WorldWideScience
1

A New and Inexpensive Pyranometer for the Visible Spectral Range  

Directory of Open Access Journals (Sweden)

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

Miguel A. Martínez

2009-06-01

2

Scattering in remote sensing in the visible and microwave spectral range and in traffic control  

OpenAIRE

The treatment of scattering processes in remote sensing for interpretation of satellite data is demonstrated in the visible and microwave spectral range comparing the two spectral ranges. Analogies and distinctions in the treatment of the scattering processes are shown. Based on this cognition an approach for traffic simulation is outlined. Simulating the traffic of a part of a city, a whole city or a larger area in an acceptable time is one of the tasks in recent traffic research. One possib...

Bo?ttger, U.; Ku?hne, R.; -u Thiessenhusene, K.

2003-01-01

3

High-gain DC-mode operated Gaseous Photomultipliers for the visible spectral range  

OpenAIRE

We shortly describe recent progress in photon detectors combining bi-alkali photocathodes and cascaded patterned gas-avalanche electron multipliers. It permitted the development and the first feasibility demonstration of high-gain gaseous photomultipliers sensitive in the visible spectral range, operated in DC mode with single-photon sensitivity.

Lyashenko, A.; Breskin, A.; Chechik, R.; Amaro, F. D.; Veloso, J.; Santos, J. M. F. Dos

2008-01-01

4

Spectroscopy of fullerenes, fulleranes and PAHs in the UV, visible and near infrared spectral range  

CERN Document Server

The spectra of fullerenes C60 and C70, higher fullerenes C76, C78 and C84 and hydrogenated fullerenes (fulleranes) were studied in laboratory in the UV and in the visible spectral range and could be used for searching and recognizing these molecules in space. Furthermore, the radical cation spectra of all the mentioned fullerene series and also of a series of large and very large polycyclic aromatic hydrocarbons (PAHs) were generated in laboratory and studied in the near infrared spectral range.

Cataldo, F; Manchado, A; Iglesias-Groth, S

2013-01-01

5

Airborne hyperspectral imaging in the visible-to-mid wave infrared spectral range by fusing three spectral sensors  

Science.gov (United States)

Airborne hyperspectral imaging is widely used for remote sensing of environment. The choice of spectral region usually depends on the availability and cost of the sensor. Visible-to-near infrared (400-1100 nm) spectral range corresponds to spectral sensitivity of relatively cheap Si detectors therefore it is the most commonly used. The implementation of shortwave infrared (1100-3000 nm) requires more expensive solutions, but can provide valuable information about the composition of the substance. Mid wave infrared (3000-8000 nm) is rarely used for civilian applications, but it provides information on the thermal emission of materials. The fusion of different sensors allows spectral analysis of a wider spectral range combining and improving already existing algorithms for the analysis of chemical content and classification. Here we introduce our Airborne Surveillance and Environmental Monitoring System (ARSENAL) that was developed by fusing seven sensors. The first test results from the fusion of three hyperspectral imaging sensors in the visible-to-mid wave infrared (365-5000 nm) are demonstrated. Principal component analysis (PCA) is applied to test correlation between principal components (PCs) and common vegetation indices.

Jakovels, Dainis; Filipovs, Jevgenijs; Erinš, Gatis; Taskovs, Juris

2014-10-01

6

Scattering in remote sensing in the visible and microwave spectral range and in traffic control  

Science.gov (United States)

The treatment of scattering processes in remote sensing for interpretation of satellite data is demonstrated in the visible and microwave spectral range comparing the two spectral ranges. Analogies and distinctions in the treatment of the scattering processes are shown. Based on this cognition an approach for traffic simulation is outlined. Simulating the traffic of a part of a city, a whole city or a larger area in an acceptable time is one of the tasks in recent traffic research. One possible approach is the areal treatment of the road network. That means that single streets are not resolved but are introduced into simulations only by parameters that correspond to a specific traffic area resistance. The aim of this work is to outline such a possibility using experiences obtained from the theory of radiative transport to simulate scattering processes and applying them to the very complex system of traffic simulation.

Böttger, U.; Kühne, R.; Thiessenhusene, K.-U.

2003-05-01

7

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

OpenAIRE

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

8

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

9

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

10

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)

11

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

OpenAIRE

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...

Bo?ttger, U.; Preusker, R.

2006-01-01

12

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-05-15

13

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

14

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

Science.gov (United States)

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

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

2009-07-01

15

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

International Nuclear Information System (INIS)

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

16

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

17

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

OpenAIRE

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...

Mieruch, S.; Noe?l, S.; Bovensmann, H.; Burrows, J. P.

2007-01-01

18

Lasing in the UV, IR and visible spectral ranges in a runaway-electron-preionised diffuse dischrage  

Energy Technology Data Exchange (ETDEWEB)

Lasers on the mixtures of inert gases, H{sub 2}, D{sub 2}, and nitrogen with NF{sub 3} and (or) SF{sub 6} are studied under pumping by the volume (diffusive) discharge formed in a nonuniform electric field due to runaway-electron preionisation. Generation in the IR, visible and UV spectral ranges is obtained on atomic transitions of neon ({lambda} = 585.3 nm), argon (750.3 nm) and fluorine (712.8 and 731.1 nm), and on molecular transitions of N2 (337.1 nm), XeF * (351 and 353 nm), HF (2.8 - 3.2 {mu}m) and DF (3.8 - 4.2 {mu}m). It is shown that in N{sub 2} - SF{sub 6}, H{sub 2} - SF{sub 6} and D{sub 2} - SF{sub 6} mixtures the generation efficiency approaches the limiting values. (lasers)

Vil' tovskii, P O; Lomaev, Mikhail I; Panchenko, Aleksei N; Panchenko, N A; Rybka, D V; Tarasenko, Viktor F [Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)

2013-07-31

19

Ground-based observations of the corona in the visible and NIR spectral ranges  

Science.gov (United States)

Since late 1993 we have been using a mirror coronagraph on Pic du Midi (PICO) to observe the solar emission corona in several spectral lines of (FE-X), (FE-XIII), and (FE-XIV). For good meteorological conditions the diffuse corona and coronal holes in between can be seen out to 1.2 solar mass for sun center. Active regions can be mapped to bond 1.5 solar mass in the green and infrared lines. Recent observations of PICO are presented.

Epple, Alexander; Schwenn, Rainer

1995-01-01

20

Optical Characterization of Organic Light-Emitting Thin Films in the Ultraviolet and Visible Spectral Ranges  

CERN Document Server

The spectrophotometric characterization of high efficiency, optically-active samples such as light-emitting organic bulks and thin films can be problematic because their broad-band luminescence is detected together with the monochromatic transmitted and reflected signals, hence perturbing measurements of optical transmittance and reflectance at wavelengths within the photoexcitation band. As a matter of fact, most commercial spectrophotometers apply spectral filtering before the light beam reaches the sample, not after it. In this Report, we introduce and discuss the method we have developed to correct photometric spectra that are perturbed by photoluminescence.

Montereali, R M; Nichelatti, E; Di Pompeo, F; Segreto, E; Canci, N; Cavanna, F

2012-01-01

21

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

S. Mieruch

2008-02-01

22

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

23

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

24

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

Energy Technology Data Exchange (ETDEWEB)

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

Mezdrogina, M. M., E-mail: margaret.m@mail.ioffe.ru; Kostina, L. S.; Beliakova, E. I.; Kuzmin, R. V. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2013-09-15

25

Super-transmission of light through subwavelength annular aperture arrays in metallic films: Spectral analysis and near-field optical images in the visible range  

Science.gov (United States)

This paper presents experimental studies of the enhanced light transmission through metallic films pierced by subwavelength annular apertures. Two different methods (e-beam lithography and focused ion beam) have been used to build the nano-structures. We have experimentally recorded their far-field spectral response in the visible range and the optical near-field above the nano-structures when they are excited at 633 nm. The spectral response exhibits a transmission peak at 700 nm with maximum efficiency around 16%. The near-field exhibits a characteristic two-lobe structure just above the aperture. Finite difference time domain (FDTD) simulations reproduce quite well the experimental results.

Poujet, Y.; Roussey, M.; Salvi, J.; Baida, F. I.; Van Labeke, D.; Perentes, A.; Santschi, C.; Hoffmann, P.

2006-02-01

26

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

International Nuclear Information System (INIS)

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

27

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

Science.gov (United States)

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

Akbari, R.; Major, A.

2013-03-01

28

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

OpenAIRE

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 mu...

Breskin, A.; Mo?rmann, D.; Lyashenko, A.; Chechik, R.; Amaro, F. D.; Maia, J. M.; Veloso, J. F. C. A.; Santos, J. M. F. Dos

2005-01-01

29

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 aerosol radiative properties is a crucial challenge for climate change studies. This study aims at providing a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW) solar spectrum. For this purpose, long-term data sets of aerosol properties from six AERONET stations located in the Iberian Peninsula (southwestern Europe) have been analyzed in terms of climatological characterization and inter-annual changes. Aerosol information was used as input for the libRadtran model in order to determine the aerosol radiative effect (ARE) 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, yearly aerosol radiative effects in the different spectral ranges were found to be -1.1 < AREUV < -0.7, -5.7 < AREVIS < -3.5, -2.6 < ARENIR < -1.6, and -8.8 < ARESW < -5.7 (in W m-2). Monthly means of ARE showed a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE), ARE per unit of aerosol optical depth, has also been evaluated in the four spectral ranges. AFE exhibited a dependence on single scattering albedo as well as a weaker one on the 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 varied with the aerosol types. The predominant aerosol size determined the fractions AFEVIS/AFESW and AFENIR/AFESW. The AFEVIS was the dominant contributor for all aerosol types, although non-absorbing large particles caused more even contribution of VIS and NIR intervals. The AFEUV / AFESW ratio showed a higher value in the case of absorbing fine particles.

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

2014-12-01

30

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

31

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

International Nuclear Information System (INIS)

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

32

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

Energy Technology Data Exchange (ETDEWEB)

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

McCarthy, K. J.; Zurro, B.; Baciero, A.

2001-07-01

33

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

34

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

35

Calculation of Spectral Darkening and Visibility Functions for Solar Oscillations  

CERN Document Server

Calculations of spectral darkening and visibility functions for the brightness oscillations of the Sun resulting from global solar oscillations are presented. This has been done for a broad range of the visible and infrared continuum spectrum. The procedure for the calculations of these functions includes the numerical computation of depth-dependent derivatives of the opacity caused by p modes in the photosphere. A radiative-transport code was used for this purpose to get the disturbances of the opacities from temperature and density fluctuations. The visibility and darkening functions are obtained for adiabatic oscillations under the assumption that the temperature disturbances are proportional to the undisturbed temperature of the photosphere. The latter assumption is the only way to explore any opacity effects since the eigenfunctions of p-mode oscillations have not been obtained so far. This investigation reveals that opacity effects have to be taken into account because they dominate the violet and infra...

Nutto, C; Zhugzhda, Y; Bruls, J; Von der Lühe, O

2008-01-01

36

Globally integrated measurements of the Earth's visible spectral albedo  

CERN Document Server

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

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

2005-01-01

37

[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

38

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

39

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

Science.gov (United States)

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

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

2014-06-01

40

Visible and Near Infrared Fluorescence Spectral Flow Cytometry  

OpenAIRE

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-derive...

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

2012-01-01

41

[Research on LC-based spectral imaging system for visible band].  

Science.gov (United States)

LC-based tunable filter with large aperture has been developed utilizing the effect of electric controlled birefringence. Spectral test indicated that this filter can operate in the visible band with an average 20 nm FWHM. A small scale spectral imaging system was established based on this tunable filter. Spectral imaging experiments on a certain number of samples show that this system can be tuned continuously with random-access selection of any wavelength, and has a higher level of resolving power in respect of both imaging and spectral tuning in the visible band, which has a brilliant application potentiality in biology, iatrology, environmental protection, resource detection through hyper-spectral imaging or ultra-spectral imaging. PMID:22250532

Shen, Zhi-Xue; Li, Jian-Feng; Zhang, Da-Yong; Wu, Jun; Long, Yan; Huang, Li-Xian; Liu, Hai-Tao; Luo, Yong-Quan; Luo, Fei; Zhang, Cui-Juan; Yang, Jun-Jie

2011-10-01

42

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

43

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

Science.gov (United States)

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

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

2015-01-01

44

Studying soil properties using visible and near infrared spectral analysis  

Science.gov (United States)

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

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

2009-04-01

45

Studies of the ECR plasma in the visible light range  

International Nuclear Information System (INIS)

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

46

Spectrally-resolved measurements of aerosol extinction at ultraviolet and visible wavelengths  

Science.gov (United States)

Aerosols play an important role in the Earth's radiative budget. Aerosol extinction includes both the scattering and absorption of light, and these vary with wavelength, aerosol diameter, and aerosol composition. Historically, aerosol absorption has been measured using filter-based or extraction methods that are prone to artifacts. There have been few investigations of ambient aerosol optical properties at the blue end of the visible spectrum and into the ultraviolet. Brown carbon is particularly important in this spectral region, because it both absorbs and scatters light, and encompasses a large and variable group of organic compounds from biomass burning and secondary organic aerosol. We have developed a laboratory instrument that combines new, high-power LED light sources with high-finesse optical cavities to achieve sensitive measurements of aerosol optical extinction. This instrument contains two broadband channels, with spectral coverage from 360 - 390 nm and 385 - 420 nm. Using this instrument, we report aerosol extinction in the ultraviolet and near-visible spectral region as a function of chemical composition and structure. We have measured the extinction cross-sections between 360 - 420 nm with 0.5 nm resolution using different sizes and concentrations of polystyrene latex spheres, ammonium sulfate, and Suwannee River fulvic acid. Fitting the real and imaginary part of the refractive index allows the absorption and scattering to be determined.

Flores, M.; Washenfelder, R. A.; Brock, C. A.; Brown, S. S.; Rudich, Y.

2012-12-01

47

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

48

Stark widths and shifts of Ar II spectral lines in visible part of spectrum  

International Nuclear Information System (INIS)

Stark widths and shifts of 13 Ar II spectral lines in the visible part of spectrum were measured. Spectral lines were emitted from pulsed wall stabilized Ar arc plasma under atmospheric pressure. Profiles were recorded at plasma electron densities of 1.3×1023 m?3 and 1.6×1023 m?3 and plasma electron temperatures of 13,400 K and 14,200 K respectively. Obtained results are compared with other experimental results as well as with theoretical values. The analysis of the experimental and theoretical data is given as well. -- Highlights: •Precise and reliable measurements of Stark parameters. •The use of these data for plasma diagnostic purposes. •Comparisons of obtained data with available experimental and theoretical values

49

A stereo range computation method using thermal infrared and visible cameras  

Science.gov (United States)

Binocular stereo vision can provide geometric position information of the target, which enables one to track the moving object precisely. Although visible images are full of details of geometry and texture, it is difficult to detect moving objects in poor visibility. Appropriate fusion of infrared and visible images can combine the complementary information and obtain a better description of the scene, which will help in target detection and target localization. Considering the physical differences between thermal infrared cameras and visible cameras, a stereo ranging method in parallel camera configuration is proposed in this paper. The rotation center of a pan-tilt device is used as the origin of the coordinate system in the method. It could not only locate the object in poor visibility, but also determine the parameters essential in range computation in practical work, which is very difficult in traditional calibration methods. Furthermore, the effect of the relative position of a certain target and reference points is analyzed. Experiments also proved the validity of the proposed method.

Chen, Wen; Cao, Li; Wu, Zijian; Huang, Shengguo

2014-01-01

50

Results of a slant range visibility field experiment with the modified DFVLR-minilidar  

Science.gov (United States)

The modified minilidar was used for a slant visual range experiment. The measured lidar visibility values were compared with: (1) in situ measurements from different heights above ground, using an instrumented tower; and (2) a slant installed transmissometer. The possibilities of the lidar two point method for practical application are shown.

Werner, C.

1981-01-01

51

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

52

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

Science.gov (United States)

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

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

2013-02-01

53

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

International Nuclear Information System (INIS)

Intense visible lines from Be-like oxygen impurity are routinely observed in the Aditya tokamak. The spatial profile of brightness of a Be-like oxygen spectral line (2p3p 3D3–2p3d 3F4) at 650.024 nm is used to investigate oxygen impurity transport in typical discharges of the Aditya tokamak. A 1.0 m multi-track spectrometer (Czerny–Turner) capable of simultaneous measurements from eight lines of sight is used to obtain the radial profile of brightness of O4+ spectral emission. The emissivity profile of O4+ spectral emission is obtained from the spatial profile of brightness using an Abel-like matrix inversion. The oxygen transport coefficients are determined by reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional empirical impurity transport code, STRAHL. Much higher values of the diffusion coefficient compared with the neo-classical values are observed in both the high magnetic field edge region (Dinboardmax?30 m2 s-1) and the low magnetic field edge region (Doutboardmax?45 m2 s-1) of typical Aditya ohmic plasmas, which seems to be due to fluctuation-induced transport. The diffusion coefficient at the limiter radius in the low-field (outboard) region is typically ? twice as high as that at the limiter radius in the high-field (inboard) region. (paper) (inboard) region. (paper)

54

Diamond photonic crystals for the IR spectral range.  

Science.gov (United States)

2D photonic crystals formed inside monocrystalline diamond to operate in the IR spectral range are reported. The photonic structures consisting of 150-?m-long graphitized wires arranged in a square matrix with a period of 4 ?m were produced by laser writing with ultrashort pulses. Transmittance spectra (?=1-14???m) measured for the structures with increasing thickness demonstrate the occurrence of few minima being different for TM and TE polarization modes. Complex refraction index of the laser-modified material was evaluated for the first time in order to be used in computer simulation of the structures. PMID:25503041

Kononenko, T V; Dyachenko, P N; Konov, V I

2014-12-15

55

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

56

Experimental Demonstration of Non-Resonant Hyperlens in the Visible Range  

CERN Document Server

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

Sun, Jingbo; Litchinitser, Natalia M

2014-01-01

57

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

OpenAIRE

We discuss propagation effects in realistic, transparent, metallo-dielectric photonic band gap structures in the context of negative refraction and super-resolution in the visible and near infrared ranges. In the resonance tunneling regime, we find that for transverse-magnetic incident polarization, field localization effects contribute to a waveguiding phenomenon that makes it possible for the light to remain confined within a small fraction of a wavelength, without any tra...

Ceglia, D.; Vincenti, M. A.; Cappeddu, M. G.; Centini, M.; Akozbek, N.; Dorazio, A.; Haus, J. W.; Bloemer, M. J.; Scalora, M.

2008-01-01

58

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

International Nuclear Information System (INIS)

Very recently Farhat et al (2011, Phys. Rev. B 84 235105) suggested that arrays of invisibility cloaks may find important applications in low-interference communication, noninvasive probing, sensing and communication networks and so on. We report on the first experimental realization of such an array of broadband invisibility cloaks that operates in the visible frequency range. The wavelength and angular dependences of the cloak array performance have been studied. (paper)

59

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

60

Airborne prototype instrument suite test flight of a low-light high-dynamic range imager and visible spectrometer  

Science.gov (United States)

The Airborne Sensors Initiative (ASI) at Ball Aerospace and Technologies Corp. (BATC) specializes in airborne demonstration of internally-developed instrument concepts and innovative remote sensing technologies. In December 2006, ASI flew an environmental remote sensing suite consisting of the Low Light Imager (LLI) and Prototype Airborne Visible Imaging Spectrometer (PAVIS), both of which are operated using a pushbroom approach. LLI is designed for nighttime or high dynamic range imaging. It is capable of yielding 10 7 dynamic range and offers quality images amid illumination extending from a 1/ 4 moon to full sunlight and with autonomous operation. PAVIS is an imaging spectrometer based on the Dyson design and exhibits a 200 nm spectral bandwidth tunable within 400 - 850 nm. Developed internally to demonstrate promising remote sensing capabilities, these small, low-mass and low-power instruments are prepared for aircraft flight and are currently being used in the field to acquire scientific data. The LLI/PAVIS instrument suite has been utilized to collect airborne urban and rural imagery, as well as spectral information about the Great Salt Lake area, western Colorado, and ancient lava flows in southern Idaho. Highlights of the instrument design and ensuing data from previous flights are presented herein.

Kuester, Michele A.; Lasnik, James K.; Ramond, Tanya; Lin, Tony; Johnson, Brian; Kaptchen, Paul; Good, William

2007-09-01

61

Method for detection and imaging over a broad spectral range  

Science.gov (United States)

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

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

2007-09-25

62

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

Directory of Open Access Journals (Sweden)

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

W. Gurlit

2004-12-01

63

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

64

Blackbody radiation sources for the IR spectral range  

Energy Technology Data Exchange (ETDEWEB)

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 ?{sub ?} 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. [All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI), Moscow (Russian Federation)

2013-09-11

65

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

66

Visible range lasing in dye-doped doubly periodic layered structures in dichromate gelatin emulsions  

International Nuclear Information System (INIS)

We have fabricated dye-doped doubly periodic layered structures exhibiting multiple bandgaps in the visible range in dichromate gelatin emulsions by a double-exposure holographic interference method. More importantly, optically pumped lasing with higher efficiency and lower threshold compared to that of singly periodic layered structures was observed in the dye-doped doubly periodic gelatin samples. This efficient lasing could be explained by the enhancement of the density of states at the overlapping bandgaps of two singly periodic layered structures. (paper)

67

Gravity-induced absorption changes in Phycomyces blakesleeanus during parabolic flights: first spectral approach in the visible.  

Science.gov (United States)

Gravity-induced absorption changes as experienced during a series of parabolas on the Airbus 300 Zero-G have been measured previously pointwise on the basis of dual-wavelength spectroscopy. Only the two wavelengths of 460 and 665 nm as generated by light-emitting diodes have been utilised during our first two parabolic-flight campaigns. In order to gain complete spectral information throughout the wavelength range from 400 to 900 nm, a miniaturized rapid scan spectrophotometer was designed. The difference of spectra taken at 0 g and 1.8 g presents the first gravity-induced absorption change spectrum measured on wild-type Phycomyces blakesleeanus sporangiophores, exhibiting a broad positive hump in the visible range and negative values in the near infrared with an isosbestic point near 735 nm. The control experiment performed with the stiff mutant A909 of Phycomyces blakesleeanus does not show this structure. These results are in agreement with those obtained with an array spectrophotometer. In analogy to the more thoroughly understood so-called light-induced absorption changes, we assume that gravity-induced absorption changes reflect redox changes of electron transport components such as flavins and cytochromes localised within the plasma membrane. PMID:17180493

Schmidt, Werner

2006-12-01

68

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

Directory of Open Access Journals (Sweden)

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

W. Gurlit

2005-01-01

69

A visible and NIR multilinear array dedicated to Sentinel 2 Multi Spectral Imager  

Science.gov (United States)

Sentinel 2 is an EU/ESA LEO Earth observation mission currently developed in the framework of Global Measurement Environment and Security (GMES) program. The associated Multi Spectral Imager instrument is equipped with about 230 mm length VNIR and SWIR Focal Plane Arrays, each one being made of twelve detectors mechanically butted in staggered configuration. Each elementary VNIR detector features tens spectral bands with 10m, 20m or 60m spatial sampling, ranging from about 430 to 900 nm. The devices are currently manufactured using a 0.35 ?m CMOS process optimised for imaging application and already space qualified, thanks to Astrium COBRA family development. For each spectral band, minimum SNR corresponding to reference flux and maximum integration time is required. Maximum flux and minimum MTF are also specified. The photo detector charge to voltage conversion factors and geometrical shapes have therefore been adjusted band per band in order to meet all these competing specifications. In addition, a per pixel Correlated Double Sampling readout circuit has been implemented to cancel photodiode reset noise, providing mean total readout noise lower than 200?V, and the output voltage swing has been improved in view of maximizing the device dynamics. Black coating has been deposited between the simple or double lines of photo detectors in order minimizing straight light effects. After a description of the multi linear detector architecture and functionality, its main performances will be presented. The current status of the industrial development will also be depicted.

Bréart de Boisanger, Michel; Saint-Pé, Olivier; Larnaudie, Franck; Guiry, Saïprasad; Magnan, Pierre; Martin-Gonthier, Philippe; Corbière, Franck; Guyatt, Neil

2009-09-01

70

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

71

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

72

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

Directory of Open Access Journals (Sweden)

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

C. E. Lund Myhre

2004-01-01

73

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

Directory of Open Access Journals (Sweden)

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

C. E. Lund Myhre

2004-06-01

74

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

Science.gov (United States)

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

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

2008-05-01

75

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

International Nuclear Information System (INIS)

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

76

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

Science.gov (United States)

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.

Zhu, Jiang-Feng; Xu, Liang; Lin, Qing-Feng; Zhong, Xin; Han, Hai-Nian; Wei, Zhi-Yi

2013-05-01

77

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)

78

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

CERN Document Server

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

Lavrov, B P; Zhukov, A S

2011-01-01

79

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.

Johansson, Sandra; Andersen, Martin

80

Development of low light level and wide dynamic range visible nephogram imaging technology  

Science.gov (United States)

The novel visible nephogram imaging technology for polar orbit platform is demonstrated in the paper, and it could be operated in from quarter moon to noon sunlight. The critical technologies and theirs solutions of the novel nephograph are included: (i) the low light level imaging capability is achieved by the combination of time delay and integration charge coupled device (TDI CCD) with push-broom imaging method; (ii) the large field of view capability is implemented by the combination of 3 pieces of imaging module with smaller field of view; (iii) the wide dynamic range capability is achieved by the combination of TDI CCD with gradient neutral density filter (NDF). On the basis of the analysis and trade-off of system design, the prototype of novel visible nephograph for polar orbit platform is developed. The results of experiments and tests in ground demonstration are satisfying, and the nephograph prototype is mainly met the customer demand. In the end of paper, several problems and theirs solution of novel technology for space application are also mentioned.

Xu, Wujun; Fan, Hong; Liu, Tangyou; Wei, Jun; Weng, Dongshan

2008-03-01

81

Simulation study on reconstruction model of three-dimensional temperature distribution within visible range in furnace  

International Nuclear Information System (INIS)

This paper presents a reconstruction model of three-dimensional temperature distribution in furnace based on radiative energy images captured by charge-coupled device (CCD) cameras within the visible wavelength range. Numerical simulation case was used in this study and a zigzag eccentric temperature distribution was assumed to verify the model. Least square QR-factorization (LSQR) method was introduced to deal with reconstruction equation. It is found that the reconstructed temperature distributions in low-temperature areas had some fluctuations and high-temperature areas were reconstructed well. The whole reconstruction relative error was mainly due to errors in low-temperature areas and the relative error for highest-temperature reconstruction was quite small

82

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

CERN Document Server

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

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

2008-01-01

83

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

84

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

85

Extending the spectral range of CdSe/ZnSe quantum wells by strain engineering  

Science.gov (United States)

We demonstrate efficient room-temperature photoluminescence and spectral tuning of epitaxially grown ZnSe/CdSe quantum well structures almost over the whole visible spectrum (470-600 nm wavelength). The key element to achieve the observed high quantum efficiency and enormous tuning range was the implementation of a special strain engineering technique, which allows us to suppress substantial lattice relaxation of CdSe on ZnSe. Previous studies indicated that a CdSe coverage exceeding 3 ML on ZnSe results in the formation of extensive lattice defects and complete quenching of the photoluminescence at low and room temperature. In contrast, our approach of strain engineering enables the deposition of planar CdSe quantum wells with a thickness ranging from 1 to 6 ML with excellent optical properties. We attribute the observed experimental features to a controllable strain compensation effect that is present in an alternating system of tensile and compressively strained epitaxial layers and supported this model by calculations of the transition energies of the ZnSe/CdSe quantum wells.

Finke, A.; Ruth, M.; Scholz, S.; Ludwig, A.; Wieck, A. D.; Reuter, D.; Pawlis, A.

2015-01-01

86

Partially Transparent Petaled Mask/Occulter for Visible-Range Spectrum  

Science.gov (United States)

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

Shiri, Ron Shahram; Wasylkiwskyj, Wasyl

2013-01-01

87

Discrete spectral selection and wavelength encoding from a visible continuum using optical MEMS  

International Nuclear Information System (INIS)

We report on a novel optical system for discrete selection of precise, user-defined spectral regions from the emitted spectrum of a white light source. The device, which is based on an array of electrostatically actuated, achromatic micro-mirrors, allows us to select signals with spectral widths between 4 and 15 nm from the super-continuum (?400 to ?750 nm), with an extinction ratio of more than 90% and a spectral power density of 15 µW nm?1. Each optical MEMS element from the array can be switched asynchronously at a selected frequency performing both the spatial selection and the frequency modulation of a specific narrow spectral region. The method we describe allows the spectral and/or temporal and polarization encoding of the selected spectral bands and may find extensive applications in biomedical research

88

Spectral irradiance measurement in the visible-ultraviolet region using synchrotron radiation  

International Nuclear Information System (INIS)

Spectral irradiances of a quartz-bromine lamp calibrated against the currently maintained ETL standard were compared with those of synchrotron radiation from TERAS in order to reconfirm the magnitude of standard unit, especially, in the ultraviolet region. The spectral irradiance unit at the wavelength of 500 nm was taken to be equal to each other. It was concluded that the magnitude of spectral irradiance unit currently used at ETL should be increased at the short wavelengths by maximum 7%. (author)

89

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

90

Spectral reflectance of carbonate minerals in the visible and near infrared (0.35-2.55 microns) - Anhydrous carbonate minerals  

Science.gov (United States)

Visible and near IR reflectance spectra for anhydrous carbonate minerals are presented, and the use of the spectra to determine the mineralogy and gaining information for the carbonate minerals is examined. Seven strong absorption bands at wavelengths greater than 1.6 microns are observed in all the spectra of anhydrous end-member carbonate minerals. The band position, intensity, and width for the carbonate bands are studied. The iron and maganese bands for the carbonate minerals are analyzed. The potential causes of spectral differences between carbonate minerals are investigated.

Gaffey, Susan J.

1987-01-01

91

Visible light optical coherence tomography for in vivo imaging the spectral contrasts of the retinal nerve fiber layer  

Science.gov (United States)

The ultimate goal of the study is to provide an imaging tool to detect the earliest signs of glaucoma before clinically visible damage occurs to the retinal nerve fiber layer (RNFL). Studies have shown that the optical reflectance of the damaged RNFL at short wavelength (<560nm) is reduced much more than that at long wavelength, which provides spectral contrasts for imaging the earliest damage to the RNFL. To image the spectral contrasts we built a dual-band spectral-domain optical coherence tomography (SD-OCT) with centered wavelength of 415nm (VIS) and 808nm (NIR), respectively. The light at the two bands was provided by the fundamental and frequency-doubled outputs of a broadband Ti: Sapphire laser. The depth resolutions of the VIS and NIR OCT systems are 12.2?m and 4.7?m in the air. The system was applied to imaging the rat retina in vivo. Significantly different appearances between the OCT cross sectional images at the two bands are observed. The experimental results showed that the dual-band OCT system is feasible for imaging the spectral contrasts of the RNFL.

Zhang, Xiangyang; Hu, Jianming; Knighton, Robert W.; Huang, Xiang-Run; Puliafito, Carmen A.; Jiao, Shuliang

2012-01-01

92

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

93

The properties of ITE's silicon avalanche photodiodes within the spectral range used in scintillation detection  

CERN Document Server

The design and properties of 3 mm silicon avalanche photodiodes developed at ITE are presented. Their performance parameters within the spectral range applicable in scintillation detection (400-700 nm) are discussed and compared to those for near infrared radiation.

Wegrzecka, I

1999-01-01

94

The properties of ITE's silicon avalanche photodiodes within the spectral range used in scintillation detection  

International Nuclear Information System (INIS)

The design and properties of 3 mm silicon avalanche photodiodes developed at ITE are presented. Their performance parameters within the spectral range applicable in scintillation detection (400-700 nm) are discussed and compared to those for near infrared radiation

95

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.

96

MEMS-based Tunable Optical Filter Arrays for Nano-Spectrometer in the Visible Spectral Range  

OpenAIRE

Optische Spektrometer sind bekannte Instrumente für viele Anwendungen in Life Sciences, Produktion und Technik aufgrund ihrer guten Selektivität und Sensitivität zusammen mit ihren berührungslosen Messverfahren. MEMS (engl. Micro-electro-mechanical system)-basierten Spektrometer werden als disruptive Technologie betrachtet, in der miniaturisierte Fabry-Pérot Filter als sehr attraktiv für die optische Kommunikation und 'Smart Personal Environments', einschließlich des medizinischen A...

Setyawati, Onny

2012-01-01

97

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

98

An improved digital global map of spectral parameters of Vesta from the Visible and Infrared mapping Spectrometer onboard Dawn  

Science.gov (United States)

The NASA/Dawn discovery mission has been designed to study in detail two of the largest proto-planets of the asteroid belt: Vesta and Ceres. From July 2011 to September 2012, Dawn has been orbiting around Vesta and the instruments have returned scientific data from three different orbital altitudes: the survey, the high altitude, and the low altitude mapping orbits. From these orbits, Dawn's Visible and Infrared mapping Spectrometer (VIR) acquired infrared and visible spectra from 0.2 to 5 microns, sampled in 864 channels with a spatial resolution reaching about 150 m/pixel. VIR spectra of Vesta have been analyzed to derive spectral parameters, which synthesize specific characteristics of the single spectra and are diagnostic of the mineralogical composition and the physical state of the portion of surface being observed. In particular, we focus on spectral parameters related to the 1.0- and 2.0-micron bands (band I and band II) typical of pyroxenes. In general, a shift in band center suggests a change in composition while the change in band depths are diagnostic of a change in the physical state of the material. Combined analysis of spectral parameters leads towards specific studies, as for example the detection of a specific mineral assemblage. Since the acquisition of first VIR data, we have worked in gathering into maps the spectral parameters extracted from every single spectrum, resulting in a global view of the mineralogical diversity of the surface of Vesta. The maps are being produced in the same projection as the camera mosaics, enabling to observe and analyze the spatial correlation between mineralogy and morphology. Here we present the global maps of spectral parameters of Vesta, improved from the previously presented ones. Filtering has been applied to input data, on the base of experience acquired during the mission. The resulting maps are more consistent, and the coverage has not been affected (practically) by the filtering process applied. The digital maps are being produced in several digital formats, allowing both the spectroscopists and non-spectroscopists to work on the same data using the software tools they are more familiar with. In particular, among other formats, the digital maps are produced in a Geographic Information System (GIS) -compatible digital format, so they can be used together with other digital maps as image mosaics, topography and geologic maps, introducing interesting perspectives for the scientific investigation of the proto-planet Vesta.

Frigeri, A.; De Sanctis, M.; Ammannito, E.; Tosi, F.; Capaccioni, F.; Capria, M.; Zambon, F.; Palomba, E.; Longobardo, A.; Fonte, S.; Giardino, M.; Magni, G.; Jaumann, R.; Raymond, C.; Russell, C.

2014-07-01

99

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

100

Spectral measurements of visible solar direct-normal irradiance and air pollutant attenuation coefficients at Helwan  

Energy Technology Data Exchange (ETDEWEB)

Solar radiation spectra were measured by a ground-level pyrheliometer (Eppley NIP) equipped with a filter wheel. Three flat, circular, Schott filters were used to define three spectral bands. The filters were large band-pass filters of the types OG530, RG630 and RG695. The experiment was conducted from June 1991 to May 1992 on the roof of the new building of the National Research Institute of Astronomy and Geophysics (NRIAG) at Helwan. The Linke turbidity factor for the integrated radiation, and the spectral attentuation coefficients of solar energy caused by aerosols were computed. In comparison with earlier measurements in 1910, 1967 and 1987, it is clear that there is a continuous increase in the turbidity factor, due to an increase of industrial waste in the Helwan atmosphere. A correlation analysis between the turbidity factors and the total suspended particles, smoke and sulphur dioxide was carried out. Meterological elements and sand storms have been taken into consideration in the correlation analysis. (author)

Shaltout, M.A.M.; Rahoma, U.A.; Fathy, A. [National Research Inst. of Astronomy and Geophysics, Helwan, Cairo (Egypt)

1996-04-01

101

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

102

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

103

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

Science.gov (United States)

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

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

2014-12-01

104

Negative refraction and sub-wavelength focusing in the visible range using transparent metallo-dielectric stacks.  

Science.gov (United States)

We numerically demonstrate negative refraction of the Poynting vector and sub-wavelength focusing in the visible part of the spectrum using a transparent multilayer, metallo-dielectric photonic band gap structure. Our results reveal that in the wavelength regime of interest evanescent waves are not transmitted by the structure, and that the main underlying physical mechanisms for sub-wavelength focusing are resonance tunneling, field localization, and propagation effects. These structures offer several advantages: tunability and high transmittance (50% or better) across the visible and near IR ranges; large object-image distances, with image planes located beyond the range where the evanescent waves have decayed. From a practical point of view, our findings point to a simpler way to fabricate a material that exhibits negative refraction and maintains high transparency across a broad wavelength range. Transparent metallo-dielectric stacks also provide an opportunity to expand the exploration of wave propagation phenomena in metals, both in the linear and nonlinear regimes. PMID:19532269

Scalora, Michael; D'Aguanno, Giuseppe; Mattiucci, Nadia; Bloemer, Mark J; de Ceglia, Domenico; Centini, Marco; Mandatori, Antonio; Sibilia, Concita; Akozbek, Neset; Cappeddu, Mirko G; Fowler, Mark; Haus, Joseph W

2007-01-22

105

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

106

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

107

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

International Nuclear Information System (INIS)

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

108

Wavelength conversion based spectral imaging  

DEFF Research Database (Denmark)

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

Dam, Jeppe Seidelin

109

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

International Nuclear Information System (INIS)

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

110

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

CERN Document Server

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

Canning, John; Cook, Kevin

2015-01-01

111

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

112

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

Science.gov (United States)

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

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

2006-02-01

113

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

114

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

115

Broadband superresolving lens with high transparency for propagating and evanescent waves in the visible range  

OpenAIRE

We present a theoretical analysis of a super-resolving lens based on 1-dimensional metallo-dielectric photonic crystals composed of Ag/GaP multilayers. The lens contains a total of 10 optical skin depths of Ag, yet maintains a normal incidence transmittance of ~50% for propagating waves over the super-resolving wavelength range of 500-650 nm. The individual Ag layers are 22 nm thick and can be readily fabricated in conventional deposition systems. The importance of anti-refl...

Bloemer, Mark J.; D Aguanno, Giuseppe; Mattiucci, Nadia; Scalora, Michael; Akozbek, Neset

2006-01-01

116

Broadband superresolving lens with high transparency for propagating and evanescent waves in the visible range  

CERN Document Server

We present a theoretical analysis of a super-resolving lens based on 1-dimensional metallo-dielectric photonic crystals composed of Ag/GaP multilayers. The lens contains a total of 10 optical skin depths of Ag, yet maintains a normal incidence transmittance of ~50% for propagating waves over the super-resolving wavelength range of 500-650 nm. The individual Ag layers are 22 nm thick and can be readily fabricated in conventional deposition systems. The importance of anti-reflection coatings for the transmission of evanescent and propagating waves is illustrated by comparison to periodic and symmetric structures without the coatings. In addition, the reflection for propagating waves is reduced to ~5% across the super-resolving wavelength band diminishing the interference between the object and the lens.

Bloemer, M J; D'Aguanno, G; Mattiucci, N; Scalora, M; Aguanno, Giuseppe D'; Akozbek, Neset; Bloemer, Mark J.; Mattiucci, Nadia; Scalora, Michael

2006-01-01

117

Application of lidar in ultraviolet, visible and infrared ranges for early forest fire detection  

Science.gov (United States)

The efficiencies of direct lidars operating at 355, 532, 1064 and 1540-nm radiation wavelengths for early forest fire detection were compared. For each wavelength, the range for reliable smoke-plume detection was estimated on the basis of a computer simulation plume using a one-dimensional ``top-hat'' gas dynamic model for the calculation of the backscattering and extinction-coefficient profiles within the plume. The agreement between the predicted signal-to-noise ratio (SNR) and experimental results for 532 and 1064-nm wavelength radiation is good. The decrease of the signal-to-noise ratio with distance is maximum for 355 nm and minimum for 1064 nm. At 1540 nm, the decay of SNR with distance is slightly faster, but the SNR is higher than for other wavelengths, leading to the highest detection efficiency for the same energy of the probing laser pulse. For a burning rate of 2 kg/s and a laser beam divergence of 2.5 mr, the maximum distance for reliable detection varies between 6 and 12 km, depending on the wavelength.

Lavrov, A.; Utkin, A. B.; Vilar, R.; Fernandes, A.

118

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

119

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

International Nuclear Information System (INIS)

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

120

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.

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

2014-08-01

121

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

122

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

2014-08-15

123

Against the long-range spectral leakage of the cosine window family  

Science.gov (United States)

Suppressing spectral leakage in the fast Fourier transform (FFT) has been investigated for over 30 years. Regarding the frequently used cosine window family, it is observed that the long-range leakage sampled by FFT spectral lines follow a flat trajectory. Consequently, the long-range leakage is approximated by polynomials in this paper. In light of this parametric model, the interpolating formula is presented with up to nine-point for a cosine window with maximum side lobe decaying. Its expression is general in the window order and number of interpolating points. Some well-known formulas of the modulus-based interpolated FFT are parallel to special cases of the new formula, but the former are susceptible to significant bias at coherent sampling conditions. The new formula was tested with real-valued signals containing a single tone and then duel tones. It is demonstrated the new formula is easy to implement and is free of the significant bias aforementioned.

Chen, Kui Fu; Jiang, Jing Tao; Crowsen, Stephen

2009-06-01

124

Defining a Polymethine Dye for Fluorescence Anisotropy Applications in the Near-Infrared Spectral Range  

OpenAIRE

Fluorescence anisotropy in the near-infrared (NIR) spectral range is challenging because of the lack of appropriate NIR fluorescent labels. We have evaluated polymethine fluorescent dyes to identify a leading candidate for NIR anisotropy applications. The NIR dye LS601 demonstrated low fluorescence anisotropy values (r) as a result of its relatively long fluorescent lifetime 1.3 ns. The r value of LS601 unbound and coupled to biological macromolecules was found to have a sufficient dynamic ra...

Gustafson, Tiffany P.; Cao, Qian; Achilefu, Samuel; Berezin, Mikhail Y.

2012-01-01

125

One-dimensional Dirac operators with zero-range interactions: Spectral, scattering, and topological results  

Science.gov (United States)

The spectral and scattering theory for 1-dimensional Dirac operators with mass m and with zero-range interactions are fully investigated. Explicit expressions for the wave operators and for the scattering operator are provided. These new formulae take place in a representation which links, in a suitable way, the energies -? and +?, and which emphasizes the role of ±m. Finally, a topological version of Levinson's theorem is deduced, with the threshold effects at ±m automatically taken into account.

Pankrashkin, Konstantin; Richard, Serge

2014-06-01

126

Fully-tunable femtosecond laser source in the ultraviolet spectral range  

OpenAIRE

We demonstrate experimentally the full tunability of a coherent femtosecond source in the whole ultraviolet spectral region. The experiment relies on the technique of high-order harmonic generation driven by a near-infrared parametric laser source in krypton gas. By tuning the drive wavelength in the range between 1100 to 1900 nm, we generated intense harmonics from near to extreme ultraviolet. A number of photons per shot of the order of 10^7 has been measured for the first...

Mahieu, B.; Coraggia, S.; Callegari, C.; Coreno, M.; Ninno, G.; Devetta, M.; Frassetto, F.; Garzella, D.; Negro, M.; Spezzani, C.; Vozzi, C.; Stagira, S.; Poletto, L.

2011-01-01

127

High spatial and spectral resolution long-range sensing using Brillouin echoes  

OpenAIRE

High spatial (~cm) and spectral (~MHz) resolution Brillouin sensing is realized with enhanced signal to noise ratio using a pre-activated acoustic field and an optical phase control over the interrogating pulse. Pre-activation of the acoustic field preserves the Brillouin natural linewidth and a differential gain technique extends the method to long ranges. Experimentally, fully resolved measurements of the Brillouin frequency shift of a 5 cm spot perturbation at the far end of a 5 km fibre h...

Foaleng, S. M.; Tur, M.; Beugnot, J. C.; The?venaz, Luc

2010-01-01

128

Spectral 6DOF registration of noisy 3D range data with partial overlap.  

Science.gov (United States)

We present Spectral Registration with Multilayer Resampling (SRMR) as a 6 Degrees Of Freedom (DOF) registration method for noisy 3D data with partial overlap. The algorithm is based on decoupling 3D rotation from 3D translation by a corresponding resampling process of the spectral magnitude of a 3D Fast Fourier Transform (FFT) calculation on discretized 3D range data. The registration of all 6DOF is then subsequently carried out with spectral registrations using Phase Only Matched Filtering (POMF). There are two main aspects for the fast and robust registration of Euler angles from spherical information in SRMR. First of all, there is the permanent use of phase matching. Second, based on the FFT on a discrete Cartesian grid, not only one spherical layer but also a complete stack of layers are processed in one step. Experiments are presented with challenging datasets with respect to interference and overlap. The results include the fast and robust registration of artificially transformed data for ground-truth comparison, scans from the Stanford Bunny dataset, high end 3D laser range finder (LRF) scans of a city center, and range data from a low-cost actuated LRF in a disaster response scenario. PMID:22868648

Bülow, Heiko; Birk, Andreas

2013-04-01

129

Valentin A. Fabrikant: negative absorption, his 1951 patent application for amplification of electromagnetic radiation (ultraviolet, visible, infrared and radio spectral regions) and his experiments  

Science.gov (United States)

This paper is devoted to Moscow physicist Valentin A. Fabrikant who is known for his 1939 thesis with suggestion of experiments on light amplification directly proving the existence of negative absorption in gas discharge, his 1951 patent application (jointly with M.M. Vudynsky and F.A. Butaeva) for amplification of electromagnetic radiation (ultraviolet, visible, infrared and radio spectral regions), and his experimental attempts (jointly with F.A. Butaeva) to observe light amplification in gas discharge (paper submission of December 1957).

Lukishova, S. G.

2010-09-01

130

Setup for the in situ monitoring of the irradiation-induced effects in optical fibers in the ultraviolet-visible optical range  

International Nuclear Information System (INIS)

The paper describes a setup for in situ monitoring of the radiation-induced optical absorption and the radiation-induced luminescence, in the UV-visible spectral range (200-800 nm), for large diameter (400 ?m) optical fibers. Silica and sapphire optical fibers were irradiated, at room temperature, with gamma rays (dose rate of 0.33 kGy/h, total dose of 34.5 kGy) and protons (dose rate of 100 Gy/s, total dose of 1.8 MGy). At several moments, the irradiation was interrupted and the annealing of the radiation-induced optical absorption was observed at room temperature. The setup also makes possible the monitoring of the optical radiation-induced recovery of the optical absorption (the effect of photobleaching), as the optical fiber can be exposed at the same time to both the ionizing radiation (gamma or protons) and to the radiation of a broadband optical source. The optical absorption and radioluminescence were measured with an optical fiber multichannel spectrometer coupled to an optical fiber multiplexer. The equipment control as well as the data collection and processing were performed using the graphical programming environment LabVIEW. The paper includes several graphs illustrating the evolution of the optical absorption and radiation-induced luminescence during gamma and proton irradiation of optical fibers

131

Setup for the in situ monitoring of the irradiation-induced effects in optical fibers in the ultraviolet-visible optical range  

Science.gov (United States)

The paper describes a setup for in situ monitoring of the radiation-induced optical absorption and the radiation-induced luminescence, in the UV-visible spectral range (200-800 nm), for large diameter (400?m) optical fibers. Silica and sapphire optical fibers were irradiated, at room temperature, with gamma rays (dose rate of 0.33kGy/h, total dose of 34.5 kGy) and protons (dose rate of 100Gy/s, total dose of 1.8 MGy). At several moments, the irradiation was interrupted and the annealing of the radiation-induced optical absorption was observed at room temperature. The setup also makes possible the monitoring of the optical radiation-induced recovery of the optical absorption (the effect of photobleaching), as the optical fiber can be exposed at the same time to both the ionizing radiation (gamma or protons) and to the radiation of a broadband optical source. The optical absorption and radioluminescence were measured with an optical fiber multichannel spectrometer coupled to an optical fiber multiplexer. The equipment control as well as the data collection and processing were performed using the graphical programming environment LabVIEW. The paper includes several graphs illustrating the evolution of the optical absorption and radiation-induced luminescence during gamma and proton irradiation of optical fibers.

Sporea, D. G.; Sporea, R. A.

2005-11-01

132

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

Science.gov (United States)

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

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

2014-11-01

133

Ultrafast Photochemistry of Bromoform in Solution Probed in the Deep-Uv to Near-Ir Spectral Range  

Science.gov (United States)

The photochemical pathways of bromoform (CHBr_3) in dilute (10 mM) and concentrated (500 mM) acetonitrile and methylcyclohexane solutions following excitation with ultrafast (100 fs) 255-nm laser pulses were investigated. Ultrafast transient absorption spectra manifest the formation of a CHBr_2 radical species within the apparatus response function through its intense deep-UV (˜ 250-nm) absorption band. The formation of iso-bromoform (iso-CHBr_2-Br) occurs within few hundreds of femtoseconds after photoexcitation and do not correlate with the dynamics of CHBr_2 radical. The iso- CHBr_2-Br isomer species decays single exponentially with a 290-ps time constant in acetonitrile. In methylcyclohexane, however, the intense absorption of the isomer in the visible spectral range dominates the transient spectra up to the longest investigated time delays of 1.2 ns. Ab initio and DFT calculations in conjunction with continuum solvation models strongly suggest that acetonitrile opens a pathway for the iso-CHBr_2-Br to CHBr_3 isomerization through a polar, cyclic transition state. This channel is not thermodynamically feasible in the non-polar solvent.

Pal, Suman Kalyan; El-Khoury, Patrick; Mereshchenko, Andrey Sergeevich; Tarnovsky, Alexander N.

2010-06-01

134

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

135

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

136

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

137

Pulsed, all solid-state light source 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 SFG between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser.

Tidemand-Lichtenberg, Peter; Andersen, Martin

138

Photonic crystals and Bragg gratings for the mid-IR and terahertz spectral ranges  

Energy Technology Data Exchange (ETDEWEB)

A method for the fabrication of 2D periodic structures by contact optical photolithography with image inversion is reported. The optical properties of photonic crystals and Bragg gratings for mid-IR and terahertz emitters are considered. The possibility of raising the integral emission intensity of light-emitting diodes for the mid-IR spectral range is demonstrated. The requirements to gratings for the output of terahertz emission generated by surface plasmons excited in layers of narrow-gap degenerate semiconductors with an accumulation layer are determined.

Usikova, A. A., E-mail: usikova@mail.ioffe.ru; Il’inskaya, N. D.; Matveev, B. A.; Shubina, T. V.; Kop’ev, P. S. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2013-12-15

139

Fully-tunable femtosecond laser source in the ultraviolet spectral range  

CERN Document Server

We demonstrate experimentally the full tunability of a coherent femtosecond source in the whole ultraviolet spectral region. The experiment relies on the technique of high-order harmonic generation driven by a near-infrared parametric laser source in krypton gas. By tuning the drive wavelength in the range between 1100 to 1900 nm, we generated intense harmonics from near to extreme ultraviolet. A number of photons per shot of the order of 10^7 has been measured for the first harmonic orders. Many novel scientific prospects are expected to benefit from the use of such a table-top tunable source.

Mahieu, B; Callegari, C; Coreno, M; De Ninno, G; Devetta, M; Frassetto, F; Garzella, D; Negro, M; Spezzani, C; Vozzi, C; Stagira, S; Poletto, L

2011-01-01

140

Spectral broadening due to long-range Coulomb interactions in the molecular metal TTF-TCNQ  

International Nuclear Information System (INIS)

We employ density-functional theory to calculate realistic parameters for an extended Hubbard model of the molecular metal TTF-TCNQ. Considering both intra- and intermolecular screening in the crystal, we find that longer-range Coulomb interactions along the molecular stacks, as well as inter-stack coupling are of importance. Contrary to past belief, these terms do not lead to the formation of a Wigner lattice, but simply broaden the spectral function. We show how this can be understood already in perturbation theory. Moreover we calculate the effect of the nearest neighbor repulsion on the Luttinger parameter. (orig.)

141

On the spectral index of the two local radio sources on the Sun in short centimeter range  

International Nuclear Information System (INIS)

Radioemission of two local sources on the Sun is considered in the wavelength ranges of 3.5-2.5 and 2.5-1.9 cm. Observations were made with a 22 m radiotelescope in three wavelengths of 3.5, 2.5 and 1.9 cm simultaneously. The measurement data were used to calculate spectral indices. Time dependences of spectral indices of the observed sources in both wavelength ranges are shown. Spectral indices values for a local source related with a low activity group are noticeably higher than the corresponding values for a more active group. As the flare activity of the latter group grows and power radiobursts are generated in it, the spectral indices values in the above intervals considerably decrease and the spectral index in the 3.5-2.5 cm range can accept negative values

142

Nonlinear Spectral Unmixing of Lunar Analog Materials in the Thermal Infrared Range  

Science.gov (United States)

It has been predicted in [1, 2] that the reflectance spectrum of a mixture of minerals can be described in terms of the Hapke model [3] based on a linear superposition of the spectra of the mineral-specific single-scattering albedo. This approach has been applied to near-infrared (NIR) data e.g. in [4] relying on the analysis of absorption features. Pronounced spectral features are also apparent in the thermal infrared (TIR) range, i.e. the Christiansen feature and the Reststrahlen bands, which may be used to classify different minerals (cf. e.g. [5]). Notably, the TIR range of the spectrum will be measured by the MERTIS instrument [6]. In this study, we apply the Hapke based unmixing method [4] to TIR spectra of mineral powders of 32-63 ?m grain size.

Rommel, D.; Grumpe, A.; Wöhler, C.; Morlok, A.; Hiesinger, H.; Mall, U.

2014-04-01

143

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

International Nuclear Information System (INIS)

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

144

High-speed full-range spectral-domain correlation mapping optical coherence tomography  

Science.gov (United States)

We present a full range spectral-domain correlation mapping optical coherence tomography (cm-OCT) method to obtain complex conjugate free, full-range correlation mapping angiography. The mirror image elimination is based on linear phase modulation of B-frames by introducing a slight off-set of the probe beam with respect to the lateral scanning fast mirror's pivot axis. An algorithm that exploits Hilbert transform to obtain complex-conjugate free image in conjunction with the cm-OCT algorithm is used to obtain full-range imaging of microcirculation within tissue beds in vivo. The proposed system is based on a high speed spectrometer at 92kHz with a modified scanning protocol to achieve higher acquisition speed to render cmOCT images with high-speed and wide scan range. The estimated sensitivity of the system was around 105dB near the zero-delay line with ~13dB roll-off from 0.5mm to 3mm imaging-depth position. The estimated axial and lateral resolutions are 12 ?m and 25 ?m, respectively. A direct consequence of this complex conjugate artifact elimination is the enhanced flow imaging sensitivity for deep tissue imaging application by doubling the imaging depth. In turn, this also provides additional flexibility to explore the most sensible measurement range near the zero-delay line.

Subhash, Hrebesh M.; Leahy, Martin

2013-02-01

145

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

146

Directional visible light scattering by silicon nanoparticles  

CERN Document Server

Directional light scattering by spherical silicon nanoparticles in the visible spectral range is experimentally demonstrated for the first time. These unique scattering properties arise due to simultaneous excitation and mutual interference of magnetic and electric dipole resonances inside a single nanosphere. Directivity of the far-field radiation pattern can be controlled by changing light wavelength and the nanoparticle size. Forward-to-backward scattering ratio above 6 can be experimentally obtained at visible wavelengths. These unique properties of silicon nanoparticles make them promising for design of novel low-loss visible- and telecom-range nanoantenna devices.

Fu, Yuan Hsing; Miroshnichenko, Andrey E; Yu, Ye Feng; Lukiyanchuk, Boris

2012-01-01

147

Reflective and transmissive broadband coating polarizers in a spectral range centered at 121.6 nm  

Science.gov (United States)

Polarimetry is a powerful tool for the interpretation of the role of the coronal plasma in the energy transfer processes from the inner parts of the Sun to the outer space. One of the key lines for observations is H I Lyman ? (121.6 nm) among few spectral lines in the far ultraviolet (FUV), and hence efficient linear polarizers at this line are demanded. New designs based on (Al/MgF2)n multilayer coatings have been developed to obtain the smallest possible reflectance in the parallel plane of polarization (Rpar) with a simultaneous high reflectance in the perpendicular plane of polarization (Rper). Samples stored in nitrogen for ˜8–17 months resulted in efficient polarizers at 121.6 nm, with Rpar ˜ 0.01–0.017 and Rper ˜ 0.69–0.725. The designs with a number n = 3–4 bilayers of Al/MgF2 result in a wider spectral range of efficient linear polarizers, compared to what can be obtained with n = 2. Coatings following various designs with good polarizing performance in a 7–8 nm wide FUV range were prepared. For the first time, a transmissive coating polarizer has been developed for this range, which has the benefit that it involves no deviation of the beam; it is based on another design of (Al/MgF2)3 multilayer coating. The transmissive polarizer has a good transmittance ratio between the two polarization components and, even though its figure of merit is not as high as that of the reflective polarizers, it incorporates filtering properties to reject wavelengths both below and above 121.6 nm; this property might enable a polarimeter for solar physics with an improved global figure of merit if a filter to isolate the H I Lyman ? line could be avoided.

Larruquert, Juan I.; Malvezzi, A. Marco; Giglia, Angelo; Aznárez, José A.; Rodríguez-de Marcos, Luis; Méndez, José A.; Miotti, Paolo; Frassetto, Fabio; Massone, Giuseppe; Nannarone, Stefano; Crescenzio, Giuseppe; Capobianco, Gerardo; Fineschi, Silvano

2014-12-01

148

Photon counting detector with picosecond timing resolution for X to visible range on the basis of GaP  

International Nuclear Information System (INIS)

Avalanche photodiodes specifically designed for single photon counting devices have been developed on the basis of various semiconductor materials: Si, Ge, GaP, GaAsP, and InGaAs at the Czech Technical University within the last 20 years. All the semiconductor detectors operate at a room temperature or at thermoelectrically achievable temperatures except of the germanium-based detector, which requires liquid nitrogen cooling. Electronic circuits for these detectors biasing, quenching and control have been developed and optimized for different applications. Timing resolution of solid-state photon counters as high as 50 ps full width at a half maximum has been achieved when detecting single photon signals. Circuits permitting operation of solid-state photon counters in both single and multiple photon signal regimes have been developed and applied. The compact and rugged design, radiation resistance, and low operating voltage are attractive features of solid state photon counters in various applications including the space projects. The sensitivity of solid-state photon counters spans from X-ray up to 1800 nm in the near infrared region. The avalanche structures based on the GaP material exhibit several special features for X-ray operation: the timing resolution as high 100 ps may be achieved when detecting individual quanta, the wavelength range spans from 0.1 nm up to visible light. The GaP exhibits from all the existing solid-state photon counters the highest detectiostate photon counters the highest detection efficiency in X-ray, it reaches 14% at 0.1 nm band

149

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

150

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

International Nuclear Information System (INIS)

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.

151

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

152

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-10-28

153

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

154

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)

155

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

CERN Document Server

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

Kamath, D; Van Winckel, H

2014-01-01

156

Design and development of an injection-molded demultiplexer for optical communication systems in the visible range.  

Science.gov (United States)

Optical simulation software based on the ray-tracing method offers easy and fast results in imaging optics. This method can also be applied in other fields of light propagation. For short distance communications, polymer optical fibers (POFs) are gradually gaining importance. This kind of fiber offers a larger core diameter, e.g., the step index POF features a core diameter of 980 ?m. Consequently, POFs have a large number of modes (>3 million modes) in the visible range, and ray tracing could be used to simulate the propagation of light. This simulation method is applicable not only for the fiber itself but also for the key components of a complete POF network, e.g., couplers or other key elements of the transmission line. In this paper a demultiplexer designed and developed by means of ray tracing is presented. Compared to the classical optical design, requirements for optimal design differ particularly with regard to minimizing the insertion loss (IL). The basis of the presented key element is a WDM device using a Rowland spectrometer setup. In this approach the input fiber carries multiple wavelengths, which will be divided into multiple output fibers that transmit only one wavelength. To adapt the basic setup to POF, the guidance of light in this element has to be changed fundamentally. Here, a monolithic approach is presented with a blazed grating using an aspheric mirror to minimize most of the aberrations. In the simulations the POF is represented by an area light source, while the grating is analyzed for different orders and the highest possible efficiency. In general, the element should be designed in a way that it can be produced with a mass production technology like injection molding in order to offer a reasonable price. However, designing the elements with regard to injection molding leads to some inherent challenges. The microstructure of an optical grating and the thick-walled 3D molded parts both result in high demands on the injection molding process. This also requires complex machining of the molding tool. Therefore, different experiments are done to optimize the process parameter, find the best molding material, and find a suitable machining method for the molding tool. The paper will describe the development of the demultiplexer by means of ray-tracing simulations step by step. Also, the process steps and the realized solutions for the injection molding are described. PMID:23842150

Höll, S; Haupt, M; Fischer, U H P

2013-06-20

157

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...

158

Compact and efficient nanosecond pulsed tuneable OPO in the mid-IR spectral range  

Science.gov (United States)

A compact, robust and efficient nanosecond pulsed optical parametric oscillator (OPO) generating radiation in the mid- IR spectral range is reported. The OPO is based on periodically poled material for the efficient non-linear processes of up-converting 1064 nm radiation to 1538 and 3450 nm respectively. Pulsed emission exceeding 130 mW average power at the idler (3450 nm) with a total conversion efficiency of 30%, including both signal and idler, has been reached. The maximum pulse energy of the idler is 11 ?J, pulse duration around 4 ns and peak power close to 3 kW. The results are achieved for an optical pump power of 1.4 W at the entrance of the OPO and an electrical pump power of 14 W. The total size of the OPO device is only 125x70x45 mm3 (LxWxH) including the pump laser at 1064 nm. The idler output radiation is narrowed by spectral filtering to nm and temperature tuneable over > 50 nm. The OPO has a robust design and withstands shocks up to 60g at 8 ms and the storage temperature is -20 °C to + 60 °C. The compact size and low power consumption make this OPO device suitable for many kinds of molecular spectroscopy applications in the areas of environmental monitoring and pollution control as well as in combustion physics and process control. Integration of the OPO source into compact equipment for Photo Acoustic Spectroscopy (PAS) allowing fast and highly sensitive detection of methane and ethanol at ppb-levels is also described.

Hellström, J.; Jänes, P.; Elgcrona, G.; Karlsson, H.

2013-05-01

159

Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind  

OpenAIRE

We measure the power and spectral index anisotropy of high speed solar wind turbulence from scales larger than the outer scale down to the ion gyroscale, thus covering the entire inertial range. We show that the power and spectral indices at the outer scale of turbulence are approximately isotropic. The turbulent cascade causes the power anisotropy at smaller scales manifested by anisotropic scalings of the spectrum: close to k^{-5/3} across and k^{-2} along the local magnet...

Wicks, Rt; Horbury, Ts; Chen, Chk; Schekochihin, Aa

2010-01-01

160

Spatial distribution of spectral parameters of high latitude geomagnetic disturbances in the Pc5/Pi3 frequency range  

OpenAIRE

We analyze spectral parameters of the geomagnetic disturbances within the 1–4 mHz (Pc5/Pi3) frequency range for 29 observatories from polar to auroral latitudes. The main object of this study is the broadband (noise) background under quiet and moderately disturbed conditions. To obtain a quantitative description of background high-latitude long period ULF activity the log-log dependence of the spectral power on frequency is expanded over Legendre polynomials, and the coefficients of this ex...

Pilipenko, V. A.; Yagova, N. V.; Engebretson, M. J.; Baransky, L. N.

2010-01-01

161

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

Scientific Electronic Library Online (English)

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

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

2014-07-30

162

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

OpenAIRE

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 semitrans...

Grusche, Sascha

2014-01-01

163

Development of MWCNTs-based wideband photodetector in the visible range: wavelength and power-dependent response studies  

Science.gov (United States)

Photosensitive detector has been reproducibly fabricated using MWCNTs random network-based film grown by chemical vapor deposition technique. For the first time, excellent photoconductive response is reported over the entire green to red band (508-680 nm) of the visible light with maximum efficiency. Wavelength-dependent studies as well as white light exposure confirm the achievement of significant response in the entire visible region which is in commensurate with the absorption spectra of the detection element. The other remarkable novelties of this work are its fast response and recovery time, excellent repeatability and no drift over a time span of 1 year. Besides, there is no local heating effect observed due to photon flux density up to 1,800 lux/m2. The sensing mechanism is explained by interband transition of free carriers, and there is no heat-induced e-h pair generation. The results have opened up the possibility of reproducible fabrication of such device applicable for optical detector or CCD for visible light detection.

Mishra, Prabhash; Harsh; Islam, S. S.

2014-07-01

164

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

International Nuclear Information System (INIS)

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

165

Relative calibration of photodiodes in the soft-X-ray spectral range  

International Nuclear Information System (INIS)

A method of obtaining a relative calibration of Si-photodiodes for the spectral range of soft X-rays (1-30 keV) is presented. A simple mathematical model of the pn-diode is adopted which allows the response to be described in terms of a small set of parameters. The diffusion length as well as the thickness of a dead layer below the front surface of the diodes are obtained from measurements of angular dependences of the photoinduced current. We show that a precise characterisation of the diode response and an accurate relative calibration can be obtained using this method. However, we find that the presence of a dead layer a few tenths of a ?m thick can pose severe restrictions on the use of planar diode arrays in X-ray tomography systems where uniformity of response is crucial. The method has been applied to the diode arrays equipping the X-ray tomography system built for the TCV tokamak, a magnetic fusion research device. (author) 13 figs., 10 refs

166

Frequency range extension of spectral analysis of pulse rate variability based on Hilbert-Huang transform.  

Science.gov (United States)

Heart rate variability (HRV) is a well-accepted indicator for neural regulatory mechanisms in cardiovascular circulation. Its spectrum analysis provides the powerful means of observing the modulation between sympathetic and parasympathetic nervous system. The timescale of HRV is limited by discrete beat-to-beat time intervals; therefore, the exploration region of frequency band of HRV spectrum is relatively narrow. It had been proved that pulse rate variability (PRV) is a surrogate measurement of HRV in most of the circumstances. Moreover, arterial pulse wave contains small oscillations resulting from complex regulation of cardiac pumping function and vascular tone at higher frequency range. This study proposed a novel instantaneous PRV (iPRV) measurement based on Hilbert-Huang transform. Fifteen healthy subjects participated in this study and received continuous blood pressure wave recording in supine and passive head-up tilt. The result showed that the very-high-frequency band (0.4-0.9 Hz) varied during head-up tilt and had strong correlation (r = 0.77) with high-frequency band and medium correlation (r = 0.643) with baroreflex sensitivity. The very-high-frequency band of iPRV helps for the exploration of non-stationary autoregulation and provides the non-stationary spectral evaluation of HRV without distortion or information loss. PMID:24435320

Chang, Chia-Chi; Hsiao, Tzu-Chien; Hsu, Hung-Yi

2014-04-01

167

Nanoscale infrared spectroscopy: improving the spectral range of the photothermal induced resonance technique.  

Science.gov (United States)

Photothermal induced resonance (PTIR) is a new technique which combines the chemical specificity of infrared (IR) spectroscopy with the lateral resolution of atomic force microscopy (AFM). PTIR requires a pulsed tunable laser for sample excitation and an AFM tip to measure the sample expansion induced by light absorption. The limited tunability of commonly available laser sources constrains the application of the PTIR technique to a portion of the IR spectrum. In this work, a broadly tunable pulsed laser relying on a difference frequency generation scheme in a GaSe crystal to emit light tunable from 1.55 ?m to 16 ?m (from 6450 cm(-1) to 625 cm(-1)) was interfaced with a commercial PTIR instrument. The result is a materials characterization platform capable of chemical imaging, in registry with atomic force images, with a spatial resolution that notably surpasses the light diffraction limit throughout the entire mid-IR spectral range. PTIR nanoscale spectra and images allow the identification of compositionally and optically similar yet distinct materials; organic, inorganic, and composite samples can be studied with this nanoscale analog of infrared spectroscopy, suggesting broad applicability. Additionally, we compare the results obtained with the two tunable lasers, which have different pulse lengths, to experimentally assess the recently developed theory of PTIR signal generation. PMID:23363013

Katzenmeyer, Aaron M; Aksyuk, Vladimir; Centrone, Andrea

2013-02-19

168

Improving prediction selectivity for on-line near-infrared monitoring of components in etchant solution by spectral range optimization  

International Nuclear Information System (INIS)

The components (H3PO4, HNO3, CH3COOH and water) in an etchant solution have been accurately measured in an on-line manner using near-infrared (NIR) spectroscopy by directly illuminating NIR radiation through a Teflon line. In particular, the spectral features according to the change of H3PO4 or HNO3 concentrations were not mainly from NIR absorption themselves, but from the perturbation (or displacement) of water bands; therefore, the resulting spectral variations were quite similar to each other. Consequently partial least squares (PLS) prediction selectivity among the components should be the most critical issue for continuous on-line compositional monitoring by NIR spectroscopy. To improve selectivity of the calibration model, we have optimized the calibration models by finding selective spectral ranges with the use of moving window PLS. Using the optimized PLS models for each component, the resulting prediction accuracies were substantially improved. Furthermore, on-line prediction selectivity was evaluated by spiking individual pure components step by step and examining the resulting prediction trends. When optimized PLS models were used, each concentration was selectively and sensitively varied at each spike; meanwhile, when whole or non-optimized ranges were used for PLS, the prediction selectivity was greatly degraded. This study verifies that the selection of an optimal spectral rang the selection of an optimal spectral range for PLS is the most important factor to make Teflon-based NIR measurements successful for on-line and real-time monitoring of etching solutions

169

Spatial distribution of spectral parameters of high latitude geomagnetic disturbances in the Pc5/Pi3 frequency range  

Directory of Open Access Journals (Sweden)

Full Text Available We analyze spectral parameters of the geomagnetic disturbances within the 1–4 mHz (Pc5/Pi3 frequency range for 29 observatories from polar to auroral latitudes. The main object of this study is the broadband (noise background under quiet and moderately disturbed conditions. To obtain a quantitative description of background high-latitude long period ULF activity the log-log dependence of the spectral power on frequency is expanded over Legendre polynomials, and the coefficients of this expansion (spectral moments are used to describe the most common features of these spectra. Not only the spectral power, but also the spectral slope and higher spectral moments, averaged over relatively long time intervals, demonstrate a systematic dependence on corrected geomagnetic (CGM latitude, ?, and magnetic local time, MLT. The 2-D distributions of the spectral moments in ?-MLT coordinates are characterized by existence of structures, narrow in latitude and extended in MLT, which can be attributed to the projections of different magnetospheric domains. Spatio-temporal distributions of spectral power of elliptically (P-component and randomly (N-component polarized signal are similar, but not identical. The N-component contribution to the total signal becomes non-negligible in regions with a high local activity, such as the auroral oval and dayside polar cusp. The spectral slope indicates a larger relative contribution of higher frequencies upon the latitude decrease, probably, as a result of the resonant effects in the ULF noise. The higher spectral moments are also controlled mostly by CGM latitude and MLT and are fundamentally different for the polarized and non-polarized components. This study is a step towards the construction of an empirical model of the ULF wave power in Earth's magnetosphere.

V. A. Pilipenko

2010-09-01

170

Fast and Enhanced Broadband Photoresponse of a ZnO Nanowire Array/Reduced Graphene Oxide Film Hybrid Photodetector from the Visible to the Near-Infrared Range.  

Science.gov (United States)

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

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

2015-04-01

171

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

Science.gov (United States)

We have carried out a search for optically visible post-asymptotic giant branch (post-AGB) candidates in the Small Magellanic Cloud (SMC). First, we used mid-IR observations from the Spitzer Space Telescope to select optically visible candidates with excess mid-IR flux and then we obtained low-resolution optical spectra for 801 of the candidates. After removing poor-quality spectra and contaminants, such as M-stars, C-stars, planetary nebulae, quasi-stellar objects and background galaxies, we ended up with a final sample of 63 high-probability post-AGB/RGB candidates of A-F spectral type. From the spectral observations, we estimated the stellar parameters: effective temperature (Teff), surface gravity (log g) and metallicity ([Fe/H]). We also estimated the reddening and deduced the luminosity using the stellar parameters combined with photometry. For the post-AGB/RGB candidates, we found that the metallicity distribution peaks at [Fe/H] ? -1.00 dex. Based on a luminosity criterion, 42 of these 63 sources were classified as post-red giant branch (post-RGB) candidates and the remaining 21 as post-AGB candidates. From the spectral energy distributions, we were able to infer that 6 of the 63 post-AGB/RGB candidates have a surrounding circumstellar shell suggesting that they are single stars, while 27 of the post-AGB/RGB candidates have a surrounding disc, suggesting that they lie in binary systems. For the remaining 30 post-AGB/RGB candidates the nature of the circumstellar environment was unclear. Variability is displayed by 38 of the 63 post-AGB/RGB candidates with the most common variability types being the Population II Cepheids (including RV-Tauri stars) and semiregular variables. This study has also revealed a new RV Tauri star in the SMC, J005107.19-734133.3, which shows signs of s-process enrichment. From the numbers of post-AGB/RGB stars in the SMC, we were able to estimate evolutionary rates. We find that the number of post-AGB and post-RGB candidates that we have identified are in good agreement with the stellar evolution models with some mass-loss in the post-AGB phase and a small amount of re-accretion in the lower luminosity post-RGB phase. This study also resulted in a new sample of 40 young stellar objects (YSOs) of A-F spectral type. The 40 YSO candidates for which we could estimate stellar parameters are luminous and of high mass (˜3-10 M?). They lie on the cool side of the usually adopted birthline in the HR-diagram. This line separates visually obscured protostars from optically visible pre-main-sequence stars, meaning that our YSO candidates have become optically visible in the region of the HR diagram usually reserved for obscured protostars. Additionally, we also identified a group of 63 objects whose spectra are dominated by emission lines and in some cases, a significant UV continuum. These objects are very likely to be either hot post-AGB/RGB candidates or luminous YSOs.

Kamath, D.; Wood, P. R.; Van Winckel, H.

2014-04-01

172

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

173

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

174

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

175

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

176

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

International Nuclear Information System (INIS)

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

177

Tunable, all-reflective spatial heterodyne spectrometer for broadband spectral line studies in the visible and near-ultraviolet.  

Science.gov (United States)

A spatial heterodyne spectrometer (SHS) is an interferometric device that combines high resolving power and a large input acceptance angle in a compact format suitable for use at small telescope focal planes and spacecraft for observations of faint, angularly extended emission-line sources. The primary limitation of SHS instruments has come from the spatial sampling of their output interference pattern image, which limits their use to a narrow bandpass. We describe the first-light results from a broadband all-reflective SHS that can be mechanically aligned to any heterodyne wavelength from 300 to 700 nm. Such an instrument can be extremely useful for the near simultaneous study of the brightness and line shapes of major atomic and molecular diagnostic emissions from extended astrophysical targets such as comets or planetary atmospheres. We discuss the results of this validation program and the potential improvements that could be used to expand and/or improve the broadband spectral response of the instrument. PMID:19623237

Dawson, Olivia R; Harris, Walter M

2009-07-20

178

Surface compositional mapping by spectral ratioing of ERTS-1 MSS data in the Wind River Basin and Range, Wyoming  

Science.gov (United States)

The author has identified the following significant results. ERTS data collected in August and October 1972 were processed on digital and special purpose analog recognition computers using ratio enhancement and pattern recognition. Ratios of band-averaged laboratory reflectances of some minerals and rock types known to be in the scene compared favorably with ratios derived from the data by ratio normalization procedures. A single ratio display and density slice of the visible channels of ERTS MSS data, Channel 5/Channel 4 (R5,4), separated the Triassic Chugwater formation (redbeds) from other formations present and may have enhanced iron oxide minerals present at the surface in abundance. Comparison of data sets collected over the same area at two different times of the year by digital processing indicated that spectral variation due to environmental factors was reduced by ratio processing.

Vincent, R. K. (principal investigator); Salmon, B. C.; Pillars, W. W.; Harris, J. E.

1975-01-01

179

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

Science.gov (United States)

The paper presents the measurements of linear triatomic carbon opacity (C3) made in a graphite tube furnace to extend the wavelength range of Brewer and Engelke (1962) to the 280-600 nm range. An electrooptical method was used to determine C3 absorption in argon at 2720 to 3060 K; a quartic polynomial regression expression was derived to provide a complete temperature profile from pyrometer measurements. The C3 spectra were plotted for several opacity levels. It was concluded that the extension of the spectral range to the near u.v. levels made it easier to identify C3 particles.

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

1980-01-01

180

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.

181

Broad spectral range measurements and modelling of birefringence dispersion in two-mode elliptical-core fibres  

International Nuclear Information System (INIS)

We present the results of measurement and modelling of the birefringence dispersion in elliptical-core fibres (ECFs). The measurement is performed over a broad wavelength range (e.g. 450–1450 nm) by two spectral interferometric techniques. First, a technique employing a tandem configuration of a Michelson interferometer and an ECF under test is used for a broad spectral range measurement of the group modal birefringence for two spatial modes supported by the fibre. Second, a method with a lateral point-like force acting on the fibre and based on spectral interferometry is used for measuring the phase modal birefringence at one wavelength for the fundamental mode only. The measured value is combined with the dispersion of the group modal birefringence to obtain the phase modal birefringence over a broad wavelength range. We also modelled the dispersion characteristics taking into account contributions of both the elliptical shape of the core and the residual thermal stress. The dispersion characteristics measured for the three ECFs show very good agreement with the results of numerical modelling

182

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

183

Dynamic Sunlight Filter (DSF): a passive way to increase the dynamic range in visible and SWIR cameras  

Science.gov (United States)

Regulating optical power levels within various systems, such as cameras, requires today an electronic feedback control or offline data processing, which introduces complex and expensive systems. Sometimes the blooming is such that data is lost and cannot be recovered by any sophisticated software. We explore the unique capabilities and advantages of nanotechnology in developing next generation non-linear components and devices to control and regulate optical power in a passive way. We report on the Dynamic Sunlight Filter (DSF) enabling High Dynamic Range (HDR) for various types of camera. The DSF solution is completely passive and can be added to any camera as an external add-on.

Donval, A.; Fisher, T.; Blecher, G.; Oron, M.

2010-04-01

184

Full Range Complex Spectral Domain Optical Coherence Tomography for Volumetric Imaging at 47, 000 A Scans per Second  

OpenAIRE

In this paper, we demonstrate a high speed spectral domain optical coherence tomography (SDOCT) system capable of achieving full range complex imaging at 47 kHz line scan rate. By applying 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 detection camera used in the system, system control software is developed that streams the raw ...

An, Lin; Hrebesh, Molly; Wang, Ruikang K.

2010-01-01

185

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

Science.gov (United States)

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.

2013-09-01

186

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

International Nuclear Information System (INIS)

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

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

Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind  

Science.gov (United States)

We measure the power and spectral index anisotropy of magnetic field fluctuations in fast solar wind turbulence from scales larger than the outer scale down to the ion gyroscale, thus covering the entire inertial range. We show that the power and spectral indices above the outer scale of turbulence are approximately isotropic. The turbulent cascade causes the power anisotropy at smaller scales manifested by anisotropic scalings of the spectrum: close to k-5/3 across and k-2 along the local magnetic field, consistent with a critically balanced Alfvénic turbulence. By using data at different radial distances from the Sun and calculating the radial dependence of the ratio of the outer scale to the ion gyroscale, we show that the width of the inertial range does not change with heliocentric distance. At the smallest scales of the inertial range, close to the ion gyroscale, we find an enhancement of power parallel to the magnetic field direction coincident with a decrease in the perpendicular power. This is most likely related to energy injection by ion kinetic modes such as the firehose instability and also marks the beginning of the kinetic range, sometimes called the dissipation range, of solar wind turbulence.

Wicks, R. T.; Horbury, T. S.; Chen, C. H. K.; Schekochihin, A. A.

2010-09-01

189

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

Science.gov (United States)

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

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

2011-08-01

190

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

International Nuclear Information System (INIS)

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

191

A Determination of the Spectral Index of Galactic Synchrotron Emission in the 1-10 GHz range  

CERN Document Server

We present an analysis of simultaneous multifrequency measurements of the Galactic emission in the 1-10 GHz range with 18 degrees, angular resolution taken from a high altitude site. Our data yield a determination of the synchrotron spectral index between 1.4 GHz and 7.5 GHz of 2.81 +/- 0.16. Combining our data with the maps from Haslam et al. (1982) and Reich & Reich (1986) we find 2.76 +/- 0.11 in the 0.4 - 7.5 GHz range. These results are in agreement with the few previously published measurements. The variation of spectral index with frequency based on our results and compared with other data found in the literature suggests a steepening of the synchrotron spectrum towards high frequencies as expected from theory, because of the steepening of the parent cosmic ray electron energy spectrum. Comparison between the Haslam data and the 19 GHz map (Cottingham 1987) also indicates a significant spectral index variation on large angular scale. Addition quality data are necessary to provide a serious study of...

Platania, P; Bersanelli, M; Amici, G D; Kogut, A J; Levin, S; Maino, D; Smoot, G F

1997-01-01

192

High-dynamic-range hybrid analog-digital control broadband optical spectral processor using micromirror and acousto-optic devices.  

Science.gov (United States)

For the first time, to the best of our knowledge, the design and demonstration of a programmable spectral filtering processor is presented that simultaneously engages the power of an analog-mode optical device such as an acousto-optic tunable filter and a digital-mode optical device such as the digital micromirror device. The demonstrated processor allows a high 50 dB attenuation dynamic range across the chosen 1530-1565 nm (~C band). The hybrid analog-digital spectral control mechanism enables the processor to operate with greater versatility when compared to analog- or digital-only processor designs. Such a processor can be useful both as a test instrument in biomedical applications and as an equalizer in fiber communication networks. PMID:18516181

Riza, Nabeel A; Reza, Syed Azer

2008-06-01

193

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

Science.gov (United States)

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

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

2011-09-01

194

Range-gated LADAR coherent imaging using parametric up-conversion of IR and NIR light for imaging with a visible-range fast-shuttered intensified digital CCD camera  

Science.gov (United States)

Research is presented on infrared (IR) and near infrared (NIR) sensitive sensor technologies for use in a high speed shuttered/intensified digital video camera for range-gated imaging at eye-safe wavelengths in the region of 1.5 microns. The study is based upon nonlinear crystals used for second harmonic generation (SHG) in optical parametric oscillators (OPOs) for conversion of NIR and IR laser light to visible range light for detection with generic S-20 photocathodes. The intensifiers are stripline geometry 18-mm diameter microchannel plate intensifiers (MCPIIs), designed by Los Alamos National Laboratory and manufactured by Philips Photonics. The MCPIIs are designed for fast optical shuttering with exposures and resolution for the wavelength conversion process are reported. Experimental set-ups for the wavelength shifting and the optical configurations for producing and transporting laser reflectance images are discussed.

Yates, George J.; McDonald, Thomas E., Jr.; Bliss, David E.; Cameron, Stewart M.; Zutavern, Fred J.; Zagarino, Paul A.

2001-04-01

195

Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind  

CERN Document Server

We measure the power and spectral index anisotropy of high speed solar wind turbulence from scales larger than the outer scale down to the ion gyroscale, thus covering the entire inertial range. We show that the power and spectral indices at the outer scale of turbulence are approximately isotropic. The turbulent cascade causes the power anisotropy at smaller scales manifested by anisotropic scalings of the spectrum: close to k^{-5/3} across and k^{-2} along the local magnetic field, consistent with a critically balanced Alfvenic turbulence. By using data at different radial distances from the Sun, we show that the width of the inertial range does not change with heliocentric distance and explain this by calculating the radial dependence of the ratio of the outer scale to the ion gyroscale. At the smallest scales of the inertial range, close to the ion gyroscale, we find an enhancement of power parallel to the magnetic field direction coincident with a decrease in the perpendicular power. This is most likely ...

Wicks, R T; Chen, C H K; Schekochihin, A A

2010-01-01

196

Caller sex and orientation influence spectral characteristics of "two-voice" stereotyped calls produced by free-ranging killer whales.  

Science.gov (United States)

This study investigates how particular received spectral characteristics of stereotyped calls of sexually dimorphic adult killer whales may be influenced by caller sex, orientation, and range. Calls were ascribed to individuals during natural behavior using a towed beamforming array. The fundamental frequency of both high-frequency and low-frequency components did not differ consistently by sex. The ratio of peak energy within the fundamental of the high-frequency component relative to summed peak energy in the first two low-frequency component harmonics, and the number of modulation bands off the high-frequency component, were significantly greater when whales were oriented towards the array, while range and adult sex had little effect. In contrast, the ratio of peak energy in the first versus second harmonics of the low-frequency component was greater in calls produced by adult females than adult males, while orientation and range had little effect. The dispersion of energy across harmonics has been shown to relate to body size or sex in terrestrial species, but pressure effects during diving are thought to make such a signal unreliable in diving animals. The observed spectral differences by signaler sex and orientation suggest that these types of information may be transmitted acoustically by freely diving killer whales. PMID:17552739

Miller, Patrick J O; Samarra, Filipa I P; Perthuison, Aurélie D

2007-06-01

197

Emissivity and reflectance measurements of 10 meteoritic analogues in the 1 to 100 ?m spectral range, from PEL  

Science.gov (United States)

We have measured the emissivity and reflectance spectra for a suite of analogues of relevance for asteroid studies. The suite consists of ten samples - 3 meteorites and 7 synthetic or terrestrial analogue materials. Meteorite Allende represents the CV group of the Carbonaceous Chondrites meteorites; Murchison meteorite is representing the CM group, while the meteorite Millbillillie represents achondritic eucrites. Synthetic and terrestrial enstatite, synthetic L-Chondrite and H-Chondrite, graphite and two phyllosilicates (montmorillonite and serpentine) complete the set of analogues. In the Planetary Emissivity Laboratory (PEL) at the Institute for Planetary Research of the German Aerospace Center (DLR) in Berlin, we can measure bi-directional reflectance of samples in the whole 1 to 100 ?m spectral range, by using an evacuated (10-4 bar) Bruker Vertex 80V FTIR spectrometer and a Bruker A513 reflection unit, allowing phase angles between 26° and 170°. The same instrument, coupled with an external emissivity chamber, can be used to measure emissivity of samples under the same vacuum and in the same wide spectral range, for sample temperatures from low (50° C) to very high (above 500° C). Complementary purged Bruker IFS88 FTIR spectrometer equipped with a Harrick SeagullTM bi-conical reflection unit permits to cover the 0.4 to 1.1 ?m spectral range. For this study, when possible we measured the smaller available grain size separate (0-25 ?m) and kept the sample temperature to the minimum we could get. Our results can be important for support of future (sample return) missions to asteroids (i.e. Hayabusa II, MarcoPolo-R and OSIRIS-REx) as well as for the interpretation of ground based observations of asteroids and minor bodies.

Maturilli, A.; Helbert, J.; D'Amore, M.

2012-12-01

198

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

199

WDM/TDM PON experiments using the AWG free spectral range periodicity to transmit unicast and multicast data.  

Science.gov (United States)

A hybrid WDM/TDM PON architecture implemented by means of two cascaded Arrayed Waveguide Gratings (AWG) is presented. Using the Free Spectral Range (FSR) periodicity of AWGs we transmit unicast and multicast traffic on different wavelengths to each Optical Network Unit (ONU). The OLT is equipped with two laser stacks, a tunable one for unicast transmission and a fixed one for multicast transmission. We propose the ONU to be reflective in order to avoid any light source at the Costumer Premises Equipment (CPE). Optical transmission tests demonstrate correct transmission at 2.5 Gbps up to 30 km. PMID:19495184

Bock, Carlos; Prat, Josep

2005-04-18

200

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

OpenAIRE

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 ...

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

2012-01-01

201

Flow-radiated noise. Study of the propagative spectral range of the wall pressure field  

Science.gov (United States)

The complete model of the wall pressure field developed here incorporates many experimentally observed and proven partial similarities, as well as hypotheses to offset experimental gaps in certain frequency ranges and wave numbers. Initial comparisons show good agreement with experimental results across a wide range of frequencies and wave numbers. The main advantages of the model are: non-dependent adjustment constants; the explicit dependence of local, boundary layer scales; the explicit formulation of physical scales that control the similarity of frequencies and levels; incorporation of the whole range of frequencies and wave numbers; complete determination of the spectrum and interspectrum; and calculation of the root mean square. The study's acoustical range model explains the asymptotic behavior of the low-frequency spectrum, by separating incompressible and acoustic factors. This can be used to calculate the share of wall pressure fluctuations migrating in the form of a sound wave, thus providing an essential element in the problem of antenna or SONAR dome set noise and radiated noise.

Benarrous, E.

202

A new generation of dyes in the 688-860-nm spectral range for laser excitation  

Science.gov (United States)

The generation characteristics of a new class of dyes under laser pumping were investigated. It is shown that these new dyes are more efficient than those used previously in the near-IR range both under ruby-laser (694-nm) pumping and N2-laser (337-nm) pumping. The high photostability of these dyes is noted.

Stepanov, B. I.; Bychkov, N. N.; Levshin, L. V.; Konstantinov, B. A.; Akimov, A. I.

1988-04-01

203

Generation of surface electromagnetic waves in terahertz spectral range by free-electron laser radiation and their refractive index determination  

International Nuclear Information System (INIS)

First experiments for observation of surface electromagnetic waves (SEW) in the terahertz spectral range generated on dense aluminum films covering the optical quality glass plates are presented in this paper. Coherent radiation of the new free-electron laser covering the frequency range from 30 to 100cm-1 was used. The interference technique employing SEW propagation in the part of one shoulder of the asymmetric interferometer was applied. From the interference pattern the real part of SEW's effective refractive index ae' was determined for the two laser emission wavelengths: at ?=150?m-ae'=1+5x10-5, at ?=110?m-ae'=1+8x10-4. High sensitivity of the interference patterns to overlayers made of Ge and Si with thickness of 100nm was demonstrated as well

204

Temperature-dependent dielectric function of germanium in the UV–vis spectral range: A first-principles study  

International Nuclear Information System (INIS)

The study of temperature dependence of thermophysical parameter dielectric function is key to understanding thermal radiative transfer in high-temperature environments. Limited by self-radiation and thermal oxidation, however, it is difficult to directly measure the high-temperature dielectric function of solids with present experimental technologies. In this work, we implement two first-principles methods, the ab initio molecular dynamics (AIMD) and density functional perturbation theory (DFPT), to study the temperature dependence of dielectric function of germanium (Ge) in the UV–vis spectral range in order to provide data of high-temperature dielectric function for radiative transfer study in high-temperature environments. Both the two methods successfully predict the temperature dependence of dielectric function of Ge. Moreover, the good agreement between the calculated results of the AIMD approach and experimental data at 825 K enables us to predict the high-temperature dielectric function of Ge with the AIMD method in the UV–vis spectral range. - Highlights: • The temperature dependence of dielectric function of germanium (Ge) is investigated with two first-principles methods. • The temperature effect on dielectric function of Ge is discussed. • The high-temperature dielectric function of Ge is predicted

205

Emitting far-field multicolor patterns and characters through plastic diffractive micro-optics elements illuminated by common Gaussian lasers in the visible range.  

Science.gov (United States)

Far-field multicolor patterns and characters are emitted effectively in a relatively wide and deep spatial region by plastic diffractive micro-optics elements (DMOEs), which are illuminated directly by common Gaussian lasers in the visible range. Phase-only DMOEs are composed of a large number of fine step-shaped phase microstructures distributed sequentially over the plastic wafer selected. The initial DMOEs in silicon wafer are fabricated by an innovative technique with a combination of a single-mask ultraviolet photolithography and low-cost and rapid wet KOH etching. The fabricated silicon DMOEs are further converted into a nickel mask by the conventional electrochemical method, and they are finally transferred onto the surface of the plastic wafer through mature hot embossing. Morphological measurements show that the surface roughness of the plastic DMOEs is in the nanometer range, and the feature height of the phase steps in diffractive elements is in the submicrometer scale, which can be designed and adjusted flexibly according to requirements. The dimensions of the DMOEs can be changed from the order of millimeters to centimeters. A large number of pixel phase microstructures with a square microappearance employed to construct the phase-only DMOEs are created by the Gerchberg-Saxton algorithm, according to the target patterns and characters and common Gaussian lasers manipulated by the DMOEs fabricated. PMID:21478971

Zhang, Xinyu; Li, Hui; Liu, Kan; Luo, Jun; Xie, Changsheng; Ji, An; Zhang, Tianxu

2011-04-01

206

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

Science.gov (United States)

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.

Bobrowski, N.; Kern, C.; Platt, U.; Hörmann, C.; Wagner, T.

2010-07-01

207

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

208

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

209

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

International Nuclear Information System (INIS)

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

210

Spectral EMG changes in vastus medialis muscle following short range of motion isokinetic training.  

Science.gov (United States)

This study was aimed at exploring the carryover effect of short range of motion (RoM) isokinetic conditioning on vastus medialis (VM) motor unit recruitment (MUR) across the full RoM. Fifty-five women were randomly assigned to one of four groups: G1 (n = 14) and G2 (n = 14) trained concentrically at 30 and 90 degrees /s, respectively whereas G3 (n = 13) and G4 (n = 14) trained similarly but using the eccentric mode. All 4 groups trained within 30-60 degrees of knee flexion. The training protocol consisted of 4 sets of 10 maximal repetitions, 3 times a week for 6 weeks. sEMG was recorded from the VM for analysis of mean frequency of the EMG power spectrum prior to the training period and 2 days after its termination. The EMG assessments took place during dynamic contractions within 3 angular RoM's: 85-60 degrees (R1), 60-30 degrees (R2) and 30-5 degrees (R3). In addition MUR was evaluated during isometric contractions at 10 degrees , 45 degrees and 80 degrees . Significant increases were observed in the MUR at R1, R2, and R3 during dynamic contractions as well as in all 3 angles during isometric contractions. These findings applied equally regardless of the mode of contraction and motion speed during training. The fact that MUR increased significantly within untrained RoM's may point out to the potential benefits of short RoM conditioning, particularly in those cases where, during specific phases of rehabilitation, a wider RoM may be contraindicative. PMID:16324851

Barak, Yaron; Ayalon, Moshe; Dvir, Zeevi

2006-10-01

211

Viewer Makes Radioactivity "Visible"  

Science.gov (United States)

Battery operated viewer demonstrates feasibility of generating threedimensional visible light simulations of objects that emit X-ray or gamma rays. Ray paths are traced for two pinhold positions to show location of reconstructed image. Images formed by pinholes are converted to intensified visible-light images. Applications range from radioactivity contamination surveys to monitoring radioisotope absorption in tumors.

Yin, L. I.

1983-01-01

212

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

Science.gov (United States)

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

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

2015-01-01

213

Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers.  

Science.gov (United States)

A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm(-1) to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ~70 as. The anharmonicity of smaller than 10(-4) cm(-1) was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 ?rad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy. PMID:25173248

Leger, Joel D; Nyby, Clara M; Varner, Clyde; Tang, Jianan; Rubtsova, Natalia I; Yue, Yuankai; Kireev, Victor V; Burtsev, Viacheslav D; Qasim, Layla N; Rubtsov, Grigory I; Rubtsov, Igor V

2014-08-01

214

Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers  

Energy Technology Data Exchange (ETDEWEB)

A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm{sup ?1} to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ?70 as. The anharmonicity of smaller than 10{sup ?4} cm{sup ?1} was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 ?rad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy.

Leger, Joel D.; Nyby, Clara M.; Varner, Clyde; Tang, Jianan; Rubtsova, Natalia I.; Yue, Yuankai; Kireev, Victor V.; Burtsev, Viacheslav D.; Qasim, Layla N.; Rubtsov, Igor V., E-mail: irubtsov@tulane.edu [Department of Chemistry, Tulane University, New Orleans, Louisiana 70118 (United States); Rubtsov, Grigory I. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312 (Russian Federation)

2014-08-15

215

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

International Nuclear Information System (INIS)

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

216

Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers  

International Nuclear Information System (INIS)

A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm?1 to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ?70 as. The anharmonicity of smaller than 10?4 cm?1 was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 ?rad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy

217

Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers  

Science.gov (United States)

A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm-1 to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ˜70 as. The anharmonicity of smaller than 10-4 cm-1 was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 ?rad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy.

Leger, Joel D.; Nyby, Clara M.; Varner, Clyde; Tang, Jianan; Rubtsova, Natalia I.; Yue, Yuankai; Kireev, Victor V.; Burtsev, Viacheslav D.; Qasim, Layla N.; Rubtsov, Grigory I.; Rubtsov, Igor V.

2014-08-01

218

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

219

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

220

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

221

Chlorine detection in cement with laser-induced breakdown spectroscopy in the infrared and ultraviolet spectral range  

International Nuclear Information System (INIS)

A significant parameter to monitor the status of concrete buildings like bridges or parking garages is the determination of the depth profile of the chlorine concentration below the exposed concrete surface. This information is required to define the needed volume of restoration for a construction. Conventional methods like wet chemical analysis are time- and cost-intensive so an alternative method is developed using laser-induced breakdown spectroscopy (LIBS). The idea is to deploy LIBS to analyze drill cores by scanning the sample surface with laser pulses. Chlorine spectral lines in the infrared (IR) and ultraviolet (UV)-range were studied for chlorine detection in hydrated cement samples. The excitation energies of these spectral lines are above 9.2 eV. Hence high plasma temperatures and pulse energies in the range of some hundred millijoules are needed to induce sufficient line intensity levels at the required working distance. To further increase the line intensity and to lower the detection limit (LOD) of chlorine a measuring chamber is used where different ambient pressures and gases can be chosen for the measurements. The influences on the line intensity for pressures between 5 mbar and 400 mbar using helium as process gas and the influence of different laser burst modi like single and collinear double pulses are investigated. For the first time a LOD according to DIN 32 645 of 0.1 mass% was achieved for chlorine in hydrated cement using the UV line 134.72 nmydrated cement using the UV line 134.72 nm.

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.

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

2014-08-01

225

Tunable diode lasers based on quaternary III-V alloys in the spectral range of 2-4 µm for laser spectroscopy applications  

OpenAIRE

The structures and electroluminescence characteristics of new two types of single mode A3B5 semiconductor tunable lasers in the 1.8-3.9 µm spectral range have been demonstrated. The first type of tunable diode laser based on quaternary solid solutions GaInAsSb and GaAlAsSb lattice matched to GaSb substrate covers 1.8-2.4 µm spectral range. Such tunable 1.8-2.4 µm lasers have single mode or quasi- single mode operation in the wide temperature range from 1.6 to 300K. The second type of tunab...

Yakovlev, Yu; Baranov, A.; Imendov, A.; Popov, A.; Sherstnev, V.

1994-01-01

226

A new facility for the synchrotron radiation-based calibration of transfer radiation sources in the ultraviolet and vacuum ultraviolet spectral range  

Science.gov (United States)

The Physikalisch-Technische Bundesanstalt (PTB) has a long tradition in the calibration of radiation sources in the ultraviolet and vacuum ultraviolet spectral range, with traceability to calculable synchrotron radiation. Within this context, new instrumentation in the PTB laboratory at the Metrology Light Source (MLS) has been put into operation that opens up extended and improved calibration possibilities. A new facility for radiation source calibrations has been set up in the spectral range from 7 nm to 400 nm based on a combined normal incidence-grazing incidence monochromator. The facility can be used for the calibration of transfer sources in terms of spectral radiant intensity or mean spectral radiance, with traceability to the MLS primary source standard. We describe the design and performance of the experimental station and give examples of some commissioning results.

Thornagel, Reiner; Fliegauf, Rolf; Klein, Roman; Kroth, Simone; Paustian, Wolfgang; Richter, Mathias

2015-01-01

227

A new facility for the synchrotron radiation-based calibration of transfer radiation sources in the ultraviolet and vacuum ultraviolet spectral range.  

Science.gov (United States)

The Physikalisch-Technische Bundesanstalt (PTB) has a long tradition in the calibration of radiation sources in the ultraviolet and vacuum ultraviolet spectral range, with traceability to calculable synchrotron radiation. Within this context, new instrumentation in the PTB laboratory at the Metrology Light Source (MLS) has been put into operation that opens up extended and improved calibration possibilities. A new facility for radiation source calibrations has been set up in the spectral range from 7 nm to 400 nm based on a combined normal incidence-grazing incidence monochromator. The facility can be used for the calibration of transfer sources in terms of spectral radiant intensity or mean spectral radiance, with traceability to the MLS primary source standard. We describe the design and performance of the experimental station and give examples of some commissioning results. PMID:25638071

Thornagel, Reiner; Fliegauf, Rolf; Klein, Roman; Kroth, Simone; Paustian, Wolfgang; Richter, Mathias

2015-01-01

228

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

229

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

OpenAIRE

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...

Makarov, D. V.; Kon Kov, L. E.; Uleysky, M. Yu; Petrov, P. S.

2012-01-01

230

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)

231

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

232

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

233

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

234

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

235

Free spectral range optimization of return-to-zero differential phase-shift keyed demodulation in 40 Gbit/s nonlinear transmission.  

Science.gov (United States)

For differential decoding, direct detection of DPSK signal needs a delay line interferometer with a free spectral range normally equal to the transmitted bit-rate. We numerically demonstrate that free spectral range optimization can increase tolerance to fiber Kerr nonlinearities for 40 Gbit/s RZ-DPSK transmission, especially for multi-format (RZ-DPSK and RZ-OOK) systems, in which Kerr nonlinearities is quite serious mainly due to cross-phase modulation. The optimal delay time of the delay line interferometer in DPSK signal demodulation is shorter than one bit-period. Joint optimization of free spectral range and optical filter bandwidth will further enhance system tolerance to nonlinear transmission. PMID:18542285

Li, Xiaolin; Zhang, Fan; Zhang, Xiaoru; Zhang, Dechao; Chen, Zhangyuan; Xu, Anshi

2008-02-01

236

Spectral Imaging by Upconversion  

OpenAIRE

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

Dam, Jeppe Seidelin; Pedersen, Christian; Tidemand-lichtenberg, Peter

2011-01-01

237

Spectral Imaging by Upconversion  

DEFF Research Database (Denmark)

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

Dam, Jeppe Seidelin; Pedersen, Christian

2011-01-01

238

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

239

Atlas and wavenumber tables for visible part of the rovibronic multiline emission spectrum of the $D_2$ molecule. II. Wavenumber range $18161 \\div 14379$ cm$^{-1}$ measured with moderate resolution  

CERN Document Server

The visible part ($\\approx 550 \\div 696$ nm) of the multiline electronic-vibro-rotational emission spectrum of the $D_2$ molecule was recorded with moderate resolution (line widths $\\approx 0.013$ nm). The resolution was limited by Doppler broadening of spectral lines. After numerical deconvolution of the recorded intensity distributions and proper calibration of the spectrometer the new set of wavenumber values was obtained. The results are reported in the form of an atlas divided into 43 sections covering about 1.5 nm, containing pictures of images in the focal plane of the spectrometer, intensity distributions in linear and logarithmic scales and the table containing wavenumber and relative intensity values for 5445 spectral lines together with existing line assignments.

Lavrov, B P

2012-01-01

240

Atlas and wavenumber tables for visible part of the rovibronic multiline emission spectrum of the $D_2$ molecule. I. Wavenumber range $23894 \\div 18161$ cm$^{-1}$ measured with moderate resolution  

CERN Document Server

The visible part ($\\approx 419 \\div 550$ nm) of the multiline electronic-vibro-rotational emission spectrum of the $D_2$ molecule was recorded with moderate resolution (line widths $\\approx 0.013$ nm). The resolution was limited by Doppler broadening of spectral lines. After numerical deconvolution of the recorded intensity distributions and proper calibration of the spectrometer the new set of wavenumber values was obtained. The results are reported in the form of an atlas divided into 36 sections covering about 1.5 nm, containing pictures of images in the focal plane of the spectrometer, intensity distributions in linear and logarithmic scales and the table containing wavenumber and relative intensity values for 6545 spectral lines together with existing line assignments.

Lavrov, B P

2012-01-01

241

Wavelength dispersion measurement of electro-optic coefficients in the range of 520 to 930 nm in rubidium titanyl phosphate using spectral interferometry.  

Science.gov (United States)

Rubidium titanyl phosphate (RTP) is widely used for electro-optical applications at low switching voltages. RTP is nonhygroscopic and does not induce piezoelectric ringing up to the megahertz range. It has large electro-optic (EO) coefficients and a high damage threshold. We present here the EO coefficient wavelength dispersion measurements in the [550,950] nm spectral range using a method based on spectral interferometry. These data are necessary for, among other things, a quantitative modelization of an EO carrier-envelope phase shifter. PMID:22330291

Gobert, Olivier; Fedorov, Nikita; Mennerat, Gabriel; Lupinski, Dominique; Guillaumet, Delphine; Perdrix, Michel; Bourgeade, Antoine; Comte, Michel

2012-02-10

242

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

Science.gov (United States)

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

243

Visible Embryo  

Science.gov (United States)

a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-01-30

244

Radiometric measurements in the spectral range of far ultraviolet radiation for diagnostics of fusion and electron cyclotron resonance plasmas  

International Nuclear Information System (INIS)

The radiation losses from 18 prominent spectral lines of carbon and oxygen in the range of 150-1200 A emitted from the tokamak ASDEX have been measured absolutely using VUV-spectrometers calibrated with a radiometric standard based on electron impact induced line emission from gases. These lines represent a power loss PVUV=131.5 kW which has to be compared with the bolometrically determined radiation loss PRAD=150 kW and the total ohmic input power POH=440 kW. About one third of the radiation loss was found in the O VI2s2S-2p2P-doublet at 1032 A and 1037.6 A. Moreover the measurements enabled us to determine the density of Be-like C III and O V ions in the metastable triplet system relative to the ground state density. About one half of these Be-like ions was found in the metastable 2s2p3P state. In the plasma model used at ASDEX the density and temperature profiles were improved, especially the steep gradients at the plasma edge. The rate coefficients for electron impact ionisation and excitation were examined and with improved excitation rate coefficients the number of calculable line intensities was extended. A comparison of experimental line intensity ratios with model calculations was used as a test for the reliability of the plasma model in the important plasma edge region. Impurity concentrations and fluxes were determined. Finally we have investigated selected line intensity ratios emitted from an Electron Cyclotron Resonance Ion Source and made an attempt to determine the electron density as a function of the neutral gas pressure in the second stage of the ECR. (orig.)

245

Optical absorption behaviour of platinum core-silica shell nanoparticle layer and its influence on the reflection spectra of a multi-layer coating system in the visible spectrum range  

International Nuclear Information System (INIS)

Platinum core-silica shell nanoparticles (Pt-SiO2) have been applied to the outermost layer of a three-layer film structure to yield a Pt-SiO2/SiO2/ITO (indium tin oxide) coating on a glass substrate. Optical properties of the three-layer film have been investigated in the visible spectrum regime. The absorption of visible light by the Pt core-SiO2 shell layer was higher in low- and high-wavelength regimes while it was minimal at a mid-visible light range, about 550 nm. This characteristic absorption of the core-shell layer resulted in a broad-band anti-reflectance behaviour of the multi-layer coating system in the entire visible light regime. Transmittance of the three-layer coating-glass system was in the range between 80% and 85% and thus the application of the platinum core-silica shell nanoparticle layer with such absorption characteristics is shown to provide flexibility of ways to achieve a broad-band anti-reflectance and transmittance of a multi-layer coating system

246

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

International Nuclear Information System (INIS)

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

247

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.)

248

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 [Symbol: see text] = 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. PMID:23383791

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

2013-01-01

249

Spectral reflectance of carbonate minerals and rocks in the visible and near infrared (0.35 - 2.55 microns) and its applications in carbonate petrology  

Science.gov (United States)

Reflection spectroscopy in the visible and near infrared (0.35 to 2.55 micron) offers a rapid, inexpensive, nondestructive tool for determining the mineralogy and investigating the minor element chemistry of the hard-to-discriminate carbonate minerals, and can, in one step, provide information previously obtainable only by the combined application of two or more analytical techniques. When light interacts with a mineral certain wavelengths are preferentially absorbed. The number, positions, widths and relative intensities of these absorptions are diagnostic of the mineralogy and chemical composition of the sample. At least seven bands due to vibrations of the carbonate radical occur between 1.60 and 2.55 micron. Positions of these bands vary from one carbonae mineral to another and can be used for mineral identification. Cation mass is the primary factor controlling band position; cation radius plays a secondary role.

Gaffey, S. J.

1984-01-01

250

Influence of the number of atomic levels on the spectral opacity of low temperature nickel and iron in the spectral range 50-300 eV  

International Nuclear Information System (INIS)

Opacity is a fundamental ingredient for the secular evolution of stars. The calculation of the stellar plasma absorption coefficients is complex due to the composition of these plasmas, generally an H /He dominated mixture with a low concentration of partially ionized heavy ions (the iron group). The international collaboration OPAC recently presented extensive comparisons of spectral opacities of iron and nickel for temperatures between 15 and 40 eV and for densities of ? 3 mg/cm3, relevant to the stellar envelope conditions [1, 2]. The role of Configuration Interaction (CI) and the influence of the number of atomic levels on the opacity using the recently improved version of HULLAC atomic code [3, 4] are illustrated in this article. Comparisons with theoretical predictions already presented in [1] are discussed. (authors)

251

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

DEFF Research Database (Denmark)

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

Alberti, Michael; Weber, Roman

2015-01-01

252

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

Energy Technology Data Exchange (ETDEWEB)

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.

Gerhard, Sven

2013-01-10

253

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

254

Spectral slope of high-latitude geomagnetic disturbances in the frequency range 1-5 mHz. Control parameters inside and outside the magnetosphere  

Science.gov (United States)

Dependence of the spectral slope of long-period high-latitude Pc5/ Pi3(1-5 mHz) geomagnetic variations on parameters of the interplanetary geomagnetic field and plasma in front of the bow shock and in the magnetosheath is analyzed for different intervals of the local magnetic time. It is shown that, contrary to the power spectral density, for which the coherent variations on 103 km scales are controlled by the plasma parameters in front of the bow shock, coherent variations of the spectral slope are controlled by processes in the magnetosheath. The relation between the spectral slope at geomagnetic latitudes ? > 73° and the parameters of the magnetic field in the magnetosheath was established. Thus, the spectral slope of high latitude disturbances in the 1-5 mHz frequency range reflects processes in the magnetosheath, far from the subsolar point, and cannot be predicted with only an analysis of parameters in the interplanetary media in front of the bow shock.

Yagova, N. V.

2015-01-01

255

The Swift-UVOT ultraviolet and visible grism calibration  

CERN Document Server

We present the calibration of the Swift UVOT grisms, of which there are two, providing low-resolution field spectroscopy in the ultraviolet and optical bands respectively. The UV grism covers the range 1700-5000 Angstrom with a spectral resolution of 75 at 2600 Angstrom for source magnitudes of u=10-16 mag, while the visible grism covers the range 2850-6600 Angstrom with a spectral resolution of 100 at 4000 Angstrom for source magnitudes of b=12-17 mag. This calibration extends over all detector positions, for all modes used during operations. The wavelength accuracy (1-sigma) is 9 Angstrom in the UV grism clocked mode, 17 Angstrom in the UV grism nominal mode and 22 Angstrom in the visible grism. The range below 2740 Angstrom in the UV grism and 5200 Angstrom in the visible grism never suffers from overlapping by higher spectral orders. The flux calibration of the grisms includes a correction we developed for coincidence loss in the detector. The error in the coincidence loss correction is less than 20%. The...

Kuin, N P M; Breeveld, A A; Page, M J; James, C; Lamoureux, H; Mehdipour, M; Still, M; Yershov, V; Brown, P J; Carter, M; Mason, K O; Kennedy, T; Marshall, F; Roming, P W A; Siegel, M; Oates, S; Smith, P J; De Pasquale, M

2015-01-01

256

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

257

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

International Nuclear Information System (INIS)

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

258

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

International Nuclear Information System (INIS)

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

259

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

260

Spectral ellipsometry study in the range of electronic excitations and band structure of [(CH3)2CHNH3]4Cd3Cl10 crystals  

International Nuclear Information System (INIS)

Optical dielectric functions ?(E) of the (IPA)4Cd3Cl10 crystal were measured in the spectral range of fundamental electronic excitations 3.5–10 eV and in the temperature range of 310–400 K containing the phase transition point between the orthorhombic phases Cmce and Pbca. Measurements were performed by spectroscopic ellipsometry with using of synchrotron radiation. Electronic band structure, density of states and dielectric functions ?(E) of (IPA)4Cd3Cl10 were calculated and analyzed on the basis of the density functional theory. Top valence and bottom conduction bands were found to be formed mainly by the cadmium–chlorine complexes of the crystals. - Highlights: ? Spectral ellipsometry in the VUV range is used for study of (IPA)4Cd3Cl10 crystals. ? Band structure of (IPA)4Cd3Cl10 crystal has been calculated for the first time. ? Origin of the lowest energy spectral band of dielectric function is determined. ? Width of temperature dependency of dielectric permittivity is large (near 50 K). ? Maximum of temperature dependency of dielectric permittivity is small (near 2%)

261

Investigation of yttrium aluminium garnet in the spectral range of 2-20.5 eV  

International Nuclear Information System (INIS)

The spectral dependences of optical absorption, reflection and emission, photoelectron emission and photoconductivity in the fundamental absorption region of yttrium aluminium garnet (YAG) are presented. The intrinsic luminescence of YAG has been observed with the emission band maximum shifting from 3.95 eV at 300 K to 4.68 eV at 80 K. A conclusion has been drawn about the existence of nonconducting excited electron states, arrived at by electron transitions in the (AlO4)5- groups in the YAG lattice. The intrinsic luminescence of YAG is ascribed to the same (AlO4)5- groups

262

Spectrally adjustable quasi-monochromatic radiance source based on LEDs and its application for measuring spectral responsivity of a luminance meter  

International Nuclear Information System (INIS)

A spectrally adjustable radiance source based on light-emitting diodes (LEDs) has been constructed for spectral responsivity measurements of radiance and luminance meters. A 300 mm integrating sphere source with adjustable output port is illuminated using 30 thermally stabilized narrow-band LEDs covering the visible wavelength range of 380–780 nm. The functionality of the measurement setup is demonstrated by measuring the relative spectral responsivities of a luminance meter and a photometer head with cosine-corrected input optics. (paper)

263

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

International Nuclear Information System (INIS)

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

264

Examining the possibility of correcting imagery acquired for the purpose of obtaining spectral reflectance coefficients in the infrared range using photometric measurements  

Science.gov (United States)

The purpose of this paper is to determine the possibility of using photometric measurements in order to correct imagery acquired in the 900-1700 nm range. This imagery is acquired for the purpose of acquiring spectral reflectance coefficients in variable lighting conditions. This paper will present a series of experiments, the problems encountered and obtained results. The main aim of this research was to determine a link between these two quantities (luminance and irradiance) in order to be able to eliminate the need of using such a spectroradiometer (a large, heavy and costly instrument) when acquiring spectral reflectance data from a XEVA XS-1.7.320 camera mounted on an UAV without using a reference panel.

Orych, A.; Walczykowski, P.; Kedzierski, M.; Fryskowska, A.

2014-11-01

265

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

266

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

267

Transmittance and optical constants of Lu films in the 3-1800 eV spectral range  

OpenAIRE

The optical constants n and k of lutetium (Lu) films were obtained in the 3-1800 eV range from transmittance measurements performed at room temperature. These are the first experimental optical constant data of Lu in the whole range. Thin films of Lu with various thicknesses were deposited by evaporation in ultrahigh vacuum conditions and their transmittance was measured in situ. Lu films were deposited onto grids coated with a thin, C support film. Transmittance measurements were used to obt...

Garci?a-corte?s, S.; Rodri?guez-de Marcos, L.; Larruquert, Juan Ignacio; Azna?rez, Jose? Antonio; Me?ndez, Jose? Antonio; Poletto, L.; Frassetto, F.; Malvezzi, A. M.; Giglia, A.; Mahne, N.; Nannarone, S.

2010-01-01

268

? and fission-reactor radiation effects on the visible-range transparency of aluminum-jacketed, all-silica optical fibers  

International Nuclear Information System (INIS)

Four aluminum-jacketed, fluorine-doped silica clad optical fibers with silica core materials fabricated by differing technologies were subjected to sequential 60Co-? ray and fission-reactor irradiations (at ?20 and 40 degree C, respectively), an intervening isothermal anneal (?20 degree C), and a final isochronal anneal (to 600 degree C) while monitoring the radiation-induced absorption spectra in the range ?400 endash 1000 nm. The two low-OH/low-chloride core fibers (one of which was doped with 0.5 mass% fluorine) both developed bands at 660 and 760 nm which exceeded 10000 dB/km for doses in the range ?102 endash 106 Gy(Si); however, these bands declined to 16 cm-2] were much less sensitive to fiber core material. The prospects for developing rad hard optical fibers for fusion reactor diagnostics are discussed in light of these findings

269

? and fission-reactor radiation effects on the visible-range transparency of aluminum-jacketed, all-silica optical fibers  

Science.gov (United States)

Four aluminum-jacketed, fluorine-doped silica clad optical fibers with silica core materials fabricated by differing technologies were subjected to sequential 60Co-? ray and fission-reactor irradiations (at ˜20 and 40 °C, respectively), an intervening isothermal anneal (˜20 °C), and a final isochronal anneal (to 600 °C) while monitoring the radiation-induced absorption spectra in the range ˜400-1000 nm. The two low-OH/low-chloride core fibers (one of which was doped with 0.5 mass % fluorine) both developed bands at 660 and 760 nm which exceeded 10 000 dB/km for doses in the range ˜102-106 Gy(Si); however, these bands declined to range ˜600-630 nm generally attributed to nonbridging-oxygen hole centers (NBOHCs). During the ?-irradiation phase the strengths of the NBOHC bands proved to be strongly dependent on the method of core material manufacture. Contrary to previous results for acrylate-jacketed fibers, no substantial bleaching of the UV-tail or NBOHC bands took place during ? irradiation despite the continuous propagation of white light powers ˜5-50 ?W. The incremental induced absorption spectra consequent to the reactor-irradiation [˜4 MGy(Si) ?-ray dose at 70 Gy(Si)/s, plus a fluence of ?2.8-MeV neutrons ˜2×1016 cm-2] were much less sensitive to fiber core material. The prospects for developing rad hard optical fibers for fusion reactor diagnostics are discussed in light of these findings.

Griscom, David L.

1996-08-01

270

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

International Nuclear Information System (INIS)

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

271

Resonant structure of the formation of doubly charged ions in multiphoton ionization of Sr atoms in the infrared spectral range  

International Nuclear Information System (INIS)

The process of two-charge ion formation during Sr atoms ionization by laser radiation in the range of frequencies 8200-9100 cm-1 was studied experimentally. It is shown that resonance structure in the yield of two-charge ions during Sr atoms ionization in IR range of the spectrum stems from excitation of highly disturbed states of neutral atoms. The results obtained also suggest that excitation of the disturbed states under conditions, when as a result of the Stark shift mixing of the levels occurs, results in a significantly higher yield of the two-charge ions

272

Achievement of a wide wavelength tuning range for lasing in the green and red spectral regions using new laser dyes  

Energy Technology Data Exchange (ETDEWEB)

The lasing characteristics of two new dyes related to the naphthalimide and benzantron classes were measured during pumping by second-harmonic ruby laser radiation. The tuning of the lasing wavelength was achieved in the range of about 100 nm (from 500 to 600 nm for naphthalimide and from 640 to 740 nm for benzantron). It is shown that the lasing energy of these compounds exceeds that of the widely used dyes coumarin 7 and uranin in the green region and cresyl violet in the red; moreover, their wavelength tuning range is substantially broader than that of conventional dyes.

Krymova, A.I.; Petukhov, V.A.

1986-03-01

273

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

274

Optical properties of gold nanoparticles produced by the assembly of size-selected clusters: Covering the full visible wavelength range in the smallest particle size regime  

International Nuclear Information System (INIS)

The tunability of the optical properties of small gold nanoparticles assembled from size-selected Au6-10 clusters on the surface of indium-tin-oxide glass support was studied as a function of gold particle size and shape using UV-VIS and dark-field microscopy techniques. The size and shape of gold nanoparticles was determined by employing synchrotron X-ray scattering. The obtained spectra show that a 350 nm wavelength range is accessible by proper tuning the size and shape of the studied nanoparticles with 1-2.5 nm main size and asymmetric vs symmetric form

275

Optical properties of gold nanoparticles produced by the assembly of size-selected clusters : Covering the full visible wavelength range in the smallest particle size regime.  

Energy Technology Data Exchange (ETDEWEB)

The tunability of the optical properties of small gold nanoparticles assembled from size-selected Au{sub 6-10} clusters on the surface of indium-tin-oxide glass support was studied as a function of gold particle size and shape using UV-VIS and dark-field microscopy techniques. The size and shape of gold nanoparticles was determined by employing synchrotron X-ray scattering. The obtained spectra show that a 350 nm wavelength range is accessible by proper tuning the size and shape of the studied nanoparticles with 1-2.5 nm main size and asymmetric vs symmetric form.

Vajda, S.; Wiederrecht, G. P.; Bouhelier, A; Tikhonov, G Y; Tomczyk, N; Lee, B; Seifert, S; Winans, R E

2007-01-01

276

Transmittance and optical constants of Ho films in the 3-1340 eV spectral range  

OpenAIRE

The optical constants n and k of holmium (Ho) films were obtained in the 3-1340-eV range from transmittance measurements performed at room temperature. Thin films of Ho with various thicknesses were deposited by evaporation in ultra high vacuum conditions and their transmittance was measured in situ. Ho films were deposited onto thin C-film substrates supported on high transmittance grids. Transmittance measurements were used to obtain the extinction coefficient k of Ho films. The refractive ...

Ferna?ndez Perea, Mo?nica; Larruquert, Juan Ignacio; Azna?rez, Jose? Antonio; Me?ndez, Jose? Antonio; Poletto, L.; Frassetto, F.; Malvezzi, A. M.; Bajoni, D.; Giglia, A.; Mahne, N.; Nannarone, S.

2011-01-01

277

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)

278

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

279

Spectral Response of Indium Oxynitride Thin Films  

OpenAIRE

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

280

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

281

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

OpenAIRE

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 bet...

Tomasella, L.; Munari, U.; Zwitter, T.

2010-01-01

282

High resolution spectral survey of symbiotic stars in the near-IR over the GAIA wavelength range  

OpenAIRE

High resolution (R~20,000), high signal-to-noise (S/N~100) spectra were collected for ~40 symbiotic stars with the Asiago echelle spectrograph over the same 8480-8740 Ang wavelength range covered by the ESA Cornerstone mission GAIA, centered on the near-IR CaII triplet and the head of the Paschen series. A large number (~140) of cool MKK giant and supergiant templates were observed with the same instrumentation to serve as a reference and classification grid. The spectra off...

Marrese, Paola M.; Sordo, Rosanna; Munari, Ulisse

2002-01-01

283

Transmittance and optical constants of erbium films in the 3:25 - 1580 eV spectral range  

OpenAIRE

The optical constants of erbium (Er) films were obtained in the 3:25-1580 eV range from transmittance measurements performed at room temperature. Thin films of Er were deposited by evaporation in ultra high vacuum conditions and their transmittance was measured in situ. Substrates consisted of a thin C film supported on a grid. Transmittance measurements were used to obtain the extinction coefficient k of the Er films. The refractive index n of Er was calculated using the Kramers-Krönig anal...

Larruquert, Juan Ignacio; Frassetto, F.; Garci?a-corte?s, S.; Vidal-dasilva, M.; Ferna?ndez Perea, Mo?nica; Azna?rez, Jose? Antonio; Me?ndez, Jose? Antonio; Nannarone, S.

2011-01-01

284

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

Science.gov (United States)

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

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

2015-01-01

285

In-vivo gingival sulcus imaging using full-range, complex-conjugate-free, endoscopic spectral domain optical coherence tomography  

Science.gov (United States)

Frequent monitoring of gingival sulcus will provide valuable information for judging the presence and severity of periodontal disease. Optical coherence tomography, as a 3D high resolution high speed imaging modality is able to provide information for pocket depth, gum contour, gum texture, gum recession simultaneously. A handheld forward-viewing miniature resonant fiber-scanning probe was developed for in-vivo gingival sulcus imaging. The fiber cantilever driven by magnetic force vibrates at resonant frequency. A synchronized linear phase-modulation was applied in the reference arm by the galvanometer-driven reference mirror. Full-range, complex-conjugate-free, real-time endoscopic SD-OCT was achieved by accelerating the data process using graphics processing unit. Preliminary results showed a real-time in-vivo imaging at 33 fps with an imaging range of lateral 2 mm by depth 3 mm. Gap between the tooth and gum area was clearly visualized. Further quantification analysis of the gingival sulcus will be performed on the image acquired.

Huang, Yong; Zhang, Kang; Yi, WonJin; Kang, Jin U.

2012-01-01

286

Transmittance and optical constants of erbium films in the 3.25-1580 eV spectral range.  

Science.gov (United States)

The optical constants of erbium (Er) films were obtained in the 3.25-1580 eV range from transmittance measurements performed at room temperature. Thin films of Er were deposited by evaporation in ultra high vacuum conditions and their transmittance was measured in situ. Substrates consisted of a thin C film supported on a grid. Transmittance measurements were used to obtain the extinction coefficient k of the Er films. The refractive index n of Er was calculated using the Kramers-Krönig analysis. k data were extrapolated both on the high- and low-energy parts of the spectrum by using experimental data and calculated k values available in the literature. Er, similar to other lanthanides, has a low-absorption band below the O(2,3) edge onset; the smallest absorption was measured at ~22.5 eV. Therefore, Er is a promising material for filters and multilayer coatings in the energy range below the O(2,3) edge, in which materials typically have an absorption stronger than at other energies. Good consistency of the data resulted from the application of f and inertial sum rules. PMID:21614114

Larruquert, Juan I; Frassetto, Fabio; García-Cortés, Sergio; Vidal-Dasilva, Manuela; Fernández-Perea, Mónica; Aznárez, José A; Méndez, José A; Poletto, Luca; Malvezzi, A Marco; Giglia, Angelo; Nannarone, Stefano

2011-05-20

287

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

CERN Document Server

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

Fisenko, Anatoliy I

2014-01-01

288

Continuous-wave, single-frequency, solid-state blue source for the 425-489 nm spectral range.  

Science.gov (United States)

We report a new source of cw, single-frequency radiation in the blue, offering extended tunability and practical powers in a compact, all-solid-state design. The device is based on a green-pumped, cw, singly resonant optical parametric oscillator using MgO-doped stoichiometric lithium tantalate (MgO:sPPLT) as the nonlinear material. By internal second-harmonic generation of the resonant near-infrared signal radiation in a 5 mm BiB(3)O(6) crystal, we generate nearly 450 mW of cw, single-frequency blue power over a tunable range of 425-489 nm with a linewidth of 8.5 MHz and a Gaussian spatial beam profile. The demonstrated wavelength coverage can be further extended by using alternative gratings for the MgO:sPPLT crystal. PMID:18516183

Samanta, G K; Ebrahim-Zadeh, M

2008-06-01

289

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

290

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.

291

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-08-07

292

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

293

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

294

Spectral measurements of aerosol particle extinction in the 0.4-3.7 {mu}m wavelength range, performed at Sagres with the IR-RAD sun-radiometer[Special issue with manuscripts related to the second Aerosol Characterization Experiment (ACE-2), 16 June-25 July 1997  

Energy Technology Data Exchange (ETDEWEB)

During the CLEARCOLUMN campaign which took place at Sagres (Portugal) from 16 June to 25 July 1997, more than 2000 spectral measurements of direct solar irradiance were performed at thirteen window-wavelengths in the 0.4-3.7 {mu}m range, on 27 days. The measurements were performed using the IR-RAD sun-radiometer designed and manufactured at the Institute ISAO (FISBAT), Bologna (Italy), and carefully calibrated by applying the Langley plot method to the measurements performed on 24 October 1996, at the Schneefernerhaus Observatory on the Zugspitze (Germany). From these measurements, the values of the total atmospheric optical depth were obtained at the various wavelengths, from which the corresponding spectral values of aerosol optical depth were determined through accurate corrections for Rayleigh scattering and gaseous absorption. Such values were found to be mostly smaller than 0.1 during June and early July, presenting almost neutral spectral dependence characteristics, closely related to the prevailing oceanic origins of particulate matter. Higher values of aerosol optical thickness, mainly ranging between 0.1 and 0.5 at visible wavelengths and sharply decreasing with wavelength, were found during the rest of July in the presence of predominant contents of continental and anthropogenic aerosol particles arriving from polluted European regions. The King inversion method was applied to the spectral series of aerosol optical depth to determine the particle size-distribution curves in the 0.2-20 {mu}m diameter range. For 2 of these cases (one chosen for a low atmospheric loading of marine aerosols and the other for a mean content of continental/anthropogenic aerosols), the changes in the outgoing solar radiation flux produced by aerosol particles were calculated, considering different surface albedo conditions. The results obtained in the second case show that changes of opposite sign can be caused by the same atmospheric aerosol loading when passing from oceanic to continental areas.

Vitale, Vito; Tomasi, Claudio; Bonafe, Ubaldo; Marani, Stefano; Lupi, Angelo; Cacciari, Alessandra; Ruggeri, Pietro [Istituto ISAO (FISBAT)-CNR, Bologna (Italy); Hoyningen-Huene, W. von [Bremen Univ. (Germany). Inst. fuer Umweltphysik

2000-04-01

295

Flexible metamaterials at visible wavelengths  

International Nuclear Information System (INIS)

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.

296

Resonant Visible Light Modulation with Graphene  

CERN Document Server

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

Yu, Renwen; de Abajo, F Javier Garcia

2015-01-01

297

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

298

KEY COMPARISON: Report on the comparison CCPR-K2.b of spectral responsivity measurements in the range 300 nm to 1000 nm  

Science.gov (United States)

At its meeting in March 1997, the Consultative Committee for Photometry and Radiometry (CCPR) identified several key comparisons in the field of optical radiation metrology, one of which concerns spectral responsivity. The present report concerns the key comparison CCPR-K2.b, international comparison of spectral responsivity measurements in the wavelength range 300 nm to 1000 nm, piloted by the BIPM. The comparison was carried out through the calibration of a group of transfer detectors, single silicon photodiodes and trap detectors, by the 17 participating national metrology institutes. It was organized in a star form, in two phases with two groups of participants. The report describes in detail the measurements made at the BIPM and summarizes the reports submitted by the participants. A key comparison reference value and degrees of equivalence have been determined from the calibration results. 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 Mutual Recognition Arrangement (MRA).

Goebel, R.; Stock, M.

2004-01-01

299

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

CERN Document Server

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

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

2014-01-01

300

Atmospheric aerosols, humidity, and visibility  

Energy Technology Data Exchange (ETDEWEB)

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

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

1980-01-01

301

STED microscopy in the visible range  

OpenAIRE

Light microscopy is a key scientific instrument in the life sciences. However, the resolution of far-field light microscopy is limited by diffraction. Exploiting a saturated depletion of the molecular excited state by stimulated emission, stimulated emission depletion (STED) breaks the resolution barrier in the important subfield of fluorescence microscopy. To this end, STED microscopy utilizes a doughnut-shaped beam featuring a central zero which is capable of quenching the fluorescence sole...

Willig, Katrin I.

2006-01-01

302

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

303

Efficient pulsed Cr2+:CdSe laser continuously tunable in the spectral range from 2.26 to 3.61 ?m  

International Nuclear Information System (INIS)

The efficient lasing of a Cr2+:CdSe single crystal pumped by 1.94-?m, 300-?s pulses from a Tm:YAP laser was obtained. The Cr2+:CdSe laser with a nonselective resonator emitted up to 17 mJ at a wavelength of ?2.65 ?m with the quantum slope efficiency of 63% with respect to the absorbed pump energy. The absorption coefficient of the Cr2+:CdSe crystal at the laser wavelength did not exceed 0.045 cm-1. By using a resonator with a dispersion prism, the laser wavelength was continuously tuned in the spectral range from 2.26 to 3.61 ?m. (lasers)

304

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

305

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)

306

Nonlinear spectral imaging of biological tissues  

Science.gov (United States)

The work presented in this thesis demonstrates live high resolution 3D imaging of tissue in its native state and environment. The nonlinear interaction between focussed femtosecond light pulses and the biological tissue results in the emission of natural autofluorescence and second-harmonic signal. Because biological intrinsic emission is generally very weak and extends from the ultraviolet to the visible spectral range, a broad-spectral range and high sensitivity 3D spectral imaging system is developed. Imaging the spectral characteristics of the biological intrinsic emission reveals the structure and biochemistry of the cells and extra-cellular components. By using different methods in visualizing the spectral images, discrimination between different tissue structures is achieved without the use of any stain or fluorescent label. For instance, RGB real color spectral images of the intrinsic emission of mouse skin tissues show blue cells, green hair follicles, and purple collagen fibers. The color signature of each tissue component is directly related to its characteristic emission spectrum. The results of this study show that skin tissue nonlinear intrinsic emission is mainly due to the autofluorescence of reduced nicotinamide adenine dinucleotide (phosphate), flavins, keratin, melanin, phospholipids, elastin and collagen and nonlinear Raman scattering and second-harmonic generation in Type I collagen. In vivo time-lapse spectral imaging is implemented to study metabolic changes in epidermal cells in tissues. Optical scattering in tissues, a key factor in determining the maximum achievable imaging depth, is also investigated in this work.

Palero, J. A.

2007-07-01

307

Recovering the spectral distribution of the illumination from spectral data by highlight analysis  

Science.gov (United States)

The problem of color constancy for discounting illumination color to obtain the apparent color of the object has been the topic of much research in computer vision. By assuming the neutral interface reflection and dichromatic reflection with highlights (i.e. highlights have the same color as the illuminant) various methods have been proposed aiming at recovering the illuminant color from color highlight analysis. In general, these methods are based on three color stimuli to approximate color. In this contribution, we estimate the spectral distribution from surface reflection using spectral information obtained by a spectrograph. The imaging spectrograph provides a spectral range at each pixel covering the visible wavelength range. Our method differ from existing methods by using a robust clustering technique to obtain the body and surface components in a multi-spectral space. These components determine the direction of the illumination spectral color. Then, we recover the illumination spectral power distribution by using principal component analysis for all wavelengths. To obtain the most reliable estimate of the spectral power distribution of the illuminant, all possible combinations of wavelengths are used to generate the optimal averaged estimation of the spectral power distribution of the scene illuminant. Our method is restricted to images containing a substantial amount of body reflection and highlights.

Stokman, Harro M.; Gevers, Theo

1999-09-01

308

Spectral Sets  

OpenAIRE

This is a chapter of the forthcoming Handbook of Linear Algebra, 2nd Edition (ed. L. Hogben). Spectral sets and K-spectral sets, introduced by John von Neumann in [vNe51], offer a possibility to estimate the norm of functions of matrices in terms of the sup-norm of the function. Examples of such spectral sets include the numerical range or the pseudospectrum of a matrix, discussed in Chapters 16 and 18. Estimating the norm of functions of matrices is an essential task in numerous fields of pu...

Priestley, H.

2013-01-01

309

The Visible and Near Infrared module of EChO  

OpenAIRE

The Visible and Near Infrared (VNIR) is one of the modules of EChO, the Exoplanets Characterization Observatory proposed to ESA for an M-class mission. EChO is aimed to observe planets while transiting by their suns. Then the instrument had to be designed to assure a high efficiency over the whole spectral range. In fact, it has to be able to observe stars with an apparent magnitude Mv= 9-12 and to see contrasts of the order of 10-4 - 10-5 necessary to reveal the characteris...

Adriani, A.; Bellucci, G.; Gambicorti, L.; Focardi, M.; Oliva, E.; Farina, M.; Di Giorgio, A. M.; Santoli, F.; Pace, E.; Piccioni, G.; Filacchione, G.; Pancrazzi, M.; Tozzi, A.; Micela, G.

2014-01-01

310

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

311

All-fiber frequency-doubled visible laser.  

Science.gov (United States)

All-fiber ns-pulsed visible laser at ?=521??nm is realized by frequency doubling an Yb-doped fiber laser with a periodically poled silica fiber. A 50-mW second-harmonic (SH) output power is produced that is over 6-orders of magnitude greater than previous results obtained with poled fibers in the visible spectral range. The normalized conversion efficiency of 0.3%/W is to date the largest demonstrated with poled fiber technology. Furthermore, 21% conversion efficiency is achieved for the doubling of 8-ps pulses from a neodymium-doped yttrium vanadate solid-state laser. The advances are made possible by the precision and flexibility offered by using the continuous periodic UV erasure, as opposite to photolithographic methods, for the fabrication of over 20-cm-long ?(2)-gratings for quasi-phase matched SH generation. PMID:25490505

Corbari, Costantino; Gladyshev, Alexey V; Lago, Laure; Ibsen, Morten; Hernandez, Yves; Kazansky, Peter G

2014-11-15

312

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

313

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

Science.gov (United States)

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

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

2013-02-19

314

Visible Light Emission from Atomic Scale Patterns Fabricated by the Scanning Tunneling Microscope  

OpenAIRE

Scanning tunneling microscope (STM) induced light emission from artificial atomic scale structures comprising silicon dangling bonds on hydrogen-terminated Si(001) surfaces has been mapped spatially and analyzed spectroscopically in the visible spectral range. The light emission is based on a novel mechanism involving optical transitions between a tip state and localized states on the sample surface. The wavelength of the photons can be changed by the bias voltage of the STM. The spatial reso...

Thirstrup, C.; Sakurai, M.; Stokbro, Kurt; Aono, M.

1999-01-01

315

Tailorable, Visible Light Emission From Silicon Nanocrystals  

Energy Technology Data Exchange (ETDEWEB)

J. P. Wilcoxon and G. A. Samara Crystalline, size-selected Si nanocrystals in the size range 1.8-10 nm grown in inverse micellar cages exhibit highly structured optical absorption and photoluminescence (PL) across the visible range of the spectrum. The most intense PL for the smallest nanocrystals produced This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. to induce a useful level of visible photoluminescence (PL) from silicon (Si). The approaches understood. Visible PL has been observed from Si nanocrystals, or quantum dots, produced by a variety of techniques including aerosols,2 colloids,3 and ion implantation.4 However, all of The optical absorption spectra of our nanocrystals are much richer in spectral features spectrum of bulk Si where the spectral features reflect the details of the band structure shown in nanocrystals estimated to have a Si core diameter of 1-2 nm. These measured quantum those in the spectrum of bulk Si in Fig. 1 are striking indicating that nanocrystals of this size 8-Room temperature PL results on an HPLC size-selected, purified 2 nm nanocrystals but blue shifted by -0.4 eV due to quantum confinement. Excitation at 245 nm yields the PL shows the PL spectrum for a similar sample excited at 490 nm (2.53 eV) trapped excitons at the surface of Si nanocrystals. The excitons are obtained for dimer bonds 1.8- 10 nm. These nanocrystals retain bulk-like optical absorption and an indirect bandgap Figure 1. The absorption spectrum of d = 2 nm Si nanocrystals compared to that of bulk7 Si. Figure 2. The extinction and PL (excitation at 490 nm) spectra ford= 8-10 nm Si nanocrystals.

Samara, G.A.; Wilcoxon, J.P.

1999-07-20

316

Water vapor retrieval from OMI visible spectra  

Science.gov (United States)

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

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

2014-06-01

317

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

318

Feature Point Descriptors: Infrared and Visible Spectra  

OpenAIRE

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

Recent variability of the solar spectral irradiance and its impact on climate modelling  

OpenAIRE

The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE (SOlar Radiation and Climate Experiment) satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near...

Ermolli, I.; Matthes, K.; Dudok Wit, T.; Krivova, N. A.; Tourpali, K.; Weber, M.; Unruh, Y. C.; Gray, L.; Langematz, U.; Pilewskie, P.; Rozanov, E.; Schmutz, W.; Shapiro, A.; Solanki, S. K.; Thuillier, G.

2013-01-01

320

Visible Human Project  

Science.gov (United States)

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

321

Morphology of the spectral resonance structure of the electromagnetic background noise in the range of 0.1–4 Hz at L = 5.2  

Directory of Open Access Journals (Sweden)

Full Text Available Continuous observations of fluctuations of the geomagnetic field at Sodankylä Geophysical Observatory (L = 5.2 were used for a comprehensive morphological study of the spectral resonance structure (SRS seen in the background electromagnetic noise in the frequency range of 0.1–4.0 Hz. It is shown that the occurrence rate of SRS is higher in the nighttime than in the daytime. The occurrence rate is higher in winter than in summer. The SRS frequencies and the difference between neighbouring eigenfrequencies (the frequency scale increase towards nighttime and decrease towards daytime. Both frequency scale and occurrence rate exhibit a clear tendency to decrease from minimum to maximum of the solar activity cycle. It is found that the occurrence rate of SRS decreases when geomagnetic activity increases. The SRS is believed to be a consequence of a resonator for Alfvén waves, which is suggested to exist in the upper ionosphere. According to the theory of the ionospheric Alfvén resonator (IAR, characteristics of SRS crucially depend on electron density in the F-layer maximum, as well as on the altitudinal scale of the density decay above the maximum.We compared the SRS morphological properties with predictions of the IAR theory. The ionospheric parameters needed for calculation were obtained from the ionosphere model (IRI-95, as well as from measurements made with the ionosonde in Sodankylä. We conclude that, indeed, the main morphological properties of SRS are explained on the basis of the IAR theory. The measured parameters of SRS can be used for improving the ionospheric models.Key words. Ionosphere (auroral ionosphere; wave propagation – Radio Science (electromagnetic noise and interference

J. Manninen

322

Evaluation of the composition, the pressure, the thermodynamic properties and the monatomic spectral lines at fixed volume for a SiO2-Ag plasma in the temperature range 5000-25 000 K  

Science.gov (United States)

The pressure, the composition, the internal energy, the heat capacity and several monatomic spectral line intensities are calculated at constant volume for a plasma composed of SiO2 and Ag for several initial densities and in the temperature range 5000-25 000 K at thermodynamic equilibrium. We show that with a small quantity of material in the plasma we obtain a high pressure. From the heat capacity and composition calculation, we deduce that the main reactions are the ionization of Ag, the dissociation of SiO2 to SiO with further dissociation and ionization of Si and O in the considered temperature range. Furthermore, with the monatomic spectral line calculation, we deduce that the oxygen spectral line has a behaviour rather different from those emitted by Ag and Si.

Bussière, W.; André, P.

2001-06-01

323

Visible to NIR DLP hyperspectral imaging system for surgical utility using inherent chromophores and fluorescent probes  

Science.gov (United States)

Visible DLP® hyperspectral reflectance imaging in medical applications is limited by the lack of penetration of visible light for visualization of deeper vessels and tissues. The longer, near infrared (NIR) wavelengths, capable of facilitating chromophore and fluorophore visualization, penetrate deeper allowing visualization of anatomical structures in surgical settings. Digital micromirror device (DMD) chips allow for digital programming of complex spectral illuminations with bandwidths as low as 7nm. Furthermore, fluorescence can be maximized by programming the DMD chip to illuminate with light precisely configured to contain excitation spectra. We have developed a "mid-range" system that extends from the visible light range into the NIR (525nm - 1050nm) and has been characterized and configured for fluorescence of indocyanine green (ICG). The DMD-based light source was found to be within the manufacturer's spectral specifications and proved to be very versatile in both spectral behavior and application. Fluorescence of ICG was successfully optimized by this system and demonstrated in capillary tubes and excised tissue.

Mangum, Michael L.; Saint-Cyr, Michel; Wehner, Eleanor F.; Thapa, Abhas; Livingston, Edward; Zuzak, Karel J.

2011-03-01

324

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.

325

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

326

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

Science.gov (United States)

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

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

2015-02-01

327

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

Science.gov (United States)

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

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

2015-04-01

328

Estimation of visibility using a visual image.  

Science.gov (United States)

Optical-based visibility measurement instruments have been widely used to quantify atmospheric light extinction for decades. The light extinction coefficient is converted to visual range using a well-known formula since visibility is defined as the longest distance at which a black object can be observed against the horizon. In this study, a camera-based visibility monitoring technique was introduced to directly estimate visual range using a visual image obtained from a camera system. It was denoted as image visual range. The visual, optical, and geographical visibility monitoring were conducted to investigate the relationship between image visual range and distance from camera installed at the monitoring site. The visibility estimation formula, which is the function of the y position of the coordinates in the visual image, was introduced. And image visual range was estimated from the visual image using the chromatic analysis. It was found that the relationship between the image visual range and the y position of the visual image was a nonlinear function. The average relative error of image visual range less than 50 km was acceptable from the results of the relationship between optical-based visual range and image visual range. It was estimated that the relative error between two variables was not only attributed to the perspective and the faint outline of the visual image in the chromatic analysis but also associated with the assumption of the uniform distribution of the light extinction by aerosol within the field of view in the optical monitoring. PMID:25647796

Kim, Kyung Won

2015-03-01

329

Earth's spectral albedo from 0.5 to 4.4 um  

Science.gov (United States)

We have analyzed spectroscopic earthshine data to determine Earth's nightly spectral albedos covering the visible, near and middle infrared spectral ranges. Observations in the visible were undertaken from Palomar Observatory with the spectrograph in the Palomar 60" telescope and with the echelle spectrograph of the InfraRed Telescope Facility (IRTF) on Mauna Kea in Hawaii. The observing runs were chosen near the quarter moon to reduce the background glow produced by the moonshine (bright side of the Moon). Although observations were taken on different nights, the similarity of lunar phases and comparable cloud cover conditions for the monitored part of the Earth's surface, allow us to derive, for the first time, an apparent albedo of the Earth covering the entire spectral range from 0.5 to 4.4 microns.

Montanes-Rodrig, P.; Palle, E.; Goode, P. R.; Koonin, S. E.

2005-12-01

330

Noncovalent functionalization of disentangled boron nitride nanotubes with flavin mononucleotides for strong and stable visible-light emission in aqueous solution.  

Science.gov (United States)

Strong and stable visible-light-emitting boron nitride nanotube (BNNT)/biomolecule nanohybrids were successfully fabricated via noncovalent functionalization of BNNTs with flavin mononucleotides (FMN). Atomic force microscopy showed excellent dispersion of the nanohybrids in aqueous solution. Infrared absorption spectroscopy revealed strong ?-? stacking interactions between FMN and BNNT sidewalls. Importantly, the fluorescence spectra revealed that the nanohybrids were highly fluorescent in the visible-light spectral range. Moreover, this fluorescence had unique pH-dependent and thermally stable properties. These nanohybrids might be used to construct novel fluorescence imaging probes that function over a wide pH and temperature range. PMID:21355547

Gao, Zhenghong; Zhi, Chunyi; Bando, Yoshio; Golberg, Dmitri; Serizawa, Takeshi

2011-03-01

331

UV-Visible Spectroscopy  

Science.gov (United States)

This webpage, part of a larger project "Understanding Chemistry", provides an introduction to UV-visible spectroscopy suitable for use in introductory chemistry and introductory analytical chemistry courses. The pages discuss UV-visible light, absorption, Beer's law, the double-beam spectrometer, and introduce some standard applications of UV-vis spectroscopy.

Clark, Jim

332

Dependence of spectral shape of bremsstrahlung spectra on atomic number of target materials in the photon energy range of 5-30 keV  

International Nuclear Information System (INIS)

Dependence of spectral shape of total bremsstrahlung spectra i.e. the sum of ordinary bremsstrahlung (OB) and polarization bremsstrahlung (PB), on the atomic number (Z) of target materials (Al, Ti, Sn and Pb), produced by continuous beta particles of 90Sr and 204Tl, has been investigated in the photon energy region of 5-30 keV. It has been found that the spectral shape of total bremsstrahlung spectra, in terms of S (k, Z) i.e. the number of photons of energy k per moc2 per beta disintegration, is not linearly dependent on the atomic number (Z) of the target material and rather it is proportional to Zn. At lower photon energies, the index values ‘n’ of Z-dependence are much higher than unity, which is due to the larger contribution of PB into OB. The decrease in ‘n’ values with increase of photon energy is due to the decrease in contribution of PB into OB. It is clear that the index ‘n’ values obtained from the modified Elwert factor (relativistic) Bethe-Heitler theory, which include the contribution PB into OB, are in agreement with the experimentally measured results using X-PIPS Si(Li) detector. Hence the contribution of PB into the formation of a spectral shape of total bremsstrahlung spectra plays a vital role.

333

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.

334

An automatic atmospheric correction algorithm for visible/NIR imagery  

OpenAIRE

The automatic correction of atmospheric effects currently requires visible to short-wave spectral bands (400–2500nm) to derive high accuracy surface reflectance data. Common techniques employ spectral correlations of dark targets in the short-wave infrared (SWIR, around 2.2 mm), blue (480 nm) and red (660 nm) regions to derive the aerosol optical depth. A large number of current Earth-observing satellite sensors have only three or four spectral channels in the visible and near-infrared (VNI...

Richter, R.; Schla?pfer, D.; Mu?ller, A.

2006-01-01

335

Validation of H2O continuum absorption models in the wave number range 180-600 cm(-1) with atmospheric emitted spectral radiance measured at the Antarctica Dome-C site.  

Science.gov (United States)

This work presents the results concerning the analysis of a set of atmospheric emitted (down welling) spectral radiance observations in the spectral range 180 to 1100 cm(-1) acquired at the Dome-C site in Antarctica during an extensive field campaign in 2011-2012. The work has been mainly focused on retrieving and validating the coefficients of the foreign contribution to the water vapour continuum absorption, within a spectral range overlapping the water vapour rotational band. Retrievals have been performed by using a simultaneous physical retrieval procedure for atmospheric and spectroscopic parameters. Both day (summer) and night (winter) spectra have been used in our analysis. This new set of observations in the far infrared range has allowed us to extend validation and verification of state-of-art water vapour continuum absorption models down to 180 cm(-1). Results show that discrepancies between measurements and models are less than 10% in the interval 350-590 cm(-1), while they are slightly larger at wave numbers below 350 cm(-1). On overall, our study shows a good consistency between observations and state-of-art models and provides evidence toward needing to adjust absorptive line strengths. Finally, it has been found that there is a good agreement between the coefficients retrieved using either summer or winter spectra, which are acquired in far different meteorological conditions. PMID:25090497

Liuzzi, Giuliano; Masiello, Guido; Serio, Carmine; Palchetti, Luca; Bianchini, Giovanni

2014-07-14

336

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

337

The ultrafast nonlinear optical response and multi-photon absorption of a new metal complex in the near-infrared spectral range  

International Nuclear Information System (INIS)

A new coordination compound, chloro(1,10-phenanthroline-N, N')(triphenylphosphine)copper(I) dichloromethane, incorporated in poly(methyl methacrylate) exhibits superior nonlinear optical properties in the near-infrared spectral region. Its nonlinear response time and third-order nonlinear optical susceptibility at 800 nm are ? 90 fs and 1.8 × 10?10 esu, respectively. Considerable nonlinear absorption is observed with this sample, near 800 and 1250 nm. The contribution of the excited states to the total nonlinear absorption process is discussed. The results reveal the potential of this newly designed compound for multi-photon absorption-based photonic applications

338

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

OpenAIRE

We study spectral diagnostics available from optical spectra with R=17000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the gamma Vel young cluster, in order to determine the fundamental parameters of these stars. We define a set of spectroscopic indices, sampling TiO bands, H-alpha core and wings, and many temperature- and gravity-sensitive lines. Combined indices tau (gamma) are also defined as Teff (log g) indicators over a wid...

Damiani, F.; Prisinzano, L.; Micela, G.; Randich, S.; Gilmore, G.; Drew, J. E.; Jeffries, R. D.; Fre?mat, Y.; Alfaro, E. J.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Lanzafame, A. C.; Pancino, E.; Recio-blanco, A.

2014-01-01

339

Visible Embryo: 16 weeks  

Science.gov (United States)

one page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Dr. R B Armstrong (Washington State University)

2006-10-31

340

Visible Embryo: 24 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-10-31

341

Visible Embryo: 18 weeks  

Science.gov (United States)

one page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-10-31

342

Visible Embryo: 38 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-11-01

343

Visible Embryo: birth  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-11-01

344

Visible Embryo: 36 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-11-01

345

Visible Embryo: 20 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-10-31

346

Visible Embryo: 34 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-11-01

347

Visible Embryo: 32 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-11-01

348

Visible Embryo: 22 weeks  

Science.gov (United States)

One page from a comprehensive resource of information on human development from conception to birth, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development.

Carmen Arbona (Mouseworks)

2006-10-31

349

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

350

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

351

Compact multispectral continuous zoom camera for color and SWIR vision with integrated laser range finder  

Science.gov (United States)

In an electro-optical sensor suite for long range surveillance tasks the optics for the visible (450nm - 700nm) and the SWIR spectral wavelength range (900nm - 1700 nm) are combined with the receiver optics of an integrated laser range finder (LRF) .The incoming signal from the observed scene and the returned laser pulse are collected within the common entrance aperture of the optics. The common front part of the optics is a broadband corrected lens design from 450 - 1700nm wavelength range. The visible spectrum is split up by a dichroic beam splitter and focused on a HDTV CMOS camera. The returned laser pulse is spatially separated from the scene signal by a special prism and focused on the laser receiver diode of the integrated LRF. The achromatic lens design has a zoom factor 14 and F#2.6 in the visible path. In the SWIR path the F-number is adapted to the corresponding chip dimensions . The alignment of the LRF with respect to the SWIR camera line of sight can be controlled by adjustable integrated wedges. The two images in the visible and the SWIR spectral range match in focus and field of view (FOV) over the full zoom range between 2° and 22° HFOV. The SWIR camera has a resolution of 640×512 pixels. The HDTV camera provides a resolution of 1920×1080. The design and the performance parameters of the multispectral sensor suite is discussed.

Hübner, M.; Gerken, M.; Achtner, Bertram; Kraus, M.; Münzberg, M.

2014-06-01

352

Study of varnish layers with optical coherence tomography in both visible and infrared domains  

Science.gov (United States)

Optical Coherence Tomography (OCT) is an attractive technique to study works of art because it allows non-destructive and contactless analysis. In the case of musical instruments, the study of wood finishes could give interesting information as the thicknesses of the layers, the number of layers and the presence of fillers. A time-domain full-field OCT, achieving high resolution, is used in both visible and near infrared ranges to characterize semi-transparent layers containing scattering particles as charged varnish layers. We present OCT measurements on wood varnished with different coatings. We show that the detection of pigment particles is dependent of the spectral range and that both spectral domains allow to reach micrometer-scale spatial resolutions.

Latour, Gaël; Georges, Gaëlle; Siozade, Laure; Deumié, Carole; Echard, Jean-Philippe

2009-07-01

353

Earth's spectral reflectivity  

Science.gov (United States)

Cyclic spectroscopic observations of the dark and bright sides of the moon (or earthshine and moonshine) have been carried out in the visible spectral region from several astronomical observatories as Earth rotates. The ratio of the earthshine to moonshine has been analyzed to determine the globally-integrated Earth's albedo during the observations. Information concerning to the search of terrestrial planets beyond the solar system can also be obtained from these results.

Montanes, P.

2007-05-01

354

The visible and near infrared module of EChO  

Science.gov (United States)

The Visible and Near Infrared (VNIR) is one of the modules of EChO, the Exoplanets Characterization Observatory proposed to ESA for an M-class mission. EChO is aimed to observe planets while transiting by their suns. Then the instrument had to be designed to assure a high efficiency over the whole spectral range. In fact, it has to be able to observe stars with an apparent magnitude Mv = 9-12 and to see contrasts of the order of 10-4-10-5 necessary to reveal the characteristics of the atmospheres of the exoplanets under investigation. VNIR is a spectrometer in a cross-dispersed configuration, covering the 0.4-2.5 ?m spectral range with a resolving power of about 330 and a field of view of 2 arcsec. It is functionally split into two channels respectively working in the 0.4-1.0 ?m and 1.0-2.5 ?m spectral ranges. Such a solution is imposed by the fact the light at short wavelengths has to be shared with the EChO Fine Guiding System (FGS) devoted to the pointing of the stars under observation. The spectrometer makes use of a HgCdTe detector of 512 by 512 pixels, 18 ?m pitch and working at a temperature of 45 K as the entire VNIR optical bench. The instrument has been interfaced to the telescope optics by two optical fibers, one per channel, to assure an easier coupling and an easier colocation of the instrument inside the EChO optical bench.

Adriani, A.; Bellucci, G.; Gambicorti, L.; Focardi, M.; Oliva, E.; Farina, M.; Di Giorgio, A. M.; Santoli, F.; Pace, E.; Piccioni, G.; Filacchione, G.; Pancrazzi, M.; Tozzi, A.; Micela, G.

2014-06-01

355

InAsSb detectors for visible to MWIR high operating temperature applications  

OpenAIRE

The Photon-Trap Structures for Quantum Advanced Detectors (PT-SQUAD) program requires MWIR detectors at 200 K. One of the ambitious requirements is to obtain high (> 80 %) quantum efficiency over the visible to MWIR spectral range while maintaining high D* (> 1.0 x 1011 cm ?Hz/W) in the MWIR. A prime method to accomplish the goals is by reducing dark diffusion current in the detector via reducing the volume fill ratio (VFR) of the detector while optimizing absorption. Electromagnetic simula...

D’souza, A. I.; Ionescu, A. C.; Salcido, M.; Robinson, E.; Dawson, L. C.; Okerlund, D. L.; Lyon, T. J.; Rajavel, R. D.; Sharifi, H.; Yap, D.; Beliciu, M. L.; Mehta, S.; Dai, W.; Chen, Gang; Dhar, N.

2011-01-01

356

Photovoltaic Detector Based on Type II Heterostructure with Deep AlSb/InAsSb/AlSb Quantum Well in the Active Region for the Mid-Infrared Spectral Range  

International Nuclear Information System (INIS)

Photodetectors for the spectral range 2-4 ?m, based on an asymmetric type-II heterostructure p-InAs/AlSb/InAsSb/AlSb/(p, n)-GaSb with a single deep quantum well (QW) or three deep QWs at the heterointerface, have been grown by metal-organic vapor phase epitaxy and analysed. The transport, luminescent, photoelectric, current-voltage, and capacitance-voltage characteristics of these structures have been examined. A high-intensity positive and negative luminescence was observed in the spectral range 3-4 ?m at high temperatures (300–400 K). The photosensitivity spectra were in the range 1.2–3.6 ?m (T = 77 K). Large values of quantum efficiency (? = 0.6–0.7), responsivity (S? = 0.9–1.4 A·W1), and detectivity D*? 3.5·1011 to 1010 cm·Hz1/2·W?1) were obtained at T = 77–200 K. The small capacitance of the structures (C = 1.5 pF at V = ?1 V and T = 300 K) enabled an estimate of the response time of the photodetector at ? = 75 ps, which corresponds to a bandwidth of about 6 GHz. Photodetectors of this kind are promising for heterodyne detection of the emission of quantum-cascade lasers and IR spectroscopy

357

Infrared spectral studies of asteroids  

Science.gov (United States)

The first comprehensive spectrophotometric survey in the near-infrared (0.8 to 2.5 microns) was carried out with the NASA Infrared Telescope Facility and special filters optimized for spectroscopy of solid surfaces. About 105 asteroids have been observed (in 52 photometric passbands) to date. These spectra provide a much improved database for determining the mineralogy of the various asteroid spectral classes previously defined on the basis of visible (0.3 to 1.0 micron) data. Preliminary results from analysis of these spectra include: (1)Class "A" asteroids are dominated by olivine and correspond to the rare brachinite meteorites; (2)Class "S" asteroids have highly variable olivine/pyroxene ratios inconsistent with chondritic compositions; (3)Classes "P" and "D" are apparently "ultracarbonacous" material which extends the known range of chondrites to lower condensation temperatures; (4)The distribution of spectral types shows that the asteroids were heated by a mechanism whose intensity declined rapidly with solar distance; and (5)Spectra of the proposed flyby targets for CRAF were used to evaluate the results obtainable from this mission.

Bell, J. F.

1986-01-01

358

Pixel Dynamics Analysis of Photospheric Spectral Data  

Science.gov (United States)

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

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

2015-04-01

359

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

360

USGS Digital Spectral Library splib06a  

Science.gov (United States)

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

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

2007-01-01

361

KEY COMPARISON: Final report on the key comparison CCPR-K2.a-2003: Spectral responsivity in the range of 900 nm to 1600 nm  

Science.gov (United States)

An international comparison of spectral responsivity in the near infrared region, 900 nm to 1600 nm, designated CCPR-K2.a, has been conducted under the Consultative Committee for Photometry and Radiometry (CCPR) as one of the key comparisons to support the Mutual Recognition Arrangement (MRA). This comparison was participated in by 15 laboratories and was piloted by National Institute of Standards and Technology (NIST). The comparison was carried out through calibration of a group of transfer standard detectors, which were indium gallium arsenide (InGaAs) photodiodes with sapphire windows, mounted with a thermistor. The comparison was organized in a star pattern, and conducted in four groups of participants. The report describes in detail the measurements made at NIST and summarizes the reports submitted by the participants. Key comparison reference values and degrees of equivalence have been determined from the comparison results. 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 (MRA).

Brown, Steven W.; Larason, Thomas C.; Ohno, Yoshi

2010-01-01

362

ZnO nanowire based visible-transparent ultraviolet detectors on polymer substrates  

Science.gov (United States)

The fabrication and characterization of fully visible-transparent and flexible ultraviolet (UV) detectors, on polyethylene 2,6-naphthalate (PEN) with active channels of zinc oxide nanowires and ohmic indium tin oxide contacts, are reported and discussed. The fabricated detector has an average transmittance of 80% in the visible spectral range and is most responsive at or below 370 nm, the onset of UV light, with a UV/vis rejection ratio of 1.42 × 103. A five orders of magnitude difference in the photocurrent, between UV illumination and dark conditions, are also observed. The single-sided UV response further shows that the PEN substrate performs well as a UV reflector. The noise analysis on the nanowire UV detector indicates a noise equivalent power and detectivity (D*) of 5.88 × 10-13 WHz-0.5 and 2.13 × 109 cm Hz0.5 W-1, respectively.

Yu, Hongbin; Ali Azhar, Ebraheem; Belagodu, Tej; Lim, Swee; Dey, Sandwip

2012-05-01

363

Dispersion of the electrooptic coefficient of the InP(Fe) crystal in the 1.5-10.6 ?m spectral range  

International Nuclear Information System (INIS)

The dispersion dependences of the quality factor and electrooptical coefficient of InP(Fe) crystal are measured by the polarization-optical method in the 1.5-10.6 ?m spectrum range. The local level (0.14+0.06) eV is found which affects directly on the InP(Fe) crystal electrooptical properties

364

UVISS preliminary visibility analysis  

DEFF Research Database (Denmark)

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

Betto, Maurizio

1998-01-01

365

Visible LED alternatives for high-radiance applications  

Science.gov (United States)

Laser diodes are used in high radiance applications, requiring spatially and angularly localized optical power, in order to minimize system size, cost, and power requirements. For applications requiring visible wavelengths (400nm to 700nm), AlInGaP laser diodes are utilized for wavelengths between 630nm and 650nm, and recently InGaN-based laser diodes spanning the violet to blue spectral range (400nm to 450nm) have become available, with longer wavelength devices being actively developed. It is not clear, however, when reliable laser diodes emitting in the green to yellow portion of the visible spectrum (>500nm) will be realized. In addition, single mode laser diodes required for high radiance applications typically exhibit speckle effects, are temperature sensitive, require non-linear drive electronics, and can be effected by optical feedback. High radiance LEDs with appropriate emitter dimensions can be used in place of laser diodes provided that moderate coherence and power levels are acceptable. This article examines the general dependencies of beam focusing, collimation, and coherence, on LED emitter size and radiance. Specific model examples are considered, using parameters consistent with typical laser diode collimating lenses. Edge emitting LEDs or EELEDs used for miniature scanned displays are described as high radiance LEDs suitable for other applications requiring collimation, partial coherence, or localized irradiance.

Altendorf, Eric H.

2003-07-01

366

Pyrazinoporphyrazines with externally appended pyridine rings. 13. Structure, UV-visible spectral features, and noncovalent interaction with DNA of a positively charged binuclear (Zn(II)/Pt(II)) macrocycle with multimodal anticancer potentialities.  

Science.gov (United States)

We investigated with spectroscopic techniques the noncovalent interaction of a bimetallic water-soluble (Zn(II)/Pt(II)) porphyrazine hexacation, [(PtCl(2))(CH(3))(6)LZn](6+), and its octacationic analogue [(CH(3))(8)LZn](8+), lacking the cis-platin-like functionality, with a 21-mer double strand (ds) 5'-d[GGG(TTAGGG)(3)]-3'/3'-d[CCC(AATCCC)(3)]-5', as model for B-DNA. Both hexacation and octacation tend to aggregate in water. The structure as well as the ground and excited-state electronic properties of the Zn(II)/Pt(II) hexacation [(PtCl(2))(CH(3))(6)LZn](6+) in water solution were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. TDDFT calculations of the lowest excited states of [(PtCl(2))(CH(3))(6)LZn](6+) in water provided an accurate description of the Q-band spectral region. In particular, the calculated optical spectra were in agreement with the experimental ones, obtained in the presence of micelles favoring complete disruption of the aggregates. The model for dsDNA binding that emerges from the analysis of UV-vis absorption and time-resolved fluorescence data shows the presence of complexes of 1 dsDNA molecule with 1, 2, and 4 macrocycles. Comparing the results for the hexacation [(PtCl(2))(CH(3))(6)LZn](6+) with those for the [(CH(3))(8)LZn](8+)octacation, we observed a higher degree of monomerization for the [(PtCl(2))(CH(3))(6)LZn](6+) derivative. PMID:23244699

Manet, Ilse; Manoli, Francesco; Donzello, Maria Pia; Viola, Elisa; Masi, Annalisa; Andreano, Giuseppina; Ricciardi, Giampaolo; Rosa, Angela; Cellai, Luciano; Ercolani, Claudio; Monti, Sandra

2013-01-01

367

Making Invisible Histories Visible  

Science.gov (United States)

This article features Omaha Public Schools' "Making Invisible Histories Visible" program, or MIHV. Omaha's schools have a low failure rate among 8th graders but a high one among high school freshmen. MIHV was created to help at-risk students "adjust to the increased demands of high school." By working alongside teachers and mentors, the program's…

Hanssen, Ana Maria

2012-01-01

368

Visible Embryo: 30 weeks  

Science.gov (United States)

one page from a comprehensive resource of information on human development designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development. This is a subset of a larger site.

Carmen Arbona (Mouseworks)

2006-11-01

369

Visible Embryo: 14 weeks  

Science.gov (United States)

a comprehensive resource of information on human development at 14 weeks of gestation (80-90mm, 25g), designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development. This is a subset of a larger site.

Carmen Arbona (Mouseworks)

2006-10-31

370

Visible Embryo: 28 weeks  

Science.gov (United States)

one page from a comprehensive resource of information on human development, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development. This is a subset of a larger site.

Carmen Arbona (Mouseworks)

2006-11-01

371

Visible Embryo: 26 weeks  

Science.gov (United States)

a comprehensive resource of information on human development at 26 weeks of gestation, designed for both medical student and interested lay people. The Visible Embryo offers a detailed pictorial account of normal and abnormal development. This is a subset of a larger site.

Carmen Arbona (Mouseworks)

2006-11-01

372

Multimodal visible embolisation particles  

OpenAIRE

Embolisation - the blocking of vessels - is a key procedure in Interventional Radiology. It plays a steadily growing role in the treatment of various tumour lesions, with hepatic cellular carcinoma and uterine fibroids the main focus. We produced multimodal visible embolization particles, which can be visualized in X-ray based fluoroscopy and computer tomography (CT) as well as radiation free magnetic resonance imaging (MRI).

Bartling, So?nke H.; Budjan, Johannes; Sadick, Maliha; Aviv, Hagit; Margel, Shlomo; Reis, Christian; Diehl, Steffen

2011-01-01

373

Bi Youth Becoming Visible  

Science.gov (United States)

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

Hutchins, Loraine

2006-01-01

374

Surface plasmon resonance biosensing via differential spectral phase interferometry  

Science.gov (United States)

A novel surface plasmon resonance (SPR) sensor based on differential spectral phase interferometry is introduced. Our scheme incorporates a broadband white-light emitting diode (WLED) with double-pass Michelson interferometer for highly sensitive Kretschmann SPR phase detection over the visible spectrum. Superior to laser based SPR interferometer which is vulnerable to nonlinear phase saturation and conventional spectroscopic SPR sensor which only measures the spectral intensity, the proposed spectral phase interferometer directly acquires the optimal SPR phase response of every spectral component which is equivalent to having infinitely many SPR laser interferometers operating simultaneously at fixed angle of incidence. Therefore the inherent phase saturation problem due to monochromatic laser source could be readily addressed. As the result, our system prevail over existing phase detection schemes by (1) achieving comparable ultimate detection limit as good as 10-7 refractive index unit (RIU), (2) extending the phase measurement range as far as 10-2 RIU, (3) simplifying the phase modulation scheme by directly acquiring the spectral oscillation instead of adding a temporal carrier. Experimental verification with BSA-aBSA interaction demonstrates that our system is capable of achieving ultimate sensitivity of 0.5ng.ml-1 (3.3pM) for ultra-sensitive aBSA detection which is among the best reported in literature. Yet such sensitivity is extended over a wide range of measurement as each wavelength specific SPR phase jump is monitored over the entire visible spectrum. Further biosensing application such as detection of cytochrome-c with aptamer immobilized on the SPR sensing surface is currently under investigation. We believe that by combination of high sensitivity, wide dynamic range and simplicity of operation, our SPR system would be truly applicable to complicated real-life biosensing.

Ng, Siu-Pang; Wu, Chi-Man Lawrence; Wu, Shu-Yuen; Ho, Ho-Pui; Kong, Siu-Kai

2011-03-01

375

An improved version of the Visible and Near Infrared (VNIR) spectrometer of EChO  

Science.gov (United States)

The Visible and Near Infrared (VNIR) is one of the modules of EChO, the Exoplanets Characterization Observatory proposed to ESA for an M-class mission. EChO is aimed to observe planets while transiting by their suns. Then the instrument has be designed to assure a high efficiency over the whole spectral range. In fact, it has to be able to observe stars with an apparent magnitude Mv= 9÷12 and able to see contrasts of 10-4÷10-5 in order to reveal the characteristics of the atmospheres of the exoplanets under investigation. VNIR was originally designed for covering the spectral range from 0.4 to 1.0 ?m [1] but now the design has been reviewed and its spectral range has been extended up to 2.5 ?m. It is a spectrometer in a cross-dispersed configuration that, then, uses the combination of a diffraction grating and a prism to spread the light in different wavelengths and in a useful number of orders of diffraction. Its resolving power is about 330 over the entire spectral range and its field of view is approximately 2 arcsec. The spectrometer is functionally split into two channels respectively working in the 0.4-1.0 ?m and 1.0-2.5 ?m spectral ranges. Such a solution is imposed by the fact the light at low wavelengths has to be shared with the EChO Fine Guiding System (FGS) devoted to the pointing of the stars under observation. The instrument works at 45K and its weight is 6 kg.

Bellucci, G.; Adriani, A.; Gambicorti, L.; Focardi, M.; Oliva, E.; Farina, M.; Di Giorgio, A. M.; Pace, E.; Piccioni, G.; Filacchione, G.; Pancrazzi, M.; Tozzi, A.; Micela, G.

2014-08-01

376

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

377

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

Science.gov (United States)

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

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

2013-09-01

378

Validation of short-pulse-laser-based measurement setup for absolute spectral irradiance responsivity calibration.  

Science.gov (United States)

This paper describes the validation process of mode-locked lasers in the "tunable lasers in photometry" (TULIP) setup at Physikalisch-Technische Bundesanstalt (PTB) regarding spectral irradiance responsivity calibrations. Validation has been carried out in the visible spectral range, 400-700 nm, with two different photometer heads and in the long wavelength range, 690-780 nm, with a filtered radiometer. A comparison of the results against those from two different validated measurement setups has been carried out for validation. For the visible spectral range, the comparison is conducted against the data obtained from a lamp-based monochromator setup for spectral irradiance responsivity calibrations and against the photometric values (integral quantity) measured at the photometric bench setup of PTB. For the long wavelength range, comparisons against results from two different lamp-based monochromator measurement setups were made. Additionally, the effect of different radiation bandwidths on interference oscillations has been determined for a filter radiometer without a diffuser. A procedure for the determination of the optimum bandwidth of the setup for the respective measurement device is presented. PMID:24921865

Schuster, Michaela; Nevas, Saulius; Sperling, Armin

2014-05-01

379

Visible Earth: Human Dimensions  

Science.gov (United States)

This website is part of Visible Earth, which is hosted by the National Aeronautics and Space Administration (NASA), and contains a searchable directory of images, visualizations, and animations of the Earth. This section pertains to human impact on the Earth, and includes images in the following categories: boundaries, land use/land cover, economic resources, environmental impacts, human health, infrastructure, and population. Each image is available in a variety of resolutions and sizes, with a brief description, credit, date, and photographing satellite.

380

Spitzer Makes 'Invisible' Visible  

Science.gov (United States)

Hidden behind a shroud of dust in the constellation Cygnus is a stellar nursery called DR21, which is giving birth to some of the most massive stars in our galaxy. Visible light images reveal no trace of this interstellar cauldron because of heavy dust obscuration. In fact, visible light is attenuated in DR21 by a factor of more than 10,000,000,000,000,000,000,000,000,000,000,000,000,000 (ten thousand trillion heptillion). New images from NASA's Spitzer Space Telescope allow us to peek behind the cosmic veil and pinpoint one of the most massive natal stars yet seen in our Milky Way galaxy. The never-before-seen star is 100,000 times as bright as the Sun. Also revealed for the first time is a powerful outflow of hot gas emanating from this star and bursting through a giant molecular cloud. The colorful image is a large-scale composite mosaic assembled from data collected at a variety of different wavelengths. Views at visible wavelengths appear blue, near-infrared light is depicted as green, and mid-infrared data from the InfraRed Array Camera (IRAC) aboard NASA's Spitzer Space Telescope is portrayed as red. The result is a contrast between structures seen in visible light (blue) and those observed in the infrared (yellow and red). A quick glance shows that most of the action in this image is revealed to the unique eyes of Spitzer. The image covers an area about two times that of a full moon.

2004-01-01

381

Photochemical investigation of a photochromic diarylethene compound that can be used as a wide range actinometer  

OpenAIRE

The photochromic diarylethene derivative 1,2-bis(5-(4-ethynylphenyl)-2-methylthiophen-3-yl)perfluorocyclopentene (1) was submitted to photochemical, thermal stability and fatigue resistance studies in acetonitrile, also to evaluate its possible application as a new actinometer. This photochromic system covers a wide spectral absorption range, with intense bands in the UV and visible regions for the open-ring and closed-ring isomers, respectively. Very high ring-closure quantum yield values we...

Ribeiro Santos, Andre?; Ballardini, Roberto; Belser, Peter; Gandolfi, Maria Teresa; Mahadevan Iyer, Vijay; Moggi, Luca

2010-01-01

382

Spectral curves of surface reflectance in some Antarctic regions  

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-04-01

383

Spectral curves of surface reflectance in some Antarctic regions  

International Nuclear Information System (INIS)

Four surface reflectance models of solar radiation were determined by examining several sets of field measurements taken for clear-sky conditions at various sites in Antarctica. Each model consists of the mean spectral curve of surface reflectance in the 0.25-2.7 ?m wavelength range and of the dependence curve of total abedo on the solar elevation angle h, within the range from 50 to 550. The TNB (Terra Nova Bay) model refers to a rocky terrain where granites are predominant; the NIS (Nansen Ice Sheet) model to a glacier surface made uneven by sastrugi and streaked by irregular fractures; the HAP (High Altitude Plateau) model to a flat ice surface covered by fresh snow and scored by light sastrugi; and the RIS (Ross Ice Shelf) model to an area covered by the sea ice pack presenting many discontinuities in the reflectance features, due to melt water lakes, puddles, refrozen ice and snow pots. The reflectance curve obtained for the TNB model presents gradually increasing values as wavelength increases through the visible spectral range and almost constant values at infrared wavelengths, giving a total albedo value equal to 0.264 at = 300, which increases by about 80% through the lower range of h and decreases by 12% through the upper range. The reflectance curves of the NIS, HAP and RIS models are all peaked at visible wavelengths and exhibit decreasing values throughout the infrared spectral range, giving values of total albedo equal tge, giving values of total albedo equal to 0.464, 0.738 and 0.426 at h 300, respectively. These values were estimated to increase by 8-14% as h decreases from 300 to 50 and to decrease by 2-4% only as h increases from 300 to 550

384

Visible parts of fractal percolation  

OpenAIRE

We study dimensional properties of visible parts of fractal percolation in the plane. Provided that the dimension of the fractal percolation is at least 1, we show that, conditioned on non-extinction, almost surely all visible parts from lines are 1-dimensional. Furthermore, almost all of them have positive and finite Hausdorff measure. We also verify analogous results for visible parts from points. These results are motivated by an open problem on the dimensions of visible ...

Arhosalo, I.; Ja?rvenpa?a?, E.; Ja?rvenpa?a?, M.; Rams, M.; Shmerkin, P.

2009-01-01

385

Miniaturized spectral imager for Aalto-1 nanosatellite  

Science.gov (United States)

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

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

2011-11-01

386

Non-Euclidean visibility problems  

CERN Document Server

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

Chamizo, F

2006-01-01

387

Spectral substraction and spectral estimation  

OpenAIRE

The problem of spectral subtraction, to estimate the parameters of a single source in colored noise, is used to show the relationships between the likelihood formulation and spectral density estimation. Reported previously as a filter bank processing for spectral estimation, it is shown that the normalized Capon estimate is the natural tool for source location in I-d and 2-d scenarios when the noise background estimate is faced as a spectral subtraction problem. Several s...

Lagunas Hernandez, Miguel A.; Pe?rez Neira, Ana Isabel

2000-01-01

388

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

Science.gov (United States)

We present a study of spectral diagnostics available from optical spectra with R = 17 000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the ? Vel young cluster, with the purpose of classifying these stars and finding their fundamental parameters. We define several spectroscopic indices, sampling the amplitude of TiO bands, the H? line core and wings, and temperature- and gravity-sensitive sets of lines, each useful as a Teff or log g indicator over a limited range of stellar spectral types. H? line indices are also useful as chromospheric activity or accretion indicators. Furthermore, we use all indices to define additional global Teff- and log g-sensitive indices ? and ?, valid for the entire range of types in the observed sample. We find a clear difference between gravity indices of main-sequence and pre-main-sequence stars, as well as a much larger difference between these and giant stars. The potentially great usefulness of the (?,?) diagram as a distance-independent age measurement tool for young clusters is discussed. We discuss the effect on the defined indices of classical T Tauri star veiling, which is however detected in only a few stars in the present sample. Then, we present tests and calibrations of these indices, on the basis of both photometry and literature reference spectra, from the UVES Paranal Observatory Projectand the ELODIE 3.1 Library. The known properties of these stars, spanning a wide range of stellar parameters, enable us to obtain a good understanding of the performances of our new spectral indices. For non-peculiar stars with known temperature, gravity, and metallicity, we are able to calibrate quantitatively our indices, and derive stellar parameters for a wide range of stellar types. To this aim, a new composite index is defined, providing a good metallicity indicator. The ability of our indices to select peculiar, or otherwise rare classes of stars is also established. For pre-main-sequence stars outside the parameter range of the ELODIE dataset, index calibration relies on model isochrones. We check our calibrations against current Gaia-ESO UVES results, plus a number of Survey benchmark stars, and also against Gaia-ESO observations of young clusters, which contribute to establishing the good performance of our method across a wide range of stellar parameters. Our gravity determination for late-type PMS stars is found to be accurate enough to let us obtain gravity-based age estimates for PMS clusters. Finally, our gravity determinations support the existence of an older pre-main-sequence population in the ? Vel sky region, in agreement with evidence obtained from the lithium depletion pattern of the same stars. Based on observations collected with the FLAMES spectrograph at VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia-ESO Large Public Survey (program 188.B-3002).Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/A50

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

2014-06-01

389

Instrument measures many optical properties in visible and IR  

Science.gov (United States)

Electro-optical system measures reflectance, reflectance ratio, transmission, absorption, refractive index, and absorption coefficient in both visible and infrared (IR) spectral regions. System effectively combining capabilities of ellisometer, reflectometer, and spectrophotometer is expected to find application in environmental and material composition testing fields.

Batten, C. E.

1979-01-01

390

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)

391

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

International Nuclear Information System (INIS)

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

392

OMEGA IR spectral imager for Mars 96 mission  

Science.gov (United States)

The goal of the OMEGA instrument (planned to fly the Mars'96 Orbiter) is to monitor the past and present evolution of Mars through visible and infrared spectral mapping of its surface. The spectral range (0.5 to 5.1 micrometers) includes signatures of major and minor components of both the surface and the atmosphere of Mars. The spectral and spatial resolutions required and the high signal to noise ratio lead to a three channel instrument: (1) A visible spectrometer (whiskbroom type) with a bidimensional silicon array (288 by 384 elements 23 by 23 micrometers) and a refractive telescope illuminating a holographic grating. (2) A two-channel infrared spectrometer (pushbroom type) based on linear InSb array (128 elements). A reflective telescope and a scanning device give the imaging capability. The IR detectors, cooled at 77 K were developed in France by the Societe Anonyme de Telecommunication (SAT) for this instrument with adapted geometry and specific two band filters. A specific electronic was developed for this instrument, especially one digital electronics based on a transputer associated to a digital signal processor in order to obtain a high efficiency, error free, data compression. After its space qualification, the instrument was fully calibrated at the Institut d'Astrophysique Spatiale (IAS) Orsay.

Puget, Pascal; Beney, J.-L.; Bibring, J.-P.; Langevin, Y.; Semery, A.; Soufflot, Alain

1995-12-01

393

[Experimental research of turbidity influence on water quality monitoring of COD in UV-visible spectroscopy].  

Science.gov (United States)

Eliminating turbidity is a direct effect spectroscopy detection of COD key technical problems. This stems from the UV-visible spectroscopy detected key quality parameters depend on an accurate and effective analysis of water quality parameters analytical model, and turbidity is an important parameter that affects the modeling. In this paper, we selected formazine turbidity solution and standard solution of potassium hydrogen phthalate to study the turbidity affect of UV--visible absorption spectroscopy detection of COD, at the characteristics wavelength of 245, 300, 360 and 560 nm wavelength point several characteristics with the turbidity change in absorbance method of least squares curve fitting, thus analyzes the variation of absorbance with turbidity. The results show, In the ultraviolet range of 240 to 380 nm, as the turbidity caused by particle produces compounds to the organics, it is relatively complicated to test the turbidity affections on the water Ultraviolet spectra; in the visible region of 380 to 780 nm, the turbidity of the spectrum weakens with wavelength increases. Based on this, this paper we study the multiplicative scatter correction method affected by the turbidity of the water sample spectra calibration test, this method can correct water samples spectral affected by turbidity. After treatment, by comparing the spectra before, the results showed that the turbidity caused by wavelength baseline shift points have been effectively corrected, and features in the ultraviolet region has not diminished. Then we make multiplicative scatter correction for the three selected UV liquid-visible absorption spectroscopy, experimental results shows that on the premise of saving the characteristic of the Ultraviolet-Visible absorption spectrum of water samples, which not only improve the quality of COD spectroscopy detection SNR, but also for providing an efficient data conditioning regimen for establishing an accurate of the chemical measurement methods. PMID:25752050

Tang, Bin; Wei, Biao; Wu, De-Cao; Mi, De-Ling; Zhao, Jing-Xiao; Feng, Peng; Jiang, Shang-Hai; Mao, Ben-Jiang

2014-11-01

394

Spectral plasma diagnostics in welding with CO2 lasers  

International Nuclear Information System (INIS)

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

395

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

Science.gov (United States)

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

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

2014-11-01

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

Modelling rotational and cyclical spectral solar irradiance variations  

Science.gov (United States)

Solar irradiance changes are highly wavelength dependent: solar-cycle variations in the UV can be on the order of tens of percent, while changes in the visible are typically only of the order of one or two permille. With the launch of a number of instruments to measure spectral solar irradiance, we are now for a first time in a good position to explore the changing solar irradiance over a large range of wavelengths and to test our irradiance models as well as some of their underlying assumptions. I will introduce some of the current modelling approaches and present model-data comparisons, using the SATIRE irradiance model and SORCE/SIM measurements as an example. I will conclude by highlighting a number of outstanding questions regarding the modelling of spectral irradiance and current approaches to address these.

Unruh, Yvonne

398

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

399

Visible Semiconductor Lasers  

Science.gov (United States)

Short-wavelength semiconductor lasers will potentially lead to major improvements in the performance of optical data storage systems. The various approaches to making visible semiconductor lasers are reviewed, including II-VI and III-V compound semiconductor lasers, and frequency-doubled infrared lasers. Although it is anticipated that diode lasers constructed from II-VI compounds will become important in the future, high-performance diode lasers of AlGaInP, a high-bandgap III-V alloy, are presently available. Lasing wavelength is 650nm<2.<680nm, and typical threshold current densities are 1-3 k?/cm2. Recent advances in the growth of quantum well device structures have resulted in significant performance improvements.

Bour, David P.

1989-05-01

400

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

401

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

CERN Document Server

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

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

2015-01-01

402

Infrared excitation spectra of visible liminescence of luminophores doped with Yb3+ and Er3+ ions  

International Nuclear Information System (INIS)

Presented are measurement results of structure of infrared spectra of excitation, absorption and radiation of the anti-Stokes luminophors which transform directly infrared radiation into a visible light. The measurements were made for the range of 0.9-1.1 ?m in the temperature range of 77-300 K for various bases (YOCl, Y2O2S, La2O2S, NaYF4) activated by Yb3+ and Er3+ ions. Stated in the scheme of crystalline splitting of multiplets into YOCl for Ybsup(3+)(sup(2)Fsub(5/2), sup(2)Fsub(7/2)) ions and for Ersub(3+)(sup(4)Isub(15/2) and sup(4)Isub(11/2)) ions taking part in energy transfer. The character of processes leading to red and green luminescence in bases studied is discussed along with their spectral coordination with various sources of infrared beams

403

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

Directory of Open Access Journals (Sweden)

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

M. Omidpanah

2012-01-01

404

Visibility trends in Tehran during 1958-2008  

Science.gov (United States)

Visibility, in the absence of certain weather conditions (e.g., fog and rain), is an excellent indicator of air quality because its impairment results from light scattering and absorption by atmospheric particles and gases. In this study, the historical airport visibility database is explored during the last five decades for the city of Tehran, Iran. Seasonal and long-term variations of the visibility are investigated using cumulative percentiles. The correlation of the long-term visibility trend with precipitation, fog and high relative humidity are also examined.The trends of visual range of the best, median, and worst visibilities at 10th, 50th and 90th percentiles of daily visibility data indicate an overall downward trend for all the percentiles. Results show a larger decrease in visibility for the Tehran metropolitan area than the sparsely populated and less polluted parts of the city. The largest trend in decreasing visibility is observed during winter time followed by spring, fall and summer. Decreasing trends in visibility occur for all stations and do not significantly depend on the special weather events.

Sabetghadam, Samaneh; Ahmadi-Givi, Farhang; Golestani, Yahya

2012-12-01

405

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

DEFF Research Database (Denmark)

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

Müller, André; Jensen, Ole Bjarlin

406

Comparison between a low-light-level visible channel and an IR channel for spaceborne night imaging  

Science.gov (United States)

Aiming at night time spaceborne imaging, we compare the expected performances of a low-light-level visible sensor with a conventional IR sensor. The low-light-level visible sensor, an electron multiplier CCD (EMCCD), is a close to ideal photon counting device, with possibly negligible dark current noise and negligible readout noise. This fact, along with the significant improvement of diffraction (about an order of magnitude), suggests an interesting competition between the two technologies. In essence, this is a tradeoff between noise and optical performances (favoring the visible channel) and basic target radiance (favoring IR). Other factors such as reliability and cost can also play an important role. While we consider two different spectral ranges with different imaging content, we are able to conduct a cautious theoretical comparison based on standard targets in various lighting conditions. We show that for a given set of system parameters, even when lighting conditions are favorable, i.e. a night with a full moon, the low-light-level visible channel performances are inferior to those of an IR channel. We also comment on the significance of the system working point regarding performances under varying condition.

Raz, Guy; Citroen, Meira; Berger, Michael

2008-04-01

407

Lunar crescent visibility  

Science.gov (United States)

We report the results of five Moonwatches, in which more than 2000 observers throughout North America attempted to sight the thin lunar crescent. For each Moonwatch we were able to determine the position of the Lunar Date Line (LDL), the line along which a normal observer has a 50% probability of spotting the Moon. The observational LDLs were then compared with predicted LDLs derived from crescent visibility prediction algorithms. We find that ancient and medieval rules are higly unreliable. More recent empirical criteria, based on the relative altitude and azimuth of the Moon at the time of sunset, have a reasonable accuracy, with the best specific formulation being due to Yallop. The modern theoretical model by Schaefer (based on the physiology of the human eye and the local observing conditions) is found to have the least systematic error, the least average error, and the least maximum error of all models tested. Analysis of the observations also provided information about atmospheric, optical and human factors that affect the observations. We show that observational lunar calendars have a natural bias to begin early.

Doggett, Leroy E.; Schaefer, Bradley E.

1994-01-01

408

Spectral-kinetic properties of heterostructures with GaAsSb/InGaAs/GaAs-based quantum wells emitting in the range of 1.0–1.2 ?m  

International Nuclear Information System (INIS)

The spectral-kinetic properties of heterostructures with GaAs/GaAsSb-based and GaAsSb/InGaAs/GaAs-based quantum wells, emitting in the range of 1.0–1.2 ?m are studied with picosecond and nanosecond temporal resolution. Intense photoluminescence in the GaAsSb/InGaAs/GaAs structure, as well as an increase in the photoluminescence wavelength by a factor of 2.5 and a shift of the location of the maximum of the peak (?100 meV) to the longer-wavelength region were observed up to room temperature. It is established that as the molar fraction of Sb and the thickness of the InGaAs layer increase, the energy of the fundamental transition decreases by a factor of 140 meV compared with the GaAsSb/InGaAs/GaAs structure with a lower Sb content and a smaller thickness of the InGaAs layer. At 300 K, the emission wavelength of such a structure was 1.18 ?m. In addition, an increase in the thickness of the InGaAs layer led to an increase in the room-temperature photoluminescence intensity by a factor of 60, which is associated with a decrease in the energy of the fundamental state for electrons in the InGaAs layer and, consequently, to larger electron localization and smaller temperature quenching of photoluminescence

409

Spectral-kinetic properties of heterostructures with GaAsSb/InGaAs/GaAs-based quantum wells emitting in the range of 1.0-1.2 {mu}m  

Energy Technology Data Exchange (ETDEWEB)

The spectral-kinetic properties of heterostructures with GaAs/GaAsSb-based and GaAsSb/InGaAs/GaAs-based quantum wells, emitting in the range of 1.0-1.2 {mu}m are studied with picosecond and nanosecond temporal resolution. Intense photoluminescence in the GaAsSb/InGaAs/GaAs structure, as well as an increase in the photoluminescence wavelength by a factor of 2.5 and a shift of the location of the maximum of the peak ({approx}100 meV) to the longer-wavelength region were observed up to room temperature. It is established that as the molar fraction of Sb and the thickness of the InGaAs layer increase, the energy of the fundamental transition decreases by a factor of 140 meV compared with the GaAsSb/InGaAs/GaAs structure with a lower Sb content and a smaller thickness of the InGaAs layer. At 300 K, the emission wavelength of such a structure was 1.18 {mu}m. In addition, an increase in the thickness of the InGaAs layer led to an increase in the room-temperature photoluminescence intensity by a factor of 60, which is associated with a decrease in the energy of the fundamental state for electrons in the InGaAs layer and, consequently, to larger electron localization and smaller temperature quenching of photoluminescence.

Morozov, S. V., E-mail: more@ipm.sci.-nnov.ru; Kryzhkov, D. I.; Aleshkin, V. Ya. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Zvonkov, B. N.; Vikhrova, O. I. [Nizhni Novgorod State University, Physical-Technical Research Institute (Russian Federation)

2013-11-15

410

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

Science.gov (United States)

The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5-10.6 ?m range. The instrumental error was found to be ±0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm. PMID:21639488

Carlie, N; Anheier, N C; Qiao, H A; Bernacki, B; Phillips, M C; Petit, L; Musgraves, J D; Richardson, K

2011-05-01

411

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

Energy Technology Data Exchange (ETDEWEB)

The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5–10.6 ?m range. The instrumental error was found to be ±0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.

Carlie, Nathan; Anheier, Norman C.; Qiao, Hong (Amy); Bernacki, Bruce E.; Phillips, Mark C.; Petit, Laticia; Musgraves, Jonathan D.; Richardson, Kathleen

2011-05-01

412

Measurement of the refractive index dispersion of As{sub 2}Se{sub 3} bulk glass and thin films prior to and after laser irradiation and annealing using prism coupling in the near- and mid-infrared spectral range  

Energy Technology Data Exchange (ETDEWEB)

The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5-10.6 {mu}m range. The instrumental error was found to be {+-}0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.

Carlie, N.; Petit, L.; Musgraves, J. D.; Richardson, K. [School of Materials Science and Engineering/COMSET, Clemson, South Carolina 29640 (United States); Anheier, N. C. Jr.; Qiao, H. A.; Bernacki, B.; Phillips, M. C. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, Richland, Washington 99352 (United States)

2011-05-15

413

Image converter tube use in VUV.UV.visible light  

Science.gov (United States)

Ultra high-speed streak cameras with image converter tubes play a very important role in the diagnosis of most experiments in laser fusion research. The window materials of the image converter tube usually applied borosilicale glass, but it is only transparent for visible light. In order to apply in VUV.UV.visible light region for the tube, we used MgF2 window material in the tube and exhibits excellent performance on the photocathode sensitivity and spectral responses in the image converter tube.

Zhang, XiaoQiu; Niu, LiHong; Gong, Maixia; Zou, Yua Xing; Liu, Jun-Qi

1999-11-01

414

Band shifting for ocean color multi-spectral reflectance data.  

Science.gov (United States)

An approach to perform band shifting applied to multi-spectral ocean remote sensing reflectance RRS values in the visible spectral range is presented. The band-shifting scheme aims at expressing RRS at a wavelength not originally part of the spectrum from data at neighboring bands. The scheme relies on the determination of inherent optical properties (IOPs) by a bio-optical model, the calculation of the IOPs at the target wavelength using the spectral shapes assumed for each IOP, and the operation of the bio-optical model in forward mode to express RRS at the target wavelength. The performance of the band-shifting scheme applied to bands typical of satellite missions is assessed with hyper-spectral data sets obtained from radiative transfer simulations or from field measurements. The relative error ? on the conversion factors from 488 to 490 nm is mostly within 1%. Analogous results are obtained for conversions in the red spectral domain (665, 667 and 670 nm) only for synthetic data sets. The range of ? for conversions between green bands (547, 555 and 560 nm) is within 2% to 5% depending on the data set considered. Similar results are obtained when RRS values are computed at 510 nm from data at 488 and 531 nm. In the case of the assessment with simulated data, all band-shifting operations are characterized by an ? range within 2% for all conversions when the concentration of chlorophyll-a is lower than 1 mg m-3. Applied to satellite data, the band-shifting scheme noticeably improves the agreement between RRS data from different missions. PMID:25836095

Mélin, Frédéric; Sclep, Gert

2015-02-01

415

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

CERN Document Server

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

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

2014-01-01

416

Spectral stratigraphy  

Science.gov (United States)

A new approach to stratigraphic analysis is described which uses photogeologic and spectral interpretation of multispectral remote sensing data combined with topographic information to determine the attitude, thickness, and lithology of strata exposed at the surface. The new stratigraphic procedure is illustrated by examples in the literature. The published results demonstrate the potential of spectral stratigraphy for mapping strata, determining dip and strike, measuring and correlating stratigraphic sequences, defining lithofacies, mapping biofacies, and interpreting geological structures.

Lang, Harold R.

1991-01-01

417

Point-focus spectral splitting solar concentrator for multiple cells concentrating photovoltaic system  

CERN Document Server

In this paper we present and experimentally validate a low-cost design of a spectral splitting concentrator for the efficient conversion of solar energy. The optical device consists of a dispersive prismatic lens made of polycarbonate designed to simultaneously concentrate the solar light and split it into its spectral components. With respect to our previous implementation, this device concentrates the light along two axes and generates a light pattern compatible with the dimensions of a set of concentrating photovoltaic cells while providing a higher concentration ratio. The mathematical framework and the constructive approach used for the design are presented and the device performance is simulated using ray-tracing software. We obtain spectral separation in the visible range within a 3x1 cm2 area and a maximum concentration of 210x for a single wavelength. The device is fabricated by injection molding and its performance is experimentally investigated. We measure an optical transmissivity above 90% in the...

Maragliano, Carlo; Stefancich, Marco

2015-01-01

418

Validation of UV-visible aerosol optical thickness retrieved from spectroradiometer measurements  

Directory of Open Access Journals (Sweden)

Full Text Available Global and diffuse UV-visible solar irradiances are routinely measured since 2003 with a spectroradiometer operated by the Laboratoire d'Optique Atmosphérique (LOA located in Villeneuve d'Ascq, France. The analysis of the direct irradiance derived by cloudless conditions enables retrieving the aerosol optical thickness (AOT spectrum in the 330–450 nm range. The site hosts also sunphotometers from the AERONET/PHOTONS network performing routinely measurements of the AOT at several wavelengths. On one hand, comparisons between the spectroradiometer and the sunphotometer AOT at 440 nm as well as, when available, at 340 and 380 nm, show good agreement. On the other hand, the AOT's spectral variations have been compared using the Angström exponents derived from AOT data at 340 and 440 nm for both instruments. The comparisons show that this parameter is difficult to retrieve accurately due to the small wavelength range and due to the weak AOT values. Thus, AOT derived at wavelengths outside the spectroradiometer range by means of an extrapolation using the Angström parameter would be of poor value, whereas, spectroradiometer's spectral AOT could be used for direct validation of other AOT, such as those provided by satellite instruments.

C. Brogniez

2008-02-01

419

Enhancement of imagery in poor visibility conditions  

Science.gov (United States)

Current still image and video systems are typically of limited use in poor visibility conditions such as in rain, fog, smoke, and haze. These conditions severely limit the range and effectiveness of imaging systems because of the severe reduction in contrast. The NASA Langley Research Center"s Visual Information Processing Group has developed an image enhancement technology based on the concept of a visual servo that has direct applications to the problem of poor visibility conditions. This technology has been used in cases of severe image turbidity in air as well as underwater with dramatic results. Use of this technology could result in greatly improved performance of perimeter surveillance systems, military, security, and law enforcement operations, port security, both on land and below water, and air and sea rescue services, resulting in improved public safety.

Woodell, Glenn; Jobson, Daniel J.; Rahman, Zia-ur; Hines, Glenn

2005-05-01

420

Low-loss antireflection coating for the visible  

Science.gov (United States)

It is shown the procedure of achieving a broadband antireflection coating for the visible. The coating structure is composed of 8 layers made of two materials: zirconium dioxide and magnesium fluoride. The experimental efficiency for getting a coating (for the admissibility criterion--specular reflection factor in the spectral (440 - 650) nm spectral

Muscalu, G. L.

1995-03-01

421

Spectral reflectance properties of carbonaceous chondrites: 2. CM chondrites  

Science.gov (United States)

We have examined the spectral reflectance properties and available modal mineralogies of 39 CM carbonaceous chondrites to determine their range of spectral variability and to diagnose their spectral features. We have also reviewed the published literature on CM mineralogy and subclassification, surveyed the published spectral literature and added new measurements of CM chondrites and relevant end members and mineral mixtures, and measured 11 parameters and searched pair-wise for correlations between all quantities. CM spectra are characterized by overall slopes that can range from modestly blue-sloped to red-sloped, with brighter spectra being generally more red-sloped. Spectral slopes, as measured by the 2.4:0.56 ?m and 2.4 ?m:visible region peak reflectance ratios, range from 0.90 to 2.32, and 0.81 to 2.24, respectively, with values tandem, suggesting a single cause, specifically serpentine-group phyllosilicates. The generally high Fe content, high phyllosilicate abundance relative to mafic silicates, and dual Fe valence state in CM phyllosilicates, all suggest that the phyllosilicates will exhibit strong absorption bands in the 0.7 ?m region (due to Fe 3+-Fe 2+ charge transfers), and the 0.9-1.2 ?m region (due to Fe 2+ crystal field transitions), and generally dominate over mafic silicates. CM petrologic subtypes exhibit a positive correlation between degree of aqueous alteration and depth of the 0.7 ?m absorption band. This is consistent with the decrease in fine-grained opaques that accompanies aqueous alteration. There is no consistent relationship between degree of aqueous alteration and evidence for a 0.65 ?m region saponite-group phyllosilicate absorption band. Spectra of different subsamples of a single CM can show large variations in absolute reflectance and overall slope. This is probably due to petrologic variations that likely exist within a single CM chondrite, as duplicate spectra for a single subsample show much less spectral variability. When the full suite of available CM spectra is considered, few clear spectral-compositional trends emerge. This indicates that multiple compositional and physical factors affect absolute reflectance, absorption band depths, and absorption band wavelength positions. Asteroids with reflectance spectra that exhibit absorption features consistent with CM spectra (i.e., absorption bands near 0.7 and 0.9 ?m) include members from multiple taxonomic groups. This suggests that on CM parent bodies, aqueous alteration resulted in the consistent production of serpentine-group phyllosilicates, however resulting absolute reflectances and spectral shapes seen in CM reflectance spectra are highly variable, accounting for the presence of phyllosilicate features in reflectance spectra of asteroids across diverse taxonomic groups.

Cloutis, E. A.; Hudon, P.; Hiroi, T.; Gaffey, M. J.; Mann, P.

2011-11-01

422

Visibility of dichalcogenide nanolayers  

OpenAIRE

Dichalcogenides with the common formula MX2 are layered materials with electrical properties that range from semiconducting to superconducting. Here, we describe optimal imaging conditions for the optical detection of ultrathin, two-dimensional dichalcogenide nanocrystals containing single, double and triple layers of MoS2, WSe2 and NbSe2. A simple optical model is used to calculate the contrast for nanolayers deposited on wafers with varying thicknesses of SiO2. The model is extended for ima...

Benameur, M. M.; Radisavljevic, B.; He?ron, J. S.; Sahoo, S.; Berger, H.; Kis, A.

2010-01-01

423

Spectral response data for development of cool coloured tile coverings  

Science.gov (United States)

Most ancient or traditional buildings in Italy show steep-slope roofs covered by red clay tiles. As the rooms immediately below the roof are often inhabited in historical or densely urbanized centres, the combination of low solar reflectance of tile coverings and low thermal inertia of either wooden roof structures or sub-tile insulation panels makes summer overheating a major problem. The problem can be mitigated by using tiles coated with cool colours, that is colours with the same spectral response of clay tiles in the visible, but highly reflecting in the near infrared range, which includes more than half of solar radiation. Cool colours can yield the same visible aspect of common building surfaces, but higher solar reflectance. Studies aimed at developing cool colour tile coverings for traditional Italian buildings have been started. A few coating solutions with the typical red terracotta colour have been produced and tested in the laboratory, using easily available materials. The spectral response and the solar reflectance have been measured and compared with that of standard tiles.

Libbra, Antonio; Tarozzi, Luca; Muscio, Alberto; Corticelli, Mauro A.

2011-03-01

424

Spectral Evolution of an Earth-Like Planet  

CERN Document Server

We have developed a characterization of the geological evolution of the Earths atmosphere and surface in order to model the observable spectra of an Earth-like planet through its geological history. These calculations are designed to guide the interpretation of an observed spectrum of such a planet by future instruments that will characterize exoplanets. Our models focus on spectral features that either imply habitability or are required for habitability. These features are generated by H2O, CO2, CH4, O2, O3, N2O, and vegetation-like surface albedos. We chose six geological epochs to characterize. These epochs exhibit a wide range in abundance for these molecules, ranging from a CO2 rich early atmosphere, to a CO2/CH4-rich atmosphere around 2 billion years ago to a present-day atmosphere. We analyzed the spectra to quantify the strength of each important spectral feature in both the visible and thermal infrared spectral regions, and the resolutions required to unambiguously observe the features for each epoch...

Kaltenegger, L; Jucks, K W

2006-01-01

425

Auroral spectral estimation with wide-band color mosaic CCDs  

Science.gov (United States)

Optical aurora can be structured over a wide range of spatial and temporal scales with spectral features that depend on the energy of precipitating particles. Scientific studies typically combine data from multiple instruments that are individually optimized for spatial, spectral, or temporal resolution. One recent addition combines all-sky optics with color mosaic CCD (charge-coupled device) detectors that use a matrix of different wide-band micro-filters to produce an image with several (often three) color channels. These devices provide sequences of two dimensional multispectral luminosity with simultaneous exposure of all color channels allowing interchannel comparison even during periods with rapidly varying aurora. At present color auroral image data are primarily used for qualitative analysis. In this study a quantitative approach based on Backus-Gilbert linear inversion was used to better understand the effective spectral resolution of existing and proposed instruments. Two spectrally calibrated commercial detectors (Sony ICX285AQ and ICX429AKL) with very different color mosaics (RGB (red, green, blue) vs. CYGM (cyan, yellow, green, magenta)) were found to have very similar spectral resolution: three channels with FWHM (full-width half-maximum) ?100 nm; a NIR (near infrared) blocking filter is important for stabilizing inversion of both three-channel configurations. Operating the ICX429AKL in a noninterlaced mode would improve spectral resolution and provide an additional near infrared channel. Transformations from arbitrary device channels to RGB are easily obtained through inversion. Simultaneous imaging of multiple auroral emissions may be achieved using a single-color camera with a triple-pass filter. Combinations of multiple cameras with simple filters should provide ~50 nm resolution across most of the visible spectrum. Performance of other instrument designs could be explored and compared using the same quantitative framework.

Jackel, B. J.; Unick, C.; Syrjäsuo, M. T.; Partamies, N.; Wild, J. A.; Woodfield, E. E.; McWhirter, I.; Kendall, E.; Spanswick, E.

2014-06-01

426

Visible and UV coherent Raman spectroscopy of dipicolinic acid  

OpenAIRE

We use time-resolved coherent Raman spectroscopy to obtain molecule-specific signals from dipicolinic acid (DPA), which is a marker molecule for bacterial spores. We use femtosecond laser pulses in both visible and UV spectral regions and compare experimental results with theoretical predictions. By exciting vibrational coherence on more than one mode simultaneously, we observe a quantum beat signal that can be used to extract the parameters of molecular motion in DPA. The signal is enhanced ...

Pestov, Dmitry; Zhi, Miaochan; Sariyanni, Zoe-elizabeth; Kalugin, Nikolai G.; Kolomenskii, Alexandre A.; Murawski, Robert; Paulus, Gerhard G.; Sautenkov, Vladimir A.; Schuessler, Hans; Sokolov, Alexei V.; Welch, George R.; Rostovtsev, Yuri V.; Siebert, Torsten; Akimov, Denis A.; Graefe, Stefanie

2005-01-01

427

Design and fabrication of diffraction grating for application in hyperspectral imaging for the long-wavelength infrared spectral region  

Science.gov (United States)

Hyperspectral imaging as an instrument for obtaining a wide range of information on the world around us is a fast developing area of modern technology. In such systems, the desired information is obtained via the processing of stored spectral information of a measured scene. One of the main advantages of hyperspectral imaging over conventional imaging methods is the use of a broad spectral range, which is not restricted to just the visible range but can extend to adjacent regions and further, for example, deeply into the infrared region. The main element in such hyperspectral systems is the spectral separating system, which can be based on a wide variety of spectral dependent physical processes - birefringence, refraction, diffraction, etc. In this contribution, we would like to present the design and fabrication process of such a spectral separating system based on diffraction grating. The main requirements for this system were - operation in the long-wavelength infrared region (LWIR, 7-14 um), the highest possible diffraction efficiency in this spectral region with respect to the bl