WorldWideScience

Sample records for 120-220 nm spectral

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

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

    1999-01-01

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

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

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

  3. Spectral narrowing of a 980 nm tapered diode laser bar

    Vijayakumar, Deepak; Jensen, Ole Bjarlin; Lucas Leclin, Gaëlle;

    2011-01-01

    in wavelength specific applications and hence, it is vital to stabilize the emission spectrum of these devices. In our experiment, we describe the wavelength narrowing of a 12 element 980 nm tapered diode laser bar using a simple Littman configuration. The tapered laser bar which suffered from a big......High power diode laser bars are interesting in many applications such as solid state laser pumping, material processing, laser trapping, laser cooling and second harmonic generation. Often, the free running laser bars emit a broad spectrum of the order of several nanometres which limit their scope...... smile has been "smile corrected" using individual phase masks for each emitter. The external cavity consists of the laser bar, both fast and slow axis micro collimators, smile correcting phase mask, 6.5x beam expanding lens combination, a 1200 lines/mm reflecting grating with 85% efficiency in the first...

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

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

  5. Solar Spectral Irradiance at 782 nm as Measured by the SES Sensor Onboard Picard

    Meftah, M.; Hauchecorne, A.; Irbah, A.; Cessateur, G.; Bekki, S.; Damé, L.; Bolsée, D.; Pereira, N.

    2016-04-01

    Picard is a satellite dedicated to the simultaneous measurement of the total and solar spectral irradiance, the solar diameter, the solar shape, and to the Sun's interior through the methods of helioseismology. The satellite was launched on June 15, 2010, and pursued its data acquisitions until March 2014. A Sun Ecartometry Sensor (SES) was developed to provide the stringent pointing requirements of the satellite. The SES sensor produced an image of the Sun at 782 ± 2.5 nm. From the SES data, we obtained a new time series of the solar spectral irradiance at 782 nm from 2010 to 2014. During this period of Solar Cycle 24, the amplitude of the changes has been of the order of ± 0.08 %, corresponding to a range of about 2× 10^{-3} W m^{-2} nm^{-1}. SES observations provided a qualitatively consistent evolution of the solar spectral irradiance variability at 782 nm. SES data show similar amplitude variations with the semi-empirical model Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE-S), whereas the Spectral Irradiance Monitor instrument (SIM) onboard the SOlar Radiation and Climate Experiment satellite (SORCE) highlights higher amplitudes.

  6. Improved spectral fitting of nitrogen dioxide from OMI in the 405–465 nm window

    Geffen, van J.H.G.M.; Boersma, K.F.; Roozendael, van M.; Hendrick, F.; Mahieu, E.; Smedt, de I.; Sneep, M.; Veefkind, J.P.

    2015-01-01

    An improved nitrogen dioxide (NO2) slant column density retrieval for the Ozone Monitoring Instrument (OMI) in the 405–465 nm spectral region is presented. Since the launch of OMI on board NASA's EOS-Aura satellite in 2004, differential optical absorption spectroscopy (DOAS) retrievals of NO2 slant

  7. Using the electron synchrotron radiation for the calibration of the spectral density in UV and long-wave vacuum UV range (160 nm to 340 nm)

    Electron synchrotron radiation was investigated with a view to the development of methods for the calibration of the spectral density in the UV and long-wave vacuum UV spectral regions. The relative spectral radiation flow of a synchrotron can be calculated over a wide spectral region. In order to determine the absolute radiation flow in the vaccum UV, the synchrotron radiation in the visible region is compared with a reference source (calibrated tungsten filament lamp). Between 160 nm and 340 nm, the spectral beam density calibration with the synchrotron radiation is uncertain by about +- 5%. Between 280 nm and 340 nm, calibrations of deuterium lamps at the synchrotron and at a cavity radiator vary by less than 10%. (orig./WL)

  8. Comparison of Molecular Iodine Spectral Properties at 514.7 and 532 nm Wavelengths

    Hrabina J.

    2014-08-01

    Full Text Available We present results of investigation and comparison of spectral properties of molecular iodine transitions in the spectral region of 514.7 nm that are suitable for laser frequency stabilization and metrology of length. Eight Doppler-broadened transitions that were not studied in detail before were investigated with the help of frequency doubled Yb-doped fiber laser, and three of the most promising lines were studied in detail with prospect of using them in frequency stabilization of new laser standards. The spectral properties of hyperfine components (linewidths, signal-to-noise ratio were compared with transitions that are well known and traditionally used for stabilization of frequency doubled Nd:YAG laser at the 532 nm region with the same molecular iodine absorption. The external frequency doubling arrangement with waveguide crystal and the Yb-doped fiber laser is also briefly described together with the observed effect of laser aging.

  9. Wideband multilayer gratings for the 17-25 nm spectral region.

    Yang, Xiaowei; Kozhevnikov, Igor V; Huang, Qiushi; Wang, Hongchang; Sawhney, Kawal; Wang, Zhanshan

    2016-06-27

    An approach to designing wideband blazed multilayer gratings is introduced and applied to gratings operating at 17-25 nm. We demonstrate single-order operation of broadband multilayer gratings, despite their very wide spectral and angular bandpass, when only one diffraction wave is excited and the diffraction efficiency reaches the reflectivity of a conventional depth-graded multilayer mirror, eliminating overlapping of different-order diffraction waves. The selection principles for the geometrical parameters of gratings are discussed. We formulate a "law of similarity" for wideband gratings that allows us to design gratings with different geometrical parameters but practically the same spectral dependence of the diffraction efficiency. PMID:27410659

  10. Detection of Solar Rotational Variability in the LYRA 190 - 222 nm Spectral Band

    Shapiro, A. V.; Shapiro, A. I.; Dominique, M.; Dammasch, I. E.; Wehrli, C.; Rozanov, E.; Schmutz, W.

    2012-01-01

    We analyze the variability of the spectral solar irradiance during the period from 7 January, 2010 until 20 January, 2010 as measured by the Herzberg channel (190-222 nm) of the Large Yield RAdiometer (LYRA) onboard PROBA2. In this period of time observations by the LYRA nominal unit experienced degradation and the signal produced by the Herzberg channel frequently jumped from one level to another. Both these factors significantly complicates the analysis. We present the algorithm which allow...

  11. Normal spectral emissivity of niobium (at 900 nm) by a pulse-heating reflectometric technique

    The normal spectral emissivity of niobium strip specimens was measured using a new pulse-heating reflectometric technique. The hemispherical spectral reflectivity of the surface of a strip tangent to an integrating sphere is determined by a high-speed lock-in technique. At the same time, the radiance temperature of the strip is measured by high-speed pyrometry from approximately 1,000 K to the melting point. Details of the measurement method and of the related calibration techniques are reported. Results of the normal spectral emissivity of niobium at 900 nm from room temperature to its melting point are presented, discussing differences related to the heating rate and to surface conditions

  12. Optical design of 400-1000nm spectral imaging system based on a single freeform mirror

    Hou, Jia; He, Zhiping; Shu, Rong

    2015-10-01

    The imaging spectrometer supplies spectral images in one spectral dimension and two spatial dimensions simultaneously. The Offner spectral imaging system was outstanding because of its small volume, light weight, free spectral smile and little keystone. However, the manufacture of the convex grating is a challenge and the cost is high. Here, an optical design of a compact 400-1000nm spectral imaging system using a planar grating based on a single freeform mirror was proposed. The spectrograph was similar with the Offner structure, only the grating is planar. The multi-spectra was split by the planar diffraction grating, and the collimating mirror and the focusing mirror were the same freeform surface by using it twice. The freeform surface was non-rotational symmetry. Its large degree of freedom can correct kinds of aberration, such as astigmatism, smile and keystone. The system has a compact volume as 120×100×100mm3. The entrance slit was 6mm, and the object NA(numerical aperture) was 0.12. The pixel size of the detector was 16μm×16μm, and its resolution was 375(spatial)×400(spectral). The design result showed that image quality close to the diffraction limit has been obtained. The maximums of the keystone and the smile at all working wavelengths in all fields were respectively 1.6μm and 7.5μm, which were both less than half of the pixel size. At last, the tolerance analysis considering manufacture and alignment of the system was done, the result showed that the manufacturability of the existing diamond turning machining technology can satisfy the accuracy need of the freeform mirror.

  13. Detection of Solar Rotational Variability in the Large Yield RAdiometer (LYRA) 190 - 222 nm Spectral Band

    Shapiro, A. V.; Shapiro, A. I.; Dominique, M.; Dammasch, I. E.; Wehrli, C.; Rozanov, E.; Schmutz, W.

    2013-08-01

    We analyze the variability of the spectral solar irradiance during the period from 7 January 2010 until 20 January 2010 as measured by the Herzberg channel (190 - 222 nm) of the Large Yield RAdiometer (LYRA) onboard PROBA2. In this period of time, observations by the LYRA nominal unit experienced degradation and the signal produced by the Herzberg channel frequently jumped from one level to another. Both factors significantly complicate the analysis. We present the algorithm that allowed us to extract the solar variability from the LYRA data and compare the results with SORCE/SOLSTICE measurements and with modeling based on the Code for the Solar Irradiance (COSI).

  14. Detection of Solar Rotational Variability in the LYRA 190 - 222 nm Spectral Band

    Shapiro, A V; Dominique, M; Dammasch, I E; Wehrli, C; Rozanov, E; Schmutz, W

    2012-01-01

    We analyze the variability of the spectral solar irradiance during the period from 7 January, 2010 until 20 January, 2010 as measured by the Herzberg channel (190-222 nm) of the Large Yield RAdiometer (LYRA) onboard PROBA2. In this period of time observations by the LYRA nominal unit experienced degradation and the signal produced by the Herzberg channel frequently jumped from one level to another. Both these factors significantly complicates the analysis. We present the algorithm which allowed us to extract the solar variability from the LYRA data and compare the results with SORCE/SOLSTICE measurements and with modeling based on the Code for the Solar Irradiance (COSI).

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

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

  16. 355-nm high spectral resolution airborne lidar LNG: system description and first results.

    Bruneau, D; Pelon, J; Blouzon, F; Spatazza, J; Genau, P; Buchholtz, G; Amarouche, N; Abchiche, A; Aouji, O

    2015-10-10

    A high spectral resolution (HSR) measurement capability in the ultraviolet has been added to the 3-wavelength-2-polarization-backscatter lidar LNG (lidar aerosols nouvelle génération) and tested during several flights. The system includes a Mach-Zehnder interferometer (MZI) as a spectral discriminator and does not require any frequency locking between the emitter and the interferometer. Results obtained during test flights show that the backscatter and extinction coefficients at 355 nm can be measured with a relative precision of 10% for 60 m and 240 m vertical resolution, respectively, in aerosol layers of 10-6  m-1 sr-1 backscatter coefficient with a 30-km horizontal resolution. The same relative precision is obtained in cirrus clouds of a 2×10-5  m-1 sr-1 backscatter coefficient for the same vertical resolution and a horizontal resolution reduced to 5 km. The capacity of the system to perform wind velocity measurements is also demonstrated with precisions in the range of 1 to 2  ms-1. Particle-to-total backscatter ratio and line-of-sight speed measurements have been performed on ground echoes; averaged data show biases less than 1% and 0.15  ms-1, respectively. PMID:26479818

  17. Improved spectral fitting of nitrogen dioxide from OMI in the 405-465 nm window

    van Geffen, J. H. G. M.; Boersma, K. F.; Van Roozendael, M.; Hendrick, F.; Mahieu, E.; De Smedt, I.; Sneep, M.; Veefkind, J. P.

    2015-04-01

    An improved nitrogen dioxide (NO2) slant column density retrieval for the Ozone Monitoring Instrument (OMI) in the 405-465 nm spectral region is presented. Since the launch of OMI on board NASA's EOS-Aura satellite in 2004, differential optical absorption spectroscopy (DOAS) retrievals of NO2 slant column densities have been the starting point for the KNMI DOMINO and NASA SP NO2 vertical column data as well as the OMI NO2 data of some other institutes. However, recent intercomparisons between NO2 retrievals from OMI and other UV/Vis and limb spectrometers, as well as ground-based measurements, suggest that OMI stratospheric NO2 is biased high. This study revises and, for the first time, fully documents the OMI NO2 retrieval in detail. The representation of the OMI slit function to convolve high-resolution reference spectra onto the relevant spectral grid is improved. The window used for the wavelength calibration is optimised, leading to much-reduced fitting errors. Ozone and water vapour spectra used in the fit are updated, reflecting the recently improved knowledge of their absorption cross section in the literature. The improved spectral fit also accounts for absorption by the O2-O2 collision complex and by liquid water over clear-water areas. The main changes in the improved spectral fitting result from the updates related to the wavelength calibration: the RMS error of the fit is reduced by 23% and the NO2 slant column by 0.85 × 1015 molec cm-2, independent of latitude, solar zenith angle and NO2 value. Including O2-O2 and liquid water absorption and updating the O3 and water vapour cross-section spectra further reduces NO2 slant columns on average by 0.35 × 1015 molec cm-2, accompanied by a further 9% reduction in the RMS error of the fit. The improved OMI NO2 slant columns are consistent with independent NO2 retrievals from other instruments to within a range that can be explained by photochemically driven diurnal increases in stratospheric NO2 and by

  18. Multifunctional 1050 nm Spectral Domain OCT System at 147 kHz for Posterior Eye Imaging

    Anqi Zhang

    2015-09-01

    Full Text Available The recent development of optical coherence tomography in ophthalmology has shown great interests in using the system in 1 µm in contrast to 800 nm wavelength range due to the less reflection and absorption of retinal pigment epithelium and pigmented choroidal melanocytes in 1 µm wavelength. The clinical value of using 1 µm system has been demonstrated in choroid imaging, retinal and choroidal microcirculation, etc. By examining different aspects of the posterior eye, the specificity and sensitivity of diagnosis can be increased. On the other hand, higher speed can greatly reduce the measuring time and motion artifacts, which brings comfort to the patients and improves the image quality. In this work, we report a newly developed multifunctional 1050 nm spectral domain optical coherence tomography (SD-OCT system working at 147 kHz A-scan rate for posterior eye imaging. The uniqueness of this system is: 1 its capability of providing not only simultaneous structural imaging of the complete posterior eye, but also the visualization of the retinal blood vessel network with larger field of view and good image quality compared with former SD-OCT systems; 2 it’s fast 147 kHz A-scan rate which has not been reported before. It is demonstrated through in vivo experiments that this system delivers not only superior performance of posterior eye structural imaging but also detailed visualization of microcirculation network in retina. The choroid of the eye with either myopic or normal conditions can clearly be visualized through the entire scanning volume. These results indicate great potential in applying this new system for clinical studies.

  19. Spectral calibration of filters and detectors of solar EUV telescope for 13.2 nm for the TESIS experiment

    The full-sun EUV telescope for 13.2 nm spectral band for the TESIS experiment is designed to produce images of hot coronal plasma (T ∼ 10 MK). Calibration process of optical elements is presented. Spectral transmission of multilayer Zr/Si filters, sensitivity and radiation tolerance of CCD detector have been measured. Peak transmission of EUV filters in working, spectral band reaches 40-50% (filters with 50 and 55 layers are used), spectral dependence of transmission is close to calculated one. Transmission of filters in white light is equal to (1-2)x10-6. Sensitivity of CCD ranges from 0.01 to 0.1 ADC units per photon, radiation tolerance is better than 109 rad

  20. Methane Absorption Coefficients in the 750-940 nm region derived from Intracavity Laser Absorption Spectral Measurements

    O'Brien, J. J.

    2002-09-01

    The absorption spectrum of methane has been recorded in the visible to near-IR region using the intracavity laser spectroscopy technique. Spectra are recorded at high spectral resolution for narrow overlapping intervals in the region for room and 77 K temperature methane samples. After spectra are deconvolved for the instrument function, absorption coefficients are derived. These will be presented (750-940 nm for room temperature methane; 850-920 nm for 77 K methane) and compared with results reported by other workers. Future work in this area also will be indicated. Support from NASA's Planetary Atmospheres Program (NAG5-6091 and a Major Equipment Grant) is gratefully acknowledged.

  1. NUV/Blue spectral observations of sprites in the 320-460 nm region: ${\\mathrm N_2}$ (2PG) Emissions

    Heavner, M J; Siefring, C; Sentman, D D; Moudry, D R; Wescott, E M; Bucsela, E J

    2010-01-01

    A near-ultraviolet (NUV) spectrograph (320-460 nm) was flown on the EXL98 aircraft sprite observation campaign during July 1998. In this wavelength range video rate (60 fields/sec) spectrographic observations found the NUV/blue emissions to be predominantly N2 (2PG). The negligible level of N2+ (1NG) present in the spectrum is confirmed by observations of a co-aligned, narrowly filtered 427.8 nm imager and is in agreement with previous ground-based filtered photometer observations. The synthetic spectral fit to the observations indicates a characteristic energy of ~1.8 eV, in agreement with our other NUV observations.

  2. Full Stokes observations in the He I 1083 nm spectral region covering an M3.2 flare

    Kuckein, C.; Collados, M.; Sainz, R. Manso; Ramos, A. Asensio

    2015-01-01

    We present an exceptional data set acquired with the Vacuum Tower Telescope (Tenerife, Spain) covering the pre-flare, flare, and post-flare stages of an M3.2 flare. The full Stokes spectropolarimetric observations were recorded with the Tenerife Infrared Polarimeter in the He I 1083.0 nm spectral region. The object under study was active region NOAA 11748 on 2013 May 17. During the flare the chomospheric He I 1083.0 nm intensity goes strongly into emission. However, the nearby photospheric Si...

  3. A upper limit for water dimer absorption in the 750 nm spectral region and a revised water line list

    A. J. L. Shillings

    2010-10-01

    Full Text Available The absorption of solar radiation by water dimer molecules in the Earth's atmosphere can potentially act as a positive feedback effect for climate change. There seems little doubt from the results of previous laboratory and theoretical studies that significant concentrations of the water dimer should be present in the atmosphere, yet attempts to detect water dimer absorption signatures in atmospheric field studies have so far yielded inconclusive results. Here we report spectral measurements in the near-infrared in the expected region of the third overtone of the water dimer hydrogen-bonded OHb stretching vibration around 750 nm. The results were obtained using broadband cavity ringdown spectroscopy (BBCRDS, a methodology that allows absorption measurements to be made under controlled laboratory conditions but over absorption path lengths representative of atmospheric conditions. In order to account correctly and completely for overlapping absorption of monomer molecules in the same spectral region, we have also constructed a new list of spectral data (UCL08 for the water monomer in the 750–20 000 cm−1 (13 μm–500 nm range.

    Our results show that the additional lines included in the UCL08 spectral database provide a substantially improved representation of the measured water monomer absorption in the 750 nm region, particularly at wavelengths dominated by weak monomer absorption features. No absorption features which could not be attributed to the water monomer were detected in the BBCRDS experiments up to water mixing ratios more than an order of magnitude greater than those in the ambient atmosphere. The absence of detectable water dimer features leads us to conclude that, in the absence of significant errors in calculated dimer oscillator strengths or monomer/dimer equilibrium constants, the widths of water dimer features present around 750 nm must be substantially greater (~100 cm−1 HWHM than

  4. Simulation of broad spectral bandwidth emitters at 1060 nm for optical coherence tomography

    Tooley, I. G.; Childs, D. T. D.; Stevens, B. J.; Groom, K. M.; Hogg, R. A.

    2016-03-01

    The simulation of broad spectral bandwidth light sources (semiconductor optical amplifiers (SOA) and superluminescent diodes (SLD)) for application in ophthalmic optical coherence tomography is reported. The device requirements and origin of key device parameters are outlined, and a range of single and double InGaAs/GaAs quantum well (QW) active elements are simulated with a view to application in different OCT embodiments. We confirm that utilising higher order optical transitions is beneficial for single QW SOAs, but may introduce deleterious spectral modulation in SLDs. We show how an addition QW may be introduced to eliminate this spectral modulation, but that this results in a reduction of the gain spectrum width. We go on to explore double QW structures where the roles of the two QWs are reversed, with the narrow QW providing long wavelength emission and gain. We show how this modification in the density of states results in a significant increase in gain-spectrum width for a given current.

  5. Full Stokes observations in the He I 1083 nm spectral region covering an M3.2 flare

    Kuckein, C; Sainz, R Manso; Ramos, A Asensio

    2015-01-01

    We present an exceptional data set acquired with the Vacuum Tower Telescope (Tenerife, Spain) covering the pre-flare, flare, and post-flare stages of an M3.2 flare. The full Stokes spectropolarimetric observations were recorded with the Tenerife Infrared Polarimeter in the He I 1083.0 nm spectral region. The object under study was active region NOAA 11748 on 2013 May 17. During the flare the chomospheric He I 1083.0 nm intensity goes strongly into emission. However, the nearby photospheric Si I 1082.7 nm spectral line profile only gets shallower and stays in absorption. Linear polarization (Stokes Q and U) is detected in all lines of the He I triplet during the flare. Moreover, the circular polarization (Stokes V) is dominant during the flare, being the blue component of the He I triplet much stronger than the red component, and both are stronger than the Si I Stokes V profile. The Si I inversions reveal enormous changes of the photospheric magnetic field during the flare. Before the flare magnetic field conc...

  6. Multifunctional 1050 nm Spectral Domain OCT System at 147 kHz for Posterior Eye Imaging

    2015-01-01

    The recent development of optical coherence tomography in ophthalmology has shown great interests in using the system in 1 µm in contrast to 800 nm wavelength range due to the less reflection and absorption of retinal pigment epithelium and pigmented choroidal melanocytes in 1 µm wavelength. The clinical value of using 1 µm system has been demonstrated in choroid imaging, retinal and choroidal microcirculation, etc. By examining different aspects of the posterior eye, the specificity and sens...

  7. Improved compensation of liquid water spectral effects in the DOAS analysis (410-500 nm)

    Peters, Enno; Wittrock, Folkard; Richter, Andreas; Burrows, John P.

    2014-05-01

    It is well known that spectral effects of liquid water are present in DOAS measurements above the ocean. Usually, the effects of surface reflectance are successfully compensated by a broadband polynomial. In addition, the absorption of liquid water and Vibrational Raman Scattering (VRS) in the water body can be considered in the DOAS fit by including the respective (literature) cross-sections. Here, ship-based MAX-DOAS measurements collected during the TransBrom campaign across the Western Pacific in October 2009 are presented. For these observations, the telescope of the instrument was pointing directly into very clear natural sea-water. These measurements were performed in a way minimizing atmospheric contributions to the resulting optical depth while at the same time maximizing the liquid water influence. Average light paths of up to 50 m under water were achieved. Systematic structures were found to remain in DOAS fit residuals in the visible wavelength range even if liquid water spectral effects are included in the fit. It can therefore be concluded that currently available cross-sections compensate liquid water effects only insufficiently in DOAS applications. Thus, empirical correction spectra for uncertainties of currently available liquid water absorption and VRS cross-sections were determined from the MAX-DOAS measurements. The influence of the retrieved correction spectra on fit quality and NO2 slant columns is estimated in MAX-DOAS measurements, both towards the water surface and at small elevation angles above the horizon.

  8. Dual-Frequency 780-nm Ti:Sa Laser for High Spectral Purity Tunable CW THz Generation

    Loas, Goulc'Hen; Romanelli, Marco; Alouini, Mehdi

    2014-01-01

    International audience — A two-axis, two-polarization, dual-frequency Ti:Sa laser optimized for high spectral purity CW-THz generation is demonstrated. The laser output power is 50mW. Its mean emission wavelength is optimized around 780nm in order to suit the maximum efficiency of low temperature grown GaAs photomixers. Despite the extremely wide gain bandwidth of Ti:Sa, a proper intracavity filtering design, adapted to this particular laser architecture, enables tunable and single-frequen...

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

    T. Wagner

    2010-03-01

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

  10. Optical properties of parietal peritoneum in the spectral range 350-2500 nm

    Kozintseva, Marina D.; Bashkatov, Alexey N.; Kochubey, Vyacheslav I.; Genina, Elina A.; Gorodkov, Sergey Y.; Morozov, Dmitry A.; Tuchin, Valery V.

    2014-01-01

    The wide application of optical methods in the areas of diagnostics, therapy and surgery of modern medicine has stimulated the investigation of optical properties of various biological tissues. Numerous investigations related to determination of tissue optical properties are available; however, the optical properties of many tissues have not been studied in a wide wavelength range. In this work the optical properties of parietal peritoneum in the wavelength range 350-2500 nm were measured. Measurement of the diffuse reflectance, total and collimated transmittance were performed using LAMBDA 950 (Perkin Elmer, USA) spectrophotometer with an integrating sphere, and values of absorption and scattering coefficients, and the scattering anisotropy factor were calculated by inverse Monte Carlo Method.

  11. PMMA-based resists for a spectral range near 13 nm

    Bulgakova, S A; Luchin, V I; Mazanova, L M; Molodnjakov, S A; Salashchenko, N N

    2000-01-01

    A number of poly(meth)acrylates positive resists of various chemical structures were synthesized and the sensitivity of 0.2 mu m resists films to soft X-ray radiation of a laser plasma source at a wavelength of 13 nm was investigated. We found that the sensitivity of methylmethacrylate (MMA) copolymers depending on the nature of comonomers changes within the limits of 12.3-1.7 mJ/cm sup 2 in a combination with the contrast gamma=5.4-1.0. This sensitivity is higher than that of PMMA, which changes from 12 to 45 mJ/cm sup 2 at the contrast gamma=2.6-8.0 depending on the developer composition of methylethylketone (MEK)/isopropyl alcohol (IPA).

  12. Spectral emissivity and optical properties at λ= 632.8 nm for liquid uranium and zirconium at high temperatures

    The spectral emissivities, refractive indices, and extinction coefficients of pure liquid uranium and zirconium were measured versus temperature by He-Ne laser polarimetry at a wavelength of 632.8 nm. The experiments were conducted under containerless conditions using electromagnetic leviation and heating supplemented by CO2 laser beam heating. Clean liquid metal surfaces were achieved by heating the specimens to high temperatures at which oxides evaporated and nitrides decomposed. Results were obtained for liquid uranium and zirconium in the temperature ranges 2000-2800 K and 2000-2600 K, respectively and included data for liquid zirconium undercooled by 125 K. The spectral emissivity of zirconium was equal to 0.345 and was independent of temperature. The spectral emissivity of uranium increased with temperature from 0.272 at 2000 K to 0.294 K at 2800 K. The melting temperature of zirconium was determined from its emissivity and apparent melting temperature to be 2125±11 K, in good agreement with values in the literature. (orig.)

  13. Design concepts of monolithic metamorphic vertical-cavity surface-emitting lasers for the 1300–1550 nm spectral range

    Possible design concepts for long-wavelength vertical-cavity surface-emitting lasers for the 1300–1550 nm spectral range on GaAs substrates are suggested. It is shown that a metamorphic GaAs–InGaAs heterostructure with a thin buffer layer providing rapid transition from the lattice constant of GaAs to that of InxGa1–xAs with an indium fraction of x < 0.3 can be formed by molecular-beam epitaxy. Analysis by transmission electron microscopy demonstrated the effective localization of mismatch dislocations in the thin buffer layer and full suppression of their penetration into the overlying InGaAs metamorphic layer

  14. Normal spectral emissivity near 680 nm at melting and in the liquid phase for 18 metallic elements

    Pottlacher, G.; Boboridis, K.; Cagran, C.; Hüpf, T.; Seifter, A.; Wilthan, B.

    2013-09-01

    Optical and thermophysical properties of pure metals at the melting point and in the liquid phase are of general interest for technological applications. This is especially true for those metals that are commonly applied. Many of these elements are used either in their pure form or as alloying components. Due to their widespread use in industry an ongoing need for new and more accurate data exists. Based on an ohmic pulse-heating apparatus, properties of conducting materials can be obtained from temperatures of about 1200 K, at which most metals are in the solid state, up to about 5000 K in the liquid state. To enable a fast and accurate temperature measurement over such a vast range, pyrometric temperature detection based on Planck's radiation law is employed. Furthermore, a microsecond-resolution ellipsometric device with no moving parts, called μs-DOAP (Division-of-Amplitude-Photopolarimeter) as first described by Azzam [1], is applied to measure normal spectral emissivity close to the wavelength of the pyrometer (650 nm). In the present paper, measurements of normal spectral emissivity at 684.5 nm, obtained by means of the above-mentioned pulse-heating technique combined with a μs-DOAP, are summarized for 18 metals, namely cobalt (Co), copper (Cu), gold (Au), hafnium (Hf-3%Zr), iron (Fe), iridium (Ir), molybdenum (Mo), nickel (Ni), niobium (Nb), palladium (Pd), platinum (Pt), rhenium (Re), silver (Ag), tantalum (Ta), titanium (Ti), tungsten (W), vanadium (V) and zirconium (Zr). The results are very important in order to eliminate uncertainties arising from the unknown behavior of emissivity at melting and in the liquid phase when investigating temperature-dependent thermophysical properties.

  15. The Measurement of the Solar Spectral Irradiance Variability at 782 nm during the Solar Cycle 24 using the SES on-board PICARD

    Meftah, Mustapha; Hauchecorne, Alain; Irbah, Abdanour; Bekki, Slimane

    2016-04-01

    A Sun Ecartometry Sensor (SES) was developed to provide the stringent pointing requirements of the PICARD satellite. The SES sensor produced an image of the Sun at 782+/-5 nm. From the SES data, we obtained a new time series of the solar spectral irradiance at 782nm from 2010 to 2014. SES observations provided a qualitatively consistent evolution of the solar spectral irradiance variability at 782 nm during the solar cycle 24. Comparisons will be made with Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE-S) semi-empirical model and with the Spectral Irradiance Monitor instrument (SIM) on-board the Solar Radiation and Climate Experiment satellite (SORCE). These data will help to improve the representation of the solar forcing in the IPSL Global Circulation Model.

  16. Optical coherence microscopy in 1700 nm spectral band for high-resolution label-free deep-tissue imaging.

    Yamanaka, Masahito; Teranishi, Tatsuhiro; Kawagoe, Hiroyuki; Nishizawa, Norihiko

    2016-01-01

    Optical coherence microscopy (OCM) is a label-free, high-resolution, three-dimensional (3D) imaging technique based on optical coherence tomography (OCT) and confocal microscopy. Here, we report that the 1700-nm spectral band has the great potential to improve the imaging depth in high-resolution OCM imaging of animal tissues. Recent studies to improve the imaging depth in OCT revealed that the 1700-nm spectral band is a promising choice for imaging turbid scattering tissues due to the low attenuation of light in the wavelength region. In this study, we developed high-resolution OCM by using a high-power supercontinuum source in the 1700-nm spectral band, and compared the attenuation of signal-to-noise ratio between the 1700-nm and 1300-nm OCM imaging of a mouse brain under the condition of the same sensitivity. The comparison clearly showed that the 1700-nm OCM provides larger imaging depth than the 1300-nm OCM. In this 1700-nm OCM, the lateral resolution of 1.3 μm and the axial resolution of 2.8 μm, when a refractive index was assumed to be 1.38, was achieved. PMID:27546517

  17. Preparation of dental amalgam and spectral diagnosis of mercury in plasmas-laser in the region of 250 nm – 850 nm

    In this paper we presents results of the spectral study of plasmas-laser of dental amalgam by technique Laser-induced Breakdown Spectroscopy (LIBS). Plasmas were generated focusing the beam of a Nd: YAG laser on the matrix of the mixture Ag-Sn-Cu and on amalgams with different proportions of mercury (3:2, 5:2, 6:2). Based on the spectral results and reported atomic parameters, became estimation of electron temperature plasmas- laser and their behavior with the concentration of Hg. The estimated values of the electron temperature for the respective proportions were 20 846 K, 19 139 K and 16 872 K, using the distribution of population of Boltzmann energy levels associated with spectral lines, considering conditions Local Thermodinamic Equilibrium (LTE) of plasmas

  18. Preparation of dental amalgam and spectral diagnosis of mercury in plasmas-laser in the region of 250 nm - 850 nm

    De la Ossa, A.; Pacheco, P.; Sarmiento, R.

    2013-11-01

    In this paper we presents results of the spectral study of plasmas-laser of dental amalgam by technique Laser-induced Breakdown Spectroscopy (LIBS). Plasmas were generated focusing the beam of a Nd: YAG laser on the matrix of the mixture Ag-Sn-Cu and on amalgams with different proportions of mercury (3:2, 5:2, 6:2). Based on the spectral results and reported atomic parameters, became estimation of electron temperature plasmas- laser and their behavior with the concentration of Hg. The estimated values of the electron temperature for the respective proportions were 20 846 K, 19 139 K and 16 872 K, using the distribution of population of Boltzmann energy levels associated with spectral lines, considering conditions Local Thermodinamic Equilibrium (LTE) of plasmas.

  19. Spectral analysis on origination of the bands at 437 nm and 475.5 nm of chlorophyll fluorescence excitation spectrum in Arabidopsis chloroplasts.

    Zeng, Lizhang; Wang, Yongqiang; Zhou, Jun

    2016-05-01

    Chlorophyll fluorescence has been often used as an intrinsic optical molecular probe to study photosynthesis. In this study, the origin of bands at 437 and 475.5 nm in the chlorophyll fluorescence excitation spectrum for emission at 685 nm in Arabidopsis chloroplasts was investigated using various optical analysis methods. The results revealed that this fluorescence excitation spectrum was related to the absorption characteristics of pigment molecules in PSII complexes. Moreover, the excitation band centred at 475.5 nm had a blue shift, but the excitation band at 437 nm changed relatively less due to induction of non-photochemical quenching (NPQ). Furthermore, fluorescence emission spectra showed that this blue shift occurred when excitation energy transfer from both chlorophyll b (Chl b) and carotenoids (Cars) to chlorophyll a (Chl a) was blocked. These results demonstrate that the excitation band at 437 nm was mainly contributed by Chl a, while the excitation band at 475.5 nm was mainly contributed by Chl b and Cars. The chlorophyll fluorescence excitation spectrum, therefore, could serve as a useful tool to describe specific characteristics of light absorption and energy transfer between light-harvesting pigments. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26358732

  20. Relationship of 2 100-2 300 nm Spectral Characteristics of Wheat Canopy to Leaf Area Index and Leaf N as Affected by Leaf Water Content

    ZHAO Chun-Jiang; WANG Ji-Hua; LIU Liang-Yun; HUANG Wen-Jiang; ZHOU Qi-Fa

    2006-01-01

    The effects of leaf water status in a wheat canopy on the accuracy of estimating leaf area index (LAI) and N were determined in this study using extracted spectral characteristics in the 2 000-2 300 nm region of the short wave infrared (SWI) band. A newly defined spectral index, relative adsorptive index in the 2 000-2 300 nm region (RAI2000-2300), which can be calculated by RAI2000-2300 = (R2224 - R2054) (R2224 + R2054)-1 with R being the reflectance at 2 224 or2 054 nm, was utilized. This spectral index, RAI2000-2300, was significantly correlated (P < 0.01) with green LAI and leaf N concentration and proved to be potentially valuable for monitoring plant green LAI and leaf N at the field canopy scale. Moreover, plant LAI could be monitored more easily and more successfully than plant leaf N. The study also showed that leaf water had a strong masking effect on the 2 000-2 300 nm spectral characteristics and both the coefficient between RAI2000-2300 and green LAI and that between RAI2000-2300 and leaf N content decreased as leaf water content increased.

  1. Portable multispectral imaging system based on light-emitting diodes for spectral recovery from 370 to 1630 nm.

    Herrera-Ramírez, Jorge; Vilaseca, Meritxell; Pujol, Jaume

    2014-05-10

    To expand and investigate the potential of spectral imaging, we developed a portable multispectral system using light-emitting diodes. This system recovers spectral information from the UV to the near IR over a large area using two different image sensors synchronized with 23 bands of illumination. The system was assessed for spectral reconstruction through simulations and experimental measurements by means of two methods of spectral reconstruction and three different evaluation metrics. The results over a Macbeth ColorChecker chart and other samples, including pigments usually employed in art paintings, are compared and discussed. The portable multispectral system using LEDs constitutes a cost-effective and versatile method for spectral imaging. PMID:24922036

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

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

    2007-10-15

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

  3. Study of two-photon resonant four-wave sum mixing in xenon in the spectral region of 105-110 nm

    Graphical abstract: Two-photon resonant four-wave mixing in Xe gaseous medium was studied by subjecting a variety of molecular samples, including acetone, furan, thiophene, triethylamine, and dimethylsilacyclobutane, to the laser sources produced for ionization. The peak positions and widths of the five spectral regions between 105 and 110 nm where four-wave sum mixing in Xe occurs were characterized. Research highlights: → VUV radiation (105-110 nm) is produced by nonlinear four-wave mixing in xenon. → The peak positions and widths of five possible spectral regions are characterized. → The previous reported VUV region of 113-117 nm is extended to shorter wavelength. - Abstract: The two-photon resonant four-wave sum and difference mixing in Xe gaseous medium was studied by subjecting a variety of molecular samples, including acetone, furan, thiophene, triethylamine, and dimethylsilacyclobutane, to the coherent radiation sources produced from the four-wave mixing processes for ionization. Ionization of all samples studied showed similar behavior and is due to the laser radiation from four-wave sum mixing. It is demonstrated that in a vacuum ultraviolet (VUV) spectral region of 105-110 nm four-wave sum mixing in Xe can only occur in five discontinued regions, all of which are to the blue of a Xe atomic transition. The peak positions and widths of the five spectral regions were characterized. Study of the triethylamine sample with its ionization energy lower than the photon energy of the VUV radiation from the difference mixing illustrated the competition between the sum and difference mixing occurring simultaneously in the Xe gas cell.

  4. Mars 1064 nm spectral radiance measurements determined from the receiver noise response of the Mars Orbiter Laser Altimeter.

    Sun, Xiaoli; Neumann, Gregory A; Abshire, James B; Zuber, Maria T

    2006-06-10

    A technique was developed to compute the radiance of the scene viewed by the optical receiver of the Mars Orbiter Laser Altimeter. The technique used the detection threshold and the false detection rate of the receiver to provide a passive radiometry measurement of Mars at the 1064 nm wavelength over a 2 nm bandwidth and subkilometer spatial resolution in addition to the altimetry and active radiometry measurements. The passive radiometry measurement is shown to have a 2% or better precision and has been stable over several Martian years. We describe the principle of operation of the instrument and its calibration and assess its performance from sample orbital measurements. PMID:16761033

  5. Method of Express Analysis of Temporal Evolution of the Spectral and Angular Distributions of Seps during Gles Using NM Data

    Mishev, Alexander; Usoskin, Ilya

    It is important for space weather studies to be estimate radiation environment during major SEP (solar energetic particle) events. For this purpose, the main characteristics, viz. spectra and anisotropy of SEPs, should be derived in near real time. Here we present a method for a quasi-real time analysis of ground level enhancements using neutron monitor (NM) data. The method is based on a precise computations of SEP propagation in the Earth's magnetosphere, namely the assymptotic cones of acceptance of NM, application of the new computed neutron monitor yield function and non-linear optimization. Several examples and a comparison with previously obtained results as well with full scale modeling are demonstrated.

  6. Clay composition and swelling potential estimation of soils using depth of absorption bands in the SWIR (1100-2500 nm) spectral domain

    Dufréchou, Grégory; Granjean, Gilles; Bourguignon, Anne

    2014-05-01

    Swelling soils contain clay minerals that change volume with water content and cause extensive and expensive damage on infrastructures. Presence of clay minerals is traditionally a good estimator of soils swelling and shrinking behavior. Montmorillonite (i.e. smectite group), illite, kaolinite are the most common minerals in soils and are usually associated to high, moderate, and low swelling potential when they are present in significant amount. Characterization of swelling potential and identification of clay minerals of soils using conventional analysis are slow, expensive, and does not permit integrated measurements. SWIR (1100-2500 nm) spectral domain are characterized by significant spectral absorption bands related to clay content that can be used to recognize main clay minerals. Hyperspectral laboratory using an ASD Fieldspec Pro spectrometer provides thus a rapid and less expensive field surface sensing that permits to measure soil spectral properties. This study presents a new laboratory reflectance spectroscopy method that used depth of clay diagnostic absorption bands (1400 nm, 1900 nm, and 2200 nm) to compare natural soils to synthetic montmorillonite-illite-kaolinite mixtures. We observe in mixtures that illite, montmorillonite, and kaolinite content respectively strongly influence the depth of absorption bands at 1400 nm (D1400), 1900 nm (D1900), and 2200 nm (D2200). To attenuate or removed effects of abundance and grain size, depth of absorption bands ratios were thus used to performed (i) 3D (using D1900/D2200, D1400/D1900, and D2200/D1400 as axis), and (ii) 2D (using D1400/D1900 and D1900/D2200 as axis) diagrams of synthetic mixtures. In this case we supposed that the overall reduction or growth of depth absorption bands should be similarly affected by the abundance and grain size of materials in soil. In 3D and 2D diagrams, the mixtures define a triangular shape formed by two clay minerals as external envelop and the three clay minerals mixtures

  7. Diode laser-based trace detection of hydrogen-sulfide at 2646.3 nm and hydrocarbon spectral interference effects

    Sharma, Rachit; Mitra, Chayan; Tilak, Vinayak

    2016-03-01

    This paper presents the first diode laser-based measurements of trace hydrogen sulfide at the 2646.35 nm absorption line and evaluates the feasibility of this line for natural gas sensing applications. The balanced detection technique is used to achieve a detection limit of 25 parts per million-meter H2S in 150 Torr (T) balance N2. Spectral interference effects of major natural gas constituents (methane, ethane, and propane) are also presented. It is shown that methane interference can be avoided by lowering the sample pressure, while propane has no interference. However, strong interfering lines of ethane are observed around the 2646.35 nm region. To our knowledge, this is the first report where individual ethane lines in this spectral region are observed. These observations make the 2646.35 nm H2S line unfavorable for natural gas applications. This line, however, still remains attractive for H2S sensing applications with low ethane content.

  8. Mars 1064-nm Spectral Radiance Measurements from the Receiver Noise Response of the Mars Orbiter Laser Altimeter

    Sun, Xiaoli; Neumann, Gregory A.; Abshire, James B.; Zuber, Maria T.

    2005-01-01

    The Mars Orbiter Laser Altimeter not only provides surface topography from the laser pulse time-of-flight, but also two radiometric measurements, the active measurement of transmitted and reflected laser pulse energy, and the passive measurement of reflected solar illumination. The passive radiometry measurement is accomplished in a novel fashion by monitoring the noise density at the output of the photodetector and solving for the amount of background light. The passive radiometry measurements provide images of Mars at 1064-nm wavelength over a 2 nm bandwidth with sub-km spatial resolution and with 2% or better precision under full illumination. We describe in this paper the principle of operation, the receiver mathematical model, its calibration, and performance assessment from sample measurement data.

  9. Generation of spectrally-stable continuous-wave emission and ns pulses at 800 nm and 975 nm with a peak power of 4 W using a distributed Bragg reflector laser and a ridge-waveguide power amplifier

    Klehr, A.; Wenzel, H.; Fricke, J.; Bugge, F.; Liero, A.; Hoffmann, Th.; Erbert, G.; Tränkle, G.

    2015-03-01

    Semiconductor based sources which emit high-power spectrally stable nearly diffraction-limited optical pulses in the nanosecond range are ideally suited for a lot of applications, such as free-space communications, metrology, material processing, seed lasers for fiber or solid state lasers, spectroscopy, LIDAR and frequency doubling. Detailed experimental investigations of 975 nm and 800 nm diode lasers based on master oscillator power amplifier (MOPA) light sources are presented. The MOPA systems consist of distributed Bragg reflector lasers (DBR) as master oscillators driven by a constant current and ridge waveguide power amplifiers which can be driven DC and by current pulses. In pulse regime the amplifiers modulated with rectangular current pulses of about 5 ns width and a repetition frequency of 200 kHz act as optical gates, converting the continuous wave (CW) input beam emitted by the DBR lasers into a train of short optical pulses which are amplified. With these experimental MOPA arrangements no relaxation oscillations in the pulse power occur. With a seed power of about 5 mW at a wavelength of 973 nm output powers behind the amplifier of about 1 W under DC injection and 4 W under pulsed operation, corresponding to amplification factors of 200 (amplifier gain 23 dB) and 800 (gain 29 dB) respectively, are reached. At 800 nm a CW power of 1 W is obtained for a seed power of 40 mW. The optical spectra of the emission of the amplifiers exhibit a single peak at a constant wavelength with a line width 50 dB. The output beams are nearly diffraction limited with beam propagation ratios M2lat ~ 1.1 and M2ver ~ 1.2 up to 4 W pulse power.

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

    Li, Peng; Johnstone, Murray; Ruikang K Wang

    2014-01-01

    Abstract. We demonstrate an extended-imaging-range anterior-segment optical coherence tomography (eAS-OCT) system for the biometric assessment of full AS in human eye. This newly developed eAS-OCT operating at 1340-nm wavelength band is simultaneously capable of an imaging speed of 120 kHz A-line scan rate, an axial resolution of 7.2 μm, and an extended imaging range of up to 16 mm in air. Imaging results from three healthy subjects and one subject with a narrow-angle demonstrate the instrume...

  11. Assessment of the CALIPSO Lidar 532 nm attenuated backscatter calibration using the NASA LaRC airborne High Spectral Resolution Lidar

    R. R. Rogers

    2011-02-01

    Full Text Available The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO spacecraft has provided global, high-resolution vertical profiles of aerosols and clouds since it became operational on 13 June 2006. On 14 June 2006, the NASA Langley Research Center (LaRC High Spectral Resolution Lidar (HSRL was deployed aboard the NASA Langley B-200 aircraft for the first of a series of 86 underflights of the CALIPSO satellite to provide validation measurements for the CALIOP data products. To better assess the range of conditions under which CALIOP data products are produced, these validation flights were conducted under both daytime and nighttime lighting conditions, in multiple seasons, and over a large range of latitudes and aerosol and cloud conditions. This paper presents a quantitative assessment of the CALIOP 532 nm calibration (through the 532 nm total attenuated backscatter using internally calibrated airborne HSRL underflight data and is the most extensive study of CALIOP 532 nm calibration. Results show that HSRL and CALIOP 532 nm total attenuated backscatter agree on average within 2.7% ± 2.1% (CALIOP lower at night and within 2.9% ± 3.9% (CALIOP lower during the day, demonstrating the accuracy of the CALIOP 532 nm calibration algorithms. Additionally, comparisons with HSRL show consistency of the CALIOP calibration before and after the laser switch in 2009 as well as improvements in the daytime version 3.01 calibration scheme compared with the version 2 calibration scheme. Potential biases and uncertainties in the methodology relevant to validating satellite lidar measurements with an airborne lidar system are discussed and found to be less than 4.5% ± 3.2% for this validation effort with HSRL. Results from this study are also compared with prior assessments of the CALIOP 532 nm attenuated backscatter calibration.

  12. Airborne differential absorption lidar for water vapour measurements in the upper troposphere and lower stratosphere in the spectral region around 940 nm

    Poberaj, G.

    2000-07-01

    Two all-solid-state laser systems were developed and studied in detail to optimise their performance for an airborne water vapour differential absorption lidar (DIAL). Their special features are high average output powers and excellent spectral properties in the 940-nm spectral region relevant for monitoring very low water vapour contents in the upper troposphere and lower stratosphere. One system is an injection-seeded pulsed Ti:sapphire ring laser with a spectral bandwidth of 105 MHz and an average power of 1.1 W. The other system is an injection-seeded optical parametric oscillator (OPO) in a ring configuration. Using KTP as nonlinear crystal, a signal output with a spectral bandwidth of 140 MHz and an average power of 1.2 W was achieved. Both systems, the Ti:sapphire ring laser and the KTP OPO, possess spectral purity values higher than 99%. The pump source for these systems is a frequency doubled diode-pumped Nd:YAG laser operating at a repetition rate of 100 Hz. The KTP OPO system has been used as a transmitter in a new airborne water vapour DIAL instrument. For the first time, measurements of two-dimensional water vapour distributions with a high vertical (500 m) and horizontal (20 km) resolution across several potential vorticity streamers were performed. Very low water vapour mixing ratios (10-50 ppmv) and strong gradients were observed in the tropopause region. The sensitivity of the DIAL instrument in the centre of a stratospheric intrusion ranges from 3% in the near field to 12% in the far field (4 km). The first comparison experiments with in situ measuring instruments show a good agreement. Considerable differences are found between DIAL measurements and data obtained from the ECMWF operational analyses and a mesoscale numerical model. (orig.)

  13. Metamorphic distributed Bragg reflectors for the 1440–1600 nm spectral range: Epitaxy, formation, and regrowth of mesa structures

    Egorov, A. Yu., E-mail: anton@beam.ioffe.ru; Karachinsky, L. Ya.; Novikov, I. I.; Babichev, A. V. [Ioffe Institute (Russian Federation); Berezovskaya, T. N. [Russian Academy of Sciences, Saint Petersburg National Research Academic University (Russian Federation); Nevedomskiy, V. N. [Ioffe Institute (Russian Federation)

    2015-10-15

    It is shown that metamorphic In{sub 0.3}Ga{sub 0.7}As/In{sub 0.3}Al{sub 0.7}As distributed Bragg reflectors (DBRs) with a reflection band at 1440–1600 nm and a reflectance of no less than 0.999 can be fabricated by molecular beam epitaxy (MBE) on a GaAs substrate. It is demonstrated that mesa structures formed from metamorphic DBRs on a GaAs substrate can be regrown by MBE and microcavities can be locally formed in two separate epitaxial processes. The results obtained can find wide application in the fabrication of vertical-cavity surface-emitting lasers (VCSELs) with a buried tunnel junction.

  14. Assessment of the CALIPSO Lidar 532 nm Attenuated Backscatter Calibration Using the NASA LaRC Airborne High Spectral Resolution Lidar

    Rogers, Raymond R.; Hostetler, Chris A.; Hair, Johnathan W.; Ferrare, Richard A.; Liu, Zhaoyan; Obland, Michael D.; Harper, David B.; Cook, Anthony L.; Powell, Kathleen A.; Vaughan, Mark A.; Winker, David M.

    2011-01-01

    The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) spacecraft has provided global, high-resolution vertical profiles of aerosols and clouds since it became operational on 13 June 2006. On 14 June 2006, the NASA Langley Research Center (LaRC) High Spectral Resolution Lidar (HSRL) was deployed aboard the NASA Langley B-200 aircraft for the first of a series of 86 underflights of the CALIPSO satellite to provide validation measurements for the CALIOP data products. To better assess the range of conditions under which CALIOP data products are produced, these validation flights were conducted under both daytime and nighttime lighting conditions, in multiple seasons, and over a large range of latitudes and aerosol and cloud conditions. This paper presents a quantitative assessment of the CALIOP 532 nm calibration (through the 532 nm total attenuated backscatter) using an internally calibrated airborne HSRL underflight data and is the most extensive study of CALIOP 532 nm calibration. Results show that average HSRL and CALIOP 532 nm total attenuated backscatter agree on average within 2.7% +/- 2.1% (CALIOP lower) at night and within 2.9 % +/- 3.9% (CALIOP lower) during the day., demonstrating the accuracy of the CALIOP 532 nm calibration algorithms. Additionally, comparisons with HSRL show consistency of the CALIOP calibration before and after the laser switch in 2009 as well as improvements in the daytime version 3 calibration scheme compared with the version 2 calibration scheme. Potential systematic uncertainties in the methodology relevant to validating satellite lidar measurements with an airborne lidar system are discussed and found to be less than 3.7% for this validation effort with HSRL. Results from this study are also compared to those from prior assessments of CALIOP calibration and attenuated backscatter.

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

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

    2014-07-01

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

  16. Direct spectral analysis of tea samples using 266 nm UV pulsed laser-induced breakdown spectroscopy and cross validation of LIBS results with ICP-MS.

    Gondal, M A; Habibullah, Y B; Baig, Umair; Oloore, L E

    2016-05-15

    Tea is one of the most common and popular beverages spanning vast array of cultures all over the world. The main nutritional benefits of drinking tea are its anti-oxidant properties, presumed protection against certain cancers, inhibition of inflammation and possible protective effects against diabetes. Laser induced breakdown spectrometer (LIBS) was assembled as a powerful tool for qualitative and quantitative analysis of various brands of tea samples using 266 nm pulsed UV laser. LIBS spectra for six brands of tea samples in the wavelength range of 200-900 nm was recorded and all elements present in our tea samples were identified. The major toxic elements detected in several brands of tea samples were bromine, chromium and minerals like iron, calcium, potassium and silicon. The spectral assignment was conducted prior to the determination of concentration of each element. For quantitative analysis, calibration curves were drawn for each element using standard samples prepared in known concentration in the tea matrix. The plasma parameters (electron temperature and electron density) were also determined prior to the tea samples spectroscopic analysis. The concentration of iron, chromium, potassium, bromine, copper, silicon and calcium detected in all tea samples was between 378-656, 96-124, 1421-6785, 99-1476, 17-36, 2-11 and 92-130 mg L(-1) respectively. The limits of detection estimated for Fe, Cr, K, Br, Cu, Si, Ca in tea samples were 22, 12, 14, 11, 6, 1 and 12 mg L(-1) respectively. To further confirm the accuracy of our LIBS results, we determined the concentration of each element present in tea samples by using standard analytical technique like ICP-MS. The concentrations detected with our LIBS system are in excellent agreement with ICP-MS results. The system assembled for spectral analysis in this work could be highly applicable for testing the quality and purity of food and also pharmaceuticals products. PMID:26992530

  17. Isotope shift measurements in the 660 spectral lines of Er I covering the 340-605 nm wavelength region with a Fourier Transform Spectrometer

    Ankush, B. K.; Deo, M. N.

    2015-04-01

    Isotope shift measurements in 660 spectral lines covering the 340-605 nm wavelength region of Er I were carried out using a Fourier Transform Spectrometer. The spectra were recorded using a liquid nitrogen cooled hollow cathode discharge source containing highly enriched 166Er and 170Er isotopes in the oxide form and two different detectors namely PMT and silicon photo diodes. Out of 660 spectral lines involving 216 even and 182 odd Er I levels, the isotope shift data were new in the 406 lines. On the basis of their level isotope shifts out of 114 unassigned even parity levels 27 levels assigned to 4f116s26p, 72 to 4f115d6s6p and 15 to 4f126s6d configuration whereas 12 each of unassigned odd parity levels assigned to 4f115d6s2, and 4f126s6p configurations and 16 unassigned odd parity levels assigned to 4f115d26s configuration. Configuration mixing for 30 odd parity energy levels has been theoretically calculated applying 'Sharing Rule' to the experimentally derived level isotope shifts, which were finally compared with mixings available in the literature.

  18. Isotope shift measurements in the 660 spectral lines of Er I covering the 340–605 nm wavelength region with a Fourier Transform Spectrometer

    Isotope shift measurements in 660 spectral lines covering the 340–605 nm wavelength region of Er I were carried out using a Fourier Transform Spectrometer. The spectra were recorded using a liquid nitrogen cooled hollow cathode discharge source containing highly enriched 166Er and 170Er isotopes in the oxide form and two different detectors namely PMT and silicon photo diodes. Out of 660 spectral lines involving 216 even and 182 odd Er I levels, the isotope shift data were new in the 406 lines. On the basis of their level isotope shifts out of 114 unassigned even parity levels 27 levels assigned to 4f116s26p, 72 to 4f115d6s6p and 15 to 4f126s6d configuration whereas 12 each of unassigned odd parity levels assigned to 4f115d6s2, and 4f126s6p configurations and 16 unassigned odd parity levels assigned to 4f115d26s configuration. Configuration mixing for 30 odd parity energy levels has been theoretically calculated applying ‘Sharing Rule’ to the experimentally derived level isotope shifts, which were finally compared with mixings available in the literature. - Highlights: • Isotope shifts in 660 spectral lines of Er I presented. • Isotope shifts in 406 lines reported for the first time. • Even levels assigned to 4f116s26p, 4f115d6s6p and 4f126s6d configurations. • 12 each of odd levels assigned to 4f115d6s2 and 4f126s6p configurations. • Configuration mixing compositions derived for 30 odd levels using ‘Sharing Rule’

  19. Hyperfine structure analysis in the intense spectral lines of the neutral Cu atom falling in the 353–809 nm wavelength region using a Fourier transform spectrometer

    Hyperfine structure analyses have been performed in the high-resolution spectrum of the neutral copper atom covering the wavelength region of 353–809 nm using Fourier transform spectroscopy. A DC discharge of natural copper produced in a liquid nitrogen cooled hollow cathode lamp used as a light source and a photomultiplier tube as well as Si photodiodes were employed as the light detectors. The hfs studies in 17 transitions of the neutral copper atom originating from 17 energy levels for 63Cu have been reported here. The present investigation has provided the magnetic dipole coupling constant A and electric quadrupole coupling constant B for the first time for the following 6 even-parity levels lying at 49,935, 49,942 cm−1, of 3d104d configuration, 52,848 cm−1 of 3d106 s configuration, 55,387, 55,391 cm−1 3d105d configuration and 71,978 cm−1 of 3d104s4d configuration. The sign convention of the previously-reported hfs A value amounting to 1920 MHz for the level at 44,963 cm−1 of 3d94s4p configuration has been revised to −1920 MHz. Measurements reported earlier of A and B hfs constants for the 11 odd-parity energy levels also have been confirmed. -- Highlights: • An improved list of ‘A’ and ‘B’ hyperfine structure constants for Cu-63 is presented. • The sign of the ‘A’ hfs constant of 44,963 cm−1 3d94s4p was changed from +1920 to −1920 MHz. • ‘A’ and ‘B’ hfs constants for the six energy levels are reported for the first time. • Over 17 spectral lines have been measured in the 353–809 nm wavelength region

  20. Realization of band gap shrinkage to the spectral characteristics of high-luminous-efficiency 658 nm AlGaInP/GaInP multiple quantum well lasers at room temperatures

    Chackrabarti, Santosh; Zargar, Rayees A.; Bansal, Jyoti; Zaker, Tho-alfiqar A.; Hafiz, A. K.

    2016-08-01

    The temperature dependent spectral shifts in 658 nm AlGaInP multiple quantum well (MQW) red laser diodes due to band gap narrowing at room temperatures (5 °Csbnd 45 °C) is reported. The density of states effective mass approximation and the conduction band effective mass approximation are employed to formulate the carrier concentrations. The spectral shift mechanism is explored with a threshold current density of 42.28 kA/cm2 and a good characteristic temperature of 149 K. The photoluminescence (PL) peak intensity shifts towards the higher wavelength(red shift) and the full width at half maximum (FWHM) increases with the increase in temperature. The band gap narrowing value determined by a simple formula amounts to 67.4 meV and displays N1/3 dependence at higher densities. The carrier density dependence conveys that the red shift of the spectral emission is due to band gap narrowing.

  1. New Sub-nanometer Spectral Estimates of the 0-5 nm Solar Soft X-Ray Irradiance at Mars Using the Extreme UltraViolet Monitor (EUVM) Onboard MAVEN

    Thiemann, E.; Eparvier, F. G.; Chamberlin, P. C.; Woods, T. N.; Peterson, W. K.; Mitchell, D. L.; Xu, S.; Liemohn, M. W.

    2015-12-01

    characterize the effectiveness of this technique, we compare Mars atmospheric photoelectron spectral measurements made by MAVEN's Solar Wind Electron Analyzer (SWEA) against modeled photoelectron spectra which use the EUVM derived 0-5 nm solar spectrum as an input.

  2. Assessment of the CALIPSO Lidar 532 nm attenuated backscatter calibration using the NASA LaRC airborne High Spectral Resolution Lidar

    R. R. Rogers; C. A. Hostetler; J. W. Hair; R. A. Ferrare; Liu, Z.; Obland, M. D.; Harper, D. B.; Cook, A. L.; K.A. Powell; M. A. Vaughan; Winker, D. M.

    2011-01-01

    The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) spacecraft has provided global, high-resolution vertical profiles of aerosols and clouds since it became operational on 13 June 2006. On 14 June 2006, the NASA Langley Research Center (LaRC) High Spectral Resolution Lidar (HSRL) was deployed aboard the NASA Langley B-200 aircraft for the first of a series of 86 underflights of the CALIPSO...

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

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

    2007-01-01

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

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

    Ao Huilan; Xing Da; Wei Huajiang; Gu Huaimin [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, ina Normal University, Guangzhou 510631 (China); Wu Guoyong; Lu Jianjun [Department of Surgery, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou 510080 (China)], E-mail: xingda@scnu.edu.cn

    2008-04-21

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

  5. Simultaneous quantum dash-well emission in a chirped dash-in-well superluminescent diode with spectral bandwidth >700 nm

    Khan, Mohammed Zahed Mustafa

    2013-10-01

    We report on the quantitative evidence of simultaneous amplified spontaneous emission from the AlGaInAs/InAs/ InP-based quantum-well (Qwell) and quantum-dashes (Qdash) in a multistack dash-in-an-asymmetric-well superluminescent diode heterostructure. As a result, an emission bandwidth (full width at half-maximum) of 700 nm is achieved, covering entire O-E-S-C-L-U communication bands, and a maximum continuous wave output power of 1.3 mW, from this device structure. This demonstration paves a way to bridge entire telecommunication bands through proper optimization of device gain region, bringing significant advances and impact to a variety of cross-disciplinary field applications. © 2013 Optical Society of America.

  6. Temporal Evolution of Spectral and Angular Characteristics of SEP Particles during Several GLEs of Solar Cycle 23 Derived from NM Data

    Mishev, Alexander; Usoskin, Ilya; Kocharov, Leon

    High-energy charged particles of solar origin could represent a severe radiation risk for astronauts and air crew. In addition, they could disrupt technological systems. When a ground-based neutron monitor register abrupt increases in solar energetic particles (SEPs), we observe a special case of solar energetic particle event, a ground-level enhancement (GLE). In order to derive the spectral and angular characteristics of GLE particles a precise computation of solar energetic particle propagation in the Earth's magnetosphere and atmosphere is necessary. It consists of detailed computation of assymptotic cones for neutron monitors (NMs) and application of inverse method using the newly computed neutron monitor yield function. Assymptotic directions are computed using the Planetocosmics code and realistic magnetospheric models, namely IGRF as the internal model and Tsyganenko 89 with the corresponding Kp index as the external one. The inverse problem solution is performed on the basis of non-linear least squares method, namely Levenberg-Marqurdt. In the study presented here, we analyse several major GLEs of the solar cycle 23 as well as the first GLE event of the solar cycle 24, namely GLE69, GLE70 and GLE 71. The SEP spectra and pitch angle distribution are obtained at different momenta since the event's onset. The obtained characteristics are compared with previously reported results. The obtained results are briefly discussed.

  7. Hyperfine structure analysis in the intense spectral lines of the neutral Cu atom falling in the 353-809 nm wavelength region using a Fourier transform spectrometer

    Ankush, B. K.; Deo, M. N.

    2014-02-01

    Hyperfine structure analyses have been performed in the high-resolution spectrum of the neutral copper atom covering the wavelength region of 353-809 nm using Fourier transform spectroscopy. A DC discharge of natural copper produced in a liquid nitrogen cooled hollow cathode lamp used as a light source and a photomultiplier tube as well as Si photodiodes were employed as the light detectors. The hfs studies in 17 transitions of the neutral copper atom originating from 17 energy levels for 63Cu have been reported here. The present investigation has provided the magnetic dipole coupling constant A and electric quadrupole coupling constant B for the first time for the following 6 even-parity levels lying at 49,935, 49,942 cm-1, of 3d104d configuration, 52,848 cm-1 of 3d106 s configuration, 55,387, 55,391 cm-1 3d105d configuration and 71,978 cm-1 of 3d104s4d configuration. The sign convention of the previously-reported hfs A value amounting to 1920 MHz for the level at 44,963 cm-1 of 3d94s4p configuration has been revised to -1920 MHz. Measurements reported earlier of A and B hfs constants for the 11 odd-parity energy levels also have been confirmed.

  8. Radical quantum yields from formaldehyde photolysis in the 30,400-32,890 cm(-1) (304-329 nm) spectral region: detection of radical photoproducts using pulsed laser photolysis-pulsed laser induced fluorescence.

    Tatum Ernest, Cheryl; Bauer, Dieter; Hynes, Anthony J

    2012-07-01

    The relative quantum yield for the production of radical products, H + HCO, from the UV photolysis of formaldehyde (HCHO) has been measured using a pulsed laser photolysis–pulsed laser induced fluorescence (PLP–PLIF) technique across the 30,400–32,890 cm(–1) (304–329 nm) spectral region of the Ã(1)A2–X̃(1)A1 electronic transition. The photolysis laser had a bandwidth of 0.09 cm(–1), which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (0.07 cm(–1)), and the yield spectrum shows detailed rotational structure. The H and HCO photofragments were monitored using LIF of the OH radical as a spectroscopic marker. The OH radicals were produced by rapid reaction of the H and HCO photofragments with NO2. This technique produced an “action” spectrum that at any photolysis wavelength is the product of the H + HCO radical quantum yield and HCHO absorption cross section at the photolysis wavelength and is a relative measurement. Using the HCHO absorption cross section previously obtained in this laboratory, the relative quantum yield was determined two different ways. One produced band specific yields, and the other produced yields averaged over each 100 cm(–1). Yields were normalized to a value of 0.69 at 31,750 cm(–1) based on the current recommendation of Sander et al. (Sander, S. P.; Abbatt, J.; Barker, J. R.; Burkholder, J. B.; Friedl, R. R.; Golden, D. M.; Huie, R. E.; Kolb, C. E.; Kurylo, M. J.; Moortgat, G. K.; et al. Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation No. 17; Jet Propulsion Laboratory: Pasadena, CA, USA, 2011). The resulting radical quantum yields agree well with previous experimental studies and the current JPL recommendation but show greater wavelength dependent structure. A significant decrease in the quantum yield was observed for the 5(0)(1) + 1(0)(1)4(0)(1) combination band centered at 31,125 cm(–1). This band has a low absorption cross section and

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

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

    2014-09-01

    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 λ = 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.

  10. The spectral shift function and spectral flow

    Azamov, N. A.; Carey, A. L.; Sukochev, F. A.

    2007-01-01

    This paper extends Krein's spectral shift function theory to the setting of semifinite spectral triples. We define the spectral shift function under these hypotheses via Birman-Solomyak spectral averaging formula and show that it computes spectral flow.

  11. Measurements of spectral snow albedo at Neumayer, Antarctica

    S. Wuttke; Seckmeyer, G.; König-Langlo, G.

    2006-01-01

    Spectral albedo in high resolution, from 290 to 1050 nm, has been measured at Neumayer, Antarctica, (70°39' S, 8°15' W) during the austral summer 2003/2004. At 500 nm, the spectral albedo nearly reaches unity, with slightly lower values below and above 500 nm. Above 600 nm, the spectral albedo decreases to values between 0.45 and 0.75 at 1000 nm. For one cloudless case an albedo up to 1.01 at 500 nm could be determined. This can be explained by the larger directional...

  12. Spectral Analysis

    Cecconi, Jaures

    2011-01-01

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

  13. Spectral stratigraphy

    Lang, Harold R.

    1991-01-01

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

  14. Precise acquisition and unsupervised segmentation of multi-spectral images

    Gomez, David Delgado; Clemmensen, Line Katrine Harder; Ersbøll, Bjarne Kjær;

    2007-01-01

    In this work, an integrated imaging system to obtain accurate and reproducible multi-spectral images and a novel multi-spectral image segmentation algorithm are proposed. The system collects up to 20 different spectral bands within a range that vary from 395 nm to 970 nm. The system is designed t...... conducted to show the ability of the system to acquire highly precise, reproducible and standardized multi-spectral images and to show its applicabilities in different situations....

  15. Spectral Ranking

    Vigna, Sebastiano

    2009-01-01

    This note tries to attempt a sketch of the history of spectral ranking, a general umbrella name for techniques that apply the theory of linear maps (in particular, eigenvalues and eigenvectors) to matrices that do not represent geometric transformations, but rather some kind of relationship between entities. Albeit recently made famous by the ample press coverage of Google's PageRank algorithm, spectral ranking was devised more than fifty years ago, almost exactly in the same terms, and has been studied in psychology and social sciences. I will try to describe it in precise and modern mathematical terms, highlighting along the way the contributions given by previous scholars.

  16. Spectral Tagging

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

  17. Global four-band spectral classification of Jupiter's clouds

    Voyager 2 digital images of Jupiter have been used to construct a global data base of cloud reflectance (normal albedo) in four spectral bands: three wideband colors with effective wavelengths at 431 nm (VI), 564 nm (GR), and 599 nm (OR), plus the narrowband CH4 filter centered at 621 nm

  18. The Missing Solar Irradiance Spectrum: 1 to 7 nm

    Sojka, J. J.; Lewis, M.; David, M.; Schunk, R. W.; Woods, T. N.; Eparvier, F. G.; Warren, H. P.

    2015-12-01

    During large X-class flares the Earth's upper atmospheric E-region responds immediately to solar photons in the 1 to 7 nm range. The response can change the E-region density by factors approaching 10, create large changes in conductivity, and plague HF communications. GOES-XRS provide 0.1 to 0.8 nm and a 0.05 to 0.4 nm integral channels; SOHO-SEM provided a 0 to 50 nm irradiance; TIMED and SORCE-XPS diode measurements also integrated down to 0.1 nm; and most recently SDO-EVE provided a 0.1 to 7 nm irradiance. For atmospheric response to solar flares the cadence is also crucial. Both GOES and SDO provided integral measurements at 10 seconds or better. Unfortunately these measurements have failed to capture the 1 to 7 nm spectral changes that occur during flares. It is these spectral changes that create the major impact since the ionization cross-section of the dominant atmospheric species, N2 and O2, both contain step function changes in the cross-sections. Models of the solar irradiance over this critical wavelength regime have suffered from the need to model the spectral variability based on incomplete measurements. The most sophisticated empirical model FISM [Chamberlin et al., 2008] used 1 nm spectral binning and various implementations of the above integral measurements to describe the 1 to 7 nm irradiance. Since excellent solar observations exist at other wavelengths it is possible to construct an empirical model of the solar atmosphere and then use this model to infer the spectral distribution at wavelengths below 5 nm. This differential emission measure approach has been used successfully in other contexts [e.g., Warren, 2005, Chamberlin et al., 2009]. This paper contrasts the broadband versus spectrally resolved descriptions of the incoming irradiance that affects the upper atmospheric E-layer. The results provide a prescription of what wavelength resolution would be needed to adequately measure the incoming solar irradiance in the 1 to 7 nm range.

  19. Picosecond laser texturization of mc-silicon for photovoltaics: A comparison between 1064 nm, 532 nm and 355 nm radiation wavelengths

    Binetti, Simona; Le Donne, Alessia; Rolfi, Andrea; Jäggi, Beat; Neuenschwander, Beat; Busto, Chiara; Frigeri, Cesare; Scorticati, Davide; Longoni, Luca; Pellegrino, Sergio

    2016-05-01

    Self-organized surface structures were produced by picosecond laser pulses on multi-crystalline silicon for photovoltaic applications. Three different laser wavelengths were employed (i.e. 1064 nm, 532 nm and 355 nm) and the resulting morphologies were observed to effectively reduce the reflectivity of the samples after laser irradiation. Besides, a comparative study of the laser induced subsurface damage generated by the three different wavelengths was performed by confocal micro-Raman, photoluminescence and transmission electron microscopy. The results of both the structural and optical characterization showed that the mc-Si texturing performed with the laser at 355 nm provides surface reflectivity between 11% and 8% over the spectral range from 400 nm to 1 μm, while inducing the lowest subsurface damage, located above the depletion region of the p-n junction.

  20. Spectral Image Analysis for Measuring Ripeness of Tomatoes

    Polder, G.; Heijden, van der G.W.A.M.; Young, I.T.

    2002-01-01

    In this study, spectral images of five ripeness stages of tomatoes have been recorded and analyzed. The electromagnetic spectrum between 396 and 736 nm was recorded in 257 bands (every 1.3 nm). Results show that spectral images offer more discriminating power than standard RGB images for measuring r

  1. A database for spectral image quality

    Le Moan, Steven; George, Sony; Pedersen, Marius; Blahová, Jana; Hardeberg, Jon Yngve

    2015-01-01

    We introduce a new image database dedicated to multi-/hyperspectral image quality assessment. A total of nine scenes representing pseudo-at surfaces of different materials (textile, wood, skin. . . ) were captured by means of a 160 band hyperspectral system with a spectral range between 410 and 1000nm. Five spectral distortions were designed, applied to the spectral images and subsequently compared in a psychometric experiment, in order to provide a basis for applications such as the evaluation of spectral image difference measures. The database can be downloaded freely from http://www.colourlab.no/cid.

  2. Design and implementation of a sub-nm resolution microspectrometer based on a Linear-Variable Optical Filter

    Emadi, A.; Wu, H; De Graaf, G.; Wolffenbuttel, R.F.

    2011-01-01

    In this paper the concept of a microspectrometer based on a Linear Variable Optical Filter (LVOF) for operation in the visible spectrum is presented and used in two different designs: the first is for the narrow spectral band between 610 nm and 680 nm, whereas the other is for the wider spectral band between 570 nm and 740 nm. Design considerations, fabrication and measurement results of the LVOF are presented. An iterative signal processing algorithm based on an initial calibration has been ...

  3. Solar Spectral Irradiance Changes During Cycle 24

    Marchenko, Sergey; Deland, Matthew

    2014-01-01

    We use solar spectra obtained by the Ozone Monitoring Instrument (OMI) on board the Aura satellite to detect and follow long-term (years) and short-term (weeks) changes in the solar spectral irradiance (SSI) in the 265-500 nm spectral range. During solar Cycle 24, in the relatively line-free regions the SSI changed by approximately 0.6% +/- 0.2% around 265 nm. These changes gradually diminish to 0.15% +/- 0.20% at 500 nm. All strong spectral lines and blends, with the notable exception of the upper Balmer lines, vary in unison with the solar "continuum." Besides the lines with strong chromospheric components, the most involved species include Fe I blends and all prominent CH, NH, and CN spectral bands. Following the general trend seen in the solar "continuum," the variability of spectral lines also decreases toward longer wavelengths. The long-term solar cycle SSI changes are closely, to within the quoted 0.1%-0.2% uncertainties, matched by the appropriately adjusted short-term SSI variations derived from the 27 day rotational modulation cycles. This further strengthens and broadens the prevailing notion about the general scalability of the UV SSI variability to the emissivity changes in the Mg II 280 nm doublet on timescales from weeks to years. We also detect subtle deviations from this general rule: the prominent spectral lines and blends at lambda approximately or greater than 350 nm show slightly more pronounced 27 day SSI changes when compared to the long-term (years) trends. We merge the solar data from Cycle 21 with the current Cycle 24 OMI and GOME-2 observations and provide normalized SSI variations for the 170-795 nm spectral region.

  4. 193nm Superlens imaging structure for 20nm lithography node.

    Shi, Zhong; Kochergin, Vladimir; Wang, Fei

    2009-07-01

    We are showing that a 20nm lithography resolution is theoretically feasible at a 193nm illumination wavelength if employing aluminum (Al) superlens structure with index matching layer. It is illustrated that transmissivity of evanescent waves for certain wavevector bands can be enhanced by an index matching layer. It is further shown a minimal resolution of approximately lambda/10 can be achieved by appropriately engineering mask material and superlens structure. A depth of focus of several nanometers is predicted to be possible for a periodic structure with 20nm half pitch. Assistant features were adopted in superlens structure to successfully suppress the side lobes and resolve a 20nm two-slit structure. PMID:19582044

  5. High power linearly polarized Raman fiber laser at 1120 nm

    Jianhua Wang; Lei Zhang; Jun Zhou; Lei Si; Jinbao Chen; Yan Feng

    2012-01-01

    An all-fiber linearly polarized Raman fiber laser at 1 120 nm is demonstrated.With a 1 070-nm linearly polarized Yb-doped fiber laser as pump source,an output of up to 7.7 W at 1 120 nm is obtained with an optical efficiency of 55%.The polarization extinction ratio of the linearly polarized Raman fiber is higher than 18 dB.A numerical simulation model is developed to determine the Raman coefficient of the gain fiber and to evaluate the laser performance.The spectral isolation between the Raman fiber laser and the pump fiber laser is determined to be necessary for further improvements of performance.%An all-fiber linearly polarized Raman fiber laser at 1120 nm is demonstrated. With a 1070-nm linearly polarized Yb-doped fiber laser as pump source, an output of up to 7.7 W at 1120 nm is obtained with an optical efficiency of 55%. The polarization extinction ratio of the linearly polarized Raman fiber is higher than 18 dB. A numerical simulation model is developed to determine the Raman coefficient of the gain fiber and to evaluate the laser performance. The spectral isolation between the Raman fiber laser and the pump fiber laser is determined to be necessary for further improvements of performance.

  6. 308-nm excimer laser in endodontics

    Liesenhoff, Tim

    1992-06-01

    Root canal preparation was performed on 20 extracted human teeth. After opening the coronal pulp, the root canals were prepared by 308 nm excimer laser only. All root canals were investigated under SEM after separation in the axial direction. By sagittal separation of the mandibles of freshly slaughtered cows, it was possible to get access to the tissues and irradiate under optical control. Under irradiation of excimer laser light, tissue starts to fluoresce. It was possible to demonstrate that each tissue (dentin, enamel, bone, pulpal, and connective tissue) has a characteristic spectral pattern. The SEM analyses showed that it is well possible to prepare root canals safely. All organic soft tissue has been removed by excimer laser irradiation. There was no case of via falsa. The simultaneous spectroscopic identification of the irradiated tissue provides a safe protection from overinstrumentation. First clinical trials on 20 patients suffering of chronical apical parodontitis have been carried out successfully.

  7. Characterization of LANDSAT Panels Using the NIST BRDF Scale from 1100 nm to 2500 nm

    Markham, Brian; Tsai, Benjamin K.; Allen, David W.; Cooksey, Catherine; Yoon, Howard; Hanssen, Leonard; Zeng, Jinan; Fulton, Linda; Biggar, Stuart; Markham, Brian

    2010-01-01

    Many earth observing sensors depend on white diffuse reflectance standards to derive scales of radiance traceable to the St Despite the large number of Earth observing sensors that operate in the reflective solar region of the spectrum, there has been no direct method to provide NIST traceable BRDF measurements out to 2500 rim. Recent developments in detector technology have allowed the NIST reflectance measurement facility to expand the operating range to cover the 250 nm to 2500 nm range. The facility has been modified with and additional detector using a cooled extended range indium gallium arsenide (Extended InGaAs) detector. Measurements were made for two PTFE white diffuse reflectance standards over the 1100 nm to 2500 nm region at a 0' incident and 45' observation angle. These two panels will be used to support the OLI calibration activities. An independent means of verification was established using a NIST radiance transfer facility based on spectral irradiance, radiance standards and a diffuse reflectance plaque. An analysis on the results and associated uncertainties will be discussed.

  8. Spectrally resolved white light interferometry to measure material dispersion over a wide spectral band in a single acquisition.

    Arosa, Yago; Lago, Elena López; Varela, Luis Miguel; de la Fuente, Raúl

    2016-07-25

    In this paper we apply spectrally resolved white light interferometry to measure refractive and group index over a wide spectral band from 400 to 1000 nm. The output of a Michelson interferometer is spectrally decomposed by a homemade prism spectrometer with a high resolution camera. The group index is determined directly from the phase extracted from the spectral interferogram while the refractive index is estimated once its value at a given wavelength is known. PMID:27464179

  9. Spectral dimensions from the spectral action

    2014-01-01

    The generalised spectral dimension $D_{ S}(T)$ provides a powerful tool for comparing different approaches to quantum gravity. In this work, we apply this formalism to the classical spectral actions obtained within the framework of almost-commutative geometry. Analysing the propagation of spin-0, spin-1 and spin-2 fields, we show that a non-trivial spectral dimension arises already at the classical level. The effective field theory interpretation of the spectral action yields plateau-structur...

  10. Spectral Imaging by Upconversion

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

    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....

  11. Spectral Decomposition Algorithm (SDA)

    National Aeronautics and Space Administration — Spectral Decomposition Algorithm (SDA) is an unsupervised feature extraction technique similar to PCA that was developed to better distinguish spectral features in...

  12. Characteristics of THz Emission from GaAs Crystal Excited by 400 nm and 800 nm Optical Pulses

    YANG Yu-Ping; XU Xin-Long; YAN Wei; WANG Li

    2005-01-01

    @@ THz emission spectroscopy is used to study the generation mechanism dependent behaviour of terahertz (THz) electromagnetic waves from the GaAs crystal under excitation by 400 nm and 800 nm femtosecond (fs) pulses,respectively. The wavelength dependence of the emission spectrum under two types of THz generation mechanisms is analysed. Under the optical rectification mechanism, a slight enhancement of the spectral amplitude in the high-frequency regime is observed in a GaAs(110) crystal by the excitation of a 400-nm optical pulse compared with that of 800nm. Whereas an obvious red shift of the amplitude spectrum occurs in the GaAs(100) sample under the transient photoconduction mechanism. These phenomena are explained in detail by the duration of the optical pump pulse and the band structure of GaAs, respectively.

  13. Spectral variations of UV-A and PAR solar radiation in estuarine waters of Goa

    Talaulikar, M.; Suresh, T.; Silveira, N.; Desa, E.; Matondkar, S.G.P.; Lotlikar, A.

    The spectral solar radiation measurements in the range 350-800 nm were carried out in the estuarine waters of Goa using hyperspectral radiometer. The results of the analysis of solar light in the spectral range of photosynthetically available...

  14. Study of the emission spectra of a 1320-nm semiconductor disk laser and its second harmonic

    Gochelashvili, K. S.; Derzhavin, S. I.; Evdokimova, O. N.; Zolotovskii, I. O.; Podmazov, S. V.

    2016-03-01

    The spectral characteristics of an optically pumped external-cavity semiconductor disk laser near λ = 1320 nm are studied experimentally. Intracavity second harmonic generation is obtained using an LBO nonlinear crystal. The output power at a wavelength of 660 nm in the cw regime was 620 mW, and the peak power in the pulsed regime was 795 mW.

  15. Photoionization of Nitromethane at 355nm and 266nm

    Martínez, Denhi; Betancourt, Francisco; Poveda, Juan Carlos; Guerrero, Alfonso; Cisneros, Carmen; Álvarez, Ignacio

    2014-05-01

    Nitromethane is one of the high-yield clean liquid fuels, i.e., thanks to the oxygen contained in nitromethane, much less atmospheric oxygen is burned compared to hydrocarbons such as gasoline, making the nitromethane an important prototypical energetic material, the understanding of its chemistry is relevant in other fields such as atmospheric chemistry or biochemistry. In this work we present the study of photoionization dynamics by multiphoton absorption with 355 nm and 266 nm wavelength photons, using time of flight spectrometry in reflectron mode (R-TOF). Some of the observed ion products appear for both wavelength and other only in one of them; both results were compared with preview observations and new ions were detected. This work is supported by CONACYT grant 165410 and DGAPA-UNAM grants IN-107-912 and IN-102-613.

  16. Analysis of Cervical Supernatant Samples Luminescence Using 355 nm Laser

    Vaitkuviene, A.; Gegzna, V.; Kurtinaitiene, R.; Stanikunas, R.; Rimiene, J.; Vaitkus, J.

    2010-05-01

    The biomarker discovery for accurate detection and diagnosis of cervical carcinoma and its malignant precursors represents one of the current challenges in clinical medicine. Laser induced autofluorescence spectra in cervical smear content were fitted to predict the cervical epithelium diagnosis as a lab off "optical biopsy" method. Liquid PAP supernatant sediment dried on Quartz plate spectroscopy was performed by 355 nm Nd YAG microlaser STA-1 (Standa, Ltd). For comparison a liquid supernatant spectroscopy was formed by laboratory "Perkin Elmer LS 50B spetrometer at 290, 300, 310 nm excitations. Analysis of spectrum was performed by approximation using the multi-peaks program with Lorentz functions for the liquid samples and with Gaussian functions for the dry samples. Ratio of spectral components area to the area under whole experimental curve (SPP) was calculated. The spectral components were compared by averages of SPP using Mann-Whitney U-test in histology groups. Results. Differentiation of Normal and HSIL/CIN2+ cases in whole supernatant could be performed by stationary laboratory lamp spectroscopy at excitation 290 nm and emission >379 nm with accuracy AUC 0,69, Sens 0,72, Spec 0,65. Differentiation Normal versus HSIL/CIN2+ groups in dried enriched supernatant could be performed by 355 nm microlaser excitation at emission 405-424 nm with accuracy (AUC 0,96, Sens 0,91, Spec 1.00). Diagnostic algorithm could be created for all histology groups differentiation under 355 nm excitation. Microlaser induced "optical biopsy "looks promising method for cervical screening at the point of care.

  17. High-resolution optical signatures of fresh and aged explosives in the 420nm to 620nm illumination range

    Lunsford, Robert; Grun, Jacob; Gump, Jared

    2012-06-01

    Optical signatures of fresh and aged explosives are measured and compared to determine whether there exist differences in the signatures that can be exploited for detection. The explosives examined are RDX, TNT, and HMX, which have been heated for two weeks at 75 degrees centigrade or irradiated for two weeks with a 15-Watt ultraviolet lamp (254nm). The optical signatures are obtained by illuminating the samples with a sequence of laser wavelengths between 420nm and 620nm in 10 nm steps and measuring the spectra of light scattered from the sample at each laser wavelength. The measurements are performed on the Naval Research Laboratory's SWOrRD instrument. SWOrRD is capable of illuminating a sample with laser wavelength between 210nm and 2000nm, in steps of 0.1nm, and measuring the spectrum of light scattered from the sample at each wavelength. SWOrRD's broad tuning range, high average power (1- 300mW), narrow line width (< 4cm-1), and rapid wavelength tunability enable these measurements. Results, based on more than 80 measurements - each at 21 sequential laser wavelengths, indicate that the variation in spectral line amplitude observed when altering laser illumination wavelength differs between fresh and aged explosives. Thus, an instrument for rapid and reagent-less differentiation between aged and fresh explosives, based on illumination with a few appropriately chosen laser wavelengths appears feasible.

  18. 65 nm CMOS Sensors Applied to Mathematically Exact Colorimetric Reconstruction

    Mayr, C; Krause, A; Schlüßler, J -U; Schüffny, R

    2014-01-01

    Extracting colorimetric image information from the spectral characteristics of image sensors is a key issue in accurate image acquisition. Technically feasible filter/sensor combinations usually do not replicate colorimetric responses with sufficient accuracy to be directly applicable to color representation. A variety of transformations have been proposed in the literature to compensate for this. However, most of those rely on heuristics and/or introduce a reconstruction dependent on the composition of the incoming illumination. In this work, we present a spectral reconstruction method that is independent of illumination and is derived in a mathematically strict way. It provides a deterministic method to arrive at a least mean squared error approximation of a target spectral characteristic from arbitrary sensor response curves. Further, we present a new CMOS sensor design in a standard digital 65nm CMOS technology. Novel circuit techniques are used to achieve performance comparable with much larger-sized spe...

  19. Successive Spectral Sequences

    Matschke, Benjamin

    2013-01-01

    If a chain complex is filtered over a poset I, then for every chain in I we obtain a spectral sequence. In this paper we define a spectral system that contains all these spectral sequences and relates their pages via differentials, extensions, and natural isomorphisms. We also study an analog of exact couples that provides a more general construction method for these spectral systems. This turns out to be a good framework for unifying several spectral sequences that one would usually apply on...

  20. On golden spectral graphs

    Estrada Roger, Ernesto; Gago Álvarez, Silvia

    2009-01-01

    The concept of golden spectral graphs is introduced and some of their general properties reported. Golden spectral graphs are those having a golden proportion for the spectral ratios defined on the basis of the spectral gap, spectral spread and the difference between the second largest and the smallest eigenvalue of the adjacency matrix. They are good expanders and display excellent synchronizability. Here we report some new construction methods as well as several of their topological pa...

  1. On the Spectral Singularities and Spectrality of the Hill Operator

    O. A. Veliev

    2014-01-01

    First we study the spectral singularity at infinity and investigate the connections of the spectral singularities and the spectrality of the Hill operator. Then we consider the spectral expansion when there is not the spectral singularity at infinity.

  2. Spectral and kinetic analysis of thermoluminescence from manganiferous carbonatite

    Chithambo, M.L., E-mail: m.chithambo@ru.ac.za [Department of Physics and Electronics, Rhodes University, PO BOX 94, Grahamstown 6140 (South Africa); Pagonis, V. [Physics Department, McDaniel College, Westminster, MD 21158 (United States); Ogundare, F.O. [Department of Physics, University of Ibadan, Ibadan (Nigeria)

    2014-01-15

    Thermoluminescence spectra of manganiferous carbonatite has been studied from 30 °C to 400 °C over the wavelength range from 200 nm to 800 nm. The natural thermoluminescence appears above 200 °C and shows continuous spectral distribution from 240 nm to 800 nm. Above 500 nm the emission appears in the form of line structure emission. These are reproduced by laboratory irradiation which also produces broad bands near 100 °C. The emission features are attributed to presence of Mn{sup 2+} impurities in the carbonatite matrix. The spectral study was supplemented by kinetic analysis of the most prominent peaks and their kinetic features are reported. -- Highlights: • Thermoluminescence spectra of manganiferous carbonatite over 200 nm to 800 nm is reported. • A detailed kinetic analysis of associated electron traps has been carried out. • The emission is linked to Mn{sup 2+} impurities and transitions involved are proposed.

  3. Spectral and kinetic analysis of thermoluminescence from manganiferous carbonatite

    Thermoluminescence spectra of manganiferous carbonatite has been studied from 30 °C to 400 °C over the wavelength range from 200 nm to 800 nm. The natural thermoluminescence appears above 200 °C and shows continuous spectral distribution from 240 nm to 800 nm. Above 500 nm the emission appears in the form of line structure emission. These are reproduced by laboratory irradiation which also produces broad bands near 100 °C. The emission features are attributed to presence of Mn2+ impurities in the carbonatite matrix. The spectral study was supplemented by kinetic analysis of the most prominent peaks and their kinetic features are reported. -- Highlights: • Thermoluminescence spectra of manganiferous carbonatite over 200 nm to 800 nm is reported. • A detailed kinetic analysis of associated electron traps has been carried out. • The emission is linked to Mn2+ impurities and transitions involved are proposed

  4. Analysis of multi-mode to single-mode conversion at 635 nm and 1550 nm

    Zamora, Vanessa; Bogatzki, Angelina; Arndt-Staufenbiel, Norbert; Hofmann, Jens; Schröder, Henning

    2016-03-01

    We propose two low-cost and robust optical fiber systems based on the photonic lantern (PL) technology for operating at 635 nm and 1550 nm. The PL is an emerging technology that couples light from a multi-mode (MM) fiber to several single-mode (SM) fibers via a low-loss adiabatic transition. This bundle of SM fibers is observed as a MM fiber system whose spatial modes are the degenerate supermodes of the bundle. The adiabatic transition allows that those supermodes evolve into the modes of the MM fiber. Simulations of the MM fiber end structure and its taper transition have been performed via functional mode solver tools in order to understand the modal evolution in PLs. The modelled design consists of 7 SM fibers inserted into a low-index capillary. The material and geometry of the PLs are chosen such that the supermodes match to the spatial modes of the desired step-index MM fiber in a moderate loss transmission. The dispersion of materials is also considered. These parameters are studied in two PL systems in order to reach a spectral transmission from 450 nm to 1600 nm. Additionally, an analysis of the geometry and losses due to the mismatching of modes is presented. PLs are typically used in the fields of astrophotonics and space photonics. Recently, they are demonstrated as mode converters in telecommunications, especially focusing on spatial division multiplexing. In this study, we show the use of PLs as a promising interconnecting tool for the development of miniaturized spectrometers operating in a broad wavelength range.

  5. The Spectral Shift Function and Spectral Flow

    Azamov, N. A.; Carey, A. L.; Sukochev, F. A.

    2007-11-01

    At the 1974 International Congress, I. M. Singer proposed that eta invariants and hence spectral flow should be thought of as the integral of a one form. In the intervening years this idea has lead to many interesting developments in the study of both eta invariants and spectral flow. Using ideas of [24] Singer’s proposal was brought to an advanced level in [16] where a very general formula for spectral flow as the integral of a one form was produced in the framework of noncommutative geometry. This formula can be used for computing spectral flow in a general semifinite von Neumann algebra as described and reviewed in [5]. In the present paper we take the analytic approach to spectral flow much further by giving a large family of formulae for spectral flow between a pair of unbounded self-adjoint operators D and D + V with D having compact resolvent belonging to a general semifinite von Neumann algebra {mathcal{N}} and the perturbation V in {mathcal{N}} . In noncommutative geometry terms we remove summability hypotheses. This level of generality is made possible by introducing a new idea from [3]. There it was observed that M. G. Krein’s spectral shift function (in certain restricted cases with V trace class) computes spectral flow. The present paper extends Krein’s theory to the setting of semifinite spectral triples where D has compact resolvent belonging to {mathcal{N}} and V is any bounded self-adjoint operator in {mathcal{N}} . We give a definition of the spectral shift function under these hypotheses and show that it computes spectral flow. This is made possible by the understanding discovered in the present paper of the interplay between spectral shift function theory and the analytic theory of spectral flow. It is this interplay that enables us to take Singer’s idea much further to create a large class of one forms whose integrals calculate spectral flow. These advances depend critically on a new approach to the calculus of functions of non

  6. Spectral reflectance relationships to leaf water stress

    Ripple, William J.

    1986-01-01

    Spectral reflectance data were collected from detached snapbean leaves in the laboratory with a multiband radiometer. Four experiments were designed to study the spectral response resulting from changes in leaf cover, relative water content of leaves, and leaf water potential. Spectral regions included in the analysis were red (630-690 nm), NIR (760-900 nm), and mid-IR (2.08-2.35 microns). The red and mid-IR bands showed sensitivity to changes in both leaf cover and relative water content of leaves. The NIR was only highly sensitive to changes in leaf cover. Results provided evidence that mid-IR reflectance was governed primarily by leaf moisture content, although soil reflectance was an important factor when leaf cover was less than 100 percent. High correlations between leaf water potentials and reflectance were attributed to covariances with relative water content of leaves and leaf cover.

  7. 65-nm Cyclone Ⅲ FPGA

    2008-01-01

    Altera公司低功耗、低成本Cyclone Ⅲ系列65nm FPGA所有8个型号的产品级芯片实现量产,Cyclone Ⅲ系列产品已迅速应用于无线、军事、显示、汽车和工业市场的大量客户系统中。

  8. Spectral luminescence analysis of amniotic fluid

    Slobozhanina, Ekaterina I.; Kozlova, Nataly M.; Kasko, Leonid P.; Mamontova, Marina V.; Chernitsky, Eugene A.

    1997-12-01

    It is shown that the amniotic fluid has intensive ultra-violet luminescence caused by proteins. Along with it amniotic fluid radiated in the field of 380 - 650 nm with maxima at 430 - 450 nm and 520 - 560 nm. The first peak of luminescence ((lambda) exc equals 350 nm; (lambda) em equals 430 - 440 nm) is caused (most probably) by the presence in amniotic fluid of some hormones, NADH2 and NADPH2. A more long-wave component ((lambda) exc equals 460 nm; (lambda) em equals 520 - 560 nm) is most likely connected with the presence in amniotic fluid pigments (bilirubin connected with protein and other). It is shown that intensity and maximum of ultra-violet luminescence spectra of amniotic fluid in normality and at pathology are identical. However both emission spectra and excitation spectra of long-wave ((lambda) greater than 450 nm) luminescence of amniotic fluid from pregnant women with such prenatal abnormal developments of a fetus as anencephaly and spina bifida are too long-wave region in comparison with the norm. Results of research testify that spectral luminescent analysis of amniotic fluid can be used for screening of malformations of the neural tube. It is very difficult for a practical obstetrician to reveal pregnant women with a high risk of congenital malformations of the fetus. Apart from ultrasonic examination, cytogenetic examination of amniotic fluid and defumination of concentrations of alpha-fetoprotein and acetylcholin-esterases in the amniotic fluid and blood plasma are the most widely used diagnostic approaches. However, biochemical and cytogenetic diagnostic methods are time-consuming. In the present work spectral luminescence properties of the amniotic fluid are investigated to determine spectral parameters that can be used to reveal pregnant women with a high risk of congenital malformations of their offsprings.

  9. 200 nm-1000 nm spectra of light emitted in the impact of 40Ar10+ upon Al and Si solid surfaces

    张小安; 赵永涛; 李福利; 杨治虎; 肖国青; 詹文龙

    2003-01-01

    This paper reports the measured results of the 200 nm-1000 nm characteristic spectral lines of Al, Si and Ar atoms when highly charged ions 40Ar10+ are incident upon Al and P-type Si surfaces. The ion 40Ar10+ is provided by the ECR ion source of the National Laboratory of the Heavy Ion Accelerator in Lanzhou. The results show that when the low-speed ions in the highly charged state interact with the solid surfaces, the characteristic spectral lines of the target atoms and ions spurted from the surfaces can be effectively excited. Moreover, because of the competition of the non-radiation de-excitation of the hollow atom by emitting secondary electrons with the de-excitation process by radiating photons, the spectral intensity of the characteristic spectral lines of Ar atoms on the P-type Si surface is, as a whole, greater than that of Ar atoms on the Al surface.

  10. Multi-spectral confocal microendoscope for in-vivo imaging

    Rouse, Andrew Robert

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

  11. Spectral signatures of penumbral transients

    Reardon, K. [INAF-Osservatorio Astrofisico di Arcetri, I-50125 Firenze (Italy); Tritschler, A. [National Solar Observatory/Sacramento Peak, P.O. Box 62, Sunspot, NM 88349 (United States); Katsukawa, Y. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2013-12-20

    In this work we investigate the properties of penumbral transients observed in the upper photospheric and chromospheric region above a sunspot penumbra using two-dimensional spectroscopic observations of the Ca II 854.21 nm line with a 5 s cadence. In our 30 minutes of observations, we identify several penumbral-micro jets (PMJs) with cotemporal observations from Dunn Solar Telescope/IBIS and Hinode/SOT. We find that the line profiles of these PMJ events show emission in the two wings of the line (±0.05 nm), but little modification of the line core. These are reminiscent of the line profiles of Ellerman bombs observed in plage and network regions. Furthermore, we find evidence that some PMJ events have a precursor phase starting 1 minute prior to the main brightening that might indicate initial heating of the plasma prior to an acoustic or bow shock event. With the IBIS data, we also find several other types of transient brightenings with timescales of less than 1 minute that are not clearly seen in the Hinode/SOT data. The spectral profiles and other characteristics of these events are significantly different from those of PMJs. The different appearances of all these transients are an indicator of the general complexity of the chromospheric magnetic field and underscore the highly dynamic behavior above sunspots. It also highlights the care that is needed in interpreting broadband filter images of chromospheric lines, which may conceal very different spectral profiles, and the underlying physical mechanisms at work.

  12. Wavelength stabilizer based on dual fiber Bragg gratings for 980nm Mini-uncooled pump laser

    Hu, Shuangshuang; Li, Yi; Jiang, Qunjie; Wu, Bin; Yu, Xiaojing; Wang, Haifang

    2008-12-01

    High power 980nm pump lasers are the key components in optical fiber amplifier. Wavelength stability for 980nm Miniuncooled pump laser is required to maintain the amplifier's efficiency throughout its lifetime. In this paper, a new type of wavelength stabilizer for uncooled pump laser which utilizes two fiber Bragg gratings (FBGs) matched in wavelength, bandwidth, and reflectivity is presented. The characteristics of transmissivity and reflectivity for the dual FBGs stabilized 980nm pump laser are theoretically modeled and experimentally studied. The results show that the output spectral characteristics of the uncooled pump laser with the dual FBGs have been greatly improved. The laser module can work steadily over a wide temperature range from 0°C to 70°C, with 0.2nm wavelength shift, along with more than 45dB side mode suppression ratio, and less than 1.57nm spectral bandwidth.

  13. Zeta Spectral Action

    Kurkov, Maxim A; Sakellariadou, Mairi; Watcharangkool, Apimook

    2014-01-01

    In this paper we propose a novel definition of the bosonic spectral action using zeta function regularization, in order to address the issues of renormalizability, ultraviolet completeness and spectral dimensions. We compare the zeta spectral action with the usual (cutoff based) spectral action and discuss its purely spectral origin, predictive power, stressing the importance of the issue of the three dimensionful fundamental constants, namely the cosmological constant, the Higgs vacuum expectation value, and the gravitational constant. We emphasize the fundamental role of the neutrino Majorana mass term for the structure of the bosonic action.

  14. The modification of spectral characteristics of cytostatics by optical beams

    Pascu, Mihail Lucian; Brezeanu, Mihail; Carstocea, Benone D.; Voicu, Letitia; Gazdaru, Doina M.; Smarandache, Adriana A.

    2004-10-01

    Besides the biochemical action of methotrexate (MTX) and 5-fluorouracil (FU) their effect in destroying cancer tumours could be enhanced by exposure to light at different doses. Absorption, excitation and emission spectra of 10-4M - 10-5M MTX solutions in natural saline and sodium hydroxide at pH = 8.4 were measured, while their exposure to coherent and uncoherent light in the visible and near ultraviolet (UV) spectral ranges was made (Hg lamps and Nitrogen pulsed laser radiation were used). Absorption spectra exhibit spectral bands in the range 200 nm - 450 nm. The 200 - 450 nm excitation spectra were measured with emission centered on 470 nm; MTX fluorescence excitation was measured at 390 nm and the emission was detected between 400 nm and 600 nm showing a maximum at 470 nm. Spectra modifications, nonlinearly depending on exposure time (varying from 1 min to 20 min), evidenced MTX photo-dissociation to the fluorescent compound 2,4 diamino-formylpteridine. In the 5-FU case the absorption spectra exhibit bands between 200 nm and 450 nm. The emission fluorescence spectra were measured between 400 nm and 600 nm, with λex = 350 nm for UV Hg lamp and with λex = 360 nm for laser irradiated samples; at irradiation with N2 laser emitted radiation the excitation spectra were measured in the range of 200 nm - 400 nm, with λem = 440 nm. New vascularity rapid destruction was observed for conjunctive impregnated with 5-FU solution whilst exposed to incoherent UV and visible light.

  15. On-chip visible-to-infrared supercontinuum generation with more than 495 THz spectral bandwidth

    Epping, J.P.; Hellwig, T.; Hoekman, M.; Mateman, R.; Leinse, A.; Heideman, R.G.; Rees, van A.; Slot, van der P.J.M.; Lee, C.J.; Fallnich, C.; Boller, K-J.

    2015-01-01

    We report ultra-broadband supercontinuum generation in high-confinement Si3N4 integrated optical waveguides. The spectrum extends through the visible (from 470 nm) to the infrared spectral range (2130 nm) comprising a spectral bandwidth wider than 495 THz, which is the widest supercontinuum spectrum

  16. Defects of a phosphosilicate glass exposed to the 193-nm radiation

    Induced absorption is measured in a hydrogen-unloaded phosphosilicate glass (PSG) in spectral ranges from 140 to 850 nm and from 1000 to 1700 nm before and after its exposure to the 193-nm radiation. It is shown that the induced-absorption bands in the range between 140 and 300 nm do not coincide with the bands observed earlier after exposing a PSG to X-rays. It is assumed that the photorefractive effect in the PSG is related to variations induced in the glass network rather than to defects responsible for the induced-absorption bands. (fiber and integrated optics)

  17. FIBER AND INTEGRATED OPTICS: Defects of a phosphosilicate glass exposed to the 193-nm radiation

    Larionov, Yu V.; Sokolov, V. O.; Plotnichenko, V. G.

    2007-06-01

    Induced absorption is measured in a hydrogen-unloaded phosphosilicate glass (PSG) in spectral ranges from 140 to 850 nm and from 1000 to 1700 nm before and after its exposure to the 193-nm radiation. It is shown that the induced-absorption bands in the range between 140 and 300 nm do not coincide with the bands observed earlier after exposing a PSG to X-rays. It is assumed that the photorefractive effect in the PSG is related to variations induced in the glass network rather than to defects responsible for the induced-absorption bands.

  18. Intra-cavity upconversion to 631 nm of images illuminated by an eye-safe ASE source at 1550 nm.

    Torregrosa, A J; Maestre, H; Capmany, J

    2015-11-15

    We report an image wavelength upconversion system. The system mixes an incoming image at around 1550 nm (eye-safe region) illuminated by an amplified spontaneous emission (ASE) fiber source with a Gaussian beam at 1064 nm generated in a continuous-wave diode-pumped Nd(3+):GdVO(4) laser. Mixing takes place in a periodically poled lithium niobate (PPLN) crystal placed intra-cavity. The upconverted image obtained by sum-frequency mixing falls around the 631 nm red spectral region, well within the spectral response of standard silicon focal plane array bi-dimensional sensors, commonly used in charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) video cameras, and of most image intensifiers. The use of ASE illumination benefits from a noticeable increase in the field of view (FOV) that can be upconverted with regard to using coherent laser illumination. The upconverted power allows us to capture real-time video in a standard nonintensified CCD camera. PMID:26565863

  19. Dual-wavelength diode laser with electrically adjustable wavelength distance at 785  nm.

    Sumpf, Bernd; Kabitzke, Julia; Fricke, Jörg; Ressel, Peter; Müller, André; Maiwald, Martin; Tränkle, Günther

    2016-08-15

    A spectrally adjustable monolithic dual-wavelength diode laser at 785 nm as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS) is presented. The spectral distance between the two excitation wavelengths can be electrically adjusted between 0 and 2.0 nm using implemented heater elements above the distributed Bragg reflector (DBR) gratings. Output powers up to 180 mW at a temperature of 25°C were measured. The spectral width is smaller than 13 pm, limited by the spectrum analyzer. The device is well-suited for Raman spectroscopy, and the flexible spectral distance allows a target-specific adjustment of the excitation light source for shifted excitation Raman difference spectroscopy (SERDS). PMID:27519065

  20. Adaptive Spectral Doppler Estimation

    Gran, Fredrik; Jakobsson, Andreas; Jensen, Jørgen Arendt

    2009-01-01

    In this paper, 2 adaptive spectral estimation techniques are analyzed for spectral Doppler ultrasound. The purpose is to minimize the observation window needed to estimate the spectrogram to provide a better temporal resolution and gain more flexibility when designing the data acquisition sequence....... The methods can also provide better quality of the estimated power spectral density (PSD) of the blood signal. Adaptive spectral estimation techniques are known to pro- vide good spectral resolution and contrast even when the ob- servation window is very short. The 2 adaptive techniques are tested and...... compared with the averaged periodogram (Welch’s method). The blood power spectral capon (BPC) method is based on a standard minimum variance technique adapted to account for both averaging over slow-time and depth. The blood amplitude and phase estimation technique (BAPES) is based on finding a set of...

  1. NM-Series of Representative Manufactured Nanomaterials - Zinc Oxide NM-110, NM-111, NM-112, NM-113: Characterisation and Test Item Preparation

    Singh, Charanjeet; FRIEDRICHS, Steffi; Levin, Michael; BIRKEDAL Rene; JENSEN Keld Astrup; Pojana, Giulio; Wohlleben, Wendel; Schulte, Stefan; Wiench, Karin; TURNEY T; KOULAEVA D; Marshall, Damian; Hund-Rinke, K.; KOERDEL W.; VAN DOREN E

    2011-01-01

    The European Commission Joint Research Centre (JRC) provides scientific support to European Union policy regarding nanotechnology. Over the last three years, the JRC, in collaboration with international public and private partners, focused part of its work on establishing and applying a priority list (NM-Series) of Representative Manufactured Nanomaterials (RMNs) in support of one of the most comprehensive nanomaterial research programmes that is currently being carried out: the Organisation ...

  2. Sub-180 nm generation with borate crystal

    Qu, Chen; Yoshimura, Masashi; Tsunoda, Jun; Kaneda, Yushi; Imade, Mamoru; Sasaki, Takatomo; Mori, Yusuke

    2014-10-01

    We demonstrated a new scheme for the generation of 179 nm vacuum-ultraviolet (VUV) light with an all-solid-state laser system. It was achieved by mixing the deep-ultraviolet (DUV) of 198.8 nm and the infrared (IR) of 1799.9 nm. While CsB3O5 (CBO) did not satisfy the phase-matching at around 180 nm, 179 nm output was generated with LiB3O5 (LBO) for the first time. The phase-matching property of LBO at around 180 nm was also investigated. There was small deviation from theoretical curve in the measurement, which is still considered reasonable.

  3. The other spectral flow

    Gato-Rivera, Beatriz; Gato-Rivera, Beatriz; Rosado, Jose Ignacio

    1995-01-01

    Recently we showed that the spectral flow acting on the N=2 twisted topological theories gives rise to a topological algebra automorphism. Here we point out that the untwisting of that automorphism leads to a spectral flow on the untwisted N=2 superconformal algebra which is different from the usual one. This "other" spectral flow does not interpolate between the chiral ring and the antichiral ring. In particular, it maps the chiral ring into the chiral ring and the antichiral ring into the antichiral ring. We discuss the similarities and differences between both spectral flows. We also analyze their action on null states.

  4. Photoinduced spectral changes of photoluminescent gold nanoclusters

    Matulionytė, Marija; Marcinonytė, Raminta; Rotomskis, Ričardas

    2015-05-01

    Ultrasmall photoluminescent gold nanoclusters (Au NCs), composed of several atoms with sizes up to a few nanometers, have recently stimulated extensive interest. Unique molecule-like behaviors, low toxicity, and facile synthesis make photoluminescent Au NCs a very promising alternative to organic fluorophores and semiconductor quantum dots (QDs) in broad ranges of biomedical applications. However, using gold nanoparticles (Au NPs) for bioimaging might cause their degradation under continuous excitation with UV light, which might result in toxicity. We report spectral changes of photoluminescent 2-(N-morpholino) ethanesulfonic acid (MES)-coated (Au-MES) NCs under irradiation with UV/blue light. Photoluminescent water soluble Au-MES NCs with a photoluminescence (PL) band maximum at 476 nm (λex=420 nm) were synthesized. Under irradiation with 402 nm wavelength light the size of photoluminescent Au-MES NCs decreased (λem=430 nm). Irradiating the sample solution with 330 nm wavelength light, nonluminescent Au NPs were disrupted, and photoluminescent Au NCs (λem=476 nm) were formed. Irradiation with 330 nm wavelength light did not directly affect photoluminescent Au-MES NCs, however, increase in PL intensity indicated the formation of photoluminescent Au NCs from the disrupted nonluminescent Au NPs. This study gives a good insight into the photostability of MES-coated Au NPs under continuous excitation with UV/blue light.

  5. Enhancement of 800 nm upconversion emission in a thulium doped tellurite microstructured fiber pumped by a 1560 nm femtosecond fiber laser

    Jia, Zhixu; Yao, Chuanfei; Wang, Shunbin; Zheng, Kezhi; Xiong, Liangming; Luo, Jie; Lv, Dajuan; Qin, Guanshi; Ohishi, Yasutake; Qin, Weiping

    2016-04-01

    We report enhanced upconversion (UC) fluorescence in Tm3+ doped tellurite microstructured fibers (TDTMFs) fabricated by using a rod-in-tube method. Under the pumping of a 1560 nm femtosecond fiber laser, ultrabroadband supercontinuum light expanding from ˜1050 to ˜2700 nm was generated in a 4 cm long TDTMF. Simultaneously, intense 800 nm UC emission from the 3H4 → 3H6 transition of Tm3+ was observed in the same TDTMF. Compared to that pumped by a 1560 nm continuous wave fiber laser, the UC emission intensity was enhanced by ˜4.1 times. The enhancement was due to the spectral broadening in the TDTMF under the pumping of the 1560 nm femtosecond fiber laser.

  6. Spectrally tailored supercontinuum generation from single-mode-fiber amplifiers

    Spectral filtering of an all-normal-dispersion Yb-doped fiber laser was demonstrated effective for broadband supercontinuum generation in the picosecond time region. The picosecond pump pulses were tailored in spectrum with 1 nm band-pass filter installed between two single-mode fiber amplifiers. By tuning the spectral filter around 1028 nm, four-wave mixing was initiated in a photonic crystal fiber spliced with single-mode fiber, as manifested by the simultaneous generation of Stokes wave at 1076 nm and anti-Stokes wave at 984 nm. Four-wave mixing took place in cascade with the influence of stimulated Raman scattering and eventually extended the output spectrum more than 900 nm of 10 dB bandwidth. This technique allows smooth octave supercontinuum generation by using simple single-mode fiber amplifiers rather than complicated multistage large-mode-area fiber amplifiers.

  7. Spectrally tailored supercontinuum generation from single-mode-fiber amplifiers

    Hao, Qiang; Guo, Zhengru; Zhang, Qingshan [Shanghai Key Laboratory of Modern Optical System, Engineering Research Center of Optical Instrument and System (Ministry of Education), School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200093 (China); Liu, Yang; Li, Wenxue [State Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 Zhongshan North Road, Shanghai 200062 (China); Zeng, Heping, E-mail: hpzeng@phy.ecnu.edu.cn [Shanghai Key Laboratory of Modern Optical System, Engineering Research Center of Optical Instrument and System (Ministry of Education), School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200093 (China); State Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 Zhongshan North Road, Shanghai 200062 (China)

    2014-05-19

    Spectral filtering of an all-normal-dispersion Yb-doped fiber laser was demonstrated effective for broadband supercontinuum generation in the picosecond time region. The picosecond pump pulses were tailored in spectrum with 1 nm band-pass filter installed between two single-mode fiber amplifiers. By tuning the spectral filter around 1028 nm, four-wave mixing was initiated in a photonic crystal fiber spliced with single-mode fiber, as manifested by the simultaneous generation of Stokes wave at 1076 nm and anti-Stokes wave at 984 nm. Four-wave mixing took place in cascade with the influence of stimulated Raman scattering and eventually extended the output spectrum more than 900 nm of 10 dB bandwidth. This technique allows smooth octave supercontinuum generation by using simple single-mode fiber amplifiers rather than complicated multistage large-mode-area fiber amplifiers.

  8. Set Up For Filter And Mirror Efficiencies Measurements In The UV and VUV Spectral Range

    Pouey, M.; Malherbe, A.

    1986-10-01

    A vacuum reflectometer for the UV and VUV spectral range was developed for qualification of optical components below 400 nm. Typical performances, in the 120-320 nm spectral range, of filters and mirrors offered by MATRA will be presented. Fitted with various gratings and sources this device allows reflecting, transmitting power as well as scattered or diffracted flux measurements (gratings efficiency measurements) until 25 nm.

  9. [Plant Spectral Discrimination Based on Phenological Features].

    Zhang, Lei; Zhao, Jian-long; Jia, Kun; Li, Xiao-song

    2015-10-01

    Spectral analysis plays a significant role onplant characteristic identification and mechanism recognition, there were many papers published on the aspects of absorption features in the spectra of chlorophyll and moisture, spectral analysis onvegetation red edge effect, spectra profile feature extraction, spectra profile conversion, vegetation leaf structure and chemical composition impacts on the spectra in past years. However, fewer researches issued on spectral changes caused by plant seasonal changes of life form, chlorophyll, leaf area index. This paper studied on spectral observation of 11 plants of various life form, plant leaf structure and its size, phenological characteristics, they include deciduous forest with broad vertical leaf, needle leaf evergreen forest, needle leaf deciduous forest, deciduous forest with broadflat leaf, high shrub with big leaf, high shrub with little leaf, deciduous forest with broad little leaf, short shrub, meadow, steppe and grass. Field spectral data were observed with SVC-HR768 (Spectra Vista company, USA), the band width covers 350-2 500 nm, spectral resolution reaches 1-4 nm. The features of NDVI, spectral maximum absorption depth in green band, and spectral maximum absorption depth in red band were measured after continuum removal processing, the mean, amplitude and gradient of these features on seasonal change profile were analyzed, meanwhile, separability research on plant spectral feature of growth period and maturation period were compared. The paper presents a calculation method of separability of vegetation spectra which consider feature spatial distances. This index is carried on analysis of the vegetation discrimination. The results show that: the spectral features during plant growth period are easier to distinguish than them during maturation period. With the same features comparison, plant separability of growth period is 3 points higher than it during maturation period. The overall separabilityof vegetation

  10. Spectral studies of ocean water using DOAS

    M. Vountas; Dinter, T.; Bracher, A.; Burrows, J.P.; Sierk, B.

    2007-01-01

    International audience Methods enabling the retrieval of oceanic parameter from the space borne instrumentation Scanning Imaging Absorption Spectrometer for Atmospheric ChartographY (SCIAMACHY) using Differential Optical Absorption Spectroscopy (DOAS) are presented. SCIAMACHY onboard ENVISAT measures back scattered solar radiation at a spectral resolution (0.2 to 1.5 nm). The DOAS method was used for the first time to fit modelled Vibrational Raman Scattering (VRS) in liquid water and in s...

  11. Observation of Quiet Limb in He I 1083.0 nm, H Paschen alpha1281.8 nm and H Brackett gamma 2166.1 nm lines

    Prasad Choudhary, Debi

    2016-05-01

    In this paper, we shall present the results of an observational study of the quiet solar limb in the near infrared lines using the New IR Array Camera (NAC) and the vertical spectrograph at the focal plane of McMath-Pierce telescope. The NAC, at the exit port of the spectrograph, was used to record the limb spectrum in HeI 1083.0 nm, Hydrogen Paschen 1281.8 nm and Brackett 2165.5 nm wavelength regions. The NAC is a 1024x1024 InSb Alladin III Detector operating over 1-5 micron range with high density sampling at 0.018 arc second/pixel. The all-reflective optical train minimizes number of surfaces and eliminates ghosts leading to low scatter, ghost-free optics. The close-cycle cryogenic provides a stable cooling environment over six hour period with an accuracy of 0.01K leading to low dark current. The low read out noise combined with low scattered light and dark current makes NAC an ideal detector for making high quality infrared spectral observations of solar limb. The limb spectrums were obtained by placing the spectrograph slit perpendicular to the limb at an interval of 10 degrees around the solar disk. We shall report the intensity profile, line-of-sight velocity and line width distribution around the sun derived from the spectra along the slit.

  12. In-vivo multi-spectral confocal microscopy

    Rouse, Andrew R.; Udovich, Joshua A.; Gmitro, Arthur F.

    2005-03-01

    A multi-spectral confocal microendoscope (MCME) for in-vivo imaging has been developed. The MCME employs a flexible fiber-optic catheter coupled to a slit-scan confocal microscope with an imaging spectrometer. The catheter consists of a fiber-optic imaging bundle linked to a miniature objective and focus assembly. The focus mechanism allows for imaging to a maximum tissue depth of 200 microns. The 3mm diameter catheter may be used on its own or routed though the instrument channel of a commercial endoscope. The confocal nature of the system provides optical sectioning with 3 micron lateral resolution and 30 micron axial resolution. The system incorporates two laser sources and is therefore capable of simultaneous acquisition of spectra from multiple dyes using dual excitation. The prism based multi-spectral detection assembly is typically configured to collect 30 spectral samples over the visible range. The spectral sampling rate varies from 4nm/pixel at 490nm to 8nm/pixel at 660nm and the minimum resolvable wavelength difference varies from 8nm to 16nm over the same spectral range. Each of these characteristics are primarily dictated by the dispersion characteristics of the prism. The MCME is designed to examine cellular structures during optical biopsy and to exploit the diagnostic information contained within the spectral domain. The primary applications for the system include diagnosis of disease in the gastro-intestinal tract and female reproductive system. In-vitro, and ex-vivo multi-spectral results are presented.

  13. Photoreceptor spectral sensitivity in the bumblebee, Bombus impatiens (Hymenoptera: Apidae.

    Peter Skorupski

    Full Text Available The bumblebee Bombus impatiens is increasingly used as a model in comparative studies of colour vision, or in behavioural studies relying on perceptual discrimination of colour. However, full spectral sensitivity data on the photoreceptor inputs underlying colour vision are not available for B. impatiens. Since most known bee species are trichromatic, with photoreceptor spectral sensitivity peaks in the UV, blue and green regions of the spectrum, data from a related species, where spectral sensitivity measurements have been made, are often applied to B impatiens. Nevertheless, species differences in spectral tuning of equivalent photoreceptor classes may result in peaks that differ by several nm, which may have small but significant effects on colour discrimination ability. We therefore used intracellular recording to measure photoreceptor spectral sensitivity in B. impatiens. Spectral peaks were estimated at 347, 424 and 539 nm for UV, blue and green receptors, respectively, suggesting that this species is a UV-blue-green trichromat. Photoreceptor spectral sensitivity peaks are similar to previous measurements from Bombus terrestris, although there is a significant difference in the peak sensitivity of the blue receptor, which is shifted in the short wave direction by 12-13 nm in B. impatiens compared to B. terrestris.

  14. Equivariant Lorentzian Spectral Triples

    Paschke, Mario; Sitarz, Andrzej

    2006-01-01

    We present examples of equivariant noncommutative Lorentzian spectral geometries. The equivariance with respect to a compact isometry group (or quantum group) allows to construct the algebraic data of a version of spectral triple geometry adapted to the situation of an indefinite metric. The spectrum of the equivariant Dirac operator is calculated.

  15. Hydrocarbon Spectral Database

    SRD 115 Hydrocarbon Spectral Database (Web, free access)   All of the rotational spectral lines observed and reported in the open literature for 91 hydrocarbon molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty and reference are given for each transition reported.

  16. On Longitudinal Spectral Coherence

    Kristensen, Leif

    1979-01-01

    It is demonstrated that the longitudinal spectral coherence differs significantly from the transversal spectral coherence in its dependence on displacement and frequency. An expression for the longitudinal coherence is derived and it is shown how the scale of turbulence, the displacement between ...

  17. The High Spectral Resolution Lidar

    Eloranta, E. W.; Roesler, F. L.; Sroga, J. T.

    1983-01-01

    The High Spectral Resolution Lidar (HSRL) system was developed for the remote measurement of atmospheric optical properties. Measurements are obtained by the separation of the backscattered signal into aerosol and molecular channels using a high spectral resolution Fabry-Perot optical interferometer to separate the aerosol contributions to backscatter near the laser wavelength from the Doppler-shifted molecular component of the backscatter. The transmitter consists of an optically pumped pulsed dye laser of the oscillator-amplifier design which emits at 467.88 nm, with a bandwidth of less than 0.3 pm. The transmitter and receiver share a common Schmidt-Cassegrain telescope, although they do not share the same field stop, but rather two conjugate stops. The HSRL system uses a computer-controlled dual-channel photon-counting data acquisition system providing for stable measurements at very low power levels and an excellent dynamic range. The system has been used to obtain airborne measurements of height profiles of aerosol and molecular backscatter cross sections.

  18. Spectral analysis of Cu2+ and Mn2+ ions doped borofluorophosphate glasses

    B Sudhakar Reddy; S Buddhudu

    2007-10-01

    We report here on the development and spectral analysis of Cu2+ (0.5 mol%) and Mn2+ (0.5 mol%) ions doped in two new series of glasses. The visible absorption spectra of Cu2+ and Mn2+ glasses have shown broad absorption bands at 820 nm and 495 nm, respectively. For Cu2+ BFP glasses, excitation at 380 nm, a blue emission at 441 nm and also a weak emission at 418 nm ions have been observed. For Mn2+ ions doped BFP glasses, excitation at 410 nm and a red shift at 605 nm emission have been observed.

  19. Validation of spectral sky radiance derived from all-sky camera images – a case study

    K. Tohsing

    2014-01-01

    Full Text Available Spectral sky radiance (380–760 nm is derived from measurements with a Hemispherical Sky Imager (HSI system. The HSI consists of a commercial compact CCD (charge coupled device camera equipped with a fish-eye lens and provides hemispherical sky images in three reference bands such as red, green and blue. To obtain the spectral sky radiance from these images non-linear regression functions for various sky conditions have been derived. The camera-based spectral sky radiance was validated by spectral sky radiance measured with a CCD spectroradiometer. The spectral sky radiance for complete distribution over the hemisphere between both instruments deviates by less than 20% at 500 nm for all sky conditions and for zenith angles less than 80°. The reconstructed spectra of the wavelength 380 nm to 760 nm between both instruments at various directions deviate by less then 20% for all sky conditions.

  20. 1064-nm Fabry-Perot transmission filter laser damage competition

    Stolz, Christopher J.; Caputo, Mark; Griffin, Andrew J.; Thomas, Michael D.

    2014-10-01

    Narrow-bandwidth Fabry-Perot transmission filters are used in telecommunications, fiber lasers1, and for diode pumped alkali lasers (DPAL)2. Because of their interference properties, extremely high standing-wave electric fields occur at peak transmission. For this study, the filters met a minimum transmission of 90% and were spectrally centered within an angle tuning range of 10-30 degrees. A blind laser damage test assured sample and submitter anonymity. The participants selected the coating materials, design, spectral bandwidth, cleaning method, and deposition method. Laser damage testing was performed at a wavelength of 1064 nm using a raster scan method on a single testing facility to enable a direct comparison among the participants. Pulse length scaling relationships were explored by laser damage testing at a 3.5-ns and 18-ns pulse length. The results show that the spectral bandwidth had the strongest relationship to the laser damage threshold. Other parameters such as deposition processes, cleaning method, coating materials, and layer count were also explored.

  1. Modelling Ar II spectral emission from the ASTRAL helicon plasma

    Munoz Burgos, Jorge; Boivin, Robert; Loch, Stuart; Kamar, Ola; Ballance, Connor; Pindzola, Mitch

    2008-11-01

    We describe our spectral modeling of ArII emission from the ASTRAL helicon plasma at Auburn University. Collisional-radiative theory is used to model the emitted spectrum, with account being taken for the density and temperature variation along the line of sight. This study has two main aims. Firstly to test the atomic data used in the model and secondly to identify spectral line ratios in the 200 nm - 1000 nm range that could be used as temperature diagnostics. Using the temperature at which Ar II emission starts to be seen we have been able to test recent ionization and recombination data. Using selected spectral lines we were then able to test the importance of the continuum-coupling effects included in the most recent Ar+ electron impact excitation data. Selected spectral line ratios have been identified that show a strong temperature variation and have potential as a temperature diagnostic.

  2. Spectral radius of graphs

    Stevanovic, Dragan

    2014-01-01

    Spectral Radius of Graphs provides a thorough overview of important results on the spectral radius of adjacency matrix of graphs that have appeared in the literature in the preceding ten years, most of them with proofs, and including some previously unpublished results of the author. The primer begins with a brief classical review, in order to provide the reader with a foundation for the subsequent chapters. Topics covered include spectral decomposition, the Perron-Frobenius theorem, the Rayleigh quotient, the Weyl inequalities, and the Interlacing theorem. From this introduction, the

  3. Spectral signatures of hydrilla from a tank and field setting

    Alfonso BLANCO; John J.QU; William E.ROPER

    2012-01-01

    The invasion of hydrilla in many waterways has caused significant problems resulting in high maintenance costs for eradicating this invasive aquatic weed.Present identification methods employed for detecting hydrilla invasions such as aerial photography and videos are difficult,costly,and time consuming.Remote sensing has been used for assessing wetlands and other aquatic vegetation,but very little information is available for detecting hydrilla invasions in coastal estuaries and other water bodies.The objective of this study is to construct a library of spectral signatures for identifying and classifying hydrilla invasions.Spectral signatures of hydrilla were collected from an experimental tank and field locations in a coastal estuary in the upper Chesapeake Bay.These measurements collected from the experimental tank,resulted in spectral signatures with an average peak surface reflectance in the near-infrared (NIR) region of 16% at a wavelength of 818 nm.However,the spectral measurements,collected in the estuary,resulted in a very different spectral signature with two surface reflectance peaks of 6% at wavelengths of 725 nm and 818 nm.The difference in spectral signatures between sites are a result of the components in the water column in the estuary because of increased turbidity (e.g.,nutrients,dissolved matter and suspended matter),and canopy being lower (submerged) in the water column.Spectral signatures of hydrilla observed in the tank and the field had similar characteristics with low reflectance in visible region of the spectrum from 400 to 700 nm,but high in the NIR region from 700 to 900 nm.

  4. Lyman alpha solar spectral irradiance line profile observations and models

    Snow, Martin; Machol, Janet; Quemerais, Eric; Curdt, Werner; Kretschmar, Matthieu; Haberreiter, Margit

    2016-04-01

    Solar lyman alpha solar spectral irradiance measurements are available on a daily basis, but only the 1-nm integrated flux is typically published. The International Space Science Institute (ISSI) in Bern, Switzerland has sponsored a team to make higher spectral resolution data available to the community. Using a combination of SORCE/SOLSTICE and SOHO/SUMER observations plus empirical and semi-empirical modeling, we will produce a dataset of the line profile. Our poster will describe progress towards this goal.

  5. Spectral albedo of arctic snow during intensive melt period

    O. Meinander; Kazadzis, S.; A. Arola; Kivi, R.; Kontu, A.; H. Suokanerva; Aaltonen, V.; Manninen, T.; J.-L. Roujean; O. Hautecoeur

    2010-01-01

    Spectral albedo and water liquid content of intensively melting Arctic snow were measured during the Snow Reflectance Transition Experiment (SNORTEX), in Sodankylä, Finland, in April 2009. The upwelling and downwelling spectral irradiance, measured at 290–550 nm with a double monochromator spectroradiometer, revealed the snow albedo to increase as a function wavelength. At the same time, we found the albedo of melting snow to decrease by ~10%, as a function of time within one day. During four...

  6. Vowel Inherent Spectral Change

    Assmann, Peter

    2013-01-01

    It has been traditional in phonetic research to characterize monophthongs using a set of static formant frequencies, i.e., formant frequencies taken from a single time-point in the vowel or averaged over the time-course of the vowel. However, over the last twenty years a growing body of research has demonstrated that, at least for a number of dialects of North American English, vowels which are traditionally described as monophthongs often have substantial spectral change. Vowel Inherent Spectral Change has been observed in speakers’ productions, and has also been found to have a substantial effect on listeners’ perception. In terms of acoustics, the traditional categorical distinction between monophthongs and diphthongs can be replaced by a gradient description of dynamic spectral patterns. This book includes chapters addressing various aspects of vowel inherent spectral change (VISC), including theoretical and experimental studies of the perceptually relevant aspects of VISC, the relationship between ar...

  7. Large-mode-area hybrid photonic crystal fiber amplifier at 1178 nm

    Petersen, Sidsel Rübner; Chen, Mingchen; Shirakawa, Akira; Olausson, Christina Bjarnal Thulin; Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper

    2015-01-01

    Amplification of 1178 nm light is demonstrated in a large-mode-area single-mode ytterbium-doped hybrid photonic crystal fiber, relying on distributed spectral filtering of spontaneous emission at shorter wavelengths. An output power of 53 W is achieved with 29 dB suppression of parasitic lasing...

  8. [Study on spectral reflectance characteristics of hemp canopies].

    Tian, Yi-Chen; Jia, Kun; Wu, Bing-Fang; Li, Qiang-Zi

    2010-12-01

    Hemp (Cannabis sativa L.) is a special economic crop and widely used in many field. It is significative for the government to master the information about planting acreage and spatial distribution of hemp for hemp industrial policy decision in China. Remote sensing offers a potential way of monitoring large area for the cultivation of hemp. However, very little study on the spectral properties of hemp is available in the scientific literature. In the present study, the spectral reflectance characteristics of hemp canopy were systematically analyzed based on the spectral data acquired with ASD FieldSpec portable spectrometer. The wavebands and its spectral resolution for discriminating hemp from other plants were identified using difference analysis. The major differences in canopy reflectance of hemp and other plants were observed near 530, 552, 734, 992, 1 213, 1 580 and 2 199 nm, and the maximal difference is near 734 nm. The spectral resolution should be 30 nm or less in visible and near infrared regions, and 50 nm or less in middle infrared regions. PMID:21322234

  9. LCTF Spectral Parameters Stability

    Pons, Alicia; Peralta, Celia; Campos, Joaquín; Negueruela, Angel I.; Rabal, A.; Martínez, T.

    2009-01-01

    Liquid crystal tunable filters (LCTF) are being widely used as spectral analysis system in different applications, particularly in color imaging and multispectral imaging. This work presents a study on the stability, at short and long terms, of the parameters defining the bandpass function: spectral distribution of transmittance maximum, bandwidth and mean or effective wavelength, λm, calculated according to the Full Wide Half Maximum (FWHM) criterion. Measurements have been made by a direct ...

  10. External-cavity diamond Raman laser performance at 1240 nm and 1485 nm wavelengths with high pulse energy

    Pashinin, V. P.; Ralchenko, V. G.; Bolshakov, A. P.; Ashkinazi, E. E.; Gorbashova, M. A.; Yurov, V. Yu; Konov, V. I.

    2016-06-01

    We report on an external-cavity diamond Raman laser (DRL) pumped with a Q-switched Nd:YAG and generating at 1st and 2nd Stokes (1240 nm and 1485 nm) with enhanced output energy. The slope efficiency of 54% and output energy as high as 1.2 mJ in single pulse at 1240 nm have been achieved with optimized cavity, while the pulse energy of 0.70 mJ was obtained in the eye-safe spectral region at 1485 nm. Calculations of thermal lensing effect indicate it as a possible reason for the observed decrease in conversion efficiency at the highest pump energies.

  11. Spectrally selective glazings

    NONE

    1998-08-01

    Spectrally selective glazing is window glass that permits some portions of the solar spectrum to enter a building while blocking others. This high-performance glazing admits as much daylight as possible while preventing transmission of as much solar heat as possible. By controlling solar heat gains in summer, preventing loss of interior heat in winter, and allowing occupants to reduce electric lighting use by making maximum use of daylight, spectrally selective glazing significantly reduces building energy consumption and peak demand. Because new spectrally selective glazings can have a virtually clear appearance, they admit more daylight and permit much brighter, more open views to the outside while still providing the solar control of the dark, reflective energy-efficient glass of the past. This Federal Technology Alert provides detailed information and procedures for Federal energy managers to consider spectrally selective glazings. The principle of spectrally selective glazings is explained. Benefits related to energy efficiency and other architectural criteria are delineated. Guidelines are provided for appropriate application of spectrally selective glazing, and step-by-step instructions are given for estimating energy savings. Case studies are also presented to illustrate actual costs and energy savings. Current manufacturers, technology users, and references for further reading are included for users who have questions not fully addressed here.

  12. Thermophotovoltaic Spectral Control

    DM DePoy; PM Fourspring; PF Baldasaro; JF Beausang; EJ Brown; MW Dashiel; KD Rahner; TD Rahmlow; JE Lazo-Wasem; EJ Gratrix; B Wemsman

    2004-06-09

    Spectral control is a key technology for thermophotovoltaic (TPV) direct energy conversion systems because only a fraction (typically less than 25%) of the incident thermal radiation has energy exceeding the diode bandgap energy, E{sub g}, and can thus be converted to electricity. The goal for TPV spectral control in most applications is twofold: (1) Maximize TPV efficiency by minimizing transfer of low energy, below bandgap photons from the radiator to the TPV diode. (2) Maximize TPV surface power density by maximizing transfer of high energy, above bandgap photons from the radiator to the TPV diode. TPV spectral control options include: front surface filters (e.g. interference filters, plasma filters, interference/plasma tandem filters, and frequency selective surfaces), back surface reflectors, and wavelength selective radiators. System analysis shows that spectral performance dominates diode performance in any practical TPV system, and that low bandgap diodes enable both higher efficiency and power density when spectral control limitations are considered. Lockheed Martin has focused its efforts on front surface tandem filters which have achieved spectral efficiencies of {approx}83% for E{sub g} = 0.52 eV and {approx}76% for E{sub g} = 0.60 eV for a 950 C radiator temperature.

  13. Spectral flow inside essential spectrum

    Azamov, Nurulla

    2014-01-01

    The spectral flow is a classical notion of functional analysis and differential geometry which was given different interpretations as Fredholm index, Witten index, and Maslov index. The classical theory treats spectral flow outside the essential spectrum. Inside essential spectrum, the spectral shift function could be considered as a proper analogue of spectral flow, but unlike the spectral flow, the spectral shift function is not an integer-valued function. In this paper it is shown that the...

  14. NBS (National Bureau of Standards) measurement services: spectral-irradiance calibrations. Special pub. (Final)

    The report describes the measurement methods and instrumentation used in realization and transfer of the NBS scale of spectral irradiance. The basic measurement equation for the irradiance realization is derived. The spectral responsivity function, linearity of response, and size of source effect of the spectroradiometer are described. The analysis of sources of error and estimates of uncertainty are described. The analysis of sources of error and estimates of uncertainty are described. The assigned uncertainties (3-sigma level) in spectral irradiance range from 2.2% at 250 nm to 1.0% at 654.6 nm to 6.5% at 2400 nm

  15. Increased spectral bandwidths in nonlinear conversion processes by use of multicrystal designs.

    Brown, M

    1998-10-15

    The fourth-harmonic generation of broadband 243-nm radiation is reported. The broadband radiation is achieved by implementation of a multicrystal design to overcome spectral bandwidth limitations, and a plane-wave analysis is developed that shows increased spectral bandwidths for these designs. The fourth harmonic of a Cr:LiSAF laser operating at 972 nm is generated in beta-barium borate (BBO). The results demonstrate a spectral bandwidth at 243 nm more than five times broader than that which is expected from a single BBO crystal of equivalent length. PMID:18091854

  16. Dust Explosion Characteristics of Agglomerated 35 nm and 100 nm Aluminum Particles

    Hong-Chun Wu

    2010-01-01

    Full Text Available In the experiment, nanoparticles of 35 nm Al and 100 nm Al powders, respectively, formed particles with average sizes of 161 nm and 167 nm in agglomeration. The characteristics of dust cloud explosions with the two powder sizes, 35 nm and 100 nm, revealed considerable differences, as shown here: (dp/dtmax-35 nm = 1254 bar/s, (dp/dtmax-100 nm = 1105 bar/s; Pmax-35 nm = 7.5 bar, Pmax-100 nm = 12.3 bar, and MEC-35 nm = 40 g/m3, MEC-100 nm = 50 g/m3. The reason of Pmax-35 nm value is smaller than Pmax-100 nm may be due to agglomeration. From an analysis of the explosive residue, the study found that nanoparticles of 35 nm Al powder became filamentous strands after an explosion, where most of 100 nm Al nanoparticles maintained a spherical structure, This may be because the initial melting temperature of 35 nm Al is 435.71°C, while that for 100 nm Al is 523.58°C, higher by 87.87°C. This study discovered that explosive property between the 35 nm Al and 100 nm Al powders after agglomeration were different.

  17. Shot-to-shot spectrally-resolved characterization of continuous-wave-triggered supercontinuum near 1 um

    Ren, Zhibo; Wong, Kenneth K Y; Tsia, Kevin

    2013-01-01

    We demonstrate shot-to-shot (at a rate of 20 MHz), broadband (>200 nm), spectrally-resolved (spectral resolution of 0.2 nm) statistical characterization of continuous-wave-triggered supercontinuum in the 1 um regime, enabled by optical time stretch.

  18. A 23-dB bismuth-doped optical fiber amplifier for a 1700-nm band.

    Firstov, Sergei V; Alyshev, Sergey V; Riumkin, Konstantin E; Khopin, Vladimir F; Guryanov, Alexey N; Melkumov, Mikhail A; Dianov, Evgeny M

    2016-01-01

    It is now almost twenty-five years since the first Erbium-Doped Fiber Amplifier (EDFA) was demonstrated. Currently, the EDFA is one of the most important elements widely used in different kinds of fiber-optic communication systems. However, driven by a constantly increasing demand, the network traffic, growing exponentially over decades, will lead to the overload of these systems ("capacity crunch") because the operation of the EDFA is limited to a spectral region of 1530-1610 nm. It will require a search for new technologies and, in this respect, the development of optical amplifiers for new spectral regions can be a promising approach. Most of fiber-optic amplifiers are created using rare-earth-doped materials. As a result, wide bands in shorter (1150-1530 nm) and longer wavelength (1600-1750 nm) regions with respect to the gain band of Er-doped fibers are still uncovered. Here we report on the development of a novel fiber amplifier operating in a spectral region of 1640-1770 nm pumped by commercially available laser diodes at 1550 nm. This amplifier was realized using bismuth-doped high-germania silicate fibers fabricated by MCVD technique. PMID:27357592

  19. Spectral confocal reflection microscopy using a white light source

    Booth, M.; Juškaitis, R.; Wilson, T.

    2008-08-01

    We present a reflection confocal microscope incorporating a white light supercontinuum source and spectral detection. The microscope provides images resolved spatially in three-dimensions, in addition to spectral resolution covering the wavelength range 450-650nm. Images and reflection spectra of artificial and natural specimens are presented, showing features that are not normally revealed in conventional microscopes or confocal microscopes using discrete line lasers. The specimens include thin film structures on semiconductor chips, iridescent structures in Papilio blumei butterfly scales, nacre from abalone shells and opal gemstones. Quantitative size and refractive index measurements of transparent beads are derived from spectral interference bands.

  20. High Resolving Power Volume Diffractive Gratings for 400-2700 nm Spectral Range Project

    National Aeronautics and Space Administration — The main purpose of this NASA SBIR Phase II proposal is development of a novel type of high resolving power diffraction gratings based on volume Bragg gratings...

  1. Comparison of Molecular Iodine Spectral Properties at 514.7 and 532 nm Wavelengths

    Hrabina, Jan; Acef, O.; Du Burck, F.; Chiodo, N.; Candela, Y.; Šarbort, Martin; Holá, Miroslava; Lazar, Josef

    2014-01-01

    Roč. 14, č. 4 (2014), s. 213-218. ISSN 1335-8871 R&D Projects: GA ČR GPP102/11/P820; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01; GA MŠk EE2.4.31.0016; GA TA ČR TA02010711; GA TA ČR TA01010995; GA TA ČR TE01020233 Institutional support: RVO:68081731 Keywords : laser spectroscopy * metrology * molecular iodine * absorption cells * frequency doubling * nterferometry Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.989, year: 2014

  2. High Resolving Power Volume Diffractive Gratings for 400-2700 nm Spectral Range Project

    National Aeronautics and Space Administration — The purpose of this NASA SBIR Phase I proposal is to develop a novel type of high resolving power diffraction gratings based on volume Bragg gratings technology....

  3. Ytterbium‐doped distributed spectral filtering photonic crystal fibers for use at wavelengths above 1100 nm

    Petersen, Sidsel Rübner; Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper

    Rare‐earth doped high‐power fiber lasers and amplifiers have attracted a lot of attention, due to the advantages of the fiber amplification scheme. Compared to conventional optically pumped bulk lasers, heat is dissipated much more effectively in fiber lasers, having a large surface......‐to‐active volume ratio. Thereby, a stable beam with nearly diffraction‐limited quality can be achieved. The fibers are often cladding‐pumped with a number of low‐brightness semiconductor laser diodes, in which way a low‐cost pump of several kilowatts can be achieved [1]. However, the frequencies, which can be...... can reach the yellow‐orange light regime through frequency doubling. Yellow‐orange light has applications within the medical industry, high‐resolution spectroscopy and for laser‐guide stars [2]. To achieve amplification at these wavelengths, the larger gain at shorter wavelengths must be suppressed to...

  4. Narrow linewidth broadband tunable semiconductor laser at 840 nm with dual acousto-optic tunable configuration for OCT applications

    Chamorovskiy, Alexander; Shramenko, Mikhail V.; Lobintsov, Andrei A.; Yakubovich, Sergei D.

    2016-03-01

    We demonstrate a tunable narrow linewidth semiconductor laser for the 840 nm spectral range. The laser has a linear cavity comprised of polarization maintaining (PM) fiber. A broadband semiconductor optical amplifier (SOA) in in-line fiber-coupled configuration acts as a gain element. It is based on InGaAs quantum-well (QW) active layer. SOA allows for tuning bandwidth exceeding 25 nm around 840 nm. Small-signal fiber-to-fiber gain of SOA is around 30 dB. A pair of acousto-optic tunable filters (AOTF) with a quasi-collinear interaction of optical and acoustic waves are utilized as spectrally selective elements. AOTF technology benefits in continuous tuning, broadband operation, excellent reproducibility and stability of the signal, as well as a high accuracy of wavelength selectivity due to the absence of mechanically moving components. A single AOTF configuration has typical linewidth in 0.05-0.15 nm range due to a frequency shift obtained during each roundtrip. A sequential AOTF arrangement enables instantaneous linewidth generation of <0.01 nm by compensating for this shift. Linewidth as narrow as 0.0036 nm is observed at 846 nm wavelength using a scanning Fabry-Perot interferometer with 50 MHz spectral resolution. Output power is in the range of 1 mW. While the majority of commercial tunable sources operate in 1060-1550 nm spectral ranges, the 840 nm spectral range is beneficial for optical coherence tomography (OCT). The developed narrow linewidth laser can be relevant for OCT with extended imaging depth, as well as spectroscopy, non-destructive testing and other applications.

  5. Laser hypersensitisation using 266nm light

    Sørensen, Henrik Rokkjær; Canning, J.; Kristensen, Martin

    2005-01-01

    UV hypersensitisation using CW 266 nm light on hydrogenated Ge-doped fibre is reported. The optimum sensitisation fluence is found to be in the range of 5 to 10 kJ/cm2, coinciding with previous results obtained using 355 nm light, indicating the same end-process used in the photochemical reaction...

  6. Accurate Measurements of Spectral Reflectance in Picasso's Guernica Painting.

    de Luna, Javier Muñoz; Fernandez-Balbuena, Antonio Alvarez; Vázquez, Daniel; Melgosa, Manuel; Durán, Humberto; García, Jorge; Muro, Carmen

    2016-01-01

    The use of non-invasive spectral measurements to control the conservation status is a part of the preventive conservation of artworks which nowadays is becoming increasingly interesting. This paper describes how to use a spectral measuring device and an illumination system specifically designed for such a task in a very large dimension artwork painting (7.8 m wide × 3.5 m high). The system, controlled by a Cartesian robot, allows spectral measurements in a spectral range of 400-780 nm. The measured data array has a total of 2201 circular regions with 5.5 mm spot diameter placed on a square grid. Colorimetric calculations performed from these spectral measurements may be used to characterize color shifts related to reflectance changes in specific areas of the paint. A color shifting from the expected gray has been shown. PMID:26767640

  7. Soybean Aphid (Hemiptera: Aphididae) Affects Soybean Spectral Reflectance.

    Alves, Tavvs M; Macrae, Ian V; Koch, Robert L

    2015-12-01

    Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is the most economically important insect pest of soybean in the north central United States. Scouting-based integrated pest management (IPM) programs could become more efficient and more widely adopted by using plant spectral reflectance to estimate soybean aphid injury. Our objective was to determine whether plant spectral reflectance is affected by soybean aphid feeding. Field trials were conducted in 2013 and 2014 using caged plots. Early-, late-, and noninfested treatments were established to create a gradient of soybean aphid pressure. Whole-plant soybean aphid densities were recorded weekly. Measurements of plant spectral reflectance occurred on two sample dates per year. Simple linear regression models were used to test the effect of cumulative aphid-days (CAD) on plant spectral reflectance at 680 nm (RED) and 800 nm (NIR), normalized difference vegetation index (NDVI), and relative chlorophyll content. Data indicated that CAD had no effect on canopy-level RED reflectance, but CAD decreased canopy-level NIR reflectance and NDVI. Canopy- and leaf-level measurements typically indicated similar plant spectral response to increasing CAD. CAD generally had no effect on relative chlorophyll content. The present study provides the first documentation that remote sensing holds potential for detecting changes in plant spectral reflectance induced by soybean aphid. The use of plant spectral reflectance in soybean aphid management may assist future IPM programs to reduce sampling costs and prevent prophylactic insecticide sprays. PMID:26470392

  8. Indium determination by spectral overlappings of lines in atomic absorption spectrometry

    A molybdenum hollow-cathode lamp filled with neon can be used to determine indium. Characteristic concentration for this element is 4.5 mg/L in the 325 nm spectral region for the Mo(I) 325.621 nm line. In addition, values of 0.4 mg/L and 0.3 mg/L are obtained with the Mo(I) 410.215 nm and Ne(I) 451.151 nm lines, respectively. These spectral overlappings allow the determination of indium in silver-cadmium-indium alloys. (Author)

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

    Pu, Minhao; Ji, Hua; Frandsen, Lars Hagedorn;

    2009-01-01

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

  10. Aqueous glucose measurement using differential absorption-based frequency domain optical coherence tomography at wavelengths of 1310 nm and 1625 nm

    John, Pauline; Manoj, Murali; Sujatha, N.; Vasa, Nilesh J.; Rao, Suresh R.

    2015-07-01

    This work presents a combination of differential absorption technique and frequency domain optical coherence tomography for detection of glucose, which is an important analyte in medical diagnosis of diabetes. Differential absorption technique is used to detect glucose selectively in the presence of interfering species especially water and frequency domain optical coherence tomography (FDOCT) helps to obtain faster acquisition of depth information. Two broadband super-luminescent diode (SLED) sources with centre wavelengths 1586 nm (wavelength range of 1540 to 1640 nm) and 1312 nm (wavelength range of 1240 to 1380 nm) and a spectral width of ≍ 60 nm (FWHM) are used. Preliminary studies on absorption spectroscopy using various concentrations of aqueous glucose solution gave promising results to distinguish the absorption characteristics of glucose at two wavelengths 1310 nm (outside the absorption band of glucose) and 1625 nm (within the absorption band of glucose). In order to mimic the optical properties of biological skin tissue, 2% and 10% of 20% intralipid with various concentrations of glucose (0 to 4000 mg/dL) was prepared and used as sample. Using OCT technique, interference spectra were obtained using an optical spectrum analyzer with a resolution of 0.5 nm. Further processing of the interference spectra provided information on reflections from the surfaces of the cuvette containing the aqueous glucose sample. Due to the absorption of glucose in the wavelength range of 1540 nm to 1640 nm, a trend of reduction in the intensity of the back reflected light was observed with increase in the concentration of glucose.

  11. Parametric Explosion Spectral Model

    Ford, S R; Walter, W R

    2012-01-19

    Small underground nuclear explosions need to be confidently detected, identified, and characterized in regions of the world where they have never before occurred. We develop a parametric model of the nuclear explosion seismic source spectrum derived from regional phases that is compatible with earthquake-based geometrical spreading and attenuation. Earthquake spectra are fit with a generalized version of the Brune spectrum, which is a three-parameter model that describes the long-period level, corner-frequency, and spectral slope at high-frequencies. Explosion spectra can be fit with similar spectral models whose parameters are then correlated with near-source geology and containment conditions. We observe a correlation of high gas-porosity (low-strength) with increased spectral slope. The relationship between the parametric equations and the geologic and containment conditions will assist in our physical understanding of the nuclear explosion source.

  12. Photovoltaic spectral responsivity measurements

    Emery, K.; Dunlavy, D.; Field, H.; Moriarty, T. [National Renewable Energy Lab., Golden, CO (United States)

    1998-09-01

    This paper discusses the various elemental random and nonrandom error sources in typical spectral responsivity measurement systems. The authors focus specifically on the filter and grating monochrometer-based spectral responsivity measurement systems used by the Photovoltaic (PV) performance characterization team at NREL. A variety of subtle measurement errors can occur that arise from a finite photo-current response time, bandwidth of the monochromatic light, waveform of the monochromatic light, and spatial uniformity of the monochromatic and bias lights; the errors depend on the light source, PV technology, and measurement system. The quantum efficiency can be a function of he voltage bias, light bias level, and, for some structures, the spectral content of the bias light or location on the PV device. This paper compares the advantages and problems associated with semiconductor-detector-based calibrations and pyroelectric-detector-based calibrations. Different current-to-voltage conversion and ac photo-current detection strategies employed at NREL are compared and contrasted.

  13. Description and availability of the SMARTS spectral model for photovoltaic applications

    Myers, Daryl R.; Gueymard, Christian A.

    2004-11-01

    Limited spectral response range of photocoltaic (PV) devices requires device performance be characterized with respect to widely varying terrestrial solar spectra. The FORTRAN code "Simple Model for Atmospheric Transmission of Sunshine" (SMARTS) was developed for various clear-sky solar renewable energy applications. The model is partly based on parameterizations of transmittance functions in the MODTRAN/LOWTRAN band model family of radiative transfer codes. SMARTS computes spectra with a resolution of 0.5 nanometers (nm) below 400 nm, 1.0 nm from 400 nm to 1700 nm, and 5 nm from 1700 nm to 4000 nm. Fewer than 20 input parameters are required to compute spectral irradiance distributions including spectral direct beam, total, and diffuse hemispherical radiation, and up to 30 other spectral parameters. A spreadsheet-based graphical user interface can be used to simplify the construction of input files for the model. The model is the basis for new terrestrial reference spectra developed by the American Society for Testing and Materials (ASTM) for photovoltaic and materials degradation applications. We describe the model accuracy, functionality, and the availability of source and executable code. Applications to PV rating and efficiency and the combined effects of spectral selectivity and varying atmospheric conditions are briefly discussed.

  14. Sub-10 nm nanopantography

    Tian, Siyuan, E-mail: siyuan.tian@lamresearch.com; Donnelly, Vincent M., E-mail: vmdonnelly@uh.edu, E-mail: economou@uh.edu; Economou, Demetre J., E-mail: vmdonnelly@uh.edu, E-mail: economou@uh.edu [Plasma Processing Laboratory, Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204 (United States); Ruchhoeft, Paul, E-mail: pruchhoeft@uh.edu [Department of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204 (United States)

    2015-11-09

    Nanopantography, a massively parallel nanopatterning method over large areas, was previously shown to be capable of printing 10 nm features in silicon, using an array of 1000 nm-diameter electrostatic lenses, fabricated on the substrate, to focus beamlets of a broad area ion beam on selected regions of the substrate. In the present study, using lens dimensional scaling optimized by computer simulation, and reduction in the ion beam image size and energy dispersion, the resolution of nanopantography was dramatically improved, allowing features as small as 3 nm to be etched into Si.

  15. Low-Cost Spectral Sensor Development Description.

    Armijo, Kenneth Miguel; Yellowhair, Julius

    2014-11-01

    Solar spectral data for all parts of the US is limited due in part to the high cost of commercial spectrometers. Solar spectral information is necessary for accurate photovoltaic (PV) performance forecasting, especially for large utility-scale PV installations. A low-cost solar spectral sensor would address the obstacles and needs. In this report, a novel low-cost, discrete- band sensor device, comprised of five narrow-band sensors, is described. The hardware is comprised of commercial-off-the-shelf components to keep the cost low. Data processing algorithms were developed and are being refined for robustness. PV module short-circuit current ( I sc ) prediction methods were developed based on interaction-terms regression methodology and spectrum reconstruction methodology for computing I sc . The results suggest the computed spectrum using the reconstruction method agreed well with the measured spectrum from the wide-band spectrometer (RMS error of 38.2 W/m 2 -nm). Further analysis of computed I sc found a close correspondence of 0.05 A RMS error. The goal is for ubiquitous adoption of the low-cost spectral sensor in solar PV and other applications such as weather forecasting.

  16. Design and implementation of a sub-nm resolution microspectrometer based on a Linear-Variable Optical Filter.

    Emadi, Arvin; Wu, Huaiwen; de Graaf, Ger; Wolffenbuttel, Reinoud

    2012-01-01

    In this paper the concept of a microspectrometer based on a Linear Variable Optical Filter (LVOF) for operation in the visible spectrum is presented and used in two different designs: the first is for the narrow spectral band between 610 nm and 680 nm, whereas the other is for the wider spectral band between 570 nm and 740 nm. Design considerations, fabrication and measurement results of the LVOF are presented. An iterative signal processing algorithm based on an initial calibration has been implemented to enhance the spectral resolution. Experimental validation is based on the spectrum of a Neon lamp. The results of measurements have been used to analyze the operating limits of the concept and to explain the sources of error in the algorithm. It is shown that the main benefits of a LVOF-based microspectrometer are in case of implementation in a narrowband application. The realized LVOF microspectrometers show a spectral resolution of 2.2 nm in the wideband design and 0.7 nm in the narrowband design. PMID:22274371

  17. Narrow linewidth broadband tunable semiconductor laser at 840 nm with dual acousto-optic tunable configuration for OCT applications

    Chamorovskiy, Alexander; Shramenko, Mikhail V.; Lobintsov, Andrei A.; Yakubovich, Sergei D.

    2016-03-01

    We demonstrate a tunable narrow linewidth semiconductor laser for the 840 nm spectral range. The laser has a linear cavity comprised of polarization maintaining (PM) fiber. A broadband semiconductor optical amplifier (SOA) in in-line fiber-coupled configuration acts as a gain element. It is based on InGaAs quantum-well (QW) active layer. SOA allows for tuning bandwidth exceeding 25 nm around 840 nm. Small-signal fiber-to-fiber gain of SOA is around 30 dB. A pair of acousto-optic tunable filters (AOTF) with a quasi-collinear interaction of optical and acoustic waves are utilized as spectrally selective elements. AOTF technology benefits in continuous tuning, broadband operation, excellent reproducibility and stability of the signal, as well as a high accuracy of wavelength selectivity due to the absence of mechanically moving components. A single AOTF configuration has typical linewidth in 0.05-0.15 nm range due to a frequency shift obtained during each roundtrip. A sequential AOTF arrangement enables instantaneous linewidth generation of power is in the range of 1 mW. While the majority of commercial tunable sources operate in 1060-1550 nm spectral ranges, the 840 nm spectral range is beneficial for optical coherence tomography (OCT). The developed narrow linewidth laser can be relevant for OCT with extended imaging depth, as well as spectroscopy, non-destructive testing and other applications.

  18. Spectral library searching in proteomics.

    Griss, Johannes

    2016-03-01

    Spectral library searching has become a mature method to identify tandem mass spectra in proteomics data analysis. This review provides a comprehensive overview of available spectral library search engines and highlights their distinct features. Additionally, resources providing spectral libraries are summarized and tools presented that extend experimental spectral libraries by simulating spectra. Finally, spectrum clustering algorithms are discussed that utilize the same spectrum-to-spectrum matching algorithms as spectral library search engines and allow novel methods to analyse proteomics data. PMID:26616598

  19. DPAL pump system exceeding 3kW at 766nm and 30 GHz bandwidth

    Koenning, Tobias; McCormick, Dan; Irwin, David; Stapleton, Dean; Guiney, Tina; Patterson, Steve

    2016-03-01

    Due to their low quantum defect, diode pumped alkali metal vapor lasers (DPALs) offer the promise of scalability to very high average power levels while maintaining excellent beam quality. Research on DPALs has progressed to ever increasing power levels across multiple gain media species over the last years, necessitating pump power in the kW range. Each material requires a specific pump wavelength: near 852nm for cesium, 780nm for rubidium, 766nm for potassium, and 670nm for lithium atoms. The shorter pump wavelength below 800nm are outside the typical wavelength range for pump diodes developed for diode pumped solid state lasers (DPSS). The biggest challenge in pumping these materials efficiently is the need for maintaining the narrow gain media absorption band of approximately 0.01nm while greatly increasing power. Typical high power diode lasers achieve spectral widths around 3nm (FWHM) in the near infrared spectrum, but optical gratings may be used internal or external to the cavity to reduce the spectral width. Recently, experimental results have shown yet narrower line widths ranging from picometers at very low power levels to sub-100 picometers for water cooled stacks around 1kW of output power. The focus of this work is the development of a fiber-based pump system for potassium DPAL. The individual tasks are the development of high power 766nm chip material, a fiber-coupled module as a building block, and a scalable system design to address power requirements from hundreds of watts to tens of kilowatts. Results for a 3kW system achieving ~30GHz bandwidth at 766nm will be shown. Approaches for power-scaling and size reduction will be discussed.

  20. A Flat Spectral Response AWG Demultiplexer Composed of Slabs with Islands and Peninsulas

    Yutaka Natsume; Junji Yamauchi; Ryoichi Tazawa; Koji Ishikawa; Shigeru Kawaguchi; Yuichi Yamamoto; Hisamatsu Nakano

    2003-01-01

    Phase adjustment elements called islands and peninsulas are introduced to obtain an AWG demultiplexer with a flat spectral response. Use of the peninsulas enables us to achieve a 1dB bandwidth of 0.5 nm.

  1. A Flat Spectral Response AWG Demultiplexer Composed of Slabs with Islands and Peninsulas

    Yutaka; Natsume; Junji; Yamauchi; Ryoichi; Tazawa; Koji; Ishikawa; Shigeru; Kawaguchi; Yuichi; Yamamoto; Hisamatsu; Nakano

    2003-01-01

    Phase adjustment elements called islands and peninsulas are introduced to obtain an AWG demultiplexer with a flat spectral response. Use of the peninsulas enables us to achieve a IdB bandwidth of 0.5 nm.

  2. Validation of spectral sky radiance derived from all-sky camera images – a case study

    K. Tohsing

    2014-07-01

    Full Text Available Spectral sky radiance (380–760 nm is derived from measurements with a hemispherical sky imager (HSI system. The HSI consists of a commercial compact CCD (charge coupled device camera equipped with a fish-eye lens and provides hemispherical sky images in three reference bands such as red, green and blue. To obtain the spectral sky radiance from these images, non-linear regression functions for various sky conditions have been derived. The camera-based spectral sky radiance was validated using spectral sky radiance measured with a CCD spectroradiometer. The spectral sky radiance for complete distribution over the hemisphere between both instruments deviates by less than 20% at 500 nm for all sky conditions and for zenith angles less than 80°. The reconstructed spectra of the wavelengths 380–760 nm between both instruments at various directions deviate by less than 20% for all sky conditions.

  3. Reconstruction of solar spectral resource using limited spectral sampling for concentrating photovoltaic systems

    Tatsiankou, Viktar; Hinzer, Karin; Mohammed, Jafaru; Muron, Aaron; Wilkins, Matthew; Haysom, Joan; Schriemer, Henry; Myrskog, Stefan

    2013-10-01

    One of the challenges associated with forecasting and evaluating concentrating photovoltaic system (CPV) performance in diverse locations is the lack of high-quality spectral solar resource data. Various local atmospheric conditions such as air mass, aerosols, and atmospheric gases affect daily CPV module operation. A multi-channel filter radiometer (MFCR) can be used to quantify these effects at relatively low cost. The proposed method of selectively sampling the solar spectrum at specific wavelength channels to spectrally reconstruct incident irradiance is described and extensively analyzed. Field spectroradiometer (FSR) measurements at the University of Ottawa's CPV testing facility (45.42°N, 75.68°W) are fed into our model to mimic the outputs from the MCFR. The analysis is performed over a two year period (2011-2012), using 46,564 spectra. A recommendation is made to use four aerosols channels at 420, 500, 780, and 1050 nm, one ozone channel at 610 nm and one water vapour channel at 940 nm, all of which can be measured with ubiquitous Si photodiodes. A simulation of this MFCR channel configuration produces an RMS error under 1.5% over 96% of the 350-1830 nm range, when compared with the FSR, for the 2012 data set in Ottawa.

  4. Tunable high-power narrow-spectrum external-cavity diode laser based on tapered amplifier at 668 nm

    Chi, Mingjun; Erbert, G.; Sumpf, B.;

    2010-01-01

    A 668 nm tunable high-power narrow-spectrum diode laser system based on a tapered semiconductor optical amplifier in external cavity is demonstrated. The laser system is tunable from 659 to 675 nm. As high as 1.38 W output power is obtained at 668.35 nm. The emission spectral bandwidth is less than...... 0.07 nm throughout the tuning range, and the beam quality factor M2 is 2.0 with the output power of 1.27 W....

  5. Laser ablation synthesis and spectral characterization of ruby nanoparticles

    Baranov, M. S.; Bardina, A. A.; Savelyev, A. G.; Khramov, V. N.; Khaydukov, E. V.

    2016-04-01

    The laser ablation method was implemented for synthesis of ruby nanoparticles. Nanoparticles were obtained by nanosecond ablation of bulk ruby crystal in 10% ethanol water solution. The nanoparticles enable water colloid stability and exhibit narrow photoluminescent line at 694 nm when pumped at blue-green spectral range. The ruby nanoparticles were characterized by SEM and Z-sizer.

  6. Laser hypersensitisation using 266nm light

    Sørensen, Henrik Rokkjær; Canning, J.; Kristensen, Martin

    2005-01-01

    UV hypersensitisation using CW 266 nm light on hydrogenated Ge-doped fibre is reported. The optimum sensitisation fluence is found to be in the range of 5 to 10 kJ/cm2, coinciding with previous results obtained using 355 nm light, indicating the same end-process used in the photochemical reaction....... We also report the observation of type IA behaviour using this wavelength.......UV hypersensitisation using CW 266 nm light on hydrogenated Ge-doped fibre is reported. The optimum sensitisation fluence is found to be in the range of 5 to 10 kJ/cm2, coinciding with previous results obtained using 355 nm light, indicating the same end-process used in the photochemical reaction...

  7. Spectral signatures of chirality

    Pedersen, Jesper Goor; Mortensen, Asger

    2009-01-01

    We present a new way of measuring chirality, via the spectral shift of photonic band gaps in one-dimensional structures. We derive an explicit mapping of the problem of oblique incidence of circularly polarized light on a chiral one-dimensional photonic crystal with negligible index contrast to the...

  8. Symmetries of Spectral Problems

    Shabat, A.

    Deriving abelian KdV and NLS hierarchies, we describe non-abelian symmetries and "pre-Lax" elementary approach to Lax pairs. Discrete symmetries of spectral problems are considered in Sect. 4.2. Here we prove Darboux classical theorem and discuss a modern theory of dressing chains.

  9. Spectral Ensemble Kalman Filters

    Mandel, Jan; Kasanický, Ivan; Vejmelka, Martin; Fuglík, Viktor; Turčičová, Marie; Eben, Kryštof; Resler, Jaroslav; Juruš, Pavel

    2014-01-01

    Roč. 11, - (2014), EMS2014-446. [EMS Annual Meeting /14./ & European Conference on Applied Climatology (ECAC) /10./. 06.10.2014-10.10.2014, Prague] R&D Projects: GA ČR GA13-34856S Grant ostatní: NSF DMS -1216481 Institutional support: RVO:67985807 Keywords : data assimilation * spectral filter Subject RIV: DG - Athmosphere Sciences, Meteorology

  10. Blue spectral inflation

    Schunck, Franz E

    2008-01-01

    We reconsider the nonlinear second order Abel equation of Stewart and Lyth, which follows from a nonlinear second order slow-roll approximation. We find a new eigenvalue spectrum in the blue regime. Some of the discrete values of the spectral index n_s have consistent fits to the cumulative COBE data as well as to recent ground-base CMB experiments.

  11. A novel 852-nm tunable fiber laser

    Yanlong Shen; Chun Gu; LixinXu; Anting Wang; Hai Ming; Yang Liu; Xiaobing Wang

    2009-01-01

    @@ We report a novel fiber laser operating at 850-nm band by using semiconductor optical amplifier and fiber grating.The laser system is stable, compact, and the operating wavelength can be tuned continuously from about 851 to 854 nm for Cs atomic clock system by stretching the fiber grating.An output power up to 20 mW is obtained with a signal-to-background ratio beyond 30 dB.

  12. Cascaded quadratic soliton compression at 800 nm

    Bache, Morten; Bang, Ole; Moses, Jeffrey;

    2007-01-01

    We study soliton compression in quadratic nonlinear materials at 800 nm, where group-velocity mismatch dominates. We develop a nonlocal theory showing that efficient compression depends strongly on characteristic nonlocal time scales related to pulse dispersion.......We study soliton compression in quadratic nonlinear materials at 800 nm, where group-velocity mismatch dominates. We develop a nonlocal theory showing that efficient compression depends strongly on characteristic nonlocal time scales related to pulse dispersion....

  13. [Application of Raman spectrometer (785 nm) to jadeite test].

    Fan, Jian-liang; Guo, Shou-guo; Liu, Xue-liang

    2007-10-01

    Jadeite is a greatly appreciated gemstone and often referred to as "the king of jade". Because of the advances in processing the treated jadeite is becoming more and more difficult for identification. NIR (785 nm) Raman spectrometer exhibits advantage of non-destruction, quickness, accurateness, and weak fluorescence interferences. This work reports such a research conducted using a NIR Raman spectrometer for a large number of jadeite samples. Based on the spectra collected and analysis there after performed, it is evident that the instrumentation and analysis methodology used have provided great information and assessment assistance in the application. It was found that the spectral response in the green area of a natural jadeite is much stronger in intensity than that in the white area. This is attributed to the key factor, the content of Cr3+ in the area. In contrast the spectral response in the green area of a treated jadeite is much weaker and additional Raman peaks start to show up on the high Raman shift side. This is the evidence of added fluorescence phenomenon and epoxyresin. It was also discovered that certain Raman features disappear compared to a natural sample. This indicates that the jadeite has been treated with acid and filled with colorless glue, which io turn destroyed the original exterior structure of a jadeite. PMID:18306795

  14. Spectral signature of short attosecond pulse trains

    Mansten, E; Mauritsson, J; Ruchon, T; LHuillier, A; Tate, J; Gaarde, M B; Eckle, P; Guandalini, A; Holler, M; Schapper, F; Gallmann, L; Keller, U

    2008-01-01

    We report experimental measurements of high-order harmonic spectra generated in Ar using a carrier-envelope-offset (CEO) stabilized 12 fs, 800nm laser field and a fraction (less than 10%) of its second harmonic. Additional spectral peaks are observed between the harmonic peaks, which are due to interferences between multiple pulses in the train. The position of these peaks varies with the CEO and their number is directly related to the number of pulses in the train. An analytical model, as well as numerical simulations, support our interpretation.

  15. Laser pulse transient method for measuring the normal spectral emissivity of samples with arbitrary surface quality

    Jeromen, Andrej; Grabec, Igor; Govekar, Edvard

    2015-01-01

    A laser pulse transient method for measuring normal spectral emissivity is described. In this method, a laser pulse (l=1064 nm) irradiates the top surface of a flat specimen. A two-dimensional temperature response of the bottom surface is measured with a calibrated thermographic camera. By solving an axisymmetric boundary value heat conduction problem, the normal spectral emissivity at 1064 nm is determined by using an iterative nonlinear least-squares estimation procedure. The method can be ...

  16. Spectral signature of Egyptian crude oils

    Crude petroleum oils are complex mixtures of diverse hydrocarbons, in widely varying compositions, that originate from a variety of geological sources. Fluorescence emission spectra have been measured for two types of Egyptian crude petroleum oil, its light and heavy products over a broad range of excitation and emission wavelengths. Both types of crude oil products are characterized by spectral signatures with a differing topography: the number of fluorescent peaks, their coordinates (λex, λem) on the plane of the three dimensions spectrum, and the shape of the bands formed by the contour line density, changeable in either direction. The refined light oil shows emission spectra at λmax between 350 and 500 nm according to the excitation wavelength. The refined heavy oil shows very broad unstructured emission spectra with λmax > 400 nm. As a group, they could certainly be distinguished from the light oil samples and most of the crude oil

  17. Liquid optical phantoms mimicking spectral characteristics of laboratory mouse biotissues

    Loginova, D. A.; Sergeeva, E. A.; Krainov, A. D.; Agrba, P. D.; Kirillin, M. Yu

    2016-06-01

    Optical phantoms mimicking optical properties of real biotissues in the visible and IR spectral regions are developed based on measurements of the spectral characteristics of ex vivo samples of laboratory mouse biotissues. The phantoms are composed of aqueous solutions of Lipofundin, Indian ink and red ink with different spectral characteristics. The deviations of the measured absorption and scattering coefficients of phantoms in the wavelength range 480 – 580 nm from the corresponding values for real biotissues do not exceed 25% and 2%, respectively. For phantoms in the wavelength region 580 – 880 nm, the deviations of the absorption coefficient do not exceed 40% and the deviations of the scattering coefficient do not exceed 25%. These values, in general, fall within the range of variations for different individual mice of one strain.

  18. SASE free electron lasers as short wavelength coherent sources. From first results at 100 nm to a 1 Å X-ray laser

    Treusch, R.; Feldhaus, J.

    2003-10-01

    During the last few years free electron lasers (FELs) based on self-amplified spontaneous emission (SASE) have been demonstrated at wavelengths of 12 μm [CITE], 830 nm [CITE], 530 nm [CITE] and 385 nm [CITE], and around 100 nm [CITE]. Recently, saturation has been observed in the vacuum ultraviolet (VUV) spectral region between 82 nm and 125 nm at the TESLA Test Facility (TTF) at DESY. The radiation pulses have been characterized with respect to pulse energy, statistical fluctuations, angular divergence and spectral distribution, both in the linear gain and in the saturation regime of the FEL [CITE]. The results are in good agreement with theoretical simulations, providing a solid basis for other projects aiming at still shorter wavelengths down to the 0.1 nm range [CITE].

  19. The use of hyperspectral imaging in the VNIR (400-1000nm) and SWIR range (1000-2500nm) for detecting counterfeit drugs with identical API composition.

    Wilczyński, Sławomir; Koprowski, Robert; Marmion, Mathieu; Duda, Piotr; Błońska-Fajfrowska, Barbara

    2016-11-01

    The risk of death from taking counterfeit drugs is now greater than the probability of dying from malaria and AIDS combined (at least half a million deaths each year). At the same time, counterfeit medicines are falsified more and more "skillfully". According to WHO about 10% of counterfeit drugs are copies of original products. The methods of hyperspectral imaging and image analysis and processing were used to detect counterfeit drugs. Original Viagra® (Pfizer) and counterfeit tablets were compared. Hyperspectral imaging was used to acquire hyperspectral data cubes from both original and counterfeit tablets in the spectral range of 400-2500nm. Spectral parameters for both the original Viagra® and counterfeit drugs were compared. Grey-Level Co-Occurrence Matrix (GLCM) analysis and Principal Component Analysis (PCA) were performed. Hyperspectral analysis of the surface of the original Viagra® and counterfeit tablets demonstrates significant differences in reflectance (maximum difference for 1619.75nm). The GLCM contrast for the falsified drug is on average higher than for the original one 16±4%. GLCM contrast analysis enables to quantify homogeneity of distribution of tablet ingredients and enables to distinguish tablets with identical chemical composition. SWIR (1000-2500nm) hyperspectral imaging has a definite advantage over imaging in VNIR (400-1000nm) - higher wavelength is less sensitive to non-uniform illumination. PMID:27591580

  20. The Double-ended 750 nm and 532 nm Laser Output from PPLN-FWM

    Wang, Tao; Li, Yu-Xiang; Yao, Jian-Quan; Guo, Ling; Wang, Zhuo; Han, Sha-Sha; Zhang, Cui-Ying; Zhong, Kai

    2013-06-01

    We investigate 750 nm and 532 nm dual-wavelength laser for applications in the internet of things. A kind of optical maser is developed, in which the semiconductor module outputs the 808 nm pump light and then it goes into a double-clad Nd3+ :YAG monocrystal optical fiber through the intermediate coupler and forms a 1064 nm laser. The laser outputs come from both left and right terminals. In the right branch, the laser goes into the right cycle polarization LinNbO3 (PPLN) crystal through the right coupler, produces the optical parametric oscillation and forms the signal light λ1 (1500 nm), the idle frequency light λ2 (3660.55 nm), and the second-harmonic of the signal light λ3 (750 nm). These three kinds of light and the pump light λ4 together form the frequency matching and the quasi-phase matching, then the four-wave mixing occurs to create the high-gain light at wavelength 750 nm. Meanwhile, in the left branch, the laser goes into the left PPLN crystal through the left coupler, engenders frequency doubling and forms the light at wavelength 532 nm. That is to say, the optical maser provides 750 nm and 532 nm dual-wavelength laser outputting from two terminals, which is workable.

  1. Effects of 946-nm thermal shift and broadening on Nd3+:YAG laser performance

    Seyed Ebrahim, Pourmand; Ghasem, Rezaei

    2015-12-01

    Spectroscopic properties of flashlamp pumped Nd3+:YAG laser are studied as a function of temperature in a range from -30 °C to 60 °C. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission within the respective intermanifold transitions of 4F3/2 → 4I9/2 are investigated. The 946.0-nm line shifts toward the shorter wavelength and broadens. In addition, the threshold power and slope efficiency of the 946.0-nm laser line are quantified with temperature. The lower the temperature, the lower the threshold power is and the higher the slope efficiency of the 946.0-nm laser line is, thus the higher the laser output is. This phenomenon is attributed to the ion-phonon interaction and the thermal population in the ground state. Project supported by Estahban Branch, Islamic Azad University.

  2. SPECTRAL CHARACTERISTICS OF SELECTED HERMATYPIC CORALS FROM GULF OF KACHCHH, INDIA

    N. Ray Chaudhury

    2012-07-01

    Full Text Available Hermatypic, scleractinian corals are the most important benthic substrates in a coral reef ecosystem. The existing, high (spatial resolution, broad-band, multi-spectral, space-borne sensors have limited capability to spatially detect and spectrally discriminate coral substrates. In situ hyperspectral signatures of eight coral targets were collected with the help of Analytical Spectral Devices FieldSpec spectroradiometer from Paga and Laku Point reefs of Gulf of Kachchh, India to study the spectral behaviour of corals. The eight coral targets consisted of seven live corals representing four distinct colony morphologies and one bleached coral target. The coral spectra were studied over a continuous range of 350 to 1350 nm. The corals strongly reflected in the NIR and MIR regions with regional central maximas located at 820 and 1070 nm respectively. In the visible region the live coral spectra conformed to "brown mode" of coral reflectance with triple-peaked pattern at 575, 600 and 650 nm. All coral spectra are characterized with two distinct absorption features: chlorophyll absorption at 675 nm and water absorption at 975 nm. The live and the bleached corals get distinguished in the visible region over 400 to 600 nm region. Water column over the targets modifies the spectral shape and magnitude. First and second-order derivatives help in identifying spectral windows to distinguish live and bleached corals.

  3. Retinal Oximetry with 510-600 nm Light Based on Partial Least-Squares Regression Technique

    Arimoto, Hidenobu; Furukawa, Hiromitsu

    2010-11-01

    The oxygen saturation distribution in the retinal blood stream is estimated by measuring spectral images and adopting the partial-least squares regression. The wavelengths range used for the calculation is from 510 to 600 nm. The regression model for estimating the retinal oxygen saturation is built on the basis of the arterial and venous blood spectra. The experiment is performed using an originally designed spectral ophthalmoscope. The obtained two-dimensional (2D) oxygen saturation indicates the reasonable oxygen level across the retina. The measurement quality is compared with those obtained using other wavelengths sets and data processing methods.

  4. Spectral Expansion for the Asymptotically Spectral Periodic Differential Operators

    O. A. Veliev

    2016-01-01

    In this paper we investigate the spectral expansion for the asymptotically spectral differential operators generated in all real line by ordinary differential expression of arbitrary order with periodic matrix-valued coefficients

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

    Attila Nagy

    2014-08-01

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

  6. Fiber delivered two-color picosecond source through nonlinear spectral transformation for coherent Raman scattering imaging

    Wang, Ke; Xu, Chris

    2012-01-01

    We demonstrate a two-color, fiber-delivered picosecond source for coherent Raman scattering (CRS) imaging through nonlinear spectral transformation. The wavelength tunable picosecond pump is generated by nonlinear spectral compression of a prechirped femtosecond pulse in a fiber wavelength division multiplexer (WDM). The 1064-nm synchronized picosecond Stokes pulse is generated through pulse carving of a continuous wave laser, nonlinear spectral broadening in 100-m standard single-mode fiber,...

  7. Miniaturized spectral imager for Aalto-1 nanosatellite

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

    2011-11-01

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

  8. 810nm, 980nm, 1470nm and 1950nm diode laser comparison: a preliminary "ex vivo" study on oral soft tissues

    Fornaini, Carlo; Merigo, Elisabetta; Sozzi, Michele; Selleri, Stefano; Vescovi, Paolo; Cucinotta, Annamaria

    2015-02-01

    The introduction of diode lasers in dentistry has several advantages, mainly consisting on the reduced size, reduced cost and possibility to beam delivering by optical fibers. At the moment the two diode wavelengths normally utilized in the dental field are 810 and 980 nm for soft tissues treatments. The aim of this study was to compare the efficacy of four different diode wavelengths: 810, 980, 1470 and 1950 nm diode laser for the ablation of soft tissues. Several samples of veal tongue were exposed to the four different wavelengths, at different fluences. The internal temperature of the soft tissues, in the area close to the beam, was monitored with thermocouple during the experiment. The excision quality of the exposed samples have been characterized by means of an optical microscope. Tissue damages and the cut regularity have been evaluated on the base of established criteria. The lowest thermal increase was recorded for 1950 nm laser. Best quality and speed of incision were obtained by the same wavelength. By evaluating epithelial, stromal and vascular damages for all the used wavelengths, the best result, in terms of "tissue respect", have been obtained for 1470 and 1950 nm exposures. From the obtained results 1470 and 1950 nm diode laser showed to be the best performer wavelengths among these used in this "ex vivo" study, probably due to their greatest affinity to water.

  9. Spectrally tunable pixel sensors

    Langfelder, G.; Buffa, C.; Longoni, A. F.; Zaraga, F.

    2013-01-01

    They are here reported the developments and experimental results of fully operating matrices of spectrally tunable pixels based on the Transverse Field Detector (TFD). Unlike several digital imaging sensors based on color filter arrays or layered junctions, the TFD has the peculiar feature of having electrically tunable spectral sensitivities. In this way the sensor color space is not fixed a priori but can be real-time adjusted, e.g. for a better adaptation to the scene content or for multispectral capture. These advantages come at the cost of an increased complexity both for the photosensitive elements and for the readout electronics. The challenges in the realization of a matrix of TFD pixels are analyzed in this work. First experimental results on an 8x8 (x 3 colors) and on a 64x64 (x 3 colors) matrix will be presented and analyzed in terms of colorimetric and noise performance, and compared to simulation predictions.

  10. Quantitative Stellar Spectral Classification

    Jurgen Stock; María Jeanette Stock

    2001-01-01

    Equivalent widths of 19 absorption lines in CCD slit spectra of 490 stars are compared with their respective (B-V) colors and their absolute magnitudes derived from Hipparcos parallaxes. Algorithms are found which yield the absolut e magnitudes for all spectral types with an average error of 0.26 magnitudes. The (B-V) colors can be reproduced with an average error of 0.020 magnitues.

  11. Spectral correlates lexical prosody

    Okobi, Anthony

    2005-09-01

    The purpose of this study is to derive a quantitative acoustic model of lexical-prosodic characteristics of stressed vowels by looking at several spectral properties associated with the articulatory mechanisms used in speech production. Native speakers of American English were asked to name disyllabic visualizable nouns. Words containing liquids or glides were not used in this study because of their effect on the spectra of adjacent vowels. Subjects uttered short phrases in which the target word was pitch accent half of the time and unaccented the other half. Results show that within the category of full vowels, unstressed and stressed vowels can be distinguished by syllable/vowel durations and spectral tilt. Spectral tilt (SpT) is an acoustic measure related to the degree of glottal spreading. Stressed full vowels had longer duration and less SpT. Distinction between unaccented and accented stressed vowels can be made by amplitude of voicing (AV), F0 (pitch), and intensity contour differences. Accented stressed vowels have higher pitch, and greater AV and intensity. These results suggest that there are acoustic correlates to lexical stress that can be used to determine the stressed syllable of a word, regardless of whether or not it is pitch accented. [Work supported by NIH T32-DC00038.

  12. Diode laser (980nm) cartilage reshaping

    El Kharbotly, A.; El Tayeb, T.; Mostafa, Y.; Hesham, I.

    2011-03-01

    Loss of facial or ear cartilage due to trauma or surgery is a major challenge to the otolaryngologists and plastic surgeons as the complicated geometric contours are difficult to be animated. Diode laser (980 nm) has been proven effective in reshaping and maintaining the new geometric shape achieved by laser. This study focused on determining the optimum laser parameters needed for cartilage reshaping with a controlled water cooling system. Harvested animal cartilages were angulated with different degrees and irradiated with different diode laser powers (980nm, 4x8mm spot size). The cartilage specimens were maintained in a deformation angle for two hours after irradiation then released for another two hours. They were serially measured and photographed. High-power Diode laser irradiation with water cooling is a cheep and effective method for reshaping the cartilage needed for reconstruction of difficult situations in otorhinolaryngologic surgery. Key words: cartilage,diode laser (980nm), reshaping.

  13. Design of an 1800nm Raman amplifier

    Svane, Ask Sebastian; Rottwitt, Karsten

    2013-01-01

    We present the experimental results for a Raman amplifier that operates at 1810 nm and is pumped by a Raman fiber laser at 1680 nm. Both the pump laser and the Raman amplifier is polarization maintaining. A challenge when scaling Raman amplifiers to longer wavelengths is the increase in...... transmission loss, but also the reduction in the Raman gain coefficient as the amplifier wavelength is increased. Both polarization components of the Raman gain is characterized, initially for linearly co-polarized signal and pump, subsequently linearly polarized orthogonal signal and pump. The noise...... performance of the amplifier is also investigated for both configurations. Our results show an on/off gain exceeding 20 dB at 1810 nm for which the obtained effective noise figure is below 3 dB....

  14. Monolithic 626 nm single-mode AlGaInP DBR diode laser.

    Blume, G; Nedow, O; Feise, D; Pohl, J; Paschke, K

    2013-09-01

    Single-mode lasers below 630 nm are still realized using complex laser systems. We present distributed Bragg reflector (DBR) ridge waveguide lasers (RWL) based on AlGaInP. When packaged into sealed TO-3 housings and cooled internally to about 0°C the DBR-RWL emit more than 50 mW at a wavelength of 626.0 nm into a nearly diffraction-limited single longitudinal mode with a spectral width below 1 MHz. These new monolithic diode lasers have the potential to drastically miniaturize existing set-ups e.g. for quantum information processing. PMID:24104041

  15. Highly reliable high-efficiency wavelength-stabilized 885 nm diode laser bars

    Leisher, Paul; Bao, Ling; Huang, Hua; Wang, Jun; DeVito, Mark; Dong, Weimin; Grimshaw, Mike; Balsley, David; Martinsen, Rob; DeFranza, Mark; Patterson, Steve

    2009-05-01

    We report on the progress of highly-reliable, high-efficiency 885-nm diode laser bar arrays. Conduction-cooled hardsoldered bars rated to 60W and 57% conversion efficiency demonstrate >30,000 device hours under 1-sec on, 1-sec off hard pulse conditions failure-free. Microchannel-cooled bars rated to 100W and 62% efficiency demonstrate >100,000 accelerated device hours failure-free. Integrated volume Bragg grating fast axis lenses provide wavelength stabilization at low cost. Vertically stacked arrays (seven bars each) of such configuration are demonstrated with a 0.8 nm FWHM spectral width and rated to 700W, 53% conversion efficiency.

  16. Liquid Carbon Reflectivity at 19 nm

    Riccardo Mincigrucci

    2015-01-01

    Full Text Available We hereby report on a pump-probe reflectivity experiment conducted on amorphous carbon, using a 780 nm laser as a pump and a 19 nm FEL emission as probe. Measurements were performed at 50 degrees with respect to the surface normal to have an un-pumped reflectivity higher than 0.5%. A sub-10 fs time synchronization error could be obtained exploiting the nearly jitter-free capabilities of FERMI. EUV FEL-based experiments open the way to study the behaviour of a liquid carbon phase being unaffected by plasma screening.

  17. SWOC: Spectral Wavelength Optimization Code

    Ruchti, G. R.

    2016-06-01

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

  18. Spectral Measures on Locally Fields

    Fan, Ai Hua

    2015-01-01

    In this paper, we propose to study spectral measures on local fields. Some basic results are presented, including the stability of Bessel sequences under perturbation, the Landau theorem on Beurling density, the law of pure type of spectral measures, the boundedness of the Radon-Nikodym derivative of absolutely continuous $F$-spectral measures etc.

  19. Wavelength conversion based spectral imaging

    Dam, Jeppe Seidelin

    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...

  20. Nuclear spectrometry and spectral interpretation

    The performance of various spectrometric detectors is summarized and methods of spectral analysis described. Sections include instrumentation, differential pulse height analysis, energy resolution and the width of spectral peaks, proportional counters (operating characteristics and application to mineral analysis), solid state detectors and spectral peak analysis

  1. High power resonantly diode-pumped σ-configuration Er3+:YVO4 laser at 1593.5 nm

    Ter-Gabrielyan, N.; Fromzel, V.; Lukasiewicz, T.; Ryba-Romanowski, W.; Dubinskii, M.

    2011-07-01

    Laser operation of an eyesafe 1593.5-nm laser based on Er3+-doped yttrium orthovanadate single crystal resonantly-pumped by a spectrally-narrowed InGaAsP/InP diode bar stack is demonstrated for the first time. Cryogenically-cooled Er3+:YVO4 laser pumped at 1534 nm performed with maximum slope efficiency of ~ 70% and maximum quasi-continuous-wave (Q-CW) power of 59.8 W.

  2. High power resonantly diode-pumped σ-configuration Er3+:YVO4 laser at 1593.5 nm

    Laser operation of an eyesafe 1593.5-nm laser based on Er3+-doped yttrium orthovanadate single crystal resonantly-pumped by a spectrally-narrowed InGaAsP/InP diode bar stack is demonstrated for the first time. Cryogenically-cooled Er3+:YVO4 laser pumped at 1534 nm performed with maximum slope efficiency of ∼ 70% and maximum quasi-continuous-wave (Q-CW) power of 59.8 W

  3. Temperature- and pressure-dependent absorption coefficients for CO2 and O2 at 193 nm

    Hartinger, K. T.; Nord, S.; Monkhouse, P. B.

    Absorption of laser radiation at 193 nm by CO2 and O2 was studied at a series of different temperatures up to 1273 K and pressures up to 1 bar. The spectrum for CO2 was found to be broadband, so that absorption could be fitted to a Beer-Lambert law. On the other hand, the corresponding O2 spectrum is strongly structured and parameterisation requires a more complex relation, depending on both temperature and the product (pressure × absorption path length). In this context, the influence of spectral structure on the resulting spectrally integrated absorption coefficients is discussed. Using the fitting parameters obtained, effective transmissions at 193 nm can be calculated for a wide range of experimental conditions. As an illustration of the practical application of these data, the calculation of effective transmission for a typical industrial flue gas is described.

  4. Visible supercontinuum generation in a graded index multimode fiber pumped at 1064  nm.

    Lopez-Galmiche, G; Sanjabi Eznaveh, Z; Eftekhar, M A; Antonio Lopez, J; Wright, L G; Wise, F; Christodoulides, D; Amezcua Correa, R

    2016-06-01

    We observe efficient supercontinuum generation that extends into the visible spectral range by pumping a low differential mode group delay graded index multimode fiber in the normal dispersion regime. For a 28.5 m long fiber, the generated spectrum spans more than two octaves, starting from below 450 nm and extending beyond 2400 nm. The main nonlinear mechanisms contributing to the visible spectrum generation are attributed to multipath four-wave mixing processes and periodic spatio-temporal breathing dynamics. Moreover, by exploiting the highly multimodal nature of this system, we demonstrate versatile generation of visible spectral peaks in shorter fiber spans by altering the launching conditions. A nonlinearly induced mode cleanup was also observed at the pump wavelength. Our results could pave the way for high brightness, high power, and compact, multi-octave continuum sources. PMID:27244412

  5. Spectral identification of lighting type and character.

    Elvidge, Christopher D; Keith, David M; Tuttle, Benjamin T; Baugh, Kimberly E

    2010-01-01

    We investigated the optimal spectral bands for the identification of lighting types and the estimation of four major indices used to measure the efficiency or character of lighting. To accomplish these objectives we collected high-resolution emission spectra (350 to 2,500 nm) for forty-three different lamps, encompassing nine of the major types of lamps used worldwide. The narrow band emission spectra were used to simulate radiances in eight spectral bands including the human eye photoreceptor bands (photopic, scotopic, and "meltopic") plus five spectral bands in the visible and near-infrared modeled on bands flown on the Landsat Thematic Mapper (TM). The high-resolution continuous spectra are superior to the broad band combinations for the identification of lighting type and are the standard for calculation of Luminous Efficacy of Radiation (LER), Correlated Color Temperature (CCT) and Color Rendering Index (CRI). Given the high cost that would be associated with building and flying a hyperspectral sensor with detection limits low enough to observe nighttime lights we conclude that it would be more feasible to fly an instrument with a limited number of broad spectral bands in the visible to near infrared. The best set of broad spectral bands among those tested is blue, green, red and NIR bands modeled on the band set flown on the Landsat Thematic Mapper. This set provides low errors on the identification of lighting types and reasonable estimates of LER and CCT when compared to the other broad band set tested. None of the broad band sets tested could make reasonable estimates of Luminous Efficacy (LE) or CRI. The photopic band proved useful for the estimation of LER. However, the three photoreceptor bands performed poorly in the identification of lighting types when compared to the bands modeled on the Landsat Thematic Mapper. Our conclusion is that it is feasible to identify lighting type and make reasonable estimates of LER and CCT using four or more spectral

  6. Spectral Identification of Lighting Type and Character

    Christopher D. Elvidge

    2010-04-01

    Full Text Available We investigated the optimal spectral bands for the identification of lighting types and the estimation of four major indices used to measure the efficiency or character of lighting. To accomplish these objectives we collected high-resolution emission spectra (350 to 2,500 nm for forty-three different lamps, encompassing nine of the major types of lamps used worldwide. The narrow band emission spectra were used to simulate radiances in eight spectral bands including the human eye photoreceptor bands (photopic, scotopic, and “meltopic” plus five spectral bands in the visible and near-infrared modeled on bands flown on the Landsat Thematic Mapper (TM. The high-resolution continuous spectra are superior to the broad band combinations for the identification of lighting type and are the standard for calculation of Luminous Efficacy of Radiation (LER, Correlated Color Temperature (CCT and Color Rendering Index (CRI. Given the high cost that would be associated with building and flying a hyperspectral sensor with detection limits low enough to observe nighttime lights we conclude that it would be more feasible to fly an instrument with a limited number of broad spectral bands in the visible to near infrared. The best set of broad spectral bands among those tested is blue, green, red and NIR bands modeled on the band set flown on the Landsat Thematic Mapper. This set provides low errors on the identification of lighting types and reasonable estimates of LER and CCT when compared to the other broad band set tested. None of the broad band sets tested could make reasonable estimates of Luminous Efficacy (LE or CRI. The photopic band proved useful for the estimation of LER. However, the three photoreceptor bands performed poorly in the identification of lighting types when compared to the bands modeled on the Landsat Thematic Mapper. Our conclusion is that it is feasible to identify lighting type and make reasonable estimates of LER and CCT using four or

  7. The Advanced Spectral Library (ASTRAL) Project

    Ayres, Thomas R.; The ASTRAL I & Science Teams, II

    2014-01-01

    The Advanced Spectral Library (ASTRAL) is an HST Treasury Program whose aim is to secure definitive ultraviolet (115-310 nm) spectra of representative bright stars utilizing the venerable -- yet still state-of-the-art -- Space Telescope Imaging Spectrograph (STIS). The initial Cycle 18 installment of the program (146 orbits in 2010-2011) focused on late-type (``cool’’) stars, acquiring high-S/N, high spectral resolution measurements of eight pivotal targets, including iconic objects like Betelgeuse and Procyon. The latest episode, in current Cycle 21 (230 orbits in 2013-2014), is designed to record very high-S/N (>100) STIS echellegrams, at the highest resolution feasible ( 30,000-100,000), of 21 representative bright early-type (``hot’’) stars, including equally iconic objects like Vega, Sirius, Regulus, and Zeta Puppis. The targets span a broad range of spectral types between early-O and early-A, encompassing main sequence and evolved stars, fast and slow rotators, as well as chemically peculiar and magnetic objects. These high-quality STIS UV spectra will be publicly available immediately after observation from the HST archive; and, in post-processed and merged form, at the project website: http://casa.colorado.edu ayres/ASTRAL/. The UV "atlases" produced by the ASTRAL Program will enable investigations of a broad range of astrophysical problems -- stellar, interstellar, and beyond -- for many years to come. Supported by Guest Observer grants from STScI.

  8. Recubrimientos ópticos en el rango espectral entre 50 y 200 nm

    Fernández Perea, Mónica; Méndez, José Antonio; Larruquert, Juan Ignacio; Aznárez, José Antonio

    2006-01-01

    The development of efficient optical coatings in the spectral region between 50 and 200 nm (EUV-FUV) is an important challenge due to the great absortion and low reflectance that most of the materials present in this region. In addition, these coatings are an important element in the advance of many fields like astronomical abservations, plasma diagnosis and lithography. In this work we describe some of the optical coatings developed by the Research Group in Thin Film Coatings (GOLD), whic...

  9. Spectral beam combining of multi-single emitters

    Wang, Baohua; Guo, Weirong; Guo, Zhijie; Xu, Dan; Zhu, Jing; Zhang, Qiang; Yang, Thomas; Chen, Xiaohua

    2016-03-01

    Spectral beam combination expands the output power while keeps the beam quality of the combined beam almost the same as that of a single emitter. Spectral beam combination has been successfully achieved for high power fiber lasers, diode laser arrays and diode laser stacks. We have recently achieved the spectral beam combination of multiple single emitter diode lasers. Spatial beam combination and beam transformation are employed before beams from 25 single emitter diode lasers can be spectrally combined. An average output power about 220W, a spectral bandwidth less than 9 nm (95% energy), a beam quality similar to that of a single emitter and electro-optical conversion efficiency over 46% are achieved. In this paper, Rigorous Coupled Wave analysis is used to numerically evaluate the influence of emitter width, emitter pitch and focal length of transform lens on diffraction efficiency of the grating and spectral bandwidth. To assess the chance of catastrophic optical mirror damage (COMD), the optical power in the internal cavity of a free running emitter and the optical power in the grating external cavity of a wavelength locked emitter are theoretically analyzed. Advantages and disadvantages of spectral beam combination are concluded.

  10. Spectral Light Measurements in Microbenthic Phototrophic Communities with a Fiberoptic Microprobe Coupled to a Sensitive Diode-Array Detector Rid A-1977-2009

    KUHL, M.; JØRGENSEN, BB

    1992-01-01

    coupled to the detector system and used for spectral light measurements in hypersaline microbial mats and in laminated phototrophic communities of coastal sediments. The vertical distribution of major photopigments of microalgae, cyanobacteria, and anoxygenic phototrophic bacteria could be identified from...... extinction maxima in measured radiance spectra at 430-550 nm (Chl a and carotenoids), 620-625 nm (phycocyanin), 675 nm (Chl a), 745-750 nm (BChl c), 800-810 nm, and 860-880 nm (BChl a). Scalar irradiance spectra exhibited a different spectral composition and a higher light intensity at the sediment surface...

  11. Spectral Variability of FSRQs

    Minfeng Gu; Y. L. Ai

    2011-03-01

    The optical variability of 29 flat spectrum radio quasars in SDSS Stripe 82 region are investigated by using DR7 released multi-epoch data. All FSRQs show variations with overall amplitude ranging from 0.24 mag to 3.46 mag in different sources. About half of FSRQs show a bluer-when-brighter trend, which is commonly observed for blazars. However, only one source shows a redder-when-brighter trend, which implies it is rare in FSRQs. In this source, the thermal emission may be responsible for the spectral behaviour.

  12. Harmonic and spectral analysis

    Székelyhidi, László

    2014-01-01

    This book provides a modern introduction to harmonic analysis and synthesis on topological groups. It serves as a guide to the abstract theory of Fourier transformation. For the first time, it presents a detailed account of the theory of classical harmonic analysis together with the recent developments in spectral analysis and synthesis. Sample Chapter(s)Chapter 1: Duality of Finite Abelian Groups (254 KB) Contents:Abstract Harmonic Analysis:Duality of Finite Abelian GroupsHarmonic Analysis on Finite Abelian GroupsSet

  13. Shock-Accelerated Flying Foil Diagnostic with a Chirped Pulse Spectral Interferometry

    陈建平; 李儒新; 曾志男; 王兴涛; 程传福; 徐至展

    2003-01-01

    A shock-accelerated flying foil is diagnosed with a chirped pulse spectral interferometry. The shock is pumped by a 1.2ps chirped laser pulse with a power of~1014 W/cm2 at 785nm irradiating on a 500nm aluminium film and detected by a probe pulse split from the pump based on a Michelson spectral interferometry. A flying foil of~5.595×10-6 g in~400 μm diameter was accelerated to~165 nm away from the initial target rear surface at~1.83 km/s before ablation.

  14. Laser and pinching discharge plasmas spectral characteristics in water window region 2

    Kolar, Petr; Vrbova, Miroslava; Nevrkla, Michal; Vrba, Pavel; Jancarek, Alexandr

    2011-01-01

    Water window emission spectra of two laboratory nitrogen plasma sources were examined with a free standing grating spectrometer (FSGS). The highest line intensities at the wavelength 2.88 nm achievable with the sources were compared. Pulse energies for this line were judged as 0.02 mJ/srad and 0.16 mJ/srad with laser produced plasma system and pinching discharge plasma, respectively. The spectral resolution was found about 0.01 nm at 3rd order of spectral lines around wavelength 2.5 nm.

  15. Repair of near-UV (365nm or 313 nm) induced DNA strand breaks

    The action of near-UV (365 nm or 313 nm) radiation in cellular inactivaton (biological measurements) and induction and repair of breaks (physical measurements) is studied in repair proficient strain and in pol A, rec A and uvr A deficient strains of Escherichia coli K-12. (M.A.C.)

  16. Rapid microscopy measurement of very large spectral images.

    Lindner, Moshe; Shotan, Zav; Garini, Yuval

    2016-05-01

    The spectral content of a sample provides important information that cannot be detected by the human eye or by using an ordinary RGB camera. The spectrum is typically a fingerprint of the chemical compound, its environmental conditions, phase and geometry. Thus measuring the spectrum at each point of a sample is important for a large range of applications from art preservation through forensics to pathological analysis of a tissue section. To date, however, there is no system that can measure the spectral image of a large sample in a reasonable time. Here we present a novel method for scanning very large spectral images of microscopy samples even if they cannot be viewed in a single field of view of the camera. The system is based on capturing information while the sample is being scanned continuously 'on the fly'. Spectral separation implements Fourier spectroscopy by using an interferometer mounted along the optical axis. High spectral resolution of ~5 nm at 500 nm could be achieved with a diffraction-limited spatial resolution. The acquisition time is fairly high and takes 6-8 minutes for a sample size of 10mm x 10mm measured under a bright-field microscope using a 20X magnification. PMID:27137565

  17. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10‑3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10‑27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  18. Visual pigments and spectral sensitivity of the diurnal gecko Gonatodes albogularis.

    Ellingson, J M; Fleishman, L J; Loew, E R

    1995-11-01

    The visual pigments and oil droplets in the retina of the diurnal gecko Gonatodes albogularis were examined microspectrophotometrically, and the spectral sensitivity under various adapting conditions was recorded using electrophysiological responses. Three classes of visual pigments were identified, with lambda max at about 542, 475, and 362 nm. Spectral sensitivity functions revealed a broad range of sensitivity, with a peak at approximately 530-540 nm. The cornea and oil droplets were found to be transparent across a range from 350-700 nm, but the lens absorbed short wavelength light below 450 nm. Despite the filtering effect of the lens, a secondary peak in spectral sensitivity to ultraviolet wavelengths was found. These results suggest that G. albogularis does possess the visual mechanisms for discrimination of the color pattern of conspecifics based on either hue or brightness. These findings are discussed in terms of the variation in coloration and social behavior of Gonatodes. PMID:7473305

  19. Photochemistry of Acrylates at 222 nm

    Excimer lamps as monochromatic UV sources with an intense short wavelength mission (specially Kr Cl, 222 nm) allow a photo initiator-free initiation of the acrylate polymerisation. Laser photolysis (Kr Cl excimer laser, pulse width 20 ns, up to 5 ml per pulse) gives rise to similar transient spectra (max << 280 nm) for all acrylates studied. As the rather unspecific spectra do not allow conclusions as to the main reaction channel, a product study has been performed by GC-MS following steady-state photolysis of acrylate solutions in acetonitrile, methanol and n-hexane. Somewhat unexpected, a-cleavage seems to be a main reaction channel, and quantum chemical calculations show that such a reaction can occur from either the excited singlet state or the un relaxed triplet state, but not from the relaxed triplet state that is observed spectroscopically. A reaction scheme accounting for the observed products is presented

  20. The Effects of Water Vapor and Clouds on the Spectral Distribution of Solar Radiation at the...

    Pilewskie, P.; Bergstrom, R.; Mariani, P.; Gore, Warren J. Y. (Technical Monitor)

    1997-01-01

    During the Subsonic Contrail and Cloud Effect Special Study (SUCCESS) a Solar Spectral Flux Radiometer was deployed at the surface in a zenith observing position. The instrument measured the solar spectral downwelling irradiance between 350 and 2500 nm with 10 nm resolution. From April 12 through April 29 approximately 18000 spectra were acquired, under a variety of meteorological conditions including cloud free, cirrus, Stearns, and cumulonimbus clouds. This study focuses on the effect of cirrus and cirrus contrails on the spectral distribution of solar irradiance at the surface and on inferring cirrus properties from their spectral transmittance. The observations have also proven to be useful for comparing the solar spectral irradiance measurements with model predictions, and in particular, for inferring the amount of solar radiation absorbed in the clear and cloudy atmosphere.

  1. Theoretical investigation on degradation behaviors of spectral properties of thermal control coatings induced by charged particles

    The degradation of spectral properties of thermal control coatings on spacecrafts is investigated in this paper. By studying their physical components and geometry structure, the factors which determine the spectral properties of the coatings are founded. A theoretical model for calculating the spectral absorptance of coatings is proposed based on the Mie's theory and Stratified Media theory. Mathematical expressions are introduced for accounting for the effect of the complicated environment. Based on these work, a predicting model for the degradation of spectral absorptance properties of the coatings is established. To validate this model, the predicted degradation performance of spectral properties of zinc oxide based coatings under electrons and protons exposure are compared with the experimental data. A good agreement is found at the wavelength between 250 nm and 2500 nm. Finally, a useful approach for predicting the degradation behaviors of thermal control coatings on spacecrafts in orbit is established.

  2. Double-pulse laser ablation sampling: Enhancement of analyte emission by a second laser pulse at 213 nm

    For the purpose of devising methods for minimally destructive multi-element analysis, we compare the performance of a 266 nm–213 nm double-pulse scheme against that of the single 266 nm pulse scheme. The first laser pulse at 266 nm ablates a mica sample. Ten ns later, the second pulse at 213 nm and 64 mJ cm−2 orthogonally intercepts the gas plume to enhance the analyte signal. Emissions from aluminum, silicon, magnesium and sodium are simultaneously observed. At low 266 nm laser fluence when only sub-ng of sample mass is removed, the signal enhancement by the 213 nm pulse is especially apparent. The minimum detectable amount of aluminum is about 24 fmol; it will be a hundred times higher if the sample is analyzed by the 266 nm pulse alone. The minimum detectable mass for the other analytes is also reduced by about two orders of magnitude when the second pulse at 213 nm is introduced. The spectral and temporal properties of the enhanced signal are consistent with the mechanism of ultra-violet laser excited atomic fluorescence of dense plumes. - Highlights: • We devise a two-laser-pulse scheme to analyze the elemental composition of mica as test samples. • We compare the analytical performance of the single 266 nm pulse scheme against the 266 nm – 213 nm two pulse scheme. • The two pulse scheme improves the absolute LODs of the analytes by about a hundred times. • The spectral and temporal properties of the enhanced signal are consistent with the mechanism

  3. Double-pulse laser ablation sampling: Enhancement of analyte emission by a second laser pulse at 213 nm

    Cai, Bruno Yue [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong (China); Mao, Xianglei [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Hou, Huaming [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Ocean University of China, Qingdao (China); Zorba, Vassilia; Russo, Richard E. [Laser Technologies Group, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Cheung, Nai-Ho, E-mail: nhcheung@hkbu.edu.hk [Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong (China)

    2015-08-01

    For the purpose of devising methods for minimally destructive multi-element analysis, we compare the performance of a 266 nm–213 nm double-pulse scheme against that of the single 266 nm pulse scheme. The first laser pulse at 266 nm ablates a mica sample. Ten ns later, the second pulse at 213 nm and 64 mJ cm{sup −2} orthogonally intercepts the gas plume to enhance the analyte signal. Emissions from aluminum, silicon, magnesium and sodium are simultaneously observed. At low 266 nm laser fluence when only sub-ng of sample mass is removed, the signal enhancement by the 213 nm pulse is especially apparent. The minimum detectable amount of aluminum is about 24 fmol; it will be a hundred times higher if the sample is analyzed by the 266 nm pulse alone. The minimum detectable mass for the other analytes is also reduced by about two orders of magnitude when the second pulse at 213 nm is introduced. The spectral and temporal properties of the enhanced signal are consistent with the mechanism of ultra-violet laser excited atomic fluorescence of dense plumes. - Highlights: • We devise a two-laser-pulse scheme to analyze the elemental composition of mica as test samples. • We compare the analytical performance of the single 266 nm pulse scheme against the 266 nm – 213 nm two pulse scheme. • The two pulse scheme improves the absolute LODs of the analytes by about a hundred times. • The spectral and temporal properties of the enhanced signal are consistent with the mechanism.

  4. DNA Charge Transport over 34 nm

    Slinker, Jason D.; Muren, Natalie B.; Renfrew, Sara E.; Barton, Jacqueline K.

    2011-01-01

    Molecular wires show promise in nanoscale electronics but the synthesis of uniform, long conductive molecules is a significant challenge. DNA of precise length, by contrast, is easily synthesized, but its conductivity has not been explored over the distances required for nanoscale devices. Here we demonstrate DNA charge transport (CT) over 34 nm in 100-mer monolayers on gold. Multiplexed gold electrodes modified with 100-mer DNA yield sizable electrochemical signals from a distal, covalent Ni...

  5. Laser induced fluorescence (LIF) of Hg2 and Hg3 via dissociation of HgBr2 at 157 nm

    Skordoulis, C.; Sarantopoulou, E.; Spyrou, S. M.; Kosmidis, C.; Cefalas, A. C.

    1991-06-01

    Laser induced fluorescence of the mercury clusters Hg2 and Hg3 in the spectral range between 300 nm to 510 nm has been obtained from the dissociation of HgBr2 at 7.88 eV (157.5 nm) with an F2 molecular laser, together with fluorescence from mercury atomic transitions from highly excited states. The excitation process involves two photon absorption which dissociates the molecule at 15.76 eV total photon energy with the subsequent formation of the metallic clusters.

  6. Laser induced fluorescence (LIF) of Hg2 and Hg3 via dissociation of HgBr2 at 157 nm

    Laser induced fluorescence of the mercury clusters Hg2 and Hg3 in the spectral range between 300 nm to 510 nm has been obtained from the dissociation of HgBr2 at 7.88 eV (157.5 nm) with an F2 molecular laser, together with fluorescence from mercury atomic transitions from highly excited states. The excitation process involves two photon absorption which dissociates the molecule at 15.76 eV total photon energy with the subsequent formation of the metallic clusters. (orig.)

  7. 500 nm Continuous Wave Tunable SingleFrequency MidIR Light Source for C–H Spectroscopy

    Høgstedt, Lasse; Jensen, Ole Bjarlin; Dam, Jeppe Seidelin; Pedersen, Christian; Tidemand-Lichtenberg, Peter

    2012-01-01

    A computer controlled tunable mid-IR light source, based on single resonant difference frequency generation (DFG), is experimentally investigated. The DFG process is pumped by an external cavity tapered diode laser, tunable over a spectral range of 30 nm. Grating feedback to the single mode channel...... of the tapered diode narrows the spectrum and allows for tuning of the emitted spectrum in the range from 780 to 810 nm. The DFG process takes place intra-cavity in a high finesse diode pumped 1064 nm solid state Nd:YVO4 laser cavity, using periodically poled LiNbO3 as the nonlinear material. Based...

  8. The Effect of Epidermal Structures on Leaf Spectral Signatures of Ice Plants (Aizoaceae

    René Hans-Jürgen Heim

    2015-12-01

    Full Text Available Epidermal structures (ES of leaves are known to affect the functional properties and spectral responses. Spectral studies focused mostly on the effect of hairs or wax layers only. We studied a wider range of different ES and their impact on spectral properties. Additionally, we identified spectral regions that allow distinguishing different ES. We used a field spectrometer to measure ex situ leaf spectral responses from 350 nm–2500 nm. A spectral library for 25 species of the succulent family Aizoaceae was assembled. Five functional types were defined based on ES: flat epidermal cell surface, convex to papillary epidermal cell surface, bladder cells, hairs and wax cover. We tested the separability of ES using partial least squares discriminant analysis (PLS-DA based on the spectral data. Subsequently, variable importance (VIP was calculated to identify spectral regions relevant for discriminating our functional types (classes. Classification performance was high, with a kappa value of 0.9 indicating well-separable spectral classes. VIP calculations identified six spectral regions of increased importance for the classification. We confirmed and extended previous findings regarding the visible-near-infrared spectral region. Our experiments also confirmed that epidermal leaf traits can be classified due to clearly distinguishable spectral signatures across species and genera within the Aizoaceae.

  9. Lasing at 300 nm and below: Optical challenges and perspectives

    Garzella, D. [Universite de Paris-Sud, Orsay (France); Couprie, M.E. [Universite de Paris-Sud, Orsay (France)]|[CEA DSM DRECAM SPAM, Gif Sur Yvette (France); Billardon, M. [ESPCI, Paris (France)

    1995-12-31

    The FEL experiment in the visible and near UV on the Super ACO storage ring has given, since 1989, important informations on the SRFEL dynamics and, furthermore, a very good beam stability has been achieved. In addition, the operation at 350 nm with this good stability and a long beam lifetime allowed us to perform the first user experiment in biology and to start with a campaign for using the laser as photons source for experiments in other domains, coupling FEL light and the Synchrotron Radiation. For this, FEL starts to be very competitive with respect to the other conventional laser sources, provided that it could oscillate further in the UV, say at 300 nm and below. So, the real challenge is now given by the lasing at shorter wavelengths and, for this, by the optical technology existing nowadays. Since 1992 the efforts have been concentrating to look for every kind of solution allowing us to overcome the problem of having a very low gain. From an optical point of view, in the range of wavelengths explored, there is a lack of transparents dielectric materials for substrates and coatings. Substrates are required at the same time to be relatively not absorbing (a few tens 10{sup -6}), to have a very good surface quality (RMS roughness below 10 {Angstrom}) because of scattering losses dramatically increasing in this spectral range and, due to the thermal load of the undulator emission, to have adequate thermal characteristics. In order to fulfill all these requirements, a good characterisation and modelisation of the substrates is needed, especially to correlate thermal loading and mechanical deformations from one hand, and roughness and scattering losses from the other hand. Coatings must be not absorbing too and, above all, the most amorphous as possible (this could be obtained with IBS deposition technique), in order to insure a good reproduction of the substrate roughness at the interfaces and on the top layer and an higher resistance to the XUV photons load.

  10. Spectral mirror for ultra-short, high peak power, multi-PW Ti:sapphire lasers

    A multilayer mirror for spectral filtering adapted to ultra-short and multi-PW Ti:Sa laser has been designed, manufactured and characterized. The method used to determine both the reflectivity shape and the coating design leads to global compensation of gain narrowing, saturation and spectral phase. The result is a spectral control on 200 nm range while keeping a flat spectral phase. This kind of filter will enable obtaining 15 fs pulse duration for multi-PW laser systems based on Ti:Sa. (authors)