a visible channel contaminated by a thin cirrus clouds.

Borel, C.C.; Villeneuve, P.V.; Clodium, W.B.; Szymenski, J.J.; Davis, A.B.

1999-04-04

 
 
 
 
101

Detection of wavelengths in the visible range using fiber optic sensors  

Science.gov (United States)

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.

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

2013-11-01

102

Spectral evolution of SN 1987A in the IUE long wavelength range  

International Nuclear Information System (INIS)

IUE low resolution spectra of SN 1987 A, in the long wavelength range, (1952 - 3348A), obtained in the period Feb 25, 1987 - Mar 17, 1988, have been analyzed to study its spectral evolution. We study the spectral variations by comparing spectra obtained at two consecutive observing dates

103

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

Science.gov (United States)

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.

Dantas, M. L.; Sodré, L., Jr.

2014-10-01

104

External quantum efficiency of Pt/n-GaN Schottky diodes in the spectral range 5-500nm  

International Nuclear Information System (INIS)

The external quantum efficiency in the spectral wavelength range 5-500nm of a large active area Pt/n-type GaN Schottky photodiode that exhibits low reverse bias leakage current, is reported. The Schottky photodiodes were fabricated from n-/n+ epitaxial layers grown by low pressure metalorganic vapour phase epitaxy on single crystal c-plane sapphire. The current-voltage (I-V) characteristics of several 0.25cm2 devices are presented together with the capacitance-voltage (C-V) characteristics of one of these devices. A leakage current as low as 14 pA at 0.5V reverse bias is reported, for a 0.25cm2 diode. The ultraviolet quantum efficiency measurements show that the diodes can be used as radiation hard detectors for the 5-365nm spectral range without the use of visible blocking filters. A peak responsivity of 77.5mA/W at 320nm is reported for one of the fabricated devices, corresponding to a spectral detectivity, D*=1.5x1014cmHz1/2W-1. The average detectivity between 250 and 350nm, for the same device, is reported to be D-bar*=1.3x1014cmHz1/2W-1. The spatial responsivity uniformity variation was established, using H2 Lyman-? radiation, to be +/-3% across the surface of a typical 0.25cm2 diode

105

Comparison of Plasma Visible Spectral Emissions Between Nova-UNICAMP and TCABR Tokamaks  

Science.gov (United States)

A comparison between the visible spectrum emissions observed on the Nova-UNICAMP and TCABR tokamak plasmas has been made in this work using a hand top HR4000 Ocean Optics spectrometer equipped with a CCD detector. A number of 58 emission lines, in which 22 are common to both machines, have been observed and identified. The differences in the observed spectrum can be explained by the difference in the time integration used in these measurements and by the materials compositions of the limiter and electrode in the TCABR tokamak. Nearby peak emissions have been separated using multi-peak Gaussian fit curves obtaining separation between peak centres with the same order of the spectrometer resolution. The HR4000 spectrometer can be routinely used to monitor the impurity species in the visible spectrum from the different tokamak windows.

do Nascimento, F.; Machida, M.; Ronchi, G.; Schmutzler, L. M. F.; Severo, J. H. F.; Nascimento, I. C.; Sanada, E. K.

2014-05-01

106

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.

107

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

Energy Technology Data Exchange (ETDEWEB)

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.

Chernikov, Alexey A.

2011-07-01

108

Demonstration of a spatial-spectral holographic LIDAR range-Doppler processor  

International Nuclear Information System (INIS)

We present a new approach to laser interferometric Doppler and ranging (LIDAR) processing using spatial-spectral holography (SSH). In this approach, broadband optical signals from a random noise or frequency-modulated laser are transmitted and reflected off remote targets. The return signals interfere spatially and spectrally with a local copy of the original transmit signal in an SSH medium, resulting in spectral gratings that have a spectral period inversely proportional to the LIDAR target's range and a position proportional to the target's Doppler (or velocity). These gratings are subsequently read out by a slowly chirped source onto a parallel detector array, and the velocity and range of the targets are inferred. We present the theoretical framework that describes the function of the LIDAR processor, as well as proof-of-concept experimental results

109

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Lovis, C.; Pepe, F.

2007-01-01

110

FTIR AND UV-VISIBLE SPECTRAL STUDY ON NORMAL BLOOD SAMPLES  

Directory of Open Access Journals (Sweden)

Full Text Available Spectroscopic techniques can be effectively employed as a diagnostic tool in clinical chemistry and it can be an alternate method in clinical analysis. The study of blood by spectroscopic techniques can be used not only for understanding the biological nature of the disease, but also for the diagnosis of the disease. In the present work, FTIR and UV-Vis spectroscopic technique is employed to study the spectral differences in the serum of normal blood samples.

Kanagathara N1*

2011-04-01

111

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

Science.gov (United States)

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.

Pan, Zhuokun; Huang, Jingfeng; Wang, Fumin

2013-12-01

112

UV and visible reflection spectral study of CO adsorption on the surface of yttrium, erbium, and holmium oxides  

International Nuclear Information System (INIS)

Diffuse reflection spectroscopy in the UV and visible ranges was used to study the surface compounds formed upon the adsorption of CO on Y2O3, Er2O3, and Ho2-O3. The adsorption of CO at 300 K on a surface aged at 1073 K is accompanied by the appearance of bands at 340, 350, and 450 nm, which are related to dioxoketenes (C2O3)2-, croconates (CO)52-, and rhodizonates (CO)62-

113

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

CERN Document Server

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.

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

2011-01-01

114

Use of high spectral resolution airborne visible/infrared imaging spectrometer data for geologic mapping: An overview  

Science.gov (United States)

Specific examples of the use of AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) high spectral resolution data for mapping, alteration related to ore deposition and to hydrocarbon seepage, and alluvial fans are presented. Correction for atmospheric effects was performed using flat field correction, log residuals, and radiative transfer modeling. Minerals of interest (alunite, kaolinite, gypsum, carbonate iron oxides, etc.) were mapped based upon the wavelength position, depth and width of characteristic absorption features. Results were checked by comparing to existing maps, results from other sensors (Thematic Mapper (TM) and TIMS (Thermal Infrared Multispectral Scanner)), and laboratory spectra of samples collected in the field. Alteration minerals were identified and mapped. The signal to noise ratio of acquired AVIRIS data, long to 2.0 microns, was insufficient to map minerals of interest.

Carrere, Veronique

1991-01-01

115

Measurement of transition probabilities in Kr II UV and visible spectral lines  

International Nuclear Information System (INIS)

This work reports an extensive collection of 120 atomic transition probabilities of Kr II lines in the spectral region 350-720 nm, all of them measured in an emission experiment. For many of them, these are the first data up to the authors' knowledge. Relative intensity measurements have been obtained on a pulsed discharge lamp and the absolute Aki-values have been calculated by considering the available data from the literature as reference for the plasma temperature diagnosis. Excitation temperature (14 000-28 000 K) has been determined by using the Boltzmann-plot method. The plasma electron density (0.2-0.8 x 1023 m-3) has been determined by two-wavelength interferometry. This work extends a previous one already published by our laboratory [1, 2]. Comparisons have also been made with previous literature values

116

Quantum efficiency of silicon photodiodes in the near-infrared spectral range.  

Science.gov (United States)

The quantum efficiency of silicon photodiodes and factors that might be responsible for the drop in quantum efficiency in the near-infrared spectral range were analyzed. It was shown that poor reflectivity from the rear surface of the die could account for a decrease in Si photodiode quantum efficiency in near-infrared spectral range by more than 20%. The photodiode quantum efficiency was modeled with an appropriate representation for the carrier-collection efficiency dependence on the die penetration depth. A corrected analytical expression for calculating the photodiode quantum efficiency is given. Some methods to improve the quantum efficiency of silicon photodiodes in near-infrared spectral range are discussed. PMID:12916603

Hicks, Chris; Kalatsky, Mark; Metzler, Richard A; Goushcha, Alexander O

2003-08-01

117

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

Science.gov (United States)

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.

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

118

Spectral radiance in the s20-range and luminance of the clear and overcast night sky.  

Science.gov (United States)

The spectral radiance of the night sky was investigated in the wavelength range from 0.40 microm to 0.80 microm.A series of measurements was taken in the Austrian Alps in 1968. Statistical reductions were made for the total data assembly as well as for data groups with different types of night sky cover, for moonless nights, and for nights with moon. The mean spectral radiance and the standard deviation in the above mentioned wavelength range are presented and discussed together with the distribution functions of the spectral radiance at 0.40 microm, 0.45 microm, 0.5577 (OI) microm, and 0.80 (OH) microm, of the photopic and scotopic luminances and of the S20 radiance. Finally the correlation coefficients regarding each pair of photopic, scotopic, and S20 responses were calculated together with the corresponding regression coefficients. The correlation coefficients are almost equal to unity. PMID:20125228

Höhn, D H; Büchtemann, W

1973-01-01

119

Sb-free quantum cascade lasers in the 3–4 ?m spectral range  

International Nuclear Information System (INIS)

In this work, the design and implementation of Sb-free short wavelength strain-compensated quantum cascade lasers in the 3–4 ?m spectral range is presented. Due to the presence of highly strained AlAs-barrier layers, the optimization of the epitaxial growth process is firstly discussed. The used active region design is then presented together with the observed laser performance. Watt-level room temperature emission at 3.3 ?m is shown for Fabry–Perot devices and laser operation in pulsed mode is observed above 350 K. The laser performance is comparable with Sb-containing quantum cascade lasers. Spectral tuning of the lasers in an external cavity configuration over more than 275 cm?1 is achieved with an emission wavelength as short as 3.15 ?m. For the first time in this spectral range, results on single-mode buried heterostructure distributed feedback lasers are shown. (paper)

120

Optical properties of human sclera in spectral range 370-2500 nm  

Science.gov (United States)

Optical characteristics of human sclera are experimentally studied. Experiments are performed in vitro on a Cary-2415 spectrophotometer in the spectral range 370-2500 nm. Based on the measured diffuse reflection and total transmission spectra, the absorption and transport scattering coefficient spectra are calculated by the inverse adding-doubling method.

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

2010-08-01

 
 
 
 
121

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

Science.gov (United States)

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.

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

2014-08-01

122

High-q microring resonator with narrow free spectral range for pulse repetition rate multiplication  

DEFF Research Database (Denmark)

We demonstrate a silicon-on-insulator microring resonator with a free-spectral-range of 0.32 nm, an extinction ratio of 27 dB, and a quality factor of ~140900 at 1550 nm that is used for pulse repetition-rate multiplication from 10 to 40 GHz.

Pu, Minhao; Ji, Hua

2009-01-01

123

Optical constants of ethylene glycol over an extremely wide spectral range  

Science.gov (United States)

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.

Sani, Elisa; Dell'Oro, Aldo

2014-11-01

124

Minor planet spectrometry. 4 Vesta: spectral range 0.48-0.55?m  

International Nuclear Information System (INIS)

Two absorption bands at 0.51 and 0.54 ?m are found in the spectrum of 4 Vesta, obtained with the 20.48 A spectral resolution. These bands are due to spin-forbidden transitions of the d-electrons in Fe2+ ions in pyroxene. Analogous bands are present only in the basaltic achondritic spectra. A conclusion is drawn that detailed spectrophotometry of the S-, R-, U-asteroids in the spectral range 0.48-0.6 ?m can give information on the presence of the differentiated matter of the certain kind on their surface

125

Application of microspectrometry in the visible range to differentiation of car paints for forensic purposes  

Science.gov (United States)

The first step to be taken in forensic investigation of paint samples is their comparative analysis in terms of colour. Microspectrometers allow an objective measurement of colour as opposed to the subjective results of visual colour comparison. In this paper, results of assessment of the usefulness of spectral information obtained by Vis microspectrometry in differentiation of small paint coat fragments for criminalistic purposes are presented. Fragments of red, blue, brown and green car paints were measured in reflectance mode both directly on a cross-section of the paint chip and via the top layer using a light beam falling perpendicular to the top surface of the sample, and in transmittance mode. It was found that the results obtained were reproducible. The variation in colour of paint samples measured via the top layer was greater. The reflectance curve obtained constitutes a representation of colour.

Trzci?ska, B.; Zi?ba-Palus, J.; Ko?cielniak, P.

2009-04-01

126

Spectral evolution of a photochemical protecting group for orthogonal two-color uncaging with visible light.  

Science.gov (United States)

Caged compounds are molecules rendered functionally inert by derivatization with a photochemical protecting group. We describe the design logic behind the development of a diethylaminocoumarin (DEAC) caging chromophore, DEAC450, that absorbs blue light strongly (?450 = 43,000 M(-1) cm(-1)) and violet light 11-fold more weakly. The absorption minimum is in the wavelength range (340-360 nm) that is traditionally used for photolysis of many widely used nitroaromatic caged compounds (e.g., 4-carboxymethoxy-5,7-dinitroindolinyl(CDNI)-GABA). We used this chromophore to synthesize DEAC450-caged cAMP and found this probe was very stable toward aqueous hydrolysis in the electronic ground state but was photolyzed with a quantum efficiency of 0.78. When DEAC450-cAMP and CDNI-GABA where co-applied to striatal cholinergic interneurons, the caged compounds were photolyzed in an chromatically orthogonal manner using blue and violet light so as to modulate the neuronal firing rate in a bidirectional way. PMID:24117060

Olson, Jeremy P; Banghart, Matthew R; Sabatini, Bernardo L; Ellis-Davies, Graham C R

2013-10-23

127

Eta Carinae across the 2003.5 Minimum: Analysis in the Visible and Near Infrared Spectral Region  

Science.gov (United States)

We present an analysis of the visible through near infrared spectrum of Eta Car and its ejecta obtained during the "Eta Car Campaign with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT)". This is a part of the larger effort to present a complete Eta Car spectrum, and extends the previously presented analyses with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) in the UV (1240-3159 Angstrom) to 10,430 Angstrom. The spectrum in the mid and near UV is characterized by the ejecta absorption. At longer wavelengths, stellar wind features from the central source and narrow emission lines from the Weigelt condensations dominate the spectrum. However, narrow absorption lines from the circumstellar shells are present. This paper provides a description of the spectrum between 3060 and 10,430 Angstroms, including line identifications of the ejecta absorption spectrum, the emission spectrum from the Weigelt condensations and the P-Cygni stellar wind features. The high spectral resolving power of VLT/UVES enables equivalent width measurements of atomic and molecular absorption lines for elements with no transitions at the shorter wavelengths. However, the ground based seeing and contributions of nebular scattered radiation prevent direct comparison of measured equivalent widths in the VLT/UVES and HST/STIS spectra. Fortunately, HST/STIS and VLT/UVES have a small overlap in wavelength coverage which allows us to compare and adjust for the difference in scattered radiation entering the instruments' apertures. This paper provides a complete online VLT/UVES spectrum with line identifications and a spectral comparison between HST/STIS and VLT/UVES between 3060 and 3160 Angstroms.

Nielsen, K. E.; Kober, G. Vieira; Weis, K.; Gull, T. R.; Stahl, O.; Bomans, D. J.

2009-01-01

128

Wide spectral-range imaging spectroscopy of photonic crystal microbeads for multiplex biomolecular assay applications  

Science.gov (United States)

Suspension assay using optically color-encoded microbeads is a novel way to increase the reaction speed and multiplex of biomolecular detection and analysis. To boost the detection speed, a hyperspectral imaging (HSI) system is of great interest for quickly decoding the color codes of the microcarriers. Imaging Fourier transform spectrometer (IFTS) is a potential candidate for this task due to its advantages in HSI measurement. However, conventional IFTS is only popular in IR spectral bands because it is easier to track its scanning mirror position in longer wavelengths so that the fundamental Nyquist criterion can be satisfied when sampling the interferograms; the sampling mechanism for shorter wavelengths IFTS used to be very sophisticated, high-cost and bulky. In order to overcome this handicap and take better usage of its advantages for HSI applications, a new wide spectral range IFTS platform is proposed based on an optical beam-folding position-tracking technique. This simple technique has successfully extended the spectral range of an IFTS to cover 350-1000nm. Test results prove that the system has achieved good spectral and spatial resolving performances with instrumentation flexibilities. Accurate and fast measurement results on novel colloidal photonic crystal microbeads also demonstrate its practical potential for high-throughput and multiplex suspension molecular assays.

Li, Jianping

2014-05-01

129

Collision-induced emission of singlet oxygen in the visible spectral region at temperatures of 90-315 K  

Science.gov (United States)

Collision-induced emission of singlet oxygen molecules is studied using spectrometers calibrated for absolute spectral sensitivity. The collision-induced emission-rate constants at wavelengths of 479, 514, 577, 634, and 703 nm are determined within the temperature range 90-315 K. It is found that the intensities of the emission bands increase with decreasing temperature below 100 K. The interrelation between the collision-induced emission-rate constants and the intensities of the collision-induced absorption bands is discussed. The Einstein coefficients for spontaneous emission of excited free O2: O2 complexes are estimated.

Zagidullin, M. V.; Svistun, M. I.; Khvatov, N. A.; Insapov, A. S.

2014-04-01

130

Dispersion properties and low infrared optical losses in epitaxial AlN on sapphire substrate in the visible and infrared range  

Energy Technology Data Exchange (ETDEWEB)

Optical waveguiding properties of a thick wurtzite aluminum nitride highly [002]-textured hetero-epitaxial film on (001) basal plane of sapphire substrate are studied. The physical properties of the film are determined by X-ray diffraction, atomic force microscopy, microRaman, and photocurrent spectroscopy. The refractive index and the thermo-optic coefficients are determined by m-lines spectroscopy using the classical prism coupling technique. The optical losses of this planar waveguide are also measured in the spectral range of 450–1553?nm. The lower value of optical losses is equal to 0.7 dB/cm at 1553?nm. The optical losses due to the surface scattering are simulated showing that the contribution is the most significant at near infrared wavelength range, whereas the optical losses are due to volume scattering and material absorption in the visible range. The good physical properties and the low optical losses obtained from this planar waveguide are encouraging to achieve a wide bandgap optical guiding platform from these aluminum nitride thin films.

Soltani, A., E-mail: ali.soltani@iemn.univ-lille1.fr; Stolz, A.; Gerbedoen, J.-C.; Rousseau, M.; Bourzgui, N.; De Jaeger, J.-C. [Institut d' Électronique, Microélectronique et Nanotechnologie, UMR-CNRS 8520, PRES Université Lille Nord de France, Cité Scientifique, Avenue Poincaré, CS 60069, 59652 Villeneuve d' Ascq Cedex (France); Charrier, J. [Fonctions Optiques pour les Technologies de l' informatiON, UMR-CNRS 6082, ENSSAT 6, rue de Kerampont, CS 80518, 22305 Lannion Cedex (France); Mattalah, M. [Laboratoire de Microélectronique, Université Djilali Liabes, 22000 Sidi Bel Abbes (Algeria); Barkad, H. A. [Institut Universitaire Technologique Industriel, Université de Djibouti, Avenue Georges Clémenceau, BP 1904 Djibouti (Djibouti); Mortet, V. [Institute of Physics of Academy of Sciences of Czech Republic, Fyzikální ústav AV CR, v.v.i., Na Slovance 1999/2 (Czech Republic); BenMoussa, A. [Solar Terrestrial Center of Excellence, Royal Observatory of Belgium, Circular 3, B-1180 Brussels (Belgium)

2014-04-28

131

Spectral reflectance measurements using a precision multiple reflectometer in the UV and VUV range.  

Science.gov (United States)

An imaging folded cavity is used to make an instrument for measuring absolute reflectivity in the UV and VUV spectral range (110-300 nm) with an accuracy of <5 x 10(-3) and a precision of <5 x 10(-4). This method operates over an incident angle between 5 and 70 degrees and can be used to measure transmissivity as well. PMID:20555994

Zhuang, D K; Yang, T L

1989-12-01

132

High-power tunable laser for the 9--12.5-?m spectral range  

International Nuclear Information System (INIS)

We have demonstrated continuous tunability of a high-pressure molecular gas laser over portions of the 9--12.5-?m spectral range. The laser employs electron-beam-controlled multiatmosphere discharges in He : N2 : CO2, He : CO : N2O, or He : CO : CS2. The high-pressure CS2 laser is continuously tunable in the 12.1-?m region which is relevant for laser separation of uranium isotopes

133

Visible to vacuum-UV range optical absorption of oxygen dangling bonds in amorphous SiO2  

International Nuclear Information System (INIS)

Synthetic silica glass with an optical absorption spectrum dominated by oxygen dangling bonds (nonbridging oxygen hole centers, or NBOHCs) and having negligible (2 laser (7.9 eV) at T = 80 K. This allowed us to obtain the up-to-now controversial optical absorption spectrum of NBOHC in the ultraviolet and vacuum-ultraviolet (UV-VUV) region of the spectrum and to show that it is semicontinuous from 4 to 7.8 eV and cannot be represented by a pair of distinct Gaussian bands. Since NBOHC is one of the main UV-VUV range optical absorbers in silica, its spectral shape provides a tool to disentangle contributions of different color centers to optical losses in this spectral region.

134

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

DEFF Research Database (Denmark)

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.

Snakenborg, Detlef; Perozziello, Gerardo

2006-01-01

135

Dose dependence of visible range diffuse reflectivity for Si{sup +} and C{sup +} ion implanted polymers  

Energy Technology Data Exchange (ETDEWEB)

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{sup +}) and carbon (C{sup +}) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 5.10{sup 12}-2.10{sup 17} cm{sup +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 R{sub d} = f({lambda}) of the implanted samples have been measured in the visible range ({lambda} = 400 to 830 nm). In this paper the dose dependences of the size and sign of the diffuse reflectivity changes {delta}R{sub d} = f(D) have been analyzed.

Balabanov, S; Tsvetkova, T [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Borisova, E; Avramov, L [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Bischoff, L [Forschungszentrum Rossendorf e.V., PO Box 510119, D-01314 Dresden (Germany)], E-mail: sbalab@issp.bas.bg

2008-05-01

136

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

Directory of Open Access Journals (Sweden)

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.

Sreelakshmi Yellamaraju

2011-01-01

137

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

Science.gov (United States)

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

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

2014-08-01

138

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

139

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

Science.gov (United States)

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÷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 ÷ 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÷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.

Balabanov, S.; Tsvetkova, T.; Borisova, E.; Avramov, L.; Bischoff, L.

2008-05-01

140

Spectral distribution of UV range diffuse reflectivity for Si{sup +} ion implanted polymers  

Energy Technology Data Exchange (ETDEWEB)

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{sup +}) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 1.10{sup 13} to 1, 2.10{sup 17} cm{sup -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 R{sub d} = f({lambda}) of the ion implanted samples have been measured in the UV range ({lambda} = 220 to 350 nm). In this paper the dose dependences of the size and sign of the diffuse optical reflectivity changes {lambda}Rd = f(D) have been analysed.

Balabanov, S; Tsvetkova, T [Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Borisova, E; Avramov, L [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia (Bulgaria); Bischoff, L [Forschungszentrum Rossendorf e.V., PO Box 510119, D-01314 Dresden (Germany)], E-mail: sbalab@issp.bas.bg

2008-05-01

 
 
 
 
141

Full range complex spectral domain optical coherence tomography without additional phase shifters.  

Science.gov (United States)

We demonstrate a new full range complex spectral domain optical coherence tomography (FRC SD-OCT) method. Other than FRC SD-OCT systems reported in literature, which employed devices such as electro-/acousto optic modulators or piezo-driven mirrors providing the phase modulations necessary for retrieval of the complex-valued signal, the system presented works without any additional phase shifting device. The required phase shift is introduced by the galvanometer scanner used for transversally scanning the sample beam. By means of a slight displacement of the probe beam with respect to the scanning mirror's pivot axis, the sample arm length and thus the phase is continuously modulated as the beam is scanned in lateral direction. From such modulated spectral data, the complex-valued data yielding a twofold increase of accessible depth range can be calculated using an algorithm based on the Hilbert transform. To demonstrate the performance of our method quantitative measurements of the suppression of mirror images as a function of induced phase shift were performed. In order to validate the FRC SD-OCT technique for high-speed imaging of biological tissue, we present full-range images of the human anterior chamber in vivo. PMID:19550607

Baumann, Bernhard; Pircher, Michael; Götzinger, Erich; Hitzenberger, Christoph K

2007-10-01

142

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

CERN Document Server

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.

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

2012-01-01

143

Large area double p-i-n heterostructure for signal multiplexing and demultiplexing in the visible range  

Energy Technology Data Exchange (ETDEWEB)

Results on the use of a double a-SiC:H p-i-n heterostructure for signal multiplexing and demultiplexing applications in the visible range, are presented. Modulated monochromatic beams together (multiplexing mode), or a single polychromatic beam (demultiplexing mode) impinge in the device and are absorbed, accordingly to their wavelength, giving rise to a time and wavelength dependent electrical field modulation. Red, green and blue pulsed input channels are transmitted together, each one with a specific transmission rate. The combined optical signal is analyzed by reading out, under different applied voltages, the generated photocurrent. Results show that in the multiplexing mode the output signal is balanced by the wavelength and transmission rate of each input channel, keeping the memory of the incoming optical carriers. In the demultiplexing mode the photocurrent is controlled by the applied voltage allowing regaining the transmitted information. An electrical model gives insight into the device operation.

Vieira, M., E-mail: mv@isel.ipl.p [Electronics Telecommunications and Computer Dept, ISEL, 1959-007, Lisbon (Portugal); CTS-UNINOVA, Monte da Caparica, 2829-516 (Portugal); Louro, P. [Electronics Telecommunications and Computer Dept, ISEL, 1959-007, Lisbon (Portugal); CTS-UNINOVA, Monte da Caparica, 2829-516 (Portugal); Fernandes, M. [Electronics Telecommunications and Computer Dept, ISEL, 1959-007, Lisbon (Portugal); Vieira, M.A. [Electronics Telecommunications and Computer Dept, ISEL, 1959-007, Lisbon (Portugal); CML-Traffic Department, Lisbon (Portugal); Fantoni, A. [Electronics Telecommunications and Computer Dept, ISEL, 1959-007, Lisbon (Portugal); Barata, M. [Electronics Telecommunications and Computer Dept, ISEL, 1959-007, Lisbon (Portugal); CTS-UNINOVA, Monte da Caparica, 2829-516 (Portugal)

2009-10-01

144

Large area double p-i-n heterostructure for signal multiplexing and demultiplexing in the visible range  

International Nuclear Information System (INIS)

Results on the use of a double a-SiC:H p-i-n heterostructure for signal multiplexing and demultiplexing applications in the visible range, are presented. Modulated monochromatic beams together (multiplexing mode), or a single polychromatic beam (demultiplexing mode) impinge in the device and are absorbed, accordingly to their wavelength, giving rise to a time and wavelength dependent electrical field modulation. Red, green and blue pulsed input channels are transmitted together, each one with a specific transmission rate. The combined optical signal is analyzed by reading out, under different applied voltages, the generated photocurrent. Results show that in the multiplexing mode the output signal is balanced by the wavelength and transmission rate of each input channel, keeping the memory of the incoming optical carriers. In the demultiplexing mode the photocurrent is controlled by the applied voltage allowing regaining the transmitted information. An electrical model gives insight into the device operation.

145

BepiColombo SIMBIO-SYS data: Preliminary evaluation for rock discrimination and recognition in both low and high resolution spectroscopic data in the visible and near infrared spectral intervals  

Science.gov (United States)

A stereo camera (STC) with panchromatic and 4 visible-near infrared (NIR) filters and a visible-near infrared hyperspectral imager (VIHI) with 400-2000 nm spectral range, integrated into the spectrometers and imagers for BepiColombo integrated observatory-system (SIMBIO-SYS) selected for BepiColombo, are dedicated to the geologic exploration of Mercury's surface. In this study the responses of the two sensors were simulated and degraded by the addition of random noise, with the purpose of evaluating their suitability to resolve the spectroscopic features diagnostic of rock forming minerals and discriminate among different lithotypes. Two cumulates (norite and anorthosite) from a Late Proterozoic layered intrusion and two basaltic lavas from Mount Etna complex were selected as possible terrestrial analogues of Mercury. Interband spectral reflectance ratios of STC noise-free data provided a first order discrimination among the different rock types. VIHI noise-free data compare well with laboratory reflectance data for the identification of the spectral features of the most important rock forming minerals. STC noisy spectra simulated for S/ N=200 showed that, because of the low reflectance of the surface rocks, the band ratios of the different rocks can partly overlap, with some uncertainty in rock discrimination. VIHI noisy spectra simulated for S/ N=100 indicated that for well defined spectral features with band depth 0.1 reflectance unit, the shift in band position corresponds to a variation of less than 0.03 atoms/formula unit of the spectrally active phases. Weaker bands have a high probability of being misidentified.

Sgavetti, Maria; Pompilio, Loredana; Carli, Cristian; de Sanctis, Maria Cristina; Capaccioni, Fabrizio; Cremonese, Gabriele; Flamini, Enrico

2007-09-01

146

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

CERN Document Server

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.

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

2007-01-01

147

Calibrating image plate sensitivity in the 700 to 5000 eV spectral energy range  

Science.gov (United States)

This paper describes a method to calibrate image plate sensitivity for use in the low energy spectral range. Image plates, also known as photostimulable luminescence (PSL) detectors, have often proved to be a valuable tool as a detector for plasma physics studies. Their advantages of large dynamic range, high stopping power, and resistance to neutron damage sometimes outweigh the problems of limited resolution and the remote processing required. The neutron damage resistance is required when the X-ray source is producing a high neutron flux. The Static X-ray Imager (SXI) is a key diagnostic on the National Ignition Facility (NIF) target chamber at LLNL for use in determining the symmetry of the laser beams. The SXI is essential to proper interpretation of the data from the Dante diagnostic to determine the X-ray radiation temperature. It is comprised of two diagnostics located at the top and the bottom of the target chamber. The usual detector is a large array CCD camera. For shots giving high yields of neutrons, the camera would not only be blinded by the neutrons, it would be damaged. To get around this problem, an image plate (IP) is used as the detector. The NIF application covers the energy range from 700 to 5000 eV. The type of image plates typically used for plasma physics are the Fuji BAS-MS, BAS-SR, and BAS-TR models. All models consist of an X-ray sensitive material made of BaF(Br,I):Eu2+ embedded in a plastic binder. X-rays incident on the phosphor ionize the Eu 2+ producing Eu3+ and free electrons that are trapped in lattice defects (F-centers) produced by the absence of halogen ions in the BaF2 crystal. An image plate readout scanner irradiates the IP with a red laser causing reduction of the Eu3+ and emission of a blue photon. The photon is collected using a photomultiplier and digitized to make an electronic image. Image plates are cleared of all F-centers by putting them under a bright light for about 10 minutes. They are then ready for producing a new X-ray image. The MS IP model has the higher sensitivity and the SR IP and TR IP models are designed for higher resolution. The MS and SR IPs have a thin Mylar coating that protects the sensitive layer. The TR model has no protective layer and is more sensitive at the lower X-ray energies but must be handled more carefully. The raw image data from the Fuji scanner can be converted to units of PSL that are proportional to the photon count. The equation relating PSL to the raw greyscale value is: PSL = (R/100)2(4000/S)exp10{L(G/(2B-1)-1/2)} where R is the resolution in ?m S is the sensitivity setting L is the latitude B is the dynamic range (8 or 16 bits) G is the raw image greyscale value. The IP photon sensitivity is defined as the PSL output per photon input and is a function of the photon energy. Meadowcroft et al in 2008 published the sensitivity for the three types of image plates in the spectral range from 1 to 100 keV. Maddox et al measured the sensitivity for type MS and SR image plates from 8 to 80 keV using the NSTec High Energy X-ray (HEX) source, a fluorescer type X-ray source. The Meadowcroft and Maddox measurements used similar X-ray sources for the higher spectral and the same type of IP scanner, the FLA 7000. There is reasonable agreement between the Maddox and Meadowcroft sensitivity measurements of MS and SR type IP for the at spectral energies above 20 keV, but the Maddox sensitivities are much lower than those of Meadowcroft in the energy range below 20 keV. Recently Bonnet et al published a model for the photon sensitivity based upon the amount of energy deposited and Monte Carlo calculations to incorporate the specifics of the X-ray absorption and the readout process. The model was calibrated for sensitivity using radioactive sources. The model was compared to the previous publications cited. The Bonnet model tends to agree with the Meadocroft measurements at the low spectral energies. The present paper describes the measurement of IP sensitivity in the spectral range from 700 to 8000 eV. The sensitivity in this spectral range had not p

Haugh, Michael J.; Lee, Joshua; Romano, Edward; Schneider, Marilyn

2013-09-01

148

Growth and characterization of InAsN/GaAs dilute nitride semiconductor alloys for the midinfrared spectral range  

International Nuclear Information System (INIS)

We report the growth of InAsN onto GaAs substrates using nitrogen plasma source molecular beam epitaxy. We describe the spectral properties of InAsN alloys with N-content in the range of 0%-1% and photoluminescence emission in the midinfrared spectral range. The photoluminescence emission of the sample containing 1% N reveals localized energy levels resonant with the conduction band states of InAsN.

149

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2010-01-01

150

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

Science.gov (United States)

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.

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

2002-01-01

151

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

Science.gov (United States)

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.

Gneiding, N.; Zhuromskyy, O.; Shamonina, E.; Peschel, U.

2014-10-01

152

Complex refractive index of ammonium nitrate in the 2-20-?m spectral range  

Science.gov (United States)

Using high-resolution Fourier-transform infrared absorbance and transmittance spectral data for ammonium sulfate (AMS), calcium carbonate (CAC), and ammonium nitrate (AMN), we made comparisons with previously published complex refractive-index 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 ?m. Subtractive 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 index obtained for AMN. We performed backscatter calculations using a log-normal size distribution for AMS, AMN, and CAC aerosols to show differences in their backscattered spectra.

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

2003-02-01

153

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

CERN Document Server

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.

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

154

Estimating aerosol concentration and spectral backscatter with multi-wavelength range-resolved lidar  

Science.gov (United States)

Algorithm development for detecting and discriminating atmospheric aerosols using range-resolved lidar is a straightforward, if non-trivial, application of well-established techniques of statistical signal processing assuming the aerosol backscatter coefficients are known as a function of wavelength. Unfortunately, in contrast to the analogous case of vapors, in most aerosol applications those coefficients are rarely known accurately. This is due to a combination of factors: (1) unknown refractive index dependence on wavelength, particularly for bioaerosols; (2) unknown particle size distribution; and (3) lack of particle sphericity making M e calculations unreliable. Uncertainties in any of these factors can distort the backscatter cross-section spectral dependence to the extent that aerosol identification becomes impossible. This paper presents a sequential algorithm for estimating both the aerosol concentration dependence on range and time and backscatter coefficient spectral signatures for a set of materials using M wavelengths with data available prior to the aerosol release for estimating the ambient lidar return. The rangedependence of the aerosol is modeled as an expansion of the concentration in an orthonormal basis set whose coefficients carry the time dependence. The basic idea is to run two estimators in parallel: a Kalman filter for the expansion coefficients, and a maximum likelihood estimator for the set of aerosol backscatter coefficients. These algorithms exchange information continuously over the data processing stream. The approach is illustrated on atmospheric backscatter lidar data collected by the U.S. Army multi-wavelength lidar from aerosol releases at the recent JBSDS trials at Dugway Proving Ground, UT.

Warren, Russell E.; Vanderbeek, Richard G.

2005-11-01

155

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Gila Notesco; Eyal Ben-Dor; Simon Adar; Yoel Shkolnisky

2013-01-01

156

On the wavelength-dependent attenuation of radiation in the UV-visible range by a homogeneous cloud layer  

Science.gov (United States)

Understanding clouds and their influence on radiation is important for many applications within atmospheric research. For instance, climate modeling as well as modeling of UV radiation and atmospheric chemistry can make use of such information. In this work, which is an update of our recent paper in GRL, we broaden the current understanding of the wavelength-dependent effect of clouds on incoming solar radiation. We modeled the attenuation of incoming solar radiation in the UV-visible range by a homogeneous cloud layer using the libRadtran radiative transfer package. By separating the wavelength-dependence of the cloud modification factor into different components, we achieved an understanding of the physical processes involved. Our results show that short wavelengths, in general, penetrate the cloud more effectively than longer wavelengths, and that there are two important contributors to this wavelength-dependence: (i) that induced by multiple scattering between the cloud top and the atmosphere above, and (ii) that introduced by the wavelength-dependent radiance distribution at the cloud top (including the direct beam) together with the transmittance of the cloud alone as function of angle of incidence. Furthermore, we found that (i) does not depend on solar zenith angle, whereas (ii) does and hence also introduces a solar zenith angle dependence in the wavelength-dependence of the cloud modification factor.

Lindfors, Anders; Arola, Antti

2009-03-01

157

New developments in the radiance calibration of deuterium lamps in the UV and VUV spectral range at the PTB  

International Nuclear Information System (INIS)

The Physikalisch-Technische Bundesanstalt (PTB) operates a unique beam line for the radiometric calibration of ultraviolet (UV) and vacuum-ultraviolet (VUV) radiation sources by direct comparison of their unknown spectral radiant flux with the calculable spectral radiant flux of the electron storage ring BESSY I in the spectral range 40 nm to 400 nm. At this beam line the relative standard uncertainty of the calculated spectral radiant flux of the synchrotron radiation is u = 3 x 10-3 and it allows the calibration of the spectral radiance of deuterium lamps with a relative standard uncertainty of 2.5 x 10-2 above 165 nm. The high-accuracy beam line is now complemented by new instrumentation specially designed for the dissemination of the spectral radiance and radiant intensity scale using deuterium lamps as transfer source standards. This instrumentation allows the calibration of radiation sources in the 115 nm to 400 nm spectral range without significant loss in accuracy and the measurement of spectrally and spatially resolved radiance profiles such as to image the plasma topography of the discharge. The new instrumentation is described. Results for the radiometric long-term stability of selected deuterium lamps are shown. The radiance and radiant intensity as well as the radiance profile of different types of commercially available deuterium lamp are presented. (authors)

158

A panoply of insertion devices at SOLEIL for a wide spectral range and flexible polarisation  

International Nuclear Information System (INIS)

The SOLEIL storage ring presents a very high fraction of its circumference dedicated to accommodate Insertion Devices (ID). Over the 25 presently planned insertion devices presenting a large variety of systems, 16 have been already installed and commissioned in September 2009. The UV-VUV region is covered with electromagnetic devices, offering tuneable polarisations. An electromagnet/permanent magnet undulator using copper sheets coils for fast switching of the helicity is under construction. 13 APPLE-II type undulators, with period ranging from 80 down to 36 mm, provide photons in the 0.1-10 keV region, some of them featuring tapering or quasi-periodicity. Five U20 in vacuum undulators cover typically the 3-30 keV range whereas an in vacuum wiggler, with compensation of the magnetic forces via adequate springs will cover the 10-50 keV spectral domain. R and D on cryogenic in-vacuum undulator is also under progress. A magnetic chicane using permanent magnet dipoles has also been designed in order to accommodate two canted undulators on the same straight section. A wiggler dedicated to slicing (production of femto second long pulses) is also being designed, its radiation will also serve for an X-ray beamline.

159

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

Directory of Open Access Journals (Sweden)

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.

L. Vogel

2012-06-01

160

Spectral synthesis provides two-dimensional videos on a one-dimensional screen with 360°-visibility and mirror-immunity.  

Science.gov (United States)

Spatial light modulator (SLM)-based tunable sources synthesize any specified spectral power distribution. However, their complexity makes a simpler version desirable. A prism before an SLM-projector is shown to synthesize spectra at least as effectively. Moreover, this simple setup projects two-dimensional (2-D) videos onto a one-dimensional (1-D) screen. Viewed through a prism (or grating), rainbow-colored renderings of grayscale videos emerge. The semitransparent, 2-D virtual images face each viewer all around the 1-D screen. Uncannily, mirrors around the 1-D screen cannot flip the images. In hindsight, SLM-based spectral synthesis is essentially a form of spectral encoding that is applicable to video projection, and beyond. PMID:24514184

Grusche, Sascha

2014-02-01

 
 
 
 
161

Spectral-kinetic characteristics of Pr3+ luminescence in LiLuF4 host upon excitation in the UV-VUV range  

International Nuclear Information System (INIS)

Spectral-kinetic study of Pr3+ luminescence has been performed for LiLuF4:Pr(0.1 mol%) single crystal upon the excitation within 5-12 eV range at T=8 K. The fine-structure of Pr3+ 4f 2?4f 5d excitation spectra is shown for LiLuF4:Pr(0.1 mol%) to be affected by the efficient absorption transitions of Pr3+ ions into 4f 5d involving 4f 1 core in the ground state. Favourable conditions have been revealed in LiLuF4:Pr(0.1 mol%) for the transformation of UV-VUV excitation quanta into the visible range. Lightly doped LiLuF4:Pr crystals are considered as the promising luminescent materials possessing the efficient Pr3+3P0 visible emission upon UV-VUV excitation. The mechanism of energy transfer between Lu3+ host ion and Pr3+ impurity is discussed

162

GOES-R Advanced Baseline Imager: spectral response functions and radiometric biases with the NPP Visible Infrared Imaging Radiometer Suite evaluated for desert calibration sites.  

Science.gov (United States)

The Advanced Baseline Imager (ABI), which will be launched in late 2015 on the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite R-series satellite, will be evaluated in terms of its data quality postlaunch through comparisons with other satellite sensors such as the recently launched Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership satellite. The ABI has completed much of its prelaunch characterization and its developers have generated and released its channel spectral response functions (response versus wavelength). Using these responses and constraining a radiative transfer model with ground reflectance, aerosol, and water vapor measurements, we simulate observed top of atmosphere (TOA) reflectances for analogous visible and near infrared channels of the VIIRS and ABI sensors at the Sonoran Desert and White Sands National Monument sites and calculate the radiometric biases and their uncertainties. We also calculate sensor TOA reflectances using aircraft hyperspectral data from the Airborne Visible/Infrared Imaging Spectrometer to validate the uncertainties in several of the ABI and VIIRS channels and discuss the potential for validating the others. Once on-orbit, calibration scientists can use these biases to ensure ABI data quality and consistency to support the numerical weather prediction community and other data users. They can also use the results for ABI or VIIRS anomaly detection and resolution. PMID:24216671

Pearlman, Aaron; Pogorzala, David; Cao, Changyong

2013-11-01

163

Spectral analysis of topography and gravity in the Basin and Range Province  

Science.gov (United States)

A two-dimensional spectral analysis has been carried out for the topography and the Bouguer gravity anomaly of the Basin and Range Province in western North America. The aim was to investigate the possible presence of dominant wavelengths in the deformation pattern at the surface and at the depth of compensation. The results suggest that a 200-km wavelength in the deep compensating mass distribution has been inherited from an early tectonic phase of extension at an azimuth N65??E. The corresponding surface topography exhibits prominent overtones at wavelength of 100, 75, and possibly 45 km. It is argued that these characterize the non-linear rheology of the upper crust. The short wavelengths in the topography reflect the present phase of deformation, mixed with the results of the older deformations. These results point to a need to extend the physical models of lithospheric stretching beyond the presently available one-phase scenario. However, they show that the boudinage instability concept is consistent with the data. ?? 1987.

Ricard, Y.; Froidevaux, C.; Simpson, R.

1987-01-01

164

Transmitted spectral modulation of double-ring resonator using liquid crystals in terahertz range  

Science.gov (United States)

Metamaterials with subwavelength structural features show unique electromagnetic responses that are unattainable with natural materials. Recent research on these artificial materials has been pushed forward to the terahertz region because of potential applications in biological fingerprinting, security imaging, remote sensing, and high frequency magnetic and electric resonant devices. Active control of their properties could further facilitate and open up new applications in terms of modulation and switching. Liquid crystals, which have been the subject of research for more than a century, have the unique properties for the development of many other optical components such as light valves, tunable filters and tunable lenses. In this paper, we investigated the transmitted spectral modulation in terahertz range by using liquid crystals (5CB and TEB300) covering on the fabricated double-ring resonators to realize the shift of the resonance frequency. Our obtained results indicate the low frequency resonance shows the obvious blue-shift, while the location of high frequency resonance is nearly unchanged. We believe this phenomenon is related to not only the refractive index of the covering liquid crystals but also the resonant mechanism of both resonances.

Sun, Huijuan; Zhou, Qingli; Wang, Xiumin; Li, Chenyu; Wu, Ani; Zhang, Cunlin

2013-12-01

165

High-resolution spectra of Jupiter in the 744--980 inverse centimeter spectral range  

International Nuclear Information System (INIS)

Spectra of the central 5'' region of Jupiter in the 744--980 cm-1 (10.2--13.4?m) spectral range are presented at 0.05 and 0.28 cm-1 resolution. The gases 14NH3, 15NH3, and PH3 are observed in absorption, and C2H2 and C2H6 are observed in emission. A synthetic spectrum which included the opacity from H2, 14NH3, 15NH3, and PH3 is compared with the observations. We conclude that: (1) the 14NH3 line profiles are best fitted with a NH3 density in the troposphere which is 0.5 times the saturated vapor pressure density and an opaque cloud at the 0.56 bar pressure level (T=140 K); (2) the best-fit 15NH3/14NH3 ratio is 0.006 (but may be consistent with the terrestrial ratio within model uncertainties); (3) the [PH3]/[H2] ratio is 1--2 x 10-7 in the tropopause; (4) the mixing ratios of NH3 and PH3 must be highly subsaturated above the tropopause or the temperature inversion is cooler than the model predictions; and (5) the intensities of the /sup R/Q0 branch of the ?9 fundamental of C2H6 and lines of the R branch of the ?5 fundamental of C2H6 are consistent with previous work

166

Spectral parameters and visible fluorescence of Sm3+ in alkali-barium-bismuth-tellurite glass with high refractive index  

International Nuclear Information System (INIS)

Sm3+-doped alkali-barium-bismuth-tellurite (LKBBT) glass with high refractive index has been fabricated and characterized optically. The refractive index, density, optical absorption, IR transmittance, Judd-Ofelt parameters and spontaneous transition probabilities have been measured, calculated and analyzed. In the LKBBT glass, Sm3+ ions emit intense reddish-orange lights under the excitation of long-wave UV and blue lights. Absorption and excitation spectra indicate that commercial UV and blue laser diodes, blue and bluish-green LEDs and Ar+ optical laser are powerful excitation sources for Sm3+ visible fluorescence in the glass with high optical refractive index

167

Photoinduced catalytic adsorption of model contaminants on Bi/Cu pillared montmorillonite in the visible light range  

Science.gov (United States)

Montmorillonite K10 clay was pillared with BiCl3 and Cu(NO3)2 to extend its applicability as catalytic adsorbent to degrade aqueous solution of anionic azo-dye Methyl Orange (MO) in the presence of visible light irradiation. The preparation of Bi/Cu-montmorillonite utilized benig...

168

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

Science.gov (United States)

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.

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

2012-05-01

169

Efficient noncollinear parametric amplification of weak femtosecond pulses in the visible and near-infrared spectral range.  

Science.gov (United States)

We report measurement of efficient amplification of weak femtosecond supercontinuum seed pulses by use of a noncollinear optical parametric process in BBO crystal pumped with 150-fs pulses from a frequency-doubled regenerative-amplified Ti:sapphire laser at 390nm . The highest amplification factor, 10(8) , was achieved for 3x10(-16)J energy seed pulses at wavelength of 560nm. PMID:18084425

Krylov, V; Ollikainen, O; Gallus, J; Wild, U; Rebane, A; Kalintsev, A

1998-01-15

170

Broadly-tunable high-power fiber laser system for IR spectral range  

Science.gov (United States)

Broadly tunable fiber laser system has been demonstrated at room temperature. The IR fiber laser system consists of two high peak power individual pulse fiber lasers and their difference frequency generation (DFG) in Periodically Poled Lithium Niobate (PPLN) nonlinear optical crystal. Both lasers were operating at 20 kHz Pulse Repetition Rate and 200 ns pulse duration with diffraction limited beam quality. The first laser is a CW, cavity amplitude modulated Yb fiber laser ring oscillator - high power two stage amplifier which produced 280 mW of average and 70W of Peak power, respectively. The second laser is a DFB CW, single 1556 nm wavelength, cavity amplitude modulated Er fiber laser oscillator - high power single stage amplifier with 160 mW of output average power and 40W of peak power. Synchronized pulses from two fiber lasers have been combined and fiber coupled into a single polarization maintained fiber using a fiber WDM combiner and then fibercoupled into the NovaWave Technologies, commercial DFG laser module which employed 50 mm PPLN crystal. The DFG stage of the system produced tunable radiation in 3236.4-3545.4 nm spectral range (309 nm). The difference frequency generation has a 9 mW average power, 20 kHz pulse repetition rate and 200 ns pulse duration which corresponds to 2.25 W of peak power. The demonstrated pulse DFG conversion efficiency is 0.2 W/W2 (20%/W) which is ~ 100 times higher than that of CW operation. Further scaling of IR laser power was limited by optical damage of PPLN crystal and fiber lasers combining optics. Using a PPLN-MgO crystal and additional fiber laser amplifier stages based on Large Mode Area gain fibers is expected to allow us to achieve damage free difference frequency generation with up-to 100 mW of average power and peak power of up to 25 W.

Ter-Mikirtychev, Valerii V.; Paul, Joshua B.; Scherer, James J.

2007-02-01

171

Increasing of frequency range of noise spectral density of silicon p-n-structures under gamma irradiation  

CERN Document Server

One studied possibility of purpose-oriented shifting of high-frequency boundary of noise plateau-spectral density of silicon p-n-structures towards high frequency range under irradiation by gamma-quanta. One observed the maximum increase of frequency range working band up to 2-2.5 times. At further irradiation of the studied structures the plateau width was not increased and its boundary was eroded. One detected correlation between the variation of lifetime of charge secondary carriers and the width of low-frequency plateau of noise spectral density. One introduced a qualitative model to describe variation of noise spectral density with irradiation flow fro silicon p-n-structures governed by distances of p-n-transition

Baranovskij, O K; Kuchinskij, P V; Petrunin, A P; Savenok, E D

2001-01-01

172

Fabrication and evaluation of active spectral filter with metal-insulator-metal structure for visible light communication  

Science.gov (United States)

Plasmonic spectral filter based on a metal-insulator-metal (MIM) structure is one of the candidates of active devices with white LEDs in the ubiquitous network society. In order to make this filter electrically active, "silver alloy and quartz-coated silver films" and "PLZT films by the dry and wet processes" were fabricated and evaluated under high annealing temperatures. The quartz-coated silver film and the PLZT film by the dry process" could be possible as the metal and insulator layers, respectively. The issue of thickness determination of the insulator layer is also discussed.

Murai, Kensuke; Oshikane, Yasushi; Yamamoto, Fumihiko; Hattori, Kou; Mochizuki, Shoichi; Mihara, Toshiyuki; Nakano, Motohiro

2014-02-01

173

A comparison of LOWTRAN-7 corrected Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data with ground spectral measurements  

Science.gov (United States)

Atmospheric correction of imaging spectroscopy data is required for quantitative analysis. Different models were proposed for atmospheric correction of these data. LOWTRAN-7 is a low-resolution model and computer code for predicting atmospheric transmittance and background radiance from 0 to 50,00 cm(sup -1) which was developed by the Air Force Geophysics Laboratory. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data used are radiometrically calibrated and include the 28 Sep. 1989 Providence Fan flight line segment 07, California. It includes a dark gravel surface defined as a calibration site by the Geologic Remote Sensing Field Experiment (GRSFE). Several ground measurements of portable spectrometer DAEDALUS AA440 Spectrafax were taken during the GRSFE, July 1989 field campaign. Comparisons of the LOWTRAN-7 corrected AVIRIS data with the ground spectrometer measurement were made.

Xu, Peng-Yang; Greeley, Ronald

1992-01-01

174

Uncooled photodetectors for the 3-5 mu m spectral range based on III-V heterojunctions. .  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The design, fabrication, and characterization of heterojunction photodiodes for room temperature operation in the mid-infrared (3–5 µm) spectral range is described. Devices appropriate for carbon dioxide detection have been developed and studied. The authors report on the improvements obtained by increasing buffer layer thickness and also by using a blocking barrier to reduce leakage current

Krier, A.; Suleiman, W.

2006-01-01

175

Full range spectral domain optical coherence tomography using a fiber-optic probe as a self-phase shifter.  

Science.gov (United States)

We present a full range handheld probe type spectral domain optical coherence tomography (SD-OCT) method. Here, the sample arm is composed of a tilted fiber-optic cantilever scanner; thus, the phase shift concurrently occurs while sample scanning. With the phase shift, we could achieve a full range complex-conjugate-free OCT image with no additional phase shifters in the reference arm. To realize this technique, a magnetically actuated probe was adopted. Full range SD-OCT images of a pearl, human fingernail, and human tooth were subsequently obtained using this suggested probe. The scanning range and acquisition speed were 3 mm and 20 frames/s, respectively. PMID:22859100

Min, Eun Jung; Shin, Jun Geun; Lee, Jae Hwi; Yasuno, Yoshiaki; Lee, Byeong Ha

2012-08-01

176

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

CERN Document Server

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.

Grusche, Sascha

2014-01-01

177

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

178

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

Science.gov (United States)

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

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

1998-05-01

179

High power helium cascade arc as an intensity standard in the VUV spectral range from 60 nm to 120 nm  

International Nuclear Information System (INIS)

The calibration of the vuv system response in the spectral range between 60 nm and 120 nm was based on the continuum radiation of a 2 mm 0 pure He arc. The results were compared with the ArI, II and III line emissions of a high current hollow cathode calibrated by means of the electron synchrotron radiation at the Physikalisch Technische Bundesanstalt Berlin

180

Infrared Spectroscopy of Gas-phase Polycyclic Aromatic Hydrocarbon Cations in the 10-50 ?m Spectral Range  

Science.gov (United States)

The gas-phase infrared spectra of four polycyclic aromatic hydrocarbon (PAH) cations have been recorded in the 10-50 ?m (or 1000-200 cm-1) spectral range via IR multiple photon dissociation (IRMPD) spectroscopy. Ionized PAHs are formed by UV laser ionization in an effusive beam and subsequently irradiated with a single pulse of narrowband tunable infrared light produced by the Free-Electron Laser for IntraCavity Experiments FELICE. The ion population is then analyzed in a time-of-flight mass spectrometer. Upon resonance, dissociation is induced so that IR spectra can be recorded by monitoring either the depleted parent ion intensity or the appearance of fragment ions as a function of the wavelength. The intracavity IR fluence enables the recording of IRMPD spectra of strongly bound PAH cations in the hitherto inaccessible far-IR spectral range. Experimental spectra are presented for the radical cations of anthracene, tetracene, pentacene, and coronene. Spectra calculated with density functional theory at the B3LYP/6-311g(2df,2pd) level reproduce IR frequencies reasonably accurately in this spectral range when a uniform scaling factor of 0.94 over the complete 10-50 ?m spectral range is employed. We show that even vibrational modes with a calculated IR intensity lower than 1 km mol-1 can be observed. For the catacondensed PAH cations we find CH out-of-plane bending vibrations involving four adjacent CH groups within a few wavenumbers of 733 cm-1, closely matching the 13.6 ?m UIR band. For the larger systems, pentacene and coronene, we observe a continuous structureless background absorption above 400 cm-1 which is attributed to the high density of IR dipole allowed combination modes for these systems.

Bakker, Joost M.; Redlich, Britta; van der Meer, Alexander F. G.; Oomens, Jos

2011-11-01

 
 
 
 
181

Cascaded Nondegenerate Four-Wave Mixing Technique for High-Power Single-Cycle Pulse Synthesis in the Visible and Ultraviolet Ranges  

CERN Document Server

We present a new technique to synthesize high-power single-cycle pulses in the visible and ultraviolet ranges by coherent superposition of a multiband octave-spanning spectrum obtained by highly-nondegenerate cascaded four-wave mixing of femtosecond pulses in bulk isotropic nonresonant media. The generation of coherent spectra spanning over two octaves in bandwidth is experimentally demonstrated using a thin fused silica slide. Full characterization of the intervening multicolored fields using frequency-resolved optical gating, where multiple cascaded orders have been measured simultaneously for the first time, supports the possibility of direct synthesis of near-single-cycle 2.2 fs visible-UV pulses without recurring to complex amplitude or phase control, which should enable many applications in science and technology.

Weigand, Rosa; Crespo, Helder M

2009-01-01

182

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

183

Spin-spectral-weight distribution and energy range of the parent compound La$_2$CuO$_4$  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The spectral-weight distribution in recent neutron scattering experiments on the parent compound La$_2$CuO$_4$ (LCO), which are limited in energy range to about 450\\,meV, is studied in the framework of the Hubbard model on the square lattice. We find that the higher-energy weight extends to about 566\\,meV and is located at and near the momentum $[\\pi,\\pi]$. Our results confirm that the $U/t$ value suitable to LCO is in the range $U/t\\in (6,8)$. The continuum weight energy-in...

Araujo, M. A. N.; Carmelo, J. M. P.; Sampaio, M. J.; White, S. R.

2012-01-01

184

Data bank of optical properties of biological tissue and blood in the visible and near infrared spectral region  

Science.gov (United States)

The data bank contains optical, ordinary biochemical and biophysical information on 120 venous blood samples of donors, healthy persons, patients with high pathology, 60 tissue samples. The optical parameters include diffuse reflection R((lambda) ) and transmission T((lambda) ) coefficients for optically thick layers, the absorption K((lambda) ) and extinction (epsilon) ((lambda) ) spectra, oxygenation degree CO2, parameter p determined by sizes and shapes of cells and their aggregates, refractive index of a disperse phase relative to surrounding media, and cooperative effects at high relative concentration. The peculiarities in absorption K((lambda) spectra are connected with different pathologies. It is shown from K((lambda) ) that the grade of pathology connected with the concentration of hemoglobin and mithohondrion together with oxygenation degree of blood and tissues, with the pathological hemoglobin's forms and its decomposition products of different levels. Parameter p is an important diagnostic parameter. We consider that it is necessary to include the oxygenation degree and erythrocyte's aggregation parameter to extend the range of common diagnostic parameters of blood by the first rota.

Khairullina, Alphiya Y.; Bui, Lilia; Oleinik, Tatiana V.; Artishevsky, Nelli; Prigoun, Natalia; Sevkovsky, Jakov; Mokhort, Tatiana

1996-12-01

185

Full range complex spectral domain optical coherence tomography for volumetric imaging at 47?000 A-scans per second  

International Nuclear Information System (INIS)

In this paper we demonstrate a high speed spectral domain optical coherence tomography (SDOCT) system capable of achieving full range complex imaging at a line scan rate of 47 kHz. By applying a beam-offset method, a constant modulation frequency is introduced into each B-scan that enables reconstruction of the full range complex SDOCT images of in vivo tissue samples. To make use of the full capacity of the detection camera used in the system, system control software is developed that streams the raw spectral fringe data directly into the computer memory. In order to assess performance of the high speed full range SDOCT system for imaging biological specimen, we present results imaged from the cuticle of the fingernail of a human volunteer in vivo and from chick embryos ex vivo. We also show the high sensitivity advantages of full range complex imaging as compared to conventional SDOCT. To the best of our knowledge, an imaging rate of 47?000 A-scans per second is the highest imaging rate that has ever been reported for full range complex imaging. Notwithstanding, the method reported here has no limitations on the imaging speed and thus offers a useful tool to achieve volumetric imaging of living samples where the high sensitivity region around zero delay line in the system can be utilized for imaging

186

Full range complex spectral domain optical coherence tomography for volumetric imaging at 47 000 A-scans per second  

Science.gov (United States)

In this paper we demonstrate a high speed spectral domain optical coherence tomography (SDOCT) system capable of achieving full range complex imaging at a line scan rate of 47 kHz. By applying a beam-offset method, a constant modulation frequency is introduced into each B-scan that enables reconstruction of the full range complex SDOCT images of in vivo tissue samples. To make use of the full capacity of the detection camera used in the system, system control software is developed that streams the raw spectral fringe data directly into the computer memory. In order to assess performance of the high speed full range SDOCT system for imaging biological specimen, we present results imaged from the cuticle of the fingernail of a human volunteer in vivo and from chick embryos ex vivo. We also show the high sensitivity advantages of full range complex imaging as compared to conventional SDOCT. To the best of our knowledge, an imaging rate of 47 000 A-scans per second is the highest imaging rate that has ever been reported for full range complex imaging. Notwithstanding, the method reported here has no limitations on the imaging speed and thus offers a useful tool to achieve volumetric imaging of living samples where the high sensitivity region around zero delay line in the system can be utilized for imaging.

An, Lin; Subhash, Hrebesh M.; Wang, Ruikang K.

2010-08-01

187

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

Energy Technology Data Exchange (ETDEWEB)

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.

Yoo, Y. S.; Lee, D. H.; Park, C. W.; Park, S. N. [Korea Research Institute of Standards and Science 209 Gajeong-Ro, Yuseong-Gu, Daejon 305-340 (Korea, Republic of)

2013-09-11

188

Effect of index contrasts in the wide spectral-range control of slot waveguide dispersion.  

Science.gov (United States)

Here we examine the waveguide dispersion property of slot waveguides, approaching/analyzing the given problem with respect to the normalized index contrast, ?nslot-core/ncore and ?ncore-clad/ncore between adjacent layers . For two index contrasts of concern, it is found that their contributions to slot waveguide dispersions are substantially different, with ?nslot-core and ?ncore-clad each acting preferentially on short- and long-wavelength regions. Additional degrees of freedom in the waveguide design, such as the effect of absolute refractive index and waveguide geometry are also investigated to enable flexible tuning of the waveguide dispersion. Focusing on the unexplored regime of slot waveguides design in short wavelength (Ta2O5/TiO2/silica slot, either of two-octave spectral width (0.467–1.581 ?m), or of one-octave, near unity coherence |g12(1)| = 1. PMID:22714346

Ryu, Hyungsuk; Kim, Jaehun; Jhon, Young Min; Lee, Seok; Park, Namkyoo

2012-06-01

189

Mapping wetland species and the impact of oil from the Deep Horizon using the Airborne/Visible Imaging Spectrometer and Multiple Endmember Spectral Mixture Analysis  

Science.gov (United States)

Between April 20, 2010 and July 15, 2010 an estimated 4.4 million barrels of oil leaked from the Maconda well, making the Deep Horizon oil spill the largest in US history. In response to a need to determine the distribution of wetland plant species and quantify their condition prior to, during and after oil reached the shore, the Airborne/Visible Infrared Imaging Spectrometer (AVIRIS) was deployed multiple times in the gulf on high altitude and low altitude airborne platforms. Significant research questions included 1) What is the distribution of key wetland species in the impacted area?; 2) which areas were impacted by oil, when and to what extent?; 3) how much oil must be present to be detected in various cover types? and 4) which wetland species are more sensitive to oil? In an effort to answer some of these questions, we applied Multiple Endmember Spectral Mixture Analysis (MESMA) to AVIRIS data acquired prior to significant impacts in May, 2010 and after oil had reached wetlands in late summer and fall, 2010. Reference polygons for species dominants were located on the images and used to build a spectral library for all dominant wetland species and surface types. This spectral library was augmented by field spectra, acquired using a contact probe for senesced plants materials and beach sands. Spectra of heavily oiled surfaces were identified using the Hydrocarbon Index to identify potential oil endmembers and the Cellulose Absorption Index to discriminate oil from Non-photosynthetic Vegetation (NPV). Wetland species and cover fractions for Green Vegetation (GV), NPV, soils/beaches, oil and water were mapped using MESMA applied to images acquired in the Birds Foot Delta, Chandeleur Islands and Barataria Bay. Species maps, showing dominant species such as Phragmites australis, Spartina alternifolia and S. patens proved to be accurate. OIl was mapped along coastal areas of Barataria Bay, expressed as high oil fractions. However, significant confusion was also observed between oiled vegetation and senesced vegetation, either resulting from oil-induced mortality or natural senescence.

Roberts, D. A.; Beland, M.; Kokaly, R. F.; Couvillion, B.; Ustin, S.; Peterson, S.

2011-12-01

190

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

Energy Technology Data Exchange (ETDEWEB)

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: Black-Right-Pointing-Pointer The strongest bands of FLUORO molecules can be assigned as {pi} {yields} {pi}{sup Asterisk-Operator} transitions. Black-Right-Pointing-Pointer A small red-shift indicates a weak exciton coupling of chromophores. Black-Right-Pointing-Pointer No n {yields} {pi}{sup Asterisk-Operator} transition occurs due to the rigidity of the ring system of the molecules. Black-Right-Pointing-Pointer The HOMO, LUMO, and E{sub g} values have been found to be independent of solvent effect.

Lakshmi Praveen, P. [Liquid Crystal Research Laboratory, Post-Graduate Department of Physics, Andhra Loyola College, Vijayawada 520 008, A.P. (India); Ojha, Durga P., E-mail: durga_ojha@hotmail.com [Liquid Crystal Research Laboratory, Post-Graduate Department of Physics, Andhra Loyola College, Vijayawada 520 008, A.P. (India)

2012-08-15

191

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.

192

Fourier transform measurements of H218O and HD18O in the spectral range 1000-2300 cm-1  

International Nuclear Information System (INIS)

The spectra of water vapor enriched by 18O were recorded in the 1000-2300 cm-1 spectral range, which corresponds to the spectral region studied by IASI instrument (Infrared Atmospheric Sounding Spectrometer) instrument. The spectra were recorded by a step by step Fourier Transform Spectrometer (FTS) at room temperature with absorption path lengths up to 36 m. Positions, intensities and self broadening coefficients of about 1800 lines of H218O and 900 of HD18O were analyzed and all the transitions were assigned. This paper focuses on lines intensities and comparisons with data from literature are presented. An average difference of 10% with HITRAN2008 database H218O line intensities is found with a maximum discrepancy of about 25% for the ?1-?2 band.

193

Ultraviolet and visible range plasmonics in the topological insulator Bi1.5Sb0.5Te1.8Se1.2  

Science.gov (United States)

The development of metamaterials, data processing circuits and sensors for the visible and ultraviolet parts of the spectrum is hampered by the lack of low-loss media supporting plasmonic excitations. This has driven the intense search for plasmonic materials beyond noble metals. Here we show that the semiconductor Bi1.5Sb0.5Te1.8Se1.2, also known as a topological insulator, is also a good plasmonic material in the blue-ultraviolet range, in addition to the already-investigated terahertz frequency range. Metamaterials fabricated from Bi1.5Sb0.5Te1.8Se1.2 show plasmonic resonances from 350 to 550?nm, while surface gratings exhibit cathodoluminescent peaks from 230 to 1,050?nm. The observed plasmonic response is attributed to the combination of bulk charge carriers from interband transitions and surface charge carriers of the topological insulator. The importance of our result is in the identification of new mechanisms of negative permittivity in semiconductors where visible range plasmonics can be directly integrated with electronics.

Ou, Jun-Yu; So, Jin-Kyu; Adamo, Giorgio; Sulaev, Azat; Wang, Lan; Zheludev, Nikolay I.

2014-10-01

194

Ultraviolet and visible range plasmonics in the topological insulator Bi1.5Sb0.5Te1.8Se1.2.  

Science.gov (United States)

The development of metamaterials, data processing circuits and sensors for the visible and ultraviolet parts of the spectrum is hampered by the lack of low-loss media supporting plasmonic excitations. This has driven the intense search for plasmonic materials beyond noble metals. Here we show that the semiconductor Bi1.5Sb0.5Te1.8Se1.2, also known as a topological insulator, is also a good plasmonic material in the blue-ultraviolet range, in addition to the already-investigated terahertz frequency range. Metamaterials fabricated from Bi1.5Sb0.5Te1.8Se1.2 show plasmonic resonances from 350 to 550?nm, while surface gratings exhibit cathodoluminescent peaks from 230 to 1,050?nm. The observed plasmonic response is attributed to the combination of bulk charge carriers from interband transitions and surface charge carriers of the topological insulator. The importance of our result is in the identification of new mechanisms of negative permittivity in semiconductors where visible range plasmonics can be directly integrated with electronics. PMID:25295413

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

2014-01-01

195

Simplified sedimentation process for 3D photonic thick layers/bulk crystals with a stop-band in the visible range  

International Nuclear Information System (INIS)

Self-organization of nano-size spherical particles in opal-like structures has been demonstrated to be a powerful mean to build three-dimensional (3D) photonic crystal. We here present a simplified sedimentation process leading to photonic crystal layer with a non-absolute bandgap in the visible range. The stacking organization is cross checked directly by classical optical microscopy (COM), atomic force microscopy (AFM) and scanning electron microscopy (SEM), giving a detailed scheme of the short range and long range organization, and indirectly by reflection/transmission spectroscopy for different incidence angles. The results show a very good resonance associated with a low cost deposition technique. The implementation of our method for further application like photonic waveguides is also discussed

196

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)

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 at the measurement site 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.

J. Jung

2010-02-01

197

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)

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.

J. Jung

2010-06-01

198

Spectral detectability of Ca- and Mg-sulfates in Martian bright soils in the 4 5 ?m wavelength range  

Science.gov (United States)

Chemical analyses of soil samples performed at different landing sites on Mars suggest the presence of sulfate minerals. These minerals are also thought to be present in the globally mixed Martian bright soils covering large areas of the planet. However, remote soil spectra have so far provided only tentative identification of sulfates regarding mineral types and abundances. This paper concentrates on the detectability of four Ca- and Mg-sulfates (anhydrite, gypsum, kieserite, hexahydrite) in the 4-5 ?m range of Martian remote soil spectra. This spectral range is important for sulfate detection as most fine-grained sulfates exhibit significant absorption bands between 4 and 5 ?m, independent of the texture of the host soils (e.g., loose powdered or cemented soils). Furthermore, this is the spectral range for which the Planetary Fourier Spectrometer (PFS) and Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) instruments onboard ESA/Mars Express mission provide high spectral and spatial resolution data. Laboratory near- and mid-IR reflectance spectra of the pure sulfates and their mixtures with a terrestrial Martian soil analog were acquired. The results show that even the smallest amount of admixed sulfate (˜5 wt%) generates significant absorption features in the portion of the 4-5 ?m range not covered by the saturated Martian atmospheric CO 2 absorption band between 4.2 and 4.4 ?m. Model calculations of the influence of emitted surface radiation on the detectability of sulfate features show that the depth of the features decreases strongly with increasing surface temperature of an observed area resulting in the fact that all sulfates are spectrally hidden at surface temperatures around 270 K even at ˜14 or ˜25 wt% sulfate content in the soils. Sulfates become increasingly detectable depending on the sulfate content if the surface temperature is below 260 K. The outcome of this work helps to constrain the conditions needed for remote detection of sulfates within Martian bright soils in the 4-5 ?m range.

Witzke, A.; Arnold, G.; Stöffler, D.

2007-03-01

199

Aperiodic normal-incidence antimony-based multilayer mirrors in the 8 - 13-nm spectral range  

International Nuclear Information System (INIS)

The optical properties of several materials were analysed from the standpoint of fabrication of broadband normal-incidence multilayer mirrors possessing maximal uniform reflectivity in the 8-13-nm range. By solving the inverse problem of multilayer optics we show that aperiodic Sb/(B4C, Sc, Si) multilayer structures optimised for maximum uniform reflectivity in the 8-13-nm range are able to afford a normal-incidence reflectivity R?10 % throughout this range. The best results are exhibited by the pair Sb/B4C, for which the average reflection coefficient amounts to about 13%. The dependence of optimisation result on the programmable limitation on the minimal layer thickness in the multilayer structure was numerically investigated. An empirical rule was established whereby setting the lower bound for a layer thickness at a level ??min/4 (in this case, ?min = 8 nm) does not result in an appreciable lowering of attainable uniform reflectivity. (quantum electronic devices)

200

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1995-12-31

 
 
 
 
201

Operation of linac based FELs in IR- and visible-range at the FELI (Free Electron Laser Research Institute, Inc.)  

International Nuclear Information System (INIS)

Two infrared free electron lasers (FELs) facilities covering the wavelength range of 1-20 ?m are opened for FEL users in this October. We are also challenging 0.3 ?m-FEL oscillations using a 2.68m undulator (?u=4cm) installed at the 160-MeV beam line of the FELI linac with a thermionic gun. A 0.52-?m spontaneous radiation of 0.1W has been observed using a 145-MeV electron beam and the undulator. (author)

202

The spectral characteristics of Gd2SiO5:Eu3+ in VUV-UV range  

International Nuclear Information System (INIS)

Synchrotron radiation source was used to investigated the spectral characteristics of Gd2SiO5:Eu3+ in VUV-UV range. The various energy transfers at room temperature and 10 K, including from host or Gd3+ ions to Eu3+ ions and transfer between Eu3+ ions at two different lattice sites, were discussed. In addition the emission spectra under 186 nm and 276 nm excitation were compared from the view of quantum cutting. The results indicate that Gd2SiO5:Eu3+ is a kind of material with potential high efficiency quantum cutting

203

New defect design in index guiding holey fiber for uniform birefringence and negative flat dispersion over a wide spectral range.  

Science.gov (United States)

A novel silica index guiding holey fiber (IGHF) design is proposed utilizing a new defect structure that is composed of an elliptic high index ring structure and an elliptic air-hole at the center with triangular lattice structure. The proposed IGHF showed unique modal properties such as uniform and high birefringence over a wide spectral range and single polarization single mode (SPSM) guidance along with a flat negative chromatic dispersion. Optical waveguide properties were numerically analyzed using the plane wave expansion method in terms of mode intensity distribution, modal birefringence, chromatic dispersion for the new defect structural parameters. PMID:19498612

Kim, Soan; Paek, U; Oh, Kyunghwan

2005-08-01

204

Light absorption in undoped congruent and magnesium-doped lithium niobate crystals in the visible wavelength range  

Science.gov (United States)

Light absorption measurements of nominally undoped congruent lithium niobate crystals (CLN) as well as 5 mol% magnesium-oxide-doped lithium niobate (MgO:LN) crystals were performed in the light wavelength range of 350 to 800 nm. Absorption spectra reveal that—besides iron (Fe) impurities—chromium (Cr) impurities of less than 0.5 wt. ppm concentration contribute significantly to the total optical absorption in the CLN crystals with a maximum of 0.035 cm-1 around 500 nm. The axial distribution of Cr within a CLN boule is examined, revealing that the bottom part of the boule contains less Cr and therefore light absorption is reduced as well. In the case of the MgO:LN crystals, Cr impurities also contribute significantly to the total optical absorption, which is on the order of 0.025 cm-1 for ordinarily polarized light and 0.015 cm-1 for extraordinarily polarized light around 500 nm.

Schwesyg, J. R.; Kajiyama, M. C. C.; Falk, M.; Jundt, D. H.; Buse, K.; Fejer, M. M.

2010-07-01

205

Retrieval interval mapping: a tool to visualize the impact of the spectral retrieval range on differential optical absorption spectroscopy evaluations  

Directory of Open Access Journals (Sweden)

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. Due to the wide range of measurement conditions, atmospheric compositions and instruments used, a specific challenge of a DOAS retrieval is to optimize the retrieval parameters for each specific case and particular trace gas of interest. Of these parameters, the retrieval wavelength range is one of the most important ones. Although for many trace gases the overall dependence of common DOAS retrieval on the evaluation wavelength interval is known, a systematic approach for finding the optimal retrieval wavelength range and quantitative assessment is missing. Here we present a novel tool to visualize the effect of different evaluation wavelength ranges. It is based on mapping retrieved column densities in the retrieval wavelength space and thus visualizing the consequences of different choices of spectral retrieval ranges caused by slightly erroneous absorption cross sections, cross correlations and instrumental features. Based on the information gathered, an optimal retrieval wavelength range may be determined systematically.

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

L. Vogel

2013-02-01

206

Full anterior segment biometry with extended imaging range spectral domain optical coherence tomography at 1340 nm.  

Science.gov (United States)

We demonstrate an extended-imaging-range anterior-segment optical coherence tomography (eAS-OCT) system for the biometric assessment of full AS in human eye. This newly developed eAS-OCT operating at 1340-nm wavelength band is simultaneously capable of an imaging speed of 120 kHz A-line scan rate, an axial resolution of 7.2 ?m, and an extended imaging range of up to 16 mm in air. Imaging results from three healthy subjects and one subject with a narrow-angle demonstrate the instrument's utility. With this system, it can provide anatomical dimensions of AS, including central corneal thickness, anterior chamber width, anterior chamber depth, crystalline lens vault, crystalline lens thickness, angle opening distance (AOD500/AOD750), and the area described by the trabecular-iris space (TISA500/TISA750) at 500/750???m. We also use eAS-OCT to image and quantify dynamic functional changes of the AS in response to a light stimulus that induces physiological pupillary changes as well as accommodative efforts that induce lens changes. The results show that the described eAS-OCT is able to provide full anatomical biometry for AS and is useful for the studies where the dynamic response of AS compartment to certain stimulus is required. PMID:24752381

Li, Peng; Johnstone, Murray; Wang, Ruikang K

2014-04-01

207

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

Science.gov (United States)

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.

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

2004-07-01

208

Estimation of a radiative transfer model in the longwave spectral range: sensitivity study and application to real cases  

Science.gov (United States)

The aerosol radiative effect in the longwave spectral range is often neglected in atmospheric aerosol forcing studies, hence very few researches are conducted in this field at local scale, and even less at regional scale. However, strong absorbing aerosols, like mineral dust, can have a small, but non-negligible heating effect in the longwave spectral range which can slightly counteract the aerosol cooling effect in the shortwave. The objective of this research is to perform a sensitivity study of an aerosol radiative transfer model as a function of dust particle properties. GAME model1, which can compute vertically resolved shortwave and longwave values of aerosol radiative forcing, is used. Before developing the sensitivity analysis, the aerosol radiative transfer model is validated by comparing its outputs with results published previously. Radiative forcing simulations in the longwave have shown an important sensitivity to the following parameters: aerosol size and refractive index, aerosol vertical distribution, humidity, surface temperature and albedo. A couple of strong mineral dust intrusion observed by means of lidar and sun-photometer are also presented in terms of shortwave and longwave radiative forcing.

Sicard, Michaël.; Bertolín, Santi; Mallet, Marc; Dubuisson, Philippe; Comerón, Adolfo

2013-10-01

209

Broad-spectral-range synchronized flat-top arrayed-waveguide grating applied in a 225-channel cascaded spectrometer.  

Science.gov (United States)

We present a new synchronized design for flattening the passband of an arrayed-waveguide grating (AWG) over a broad wavelength range of 90 nm. A wavelength-insensitive 3-dB balanced coupler is designed to be used in duplicate in a Mach-Zehnder interferometer (MZI); the phase deviation created by one of the balanced couplers is cancelled by flipping the other coupler around. This MZI is arranged in tandem with the AWG such that the output signal of the MZI is the input signal of the AWG. We demonstrate a 5-channel, 18-nm-spacing AWG with a 0.5-dB bandwidth of 12 nm over a 90-nm spectral range. A low-loss cascaded AWG system is demonstrated by using the MZI-synchronized flat-top AWG as a primary filter. PMID:23038381

Akca, B I; Doerr, C R; Sengo, G; Wörhoff, K; Pollnau, M; de Ridder, R M

2012-07-30

210

Observations of short-range, high-LET recoil tracks in CR-39 plastic nuclear track detector by visible light microscopy  

Energy Technology Data Exchange (ETDEWEB)

Using standard visible light microscopy, we are able to observe particle tracks produced by <10 {mu}m range target fragment recoils in CR-39 plastic nuclear track detector (PNTD) following short chemical etching (bulk etch B {<=}1 {mu}m). In accelerator irradiations, targets of varying composition, including a number of elemental targets of high Z, were exposed in contact with layers of CR-39 PNTD to beams of 60 MeV, 230 MeV, and 1 GeV protons at doses of 10-50 Gy. Chemical etching of CR-39 under standard conditions (50 {sup o}C, 6.25 N NaOH) for 2-4 h (removed layer B = 0.5-1.0 {mu}m) yielded secondary track densities of 10{sup 5}-10{sup 6} cm{sup -2} observable under a standard optical microscope with 500x-800x magnification. Ordinarily such a short duration etch would not be expected to enlarge the tracks sufficiently for them to be resolved by visible light optics. However, due to the short-range of the particles, a longer chemical processing would have over-etched the tracks until they were no longer recognizable. The tracks we observe in CR-39 PNTD irradiated in these experiments are the result of residual heavy recoil fragments returning to equilibrium via evaporation processes following proton-induced knock out of light particles via preequilibrium processes. Because the heavy recoil particles are very near the end of their ranges (i.e. in the Bragg peak), their LET is extremely high and changes rapidly. Consequently, the tracks they produce in CR-39 PNTD often take the form of long tubes rather than the conical etch pits produced by higher energy particles.

Benton, E.R., E-mail: eric.benton@okstate.ed [Dept. of Physics, Oklahoma State University, 1110 S. Innovation Way, 100, Stillwater, OK 74078 (United States); Johnson, C.E. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); DeWitt, J. [Dept. of Physics, Oklahoma State University, 1110 S. Innovation Way, 100, Stillwater, OK 74078 (United States); Yasuda, N. [National Institute of Radiological Sciences, Chiba (Japan); Benton, E.V. [Dept. of Physics, University of San Francisco, San Francisco, CA 94117 (United States); Moyers, M.H. [Proton Therapy, Inc., Colton, CA 92324 (United States); Frank, A.L. [Dept. of Physics, University of San Francisco, San Francisco, CA 94117 (United States)

2011-05-15

211

Visible-range hybrid femtosecond systems based on a XeF(C-A) amplifier: state of the art and prospects  

Energy Technology Data Exchange (ETDEWEB)

Results of experimental and theoretical investigations of the hybrid (solid state/gas) visible-range femtosecond systems THL-100 (IHCE SB RAS) and THL-30 (P.N. Lebedev Physics Institute) based on a Ti : sapphire front end and a photochemical XeF(C-A) amplifier are reported. The front end generates 50-fs optical pulses with the second-harmonic (475 nm) energy of up to 5 mJ. The active medium of the amplifier is produced in a mixture XeF{sub 2} - N{sub 2} subjected to VUV radiation of xenon excited by an electron beam. The computer model is developed for calculating parameters of the XeF(C - A) amplifier, which is in a good agreement with experiments. In the THL-100 system with the 25-cm output aperture of the XeF(C-A) amplifier, a record visible-range femtosecond radiation peak power of 14 GW was obtained in a 50-fs pulse with the time contrast of above 10{sup 8}. The measured power of an amplified spontaneous emission of the XeF(C-A) amplifier in the angle of 0.2 mrad was 32 W. The result obtained testifies that the hybrid approach to the development of ultrahigh-power systems provides a high time contrast of radiation (greater than 10{sup 12} for the projected peak power of 100 TW). In the THL-30 system, prospects for shortening an amplified femtosecond pulse are studied and it is experimentally shown that by compensating a third-order dispersion in a hybrid system one can obtain pulses with duration of at least 27 fs with a recompression of amplified pulses in bulk glass. Also, a new phenomenon was observed of spectrum broadening and self-compression of negatively chirped femtosecond pulses in the visible range under a nonlinear interaction of wide-aperture beams with fused silica. This result opens prospects for development of the new methods of selfcompression for femtosecond pulses that are lacking physical limitations on pulse energy and realisation of self-compression of amplified pulses in the output window of the XeF(C-A) amplifier. (extreme light fields and their applications)

Alekseev, S V; Aristov, A I; Grudtsyn, Ya V; Ivanov, N G; Koval' chuk, B M; Losev, B F; Mamaev, S B; Mesyats, Gennadii A; Mikheev, L D; Panchenko, Yu N; Polivin, A V; Stepanov, S G; Ratakhin, N A; Yalovoi, V I; Yastremskii, Arkadii G

2013-03-31

212

Visible-range hybrid femtosecond systems based on a XeF(C-A) amplifier: state of the art and prospects  

Science.gov (United States)

Results of experimental and theoretical investigations of the hybrid (solid state/gas) visible-range femtosecond systems THL-100 (IHCE SB RAS) and THL-30 (P.N. Lebedev Physics Institute) based on a Ti : sapphire front end and a photochemical XeF(C-A) amplifier are reported. The front end generates 50-fs optical pulses with the second-harmonic (475 nm) energy of up to 5 mJ. The active medium of the amplifier is produced in a mixture XeF2 - N2 subjected to VUV radiation of xenon excited by an electron beam. The computer model is developed for calculating parameters of the XeF(C - A) amplifier, which is in a good agreement with experiments. In the THL-100 system with the 25-cm output aperture of the XeF(C-A) amplifier, a record visible-range femtosecond radiation peak power of 14 GW was obtained in a 50-fs pulse with the time contrast of above 108. The measured power of an amplified spontaneous emission of the XeF(C-A) amplifier in the angle of 0.2 mrad was 32 W. The result obtained testifies that the hybrid approach to the development of ultrahigh-power systems provides a high time contrast of radiation (greater than 1012 for the projected peak power of 100 TW). In the THL-30 system, prospects for shortening an amplified femtosecond pulse are studied and it is experimentally shown that by compensating a third-order dispersion in a hybrid system one can obtain pulses with duration of at least 27 fs with a recompression of amplified pulses in bulk glass. Also, a new phenomenon was observed of spectrum broadening and self-compression of negatively chirped femtosecond pulses in the visible range under a nonlinear interaction of wide-aperture beams with fused silica. This result opens prospects for development of the new methods of selfcompression for femtosecond pulses that are lacking physical limitations on pulse energy and realisation of self-compression of amplified pulses in the output window of the XeF(C-A) amplifier.

Alekseev, S. V.; Aristov, A. I.; Grudtsyn, Ya V.; Ivanov, N. G.; Koval'chuk, B. M.; Losev, B. F.; Mamaev, S. B.; Mesyats, Gennadii A.; Mikheev, L. D.; Panchenko, Yu N.; Polivin, A. V.; Stepanov, S. G.; Ratakhin, N. A.; Yalovoi, V. I.; Yastremskii, Arkadii G.

2013-03-01

213

Visible-range hybrid femtosecond systems based on a XeF(C–A) amplifier: state of the art and prospects  

International Nuclear Information System (INIS)

Results of experimental and theoretical investigations of the hybrid (solid state/gas) visible-range femtosecond systems THL-100 (IHCE SB RAS) and THL-30 (P.N. Lebedev Physics Institute) based on a Ti : sapphire front end and a photochemical XeF(C–A) amplifier are reported. The front end generates 50-fs optical pulses with the second-harmonic (475 nm) energy of up to 5 mJ. The active medium of the amplifier is produced in a mixture XeF2 – N2 subjected to VUV radiation of xenon excited by an electron beam. The computer model is developed for calculating parameters of the XeF(C – A) amplifier, which is in a good agreement with experiments. In the THL-100 system with the 25-cm output aperture of the XeF(C–A) amplifier, a record visible-range femtosecond radiation peak power of 14 GW was obtained in a 50-fs pulse with the time contrast of above 108. The measured power of an amplified spontaneous emission of the XeF(C–A) amplifier in the angle of 0.2 mrad was 32 W. The result obtained testifies that the hybrid approach to the development of ultrahigh-power systems provides a high time contrast of radiation (greater than 1012 for the projected peak power of 100 TW). In the THL-30 system, prospects for shortening an amplified femtosecond pulse are studied and it is experimentally shown that by compensating a third-order dispersion in a hybrid system one can obtain pulses with duration of at least 27 fs with a recompression of amplified pulses in bulk glass. Also, a new phenomenon was observed of spectrum broadening and self-compression of negatively chirped femtosecond pulses in the visible range under a nonlinear interaction of wide-aperture beams with fused silica. This result opens prospects for development of the new methods of selfcompression for femtosecond pulses that are lacking physical limitations on pulse energy and realisation of self-compression of amplified pulses in the output window of the XeF(C–A) amplifier. (extreme light fields and their applications)

214

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

Directory of Open Access Journals (Sweden)

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.

T. Wagner

2010-03-01

215

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

Directory of Open Access Journals (Sweden)

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.

T. Wagner

2010-07-01

216

An in-vacuum wiggler for SOLEIL Hard X-rays spectral range  

International Nuclear Information System (INIS)

The production of Hard X-rays has become a tricky problem on medium energy storage rings. It requires Insertion Devices (IDs) with high magnetic field and a large number of periods. To cover the 20-50 keV photon energy range at SOLEIL (2.75 GeV), an in-vacuum wiggler (WSV50) has been preferred to a superconducting ID. The wiggler is composed of 38 periods of 50 mm producing a 2.1 T field at a minimum magnetic gap of 5.5 mm. To minimize the magnetic forces acting between magnet arrays (8.5 tons), a compensation system composed of non magnetic springs has been mounted apart from the magnet system to reduce the mechanical deformations. The wiggler has been assembled step by step by means of a genetic algorithm which minimizes the magnetic errors measured with a flipping coil. This paper presents the mechanical and magnetic design of the wiggler as well as the construction and the magnetic measurements.

217

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization  

Energy Technology Data Exchange (ETDEWEB)

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

Thoen, D. J.; Bongers, W. A.; Westerhof, E.; Baar, M. R. de; Berg, M. A. van den; Beveren, V. van; Goede, A. P. H.; Graswinckel, M. F.; Schueller, F. C. [Association EURATOM-FOM, Trilateral Euregio Cluster, FOM-Institute for Plasma Physics Rijnhuizen, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); Oosterbeek, J. W.; Buerger, A. [Association EURATOM-FZJ, Institut fuer Energieforschung-Plasmaphysik, Forschungszentrum Juelich GMBH, 52425 Juelich (Germany); Hennen, B. A. [Association EURATOM-FOM, Trilateral Euregio Cluster, FOM-Institute for Plasma Physics Rijnhuizen, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); Control Systems Technology Group, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven (Netherlands)

2009-10-15

218

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization  

International Nuclear Information System (INIS)

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

219

Direct measurement of the complex refractive index of thin foils in the XUV spectral range by point diffraction interferometry  

Science.gov (United States)

In this paper, we demonstrate the application of point diffraction interferometry to determine the complex refractive index of thin foils in the extreme ultraviolet spectral range. Results are cross-checked by an independent interferometric measurement of the refractive index and a direct transmission measurement of the foils. As the light source, we apply high-order harmonics of a titanium-sapphire laser generated in a gas jet. This interferometric method has the advantage to simultaneously and directly deliver the refractive and absorptive part of the refractive index without relying on the Kramers-Kronig relations or the Fresnel equations. We present results for a set of materials (aluminum, silicon, germanium, boron, and parylene), which are of interest for the design of bandpass filters or multilayer coatings.

Hemmers, D.; Benzid, M.; Pretzler, G.

2012-07-01

220

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

CERN Document Server

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.

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

1999-01-01

 
 
 
 
221

Transmission imaging of sodium in the vacuum ultra-violet spectral range: new application for an intense VUV source  

Science.gov (United States)

Metallic sodium (Na) was proposed as a transparent material in the vacuum ultra-violet (VUV) spectral range in 1930s and in 1960s. However no clear transmission has ever been demonstrated. In this paper we describe firstly the direct measurement of actual transmittance of a sodium samples in a spectral range longer than 115 nm which corresponds to the shortest transmission wavelength of magnesium fluoride (MgF2) windows, resulting in several tens of % transmittance of a 3 mm-thick solid sodium sample including MgF2 windows at the wavelength of ~120 nm. We also find very weak temperature dependency of the transmittance up to 150 degrees centigrade where the solid sample is melted at 97 degrees. The measured transmittance pushes us to make a simple imaging experiment illuminated by the VUV light through a 2-mm thick sodium sample, resulting in obtaining a clear image composed of 100 ?m diameter tungsten mesh recorded on a two dimensional Charge Coupled Device detector. The result also opens a way to construct an optical imaging device for objects inside or through a solid or a liquid sodium medium. According to the present experiment, we can make a continuous real time transmission imaging for a liquid sodium sample if we use proper optical setup including an intense continuous VUV source or high repetition rated intense coherent source for holographic data acquisition. Such an experiment opens up a way to perform transmission imaging through or inside a sodium medium for characterization of hydrodynamic and material properties.

Daido, Hiroyuki; Suzuki, Yoji; Kawachi, Tetsuya; Fukuda, Takeshi; Nakagiri, Toshio; Kaku, Masanori; Kubodera, Shoichi; Pirozhkov, Alexander S.

2013-09-01

222

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

Directory of Open Access Journals (Sweden)

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.

S. A. Buehler

2012-07-01

223

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

Directory of Open Access Journals (Sweden)

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.

S. A. Buehler

2012-02-01

224

Multispectral measurement of contrast in tissue-mimicking phantoms in near-infrared spectral range of 650 to 1600 nm.  

Science.gov (United States)

In order to identify the optimal imaging conditions for the highest spatial contrast in biological tissue, we explored the properties of a tissue-mimicking phantom as a function of the wavelengths in a broad range of near-infrared spectra (650 to 1600 nm). Our customized multispectral hardware, which featured a scanning transmission microscope and imaging spectrographs equipped with silicon and InGaAs charge-coupled diode array detectors, allowed for direct comparison of the Michelson contrast obtained from a phantom composed of a honeycomb grid, Intralipid, and India ink. The measured contrast depended on the size of the grid, luminance, and the wavelength of measurements. We demonstrated that at low thickness of the phantom, a reasonable contrast of the objects can be achieved at any wavelength between 700 and 1400 nm and between 1500 and 1600 nm. At larger thicknesses, such contrast can be achieved mostly between 1200 and 1350 nm. These results suggest that distinguishing biological features in deep tissue and developing contrast agents for in vivo may benefit from imaging in this spectral range. PMID:25104414

Salo, Daniel; Zhang, Hairong; Kim, David M; Berezin, Mikhail Y

2014-08-01

225

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

Science.gov (United States)

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 ? 50. It has been used at the LULI-2000 laser facility at E?cole Polytechnique (France) to measure the ?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. PMID:23126955

Reverdin, Charles; Thais, Frédéric; Loisel, Guillaume; Busquet, M; Bastiani-Ceccotti, S; Blenski, T; Caillaud, T; Ducret, J E; Foelsner, W; Gilles, D; Gilleron, F; Pain, J C; Poirier, M; Serres, F; Silvert, V; Soullie, G; Turck-Chieze, S; Villette, B

2012-10-01

226

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)

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.

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

227

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

International Nuclear Information System (INIS)

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 ? 50. It has been used at the LULI-2000 laser facility at École Polytechnique (France) to measure the ?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.

228

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

Science.gov (United States)

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 ?E/?E? ˜ 50. It has been used at the LULI-2000 laser facility at École Polytechnique (France) to measure the ?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.

Reverdin, Charles; Thais, Frédéric; Loisel, Guillaume; Busquet, M.; Bastiani-Ceccotti, S.; Blenski, T.; Caillaud, T.; Ducret, J. E.; Foelsner, W.; Gilles, D.; Gilleron, F.; Pain, J. C.; Poirier, M.; Serres, F.; Silvert, V.; Soullie, G.; Turck-Chieze, S.; Villette, B.

2012-10-01

229

Visible and infrared linear detector arrays for the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)  

Science.gov (United States)

The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument uses four separate focal plane assemblies consisting of line array detectors that are multiplexed to a common J-FET preamp using a FET switch multiplexing (MUX) technique. A 32-element silicon line array covers the spectral range from 0.41 to 0.70 microns. Three additional 64-element indium antimonide (InSb) line arrays cover the spectral range from 0.68 to 2.45 microns. The spectral sampling interval per detector element is nominally 9.8 nm, giving a total of 224 spectral channels. All focal planes operate at liquid nitrogen temperature and are housed in separate dewars. Electrical performance characteristics include a read noise of less than 1000 e(-) in all channels, response and dark nonuniformity of 5 percent peak to peak, and quantum efficiency of greater than 60 percent.

Bailey, Gary C.

1988-01-01

230

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

Science.gov (United States)

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

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

2014-03-01

231

A high resolution, multi-epoch spectral atlas of peculiar stars including RAVE, GAIA and HERMES wavelength ranges  

CERN Document Server

We present an Echelle+CCD, high S/N, 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 Ang, and includes the RAVE, Gaia and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of observed stars. A total of 425 spectra of peculiar stars are presented, which have been collected during 56 observing nights between November 1998 and August 2002. 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, spectro-photometric 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 the planning for and training...

Tomasella, L; Zwitter, T

2010-01-01

232

Heteroepitaxial growth of GaSb nanotrees with an ultra-low reflectivity in a broad spectral range.  

Science.gov (United States)

We report on the growth of GaSb nanotrees on InAs { ?1 ?1 ?1}(B) substrates by chemical beam epitaxy. GaSb nanotrees form by the nucleation of Ga droplets on the surface of (B) oriented GaSb nanowires followed by the epitaxial growth of branches catalyzed by these Ga droplets. In the tip region, the trunks of the GaSb nanotrees are periodically twinned, which is attributed to a change of the effective V/III ratio at the later stage of growth as a consequence of the change in surface structure. The reflectivity of a forest of nanotrees was measured for a broad spectral range and compared to the reflectivity of a GaSb ( ?1 ?1 ?1)(B) wafer and of GaSb nanowires. At wavelengths from 500 to 1700 nm, the presence of GaSb nanotrees decreased the reflection by three orders of magnitude compared to a blank GaSb substrate. PMID:22432874

Yan, Chenglin; Li, Xiaopeng; Zhou, Keya; Pan, Anlian; Werner, Peter; Mensah, Samuel L; Vogel, Alexander T; Schmidt, Volker

2012-04-11

233

Multiple fiber Bragg grating sensor network with a rapid response and wide spectral dynamic range using code division multiple access  

Science.gov (United States)

Fiber Bragg grating (FBG) sensor networks have been intensively researched in optical sensor area and it developed in wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies which was adopted for its interrogating many optical sensors. In particular, WDM technology can be easily employed to interrogate FBG sensor however, the number of FBG sensors is limited. On the other hand, the TDM technique can extremely expand the number of sensor because the FBG sensors have same center wavelength. However, it suffers from a reduced sensor output power due to low reflectivity of FBG sensor. In this paper, we proposed and demonstrated the FBG sensor network based on code division multiple access (CDMA) with a rapid response and wide spectral dynamic range. The reflected semiconductor optical amplifier (RSOA) as a light source was directly modulated by the generated pseudorandom binary sequence (PRBS) code and the modulated signal is amplified and goes through FBG sensors via circulator. When the modulated optical signal experienced FBG sensor array, the optical signal which was consistent with center wavelength of FBGs is reflected and added from each sensors. The added signal goes into dispersion compensating fiber (DCF) as a dispersion medium. After through the DCF, the optical signal is converted into electrical signal by using photodetector (PD). For separate individual reflected sensor signal, the sliding correlation method was used. The proposed method improves the code interference and it also has advantages such as a large number of sensors, continuously measuring individual sensors, and decreasing the complexity of the sensor network.

Kim, Youngbok; Jeon, Sie-Wook; Park, Chang-Soo

2011-05-01

234

Quantum key distribution using quantum dot single-photon emitting diodes in the red and near infrared spectral range  

International Nuclear Information System (INIS)

We report on in-lab free space quantum key distribution (QKD) experiments over 40 cm distance using highly efficient electrically driven quantum dot single-photon sources emitting in the red as well as near-infrared spectral range. In the case of infrared emitting devices, we achieve sifted key rates of 27.2 kbit s-1 (35.4 kbit s-1) at a quantum bit error rate (QBER) of 3.9% (3.8%) and a g(2)(0) value of 0.35 (0.49) at moderate (high) excitation. The red emitting diodes generate sifted keys at a rate of 95.0 kbit s-1 at a QBER of 4.1% and a g(2)(0) value of 0.49. This first successful proof of principle QKD experiment based on electrically operated semiconductor single-photon sources can be considered as a major step toward practical and efficient quantum cryptography scenarios. (paper)

235

Temperature dependent dielectric function in the near-infrared to vacuum-ultraviolet ultraviolet spectral range of alumina and yttria stabilized zirconia thin films  

Science.gov (United States)

The dielectric function of nano-/polycrystalline alumina and yttria stabilised zirconia thin films has been investigated in a wide spectral range from 1.0 eV to 7.5 eV and temperatures between 10 K and room temperature. In the near band-edge spectral range, we found a broad distribution of optical transitions within the band gap, the so-called Urbach absorption tail which is typical for amorphous or polycrystalline materials due to the lack of long range order in the crystal structure. The coupling properties of the electronic system to the optical phonon bath and thermal lattice vibrations strongly depend on the ratio of the spectral extent of these disorder states to the main phonon energy, which we correlate with the different crystalline structure of our samples. The films have been grown at room temperature and 650 °C by pulsed laser deposition.

Schmidt-Grund, R.; Lühmann, T.; Böntgen, T.; Franke, H.; Opper, D.; Lorenz, M.; Grundmann, M.

2013-12-01

236

Temperature dependent dielectric function in the near-infrared to vacuum-ultraviolet ultraviolet spectral range of alumina and yttria stabilized zirconia thin films  

Energy Technology Data Exchange (ETDEWEB)

The dielectric function of nano-/polycrystalline alumina and yttria stabilised zirconia thin films has been investigated in a wide spectral range from 1.0?eV to 7.5?eV and temperatures between 10?K and room temperature. In the near band-edge spectral range, we found a broad distribution of optical transitions within the band gap, the so-called Urbach absorption tail which is typical for amorphous or polycrystalline materials due to the lack of long range order in the crystal structure. The coupling properties of the electronic system to the optical phonon bath and thermal lattice vibrations strongly depend on the ratio of the spectral extent of these disorder states to the main phonon energy, which we correlate with the different crystalline structure of our samples. The films have been grown at room temperature and 650?°C by pulsed laser deposition.

Schmidt-Grund, R., E-mail: Schmidt-Grund@physik.uni-leipzig.de; Lühmann, T.; Böntgen, T.; Franke, H.; Lorenz, M.; Grundmann, M. [Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Universität Leipzig, Linnéstr. 5, D-04103 Leipzig (Germany); Opper, D. [PANalytical GmbH, Nürnberger Straße 113, D-34123 Kassel (Germany)

2013-12-14

237

Temperature dependent dielectric function in the near-infrared to vacuum-ultraviolet ultraviolet spectral range of alumina and yttria stabilized zirconia thin films  

International Nuclear Information System (INIS)

The dielectric function of nano-/polycrystalline alumina and yttria stabilised zirconia thin films has been investigated in a wide spectral range from 1.0?eV to 7.5?eV and temperatures between 10?K and room temperature. In the near band-edge spectral range, we found a broad distribution of optical transitions within the band gap, the so-called Urbach absorption tail which is typical for amorphous or polycrystalline materials due to the lack of long range order in the crystal structure. The coupling properties of the electronic system to the optical phonon bath and thermal lattice vibrations strongly depend on the ratio of the spectral extent of these disorder states to the main phonon energy, which we correlate with the different crystalline structure of our samples. The films have been grown at room temperature and 650?°C by pulsed laser deposition

238

Spectral emissivity modeling of steel 201 during the growth of oxidation film over the temperature range from 800 to 1100 K in air  

Science.gov (United States)

This study explores the spectral emissivity modeling of steel 201 during the growth of oxidation film over the temperature range from 800 to 1100 K at 1.5 ?m. The radiance coming from the specimen is received by an InGaAs photodiode detector. The specimen temperature is obtained by averaging the two platinum-rhodium thermocouples, which are tightly welded in the front surface of specimen near the measuring area viewed by the detector. The variation of spectral emissivity with the temperature is studied at a given heating time. The variation of spectral emissivity with the heating time is evaluated at a definite temperature. The strong oscillations of spectral emissivity are observed and discussed in detail, which originate from the interference effect between the radiation stemming from the oxidization film on the specimen surface and the radiation coming from the specimen surface. The measurement uncertainties of spectral emissivity contributed only by the surface oxidization are about 3.2-14.1%. At a given heating time, the variation of spectral emissivity with the temperature abides well by a simple analytic functional form. And at a definite temperature, the variation of spectral emissivity with the heating time can also be well reproduced by fitting except for the periodical oscillations.

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

2014-11-01

239

Anomalies of The Moon's Thermal Emission In The Ir Spectral Range (10,5-12,5 Micron).  

Science.gov (United States)

New satellite measurements of the lunar surface radiation temperature were used to construct the spatial angular function of thermal radiation of the Moon in the infrared (10.5-12.5micron) spectral range. The basic material for investigations is the scanned cosmic spectrozonal images of the lunar surface transmitted by the first Russian geo- stationary artificial meteorological satellite "GOMS". In this paper I describe an ana- lytic model for the lunar thermal field, which is realized as an angular function of the thermal infrared radiation emitted by the lunar surface and analyse thermal anomalies of the lunar surface.A comparison of the regression dependence with radiation tem- peratures measured at some points of the lunar surface shows a systematic departure of the measured values from the average values. These deviations, depending on the surface albedo, characterize the photometric inhomogeneity of the lunar surface layer. On the lunar surface four groups of thermal anomalies are chosen: the thermal anoma- lies at the expense of different heat conduction of the lunar ground, thermal anomalies on the edge of the Moon's limb, "hot spots" - sites of the surface, which area are less than the sanction of the detector, anomalies stipulated by the relief of the surface. On detail study of large-scale photographs some anomalies are identified with small-sized craters, others with separate clusters of stones. The difference in temperature of the surface of the thermal anomalies can exceed 20 deg. The differences of temperature of the lunar surface layer indicate the extremely low heat conduction and high porosity of the material. Major factors of the photometric inhomogeneity are strong irregularities of the relief and the varied heat conduction of the lunar ground. The thermal anomalies for highland regions and for mare regions are shown in figure.

Pugacheva, S. G.; Shevchenko, V. V.

240

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)

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.

Tsai, Rung-Ywan; Ho, Fang C.

1994-11-01

 
 
 
 
241

A Compact Spectral Range and Matching Extreme-Ultraviolet Spectrometer for the Simultaneous Study of 1 × 104-2 × 107 K Solar Plasmas  

Science.gov (United States)

An EUV spectral range of less than 100 Å in first order has been found that includes sufficient spectral lines and critical combinations of lines in first and second order to permit dynamic and diagnostic investigations of the solar atmosphere with a relatively simple spectrometer. An optical design of such a spectrometer, based on the performance of the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) spacecraft, and sample stigmatic solar spectra for the range 1334-1428 Å from SUMER are presented to illustrate the utility of this range. Lines of almost all abundant solar elements except H and He are present within this wavelength band in first or second order. The lines cover the large temperature range from 1 × 104 K (chromosphere) to 2 × 107 K (flares). The spectrometer's resolution is sufficiently high to permit measuring line profiles and wavelength shifts which allows plasma dynamical studies of individual solar structures from the chromosphere up into the corona. In addition, electron density diagnostics are available within the spectral range that cover the temperature range from 8 × 104 to 1 × 106 K and an electron density range from 108 to 1013 cm-3.

Feldman, U.; Brown, C. M.; Laming, J. M.; Seely, J. F.; Doschek, G. A.

1998-08-01

242

Visibles Revisited  

Science.gov (United States)

Within the set of points in the plane with integer coordinates, one point is said to be visible from another if no other point in the set lies between them. This study of visibility draws in topics from a wide variety of mathematical areas, including geometry, number theory, probability, and combinatorics.

Bridger, Mark; Zelevinsky, Andrei

2005-01-01

243

Design of a sun tracker for the automatic measurement of spectral irradiance and construction of an irradiance database in the 330-1100 nm range  

Energy Technology Data Exchange (ETDEWEB)

An automatic global and direct solar spectral irradiance system has been designed based on two LICOR spectro radiometers equipped with fibre optics and remote cosine sensors. To measure direct irradiance a sun tracker based on step motors has been developed. The whole system is autonomous and works continuously. From the measurements provided by this system a spectral irradiance database in the 330-1100 nm range has been created. This database contains normal direct and global horizontal irradiances as well as diffuse irradiance on a horizontal plane, together with total atmospheric optical thickness and aerosol optical depth. (author)

Canada, J.; Maj, A. [Departamento de Termodinamica Aplicada, Universidad Politecnica de Valencia, Camino de Vera, s/n. 46022 Valencia (Spain); Utrillas, M.P.; Martinez-Lozano, J.A.; Pedros, R.; Gomez-Amo, J.L. [Departamento de Fisica de la Tierra y Termodinamica, Facultat de Fisica, Universitat de Valencia, 46100 Burjassot (Valencia) (Spain)

2007-10-15

244

The visible and infrared luminescence of activated silver bromide crystals  

Science.gov (United States)

The luminescence of silver bromide crystals doped with metal ions (Ni 2+, Co 2+, Nd 3+, Pr 3+, and Er 3+) was investigated in the visible and near infrared spectral ranges. The emission, excitation, and absorption spectra, as well as the kinetic parameters, were measured over a broad temperature range. The Judd-Ofelt analysis was applied to the rare-earth doped crystals, and transition rates, branching ratios, and quantum efficiencies were calculated. Good agreement between theory and experiment was obtained.

Bunimovich, D.; Nagli, L.; Katzir, A.

1997-07-01

245

Variable optical attenuator for use in the visible spectrum.  

Science.gov (United States)

A method for attenuating a laser beam based on the excitation of a surface plasmon is described. This attenuator is continuously variable, has a dynamic range of 10(2), has a spectral range covering the visible, does not steer the beam or distort its profile, and can handle powers of at least 1-W cw. Some preliminary results obtained on a crude prototype are presented; final device design and predicted performance are discussed. PMID:20490148

Staromlynska, J; Clay, R A; Dexter, K F

1987-09-15

246

Theoretical modeling of an U-shaped SPR fiber sensor in 1550-nm spectral range for sensing applications  

Science.gov (United States)

Currently, the surface plasmon resonance (SPR) based sensors are mainly focused in visible frequencies, being a barrier for a better integration with the typical fiber optical communication transmission bands. Here, it is presented a theoretical analysis of a SPR based fiber optic sensor with a uniform gold coating on a U-shaped probe. The sensor does not require any fiber etching treatment which eases and improves the control of the overall process. The response of the device to refractive index variations was investigated and a resolution of 10-8 is foreseen for refractive indices around 1.413, becoming the proposed sensor a useful tool for biological and chemical applications.

Duarte, Daniel P.; Alberto, Nélia J.; Bilro, Lúcia; Nogueira, Rogério N.

2014-08-01

247

Relative spectral response measurement of spectrometers using undulator radiation  

Science.gov (United States)

Undulator radiation with known spectral characteristics is recognized as an excellent light source that can be used to measure the spectral response of a variety of spectral measurement devices in a wide range from infrared to x-ray. This technique has been developed at Duke Free-Electron Laser (FEL) Laboratory to successfully measure the spectral response of several spectrometers in the near-infrared, visible, and ultraviolet regions. In this paper, we present both simulation and experimental results of the spectral response measurement, with a focus on high-accuracy spectral response reconstruction. Using simulation studies, we have tested and confirmed the validity of the spectral response measurement method while taking into account major sources of errors. Especially, it shows that the spectral response reconstruction technique developed in this work is rather robust against the spectral broadening of undulator radiation. The usefulness of this spectral response measurement method is also confirmed with the experimental study on a spectrometer in the visible region. Overall, we have achieved good results with the measured spectral response, with an RMS uncertainty of about 2.7% in the range from 414 to 591 nm. Using multiple measurements, the reproducibility of this method has also been tested with a relative difference of about 2.3% (RMS in the range from 415 to 590 nm). For high-accuracy measurements of a broad radiation spectrum, the knowledge of the spectral response of the spectrometer is critical. In this paper, we will show that the details of the measured undulator radiation spectra can be properly restored by correcting the raw spectrum using the measured spectral response. The method of spectral response measurement using undulator radiation is also useful to calibrate spectral devices in extreme spectral ranges such as VUV and x-ray.

Huang, S.; Li, J. Y.; Jia, B.; Wu, Y. K.

2014-03-01

248

X-ray crystal spectrometer for opacity measurements in the 8-18 Å spectral range at the LULI laser facilitya)  

Science.gov (United States)

An x-ray crystal spectrometer was built in order to measure opacities in the 8-18 Å spectral range with an average spectral resolution of ?? /???˜400. It has been successfully used at the LULI-2000 laser facility (See C. Sauteret, rapport LULI 2001, 88 (2002) at École Polytechnique (France) to measure in the same experimental conditions the 2p-3d transitions of several elements with the neighboring atomic number Z: Fe, Ni, Cu, and Ge [G. Loisel et al., High Energy Density Phys. 5, 173 (2009)]. Hence, a spectrometer with a wide spectral range is needed. This spectrometer features two lines of sight. In this example, one line of sight looks through the sample and the other one is looking directly at the backlighter emission. Both are outfitted with a spherical condensing mirror. A TlAP crystal is used for spectral dispersion. Detection is made with an image plate Fuji BAS TR2025, which is sensitive to x rays. We present some experimental results showing the performances of this spectrometer.

Reverdin, C.; Thais, F.; Loisel, G.; Bougeard, M.

2010-10-01

249

X-ray crystal spectrometer for opacity measurements in the 8-18 A spectral range at the LULI laser facility  

International Nuclear Information System (INIS)

An x-ray crystal spectrometer was built in order to measure opacities in the 8-18 A spectral range with an average spectral resolution of ?400. It has been successfully used at the LULI-2000 laser facility (See C. Sauteret, rapport LULI 2001, 88 (2002) at Ecole Polytechnique (France) to measure in the same experimental conditions the 2p-3d transitions of several elements with the neighboring atomic number Z: Fe, Ni, Cu, and Ge [G. Loisel et al., High Energy Density Phys. 5, 173 (2009)]. Hence, a spectrometer with a wide spectral range is needed. This spectrometer features two lines of sight. In this example, one line of sight looks through the sample and the other one is looking directly at the backlighter emission. Both are outfitted with a spherical condensing mirror. A TlAP crystal is used for spectral dispersion. Detection is made with an image plate Fuji BAS TR2025, which is sensitive to x rays. We present some experimental results showing the performances of this spectrometer.

250

Final report on the key comparison CCPR-K2.c-2003: Spectral responsivity in the range of 200 nm to 400 nm  

Science.gov (United States)

The CCPR K2.c key comparison of spectral power responsivity of detectors in the ultraviolet spectral range from 200 nm to 400 nm was carried out in the framework of the CIPM Mutual Recognition Arrangement by 14 participating national metrology institutes. The key comparison was piloted by the Physikalisch-Technische Bundesanstalt (PTB). The comparison was carried out through the calibration of sets of transfer detectors. Three types of transfer detectors based on two types of photodiodes have been used to handle probable changes of the spectral responsivity of the detectors in the ultraviolet spectral range. The results of the key comparison in the wavelength range from 200 nm to 240 nm are based on single-element windowless PtSi/n-Si Schottky photodiodes while in the range from 250 nm to 400 nm the results are based on single-element photodiode detectors and three-element reflection trap detectors, both made up of windowless Si pn junction photodiodes. The comparison was organized in a star pattern and conducted in three groups of participants. The report describes the measurements made by the pilot laboratory, summarizes the reports submitted by the participants and describes the data analysis carried out to determine the key comparison reference values and degrees of equivalence. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Werner, Lutz

2014-01-01

251

Temperature dependence of the dielectric function in the spectral range (0.5-8.5) eV of an In2O3 thin film  

Science.gov (United States)

We present the dielectric function of a bcc-In2O3 thin film in the wide spectral range from near-infrared to vacuum-ultraviolet and for temperatures 10 K-300 K, determined by spectroscopic ellipsometry. From the temperature dependence of electronic transition energies, we derive electron-phonon coupling properties and found hints that the direct parabolic band-band transitions involve In-d states. Further we discuss possible excitonic contributions to the dielectric function.

Schmidt-Grund, R.; Krauß, H.; Kranert, C.; Bonholzer, M.; Grundmann, M.

2014-09-01

252

Spectral characteristics of visible luminescence in Gd2SiO5-Lu2SiO5 (LGSO) solid solution crystals co-doped with Ce3+ and Dy3+  

Science.gov (United States)

Two single crystals of LGSO containing 1% Dy3+ and differing in Ce3+ concentration were grown by the Czochralski method. XRD examination revealed that a crystal with a nominal Ce3+ concentration of 3% has the C2/c structure inherent to Lu2SiO5 (LSO) whereas a crystal with a nominal Ce3+ concentration of 1% has the P21/c structure inherent to Gd2SiO5 (GSO). In both crystal structure types the excitation of Ce3+ ions is followed by an energy transfer to Dy3+ ions and resulting visible emission consists of a broad-band Ce3+ luminescence and of much more narrow bands of Dy3+ luminescence. Excitation spectra imply that the efficiency of Dy3+ excitation via Ce3+ - Dy3+ energy transfer is markedly higher than upon direct optical pumping into Dy3+ excited levels. It was observed that visible emission in the two systems differs in spectral characteristics, hence in the colour of the emitted light. Examination of optical spectra recorded with a polarized light revealed important anisotropy of transition intensities of Ce3+ ions in LGSO host with the P21/c structure.

Strz?p, Adam; Ryba-Romanowski, Witold; Berkowski, Marek

2014-11-01

253

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: 1. Measurement procedures and results  

Science.gov (United States)

The infrared (IR) aerosol optical thickness (AOT) spectra of Saharan dust measured during the Portable Infrared Aerosol Transmission Experiment (PIRATE) are reported. Saharan dust optical thickness (extinction) spectra from 8 to 13 ?m were obtained using column-integrated solar transmission measurements in Puerto Rico in July 2005 and Senegal in January and March 2006 (during a dust plume) using a Fourier transform infrared (FTIR) spectrometer. The FTIR measured the solar spectral irradiance in the IR in the presence of Saharan dust, and the AOT was determined by comparing the measured spectra to modeled downwelling spectra without dust for the same atmospheric temperature profile, solar zenith angle, water vapor, and ozone concentrations. The modeled dust-free spectra are generated using the Santa Barbara Disort Atmospheric Radiative Transfer (SBDART) program. The measured dust AOT is compared with modeled AOT spectra obtained using Mie theory with dust indices of refraction from Volz and Fouquart with assumed lognormal size distributions. When the visible AOT values from nearby Aerosol Robotic Network (AERONET) sensors are compared to the IR AOT values, results from various dust loadings show that the IR dust AOT at 9.5 ?m is typically only one third that of the visible (670 nm) dust AOT, but there is some evidence that this ratio could increase for larger dust size distributions. The surface IR dust forcing is determined to be about -0.4 W/m2 by summing the dusty and clear irradiance differences.

Thomas, M.; Gautier, C.; Ricchiazzi, P.

2009-06-01

254

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)

255

Dual-channel spectral-domain optical-coherence tomography system based on 3 × 3 fiber coupler for extended imaging range.  

Science.gov (United States)

We have demonstrated a dual-channel multiplexing spectral-domain optical-coherence tomography (SD-OCT) system based on a 3×3 fiber coupler for extended imaging range of whole human eye depth, with a single light source and spectrometer. OCT images of anterior segments of a human eye were sequentially performed and constructed to demonstrate an extended depth range as large as 15 mm in air. A good quality OCT image of the whole anterior segment of an eye was present. Furthermore, whole eye segmental imaging was performed and ocular distances were calculated to show the validation of the system for whole eye morphological measurement. PMID:25321108

Dai, Cuixia; Fan, Shanhui; Chai, Xinyu; Li, Yan; Ren, Qiushi; Xi, Peng; Zhou, Chuanqing

2014-08-20

256

A narrow-linewidth external cavity quantum dot laser for high-resolution spectroscopy in the near-infrared and yellow spectral ranges  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We demonstrate a diode laser system which is suitable for high-resolution spectroscopy in the 1200 nm and yellow spectral ranges. It is based on a two-facet quantum dot chip in a Littrow-type external cavity configuration. The laser is tunable in the range 1125 -1280 nm, with an output power of more than 200 mW and exhibits a free-running linewidth of 200 kHz. Amplitude and frequency noise were characterized, including the dependence of frequency noise on the cavity length. ...

Nevsky, A. Yu; Bressel, U.; Eisele, Ch; Okhapkin, M.; Schiller, S.; Gubenko, A.; Livshits, D.; Mikhrin, S.; Krestnikov, I.; Kovsh, A.

2008-01-01

257

Super Dual Auroral Radar Network observations of fluctuations in the spectral distribution of near range meteor echoes in the upper mesosphere and lower thermosphere  

Directory of Open Access Journals (Sweden)

Full Text Available The Doppler shifts of meteor echoes measured by the SuperDARN HF radar network have been used in several studies to observe neutral winds in the upper mesosphere and lower thermosphere region. In the absence of accurate height information for individual meteors, it has been necessary to assume a statistical mean meteor layer where the variations in altitude were not correlated to changes in the horizontal winds. Observations of spectral width distribution variations made by the radars allow an independent determination of the systematic error in the height. We have investigated the dependence of this distribution on a number of factors including the radar geometry, diurnal and seasonal cycles, variations in solar UV irradiance and geomagnetic activity. Changes in the altitude of the mean meteor layer observed at different radar ranges provide us with some insight into the structure of the upper mesosphere and the lower thermosphere within which the meteors are being ablated. An examination of the spectral widths, as measured by the CUT-LASS Finland radar, in the days preceding and following a Storm Sudden Commencement in April 1997, illustrates how the spectral properties of the observed region can be affected. The variations in the widths were consistent with model calculations of the changes to the temperature profile over this interval. Further refinements in the determination of the spectral width are outlined for future experiments.

Key words. Meterology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; instruments and techniques

N. F. Arnold

258

Efficient ion blocking in gaseous detectors and its application to gas-avalanche photomultipliers sensitive in the visible-light range  

CERN Document Server

A novel concept for ion blocking in gas-avalanche detectors was developed, comprising cascaded micro-hole electron multipliers with patterned electrodes for ion defocusing. This leads to ion blocking at the 10^{-4} level, in DC mode, in operation conditions adequate for TPCs and for gaseous photomultipliers. The concept was validated in a cascaded visible-sensitive gas avalanche photomultiplier operating at atmospheric pressure of Ar/CH_{4} (95/5) with a bi-alkali photocathode. While in previous works high gain, in excess of 10^{5}, was reached only in a pulse-gated cascaded-GEM gaseous photomultiplier, the present device yielded, for the first time, similar gain in DC mode. We describe shortly the physical processes involved in the charge transport within gaseous photomultipliers and the ion blocking method. We present results of ion backflow fraction and of electron multiplication in cascaded patterned-electrode gaseous photomultiplier with K-Cs-Sb, Na-K-Sb and Cs-Sb visible-sensitive photocathodes, operate...

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

2008-01-01

259

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)

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.

M. Rajeswara Rao

2005-08-01

260

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.  

Science.gov (United States)

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 E-red). 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 E-violet 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. PMID:16705821

Cohly, Hari H P; Panja, Asit; Reno, William L; Obenhuber, Don; Koelle, Margot S; Das, Suman K; Angel, Michael F; Rao, M Rajeswara

2005-08-01

 
 
 
 
261

Spectral stratigraphy  

Science.gov (United States)

Stratigraphic and structural studies of the Wind River and Bighorn basins, Wyoming, and the Guerrero-Morelos basin, Mexico, have resulted in development of ''spectral stratigraphy.'' This approach to stratigraphic analysis 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. This paper reviews selected published examples that illustrate this new stratigraphic procedure. Visible to thermal infrared laboratory, spectral measurements of sedimentary rocks are the physical basis for spectral stratigraphy. Results show that laboratory, field, and remote spectroscopy can augment conventional laboratory and field methods for petrologic analysis, stratigraphic correlation, interpretation of depositional environments, and construction of facies models. Landsat thematic mapper data are used to map strata and construct stratigraphic columns and structural cross sections at 1:24,000 scale or less. Experimental multispectral thermal infrared aircraft data facilitate lithofacies/biofacies analyses. Visible short-wavelength infrared imaging spectrometer data allow remote determination of the stratigraphic distribution of iron oxides, quartz, calcite, dolomite, gypsum, specific clay species, and other minerals diagnostic of environments of deposition. Development of a desk-top, computer-based, geologic analysis system that provides for automated application of these approaches to coregistered digital image and topographic data portends major expansion in the use of spectral stratigraphy for purely scientific (lithospheric research) or practical (resource exploration) objectives.

Lang, Harold R.

1991-09-01

262

Third-harmonic generation in silicon and photonic crystals of macroporous silicon in the spectral intermediate-IR range; Erzeugung der Dritten Harmonischen in Silizium und Photonischen Kristallen aus makroporoesem Silizium im spektralen mittleren IR-Bereich  

Energy Technology Data Exchange (ETDEWEB)

Nonlinear optical spectroscopy is a powerful method to study surface or bulk properties of condensed matter. In centrosymmetric materials like silicon even order nonlinear optical processes are forbidden. Besides self-focussing or self phase modulation third-harmonic-generation (THG) is the simplest process that can be studied. This work demonstrates that THG is a adapted non-contact and non-invasive optical method to get information about bulk structures of silicon and Photonic crystals (PC), consisting of silicon. Until now most studies are done in the visible spectral range being limited by the linear absorption losses. So the extension of THG to the IR spectral range is extremely useful. This will allow the investigation of Photonic Crystals, where frequencies near a photonic bandgap are of special interest. 2D- photonic structures under investigation were fabricated via photoelectrochemical etching of the Si (100) wafer (thickness 500 {mu}m) receiving square and hexagonal arranged pores. The typical periodicity of the structures used is 2 {mu}m and the length of the pores reached to 400 {mu}m. Because of stability the photonic structures were superimposed on silicon substrate. The experimental set-up used for the THG experiments generates tuneable picosecond IR pulses (tuning range 1500-4000 cm{sup -1}). The IR-pulse hit the sample either perpendicular to the sample surface or under an angle {theta}. The sample can be rotated (f) around the surface normal. The generated third harmonic is analysed by a polarizer, spectrally filtered by a polychromator and registered by a CCD camera. The setup can be used either in transmission or in reflection mode. Optical transmission and reflection spectra of the Si bulk correspond well with the theoretical description, a 4-fold and a 8-fold dependencies of the azimuth angle resulting in the structure of the x{sup (3)}-tensor of (100)-Si. The situation changes dramatically if the PC with hexagonal structure is investigated. In reflection mode a six fold symmetry is observed. This can only be explained by the symmetry of the Photonic Crystal. Changing the transmission mode the result depends on the mount of the PC - fundamental entering from the structure side or fundamental entering from the bulk side. Common to both results are there six maxima. To explain the difference between the transmission and reflection results one has to recognise, that the effective interaction length is limited: so in the reflection geometry of generated TH is from the structured region, whereas in the transmission cases a combination of the structure and the bulk has to be taken into account. This work gives a first theoretical description of this effects. (orig.)

Mitzschke, Kerstin

2007-11-01

263

Effective temperatures and spectral energy distribution for A and F stars in the near infrared range. Comparison with theoretical models  

International Nuclear Information System (INIS)

The comparison between observal energy distribution for A and F stars with the theoretical model atmospheres of Kurucz at the range 6000-10800 A is presented. A and F stars of IV and V luminosity classes have infrared excesses ? 5-6% in the region 8000-10800 A (the mean value of excess of the main spectrophotometric standard range

264

Human Contrast Threshold and Astronomical Visibility  

CERN Document Server

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...

Crumey, Andrew

2014-01-01

265

Gas-phase absorption cross sections of 24 monocyclic aromatic hydrocarbons in the UV and IR spectral ranges  

Science.gov (United States)

Absorption cross sections of 24 volatile and non-volatile derivatives of benzene in the ultraviolet (UV) and the infrared (IR) regions of the electromagnetic spectrum have been determined using a 1080 l quartz cell. For the UV a 0.5 m Czerny-Turner spectrometer coupled with a photodiode array detector (spectral resolution 0.15 nm) was used. IR spectra were recorded with an FT-IR spectrometer (Bruker IFS-88, spectral resolution 1 cm -1). Absolute absorption cross sections and the instrument function are given for the UV, while for the IR, absorption cross sections and integrated band intensities are reported. The study focused primarily on the atmospherically relevant methylated benzenes (benzene, toluene, o-xylene, m-xylene, p-xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethylbenzene, styrene) and their ring retaining oxidation products (benzaldehyde, o-tolualdehyde, m-tolualdehyde, p-tolualdehyde, phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4,6-trimethylphenol and ( E,Z)- and ( E,E)-2,4-hexadienedial). The UV absorption cross sections reported here can be used for the evaluation of DOAS spectra (Differential Optical Absorption Spectroscopy) for measurements of the above compounds in the atmosphere and in reaction chambers, while the IR absorption cross sections will primarily be useful in laboratory studies on atmospheric chemistry, where FT-IR spectrometry is an important tool.

Etzkorn, Thomas; Klotz, Björn; Sørensen, Søren; Patroescu, Iulia V.; Barnes, Ian; Becker, Karl H.; Platt, Ulrich

266

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.)

267

Experimental Verification of n=0 Structures for Visible Light  

Science.gov (United States)

We fabricate and characterize a metal-dielectric nanostructure with an effective refractive index n=0 in the visible spectral range. Light is excited in the material at deep subwavelength resolution by a 30-keV electron beam. From the measured spatially and angle-resolved emission patterns, a vanishing phase advance, corresponding to an effective ?=0 and n=0, is directly observed at the cutoff frequency. The wavelength at which this condition is observed can be tuned over the entire visible or near-infrared spectral range by varying the waveguide width. This n=0 plasmonic nanostructure may serve as a new building block in nanoscale optical integrated circuits and to control spontaneous emission as experimentally demonstrated by the strongly enhanced radiative optical density of states over the entire n=0 structure.

Vesseur, Ernst Jan R.; Coenen, Toon; Caglayan, Humeyra; Engheta, Nader; Polman, Albert

2013-01-01

268

Visible-Infrared Hyperspectral Image Projector  

Science.gov (United States)

The VisIR HIP generates spatially-spectrally complex scenes. The generated scenes simulate real-world targets viewed by various remote sensing instruments. The VisIR HIP consists of two subsystems: a spectral engine and a spatial engine. The spectral engine generates spectrally complex uniform illumination that spans the wavelength range between 380 nm and 1,600 nm. The spatial engine generates two-dimensional gray-scale scenes. When combined, the two engines are capable of producing two-dimensional scenes with a unique spectrum at each pixel. The VisIR HIP can be used to calibrate any spectrally sensitive remote-sensing instrument. Tests were conducted on the Wide-field Imaging Interferometer Testbed at NASA s Goddard Space Flight Center. The device is a variation of the calibrated hyperspectral image projector developed by the National Institute of Standards and Technology in Gaithersburg, MD. It uses Gooch & Housego Visible and Infrared OL490 Agile Light Sources to generate arbitrary spectra. The two light sources are coupled to a digital light processing (DLP(TradeMark)) digital mirror device (DMD) that serves as the spatial engine. Scenes are displayed on the DMD synchronously with desired spectrum. Scene/spectrum combinations are displayed in rapid succession, over time intervals that are short compared to the integration time of the system under test.

Bolcar, Matthew

2013-01-01

269

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.

270

Impact of cavity symmetry on mode suppression and increase of free spectral range in solid-state dye microlaser  

Science.gov (United States)

We describe modeling the solid-state dye laser with the microcavity size comparable to light wavelength. Certain symmetry in the allocation of gain material leads to depletion of odd longitudinal modes that, in turn, increases the tunability range of the microlaser. We provide simple physical explanation for the modeling results.

Popov, Sergei; Ricciardi, Sebastien; Friberg, Ari T.; Sergeyev, Sergey

2007-11-01

271

Study of wave chaos in a randomly-inhomogeneous oceanic acoustic waveguide: spectral analysis of the finite-range evolution operator  

CERN Document Server

The proplem of sound propagation in an oceanic waveguide is considered. Scattering on random inhomogeneity of the waveguide leads to wave chaos. Chaos reveals itself in spectral properties of the finite-range evolution operator (FREO). FREO describes transformation of a wavefield in course of propagation along a finite segment of a waveguide. We study transition to chaos by tracking variations in spectral statistics with increasing length of the segment. Analysis of the FREO is accompanied with ray calculations using the one-step Poincar\\'e map which is the classical counterpart of the FREO. Underwater sound channel in the Sea of Japan is taken for an example. Several methods of spectral analysis are utilized. In particular, we approximate level spacing statistics by means of the Berry-Robnik and Brody distributions, explore the spectrum using the procedure elaborated by A. Relano with coworkers (Relano et al, Phys. Rev. Lett., 2002; Relano, Phys. Rev. Lett., 2008), and analyze modal expansions of the eigenfu...

Makarov, D V; Uleysky, M Yu; Petrov, P S

2012-01-01

272

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

273

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

Energy Technology Data Exchange (ETDEWEB)

We report the parameters necessary to construct the dielectric functions of Cd{sub 1-x}Mg{sub x}Te 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 E{sub 2} + ?{sub 2}, E{sub 2}(?), E{sub 2}(?), and E'{sub 1} transitions.

Kim, Tae Jung; Ghong, Tae Ho; Yoon, Jae Jin; Hwang, Soon Yong; Barange, Nilesh; Kim, Young Dong [Kyung Hee University, Seoul (Korea, Republic of); Chang, Yia Chung [Research Center for Applied Sciences, Academia Sinica, Taipei (China)

2012-04-15

274

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.

275

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

276

Visible range colossal magnetorefractive effect in (La1 - y Pr y )2/3Ca1/3MnO3 films  

Science.gov (United States)

We report a colossal magnetorefractive effect (MRE) in epitaxial thin films of a classical colossal magnetoresistance (CMR) manganite, (La1 - y Pr y )2/3Ca1/3MnO3 (y = 0.375 and 0.7). Close to the ferromagnetic (FM) phase transition a moderate applied magnetic field, H ˜ 10 kOe, results in a reduction of the optical reflectance by ˜18% for the photon energy E ˜ 2.7 eV. The MRE spectral behavior with three pronounced maxima at E = 1.6, 2.7 and 4.0 eV points out an inter-site nature of the involved optical transitions. The results are discussed within a phase separation scenario with coexisting FM metallic nanodomains antiferromagnetically coupled by correlated polarons. The probability of MRE optical transitions is maximal for antiparallel alignment of Mn3+/Mn4+-spins realized for the coercive field, H c ˜ 200-800 Oe, and is suppressed by stronger fields, which favor FM metallic behavior. As a result, both the optical reflectivity and the electrical resistance decrease, yielding a close similarity between the CMR and MRE behavior.

Jungbauer, M.; Hühn, S.; Krisponeit, J.-O.; Moshnyaga, V.

2014-06-01

277

Atomic states of lithium by the beam-foil technique in the spectral range 400-1,900 A  

International Nuclear Information System (INIS)

6Li+-ions accelerated electrostatically to energies of 200-390 keV are electronically excited by the beam-foil technique. The emitted light is analyzed with a Seya-Namioka VUV monochromator in the wavelength range 400-1,900 A. All Li II and Li III lines known from theory - in one case emitted by a n = 9 level - are detected, several of them for the first time. Lifetimes of 20 Li II levels are determined after correction for cascades. The accuracy of the experimental values for several lifetimes is better than of theoretical predictions. (orig.)

278

Change of the spectral sensitivity range of thin-film AlGaAs/GaAs -photoreceivers under influence of ultrasonic waves  

International Nuclear Information System (INIS)

Full text: The task of controlled variation of the physical properties of semiconductor materials under the action of external factors is an important problem in the physics of semiconductors. As is well known, one such factor is ultrasonic radiation: propagating in a semiconductor crystal, acoustic (ultrasonic) waves change its properties, in particular, the optical characteristics. In the context of solving the above task, it is expedient to continue investigations of the effect of ultrasonic waves on the characteristics of semiconductor devices. This report presents the results of experimental investigations of the influence of ultrasonic waves on the spectral characteristics of photoreceivers based on AlGaAs/GaAs- heterostructures. The study showed that an exposure to ultrasonic radiation leads to a change, depending on the ultrasonic treatment (UST) parameters, in the spectral characteristics of gallium arsenide crystals, the base materials of modern semiconductor photoelectronics. Some results showed evidence of the positive character of changes in the characteristics of A3B5-based photoreceivers under the action of ultrasonic waves. The effect of ultrasonic waves on the spectral sensitivity of photoreceivers based on AlGaAs/GaAs- heterostructures has been studied. Ultrasonic treatment of a zinc-doped graded-gap AlxGa1-x As- film leads to the formation of a surface layer sensitive to electromagnetic radiation in the wavelength range < 0,55m. It is established that this layer is formed as a result of the acoustostimulated inward diffusion of zinc from the surface to the bulk of the graded-gap layer. The observed expansion of the short-wavelength sensitivity range and an increase in the efficiency of nonequilibrium charge carrier collection in AlGaAs/GaAs- photoreceivers are due to improvement of the crystal defect structure and the dopant redistribution under the action of ultrasound. (authors)

279

Sensitivity gains, linearity, and spectral reproducibility in nonuniformly sampled multidimensional MAS NMR spectra of high dynamic range.  

Science.gov (United States)

Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear (13)C-(13)C correlation spectra. We demonstrate on model compounds and on 1-73-(U-(13)C,(15)N)/74-108-(U-(15)N) E. coli thioredoxin reassembly, that with appropriately constructed 50% NUS schedules inherent sensitivity gains of 1.7-2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear (13)C-(13)C MAS correlation experiments that yield high-quality artifact-free datasets. PMID:24752819

Suiter, Christopher L; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David; Hoch, Jeffrey C; Rovnyak, David; Polenova, Tatyana

2014-06-01

280

Spectrophotometric determination of absorption in the DUV/VUV spectral range for MgF2 and LaF3 thin films  

Science.gov (United States)

The intrinsic absorption of fluoride coating materials tends to higher values in the DUV/VUV spectral range. In respect to applications of this material class for DUV/VUV multilayer systems, like high reflecting mirrors and anti- reflective coatings, the control of absorption is essential for further improvement of the coating quality. However, the reliable determination of absorption losses by photometric techniques has to overcome various obstacles caused by light absorption in air, scattering effects of the coating, and absorption related to contamination of the employed fluoride material. In this contribution spectrophotometric measurements for the characterization of optical data of MgF2 and LaF3 single layers and multi layer systems are presented. An advanced VUV/DUV-spectrophotometer, which has been developed at the Laser Zentrum Hannover for the optimization of thin film production processes, is described. The subsequent optical data evaluation for fluoride single layer coatings is reported and the optical data, n and k, of MgF2 and LaF3 for the spectral range from 130 to 660 nm are presented. Transmittance and reflectance measurements of multilayer coating systems are compared to theoretical calculations for these systems on the basis of the evaluated optical data of the single layers. Observed deviations are discussed under respect of contaminations of the fluoride layer systems.

Guenster, Stefan; Ristau, Detlev; Bosch, Salvador

2000-11-01

 
 
 
 
281

A simple analysis method for measuring in real-time power spectral densities and coherence functions in a large frequency range  

International Nuclear Information System (INIS)

This paper describes a real-time method which allows the measurement of auto and cross power spectral densities in a large frequency range with almost constant relative frequency resolution. Based on a normal digital frequency analysis the resolution at low frequencies can be increased to any extend without additional electronic equipment. The long time signals needed for the low frequencies are won from the high frequency data by a digital low pass filter. Due to this decimation of the time series only moderate storage region is needed allowing the use of a small digital computer for on-line application. The method is suitable to monitor the spectra in a wide frequency range without time delay. (orig.)

282

Spectral studies of SiCl4 + N2O + Ar and SiH4 + Ar mixtures in a shock tube in 160-550 nm range  

Science.gov (United States)

Gases containing SiO, SiO2, SiH, and Si2 were produced in the reflected-shock region of a shock tube by heating SiCl4 + N2O + Ar and SiH4 + Ar mixtures with shock waves. Spectral absorption characteristics were measured in the 160-550 nm wavelength range and in the 2800-3600 K temperature range and compared to calculated values. The sums of the squares of electronic transition moments at equilibrium separation were derived. It was found that absorption by SiO2 and other known bands of SiO, SiH, and Si2 were too weak to be measured. The cross section of absorption by a continuum, believed due to SiH, varied from 2.5 x 10 to the -17th sq cm at 280 nm to 1.6 x 10 to the -18th sq cm at 440 nm.

Park, C.; Fujiwara, T.

1978-01-01

283

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

Science.gov (United States)

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.

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

2014-07-01

284

A narrow-linewidth external cavity quantum dot laser for high-resolution spectroscopy in the near-infrared and yellow spectral ranges  

CERN Document Server

We demonstrate a diode laser system which is suitable for high-resolution spectroscopy in the 1200 nm and yellow spectral ranges. It is based on a two-facet quantum dot chip in a Littrow-type external cavity configuration. The laser is tunable in the range 1125 -1280 nm, with an output power of more than 200 mW and exhibits a free-running linewidth of 200 kHz. Amplitude and frequency noise were characterized, including the dependence of frequency noise on the cavity length. Frequency stabilization to a high-finesse reference cavity is demonstrated reducing the linewidth to about 20 - 30 kHz. Yellow light (> 3 mW) at 578 nm was generated by frequency doubling in an enhancement cavity containing a PPLN crystal. The source has potential application for precision spectroscopy of ultra-cold Yb atoms and molecular hydrogen ions.

Nevsky, A Yu; Eisele, Ch; Okhapkin, M; Schiller, S; Gubenko, A; Livshits, D; Mikhrin, S; Krestnikov, I; Kovsh, A

2008-01-01

285

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

Science.gov (United States)

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. PMID:25003752

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

2014-07-01

286

Variation of spectral properties of dielectric ionic crystal in the terahertz range due to the polariton absorption.  

Science.gov (United States)

The dispersion equations for polariton waves in dielectric ionic crystal with the absorption are obtained. The self-consistent solutions of the system of Maxwell electromagnetic field equations and the equations of motion of ions have been used. The elastic and absorption properties of the crystal are taken into account in the ion equations of motion. It is shown that the separated equations of motion for positive and negative ions allow obtaining all branches of phonon and polariton spectrum by the example of the ionic crystal of cubic symmetry at the terahertz range. It has been shown that the variation of absorption in the crystal leads to changing of the character of spectrum branch and the polariton velocities. PMID:24922221

Dzedolik, Igor V; Pereskokov, Vladislav

2014-05-20

287

Tailoring the shape of GaN/AlxGa1-xN nanostructures to extend their luminescence in the visible range  

International Nuclear Information System (INIS)

We show that the shape of GaN nanostructures grown by molecular beam epitaxy on AlxGa1-xN (0001) surfaces, for x?0.4, can be controlled via the ammonia pressure. The nanostructures are obtained from a two dimensional to three dimensional transition of a GaN layer occurring upon a growth interruption. Atomic force microscopy measurements show that depending on the ammonia pressure during the growth interruption, dot or dash-shaped nanostructures can be obtained. Low temperature photoluminescence measurements reveal a large redshift in the emission energy of the quantum dashes, as compared to the quantum dots. By simply adjusting the GaN deposited thickness, it is shown that quantum dashes enable to strongly extend the emission range of GaN/Al0.5Ga0.5N nanostructures from the violet-blue (?400-470 nm) to the green-orange range (?500-600 nm)

288

Radiation damage resistance of AlGaN detectors for applications in the extreme-ultraviolet spectral range  

International Nuclear Information System (INIS)

We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky-photodiode-based detectors. AlGaN layers were grown using metal-organic chemical vapor deposition (MOCVD) on Si(111) wafers. The diodes were characterized at a wavelength of 13.5 nm using a table-top extreme-ultraviolet (EUV) radiation source, consisting of a laser-produced xenon plasma and a Schwarzschild objective. The responsivity of the diodes was tested between EUV energies ranging from 320 nJ down to several picojoules. For low fluences, a linear responsivity of 7.14 mAs/J could be determined. Saturation starts at approximately 1 nJ, merging into a linear response of 0.113 mAs/J, which could be attributed to the photoeffect on the Au electrodes on top of the diode. Furthermore, degradation tests were performed up to an absolute dose of 3.3x1019 photons/cm2. AlGaN photodiodes were compared to commercially available silicon-based photodetectors. For AlGaN diodes, responsivity does not change even for the highest EUV dose, whereas the response of the Si diode decreases linearly to ?93% after 2x1019 photons/cm2.

289

Radiation damage resistance of AlGaN detectors for applications in the extreme-ultraviolet spectral range.  

Science.gov (United States)

We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky-photodiode-based detectors. AlGaN layers were grown using metal-organic chemical vapor deposition (MOCVD) on Si(111) wafers. The diodes were characterized at a wavelength of 13.5 nm using a table-top extreme-ultraviolet (EUV) radiation source, consisting of a laser-produced xenon plasma and a Schwarzschild objective. The responsivity of the diodes was tested between EUV energies ranging from 320 nJ down to several picojoules. For low fluences, a linear responsivity of 7.14 mAs/J could be determined. Saturation starts at approximately 1 nJ, merging into a linear response of 0.113 mAs/J, which could be attributed to the photoeffect on the Au electrodes on top of the diode. Furthermore, degradation tests were performed up to an absolute dose of 3.3x10(19) photons/cm(2). AlGaN photodiodes were compared to commercially available silicon-based photodetectors. For AlGaN diodes, responsivity does not change even for the highest EUV dose, whereas the response of the Si diode decreases linearly to approximately 93% after 2x10(19) photons/cm(2). PMID:19791927

Barkusky, Frank; Peth, Christian; Bayer, Armin; Mann, Klaus; John, Joachim; Malinowski, Pawel E

2009-09-01

290

Radiation damage resistance of AlGaN detectors for applications in the extreme-ultraviolet spectral range  

Science.gov (United States)

We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky-photodiode-based detectors. AlGaN layers were grown using metal-organic chemical vapor deposition (MOCVD) on Si(111) wafers. The diodes were characterized at a wavelength of 13.5 nm using a table-top extreme-ultraviolet (EUV) radiation source, consisting of a laser-produced xenon plasma and a Schwarzschild objective. The responsivity of the diodes was tested between EUV energies ranging from 320 nJ down to several picojoules. For low fluences, a linear responsivity of 7.14 mAs/J could be determined. Saturation starts at approximately 1 nJ, merging into a linear response of 0.113 mAs/J, which could be attributed to the photoeffect on the Au electrodes on top of the diode. Furthermore, degradation tests were performed up to an absolute dose of 3.3×1019 photons/cm2. AlGaN photodiodes were compared to commercially available silicon-based photodetectors. For AlGaN diodes, responsivity does not change even for the highest EUV dose, whereas the response of the Si diode decreases linearly to ˜93% after 2×1019 photons/cm2.

Barkusky, Frank; Peth, Christian; Bayer, Armin; Mann, Klaus; John, Joachim; Malinowski, Pawel E.

2009-09-01

291

Free-Free Emission in the Far-Ultraviolet Spectral Range: A Resource for Diagnosing Solar and Stellar Flare Plasmas  

Science.gov (United States)

We report the detection of free-free (bremsstrahlung) emission near 1200 Å from a flare at the solar limb observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) spacecraft. The observations consist of a time series of slit spectra at a fixed pointing that lasted almost 2 hr, during which the observed solar region produced a C8 flare. Using the free-free continuum intensities in conjunction with intensities of high-temperature (106-107 K) emission lines that appear in the same wavelength range, we derive the flare plasma electron density, electron temperature, emission measure, and nonthermal mass motions before, during, and after the flare. We describe a new diagnostic method for determining the temperature of cooling plasmas. Because the free-free radiation is emitted primarily by the interaction of electrons with nuclei of H and He atoms, we are also able to derive the Fe/H, Al/H, and Ca/H abundance ratios from the line intensities of highly ionized Fe, Al, and Ca lines and the intensities of the free-free emission, assuming a He abundance. The present work demonstrates the exceptional plasma diagnostic potential of ultraviolet free-free continuum radiation when coupled with emission-line intensities. We demonstrate that a similar technique could be employed to diagnose plasma properties of stellar flares using a high-resolution spectrometer with a sufficiently large effective collecting area.

Feldman, U.; Landi, E.; Doschek, G. A.; Dammasch, I.; Curdt, W.

2003-08-01

292

Time-dependent strain analysis of mirrors illuminated with intense femtosecond pulses in the soft x-ray spectral range  

Science.gov (United States)

We consider the three-dimensional time-dependent thermoelastic problem for a thin silicon blade illuminated by a single soft x-ray free-electron laser (FEL) pulse of fs duration. An exact analytical solution is given. It shows that the heat flow in the blade is very slow, which might pose problems for cooling if the FEL is operated to produce a train of pulses with short spacing. Surface mechanical oscillations are generated shortly after the FEL pulse is absorbed, and resonant enhancement by subsequent pulses in the pulse train is an issue. After the FEL pulse, but long before the heat front reaches the heat sink, the optical surface bulges outwards. The effects of a FEL pulse train with thousands of pulses need more detailed study, but experiments with single pulses at kHz rates are not expected to suffer from thermally induced surface figure distortion. The emphasis in this article is not on whether the blade will escape melting, but rather to what extent the profile of a high precision optical surface is preserved under FEL illumination, a question of major interest if focal spots with diameters in the micron range are needed.

de Castro, A. R. B.; Möller, T.

2005-06-01

293

A new method to extract gas concentrations in the ultraviolet and visible wavelength ranges, based on differential optical absorption technique and Fourier transform  

International Nuclear Information System (INIS)

By combining differential optical absorption technique with Fourier transformation we obtain a measuring method exhibiting high sensitivity, good accuracy and good robustness against wavelength displacements in the spectrum obtained. The method also separates different gases in the absorption spectrum from each other in an effective way. The above mentioned features make this method attractive. The ability to separate gases is especially rewarding; it means that we need not know which gases are present when we start to measure. The only prerequisite is that the gases involved absorb in the wavelength range that is to be measured. The method appears to be well suited for the detection of atmospheric pollutions

294

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

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...

Saldin, E L; Yurkov, M V

2004-01-01

295

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

CERN Document Server

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...

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

2013-01-01

296

Spectral Response of Indium Oxynitride Thin Films  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work we study the electrical properties as spectral response, resistivity and quantum efficiency of nanostructured indium oxynitride deposited by reactive RF magnetron sputtering. This material shows multi-functionality in electrical and photonic applications. It shows transparency in visible range, wide band gap, high resistivity, low linkage current and response for light. The deposition processes were performed in a home build magnetron sputtering system, using a four-i...

Sparvoli M.; Onmori R.K.; Chubaci J.F.D.

2013-01-01

297

The spectral characteristics of Gd sub 2 SiO sub 5 :Eu sup 3 sup + in VUV-UV range  

CERN Document Server

Synchrotron radiation source was used to investigated the spectral characteristics of Gd sub 2 SiO sub 5 :Eu sup 3 sup + in VUV-UV range. The various energy transfers at room temperature and 10 K, including from host or Gd sup 3 sup + ions to Eu sup 3 sup + ions and transfer between Eu sup 3 sup + ions at two different lattice sites, were discussed. In addition the emission spectra under 186 nm and 276 nm excitation were compared from the view of quantum cutting. The results indicate that Gd sub 2 SiO sub 5 :Eu sup 3 sup + is a kind of material with potential high efficiency quantum cutting

Chen Yong; Wei Ya Guang; Tao Ye

2002-01-01

298

Shock-tube studies of atomic silicon emission in the spectral range 180 to 300 nm. [environment simulation for Jupiter probes  

Science.gov (United States)

Emission spectroscopy of shock-heated atomic silicon was performed in the spectral range 180 to 300 nm, in an environment simulating the ablation layer expected around a Jovian entry probe with a silica heat shield. From the spectra obtained at temperatures from 6000 to 10,000 K and electron number densities from 1 quadrillion to 100 quadrillion per cu cm, the Lorentzian line-widths were determined. The results showed that silicon lines are broadened significantly by both electrons (Stark broadening) and hydrogen atoms (Van der Waals broadening), and the combined line-widths are much larger than previously assumed. From the data, the Stark and the Van der Waals line-widths were determined for 34 silicon lines. Radiative transport through a typical shock layer was computed using the new line-width data. The computations showed that silicon emission in the hot region is large, but it is mostly absorbed in the colder region adjacent to the wall.

Prakash, S. G.; Park, C.

1978-01-01

299

Light-Emitting-Diodes based on ordered InGaN nanocolumns emitting in the blue, green and yellow spectral range  

Science.gov (United States)

The growth of ordered arrays of InGaN/GaN nanocolumnar light emitting diodes by molecular beam epitaxy, emitting in the blue (441 nm), green (502 nm), and yellow (568 nm) spectral range is reported. The device active region, consisting of a nanocolumnar InGaN section of nominally constant composition and 250 to 500 nm length, is free of extended defects, which is in strong contrast to InGaN (planar) layers of similar composition and thickness. Electroluminescence spectra show a very small blue shift with increasing current (almost negligible in the yellow device) and line widths slightly broader than those of state-of-the-art InGaN quantum wells.

Bengoechea-Encabo, A.; Albert, S.; Lopez-Romero, D.; Lefebvre, P.; Barbagini, F.; Torres-Pardo, A.; Gonzalez-Calbet, J. M.; Sanchez-Garcia, M. A.; Calleja, E.

2014-10-01

300

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

Science.gov (United States)

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

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

 
 
 
 
301

[Spectral properties of myoglobins from aquatic mammals].  

Science.gov (United States)

Spectral characteristics of ferri- and ferroderivatives of myoglobins have been studied in semiwater mammals. Extinction coefficients in the visible range of the spectrum have been determined for different derivatives of the studied heme proteins. It is established that variations in the maxima and minima of different absorption bands are inconsiderable. Close positions of isobestic points have been revealed for a system of oxyglobin and reduced myoglobin obtained from the muscles of the studied animals. Changes in spectral characteristics of methmyoglobins, induced by the effect of different pH, are identical, which evidences for similarity of the surroundings of active site of the studied heme proteins. PMID:1882458

Sukhomlynov, B F; Korobov, V M; Fedorovych, A M; Vasil'ieva, V O

1991-01-01

302

Salinity and spectral reflectance of soils  

Science.gov (United States)

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.

Szilagyi, A.; Baumgardner, M. F.

1991-01-01

303

Visible Light Communication  

Directory of Open Access Journals (Sweden)

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

Rajan Sagotra, Reena Aggarwal

2013-04-01

304

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

Directory of Open Access Journals (Sweden)

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.

Ignacio Melendez-Pastor

2013-12-01

305

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

Science.gov (United States)

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.

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

306

ORFEUS II echelle spectra On the influence of iron-group line blanketing in the Far-UV spectral range of hot subdwarfs  

CERN Document Server

We present an analysis of the subdwarf O star Feige 67 with a fully metal-line blanketed NLTE model atmosphere based on high-resolution Far-UV (912-2000 A) and Near-UV (2000-3400 A) spectra from new ORFEUS II echelle observations and the IUE final archive. The Far-UV spectra are heavily blanketed by iron and nickel lines, preventing the detection of the stellar continuum and complicating the abundance analysis. Important points concerning the account for blanketing by millions of iron-group lines and for an accurate determination of iron and nickel abundances are discussed: The usage of all theoretically and experimentally known line opacities of the iron-group elements, the consideration of a broad wavelength range for a reliable determination of the stellar continuum flux, and the role of interstellar reddening. This paper outlines a basic approach for spectral analysis of future high-resolution Far-UV spectra of hot compact stars. During this study we re-analyzed the iron and nickel abundance of our exempl...

Deetjen, J L

2000-01-01

307

InSb quantum dots for the mid-infrared spectral range grown on GaAs substrates using metamorphic InAs buffer layers  

Science.gov (United States)

Type II InSb/InAs quantum dots (QDs) were successfully grown on GaAs substrates using three different metamorphic buffer layer (MBL) designs. The structural properties of the resulting metamorphic InAs buffer layers were studied and compared using cross-sectional transmission electron microscopy and high resolution x-ray diffraction measurements. Photoluminescence (PL) originating from the InSb QDs was observed from each of the samples and was found to be comparable to the PL of InSb QDs grown onto homo-epitaxially deposited InAs. The 4 K PL intensity and linewidth of InSb QDs grown onto a 3 µm thick InAs buffer layer directly deposited onto GaAs proved to be superior to that from QDs grown onto an InAs MBL using either AlSb or GaSb interlayers. Light-emitting diode structures containing ten layers of InSb QD in the active region were subsequently fabricated and electroluminescence from the QDs was obtained in the mid-infrared spectral range up to 180 K. This is the first step towards obtaining mid-infrared InSb QD light sources on GaAs substrates.

Lu, Q.; Zhuang, Q.; Marshall, A.; Kesaria, M.; Beanland, R.; Krier, A.

2014-07-01

308

Flexible metamaterials at visible wavelengths  

Energy Technology Data Exchange (ETDEWEB)

We report on the fabrication and characterization of plasmonic structures on flexible substrates (Metaflex) and demonstrate the optical properties of a single layer of Metaflex. The layer exhibits a plasmonic resonance in the visible region around 620 nm. We show experimental and numerical results for both nano-antennas and fishnet geometries. We anticipate the use of Metaflex as a building block for flexible metamaterials in the visible range.

Di Falco, Andrea; Ploschner, Martin; Krauss, Thomas F, E-mail: adf10@st-andrews.ac.u [School of Physics and Astronomy, University of St Andrews, North Haugh, KY16 9SS, Fife (United Kingdom)

2010-11-15

309

VISIBLE CONCRETE SURFACES  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The diploma paper deals with visible concrete surfaces as facade cladding of architecture. The first part describes concrete and visible concrete in theory. It presents methods of producing or constructing visible concretes and procedures of visible concrete surfaces processing. Moreover the surface defects when working with visible concrete are comprehended. It also deals with specific examples of buildings which are selected according to the different visible concrete surfaces processin...

Z?iher, Tina

2012-01-01

310

Beamline and station of radiometry in the UV-VUV spectral regions  

International Nuclear Information System (INIS)

Over the last few years, along with the developments of space science, astrophysics, controlled nuclear fusion, plasma physics and ultraviolet laser research, the need is urgent for the radiometric standards from the infrared, the visible and the near ultraviolet spectral ranges expanding to the ultraviolet, the vacuum ultraviolet and the soft X-ray spectral ranges. Not only can synchrotron radiation (SR) be used as spectral radiation standard source in the ultraviolet, the visible and the infrared spectral ranges, but also it can be used as primary source standard in the vacuum ultraviolet and the soft X-ray spectral ranges. SR can calibrate spectral radiation for various radiation sources and the detectors. The Spectral Radiation Standard and Metrology beam-lines and experimental stations in the NSRL Phase II Project are under construction that include two beam-lines and three-experimental stations. This paper describes the dedicated facility for light source of primary standard and transfer standard in the UV and VUV spectral ranges from 110 to 400 nm

311

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)

312

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

DEFF Research Database (Denmark)

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.

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

2012-01-01

313

Visible light optical coherence tomography  

Science.gov (United States)

We demonstrate for the first time optical coherence tomography (OCT) in the visible wavelength range with unprecedented sub-micrometer axial resolution, achieved by employing a photonic crystal fiber in combination with a sub-15fs Ti:sapphire laser (FEMTOLASERS). The shaped emission spectrum produced by the photonic crystal fiber ranges from 535 nm to 700 nm (centered at ~600 nm) resulting in ~0.9 micrometers axial OCT resolution in air corresponding to ~0.6 micrometers in biological tissue. Preliminary demonstration of the sub-micrometer resolution achieved with this visible light OCT setup is demonstrated on a 2.2 micrometers thick nitrocellulose membrane. The visible wavelength range not only enables extremely high axial resolution for OCT imaging, but also offers an attractive region for spectroscopic OCT.

Povazay, Boris; Apolonski, Alexander A.; Unterhuber, Angelika; Hermann, Boris; Bizheva, Kostadinka K.; Sattmann, Harald; Russell, Phillip S. J.; Krausz, Ferenc; Fercher, Adolf F.; Drexler, Wolfgang

2002-06-01

314

A Fourier transform Raman spectrometer with visible laser excitation  

CERN Document Server

We present the development and performance of a Fourier transformation (FT) based Raman spectrometer working with visible laser (532 nm) excitation. It is generally thought that FT-Raman spectrometers are not viable in the visible range where shot-noise limits the detector performance and therein they are outperformed by grating based, dispersive ones. We show that contrary to this common belief, the recent advances of high-performance interference filters makes the FT-Raman design a valid alternative to dispersive Raman spectrometers for samples which do not luminesce. We critically compare the performance of our spectrometer to two dispersive ones: a home-built single channel and a state-of-the-art CCD based instruments. We demonstrate a similar or even better sensitivity than the CCD based dispersive spectrometer particularly when the laser power density is considered. The instrument possesses all the known advantages of the FT principle of spectral accuracy, high throughput, and economic design. We also d...

Dzsaber, S; Bernáth, B; Gyüre, B; Fehér, T; Kramberger, C; Pichler, T; Simon, F

2014-01-01

315

Human contrast threshold and astronomical visibility  

Science.gov (United States)

The standard visibility model in light-pollution studies is the formula of Hecht, as used e.g. by Schaefer. 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's), 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 in 1947, enabling the sky brightness at that time to be determined. The result is darker than the calculation by Garstang, implying that light pollution grew more rapidly in subsequent decades than has been supposed. The model is applied to the nebular observations of William Herschel, enabling his visual performance to be quantified. Proposals are made regarding sky quality indicators for public use.

Crumey, Andrew

2014-08-01

316

Feature Point Descriptors: Infrared and Visible Spectra  

Directory of Open Access Journals (Sweden)

Full Text Available 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.

Pablo Ricaurte

2014-02-01

317

Feature point descriptors: infrared and visible spectra.  

Science.gov (United States)

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. PMID:24566634

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

2014-01-01

318

Feature Point Descriptors: Infrared and Visible Spectra  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

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

2014-01-01

319

Visibility of Pulsar Emission: Motion of the Visible Point  

Science.gov (United States)

A standard model for the visibility of pulsar radio emission is based on the assumption that the emission is confined to a narrow cone about the tangent to a dipolar field line. The widely accepted rotating vector model (RVM) is an approximation in which the line of sight is fixed and the field line is not strictly tangent to it. We refer to an exact treatment (Gangadhara, 2004) as the tangent model. In the tangent model (but not in the RVM) the visible point changes as a function of pulsar rotational phase, ?, defining a trajectory on a sphere of radius r. We solve for the trajectory and for the angular velocity of the visible point around it. We note the recent claim that this motion is observable using interstellar holography (Pen et al., 2014). We estimate the error introduced by use of the RVM and find that it is significant for pulsars with emission over a wide range of ?. The RVM tends to underestimate the range of ? over which emission is visible. We suggest that the geometry alone strongly favors the visible pulsar radio being emitted at a heights more than ten percent of the light-cylinder distance, where our neglect of retardation effects becomes significant.

Yuen, R.; Melrose, D. B.

2014-10-01

320

Caracterización espectral y mineralógica de los suelos del valle del río Cauca por espectroscopía visible e infrarroja (400 - 2.500 nm) / Soil spectral characterization and mineralogy of the Cauca River Valley by visible and infrared (400 - 2,500 nm) spectroscopy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish Las librerías espectrales se utilizan para identificar diferentes tipos de suelo a partir de análisis espectrales que caracterizan su composición mineralógica y química. Los objetivos del presente trabajo consistieron en determinar si existen diferencias en el perfil espectral de los suelos del vall [...] e geográfico del río Cauca a nivel de subgrupo taxonómico; y cuantificar en sus perfiles espectrales la abundancia de minerales arcillosos. Por medio de un análisis de conglomerados se seleccionaron las muestras más homogéneas de cada subgrupo taxonómico para construir el perfil espectral de cada uno de ellos. El modelo linear spectral unmixing se utilizó para determinar las concentraciones de minerales arcillosos. A nivel de subgrupo taxonómico se observaron diferencias en la magnitud de los perfiles espectrales, así como en sus longitudes de onda a los 1.400, 1.900 y 2.200 nm. El modelo utilizado permite caracterizar de manera objetiva las concentraciones de minerales arcillosos de cada suelo a partir de su perfil espectral. Abstract in english Spectral libraries are used to identify different soil types based on spectral analyses which feature their mineralogical and chemical composition. On these grounds, the objective of the present work consisted in determining whether there are any differences in the spectral profile of the soils of t [...] he geographical Cauca Valley at the taxonomic subgroup level; and to assess their spectral profiles in terms of the abundance of clay minerals. By means of cluster analysis we selected the most homogeneous samples of each taxonomic sub group to elaborate its spectral profile. Clay mineral concentrations were determined by means of a linear spectral unmixing model. Differences among taxonomic subgroups were found in both the magnitude of the spectral profiles and their wavelengths (1.400, 1.900 and 2.200 nm). Based on soil spectral profiles, the applied model can be used to objectively characterize clay mineral concentrations.

Ernesto, Bastidas-Obando; Javier A., Carbonell.

2010-08-01

 
 
 
 
321

Current status of visibility sensors for aviation  

Science.gov (United States)

The development of a new increased range higher visibility was investigated. The visibility sensor that is currently is the Transmissometer. Current transmissometer technology provides only a factor of 10 dynamic range with a single base line. The FAA is preparing to install automated weather observing systems (AWOS) at many locations. These systems require visibilities up to approximately 5 miles. To use a transmissometer for this type of measurement, the base line must be about 1,000 feet; where alignment becomes very difficult to maintain. New technologies were developd for measuring visibility. Improved transmissometers, forward-scatter meters and back-scatter meters have become available. A current practical issue for visibility sensors is how to specify one that is good enough to meet the needs of aviation. The first question is what performance is required; how accurately must the sensor measure? Visibility sensors do not actually measure the visibility directly. The purpose of measuring the visibility is to predict what the pilot will see a considerable distance away from the sensor location. The atmosphere introduces considerable variation in the measurement and the basic sensor accuracy needed is difficult to define. The second question for high visibilities is what to use as the standard reference sensor. The third question pertains to the competitive procurement of visibility sensors, which is mandated at present. Two acceptance test procedures to be used to insure satisfactory sensor performance is examined.

Burnham, D. C.

1983-01-01

322

Spectral mixture analysis of multispectral thermal infrared images  

Science.gov (United States)

Remote spectral measurements of light reflected or emitted from terrestrial scenes is commonly integrated over areas sufficiently large that the surface comprises more than one component. Techniques have been developed to analyze multispectral or imaging spectrometer data in terms of a wide range of mixtures of a limited number of components. Spectral mixture analysis has been used primarily for visible and near-infrared images, but it may also be applied to thermal infrared data. Two approaches are reviewed: binary mixing and a more general treatment for isothermal mixtures of a greater number of components.

Gillespie, Alan R.

1992-01-01

323

Validation of line and continuum spectroscopic parameters with measurements of atmospheric emitted spectral radiance from far to mid infrared wave number range  

International Nuclear Information System (INIS)

The latest release of a high-resolution transmission molecular absorption database along with two improved models of water vapor continuum absorption are used to check their impact on the improvement of state-of-art radiative transfer. Radiative transfer performance has been assessed using high mountains atmospheric emitted spectral downwelling radiance observations in the 360-1200 cm-1 spectral regions. These high mountains observations are particularly suited to check the behavior and performance in the water vapor rotation band. In addition, they also have allowed us to gain insight into understanding the quality of recent new compilation of lines and related treatment for the ?2 CO2 band and the O3 band at 9.6?m. Comparisons are made between forward calculations of atmospheric transmission spectra and spectral radiances measured using two ground-based Fourier transform instruments. The results demonstrate that water vapor absorption largely benefits from the recent improvement in the related continuum (both self and foreign). In addition, ozone absorption is very accurately reproduced and, although to a less extent, this is also the case of CO2 absorption in the long wave ?2 band.

324

A Spectral Map Of Mercury From MESSENGER  

Science.gov (United States)

We use orbital data from the Mercury Surface and Atmospheric Composition Spectrometer (MASCS) Visible and Near Infrared Spectrograph (VIRS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft to study subtle compositional variations across the surface of Mercury. VIRS reflectance spectra obtained from orbit allow identification and classification of spectral units, many of which collocate with geologic features such as pyroclastic deposits; low-reflectance material (LRM); bright, fresh-appearing impact craters; and hollows. The vast majority of the surface is composed of plains units with brightness and spectral reflectance ratios (e.g., 415 nm / 750 nm and 310 nm / 390 nm) that vary within a small range about mean values for the planet. Analysis of VIRS reflectance data in the context of Mercury Dual Imaging System (MDIS) color and high-resolution images enables identification of large regions with similar spectral properties. Our spectral map of Mercury covers approximately 70% of the planet (excluding polar regions and two regions for which calibration refinement is pending). On the basis of brightness, spectral ratio variations, and superposition relationships in the image data, we define four large-scale spectral units in Mercury plains, as well as six additional spectral units of smaller area. The four large-scale spectral units cover (1) 48.7% (brightness and spectral ratio parameters within a few percent of planetary mean values) (2) 31.6% (higher reflectance, higher 310 nm / 390 nm values than mean), (3) 12.9% (higher reflectance, lower 415 nm / 750 nm values than mean), and (4) 6.8% (lower reflectance and higher 310 nm / 390 nm values than mean) of the mapped area. Spectrally defined plains units correspond broadly to plains units defined by morphology and color imaging; e.g., unit 2 corresponds to the previously defined high-reflectance red plains (HRP), unit 3 to the northern smooth plains and the smooth plains inside Caloris basin, and unit 4 to low-reflectance blue plains (LPB). Other spectrally distinct units include bright areas that correspond to fresh craters, crater ejecta, and rays; spectrally 'red' areas that correspond to pyroclastic materials; and dark materials that correspond to LRM.

Izenberg, N. R.; Pahsai, P.; Klima, R. L.; Blewett, D. T.; Goudge, T. A.; Solomon, S. C.

2013-12-01

325

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

Science.gov (United States)

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.

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

2014-11-01

326

Visibility of pulsar emission: motion of the visible point  

CERN Document Server

A standard model for the visibility of pulsar radio emission is based on the assumption that the emission is confined to a narrow cone about the tangent to a dipolar field line. The widely accepted rotating vector model (RVM) is an approximation in which the line of sight is fixed and the field line is not strictly tangent to it. We refer to an exact treatment (Gangadhara 2004) as the tangent model. In the tangent model (but not in the RVM) the visible point changes as a function of pulsar rotational phase, $\\psi$, defining a trajectory on a sphere of radius $r$. We solve for the trajectory and for the angular velocity of the visible point around it. We note the recent claim that this motion is observable using interstellar holography (Pen et al. 2014). We estimate the error introduced by use of the RVM and find that it is significant for pulsars with emission over a wide range of $\\psi$. The RVM tends to underestimate the range of $\\psi$ over which emission is visible. We suggest that the geometry alone stro...

Yuen, R

2014-01-01

327

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

328

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)

329

Ultraviolet, Visible, and Fluorescence Spectroscopy  

Science.gov (United States)

Spectroscopy in the ultraviolet-visible (UV-Vis) range is one of the most commonly encountered laboratory techniques in food analysis. Diverse examples, such as the quantification of macrocomponents (total carbohydrate by the phenol-sulfuric acid method), quantification of microcomponents, (thiamin by the thiochrome fluorometric procedure), estimates of rancidity (lipid oxidation status by the thiobarbituric acid test), and surveillance testing (enzyme-linked immunoassays), are presented in this text. In each of these cases, the analytical signal for which the assay is based is either the emission or absorption of radiation in the UV-Vis range. This signal may be inherent in the analyte, such as the absorbance of radiation in the visible range by pigments, or a result of a chemical reaction involving the analyte, such as the colorimetric copper-based Lowry method for the analysis of soluble protein.

Penner, Michael H.

330

[Research on spectral reflectance characteristics for Glycyrrhizae Radix].  

Science.gov (United States)

In order to study the spectral reflectance differences of Glycyrrhizae Radix under different growth conditions and lay the foundation for quantitative monitoring of Glycyrrhizae Radix remote sensing images, spectra of Glycyrrhiza species under different growth period and different varieties and different regions were measured by a portable spectrometer. The results showed that the reflectivity of annual G. uralensis was obviously higher than that of the two years plant in the visible light band own to the contents of crown layer chlorophyll. The reflectivity of two years G. pallidiflora was higher than that of G. uralensis in the near infrared band own to the leaf area index and the content of leaf water. The red edge spectrum of annual plant fluctuated largely than that of two years plant due to vegetation coverage and leaf area index. G. pallidiflora grew well than G. uralensis. Under different regions of the Glycyrrhiza species, spectral data analysis showed that within a certain range, the average annual precipitation and average annual evaporation were the major factors to affect the differences of Glycyrrhiza species spectral data under different regions owe to the leaf water content, the higher leaf water content, the lower spectral reflectance. The principal component analysis and continuum-removed method of the spectral data under different regions found that, within a certain range, the average annual precipitation and average annual evaporation were the major factors caused by the differences of Glycyrrhiza species spectral data under the different regions, Glycyrrhiza species spectral similarity related to the spatial distance. PMID:24946542

Li, Hui; Xie, Cai-Xiang; Li, Xiao-Jin; Wen, Mei-Jia; Jia, Guang-Lin; Shi, Ming-Hui; Guo, Bao-Lin; Jia, Xiao-Guang

2014-02-01

331

Visible-infrared properties of controlled laboratory soils  

Science.gov (United States)

Almost all surfaces available for remote observation consist of particulate materials or soils. The distribution of mean particle sizes depend on the original material and physical and chemical processes that have acted on the surface over time. It is well known that the optical and infrared spectral properties of materials depends on the particle size. There has been little detailed study, however, of natural soils, namely particulate materials with a range of particle sizes. Current models for intimate mixing typically use an average particle size in calculations and are most successful when the particle size is constrained by known sieve fractions. Preliminary results of a study in which soils were prepared with a known composition and range of particle sizes are reported. This discussion presents the overall visible to infrared properties of these synthetic soils and evaluates the mid-infrared properties.

Pieters, C. M.; Mustard, J. F.; Pratt, S. F.; Sunshine, J. M.; Hoppin, Andrew

1993-01-01

332

Experimental method for observation prediction based on the decision matrix through day/night equipments in NIR and LWIR spectral ranges  

Science.gov (United States)

The paper presents an evaluation methodology and the results of some experiments that have been made in laboratory in order to determine the target's detection's probability depending on the target's contrast and the observers' age. The main goal was to assure the model for an optimal feature's configuration for a device used to enable the view during day or night, so that we can estimate, within improper view conditions, its visibility boundaries during day and night. The base of method's principle is the Bayes' theorem, and the authors have used in their experiments the technique of estimation by probability of real positive and real negative that is also used in medical evaluation of images. The authors have used an instrument layout in the laboratory that included an uncooled 8- 12 ?m thermal camera, a CCD and a ICU camera, an USAF pattern and a set of chemical compositions that produce aerosols with different concentrations. It has been proved that the detection probability decreases proportionally by age, but being differentiated by the contrast between the target and the background; it has been presented the diagram of the probability variation and the analytical relationships that approximate it, in terms of contrast and aerosols' concentration features.

Borcan, Octavia C.; Spulber, Catalin A.

2009-05-01

333

Analysis of the influence of the plasma thermodynamic regime in the spectrally resolved and mean radiative opacity calculations of carbon plasmas in a wide range of density and temperature  

International Nuclear Information System (INIS)

In this work the spectrally resolved, multigroup and mean radiative opacities of carbon plasmas are calculated for a wide range of plasma conditions which cover situations where corona, local thermodynamic and non-local thermodynamic equilibrium regimes are found. An analysis of the influence of the thermodynamic regime on these magnitudes is also carried out by means of comparisons of the results obtained from collisional-radiative, corona or Saha–Boltzmann equations. All the calculations presented in this work were performed using ABAKO/RAPCAL code. -- Highlights: ? Spectrally resolved, multigroup and mean radiative opacities of carbon plasmas are calculated. ? Corona, local thermodynamic and non-local thermodynamic equilibrium regimes are analyzed. ? Simulations performed using the computational package ABAKO/RAPCAL. ? A criterion for the establishment of the thermodynamic regime is proposed.

334

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

CERN Document Server

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.

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

335

Visible fluorescence from ultraviolet excited crude oil  

International Nuclear Information System (INIS)

Radiant fluorescent intensity, from a UV irradiated sample of crude oil in the visible spectral region, was measured as a function of exposure time of the crude oil to the atmosphere. The intensity of the laboratory source of UV irradiation (300--400 nm) was calibrated and compared with the intensity of the sun at sea level through 1 atm. The maximum intensity of the sun excited flourescence was estimated to be 5 times less than that required to be detected by presently available satellite mounted visible spectrum detectors and 500 times less than that required to differentiate one crude oil type from another

336

Spectral filtering for plant production  

Science.gov (United States)

Both plants and animals have one general commonality in their perception of light. They both are sensitive primarily to the 400 to 700 nm wavelength portion of the electromagnetic spectrum. This is referred to as the visible spectrum for animals and as the photosynthetically active radiation (PAR) spectrum for plants. Within this portion of the spectrum, animals perceive colors. Relatively recently it has been learned that within this same spectral range plants also demonstrate varying responses at different wavelengths, somewhat analogous to the definition of various colors at specific wavelengths. Although invisible to the human eye, portions of the electromagnetic spectrum on either side of the visible range are relatively inactive photosynthetically but have been found to influence important biological functions. These portions include the ultraviolet (UV approximately equal to 280-400 nm) and the far-red (FR approximately equal to 700-800 nm). The basic photoreceptor of plants for photosynthesis is chlorophyll. It serves to capture radiant energy which combined with carbon dioxide and water produces oxygen and assimulated carbon, used for the synthesis of cell wall polysaccarides, proteins, membrane lipids and other cellular constituents. The energy and carbon building blocks of photosynthesis sustain growth of plants. On the other hand, however, there are other photoreceptors, or pigments, that function as signal transducers to provide information that controls many physiological and morphological responses of how a plant grows. Known photomorphogenic receptors include phytochrome (the red/far-red sensor in the narrow bands of 655-665 nm and 725-735 nm ranges, respectively) and 'cryptochrome' (the hypothetical UV-B sensor in the 280-320 nm range). Since the USDA team of W. L. Butler, S. B. Hendricks, H. A. Borthwick, H. A. Siegleman and K. Norris in Beltsville, MD detected by spectroscopy, extracted and identified phytochrome as a protein in the 1950's, many other investigators have found evidence of its control functions in plants. Considerably less, however, is known about the yet non-isolated cryptochrome. The information-transferring roles of photoreceptors in plants at specific spectral ranges quite naturally stimulated plant scientists and engineers to consider physically manipulating light to achieve desired physiological and morphological characteristics. One way to manipulate light is to filter it through materials that selectively transmit portions of the sun's spectrum in and near the PAR range.

Young, Roy E.; Mcmahon, Margaret J.; Rajapakse, Nihal C.; Decoteau, Dennis R.

1994-01-01

337

Application of Visible and Near Infrared Spectroscopy for Rapid Analysis of Chrysin and Galangin in Chinese Propolis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A novel method for the rapid determination of chrysin and galangin in Chinese propolis of poplar origin by means of visible and near infrared spectroscopy (Vis-NIR) was developed. Spectral data of 114 Chinese propolis samples were acquired in the 325 to 1,075 nm wavelength range using a Vis-NIR spectroradiometer. The reference values of chrysin and galangin of the samples were determined by high performance liquid chromatography (HPLC). Partial least squares (PLS) models were established usin...

Yong He; Zhengyan Xia; Da-Wen Sun; Pengcheng Nie

2013-01-01

338

Scanning picosecond optical parametric source using potassium dihydrogen phosphate in the visible and near infrared  

International Nuclear Information System (INIS)

An optical parametric source using angle-tuned type II potassium dihydrogen phosphate (KDP) as the nonlinear medium and pumped with 35-ps, 355-nm pulses from an active--passive mode-locked Nd:YAG laser, is described. With a 1.35-mJ pump pulse, conversion efficiencies ranging from 1%--40% in the spectral range 450--650 and 800--1600 nm have been achieved. The ???t products can approach the transform limit, although 15--30 times transform limited is more typical. The merits of the combination of pump wavelength and phase match used here are discussed with respect to the tuning range, spectral width, and ease of operation. Automated scanning was achieved by placing the crystals on stepper-motor controlled rotation stages. A convenient, easily reproducible high peak power source rapidly tunable over much of the visible and near infrared is obtained

339

Bandwidth-variable tunable optical filter unit for illumination and spectral imaging systems using thin-film optical band-pass filters.  

Science.gov (United States)

An optical filter unit is demonstrated, which uses two successively arranged tunable thin-film optical band-pass filters and allows for simultaneous adjustment of the central wavelength in the spectral range 522-555 nm and of the spectral bandwidth in the range 3-16 nm with a wavelength switching time of 8 ms?nm. Different spectral filter combinations can cover the complete visible spectral range. The transmitted intensity was found to decrease only linearly with the spectral bandwidth for bandwidths >6 nm, allowing a high maximum transmission efficiency of >75%. The image of a fiber bundle was spectrally filtered and analyzed in terms of position-dependency of the transmitted bandwidth and central wavelength. PMID:23635187

Hennig, Georg; Brittenham, Gary M; Sroka, Ronald; Kniebühler, Gesa; Vogeser, Michael; Stepp, Herbert

2013-04-01

340

Generation of high-power femtosecond supercontinua in the near-IR spectral range using broadband parametric frequency conversion in LBO and DCDA crystals pumped at ? = 620 nm  

Science.gov (United States)

The pump wavelength of parametric amplifiers based on CLBO, DCDA and LBO crystals and pumped by the second harmonic of a femtosecond Cr : forsterite laser (620 nm) is close to optimal for broadband amplification because of the proximity of group velocities of interacting pulses. Injection of a broadband continuum into the range of the signal-wave gain in LBO and DCDA parametric amplifiers, pumped at ? = 620 nm, leads to generation of broadband femtosecond pulses with a spectrum ranging from 1050 to 1600 nm and peak powers up to 20 MW.

Podshivalov, A. A.; Potemkin, F. V.; Sidorov-Biryukov, D. A.

2014-09-01

 
 
 
 
341

Effect of GaAsP barrier layers on the parameters of InGaAs/AlGaAs laser diodes emitting in the 1050-1100-nm spectral range  

International Nuclear Information System (INIS)

To improve the parameters of laser diodes emitting in the 1000-1070-nm spectral range and develop highly efficient laser diodes emitting in the 1070-1100-nm range, it is proposed to introduce GaAsP barrier layers into the active region of the quantum-well InGaAs/AlGaAs heterostructure, which compensate for enhanced mechanical stresses. This considerably improves the luminescence characteristics of heterostructures and changes conditions for generating misfit dislocations. The long-wavelength lasing at 1100 nm becomes possible due to an increase in the thickness of quantum wells and in the molar fraction of InAs in them. The manufactured laser diodes emitting in the 1095-1100-nm range have low threshold currents, the high output power and high reliability. (lasers)

342

Komatiites as Mercury surface analogues: Spectral measurements at PEL  

Science.gov (United States)

The elemental composition of Mercury's surface, which has been recently measured by the NASA MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, suggests a mineralogy dominated by magnesium-rich orthopyroxene and feldspar. The most magnesium-rich and aluminium-poor regions of Mercury's surface (which are presumably orthopyroxene-rich) have compositions, and possibly mineralogies, analogous to terrestrial boninites and basaltic komatiites. Unfortunately, little is known about the spectral properties of komatiites, especially at the high surface temperatures of Mercury. We therefore have collected three terrestrial komatiites with different compositions plus a synthetic komatiitic sample, and measured their reflectances in the visible and thermal infrared spectral ranges. Samples divided into four grain size ranges (when enough material was available) were measured fresh and after thermal processing in vacuum (10 Pa) at 500 °C, comparable to Mercury peak surface temperatures. Our measurements show that spectral changes between fresh and thermally processed samples occur in both spectral channels, but are stronger in the visible range, with reddening affecting all the samples, while darkening is more selective. It is important to note that darkening and reddening after thermally processing the samples are independent of the komatiites ferrous iron content. In fact the synthetic sample which is nearly iron-free is most strongly affected. From our study it turns out that thermally processing the samples in vacuum at Mercury surface temperature produces the removal of samples' colour centres. The results of our study show also that the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument on MESSENGER orbiting Mercury currently cannot distinguish between different compositions of komatiites, while the future MErcury Radiometer and Thermal infrared Imaging Spectrometer (MERTIS) on the upcoming ESA BepiColombo mission will resolve their differences in the 7-14 ?m spectral range.

Maturilli, Alessandro; Helbert, Jörn; St. John, James M.; Head, James W.; Vaughan, William M.; D'Amore, Mario; Gottschalk, Matthias; Ferrari, Sabrina

2014-07-01

343

Redoubling spectral resolution  

Science.gov (United States)

Using two immersed gratings in tandem, a spectrograph can be designed of size not much larger than a simple conventional Cassegrain spectrograph, with the same advantages of long accessible free spectral range, long slit, and multi-object capability, and in addition with spectral resolutions at least as high as are provided by an echelle spectrograph at the same slit width.

Wynne, C. G.

1992-01-01

344

Visibility and Citation Impact  

Directory of Open Access Journals (Sweden)

Full Text Available The number of publications is the first criteria for assessing a researcher output. However, the main measurement for author productivity is the number of citations, and citations are typically related to the paper's visibility. In this paper, the relationship between article visibility and the number of citations is investigated. A case study of two researchers who are using publication marketing tools confirmed that the article visibility will greatly improve the citation impact. Some strategies to make the publications available to a larger audience have been presented at the end of this paper.

Nader Ale Ebrahim

2014-03-01

345

CHARACTERIZATION OF SOIL HUMIC SUBSTANCES BY ULTRAVIOLET-VISIBLE AND SYNCHRONOUS FLUORESCENCE SPECTROSCOPY  

Directory of Open Access Journals (Sweden)

Full Text Available We focused our study on ultraviolet-visible and synchronous fluorescence spectra and indexes of humic subctances isolated from five Czech soil samples: Haplic Chernozem, Luvic Chernozem, Gleyic Luvisol, Haplic Cambisol and Leptic Cambisol. Results indicated the following HS quality: Haplic Chernozem > Luvic Chernozem > Gleyic Luvisol > Haplic Cambisol > Leptic Cambisol. Humic acids and fulvic acids ratios (HA/FA were increasing together with decreasing values of Q4/6 measured in visible spectral range. Highest absorbance in visible spectral range was detected in Haplic Chernozem and Luvic Chernozem. Maximum relative fluorescence was found in Haplic Chernozem. SFS spectra (in emission mode at ??=20 nm showed five main fluorophore peaks at: 360, 470, 488, 502 and 512 nm. Fluorescence behaviour of studied samples was compared with Elliot soil humic acid standard (IHSS. Correlation between fluorescence indexes (F and humification degree (HD R2= 0.88 and between calculated humification degree (HD* and humic acids content (HA sum R2=0.84 and between fluorescence indexes F and HA/FA ratios (R2=0.88 were found.

NAD?ŽDA FASUROVÁ

2011-01-01

346

Acousto-optic tunable filter for spectral imaging  

Science.gov (United States)

In this paper we present a noncollinear TeO2 Acousto-Optic Tunable Filter (AOTF) device for a hyperspectral remote sensing system with moderate spatial and spectral resolution. The single beam configuration of the device will make the imaging optics behind it very simple and thus will make the whole system more compact. The power compensated circuit design of the RF driver of the acousto-optic filter gives relatively high and consistent diffraction efficiency over the whole tuning range in visible. The device can provide about 4° viewfield angle and 5 mm active aperture. The preliminary results have illustrated the capability of the device to be used for spectral imaging. The operation principle of AOTF will be introduced and its optical properties will be analyzed in this paper. The configuration of the AOTF device we developed for spectral imaging will be described and the measured performance of the filter will be summarized.

Dong, Ying; You, Zheng; Gao, Peng

2002-09-01

347

Unit Rectangle Visibility Graphs  

CERN Document Server

Over the past twenty years, rectangle visibility graphs have generated considerable interest, in part due to their applicability to VLSI chip design. Here we study unit rectangle visibility graphs, with fixed dimension restrictions more closely modeling the constrained dimensions of gates and other circuit components in computer chip applications. A graph $G$ is a unit rectangle visibility graph (URVG) if its vertices can be represented by closed unit squares in the plane with sides parallel to the axes and pairwise disjoint interiors, in such a way that two vertices are adjacent if and only if there is a non-degenerate horizontal or vertical band of visibility joining the two rectangles. Our results include necessary and sufficient conditions for $K_n$, $K_{m,n}$, and trees to be URVGs, as well as a number of general edge bounds.

Dean, Alice; Hamilton, Sarah; Pangborn, Greta

2007-01-01

348

Visible Human Project  

Science.gov (United States)

... Technical Data, Track I-D-2: Medical and Health Data, Montréal, Canada, October, 2002. D-Lib magazine article entitled "Accessing the Visible Human Project ® " by Michael J. Ackerman, Ph.D. Send queries ...

349

Switching of the photonic band gap in three-dimensional film photonic crystals based on opal-VO2 composites in the 1.3-1.6 ?m spectral range  

International Nuclear Information System (INIS)

The parameters of three-dimensional photonic crystals based on opal-VO2 composite films in the 1.3-1.6 ?m spectral range important for practical applications (Telecom standard) are numerically calculated. For opal pores, the range of filling factors is established (0.25-0.6) wherein the composite exhibits the properties of a three-dimensional insulator photonic crystal. On the basis of the opal-VO2 composites, three-dimensional photonic film crystals are synthesized with specified parameters that provide a maximum shift of the photonic band gap in the vicinity of the wavelength ?1.5 ?m (?170 meV) at the semiconductor-metal transition in VO2.

350

All-fiber femtosecond Cherenkov laser at visible wavelengths  

DEFF Research Database (Denmark)

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.

Liu, Xiaomin; Lægsgaard, Jesper

2013-01-01

351

Integration of Cd(Zn)Se/ZnSe and GaN-based lasers for optoelectronic applications in a green spectral range  

International Nuclear Information System (INIS)

Cd(Zn)Se/ZnSe green (?=510-530 nm) lasers have been investigated in wide temperature and power ranges under pulsed optical excitation. The minimum laser threshold, maximum external quantum efficiency and maximum output power have been found to be 10 kW/cm2, 12%, and 20 W, respectively, in heterostructures with multiple CdSe quantum disc sheets in an active region. The high temperature stability of threshold power densities (T0=330 K up to 100 C) has been observed. For the optical excitation of the green lasers, optically-pumped InGaN/GaN quantum well heterostructures grown on Si(111) substrates has been used for the first time. The conversion coefficient of energy is about 0.01. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

352

Integration of Cd(Zn)Se/ZnSe and GaN-based lasers for optoelectronic applications in a green spectral range  

Energy Technology Data Exchange (ETDEWEB)

Cd(Zn)Se/ZnSe green ({lambda}=510-530 nm) lasers have been investigated in wide temperature and power ranges under pulsed optical excitation. The minimum laser threshold, maximum external quantum efficiency and maximum output power have been found to be 10 kW/cm{sup 2}, 12%, and 20 W, respectively, in heterostructures with multiple CdSe quantum disc sheets in an active region. The high temperature stability of threshold power densities (T{sub 0}=330 K up to 100 C) has been observed. For the optical excitation of the green lasers, optically-pumped InGaN/GaN quantum well heterostructures grown on Si(111) substrates has been used for the first time. The conversion coefficient of energy is about 0.01. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Sedova, I.V.; Sorokin, S.V.; Toropov, A.A.; Kaygorodov, V.A.; Ivanov, S.V.; Kop' ev, P.S. [Ioffe Physico-Technical Institute of RAS, St.-Petersburg (Russian Federation); Lutsenko, E.V.; Pavlovskii, V.N.; Zubialevich, V.Z.; Gurskii, A.L.; Yablonskii, G.P. [Stepanov Institute of Physics of NAS Belarus, F. Skaryna Ave. 68, 220072 Minsk (Belarus); Dikme, Y.; Kalisch, H.; Szymakowski, A.; Jansen, R.H. [Institut fuer Theoretische Elektrotechnik, RWTH, Aachen (Germany); Schineller, B.; Heuken, M. [AIXTRON AG, Aachen (Germany)

2004-03-01

353

On the spectral domain approach to long-range propagation of high-frequency waves along a strip conductor above a PEC surface  

CERN Document Server

A generic problem of high frequency wave propagation along a metallic strip in parallel above a PEC ground plane is considered. The wave is excited by an elemental electric dipole at an arbitrary location above the PEC plane. The full wave problem, for arbitrary widths of the strip, is solved by means of a mode matching approach and expansion of the strip surface current into Chebyshev polynomials. For narrow strips, an approximate method using only longitudinal currents is derived, and compared numerically with the full wave method. Utilizing the concept of equivalent radius, the approximate method for narrow strips is evaluated numerically against results for thin circular wires. It is concluded that the approximate method is suitable for handling multiple wires in layered structures, wherefore the method has potential usefulness for estimating long range propagation of high frequency waves in wire structures like power lines and railway feeding systems, containing over-head wires and wires submerged into g...

Norgren, Martin

2012-01-01

354

Nanohole-based surface plasmon resonance instruments with improved spectral resolution quantify a broad range of antibody-ligand binding kinetics.  

Science.gov (United States)

We demonstrate an affordable low-noise surface plasmon resonance (SPR) instrument based on extraordinary optical transmission (EOT) in metallic nanohole arrays and quantify a broad range of antibody-ligand binding kinetics with equilibrium dissociation constants ranging from 200 pM to 40 nM. This nanohole-based SPR instrument is straightforward to construct, align, and operate, since it is built around a standard microscope and a portable fiber-optic spectrometer. The measured refractive index resolution of this platform is 3.1 × 10(-6) without on-chip cooling, which is among the lowest reported for SPR sensors based on EOT. This is accomplished via rapid full-spectrum acquisition in 10 ms followed by frame averaging of the EOT spectra, which is made possible by the production of template-stripped gold nanohole arrays with homogeneous optical properties over centimeter-sized areas. Sequential SPR measurements are performed using a 12-channel microfluidic flow cell after optimizing surface modification protocols and antibody injection conditions to minimize mass-transport artifacts. The immobilization of a model ligand, the protective antigen of anthrax on the gold surface, is monitored in real-time with a signal-to-noise ratio of ~860. Subsequently, real-time binding kinetic curves were measured quantitatively between the antigen and a panel of small, 25 kDa single-chain antibodies at concentrations down to 1 nM. These results indicate that nanohole-based SPR instruments have potential for quantitative antibody screening and as a general-purpose platform for integrating SPR sensors with other bioanalytical tools. PMID:22235895

Im, Hyungsoon; Sutherland, Jamie N; Maynard, Jennifer A; Oh, Sang-Hyun

2012-02-21

355

Human Contrast Threshold and Astronomical Visibility  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 p...

Crumey, Andrew

2014-01-01

356

Optical constants determination of samarium, holmium, and erbium in the 1.5-850 eV spectral range using a transmittance method  

Energy Technology Data Exchange (ETDEWEB)

The optical constants {beta} and {delta} of the complex refractive index n{approx}=1-{delta}+i{beta} of Sm, Ho, and Er were obtained in the 1.5-850eV energy range using a transmittance method. Thin films of Sm, Ho, and Er were deposited by magnetron sputtering, and transmittance was measured using synchrotron radiation under a high vacuum condition. All films were directly coated on Si photodiodes, which were used as coating substrates, as well as photon detectors. Si was used as capping layer while a thin W layer was used as barrier against interface diffusion between Si and the highly reactive rare earth elements. The constants {beta} were extracted from transmittance results, and the constants {delta} were calculated based on measured {beta} values using the Kramers-Kronig formalism. Small deficiencies determined from the present data using the partial sum rules were partly attributed to the sputtered film densities that could be slightly lower than the bulk values.

Kjornrattanawanich, Benjawan; Windt, David L.; Seely, John F.

2010-11-01

357

Optical Constants Determination of Samarium Holmium and Erbium in the 1.5-850 eV Spectral Range using a Transmittance Method  

Energy Technology Data Exchange (ETDEWEB)

The optical constants {beta} and {sigma} of the complex refractive index {tilde n} = 1 - {delta} + i{beta} of Sm, Ho, and Er were obtained in the 1.5-850 eV energy range using a transmittance method. Thin films of Sm, Ho, and Dr were deposited by magnetron sputtering, and transmittance was measured using synchrotron radiation using a high vacuum condition. All films were directly coated on Si photodiodes, which were used as coating substrates, as well as photon detectors. Si was used as capping layer while a thin W layer was used as barrier against interface diffusion between Si and the highly reactive rare earth elements. The constants {beta} were extracted from transmittance results, and the constants {sigma} were calculated based on measured {beta} values using the Kramers-Kronig formalism. Small deficiencies determined from the present data using the partial sum rules were partially attributed to the sputtered film densities that could be slightly lower than the bulk values.

B Kjornrattanawanich; D Windt; J Seely

2011-12-31

358

A wide dynamic range CMOS image sensor with 200-1100 nm spectral sensitivity and high robustness to UV right exposure  

Science.gov (United States)

A highly UV-light sensitive and sensitivity robust CMOS image sensor with a wide dynamic range (DR) was developed and evaluated. The developed CMOS image sensor includes a lateral overflow integration capacitor in each pixel in order to achieve a high sensitivity and a wide DR simultaneously. As in-pixel photodiodes (PDs), buried pinned PDs were formed on flattened Si surface. The PD has a thin surface p+ layer with a steep dopant concentration profile to form an electric field that drifts photoelectrons to the pinned n layer. This structure improves UV-light sensitivity and its stability. In addition, a buried channel source follower driver was introduced to achieve a low pixel noise. This CMOS image sensor was fabricated by a 0.18-µm 1-polycrystalline silicon 3-metal CMOS process technology with buried pinned PD. The fabricated image sensor has a high sensitivity for 200-1100 nm light wave band, high robustness of sensitivity and dark current toward UV-light exposure and a wide DR of 97 dB. In this paper, the PD structures, the circuit, the operation sequence and the measurement results of this CMOS image sensor are discussed.

Nasuno, Satoshi; Kawada, Shun; Koda, Yasumasa; Nakazawa, Taiki; Hanzawa, Katsuhiko; Kuroda, Rihito; Sugawa, Shigetoshi

2014-01-01

359

Determination of optical properties of human blood in the spectral range 250 to 1100 nm using Monte Carlo simulations with hematocrit-dependent effective scattering phase functions.  

Science.gov (United States)

The absorption coefficient mu(a), scattering coefficient mu(s), and anisotropy factor g of diluted and undiluted human blood (hematocrit 0.84 and 42.1%) are determined under flow conditions in the wavelength range 250 to 1100 nm, covering the absorption bands of hemoglobin. These values are obtained by high precision integrating sphere measurements in combination with an optimized inverse Monte Carlo simulation (IMCS). With a new algorithm, appropriate effective phase functions could be evaluated for both blood concentrations using the IMCS. The best results are obtained using the Reynolds-McCormick phase function with the variation factor alpha = 1.2 for hematocrit 0.84%, and alpha = 1.7 for hematocrit 42.1%. The obtained data are compared with the parameters given by the Mie theory. The use of IMCS in combination with selected appropriate effective phase functions make it possible to take into account the nonspherical shape of erythrocytes, the phenomenon of coupled absorption and scattering, and multiple scattering and interference phenomena. It is therefore possible for the first time to obtain reasonable results for the optical behavior of human blood, even at high hematocrit and in high hemoglobin absorption areas. Moreover, the limitations of the Mie theory describing the optical properties of blood can be shown. PMID:16822070

Friebel, Moritz; Roggan, André; Müller, Gerhard; Meinke, Martina

2006-01-01

360

Comparison of very long baseline interferometry, GPS, and satellite laser ranging height residuals from ITRF2005 using spectral and correlation methods  

Science.gov (United States)

For the first time, the ITRF2005 input data are in the form of time series of station positions and Earth orientation parameters, together with full variance-covariance information. The first step of the ITRF2005 analysis consists of rigorously stacking each time series to yield a long-term solution per technique. As a by-product, time series of position residuals contain the nonlinear motion of points over the Earth's surface. In this paper, the height residual time series of very long baseline interferometry (VLBI), Global Positioning System (GPS), and satellite laser ranging (SLR) solutions submitted to ITRF2005 are compared. We note that the interpretation of the ITRF2005 position residual time series as observed physical motions at the various stations is delicate due to the inhomogeneous site distribution. We estimate that the network effect may introduce an averaged scatter of 3 and 2 mm in the VLBI and SLR height residuals, respectively. Although noise levels are different among these three techniques, a common 1.0 cycles per year (cpy) frequency is clearly detected. The GPS height annual signal exhibits significant regional correlations that are confirmed by VLBI and SLR measurements in some colocated sites. Significant power near frequencies 2.00, 3.12, and 4.16 cpy is also detected in the individual GPS height residuals time series as mentioned by Ray et al. (2007). However, neither VLBI nor SLR show any significant signals at these frequencies for colocated sites. The agreement between detrended height time series at colocated sites is quantified using a novel method based on Kalman filtering and on maximum likelihood estimation. The GPS and VLBI measurements are shown to agree fairly well for most of the colocated sites. However, agreement is not generally observed in the GPS and SLR comparisons. A study of the interannual signal at colocated sites indicates that the good correlation cannot be completely attributed to the annual harmonic.

Collilieux, X.; Altamimi, Z.; Coulot, D.; Ray, J.; Sillard, P.

2007-12-01

 
 
 
 
361

Luminescent properties in the visible of Er3+/Yb3+ activated composite materials  

Science.gov (United States)

In this work we present the results of our research on luminescent properties in the visible spectral range of two different composite materials - based on polymer (PMMA) and glass (B2O3-BaO-K2O) hosts doped with Er3++Yb3+:Y2O3 nanocrystallites. The luminescent properties of these two composites were carefully studied on the basis of excitation and emission characteristics complemented by fluorescence dynamics profiles. The specific attention was given to the main deactivation mechanisms and up-conversion phenomena as well as analysis of the influence of host’s type on the optical properties of erbium ions.

Jusza, Anna; Anders, Krzysztof; Polis, Pawe?; St?pie?, Ryszard; Lipi?ska, Ludwika; Piramidowicz, Ryszard

2014-08-01

362

Gas discharge and visible spectroscopy on brass electrodes Z-pinch  

International Nuclear Information System (INIS)

Experiments on gas discharge in Z-pinch with brass electrodes in Argon were performed. The gas discharge was characterized by visible spectroscopy on the condition of current density and charge up to 3.0 k A/cm2 and 0.33 C. Reproducible discharges without delay were observed in the pressure range of 22-200 m Torr when radiofrequency pre-ionization was used. Fine brass powder was produced by electrode erosion. In this condition, atoms of copper and zinc were present in the plasma. Spectral lines of residual gas indicated ions of Ar+ and Ar++ in the plasma core. (L.C.J.A.)

363

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

364

Soil organic carbon content estimation with laboratory-based visible-near-infrared reflectance spectroscopy: feature selection.  

Science.gov (United States)

This study, with Yixing (Jiangsu Province, China) and Honghu (Hubei Province, China) as study areas, aimed to compare the successive projection algorithm (SPA) and the genetic algorithm (GA) in spectral feature selection for estimating soil organic carbon (SOC) contents with visible-near-infrared (Vis-NIR) reflectance spectroscopy and further to assess whether the spectral features selected from one site could be applied to another site. The SOC content and Vis-NIR reflectance spectra of soil samples were measured in the laboratory. Savitzky-Golay smoothing and log10(1/R) (R is reflectance) were used for spectral preprocessing. The reflectance spectra were resampled using different spacing intervals ranging from 2 to 10 nm. Then, SPA and GA were conducted for selecting the spectral features of SOC. Partial least square regression (PLSR) with full-spectrum PLSR and the spectral features selected by SPA (SPA-PLSR) and GA (GA-PLSR) were calibrated and validated using independent datasets, respectively. Moreover, the spectral features selected from one study area were applied to another area. Study results showed that, for the two study areas, the SPA-PLSR and GA-PLSR improved estimation accuracies and reduced spectral variables compared with the full spectrum PLSR in estimating SOC contents; GA-PLSR obtained better estimation results than SPA-PLSR, whereas SPA was simpler than GA, and the spectral features selected from Yixing could be well applied to Honghu, but not the reverse. These results indicated that the SPA and GA could reduce the spectral variables and improve the performance of PLSR model and that GA performed better than SPA in estimating SOC contents. However, SPA is simpler and time-saving compared with GA in selecting the spectral features of SOC. The spectral features selected from one dataset could be applied to a target dataset when the dataset contains sufficient information adequately describing the variability of samples of the target dataset. PMID:25061784

Shi, Tiezhu; Chen, Yiyun; Liu, Huizeng; Wang, Junjie; Wu, Guofeng

2014-08-01

365

Spectral and Spread Spectral Teleportation  

Energy Technology Data Exchange (ETDEWEB)

We report how quantum information encoded into the spectral degree of freedom of a single-photon state is teleported using a finite spectrally entangled biphoton state. We further demonstrate how the bandwidth of a teleported waveform can be controllably and coherently dilated using a spread spectral variant of teleportation. We present analytical fidelities for spectral and spread spectral teleportation when complex-valued Gaussian states are prepared using a proposed experimental approach, and we discuss the utility of these techniques for integrating broad-bandwidth photonic qubits with narrow-bandwidth receivers in quantum communication systems.

Humble, Travis S [ORNL

2010-01-01

366

Visible-blind photodetector based on p-i-n junction GaN nanowire ensembles  

International Nuclear Information System (INIS)

We report the synthesis, fabrication and extensive characterization of a visible-blind photodetector based on p-i-n junction GaN nanowire ensembles. The nanowires were grown by plasma-assisted molecular beam epitaxy on an n-doped Si(111) substrate, encapsulated into a spin-on-glass and processed using dry etching and metallization techniques. The detector presents a high peak responsivity of 0.47 A W-1 at - 1 V. The spectral response of the detector is restricted to the UV range with a UV-to-visible rejection ratio of 2 x 102. The dependence on the incident power and the operation speed of the photodetector are discussed.

367

Graphite oxide–TiO2 nanocomposite and its efficient visible-light-driven photocatalytic hydrogen production  

International Nuclear Information System (INIS)

Highlights: ? GO–TiO2 nanocomposites were fabricated by a facile hydrothermal process. ? The implanted GO expand the spectral responsive range of TiO2 to visible light for H2 production. ? As a result, stable photocatalytic H2 production efficiency were obtained over GO–TiO2. - Abstract: Graphite oxide (GO)–TiO2 nanocomposite was prepared by a facile hydrothermal process and was characterized by X-ray powder diffraction, Transmission electron microscopy, UV–vis diffusion reflectance spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. TiO2 particles with average particle size of ?20 nm in the nanocomposites are attached to the surface of GO and/or intercalated into the interlayer of GO. The obtained GO–TiO2 was used as photocatalyst for H2 production under visible light (? ? 420 nm) irradiation, and an optimal photocatalytic H2 production rate of 380 ?mol h?1 can be obtained over 2 wt% GO–TiO2. The encouraging results presented here demonstrate that GO can serve as visible-light-driven photocatalyst and photosensitizer to expand the photoresponsive range of TiO2 to visible light for H2 production. The possible mechanism for H2 production was proposed for better understanding the visible-light-driven photocatalytic behaviour of the GO–TiO2 nanocomposite.

368

Evaluation of Visible Plumes.  

Science.gov (United States)

Developed for presentation at the 12th Conference on Methods in Air Pollution and Industrial Hygiene Studies, University of Southern California, April, 1971, this outline discusses plumes with contaminants that are visible to the naked eye. Information covers: (1) history of air pollution control regulations, (2) need for methods of evaluating…

Brennan, Thomas

369

Spectral Methods  

CERN Document Server

Along with finite differences and finite elements, spectral methods are one of the three main methodologies for solving partial differential equations on computers. This book provides a detailed presentation of basic spectral algorithms, as well as a systematical presentation of basic convergence theory and error analysis for spectral methods. Readers of this book will be exposed to a unified framework for designing and analyzing spectral algorithms for a variety of problems, including in particular high-order differential equations and problems in unbounded domains. The book contains a large

Shen, Jie; Wang, Li-Lian

2011-01-01

370

Simultaneous Spectral Temporal Adaptive Raman Spectrometer - SSTARS  

Science.gov (United States)

Raman spectroscopy is a prime candidate for the next generation of planetary instruments, as it addresses the primary goal of mineralogical analysis, which is structure and composition. However, large fluorescence return from many mineral samples under visible light excitation can render Raman spectra unattainable. Using the described approach, Raman and fluorescence, which occur on different time scales, can be simultaneously obtained from mineral samples using a compact instrument in a planetary environment. This new approach is taken based on the use of time-resolved spectroscopy for removing the fluorescence background from Raman spectra in the laboratory. In the SSTARS instrument, a visible excitation source (a green, pulsed laser) is used to generate Raman and fluorescence signals in a mineral sample. A spectral notch filter eliminates the directly reflected beam. A grating then disperses the signal spectrally, and a streak camera provides temporal resolution. The output of the streak camera is imaged on the CCD (charge-coupled device), and the data are read out electronically. By adjusting the sweep speed of the streak camera, anywhere from picoseconds to milliseconds, it is possible to resolve Raman spectra from numerous fluorescence spectra in the same sample. The key features of SSTARS include a compact streak tube capable of picosecond time resolution for collection of simultaneous spectral and temporal information, adaptive streak tube electronics that can rapidly change from one sweep rate to another over ranges of picoseconds to milliseconds, enabling collection of both Raman and fluorescence signatures versus time and wavelength, and Synchroscan integration that allows for a compact, low-power laser without compromising ultimate sensitivity.

Blacksberg, Jordana

2010-01-01

371

Development of a spectral break in the nonthermal emission of AO 0235+164  

Science.gov (United States)

Results are reported for braod-band photometry of the BL Lac object AO 0235+164 carried out over the spectral range from 0.36 to 3.5 microns in December 1975 and in October and November 1976. It is found that the continuum of this object steepened at visible wavelengths between December 1975 and October 1976, but maintained a relatively constant slope in the near-IR despite a factor-of-ten decrease in flux from the maximum level. Visible-wavelength data are cited which appear to suggest that the steepening of the visible spectrum occurred in less than 300 days, while the near-IR level may have been nearly constant. It is shown that the observed change in the spectral shape of the visible-wavelength continuum cannot be explained in terms of a 'composite' model consisting of an unchanging galaxy and a varying nonthermal source with constant spectral index. Two other general classes of models are considered: intrinsic variability and extrinsic modulation.

Odell, S. L.; Puschell, J. J.; Stein, W. A.; Warner, J. W.

1977-01-01

372

Broad spectral photonic crystal fiber surface enhanced Raman scattering probe  

Science.gov (United States)

A broad spectral surface enhanced Raman scattering sensor is developed using the solid core holey photonic crystal fiber with silver nanoparticles cluster. This SERS probe offers an operational excitation wavelength range overlaying visible light and near infrared light. The PCF SERS sensing is demonstrated in the detection of the 4-Mercaptobenzoic acid (10-6 M) solution with 514.5 and 785 nm excitation. In this structure of PCF sensor, the related analysis shows that leakage modes also make an important contribution in the SERS activity not only by the evanescent field way.

Xie, Z.; Lu, Y.; Wei, H.; Yan, J.; Wang, P.; Ming, H.

2009-06-01

373

Polarization gratings for visible and near-infrared astronomy  

Science.gov (United States)

We report on the development of polarization gratings that can be used for polarimetry and/or high throughput broadband spectroscopy in astronomy. Polarization gratings are able to overcome fundamental limitations on the diffraction efficiency of conventional gratings to provide near 100% diffraction efficiency over a broad bandwidth. The broad spectral coverage of these devices will be useful for observations of gamma-ray bursts and supernovae of unknown the redshift, where spectral features may fall over a range of wavelengths. As a spectropolarimeter a polarization grating would be ideal, for example, for the study of dusts and hazes, whose polarimetric properties vary with wavelength. We present the results of a series of laboratory measurements of the diffraction efficiency and modulation efficiency of a prototype grating designed for operation from 500 to 900 nm. We find that the grating is able to achieve greater than 90% diffraction efficiency from 500 to 850 nm and modulate incident circular polarized light with an efficiency of ~ 99%. Our future plans include on-sky testing at a small local telescope, with an eventual goal of incorporating a polarization grating into the design of a microshutter array- based multi-object visible/NIR spectrograph for a 10m class facility.

Millar-Blanchaer, Max; Moon, Dae-Sik; Graham, James R.; Escuti, Michael

2014-07-01

374

Visible Genotype Sensor Array  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A visible sensor array system for simultaneous multiple SNP genotyping has been developed using a new plastic base with specific surface chemistry. Discrimination of SNP alleles is carried out by an allele-specific extension reaction using immobilized oligonucleotide primers. The 3’-ends of oligonucleotide primers are modified with a locked nucleic acid to enhance their efficiency in allelic discrimination. Biotin-dUTPs included in the reaction mixture are selectively incorporate...

Takashi Imai; Mayumi Iwakawa; Kenichi Ishikawa; Atsuko Ishikawa; Izumi Matsumoto; Yoshimi Ohtsuka; Tomo Suga; Yuichi Michikawa

2008-01-01

375

Visible Genotype Sensor Array  

Directory of Open Access Journals (Sweden)

Full Text Available A visible sensor array system for simultaneous multiple SNP genotyping has been developed using a new plastic base with specific surface chemistry. Discrimination of SNP alleles is carried out by an allele-specific extension reaction using immobilized oligonucleotide primers. The 3’-ends of oligonucleotide primers are modified with a locked nucleic acid to enhance their efficiency in allelic discrimination. Biotin-dUTPs included in the reaction mixture are selectively incorporated into extending primer sequences and are utilized as tags for alkaline phosphatase-mediated precipitation of colored chemical substrates onto the surface of the plastic base. The visible precipitates allow immediate inspection of typing results by the naked eye and easy recording by a digital camera equipped on a commercial mobile phone. Up to four individuals can be analyzed on a single sensor array and multiple sensor arrays can be handled in a single operation. All of the reactions can be performed within one hour using conventional laboratory instruments. This visible genotype sensor array is suitable for “focused genomics” that follows “comprehensive genomics”.

Takashi Imai

2008-04-01

376

Spatial and spectral performance of a chromotomosynthetic hyperspectral imaging system.  

Science.gov (United States)

The spatial and spectral resolutions achievable by a prototype rotating prism chromotomosynthetic imaging (CTI) system operating in the visible spectrum are described. The instrument creates hyperspectral imagery by collecting a set of 2D images with each spectrally projected at a different rotation angle of the prism. Mathematical reconstruction techniques that have been well tested in the field of medical physics are used to reconstruct the data to produce the 3D hyperspectral image. The instrument operates with a 100 mm focusing lens in the spectral range of 400-900 nm with a field of view of 71.6 mrad and angular resolution of 0.8-1.6 ?rad. The spectral resolution is 0.6 nm at the shortest wavelengths, degrading to over 10 nm at the longest wavelengths. Measurements using a point-like target show that performance is limited by chromatic aberration. The system model is slightly inaccurate due to poor estimation of detector spatial resolution, this is corrected based on results improving model performance. As with traditional dispersion technology, calibration of the transformed wavelength axis is required, though with this technology calibration improves both spectral and spatial resolution. While this prototype does not operate at high speeds, components exist which will allow for CTI systems to generate hyperspectral video imagery at rates greater than 100 Hz. PMID:22462909

Bostick, Randall L; Perram, Glen P

2012-03-01

377

Acquisition and visualization techniques for narrow spectral color imaging.  

Science.gov (United States)

This paper introduces a new approach in narrow-band imaging (NBI). Existing NBI techniques generate images by selecting discrete bands over the full visible spectrum or an even wider spectral range. In contrast, here we perform the sampling with filters covering a tight spectral window. This image acquisition method, named narrow spectral imaging, can be particularly useful when optical information is only available within a narrow spectral window, such as in the case of deep-water transmittance, which constitutes the principal motivation of this work. In this study we demonstrate the potential of the proposed photographic technique on nonunderwater scenes recorded under controlled conditions. To this end three multilayer narrow bandpass filters were employed, which transmit at 440, 456, and 470 nm bluish wavelengths, respectively. Since the differences among the images captured in such a narrow spectral window can be extremely small, both image acquisition and visualization require a novel approach. First, high-bit-depth images were acquired with multilayer narrow-band filters either placed in front of the illumination or mounted on the camera lens. Second, a color-mapping method is proposed, using which the input data can be transformed onto the entire display color gamut with a continuous and perceptually nearly uniform mapping, while ensuring optimally high information content for human perception. PMID:24323091

Neumann, László; García, Rafael; Basa, János; Hegedüs, Ramón

2013-06-01

378

Visible Spectrum Incandescent Selective Emitter  

Energy Technology Data Exchange (ETDEWEB)

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.

Sonsight Inc.

2004-04-30

379

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.

380

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

Directory of Open Access Journals (Sweden)

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.

Meng Kong

2011-01-01

 
 
 
 
381

Correlated IR spectroscopy and visible light scattering measurements of mineral dust aerosol  

Science.gov (United States)

A combined infrared spectroscopy and visible light scattering study of the optical properties of quartz aerosol, a major component of atmospheric dust, is reported. Scattering phase function and polarization measurements for quartz dust at three visible wavelengths (470, 550, 660 nm) are compared with results from T-matrix theory simulations using a uniform spheroid model for particle shape. Aerosol size distributions were measured simultaneously with light scattering. Particle shape distributions were determined in two ways: (1) analysis of electron microscope images of the dust, and (2) spectral fitting of infrared resonance extinction features. Since the aerosol size and shape distributions were measured, experimental scattering data could be directly compared with T-matrix simulations with no adjustable parameters. ?2 analysis suggests that T-matrix simulations based on a uniform spheroid approximation can be used to model the optical properties of irregularly shaped dust particles in the accumulation mode size range, provided the particle shape distribution can be reliably determined. Particle shape distributions derived from electron microscope image analysis give poor fits, indicating that two-dimensional images may not give an accurate representation of the shape distribution for three-dimensional particles. However, simulations based on particle shape models inferred from IR spectral analysis give excellent fits to the experimental data. Our work suggests that correlated IR spectral and visible light scattering measurements, together with the use of theoretical light scattering models, may offer a more accurate method for characterizing atmospheric dust loading, and aerosol composition, size, and shape distributions, which are of great importance in climate modeling.

Meland, B.; Kleiber, P. D.; Grassian, V. H.; Young, M. A.

2010-10-01

382

Spectral Analysis  

CERN Document Server

G. Bottaro: Quelques resultats d'analyse spectrale pour des operateurs differentiels a coefficients constants sur des domaines non bornes.- L. Garding: Eigenfuction expansions.- C. Goulaouic: Valeurs propres de problemes aux limites irreguliers: applications.- G. Grubb: Essential spectra of elliptic systems on compact manifolds.- J.Cl. Guillot: Quelques resultats recents en Scattering.- N. Schechter: Theory of perturbations of partial differential operators.- C.H. Wilcox: Spectral analysis of the Laplacian with a discontinuous coefficient.

Cecconi, Jaures

2011-01-01

383

Multi-spectral mapping of in vivo skin hemoglobin and melanin  

Science.gov (United States)

The multi-spectral imaging technique has been used for distant mapping of in-vivo skin chromophores by analyzing spectral data at each reflected image pixel and constructing 2-D maps of the relative concentrations of oxy-/deoxyhemoglobin and melanin. Instead of using a broad visible-NIR spectral range, this study focuses on narrowed spectral band 500-700 nm, so speeding-up the signal processing procedure. Regression analysis confirmed that superposition of three Gaussians is optimal analytic approximation for the oxy-hemoglobin absorption tabular spectrum in this spectral band, while superposition of two Gaussians fits well for deoxy-hemoglobin absorption and exponential function - for melanin absorption. The proposed approach was clinically tested for three types of in-vivo skin provocations - ultraviolet irradiance, chemical reaction with vinegar essence and finger arterial occlusion. Spectral range 500-700 nm provided better sensitivity to oxy-hemoglobin changes and higher response stability to melanin than two reduced ranges 500-600 nm and 530-620 nm.

Jakovels, Dainis; Spigulis, Janis; Saknite, Inga

2010-04-01

384

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

385

Results and lessons from a decade of Terra MODIS on-orbit spectral characterization  

Science.gov (United States)

Since launch in 1999, the NASA EOS Terra MODIS has successfully operated for more than a decade. MODIS acquires data in 36 spectral bands with wavelengths ranging from visible (VIS) to long-wave infrared (LWIR) and at three nadir spatial resolutions: 250m for 2 bands, 500m for 5 bands, and 1km for 29 bands. In addition to its on-board calibrators (OBC), designed for sensor radiometric calibration and characterization, MODIS was built with a unique device called the spectro-radiometric calibration assembly (SRCA), which can be configured into three different modes: radiometric, spatial, and spectral. When it is operated in the spectral mode, the SRCA can monitor changes in sensor spectral performance for the VIS and near-infrared (NIR) spectral bands. For more than 10 years, the SRCA operations have continued to provide valuable information for Terra MODIS on-orbit spectral performance. This paper briefly describes Terra MODIS SRCA on-orbit operations and calibration activities and presents results derived from its decade-long spectral characterization, including changes in the VIS and NIR spectral bands center wavelengths (CW) and bandwidths (BW). It demonstrates that the SRCA on-orbit wavelength calibration capability remains satisfactory. For most spectral bands, the changes in CW and BW are less than 0.5 nm and 1.0 nm, respectively. As expected, results and lessons from Terra MODIS on-orbit spectral characterization have and will continue to benefit the operation and calibration of its successor, Aqua MODIS, and the development of future missions and sensors, which have stringent requirements on sensor spectral performance.

Xiong, Xiaoxiong; Choi, Taeyoung; Che, Nianzeng; Wang, Zhipeng; Dodd, Jennifer; Xie, Yong; Barnes, William

2010-10-01

386

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)

387

Block Numerical Ranges  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The block numerical range (BNR) of a block operator matrix is a generalization of the numerical range of an operator acting on a Hilbert space. Main topics of this thesis are block diagonalizability of a block operator matrix if its BNR consists of the maximal number of connected components and spectral properties of corners of BNRs of block operator matrices and block operator functions.

Wagenhofer, Markus

2007-01-01

388

Development of short-wavelength near-infrared spectral imaging for grain color classification  

Science.gov (United States)

Color class of wheat is an important attribute for the identification of cultivars and the marketing of wheat, but is not always easy to measure in the visible spectral range because of variation in vitreosity and surface structure of the kernels. This work examines whether short-wavelength near IR imaging in the range 632-1098 nm can be used to distinguish different cultivars. The spectral characteristics of six hard white winter and hard red spring wheats were first studied by bulk-sample SW-NIR reflectance spectroscopy using regression analysis to select appropriate wavelengths and sets of wavelengths. Prediction of percent red wheat was better if C-H or O-H vibrational overtones were included in the models in addition to the tail from the visible chromophore absorbance, apparently because the vibrational bands make it possible to normalize the color measurement to the dry matter content of the samples. Next, a reflectance spectral image of 640 X 480 spatial pixels and 11 wavelengths was acquired for a mixture of the two contrasting wheat samples using a CCD camera and a liquid crystal tunable filter. The cultivars were distinguished in the image of principal component (PC) score number two that was calculated from the spectral image. The discrimination is due to the tail from the absorbance band that peaks in the visible. PC images 3 and 6 seem to arise mainly from O-H and C-H bands, respectively, and it is speculated that these spectral features will be important for generating multivariate models to predict the color class of grain. It is shown that the contrast between the red-wheat, white- wheat and background can be increased by applying histogram equalization and segmentation of the kernels in the images.

Archibald, Douglas D.; Thai, Chi N.; Dowell, Floyd E.

1999-01-01

389

Optical Conductivity of Graphene in the THz Frequency Range  

International Nuclear Information System (INIS)

Full text: Since its discovery in 2004, graphene - planar, hexagonal arrangements of carbon atoms - attracted much attention in different scientific fields. This is not only due to the fact, that truly two-dimensional crystalline systems like graphene were supposed not to exist, but mainly due to the unique electronic properties of this material. The crystal structure of graphene consists of two equivalent sublattices. Quantum mechanical hopping of electrons between these sublattices leads to the formation of two energy bands that intersect at the points K and K'. Around these crossing points, the electron dispersion relation is linear and gapless in contrast to conventional metals and semiconductors. This fact is expected to result in strong interaction between graphene and terahertz radiation under certain conditions, and thus makes graphene a very interesting material for the terahertz spectral range. In this context, the optical conductivity is a key property of graphene. While the optical conductivity of graphene is constant for the visible spectral region, it is expected to show strong deviation from this behaviour in the THz frequency region. This is due to the fact that interband transitions dominate in the visible range whereas, below the mid-infrared range, intraband transitions are dominant. We present an experimental approach to measure the optical conductivity of a graphene monolayer by means of THz time-domain-spectroscopy involving an on-chip coplanar waveguide structure for generation and detection of THz pulses. (author)

390

On spectropolarimetric measurements with visible lines  

CERN Document Server

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...

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

2010-01-01

391

Spectral Ranking  

CERN Document Server

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.

Vigna, Sebastiano

2009-01-01

392

The spectral absorption by aerosols from 350-2500nm and its radiative forcing implications  

Science.gov (United States)

The absorption properties of aerosol particles are still one of the largest uncertainties on the aerosol forcing of the Climate. Global measurements of BC are not available and badly needed. In situ aerosol absorption measurements are often inaccurate, neglect some important properties, and usually cover a narrow spectral range missing significant absorption features. This work presents results of spectral measurements of aerosol absorption efficiency in a broad spectral range (350-2500nm) highlighting some characteristics of BC and other aerosol absorbers. Implications of these results on the aerosol radiative forcing over different surface types will also be discussed. It is well known that BC is the main absorbing material in atmospheric aerosol but it is not the only one. Soil dust absorbs light in the UV and visible, some organic materials absorb in the UV, and there are recent evidences that some organic materials may also absorb light in longer wavelengths. The absorption spectral dependence by aerosol particles is directly influenced by the chemical composition (refractive indices), the relative size of the absorbers versus the wavelength, and by mixtures between the absorbing and non-absorbing materials. Our spectral absorption measurements covering a broad spectral range (350-2500nm) produce enough information to separate these effects determining the absorption contribution by the different aerosol constituents and the identifying the potential mixture between fine and coarse particles. Results from spectral absorption measurements will be presented for Brazil (Sao Paulo and the Amazon), Mexico, China, UAE, Israel, Bodele, and the US. These results were used on radiative forcing calculations for these aerosols and on the determination of their potential to heat the atmospheric column and affect cloud formation and cloud life time. Our calculations show that in many circumstances, the often neglected wide spectral range, and the absorption by coarse mode particles are essential for an accurate determination of the aerosol forcing.

Martins, J. V.; Chaudhry, Z.; Artaxo, P.

2007-12-01

393

Distance and Visibility: Two Systems in Hausa Deixis  

Directory of Open Access Journals (Sweden)

Full Text Available The current standard account of Hausa deixis claims that Hausa has a linear person-based system with the following four locative adverbs and their interpretations: nân 'here', nan 'there near you', cân 'there away from you and me', and can 'over there away from you and me'. This paper shows that in fact one may need two separate deictic systems for Hausa to account for all relevant data. The first system is based on distance with a primary proximal vs. distal contrast. The distance system however also embeds a person subsystem, with one adverb in particular referring to the hearer (second person position. The second deictic system in Hausa is based on visibility, with a primary contrast between an area comfortably visible and an area visible only with some difficulties. Indeed, in the visibility system, five adverbs range the entire visible area in front of the speaker, from the foreground up to the extreme visible area at the horizon.

Abdoulaye, Mahamane L.

2008-01-01

394

Visible light emission due to resonant CO_{2} excitation of dental hard tissue  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Visible light emission of dental hard substances excited by high-power infrared pulses of a tunable TEA CO2 laser has been investigated. A clear correlation between observed visible light emission, plasma formation as well as ablation of dental hard tissue has been demonstrated. Both, the highly nonlinear infrared to visible upconversion process and the ablation efficiency show a sharp spectral resonance close to a vibrational mode of PO4 at 1090 cm-1 in dental enamel and dentin. The influenc...

Lohner, Andrea; Huber, Michael; Ganichev, Sergey; Prettl, Wilhelm; Niederdellmann, Herbert

2000-01-01

395

Results of first experiments with using of a visible-near IR endoscope on the T-10 tokamak  

International Nuclear Information System (INIS)

The work is devoted to the design and parameters of a visible - near IR endoscope, that has been recently installed on the T-10 tokamak. The arrangement of the instrument enables tangential observation of the cross-section, where the carbon limiters of the machine are situated. With use of the endoscope the following measurements of the space distribution of radiation intensity at different spectral regions are carried out: at the H?, H?, and CVI (529 nm) lines, at the Bremsstrahlung window 523,0 to 524,2 nm, at the range of 700 ± 5 nm (hydrogen molecular lines), and at the near IR region

396

Near infrared and visible luminescence of U{sup 3+}-doped PbCl{sub 2} single crystals  

Energy Technology Data Exchange (ETDEWEB)

Good optical quality U{sup 3+}-doped PbCl{sub 2} single crystals of the composition Pb{sub 0.99}U{sub 0.01}Cl{sub 2} 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 5f{sup 2}6d{sup 1} bands. The lifetimes of the emitting levels in the visible and near infrared region are given.

Sobczyk, Marcin [Faculty of Chemistry, University of Wroclaw, ul. F. Joliot-Curie 14, 50-383 Wroclaw (Poland); Drozdzynski, Janusz [Faculty of Chemistry, University of Wroclaw, ul. F. Joliot-Curie 14, 50-383 Wroclaw (Poland)], E-mail: jd@wchuwr.chem.uni.wroc.pl; Lisiecki, Radoslaw; Ryba-Romanowski, Witold [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland)

2008-02-15

397

Spectral Experiments+  

CERN Document Server

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.

Rivin, Igor

2014-01-01

398

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

CERN Document Server

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,...

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

399

Spectral analysis by correlation  

International Nuclear Information System (INIS)

The spectral density of a signal, which represents its power distribution along the frequency axis, is a function which is of great importance, finding many uses in all fields concerned with the processing of the signal (process identification, vibrational analysis, etc...). Amongst all the possible methods for calculating this function, the correlation method (correlation function calculation + Fourier transformation) is the most promising, mainly because of its simplicity and of the results it yields. The study carried out here will lead to the construction of an apparatus which, coupled with a correlator, will constitute a set of equipment for spectral analysis in real time covering the frequency range 0 to 5 MHz. (author)