Science.gov

Sample records for optical absorption properties

  1. Estimation of aerosol optical properties considering hygroscopicity and light absorption

    NASA Astrophysics Data System (ADS)

    Jung, Chang Hoon; Lee, Ji Yi; Kim, Yong Pyo

    2015-03-01

    In this study, the influences of water solubility and light absorption on the optical properties of organic aerosols were investigated. A size-resolved model for calculating optical properties was developed by combining thermodynamic hygroscopic growth and aerosol dynamics models. The internal mixtures based on the homogeneous and core-shell mixing were compared. The results showed that the radiative forcing (RF) of Water Soluble Organic Carbon (WSOC) aerosol can be estimated to range from -0.07 to -0.49 W/m2 for core-shell mixing and from -0.09 to -0.47 W/m2 for homogeneous mixing under the simulation conditions (RH = 60%). The light absorption properties of WSOC showed the mass absorption efficiency (MAE) of WSOC can be estimated 0.43-0.5 m2/g, which accounts for 5-10% of the MAE of elemental carbon (EC). The effect on MAE of increasing the imaginary refractive index of WSOC was also calculated, and it was found that increasing the imaginary refractive index by 0.001i enhanced WSOC aerosol absorption by approximately 0.02 m2/g. Finally, the sensitivity test results revealed that changes in the fine mode fraction (FMF) and in the geometric mean diameter of the accumulation mode play important roles in estimating RF during hygroscopic growth.

  2. Tuning nonlinear optical absorption properties of WS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Long, Hui; Tao, Lili; Tang, Chun Yin; Zhou, Bo; Zhao, Yuda; Zeng, Longhui; Yu, Siu Fung; Lau, Shu Ping; Chai, Yang; Tsang, Yuen Hong

    2015-10-01

    To control the optical properties of two-dimensional (2D) materials is a long-standing goal, being of both fundamental and technological significance. Tuning nonlinear optical absorption (NOA) properties of 2D transition metal dichalcogenides in a cost effective way has emerged as an important research topic because of its possibility to custom design NOA properties, implying enormous applications including optical computers, communications, bioimaging, and so on. In this study, WS2 with different size and thickness distributions was fabricated. The results demonstrate that both NOA onset threshold, FON, and optical limiting threshold, FOL, of WS2 under the excitation of a nanosecond pulsed laser can be tuned over a wide range by controlling its size and thickness. The FON and FOL show a rapid decline with the decrease of size and thickness. Due to the edge and quantum confinement effect, WS2 quantum dots (2.35 nm) exhibit the lowest FON (0.01 J cm-2) and FOL (0.062 J cm-2) among all the samples, which are comparable to the lowest threshold achieved in graphene based materials, showing great potential as NOA materials with tunable properties.To control the optical properties of two-dimensional (2D) materials is a long-standing goal, being of both fundamental and technological significance. Tuning nonlinear optical absorption (NOA) properties of 2D transition metal dichalcogenides in a cost effective way has emerged as an important research topic because of its possibility to custom design NOA properties, implying enormous applications including optical computers, communications, bioimaging, and so on. In this study, WS2 with different size and thickness distributions was fabricated. The results demonstrate that both NOA onset threshold, FON, and optical limiting threshold, FOL, of WS2 under the excitation of a nanosecond pulsed laser can be tuned over a wide range by controlling its size and thickness. The FON and FOL show a rapid decline with the decrease of size

  3. Tuning nonlinear optical absorption properties of WS₂ nanosheets.

    PubMed

    Long, Hui; Tao, Lili; Tang, Chun Yin; Zhou, Bo; Zhao, Yuda; Zeng, Longhui; Yu, Siu Fung; Lau, Shu Ping; Chai, Yang; Tsang, Yuen Hong

    2015-11-14

    To control the optical properties of two-dimensional (2D) materials is a long-standing goal, being of both fundamental and technological significance. Tuning nonlinear optical absorption (NOA) properties of 2D transition metal dichalcogenides in a cost effective way has emerged as an important research topic because of its possibility to custom design NOA properties, implying enormous applications including optical computers, communications, bioimaging, and so on. In this study, WS2 with different size and thickness distributions was fabricated. The results demonstrate that both NOA onset threshold, F(ON), and optical limiting threshold, F(OL), of WS2 under the excitation of a nanosecond pulsed laser can be tuned over a wide range by controlling its size and thickness. The F(ON) and F(OL) show a rapid decline with the decrease of size and thickness. Due to the edge and quantum confinement effect, WS2 quantum dots (2.35 nm) exhibit the lowest F(ON) (0.01 J cm(-2)) and F(OL) (0.062 J cm(-2)) among all the samples, which are comparable to the lowest threshold achieved in graphene based materials, showing great potential as NOA materials with tunable properties. PMID:26456545

  4. AEROSOL OPTICAL PROPERTIES AND BIOGENIC SOA: EFFECT ON HYGROSCOPIC PROPERTIES AND LIGHT ABSORPTION

    EPA Science Inventory

    This study will provide a comprehensive characterization of optical properties of biogenic SOA and their sensitivity to anthropogenic influence. Several parameters critical for climate modeling, such as absorption cross-section, single scattering albedo and sensitivity to R...

  5. Relationship of the optical absorption and scattering properties with mechanical and structural properties of apple tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical absorption and scattering properties of fruit change with the physiological and biochemical activities in the tissue during ripening and postharvest storage. But it has not been well understood on how these changes are related to the structural and mechanical properties of fruit. This resear...

  6. Ripeness of 'Sun Bright' tomato using the optical absorption and scattering properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maturity is one of the most important factors in determining the processing and eating quality of tomato. The objective of this research was to test the suitability of optical absorption and scattering properties for evaluating the maturity of tomatoes. Optical absorption and reduced scattering coef...

  7. Optical absorption properties of dispersed gold and silver alloy nanoparticles.

    PubMed

    Wilcoxon, Jess

    2009-03-01

    The oldest topic in nanoscience is the size-dependent optical properties of gold and silver colloids or nanoparticles, first investigated scientifically by Michael Faraday in 1857. In the modern era, advances in both synthesis and characterization have resulted in new insights into the size-dependent absorbance of Au and Ag nanoparticles with sizes below the classical limit for Mie theory. In this paper we discuss the synthesis and properties of core/shell and nanoalloy particles of Au and Ag, compare them to particles of pure gold and silver, and discuss how alloying affects nanoparticle chemical stability. We show that composition, size, and nanostructure (e.g., core/shell vs quasi-random nanoalloy) can all be employed to adjust the optical absorbance properties. The type of nanostructure--core/shell vs alloy--is reflected in their optical absorbance features. PMID:19708105

  8. Broadband optical limiting and nonlinear optical absorption properties of a novel hyperbranched conjugated polymer

    NASA Astrophysics Data System (ADS)

    Li, Chao; Liu, Chunling; Li, Quanshui; Gong, Qihuang

    2004-12-01

    The nonlinear transmittance of a novel hyperbranched conjugated polymer named DMA-HPV has been measured in CHCl 3 solution using a nanosecond optical parametric oscillator. DMA-HPV shows excellent optical limiting performance in the visible region from 490 to 610 nm. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its huge and broadband nonlinear optical absorption.

  9. Tuning optical and three photon absorption properties in graphene oxide-polyvinyl alcohol free standing films

    NASA Astrophysics Data System (ADS)

    Karthikeyan, B.; Udayabhaskar, R.; Hariharan, S.

    2016-07-01

    We report the optical and nonlinear optical properties of graphene oxide (GO)-polyvinyl alcohol (PVA) free standing films. The composite polymer films were prepared in ex-situ method. The variation in optical absorption spectra and optical constants with the amount of GO loading was noteworthy from the optical absorption spectroscopic studies. Nonlinear optical studies done at 532 nm using 5 ns laser pulses show three photon absorption like behaviour. Both steady state and time resolved fluorescence studies reveal that the GO was functioning as a pathway for the decay of fluorescence from PVA. This is attributed to the energy level modifications of GO through hydroxyl groups with PVA. Raman spectroscopy also supports the interaction between GO and PVA ions through OH radicals.

  10. Investigation on optical absorption properties of ion irradiated single walled carbon nanotubes

    SciTech Connect

    Vishalli, Dharamvir, Keya; Kaur, Ramneek; Raina, K. K.; Avasthi, D. K.; Jeet, Kiran

    2015-08-28

    In the present study change in the optical absorption properties of single walled carbon nanotubes (SWCNTs) under nickel ion (60 MeV) irradiation at various fluences has been investigated. Langmuir Blodgett technique is used to deposit SWCNT thin film of uniform thickness. AFM analysis shows a network of interconnected bundles of nanotubes. UV-Vis-NIR absorption spectra indicate that the sample mainly contain SWCNTs of semiconducting nature. It has been found in absorption spectra that there is decrease in the intensity of the characteristic SWCNT peaks with increase in fluence. At fluence value 1×10{sup 14} ions/cm{sup 2} there is almost complete suppression of the characteristic SWCNTs peaks.The decrease in the optical absorption with increase in fluence is due to the increase in the disorder in the system which leads to the decrease in optically active states.

  11. Two-photon absorption and optical-limiting properties of a novel organic compound

    NASA Astrophysics Data System (ADS)

    Ye, Lihua; Zhang, Junxiang; Cui, Yiping; Li, Zhenhua; He, Anzhi

    2002-09-01

    The two-photon absorption and applications become the hot points in the recent photoelectronic material research field. The two-photon absorption materials can be applied to many fields such as up-conversion lasing, optical limiting, optical stabilization, three-dimension optical storage, three-dimension micro-machining, et al. Especially studies of optical power limiting have become more interesting to the research community because of the need for automatic protection of optical sensors against intense laser radiation. Here we report the observation of the TPA and optical power limiting property of a novel double conjugated molecule DSBDR1 in solution. The linear absorption spectral is observed using a scanning spectrophotometer. Using Nd:YAG laser pulse as exciting laser, the incident pulse energy and the transmitted pulse energy are respectively recorded by an energy meter. Then we obtain the nonlinear absorption coefficient of the novel double conjugated molecule in THF. Figures show that the molecule exhibts the large TPA cross-section and excellent optical limiting at 1064 nm. The nonlinear absorption mechanism of the novel organic compound is finally analyzed.

  12. Monitoring transformer oil insulation using optical absorption properties

    NASA Astrophysics Data System (ADS)

    Rose, Benjamin P.

    As the electrical power distribution system ages, new methods of determining the quality of electrical transformer units are needed. Due to the relatively high expense of loss of service and safety hazards, a relatively cheap sensor to track the age of the insulation would aide in the progress of an intelligent power grid. The degradation of solid insulating paper releases some of the age indicating organic compounds into the oil. At present, the only available method to determine the concentration of those compounds is to perform high performance liquid chromatography (HPLC) testing in a laboratory. This is an expensive and time consuming activity that also requires transformer to be taken offline. Currently there are no sensors that can directly (on-line) measure the chemical integrity of the material. This research was focused upon one of the well known organic compounds released by paper into the transformer oil - 2-furfuraldehyde (2FAL). Previous methods of 2FAL detection were explored and expounded upon. A device was constructed to utilize light emitting diodes to optically interrogate solid discs made out of chemically active material in multiple tests. A 10 kVA distribution transformer was fitted with a special device allowing a continuous oil circulation and the optical setup. The transformer was tested while being loaded under accelerated ageing conditions. A premature failure of the distribution transformer did not allow any correlation between concentration of 2FAL and the optical signals. Previously sampled oils for a current transformer (CT) were also tested for chemical analysis in the laboratory and optical signals from the newly developed optical device were obtained. A 95% linear correlation was found between the age of the CT oil and the output of the optical device. Although the technique was validated and does seem to have merit, more tests are needed before the optical device can be recommended for use in the field.

  13. Three-dimensional printed optical phantoms with customized absorption and scattering properties.

    PubMed

    Diep, Phuong; Pannem, Sanjana; Sweer, Jordan; Lo, Justine; Snyder, Michael; Stueber, Gabriella; Zhao, Yanyu; Tabassum, Syeda; Istfan, Raeef; Wu, Junjie; Erramilli, Shyamsunder; Roblyer, Darren

    2015-11-01

    Three-dimensional (3D) printing offers the promise of fabricating optical phantoms with arbitrary geometry, but commercially available thermoplastics provide only a small range of physiologically relevant absorption (µa) and reduced scattering (µs`) values. Here we demonstrate customizable acrylonitrile butadiene styrene (ABS) filaments for dual extrusion 3D printing of tissue mimicking optical phantoms. µa and µs` values were adjusted by incorporating nigrosin and titanium dioxide (TiO2) in the filament extrusion process. A wide range of physiologically relevant optical properties was demonstrated with an average repeatability within 11.5% for µa and 7.71% for µs`. Additionally, a mouse-simulating phantom, which mimicked both the geometry and optical properties of a hairless mouse with an implanted xenograft tumor, was printed using dual extrusion methods. 3D printed tumor optical properties matched the live tumor with less than 3% error at a wavelength of 659 nm. 3D printing with user defined optical properties may provide a viable method for durable optically diffusive phantoms for instrument characterization and calibration. PMID:26600987

  14. Three-dimensional printed optical phantoms with customized absorption and scattering properties

    PubMed Central

    Diep, Phuong; Pannem, Sanjana; Sweer, Jordan; Lo, Justine; Snyder, Michael; Stueber, Gabriella; Zhao, Yanyu; Tabassum, Syeda; Istfan, Raeef; Wu, Junjie; Erramilli, Shyamsunder; Roblyer, Darren

    2015-01-01

    Three-dimensional (3D) printing offers the promise of fabricating optical phantoms with arbitrary geometry, but commercially available thermoplastics provide only a small range of physiologically relevant absorption (µa) and reduced scattering (µs`) values. Here we demonstrate customizable acrylonitrile butadiene styrene (ABS) filaments for dual extrusion 3D printing of tissue mimicking optical phantoms. µa and µs` values were adjusted by incorporating nigrosin and titanium dioxide (TiO2) in the filament extrusion process. A wide range of physiologically relevant optical properties was demonstrated with an average repeatability within 11.5% for µa and 7.71% for µs`. Additionally, a mouse-simulating phantom, which mimicked both the geometry and optical properties of a hairless mouse with an implanted xenograft tumor, was printed using dual extrusion methods. 3D printed tumor optical properties matched the live tumor with less than 3% error at a wavelength of 659 nm. 3D printing with user defined optical properties may provide a viable method for durable optically diffusive phantoms for instrument characterization and calibration. PMID:26600987

  15. Optical absorption measurement system

    DOEpatents

    Draggoo, Vaughn G.; Morton, Richard G.; Sawicki, Richard H.; Bissinger, Horst D.

    1989-01-01

    The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

  16. Solar energy absorption characteristics and the effects of heat on the optical properties of several coatings

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1981-01-01

    The solar energy absorption characteristics of several high temperature coatings were determined and effects of heat on these coatings were evaluated. Included in the investigation were an electroplated alloy of black chrome and vanadium, electroplated black chrome, and chemically colored 316 stainless steel. Each of the coatings possessed good selective solar energy absorption properties at laboratory ambient temperature. Measured at a temperature of 700 K (800 F), the emittances of black chrome, black chrome vanadium, and colored stainless steel were 0.11, 0.61, and 0.15, respectively. Black chrome and black chrome vanadium did not degrade optically in the presence of high heat (811 K (1000 F)). Chemically colored stainless steel showed slight optical degradation when exposed to moderately high heat (616 K (650 F)0, but showed more severe degradation at exposure temperatures beyond this level. Each of the coatings showed good corrosion resistance to a salt spray environment.

  17. Rest-frame optical properties of luminous, radio-selected broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Runnoe, Jessie C.; Ganguly, R.; Brotherton, M. S.; DiPompeo, M. A.

    2013-08-01

    We have obtained Infrared Telescope Facility/SpeX spectra of eight moderate-redshift (z = 0.7-2.4), radio-selected (log R* ≈ 0.4-1.9) broad absorption line (BAL) quasars. The spectra cover the rest-frame optical band. We compare the optical properties of these quasars to those of canonically radio-quiet (log R* ≲ 1) BAL quasars at similar redshifts and to low-redshift quasars from the Palomar-Green catalogue. As with previous studies of BAL quasars, we find that [O III] λ5007 is weak, and optical Fe II emission is strong, a rare combination in canonically radio-loud (log R* ≳ 1) quasars. With our measurements of the optical properties, particularly the Balmer emission-line widths and the continuum luminosity, we have used empirical scaling relations to estimate black hole masses and Eddington ratios. These lie in the range (0.4-2.6) × 109 M⊙ and 0.1-0.9, respectively. Despite their comparatively extreme radio properties relative to most BAL quasars, their optical properties are quite consistent with those of radio-quiet BAL quasars and dissimilar to those of radio-loud non-BAL quasars. While BAL quasars generally appear to have low values of [O III] λ5007/Fe II an extreme of `Eigenvector 1', the Balmer line widths and Eddington ratios do not appear to significantly differ from those of unabsorbed quasars at similar redshifts and luminosities.

  18. Optical nonlinear properties of InAs quantum dots by means of transient absorption measurements

    NASA Astrophysics Data System (ADS)

    Nakamura, H.; Nishikawa, S.; Kohmoto, S.; Kanamoto, K.; Asakawa, K.

    2003-07-01

    The optical nonlinear properties of self-assembled InAs/GaAs quantum dots (QDs) were experimentally verified by means of transient absorption measurements. A saturation pulse energy Ps of 13 fJ/μm2 and an absorption recovery time τr of 55 ps were obtained from transmission bleaching and pump/probe measurements for a waveguide sample with ten-layer-stacked QDs. An absorption saturation intensity Is of 2.5×104W/cm2, calculated from Ps and τr, was found. The saturation pulse energy is up to an order of magnitude smaller than, or at least comparable with, the reported values for excitons in quantum wells of III-V compound semiconductors. The dipole length, as calculated from the absorption cross section, is of the same order as the lattice constant of the InAs QDs. The results are expected to experimentally verify that QDs show a delta-function-like density of states.

  19. Effect of swift heavy ion irradiation on optical absorption properties of SWCNTs

    NASA Astrophysics Data System (ADS)

    Vishalli, Raina, K. K.; Avasthi, D. K.; Srivastava, Alok; Dharamvir, Keya

    2016-05-01

    In the present work, experimental investigations on the optical absorption properties of swift heavy ion irradiated single walled carbon nanotubes (SWCNTs) have been carried out. The uniform thin films of SWCNTs have been deposited on quartz substrate by Langmuir Blodgett (LB) method in a layer by layer manner. The irradiation of thin films is carried out by nickel ion beam of energy 60 MeV at different fluences. The variation in the S11, S22, and M11 band in optical spectra of SWCNTs has been studied before and after irradiation. The decrease in intensity/area of the bands corresponding to both semiconducting and metallic SWCNTs has been observed with increasing fluence.

  20. Optical Absorption and Photo-Thermal Conversion Properties of CuO/H2O Nanofluids.

    PubMed

    Wang, Liangang; Wu, Mingyan; Wu, Daxiong; Zhang, Canying; Zhu, Qunzhi; Zhu, Haitao

    2015-04-01

    Stable CuO/H2O nanofluids were synthesized in a wet chemical method. Optical absorption property of CuO/H2O nanofluids was investigated with hemispheric transmission spectrum in the wavelength range from 200 nm to 2500 nm. Photo-thermal conversion property of the CuO/H2O nanofluids was studied with an evaluation system equipped with an AUT-FSL semiconductor/solid state laser. The results indicate that CuO/H2O nanofluids have strong absorption in visible light region where water has little absorption. Under the irradiation of laser beam with a wavelength of 635 nm and a power of 0.015 W, the temperature of CuO/H2O nanofluids with 1.0% mass fraction increased by 5.6 °C within 40 seconds. Furthermore, the temperature elevation of CuO/H2O nanofluids was proved to increase with increasing mass fractions. On the contrast, water showed little temperature elevation under the identical conditions. The present work shows that the CuO/H2O nanofluids have high potential in the application as working fluids for solar utilization purpose. PMID:26353558

  1. The INTEGRAL/IBIS AGN catalogue - I. X-ray absorption properties versus optical classification

    NASA Astrophysics Data System (ADS)

    Malizia, A.; Bassani, L.; Bazzano, A.; Bird, A. J.; Masetti, N.; Panessa, F.; Stephen, J. B.; Ubertini, P.

    2012-11-01

    In this work we present the most comprehensive INTEGRAL active galactic nucleus (AGN) sample. It lists 272 AGN for which we have secure optical identifications, precise optical spectroscopy and measured redshift values plus X-ray spectral information, i.e. 2-10 and 20-100 keV fluxes plus column density. Here we mainly use this sample to study the absorption properties of active galaxies, to probe new AGN classes and to test the AGN unification scheme. We find that half (48 per cent) of the sample is absorbed, while the fraction of Compton-thick AGN is small (˜7 per cent). In line with our previous analysis, we have however shown that when the bias towards heavily absorbed objects which are lost if weak and at large distance is removed, as it is possible in the local Universe, the above fractions increase to become 80 and 17 per cent. We also find that absorption is a function of source luminosity, which implies some evolution in the obscuration properties of AGN. A few peculiar classes, so far poorly studied in the hard X-ray band, have been detected and studied for the first time such as 5 X-ray bright optically normal galaxies, 5 type 2 QSOs and 11 low-ionization nuclear emission regions. In terms of optical classification, our sample contains 57 per cent of type 1 and 43 per cent of type 2 AGN; this subdivision is similar to that found in X-rays if unabsorbed versus absorbed objects are considered, suggesting that the match between optical and X-ray classifications is overall good. Only a small percentage of sources (12 per cent) does not fulfil the expectation of the unified theory as we find 22 type 1 AGN which are absorbed and 10 type 2 AGN which are unabsorbed. Studying in depth these outliers we found that most of the absorbed type 1 AGN have X-ray spectra characterized by either complex or warm/ionized absorption more likely due to ionized gas located in an accretion disc wind or in the biconical structure associated with the central nucleus, therefore

  2. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-08-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  3. Properties of multilayer optical systems formed by layers with small absorption in inclined falling of radiation

    NASA Astrophysics Data System (ADS)

    Karyaev, Konstantin V.; Zhoga, Eugene V.; Putilin, Eduard S.

    2000-10-01

    Multilayer dielectric systems find wide employment in different fields of science and engineering. Dielectric systems, formed by layers with small absorption, attract particular interest. Value of absorption, as a rule, depends on structure of the system (order and optical thickness of layers), angle of incidence and wavelength of radiation. Experiment shows that there are peaks of absorption on certain angles of incidence and wavelength, but behavior of absorption wasn't studied well. Model of a system, formed by isotropic layers settled on semiinfinite substate proved to be a good approximation for many of real optical systems. We studied pecularities in spectral dependencies of reflection, transmission and absorption coefficients in dependance on the angle of incidence and wavelength of falling radiation with flat wave front. Problem was solved on the basis of Maxwell equations and corresponding boundary conditions.

  4. Photochromic polymers as a versatile tool for devices based on switchable absorption and other optical properties

    NASA Astrophysics Data System (ADS)

    Bertarelli, Chiara; Castagna, Rossella; Pariani, Giorgio; Bianco, Andrea

    2011-10-01

    Photochromic polymer materials with large modulation of properties enable the production of functional optical devices. The light-triggered change in color has been exploited to develop multi-object focal plane masks for astronomical instrumentation and holographic optical elements for interferometric optical testing. Modulation of properties other than color (i.e. refractive index, light emission or Raman scattering) opens the way to many other applications into technology, such as rewritable optical memories, switchable organic lasers, etc. In this background, examples from molecular design to devices are highlighted.

  5. Study of nonlinear optical absorption properties of V2O5 nanoparticles in the femtosecond excitation regime

    NASA Astrophysics Data System (ADS)

    Molli, Muralikrishna; Bhat Kademane, Abhijit; Pradhan, Prabin; Sai Muthukumar, V.

    2016-08-01

    In this work, we report for the first time, the nonlinear optical absorption properties of vanadium pentoxide (V2O5) nanoparticles in the femtosecond excitation regime. V2O5 nanoparticles were synthesized through solution combustion technique. The as-synthesized samples were further characterized using XRD, FESEM, EDAX, TEM and UV-visible spectroscopy. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies showed the size of the nanoparticles to be ~200 nm. Open-aperture z-scan technique was employed to study the nonlinear optical absorption behavior of the synthesized samples using a 100-fs laser pulses at 800 nm from a regeneratively amplified Ti: sapphire laser. The mechanism of nonlinear absorption was found to be a three-photon absorption process which was explained using the density of states of V2O5 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered for optical-power-limiting applications.

  6. Study of nonlinear optical absorption properties of Sb2Se3 nanoparticles in the nanosecond and femtosecond excitation regime

    NASA Astrophysics Data System (ADS)

    Molli, Muralikrishna; Pradhan, Prabin; Dutta, Devarun; Jayaraman, Aditya; Bhat Kademane, Abhijit; Muthukumar, V. Sai; Kamisetti, Venkataramaniah; Philip, Reji

    2016-05-01

    In this work, we report for the first time, the nonlinear optical absorption properties of antimony selenide (Sb2Se3) nanoparticles synthesized through solvothermal route. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies revealed that the nanoparticles are in the range of 10-40 nm. Elemental analysis was performed using EDAX. The nanosecond optical limiting effect was characterized by using fluence-dependent transmittance measurements with 15-ns laser pulses at 532 and 1064 nm excitation wavelengths. Mechanistically, effective two-photon (2PA) absorption and nonlinear scattering processes were the dominant nonlinear processes at both the wavelengths. At 800 nm excitation in the femtosecond regime (100 fs), the nonlinear optical absorption was found to be a three-photon (3PA) process. Both 2PA and 3PA processes were explained using the band structure and density of states of Sb2Se3 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered to have optical power-limiting applications in the visible range.

  7. Optical absorption properties of electron bubbles and experiments on monitoring individual electron bubbles in liquid helium

    NASA Astrophysics Data System (ADS)

    Guo, Wei

    When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms, which is referred to as an electron bubble. It represents a fine example of a quantum-mechanical particle confined in a potential well. In this dissertation, we describe our studies on bubble properties, especially the optical absorption properties of ground state electron bubbles and experiments on imaging individual electron bubbles in liquid helium. We studied the effect of zero-point and thermal fluctuations on the shape of ground state electron bubbles in liquid helium. The results are used to determine the line shape for the 1S to 1P optical transition. The calculated line shape is in very good agreement with the experimental measurements of Grimes and Adams. For 1S to 2P transition, the obtained transition line width agrees well with the measured data of Zipfel over a range of pressure up to 15 bars. Fluctuations in the bubble shape also make other "unallowed" transitions possible. The transition cross-sections from the 1S state to the 1D and 2D states are calculated with magnitude approximately two orders smaller than that of the 1S to 1P and 2P transitions. In our electron bubble imaging experiments, a planar ultrasonic transducer was used to generate strong sound wave pulse in liquid helium. The sound pulse passed through the liquid so as to produce a transient negative pressure over a large volume (˜ 1 cm3). An electron bubble that was passed by the sound pulse exploded for a fraction of a microsecond and grew to have a radius of around 10 microns. While the bubble had this large size it was illuminated with a flash lamp and its position was recorded. In this way, we can determine its position. Through the application of a series of sound pulses, we can then take images along the track of individual electrons. The motion of individual electron bubbles has been successfully monitored. Interesting bubble tracks that may relate to electrons

  8. Phosphorescence, near-infrared absorption and nonlinear optical property of a new chiral organic crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Bei; Zhao, Yu-Mei; Yong, Guo-Ping

    2014-02-01

    A new enantiomerically pure compound was synthesized by the single step reduced reaction from 2-(imidazo[1,2-a]pyridin-2-yl)-2-oxo-N-(pyridin-2-yl)acetamide via chiral induction with D-tartaric acid in good yield. Single crystal data confirm this compound crystallizes in chiral space group P21. Transmission spectrum reveals that the crystal has low UV cut-off of 372 nm and has a good transmittance in the entire visible and near-infrared (NIR)region to 1100 nm, indicating its optical application. Kurtz powder test shows a good second harmonic generation (SHG) which also demonstrates its chiral structure. Moreover, this material exhibits blue phosphorescence with quantum yield of 3.6% and unusually NIR absorption between 1500 nm and 2500 nm. Therefore, this new chiral crystal is a promising multifunctional material for the blue phosphorescence, NIR absorption and nonlinear optical (NLO) applications.

  9. 'Diamondlike' carbon films - Optical absorption, dielectric properties, and hardness dependence on deposition parameters

    NASA Technical Reports Server (NTRS)

    Natarajan, V.; Lamb, J. D.; Woollam, J. A.; Liu, D. C.; Gulino, D. A.

    1985-01-01

    An RF plasma deposition system was used to prepare amorphous 'diamondlike' carbon films. The source gases for the RF system include methane, ethylene, propane, and propylene, and the parameters varied were power, dc substrate bias, and postdeposition anneal temperature. Films were deposited on various substrates. The main diagnostics were optical absorption in the visible and in the infrared, admittance as a function of frequency, hardness, and Auger and ESCA spectroscopy. Band gap is found to depend strongly on RF power level and band gaps up to 2.7 eV and hardness up to 7 Mohs were found. There appears to be an inverse relationship between hardness and optical band gap.

  10. Asymptotic Solutions for Optical Properties of Large Particles with Strong Absorption

    NASA Technical Reports Server (NTRS)

    Yang, Ping; Gao, Bo-Cai; Baum, Bryan A.; Hu, Yong X.; Wiscombe, Warren J.; Mishchenko, Michael I.; Winker, Dave M.; Nasiri, Shaima L.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    For scattering calculations involving nonspherical particles such as ice crystals, we show that the transverse wave condition is not applicable to the refracted electromagnetic wave in the context of geometric optics when absorption is involved. Either the TM wave condition (i.e., where the magnetic field of the refracted wave is transverse with respect to the wave direction) or the TE wave condition (i.e., where the electric field is transverse with respect to the propagating direction of the wave) may be assumed for the refracted wave in an absorbing medium to locally satisfy the electromagnetic boundary condition in the ray tracing calculation. The wave mode assumed for the refracted wave affects both the reflection and refraction coefficients. As a result, a nonunique solution for these coefficients is derived from the electromagnetic boundary condition. In this study we have identified the appropriate solution for the Fresnel reflection/refraction coefficients in light scattering calculation based on the ray tracing technique. We present the 3 x 2 refraction or transmission matrix that completely accounts for the inhomogeneity of the refracted wave in an absorbing medium. Using the Fresnel coefficients for an absorbing medium, we derive an asymptotic solution in an analytical format for the scattering properties of a general polyhedral particle. Numerical results are presented for hexagonal plates and columns with both preferred and random orientations. The asymptotic theory can produce reasonable accuracy in the phase function calculations in the infrared window region (wavelengths near 10 micron) if the particle size (in diameter) is on the order of 40 micron or larger. However, since strong absorption is assumed in the computation of the single-scattering albedo in the asymptotic theory, the single scattering albedo does not change with variation of the particle size. As a result, the asymptotic theory can lead to substantial errors in the computation of

  11. Luminescence properties and optical absorption of X ray-irradiated KBr: Ce3(+), Tb(3+) crystals.

    PubMed

    Bangaru, S; Saradha, K; Muralidharan, G

    2015-03-01

    This paper reports that KBr doubly doped with Tb(3+) and Ce(3+) were prepared by Bridgman-Stockbarger method and characterized by Optical absorption, Photoluminescence (PL), Thermoluminescence (TL), Photo stimulated emission (PSL) and TL emission, after X-ray irradiation have been observed. The optical absorption measurement indicates that F and Z3 centers are formed in the crystal during X-ray irradiation process. It was attempted to incorporate a broad band of Ce(3+) sensitizer into the narrow band emission of Tb(3+) in the KBr host without reduction of emission intensity. Co-doping of Ce(3+) ions in KBr:Tb(3+) crystal showed a broad band emission due to the d-f transition of Ce(3+) and a reduction in the intensity of emission peaks due to (5)days → (7)F6 transition of Tb(3+) when they were excited at 250 nm. These results supported that an effective energy transfer occurs from Ce(3+) to Tb(3+) in the KBr host. Co-doping Ce(3+) ions greatly intensified the excitation peak at 260 nm for the emission at 390 nm of Tb(3+) which means that more lattice defects, involved in the energy absorption and transfer to Tb(3+), are formed by the Ce(3+) co-doping. The integrated light intensity is two orders of magnitude higher as compared to the undoped samples for similar doses of irradiation and heating rate. Thermoluminescence process has been identified due to thermal mobilization of F-electrons and this causes peaks at 371 K and at 427 K, 457 K in KBr: Ce(3+), Tb(3+) crystals. The defects generated by irradiation were monitored by optical absorption and trap parameters for the TL process were calculated and presented. PMID:25585645

  12. Optical properties of Mg-doped VO2: Absorption measurements and hybrid functional calculations

    NASA Astrophysics Data System (ADS)

    Hu, Shuanglin; Li, S.-Y.; Ahuja, R.; Granqvist, C. G.; Hermansson, K.; Niklasson, G. A.; Scheicher, R. H.

    2012-11-01

    Mg-doped VO2 thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < ħω < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.

  13. Optical properties of Mg-doped VO{sub 2}: Absorption measurements and hybrid functional calculations

    SciTech Connect

    Hu Shuanglin; Li, S.-Y.; Granqvist, C. G.; Niklasson, G. A.; Ahuja, R.; Scheicher, R. H.; Hermansson, K.

    2012-11-12

    Mg-doped VO{sub 2} thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < h{omega} < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.

  14. Crystal field effect on EPR and optical absorption properties of natural green zoisite.

    PubMed

    Javier-Ccallata, Henry; Watanabe, Shigueo

    2013-03-01

    In this study the electron paramagnetic resonance (EPR) and optical absorption (OA) of natural crystal of zoisite were investigated after γ ((60)Co) irradiation and high temperature annealing. EPR measurements show that the zoisite from Tefilo Otoni MG Brazil contain Cr(3+), Fe(3+) and Mn(2+) ions and occupy distorted Al(3+) octahedral and tetrahedral sites which are subjected to the action of a strong crystal field in axial direction. Absorption bands which in principle give rise to sets of EPR lines between 500 and 2500 G were found using the deconvolution method. The application of high doses of gamma ray and high temperature annealing has shown no significant effects on EPR and OA spectra. Spin-allowed, spin-forbidden and crystal field parameters were calculated for 3d(3) configuration and interpreted using the spin Hamiltonian formalism containing axial and rhombic terms in low symmetries. PMID:23291113

  15. Absorption properties of identical atoms

    SciTech Connect

    Sancho, Pedro

    2013-09-15

    Emission rates and other optical properties of multi-particle systems in collective and entangled states differ from those in product ones. We show the existence of similar effects in the absorption probabilities for (anti)symmetrized states of two identical atoms. The effects strongly depend on the overlapping between the atoms and differ for bosons and fermions. We propose a viable experimental verification of these ideas. -- Highlights: •The absorption rates of a pair of identical atoms in product and (anti)symmetrized states are different. •The modifications of the optical properties are essentially determined by the overlapping between the atoms. •The absorption properties differ, in some cases, for bosons and fermions.

  16. A method for segregating the optical absorption properties and the mass concentration of winter time urban aerosol

    NASA Astrophysics Data System (ADS)

    Ajtai, T.; Utry, N.; Pintér, M.; Major, B.; Bozóki, Z.; Szabó, G.

    2015-12-01

    A novel in-situ, real time method for the determination of inherent absorption properties of light absorbing carbonaceous particulate matter and its possible application for source apportionment are introduced here. The method is deduced from a two-week campaign under wintry urban conditions during which strong correlation was found between aerosol number size distribution and wavelength dependent optical absorption coefficient (AOC(λ)), measured by a Single Mobility Particle Sizer (SMPS) and a multi-wavelength photoacoustic absorption spectrometer, respectively, while wood burning and traffic (i.e. fossil fuel burning) activity were identified to be the dominant sources of carbonaceous particulate. Indeed, during the whole campaign, regardless of the actual emission strength of the aerosol sources, the measured number size distributions were always dominated by two unimodal modes with Count Mean Diameter (CMD) of 20 and 100 nm, which could be correlated to traffic and wood burning activities, respectively. AAEff, AAEwb (i.e. the Aerosol Angström Exponent of traffic and wood burning aerosol, respectively), σff(266 nm), σff(1064 nm), σwb(266 nm) and σff(1064 nm) (i.e. the segregated mass specific optical absorption coefficients at two of the measurement wavelengths) were found to be 1.17 ± 0.18, 2.6 ± 0.14, 7.3 ± 0.3 m2g-1, 1.7 ± 0.1 m2g-1 3.4 ± 0.3 m2g-1 and 0.31 ± 0.08 m2g-1, respectively. Furthermore the introduced methodology can also disentangle and quantify the temporal variation of both the segregated optical absorptions and the segregated mass concentrations of traffic and wood burning aerosol. Accordingly, the contribution of wood burning to optical absorption of PM was found to be negligible at 1064 nm but increased gradually towards the shorter wavelengths and became commensurable with the optical absorption of traffic at 266 nm during the whole measurement period. Furthermore, the contribution of wood burning mass to CM (mass of carbonaceous

  17. Analyzing Water's Optical Absorption

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

  18. The WO3/WS2 nanostructures: Preparation, characterization and optical absorption properties

    NASA Astrophysics Data System (ADS)

    Cao, Shixiu; Zhao, Cong; Han, Tao; Peng, Lingling

    2016-07-01

    The WO3/WS2 nanostructures were successfully prepared using a two-step hydrothermal/gas phase method. The physical properties of the nanostructures were characterized using XRD, SEM, TEM, UV-visible spectroscopy. The WO3/WS2 nanostructures obtained were coexistence of WO3 and WS2 in the same particle. The WO3/WS2 nanostructures contained a wide and intensive absorption in the UV-visible light region of 245-750 nm, which showed that the WO3/WS2 nanostructures may have a potential application as an UV-visible photocatalyst.

  19. A theoretical analysis of the optical absorption properties in one-dimensional InAs/GaAs quantum dot superlattices

    SciTech Connect

    Kotani, Teruhisa; Birner, Stefan; Lugli, Paolo; Hamaguchi, Chihiro

    2014-04-14

    We present theoretical investigations of miniband structures and optical properties of InAs/GaAs one-dimensional quantum dot superlattices (1D-QDSLs). The calculation is based on the multi-band k·p theory, including the conduction and valence band mixing effects, the strain effect, and the piezoelectric effect; all three effects have periodic boundary conditions. We find that both the electronic and optical properties of the 1D-QDSLs show unique states which are different from those of well known single quantum dots (QDs) or quantum wires. We predict that the optical absorption spectra of the 1D-QDSLs strongly depend on the inter-dot spacing because of the inter-dot carrier coupling and changing strain states, which strongly influence the conduction and valence band potentials. The inter-miniband transitions form the absorption bands. Those absorption bands can be tuned from almost continuous (closely stacked QD case) to spike-like shape (almost isolated QD case) by changing the inter-dot spacing. The polarization of the lowest absorption peak for the 1D-QDSLs changes from being parallel to the stacking direction to being perpendicular to the stacking direction as the inter-dot spacing increases. In the case of closely stacked QDs, in-plane anisotropy, especially [110] and [11{sup ¯}0] directions also depend on the inter-dot spacing. Our findings and predictions will provide an additional degree of freedom for the design of QD-based optoelectronic devices.

  20. Optical absorption and photoluminescence properties of Dy3+ doped heavy metal borate glasses - Effect of modifier oxides

    NASA Astrophysics Data System (ADS)

    Sasi kumar, M. V.; Rajesh, D.; Balakrishna, A.; Ratnakaram, Y. C.

    2013-06-01

    The present paper aims at reporting the optical absorption and emission properties of Dy3+ doped alkali (Li, Na, K) and mixed alkali (Li-Na, Li-K, Na-K) heavy metal borate glasses. For these glasses X-ray diffraction (XRD), differential scanning calorimetry (DSC), optical absorption, emission and lifetime decay measurements were carried out. Glass transition temperatures are obtained from the DSC spectra. Judd-Ofelt theory has been used to derive the spectral intensities (f), Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6) and certain radiative properties. Using the Judd-Ofelt intensity parameters, radiative lifetimes (τR), branching ratios (β), integrated absorption cross-sections (Σ) and emission cross-sections (σP) were obtained. The variations in these parameters with the variation of glass matrix are discussed in detail. The decay lifetime of the 4F9/2 level has been measured from the decay profiles and compared with calculated lifetimes. From the emission spectra, chromacity color coordinates are calculated and indicated the white light emission for potassium glass matrices. It was observed that among various glass matrices, potassium glass matrix has exhibited large emission cross-section for 6F9/2 → 6H13/2 transition.

  1. The low-lying states and optical absorption properties of a hydrogenic impurity in a parabolic quantum dot modulation by applied electric field

    NASA Astrophysics Data System (ADS)

    Yuan, Jian-Hui; Zhang, Yan; Guo, Xinxia; Zhang, Jinjin; Mo, Hua

    2015-04-01

    Using the configuration-integration method, we investigated theoretically the low-lying states and optical absorption properties of a hydrogenic impurity in a parabolic quantum dot modulation by applied electric field. The low-lying states and optical absorption properties depend sensitively on the electric field F and the strength of the parabolic confinement ℏω0 . We discuss the linear and third-order nonlinear optical absorption coefficients of the dot (i) with the impurity ion and (ii) without the impurity ion. In the first case, the increase of the parabolic confinement ℏω0 (or the electric field F) can induce the blueshift (or redshift) of the peak of the absorption coefficient. Also the optical intensity can induce the increase of the third-order nonlinear optical absorption coefficients to weaken and even bleach the total optical absorption coefficients. Similar behavior has also been observed in the second case, but there is no redshift of the peak positions of the absorption coefficient with the increase of the electric field F. Compared with the second case, it is easily seen that there are the blueshifts of the peak of the absorption coefficients, which can be used as a technical means for detecting impurities.

  2. Absorption properties of identical atoms

    NASA Astrophysics Data System (ADS)

    Sancho, Pedro

    2013-09-01

    Emission rates and other optical properties of multi-particle systems in collective and entangled states differ from those in product ones. We show the existence of similar effects in the absorption probabilities for (anti)symmetrized states of two identical atoms. The effects strongly depend on the overlapping between the atoms and differ for bosons and fermions. We propose a viable experimental verification of these ideas.

  3. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Geon Joon; Sim, Geon Bo; Choi, Eun Ha; Kwon, Young-Wan; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-01

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  4. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    SciTech Connect

    Lee, Geon Joon Sim, Geon Bo; Choi, Eun Ha; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-14

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  5. Optical Absorption in Liquid Semiconductors

    NASA Astrophysics Data System (ADS)

    Bell, Florian Gene

    An infrared absorption cell has been developed which is suitable for high temperature liquids which have absorptions in the range .1-10('3) cm('-1). The cell is constructed by clamping a gasket between two flat optical windows. This unique design allows the use of any optical windows chemically compatible with the liquid. The long -wavelength limit of the measurements is therefore limited only by the choice of the optical windows. The thickness of the cell can easily be set during assembly, and can be varied from 50 (mu)m to .5 cm. Measurements of the optical absorption edge were performed on the liquid alloy Se(,1-x)Tl(,x) for x = 0, .001, .002, .003, .005, .007, and .009, from the melting point up to 475(DEGREES)C. The absorption was found to be exponential in the photon energy over the experimental range from 0.3 eV to 1.2 eV. The absorption increased linearly with concentration according to the empirical relation (alpha)(,T)(h(nu)) = (alpha)(,1) + (alpha)(,2)x, and the absorption (alpha)(,1) was interpreted as the absorption in the absence of T1. (alpha)(,1) also agreed with the measured absorption in 100% Se at corresponding temperatures and energies. The excess absorption defined by (DELTA)(alpha) = (alpha)(,T)(h(nu))-(alpha)(,1) was interpreted as the absorption associated with Tl and was found to be thermally activated with an activation energy E(,t) = 0.5 eV. The exponential edge is explained as absorption on atoms immersed in strong electric fields surrounding ions. The strong fields give rise to an absorption tail similar to the Franz-Keldysh effect. A simple calculation is performed which is based on the Dow-Redfield theory of absorption in an electric field with excitonic effects included. The excess absorption at low photon energies is proportional to the square of the concentration of ions, which are proposed to exist in the liquid according to the relation C(,i) (PROPORTIONAL) x(' 1/2)(.)e('-E)t('/kT), which is the origin of the thermal activation

  6. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Absorption Related to Electrochromism in Cubic Boron Nitride Single Crystals

    NASA Astrophysics Data System (ADS)

    Ren, Ce; Chen, Zhan-Guo; Jia, Gang; Liu, Xiu-Huan; Zhao, Jian-Xun; Wang, Shuang

    2009-06-01

    A unusual electrochromism is observed in amber cubic boron nitride (cBN) single crystals when breakdown possibly related to impurities and defects occurs. The electrochromism induces an abrupt increase in the absorption coefficient of the cBN crystals within the visible and infrared region. The change of the absorption coefficient of cBN crystal can be increased linearly by raising the current after the electrochromism occurs, whereas it is irrelevant to the polarization of the incident light. The absorption related to the electrochromism in the cBN single crystal has potential applications in designing and manufacturing electro-optical modulators, optical switches, and other optoelectric devices.

  7. Optical absorption and scattering properties of bulk porcine muscle phantoms from interstitial radiance measurements in 650-900 nm range

    NASA Astrophysics Data System (ADS)

    Grabtchak, Serge; Montgomery, Logan G.; Whelan, William M.

    2014-05-01

    We demonstrated the application of relative radiance-based continuous wave (cw) measurements for recovering absorption and scattering properties (the effective attenuation coefficient, the diffusion coefficient, the absorption coefficient and the reduced scattering coefficient) of bulk porcine muscle phantoms in the 650-900 nm spectral range. Both the side-firing fiber (the detector) and the fiber with a spherical diffuser at the end (the source) were inserted interstitially at predetermined locations in the phantom. The porcine phantoms were prostate-shaped with ˜4 cm in diameter and ˜3 cm thickness and made from porcine loin or tenderloin muscles. The described method was previously validated using the diffusion approximation on simulated and experimental radiance data obtained for homogenous Intralipid-1% liquid phantom. The approach required performing measurements in two locations in the tissue with different distances to the source. Measurements were performed on 21 porcine phantoms. Spectral dependences of the effective attenuation and absorption coefficients for the loin phantom deviated from corresponding dependences for the tenderloin phantom for wavelengths <750 nm. The diffusion constant and the reduced scattering coefficient were very close for both phantom types. To quantify chromophore presence, the plot for the absorption coefficient was matched with a synthetic absorption spectrum constructed from deoxyhemoglobin, oxyhemoglobin and water. The closest match for the porcine loin spectrum was obtained with the following concentrations: 15.5 µM (±30% s.d.) Hb, 21 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The tenderloin absorption spectrum was best described by 30 µM Hb (±30% s.d), 19 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The higher concentration of Hb in tenderloin was consistent with a dark-red appearance of the tenderloin phantom. The method can be applied to a number of biological

  8. Optical reflection, transmission and absorption properties of single-layer black phosphorus from a model calculation

    NASA Astrophysics Data System (ADS)

    Margulis, Vl A.; Muryumin, E. E.; Gaiduk, E. A.

    2016-05-01

    An effective anisotropic tight-binding model is developed to analytically describe the low-energy electronic structure and optical response of phosphorene (a black phosphorus (BP) monolayer). Within the framework of the model, we derive explicit closed-form expressions, in terms of elementary functions, for the elements of the optical conductivity tensor of phosphorene. These relations provide a convenient parametrization of the highly anisotropic optical response of phosphorene, which allows the reflectance, transmittance, and absorbance of this material to be easily calculated as a function of the frequency of the incident radiation at arbitrary angles of incidence. The results of such a calculation are presented for both a free-standing phosphorene layer and the phosphorene layer deposited on a {{SiO}}2 substrate, and for the two principal cases of polarization of the incident radiation either parallel to or normal to the plane of incidence. Our findings (e.g., a ‘quasi-Brewster’ effect in the reflectance of the phosphorene/{{SiO}}2 overlayer system) pave the way for developing a new, purely optical method of distinguishing BP monolayers.

  9. Optical Absorption and Scattering Properties of Normal and Defective Pickling Cucumbers for 700-1000 nm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Internal defect in pickling cucumbers can cause bloater damage during brining, which lowers the quality of final pickled products and results in economic loss for the pickle industry. Hence it is important to have an effective optical inspection system for detection and segregation of defective pick...

  10. Measurement of food optical properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical properties determine how a biological material or a food product will behave or interact with light. Absorption and scattering coefficients are the two primary optical properties characterizing turbid or diffusive food products. Measurement of the optical properties can provide useful inform...

  11. Periodically Diameter-Modulated Semiconductor Nanowires for Enhanced Optical Absorption.

    PubMed

    Ko, Minjee; Baek, Seong-Ho; Song, Bokyung; Kang, Jang-Won; Kim, Shin-Ae; Cho, Chang-Hee

    2016-04-01

    A diameter-modulated silicon nanowire array to enhance the optical absorption across broad spectral range is presented. Periodic shape engineering is achieved using conventional semiconductor processes and the unique optical properties are analyzed. The periodicity in the diameter of the silicon nanowires enables stronger and more closely spaced optical resonances, leading to broadband absorption enhancement. PMID:26833855

  12. Optical absorption in trilayer graphene

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Zhang, Fan; Niu, Qian

    2013-03-01

    We use a low energy effective model to analyze the optical responses of trilayer graphene samples. We first show that optical absorption of the ABA-stacked trilayer has strong dependence on both the Fermi energy and optical frequency, which is in sharp contrast to that of ABC-stacked trilayer graphene. Secondly, we are able to determine the possible existence of trigonal warping effects in the bandstructure of ABC-stacked trilayer graphene by a divergence in the absorption spectra at around 10 meV. In addition, we can partially distinguish the vairious broken symmetry states driven by electron-electron interactions in ABC-stacked trilayer graphene. In particular, the quantum anomalous Hall (QAH) state is sensitive to the polarization of the incident light, giving a way to detect its possible existence.

  13. Optical absorption and fluorescence properties of Er{sup 3+}/Yb{sup 3+} codoped lead bismuth alumina borate glasses

    SciTech Connect

    Goud, K. Krishna Murthy Reddy, M. Chandra Shekhar Rao, B. Appa

    2014-04-24

    Lead bismuth alumina borate glasses codoped with Er{sup 3+}/Yb{sup 3+} were prepared by melt quenching technique. Optical absorption, FTIR and photoluminescence spectra of these glasses have been studied. Judd-Ofelt theory has been applied to to the f ↔ f transitions for evaluating Ω{sub 2}, Ω{sub 4} and Ω{sub 6} parameters. Radiative properties like branching ratio β{sub r} and the radiative life time τ{sub R} have been determined on the basis of Judd-Ofelt theory. Upconversion emissions have been observed under 980nm laser excitation at room temperature. Green and red up-conversion emissions are centered at 530, 550 and 656 nm corresponding to {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2}, {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} and {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} transitions of Er{sup 3+} respectively. The results obtained are discussed quantitatively based on the energy transfer between Yb{sup 3+} and Er{sup 3+}.

  14. Microwave and optical saturable absorption in graphene.

    PubMed

    Zheng, Zhiwei; Zhao, Chujun; Lu, Shunbin; Chen, Yu; Li, Ying; Zhang, Han; Wen, Shuangchun

    2012-10-01

    We report on the first experiments on saturable absorption in graphene at microwave frequency band. Almost independent of the incident frequency, microwave absorbance of graphene always decreases with increasing the power and reaches at a constant level for power larger than 80 µW, evidencing the microwave saturable absorption property of graphene. Optical saturable absorption of the same graphene sample was also experimentally confirmed by an open-aperture Z-scan technique by one laser at telecommunication band and another pico-second laser at 1053 nm, respectively. Herein, we are able to conclude that graphene is indeed a broadband saturable absorber that can operate at both microwave and optical band. PMID:23188285

  15. Light absorption, optical and microphysical properties of trajectory-clustered aerosols at two AERONET sites in West Africa

    NASA Astrophysics Data System (ADS)

    Fawole, O. G.; Cai, X.; MacKenzie, A. R.

    2015-12-01

    Aerosol remote sensing techniques and back-trajectory modeling can be combined to identify aerosol types. We have clustered 7 years of AERONET aerosol signals using trajectory analysis to identify dominant aerosol sources at two AERONET sites in West Africa: Ilorin (4.34 oE, 8.32 oN) and Djougou (1.60 oE, 9.76 oN). Of particular interest are air masses that have passed through the gas flaring region in the Niger Delta area, of Nigeria, en-route the AERONET sites. 7-day back trajectories were calculated using the UK UGAMP trajectory model driven by ECMWF wind analyses data. Dominant sources identified, using literature classifications, are desert dust (DD), Biomass burning (BB) and Urban-Industrial (UI). Below, we use a combination of synoptic trajectories and aerosol optical properties to distinguish a fourth source: that due to gas flaring. Gas flaring, (GF) the disposal of gas through stack in an open-air flame, is believed to be a prominent source of black carbon (BC) and greenhouse gases. For these different aerosol source signatures, single scattering albedo (SSA), refractive index , extinction Angstrom exponent (EEA) and absorption Angstrom exponent (AAE) were used to classify the light absorption characteristics of the aerosols for λ = 440, 675, 870 and1020 nm. A total of 1625 daily averages of aerosol data were collected for the two sites. Of which 245 make up the GF cluster for both sites. For GF cluster, the range of fine-mode fraction is 0.4 - 0.7. Average values SSA(λ), for the total and GF clusters are 0.90(440), 0.93(675), 0.95(870) and 0.96(1020), and 0.93(440), 0.92(675), 0.9(870) and 0.9(1020), respectively. Values of for the GF clusters for both sites are 0.62 - 1.11, compared to 1.28 - 1.66 for the remainder of the clusters, which strongly indicates the dominance of carbonaceous particles (BC), typical of a highly industrial area. An average value of 1.58 for the real part of the refractive index at low SSA for aerosol in the GF cluster is also

  16. The role of scattering and absorption on the optical properties of birefringent polycrystalline ceramics: Modeling and experiments on ruby (Cr:Al2O3)

    NASA Astrophysics Data System (ADS)

    Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Basun, S. A.; Evans, D. R.; Garay, J. E.

    2016-01-01

    Light scattering due to birefringence has prevented the use of polycrystalline ceramics with anisotropic optical properties in applications such as laser gain media. However, continued development of processing technology has allowed for very low porosity and fine grains, significantly improving transparency and is paving the way for polycrystalline ceramics to be used in demanding optical applications. We present a method for producing highly transparent Cr3+ doped Al2O3 (ruby) using current activated pressure assisted densification. The one-step doping/densification process produces fine grained ceramics with well integrated (doped) Cr, resulting in good absorption and emission. In order to explain the light transmission properties, we extend the analytical model based on the Rayleigh-Gans-Debye approximation that has been previously used for undoped alumina to include absorption. The model presented captures reflection, scattering, and absorption phenomena in the ceramics. Comparison with measured transmission confirms that the model adequately describes the properties of polycrystalline ruby. In addition the measured emission spectra and emission lifetime are found to be similar to single crystals, confirming the high optical quality of the ceramics.

  17. Electronic structure and optical properties of CdS{sub x}Se{sub 1−x} solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

    SciTech Connect

    Murphy, M. W.; Yiu, Y. M. Sham, T. K.; Ward, M. J.; Liu, L.; Hu, Y.; Zapien, J. A.; Liu, Yingkai

    2014-11-21

    The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS{sub x}Se{sub 1−x} solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

  18. Optical diffusion property of cerumen from ear canal and correlation to metal content measured by synchrotron x-ray absorption

    NASA Astrophysics Data System (ADS)

    Holden, Todd; Dehipawala, Sumudu; Cheung, E.; Golebiewska, U.; Schneider, P.; Tremberger, G., Jr.; Kokkinos, D.; Lieberman, D.; Dehipawala, Sunil; Cheung, T.

    2012-03-01

    Human (and other mammals) would secrete cerumen (ear wax) to protect the skin of the ear canal against pathogens and insects. The studies of biodiversity of pathogen in human include intestine microbe colony, belly button microbe colony, etc. Metals such as zinc and iron are essentials to bio-molecular pathways and would be related to the underlying pathogen vitality. This project studies the biodiversity of cerumen via its metal content and aims to develop an optical probe for metal content characterization. The optical diffusion mean free path and absorption of human cerumen samples dissolved in solvent have been measured in standard transmission measurements. EXFAS and XANES have been measured at Brookhaven Synchrotron Light Source for the determination of metal contents, presumably embedded within microbes/insects/skin cells. The results show that a calibration procedure can be used to correlate the optical diffusion parameters to the metal content, thus expanding the diagnostic of cerumen in the study of human pathogen biodiversity without the regular use of a synchrotron light source. Although biodiversity measurements would not be seriously affected by dead microbes and absorption based method would do well, the scattering mean free path method would have potential to further study the cell based scattering centers (dead or live) via the information embedded in the speckle pattern in the deep-Fresnel zone.

  19. Wavelength-Dependent Optical Absorption Properties of Artificial and Atmospheric Aerosol Measured by a Multi-Wavelength Photoacoustic Spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Bozóki, Z.; Szabó, G.

    2014-12-01

    Various aspects of the photoacoustic (PA) detection method are discussed from the point of view of developing it into a routine tool for measuring the wavelength-dependent optical absorption coefficient of artificial and atmospheric aerosol. The discussion includes the issues of calibration, cross-sensitivity to gaseous molecules, background PA signal subtraction, and size-dependent particle losses within the PA system. The results in this paper are based on a recently developed four-wavelength PA system, which has operational wavelengths in the near-infrared, in the visible, and in the ultraviolet. The measured spectra of artificial and atmospheric aerosol prove the outstanding applicability of the presented PA system.

  20. Finding consistency between different views of the absorption enhancement of black carbon: An observationally constrained hybrid model to support a transition in optical properties with mass fraction

    NASA Astrophysics Data System (ADS)

    Coe, H.; Allan, J. D.; Whitehead, J.; Alfarra, M. R. R.; Villegas, E.; Kong, S.; Williams, P. I.; Ting, Y. C.; Haslett, S.; Taylor, J.; Morgan, W.; McFiggans, G.; Spracklen, D. V.; Reddington, C.

    2015-12-01

    The mixing state of black carbon is uncertain yet has a significant influence on the efficiency with which a particle absorbs light. In turn, this may make a significant contribution to the uncertainty in global model predictions of the black carbon radiative budget. Previous modelling studies that have represented this mixing state using a core-shell approach have shown that aged black carbon particles may be considerably enhanced compared to freshly emitted black carbon due to the addition of co-emitted, weakly absorbing species. However, recent field results have demonstrated that any enhancement of absorption is minor in the ambient atmosphere. Resolving these differences in absorption efficiency is important as they will have a major impact on the extent to which black carbon heats the atmospheric column. We have made morphology-independent measurements of refractory black carbon mass and associated weakly absorbing material in single particles from laboratory-generated diesel soot and black carbon particles in ambient air influenced by traffic and wood burning sources and related these to the optical properties of the particles. We compared our calculated optical properties with optical models that use varying mixing state assumptions and by characterising the behaviour in terms of the relative amounts of weakly absorbing material and black carbon in a particle we show a sharp transition in mixing occurs. We show that the majority of black carbon particles from traffic-dominated sources can be treated as externally mixed and show no absorption enhancement, whereas models assuming internal mixing tend to give the best estimate of the absorption enhancement of thickly coated black carbon particles from biofuel or biomass burning. This approach reconciles the differences in absorption enhancement previously observed and offers a systematic way of treating the differences in behaviour observed.

  1. Third-order nonlinear optical properties of colloidal Au nanorods systems: saturable and reverse-saturable absorption.

    PubMed

    García-Ramírez, E V; Almaguer-Valenzuela, S; Sánchez-Dena, O; Baldovino-Pantaleón, O; Reyes-Esqueda, J A

    2016-01-25

    In this work, we present a study of the nonlinear absorption properties from different gold nanorod (NR) systems in aqueous suspension. The NRs were obtained with the bottom-up protocol by the seed-mediated growth method (SMG), using Ag(+) ions at different concentrations, and CTAB as surfactant. By using this method, aspect ratios between 2 and 5 were obtained. The transverse surface plasmons (TSP) are located between 514 - 535 nm, while the longitudinal surface plasmons (LSP) are between 639 - 921 nm, for the different samples studied. The Z-scan technique was implemented for open (OA) and closed (CA) aperture at 532 and 1064 nm, with laser pulses of 26 ps, for vertical and horizontal polarizations, with respect to the incidence plane (horizontal). At 532 nm all samples showed saturable absorption (SA), while for samples with LSP near 1064 nm, such effect was observed only at low-energy pulse experimental conditions. In the high-energy pulse regime, an apparent reverse-saturable absorption (RSA) was observed for both wavelengths. However for 532 nm, it was possible to determine that this effect results from structural changes in the samples, which are manifested through the behavior of nonlinear absorption and refraction curves. These results were used to determine the irradiances to which NRs can be modified by photodegradation. PMID:26832569

  2. Effect of SnO addition on optical absorption of bismuth borate glass and photocatalytic property of the crystallized glass

    SciTech Connect

    Masai, Hirokazu; Fujiwara, Takumi; Mori, Hiroshi

    2008-04-07

    We have found that an addition of SnO in a bismuth-borate glass, CaO-B{sub 2}O{sub 3}-Bi{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-TiO{sub 2}, decreases the optical absorption coefficient in the visible region, in which selective crystallization of TiO{sub 2} was observed after heat treatment. Since selective crystallization of TiO{sub 2} was also attained in the SnO-containing glass, the transparency of TiO{sub 2} crystallized glass can be improved independently of selective crystallization of TiO{sub 2}. We have also demonstrated that the rutile-nanocrystallized glass with SnO addition shows a higher photocatalytic activity than the glass without SnO, indicating that this crystallized glass has a large potential for application as transparent photocatalytic materials.

  3. Luminescence and optical absorption properties of Nd(3+) ions in K-Mg-Al phosphate and fluorophosphate glasses.

    PubMed

    Surendra Babu, S; Babu, P; Jayasankar, C K; Joshi, A S; Speghini, A; Bettinelli, M

    2006-04-26

    Absorption and emission properties and fluorescence lifetimes for the [Formula: see text] transition of Nd(3+) ions embedded in P(2)O(5)-K(2)O-MgO-Al(2)O(3) (PKMA)-based glasses modified with AlF(3) and BaF(2) are reported at room temperature. The observed energy levels of Nd(3+) ions in these glasses have been analysed through a semi-empirical free-ion Hamiltonian model. The spin-orbit interaction and net electrostatic interaction experienced by the Nd(3+) ions follow the trend as PKMA>PKMA+AlF(3)> PKMA+BaF(2) glasses. Judd-Ofelt analysis has been carried out on the absorption spectra of 1.0 mol% Nd(3+)-doped glasses to predict the radiative properties for the fluorescent levels of the Nd(3+) ion. Branching ratios and stimulated emission cross-sections show that the [Formula: see text] transition of the glasses under investigation has the potential for laser applications. The Inokuti-Hirayama model has been applied to investigate the non-radiative relaxation of the Nd(3+) ion emitting state, (4)F(3/2). Based on the decay curve analysis, concentration quenching of the (4)F(3/2) emission has been attributed to a cross-relaxation process between the Nd(3+) ions. PMID:21690752

  4. A comparative study of optical absorption and photocatalytic properties of nanocrystalline single-phase anatase and rutile TiO{sub 2} doped with transition metal cations

    SciTech Connect

    Kernazhitsky, L.; Shymanovska, V.; Gavrilko, T.; Naumov, V.; Kshnyakin, V.; Khalyavka, T.

    2013-02-15

    The effect of nanocrystalline TiO{sub 2} doping with transition metal cations (Cu{sup 2+}, Fe{sup 3+}, Co{sup 2+}, Cr{sup 3+}) on their optical absorption and photocatalytic properties was investigated. The obtained metal-doped TiO{sub 2} samples were characterized by X-ray diffraction, scanning electron microscopy, and UV-vis absorption spectroscopy. It is shown that doping effect on anatase (A) and rutile (R) properties is quite different, being much stronger and complicated on A than on R. Contrary to doped R, doped A revealed a significant red shift of the absorption edge along with the band gap narrowing. Photocatalytic activity of anatase increases upon doping in the order: AR/Co>R/Cu>R/Fe>R/Cr, indicating the inhibitory effect of impurity cations. This fact correlates with the decrease in the UV absorption of the doped rutile in the region of the Hg-lamp irradiation at 4.88 eV. - Graphical abstract: A red shift of the absorption edge of nanocrystalline single-phase anatase after doping with transition metal cations. Highlights: Black-Right-Pointing-Pointer Single-phase anatase and rutile powders surface-doped with transition metal cations. Black-Right-Pointing-Pointer Absorption edge and band gap of rutile do not change with surface doping. Black-Right-Pointing-Pointer Band gap of surface-doped anatase reduces being the lowest for A/Fe. Black-Right-Pointing-Pointer The surface-doping improves photocatalytic activity of anatase. Black-Right-Pointing-Pointer The surface-doping inhibits photocatalytic activity of rutile.

  5. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies.

    PubMed

    El-Shishtawy, Reda M; Elroby, Shaaban A; Asiri, Abdullah M; Müllen, Klaus

    2016-01-01

    The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1-SQD4) were investigated using density functional theory (DFT) and time-dependent (TD-DFT) density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0)), and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh) with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO) were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (-4.26 eV) of the conduction band of TiO₂ nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO₂ in dye-sensitized solar cells (DSSCs). Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices. PMID:27043556

  6. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies

    PubMed Central

    El-Shishtawy, Reda M.; Elroby, Shaaban A.; Asiri, Abdullah M.; Müllen, Klaus

    2016-01-01

    The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1–SQD4) were investigated using density functional theory (DFT) and time-dependent (TD-DFT) density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0)), and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh) with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO) were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (−4.26 eV) of the conduction band of TiO2 nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO2 in dye-sensitized solar cells (DSSCs). Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices. PMID:27043556

  7. Synthesis, characterization and nonlinear absorption of novel octakis-POSS substituted metallophthalocyanines and strong optical limiting property of CuPc.

    PubMed

    Ceyhan, Tanju; Yüksek, Mustafa; Yağlioğlu, H Gül; Salih, Bekir; Erbil, Mehmet K; Elmali, Ayhan; Bekaroğlu, Ozer

    2008-05-14

    In this study, the preparation of some novel metallophthalocyanine (MPcs) complexes substituted with octakis(mercaptopropylisobutyl-POSS) functional group was achieved. By the reaction of [1-(3-mercapto)propyl-3,5,7,9,11,13,15-isobutylpentacyclo[9.5.1.1(3,9).1(5,15).1(7,13)]octasiloxane 1 with 4,5-dichloro-1,2-dicyanobenzene 2 in THF as the solvent in the presence of K2CO3 as the base, the phthalonitrile derivative 3 was synthesized. Compound 3 reacted with CoCl2 x 6H2O in ethylene glycol to furnish a novel cobalt(II) phthalocyanine . The tetramerization of 3 with urea and CuCl in the absence of solvent gave the novel Cu(II) phthalocyanine 4; while with Zn(OAc)2 x 2H2O in dry DMF gave the novel zinc(ii) phthalocyanine 6. The structures of the target compounds were confirmed by elemental analysis, UV/VIS, IR, MALDI-TOF MS and 1H NMR spectra. Nonlinear absorptions of MPcs in chloroform solution were investigated by using Z-scan measurement technique with 4 ns pulses at 532 nm wavelength. While CuPc 5 showed very high nonlinear absorption, MPcs 4 and 6 did not show considerable nonlinear absorption. Investigations of optical limiting properties of 5 revealed that this material is a very good candidate for optical limiting applications. PMID:18461195

  8. Synthesis and nonlinear optical absorption of novel chalcone derivative compounds

    NASA Astrophysics Data System (ADS)

    Rahulan, K. Mani; Balamurugan, S.; Meena, K. S.; Yeap, G.-Y.; Kanakam, Charles C.

    2014-03-01

    3-(4-(dimethylamino)phenyl)-1-(4-(4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl)phenyl)prop-2-en-1-one was synthesized and its third order nonlinear optical properties have been investigated using a z-scan technique with nanosecond laser pulses at 532 nm. The nonlinear absorption behavior of the compound in chloroform presents a distinct difference at different laser intensity. Interestingly, the compound showed a switchover from saturable absorption (SA) to reverse saturable absorption (RSA) with the increase of excitation intensity. Our studies suggest that compound could be used as a potential candidate for optical device applications such as optical limiters.

  9. Absorption Optics of Aqueous Foams

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Ranjini; Gittings, Alex; Durian, D. J.

    2002-11-01

    Aqueous foams are composed of gas bubbles packed together in a small volume of soapy water. The large number of gas-liquid interfaces in foams results in very strong scattering of light, which explains the opaque nature of conventional aqueous foams such as shaving foams and mousse. For dry foams, the interfaces can take the following three forms: the soap films where two bubbles meet, the triangular plateau borders where three soap films meet and the vertices where four plateau borders meet. Previous experiments have shown that most of the scattering occurs from the plateau borders 2,3 and the transport mean free path of light (l*), the bubble radius (R) and the liquid fraction of foam (epsilon) is related through the relation l*=R/(epsilon0.5). To understand the reflection and scattering of light at the gas-bubble interfaces, we study the absorption of photons in the liquid network as a function of the foam absorptivity. We do this to confirm if the time spent by the photons in the liquid phase is proportional to the liquid fraction of the foam. Our results indicate that for a specific range of liquid fractions (0.05 is less than e is less than 0.1), the photons seem to get trapped in the liquid network. This result is independent of the absorptivity of the foam and leads us to conclude that under appropriate conditions, an aqueous foam behaves very much like an optical fiber network. Aqueous foam is generated in the lab by the method of turbulent mixing of N2 gas with a jet of alpha-olefin-sulfonate (AOS) solution. The foam has been made absorbing by dissolving small quantities of rhodamine dye (R = 0.005 g/l, R = 0.01 g/l and R = 0.0124 g/l) in the AOS solution. The transmission of photons through the foams of liquid fractions 0.0297 is less than e is less than 0.35 has been studied using Diffuse Transmission Spectroscopy (DTS). For each liquid fraction, the transport mean free path l* (the length over which the photon travels before it gets completely

  10. Nonlinear absorption, nonlinear scattering, and optical limiting properties of MoS2-ZnO composite-based organic glasses.

    PubMed

    Qu, Bin; Ouyang, Qiuyun; Yu, Xianbo; Luo, Wenhe; Qi, Lihong; Chen, Yujin

    2015-02-28

    MoS2-ZnO composites were synthesized using a solution-based method. The scanning electron microscopy and transmission electron microscopy analysis demonstrated that ZnO nanoparticles with a size of about 4.5 nm were coated on the basal surface of MoS2 nanosheets with an expanded spacing of the (002) plane. The MoS2-ZnO composite-based poly(methyl methacrylate) (PMMA) organic glasses (MoS2-ZnO-PMMA organic glasses) were prepared through a polymerization process. The nonlinear absorption (NLA), nonlinear scattering (NLS), and optical limiting (OL) properties of the MoS2-ZnO-PMMA organic glasses with different amounts of MoS2-ZnO were investigated using a modified Z-scan technique. Compared to MoS2-PMMA and ZnO-PMMA organic glasses, the MoS2-ZnO-PMMA organic glasses exhibited enhanced NLA, NLS, and OL properties, which were attributed to the interfacial charge transfer between MoS2 nanosheets and ZnO nanoparticles, the layered structure of MoS2 nanosheets, the small size effect of ZnO nanoparticles, and the local field effect. In addition, a changeover from saturable absorption (SA) to reverse saturable absorption (RSA) could be realized in the MoS2-ZnO-PMMA organic glasses by adjusting the input energy. The total nonlinear extinction coefficient and response time of the MoS2-ZnO-PMMA organic glasses could be up to 2380 cm GW(-1) and several hundred picoseconds, respectively. Compared to the MoS2 films, the MoS2-ZnO-PMMA organic glasses have higher optical damage threshold, better mechanical strength and flexibility. Thus the MoS2-ZnO-PMMA organic glasses are very promising for optical devices such as optical limiters, optical shutters, ultrafast lasers, and ultrafast optical switches. PMID:25642471

  11. The effect of Ni pre-implantation on surface morphology and optical absorption properties of Ag nanoparticles embedded in SiO2

    NASA Astrophysics Data System (ADS)

    Shen, Yanyan; Qi, Ting; Qiao, Yu; Yu, Shengwang; Hei, Hongjun; He, Zhiyong

    2016-02-01

    The effect of Ni ion fluence on Ag nucleation and particle growth was investigated by sequentially implantation of 60 keV Ni ions at fluences of 1 × 1016, 5 × 1016, 1 × 1017 ions/cm2 and 70 keV Ag ions at a fluence of 5 × 1016 ions/cm2. Due to the modification of the deposition and accumulation process of Ag implants caused by Ni pre-implantation, the surface morphology, structures, and optical absorption properties of the Ag nanoparticles (NPs) depends strongly on the Ni fluences. UV-vis absorption spectroscopy study showed that the introducing of Ni atoms lead to intensity decrease in the Ag SPR band. Remarkable local concentration increase of Ag profiles appeared for the sample pre-implanted by Ni ions of 5.0 × 1016 ions/cm2. In particular, the AgNi alloy NPs with dual absorption peaks centered at 406 nm and 563 nm have been formed after 600 °C annealing in Ar atmosphere. However, at a low fluence of 1.0 × 1016 ions/cm2, only small increase of the local Ag concentration than the Ag ions singly implanted sample can be observed. At a high fluence of 1.0 × 1017 ions/cm2, lots Ag atoms are trapped close to the surface, which result in heavy sputtering loss of Ag atoms and the sublimation of Ag atoms after 600 °C annealing.

  12. Two-photon absorption in tetraphenylporphycenes: are porphycenes better candidates than porphyrins for providing optimal optical properties for two-photon photodynamic therapy?

    PubMed

    Arnbjerg, Jacob; Jiménez-Banzo, Ana; Paterson, Martin J; Nonell, Santi; Borrell, José I; Christiansen, Ove; Ogilby, Peter R

    2007-04-25

    Porphycenes are structural isomers of porphyrins that have many unique properties and features. In the present work, the resonant two-photon absorption of 2,7,12,17-tetraphenylporphycene (TPPo) and its palladium(II) complex (PdTPPo) has been investigated. The data obtained are compared to those from the isomeric compound, meso-tetraphenylporphyrin (TPP). Detection of phosphorescence from singlet molecular oxygen, O2(a(1)Delta(g)), produced upon irradiation of these compounds, was used to obtain two-photon excitation spectra and to quantify two-photon absorption cross sections, delta. In the spectral region of 750-850 nm, the two-photon absorption cross sections at the band maxima for both TPPo and PdTPPo, delta = 2280 and 1750 GM, respectively, are significantly larger than that for TPP. This difference is attributed to the phenomenon of so-called resonance enhancement; for the porphycenes, the two-photon transition is nearly resonant with a comparatively intense one-photon Q-band transition. The results of quantum mechanical calculations using density functional quadratic response theory are in excellent agreement with the experimental data and, as such, demonstrate that comparatively high-level quantum chemical methods can be used to interpret and predict nonlinear optical properties from such large molecular systems. One important point realized through these experiments and calculations is that one must exercise caution when using qualitative molecular-symmetry-derived arguments to predict the expected spectral relationship between allowed one- and two-photon transitions. From a practical perspective, this study establishes that, in comparison to porphyrins and other tetrapyrrolic macrocyclic systems, porphycenes exhibit many desirable attributes for use as sensitizers in two-photon initiated photodynamic therapy. PMID:17397157

  13. Optical absorption and scattering properties of bulk porcine muscle phantoms from interstitial radiance measurements in 650-900 nm range.

    PubMed

    Grabtchak, Serge; Montgomery, Logan G; Whelan, William M

    2014-05-21

    We demonstrated the application of relative radiance-based continuous wave (cw) measurements for recovering absorption and scattering properties (the effective attenuation coefficient, the diffusion coefficient, the absorption coefficient and the reduced scattering coefficient) of bulk porcine muscle phantoms in the 650-900 nm spectral range. Both the side-firing fiber (the detector) and the fiber with a spherical diffuser at the end (the source) were inserted interstitially at predetermined locations in the phantom. The porcine phantoms were prostate-shaped with ∼4 cm in diameter and ∼3 cm thickness and made from porcine loin or tenderloin muscles. The described method was previously validated using the diffusion approximation on simulated and experimental radiance data obtained for homogenous Intralipid-1% liquid phantom. The approach required performing measurements in two locations in the tissue with different distances to the source. Measurements were performed on 21 porcine phantoms. Spectral dependences of the effective attenuation and absorption coefficients for the loin phantom deviated from corresponding dependences for the tenderloin phantom for wavelengths <750 nm. The diffusion constant and the reduced scattering coefficient were very close for both phantom types. To quantify chromophore presence, the plot for the absorption coefficient was matched with a synthetic absorption spectrum constructed from deoxyhemoglobin, oxyhemoglobin and water. The closest match for the porcine loin spectrum was obtained with the following concentrations: 15.5 µM (±30% s.d.) Hb, 21 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The tenderloin absorption spectrum was best described by 30 µM Hb (±30% s.d), 19 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The higher concentration of Hb in tenderloin was consistent with a dark-red appearance of the tenderloin phantom. The method can be applied to a number of

  14. Preparation of Few-Layer Bismuth Selenide by Liquid-Phase-Exfoliation and Its Optical Absorption Properties

    PubMed Central

    Sun, Liping; Lin, Zhiqin; Peng, Jian; Weng, Jian; Huang, Yizhong; Luo, Zhengqian

    2014-01-01

    Bismuth selenide (Bi2Se3), a new topological insulator, has attracted much attention in recent years owing to its relatively simple band structure and large bulk band gap. Compared to bulk, few-layer Bi2Se3 is recently considered as a highly promising material. Here, we use a liquid-phase exfoliation method to prepare few-layer Bi2Se3 in N-methyl-2-pyrrolidone or chitosan acetic solution. The resulted few-layer Bi2Se3 dispersion demonstrates an interesting absorption in the visible light region, which is different from bulk Bi2Se3 without any absorption in this region. The absorption spectrum of few-layer Bi2Se3 depends on its size and layer number. At the same time, the nonlinear and saturable absorption of few-layer Bi2Se3 thin film in near infrared is also characterized well and further exploited to generate laser pulses by a passive Q-switching technique. Stable Q-switched operation is achieved with a lower pump threshold of 9.3 mW at 974 nm, pulse energy of 39.8 nJ and a wide range of pulse-repetition-rate from 6.2 to 40.1 kHz. Therefore, the few-layer Bi2Se3 may excite a potential applications in laser photonics and optoelectronic devices. PMID:24762534

  15. Geometrical interpretation of optical absorption

    SciTech Connect

    Monzon, J. J.; Barriuso, A. G.; Sanchez-Soto, L. L.; Montesinos-Amilibia, J. M.

    2011-08-15

    We reinterpret the transfer matrix for an absorbing system in very simple geometrical terms. In appropriate variables, the system appears as performing a Lorentz transformation in a (1 + 3)-dimensional space. Using homogeneous coordinates, we map that action on the unit sphere, which is at the realm of the Klein model of hyperbolic geometry. The effects of absorption appear then as a loxodromic transformation, that is, a rhumb line crossing all the meridians at the same angle.

  16. Analytical modeling and experimental investigation on optical properties of new class of nanofluids (Al2O3-CuO binary nanofluids) for direct absorption solar thermal energy

    NASA Astrophysics Data System (ADS)

    Menbari, Amir; Alemrajabi, Ali Akbar

    2016-02-01

    Nanofluids play a major role in many modern engineering processes. Binary nanofluids are a new class of nanofluids that are prepared by dispersing simultaneously two dissimilar nanoparticles in a base fluid. They offer a good potential for use in direct absorption solar systems. The present study investigates both experimentally and analytically the optical properties of binary nanofluids for direct absorption in solar applications. For this purpose, two dissimilar nanoparticles, i.e. CuO and γ-Al2O3, are dispersed in water, ethylene glycol, and the ethylene glycol-water mixture to form binary nanofluids. In addition, a new method is developed for calculating the extinction coefficient of the binary nanofluids based on the classical electromagnetic theory. It will be shown that the extinction coefficients obtained from both analytical and experimental studies are in good agreement. Moreover, the extinction coefficient of the binary nanofluids is found to be approximately equal to the sum of the extinction coefficients of the constituent components, determined both analytically and experimentally. By increasing the nanoparticle volume fraction, improvements are observed in the extinction coefficient of the binary nanofluids prepared. Also, the analytical and experimental results of the study show that the extinction coefficient of the binary nanoparticles dispersed in water as the "base fluid" is greater than those of the binary nanoparticles dispersed in ethylene glycol or the mixture of ethylene glycol-water.

  17. Optical properties of human hair

    NASA Astrophysics Data System (ADS)

    Altshuler, Gregory B.; Ilyasov, Ildar K.; Prikhodko, Constantin V.

    1995-01-01

    Optical properties of human hair are the subject of great interest for the realization of any possible cosmetic applications. This paper represents the results of hair microstructure as an optical substance investigation, indicates melanin and keratin absorption spectra, and shows experimentally discovered anisotropia of optical properties of human hair. Radiation weakening coefficient value at the range from 450 up to 800 nm is estimated. Thresholds of hair destruction by Nd, Ho, Cu, and Er laser radiation are obtained. Perspectives of laser application for epilation and other medical purposes are evaluated.

  18. Further advancement of differential optical absorption spectroscopy: theory of orthogonal optical absorption spectroscopy.

    PubMed

    Liudchik, Alexander M

    2014-08-10

    A modified version of the differential optical absorption spectroscopy (DOAS) method is presented. The technique is called orthogonal optical absorption spectroscopy (OOAS). A widespread variant of DOAS with smoothing of the registered spectrum and absorption cross sections being made employing a polynomial regression is a particular case of OOAS. The concept of OOAS provides a variety of new possibilities for constructing computational schemes and analyzing the influence of different error sources on calculated concentrations. PMID:25320931

  19. Single-molecule imaging by optical absorption

    NASA Astrophysics Data System (ADS)

    Celebrano, Michele; Kukura, Philipp; Renn, Alois; Sandoghdar, Vahid

    2011-02-01

    To date, optical studies of single molecules at room temperature have relied on the use of materials with high fluorescence quantum yield combined with efficient spectral rejection of background light. To extend single-molecule studies to a much larger pallet of substances that absorb but do not fluoresce, scientists have explored the photothermal effect, interferometry, direct attenuation and stimulated emission. Indeed, very recently, three groups have succeeded in achieving single-molecule sensitivity in absorption. Here, we apply modulation-free transmission measurements known from absorption spectrometers to image single molecules under ambient conditions both in the emissive and strongly quenched states. We arrive at quantitative values for the absorption cross-section of single molecules at different wavelengths and thereby set the ground for single-molecule absorption spectroscopy. Our work has important implications for research ranging from absorption and infrared spectroscopy to sensing of unlabelled proteins at the single-molecule level.

  20. Coherent perfect absorption in nonlinear optics

    NASA Astrophysics Data System (ADS)

    Zheng, Yuanlin; Wan, Wenjie; Chen, Xianfeng

    2013-02-01

    Recently, a concept of time reversed lasing or coherent perfect absorber (CPA) has been proposed by A. D. Stone and co-workers, and was shortly experimentally demonstrated by them. The CPA system is illuminated coherently and monochromatically by the time reverse of the output of a lasing mode and the incident radiation is perfectly absorbed. Shortly afterwards, Stefano Longhi extended the idea to realize a CPA for colored incident light, and have theoretically shown that the time reversal of optical parametric oscillation (OPO) in a nonlinear medium could also realize a colored CPA for incident signal and idler fields which can be seemed as a kind of nonlinear CPA. Here we present the realization of such time-reversed processes in nonlinear optics regime, including time-reversed second harmonic generation (SHG) for coherent absorption at harmonic frequency of the pump and time-reversed optical parametric amplification (OPA) for coherent attenuation of colored travelling optical fields. Time reversed SHG is carried out at both phase matching and mismatching conditions, which shows parametric near perfect absorption at the harmonic frequency of the pump. The time reversal of OPA is demonstrated experimentally in a nonlinear medium to form a coherent absorber for perpendicularly polarized signal and idler travelling waves, realizing in the condition of OPA by a type II phase matching scheme. The absorption of signal/idler pair occurs at some specific phase difference. This is the first experimental demonstration of coherent absorption processes in nonlinear optics regime.

  1. Absorption-edge calculations of inorganic nonlinear optical crystals

    NASA Astrophysics Data System (ADS)

    Wu, Kechen; Chen, Chuangtian

    1992-03-01

    A theoretical model suitable for calculating absorption edges of inorganic nonlinear optical (NLO) crystals is introduced. This model is proved to be useful to elucidate the relationship between electronic structures of NLO-active groups and macroscopic properties of absorption edges on the UV side of most of the inorganic nonlinear optical crystals. A systematic calculation of absorption edges on the UV side for several important inorganic NLO crystals is carried out by means of DV-SCM-Xα method and all calculated results are in good agreement with experimental data. These inorganic NLO crystals include LiB3O5(LBO), β-BaB2O4(BBO), KB5, KDP, Na2SbF5, Ba2TiSi2O8, iodate and NaNO2. The calculated energy level structures of LiB3O5 and β-BaB2O4 crystals are compared with the measured XPS spectra. The unusual transparent spectra of KB5 and KDP crystals are partly explained from the microstructure point of view. The effect of lone electron pair in iodate and NaNO2 crystals on their absorption edges are discussed. All these results show that Anionic Group Theory of Nonlinear Optical Crystals is useful to evaluate the absorption edges of the inorganic nonlinear optical crystal and is a powerful tool in a Molecular Engineering approach to search for new nonlinear optical materials.

  2. Neutron scattering and absorption properties

    SciTech Connect

    Holden, N.E.

    1993-12-01

    The Table in this report presents an evaluated set of values for the experimental quantities, which characterize the properties for scattering and absorption of neutrons. The neutron cross section is given for room temperature neutrons, 20.43{degree}C, corresponds to a thermal neutron energy of 0.0253 electron volts (eV) or a neutron velocity of 2200 meters/second. The neutron resonance integral is defined over the energy range from 0.5 eV to 0.1 {times} 10{sup 6} eV, or 0.1 MeV. A list of the major references used is given below. The literature cutoff data is October 1993. Uncertainties are given in parentheses. Parentheses with two or more numbers indicate values to the excited states(s) and to the ground state of the product nucleus.

  3. Evolution of linear absorption and nonlinear optical properties in V-shaped ruthenium(II)-based chromophores.

    PubMed

    Coe, Benjamin J; Foxon, Simon P; Harper, Elizabeth C; Helliwell, Madeleine; Raftery, James; Swanson, Catherine A; Brunschwig, Bruce S; Clays, Koen; Franz, Edith; Garín, Javier; Orduna, Jesús; Horton, Peter N; Hursthouse, Michael B

    2010-02-10

    In this article, we describe a series of complexes with electron-rich cis-{Ru(II)(NH(3))(4)}(2+) centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845-4859). They have been isolated as their PF(6)(-) salts and characterized by using various techniques including (1)H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru(III/II) waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities beta have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d --> pi* metal-to-ligand charge-transfer (MLCT) and pi --> pi* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant beta(0) responses as high as ca. 600 x 10(-30) esu. These pseudo-C(2v) chromophores show two substantial components of the beta tensor, beta(zzz) and beta(zyy), although the relative significance of these varies with the physical method applied. According to HRS, beta(zzz) dominates in all cases, whereas the Stark analyses indicate that beta(zyy) is dominant in the shorter chromophores, but beta(zzz) and beta(zyy) are similar for the extended species. In contrast, finite field calculations predict that beta(zyy) is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand pi-systems are extended. Such unusual

  4. Absorption characteristics of optically complex inland waters: Implications for water optical classification

    NASA Astrophysics Data System (ADS)

    Shi, Kun; Li, Yunmei; Li, Lin; Lu, Heng

    2013-06-01

    Multiple bio-optical measurements were conducted in inland waters of China, including Lake Taihu [spring and autumn], Lake Chaohu, Lake Dianchi, and Three Gorges Reservoirs. The variations in the absorption characteristics of chromophoric dissolved organic matter (CDOM), phytoplankton, and non-algal particles (NAP) and their relative contributions to total absorption among these waters were analyzed. The obtained results indicated that these areas are representative of the optically complex inland waters characterized by strong regional variations of their absorption properties. By means of the relative contributions of NAP and phytoplankton to the total water absorption at 550 and 675 nm, these waters were classified into three optical water types, each one having specific biogeochemical and optical properties. Two of the types were distinct and corresponded to waters that are optically controlled by NAP (Type I) and dominated by phytoplankton (Type III). Type II was related to relatively optically mixed waters where the absorption properties are controlled by NAP and phytoplankton. Additionally, the differences in remote-sensing reflectance (Rrs) spectra among the three classified water types were clarified to establish optical criteria for identifying these water types. On this basis, the classification criteria for MERIS images were developed, which allowed one to cluster every Rrs spectrum into one of the three water types by comparing the values from band 6, band 8, and band 9 of MERIS images. The proposed criteria were subsequently conducted to map the water types of Lake Taihu using MERIS images.

  5. Engineering optical properties of semiconductor metafilm superabsorbers

    NASA Astrophysics Data System (ADS)

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2016-04-01

    Light absorption in ultrathin layer of semiconductor has been considerable interests for many years due to its potential applications in various optical devices. In particular, there have been great efforts to engineer the optical properties of the film for the control of absorption spectrums. Whereas the isotropic thin films have intrinsic optical properties that are fixed by materials' properties, metafilm that are composed by deep subwavelength nano-building blocks provides significant flexibilities in controlling the optical properties of the designed effective layers. Here, we present the ultrathin semiconductor metafilm absorbers by arranging germanium (Ge) nanobeams in deep subwavelength scale. Resonant properties of high index semiconductor nanobeams play a key role in designing effective optical properties of the film. We demonstrate this in theory and experimental measurements to build a designing rule of efficient, controllable metafilm absorbers. The proposed strategy of engineering optical properties could open up wide range of applications from ultrathin photodetection and solar energy harvesting to the diverse flexible optoelectronics.

  6. Enhanced optical properties of heterostructured ZnO/CeO2 nanocomposite fabricated by one-pot hydrothermal method: Fluorescence and ultraviolet absorption and visible light transparency

    NASA Astrophysics Data System (ADS)

    He, Geping; Fan, Huiqing; Wang, Zhiwei

    2014-12-01

    Many researchers investigated the properties of either discrete metal oxide CeO2 or ZnO materials. However, less attention has been paid to the various nanostructure and performances of CeO2 and ZnO nanocomposite up to now. In this paper, a facile and low cost one-pot hydrothermal synthesis method has been adopted to obtained directly precursors of CeCO3OH and Zn5(CO3)2(OH)6 with different Ce atom molar ratios to Zn, which are transformed into their corresponding metal oxide to form the ZnO/CeO2 heterostructure nanocomposites (HSNCs) by pyrolysis. The heterostructure is composed of ZnO and CeO2 monocrystals, simultaneously, CeO2 monocrystals are well dispersed on the surface of ZnO monocrystal for cosmetics. Bing dependent on the analysis results of XRD and TEM for the obtained precursors before and after pyrolysis, the formation mechanism of HSNCs was proposed. To the best of our knowledge, the paper first reported heterostructured ZnO/CeO2 nanocomposite grown in one-pot mixed aqueous solution of cerium nitrate, zinc acetate and urea without other extra surfactant. Additionally, the influence of various Ce/Zn molar ratios on the heterostructure, fluorescence emission and UV-visible absorption properties of HSNCs was investigated in detail. ZnO/CeO2 HSNCs display higher fluorescence emission with the increasing Ce/Zn molar ratio. Meanwhile, the larger Ce/Zn molar ratio of ZnO/CeO2 HSNCs, the stronger transparency in the visible light region and the weaker UV absorption. The results are due to the fact that the band gap of ZnO/CeO2 HSNCs will decrease from 3.25 to 3.08 eV when Ce/Zn atom molar ratio is increased from 0 to 0.08. By the comprehensive analysis on the optical performances of HSNCs with the different Ce/Zn atom molar ratios, ZnO/CeO2-0.04 HSNCs could become UV absorber materials and transparent material in the visible region. ZnO/CeO2-0.04 HSNCs with the UV-filtering and Vis-transparent properties is appropriate for personal-care cosmetics.

  7. Aerosol optical absorption measurements with photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Kun; Wang, Lei; Liu, Qiang; Wang, Guishi; Tan, Tu; Zhang, Weijun; Chen, Weidong; Gao, Xiaoming

    2015-04-01

    Many parameters related to radiative forcing in climate research are known only with large uncertainties. And one of the largest uncertainties in global radiative forcing is the contribution from aerosols. Aerosols can scatter or absorb the electromagnetic radiation, thus may have negative or positive effects on the radiative forcing of the atmosphere, respectively [1]. And the magnitude of the effect is directly related to the quantity of light absorbed by aerosols [2,3]. Thus, sensitivity and precision measurement of aerosol optical absorption is crucial for climate research. Photoacoustic spectroscopy (PAS) is commonly recognized as one of the best candidates to measure the light absorption of aerosols [4]. A PAS based sensor for aerosol optical absorption measurement was developed. A 532 nm semiconductor laser with an effective power of 160 mW was used as a light source of the PAS sensor. The PAS sensor was calibrated by using known concentration NO2. The minimum detectable optical absorption coefficient (OAC) of aerosol was determined to be 1 Mm-1. 24 hours continues measurement of OAC of aerosol in the ambient air was carried out. And a novel three wavelength PAS aerosol OAC sensor is in development for analysis of aerosol wavelength-dependent absorption Angstrom coefficient. Reference [1] U. Lohmann and J. Feichter, Global indirect aerosol effects: a review, Atmos. Chem. Phys. 5, 715-737 (2005) [2] M. Z. Jacobson, Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols, Nature 409, 695-697 (2001) [3] V. Ramanathan and G. Carmichae, Global and regional climate changes due to black carbon, nature geoscience 1, 221-227 (2008) [4] W.P Arnott, H. Moosmuller, C. F. Rogers, T. Jin, and R. Bruch, Photoacoustic spectrometer for measuring light absorption by aerosol: instrument description. Atmos. Environ. 33, 2845-2852 (1999).

  8. Prediction of Apple Quality by Optical Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical properties (i.e., absorption and scattering) are useful for assessing the internal quality of apples such as firmness and soluble solids content (SSC). A spatially-resolved hyperspectral imaging technique was developed to measure the optical properties of apples for predicting fruit firmness...

  9. Optical properties of flyash

    SciTech Connect

    Self, S.A.

    1989-07-01

    The purpose of this task is to validate the whole approach adopted in this program. Specifically, this bench-scale experiment is intended to compare the measured optical/radiative properties of a dispersion of well characterized ash with those calculated on the basis of the known size/composition distribution using the correlation formulae relating the composition and complex refractive index resulting from measurements on bulk samples of synthetic slag. Considerable thought has been given to the various possible approaches to satisfying the objectives of this task. Several experiments were done to guide our design of an apparatus for measuring the scattering and absorption properties of dispersions of flyash. As a result of these experiments, and from extensive prior experience in connection with research on electrostatic precipitation, it has been determined that there is no satisfactory way to satisfy the aims of this task using a gaseous dispersion of flyash because it is not possible to adequately disperse and deagglomerate flyash into a gas stream. Unless the ash is adequately dispersed, as it exists in the radiant boiler of a pulverized coal-fired combustion system, one cannot expect calculations, based on Mie calculations for a dispersion of spheres to properly agree with laboratory measurements. For these reasons, our design efforts are based on making measurements on a dispersion of flyash in liquid, for which our experience shows we can obtain stable, well-deagglomerated dispersions of ash. Because there is not single liquid which is adequately transparent over the wavelength range 1--12 {mu}m, we plan to use a combination of three liquids, C Cl{sub 4}, C S{sub 2} and bromoform to cover the full range. Windows of BaF{sub 2} will be used to contain the liquid suspension in an absorption/scattering cell.

  10. Soot Optical Property Study

    NASA Technical Reports Server (NTRS)

    Aung, K. T.; Hassan, M. I.; Krishnan, S. S.; Lin, K.-C.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2001-01-01

    Recent past studies of soot reaction processes in laminar premixed and nonpremixed flames generally have used the intrusive technique of thermophoretic sampling and analysis by transmission electron microscopy (TEM) to observe soot structure and obtain important fundamental information about soot particle properties, such as soot primary particle diameters, the rate of change of soot primary particle diameter as a function of time (or rate of soot surface growth or oxidation), the amount of soot particle reactive surface area per unit volume, the number of primary soot particles per unit volume, and the rate of formation of primary soot particles (or the rate of soot primary particle nucleation). Given the soot volume per unit volume of the flame (or the soot volume fraction), all these properties are readily found from a measurement of the soot primary particle diameter (which usually is nearly a constant for each location within a laminar flame). This approach is not possible within freely propagating flames, however, because soot properties at given positions in such flames vary relatively rapidly as a function of time in the soot formation and oxidation regions compared to the relatively lengthy sampling times needed to accumulate adequate soot samples and to minimize effects of soot collected on the sampling grid as it moves to and from the sampling position through other portions of the flame. Thus, nonintrusive optical methods must be used to find the soot primary particle diameters needed to define the soot surface reaction properties mentioned earlier. Unfortunately, approximate nonintrusive methods used during early studies of soot reaction properties in flames, found from laser scattering and absorption measurements analyzed assuming either Rayleigh scattering or Mie scattering from polydisperse effective soot particles having the same mass of soot as individual soot aggregates, have not been found to be an effective way to estimate the soot surface

  11. Linear and nonlinear optical absorption coefficients of spherical dome shells

    NASA Astrophysics Data System (ADS)

    Guo, Kangxian; Liu, Guanghui; Huang, Lu; Zheng, Xianyi

    2015-08-01

    Linear and nonlinear optical absorption coefficients of spherical dome shells are theoretically investigated within analytical wave functions and numerical quantized energy levels. Our results show that the inner radius, the outer radius and the cut-off angle of spherical dome shells have great influences on linear and nonlinear optical absorption coefficients as well as the total optical absorption coefficients. It is found that with the increase of the inner radius and the outer radius, linear and nonlinear optical absorption coefficients exhibit a blueshift and a redshift, respectively. However, with the increase of the cut-off angle, linear and nonlinear optical absorption coefficients do not shift. Besides, the resonant peaks of linear and nonlinear optical absorption coefficients climb up and then decrease with increasing the cut-off angle. The influences of the incident optical intensity on the total optical absorption coefficients are studied. It is found that the bleaching effect occurs at higher incident optical intensity.

  12. Ocean optics estimation for absorption, backscattering, and phase function parameters.

    PubMed

    Hakim, Ammar H; McCormick, Norman J

    2003-02-20

    We propose and test an inverse ocean optics procedure with numerically simulated data for the determination of inherent optical properties using in-water radiance measurements. If data are available at only one depth within a deep homogeneous water layer, then the single-scattering albedo and the single parameter that characterizes the Henyey-Greenstein phase function can be estimated. If data are available at two depths, then these two parameters can be determined along with the optical thickness so that the absorption and scattering coefficients, and also the backscattering coefficient, can be estimated. With a knowledge of these parameters, the albedo and Lambertian fraction of reflected radiance of the bottom can be determined if measurements are made close to the bottom. A simplified method for determining the optical properties of the water also is developed for only three irradiance-type measurements if the radiance is approximately in the asymptotic regime. PMID:12617207

  13. Study on optical weak absorption of borate crystals

    NASA Astrophysics Data System (ADS)

    Li, Xiaomao; Hu, Zhanggui; Yue, Yinchao; Yu, Xuesong; Lin, Zheshuai; Zhang, Guochun

    2013-10-01

    Borate crystal is an important type of nonlinear optical crystals used in frequency conversion in all-solid-state lasers. Especially, LiB3O5 (LBO), CsB3O5 (CBO) and CsLiB6O10 (CLBO) are the most advanced. Although these borate crystals are all constructed by the same anionic group-(B3O7)5-, they show different nonlinear optical properties. In this study, bulk weak absorption values of three borate crystals have been studied at 1064 nm by a photothermal common-path interferometer. The bulk weak absorption values of them along [1 0 0], [0 1 0] and [0 0 1] directions were obtained, respectively, to be approximately 17.5 ppm cm-1, 15 ppm cm-1 and 20 ppm cm-1 (LBO); 80 ppm cm-1, 100 ppm cm-1 and 40 ppm cm-1 (CBO); 600 ppm cm-1, 600 ppm cm-1 and 150 ppm cm-1 (CLBO) at 1064 nm. The results showed an obvious discrepancy of the values of these crystals along three axis directions. A correlation between the bulk weak absorption property and crystal intrinsic structure was then discussed. It is found that the bulk weak absorption values strongly depend on the interstitial area surrounded by the B-O frames. The interstitial area is larger, the bulk weak absorption value is higher.

  14. Grain optical properties

    NASA Technical Reports Server (NTRS)

    Hanner, Martha

    1988-01-01

    The optical properties of small grains provide the link between the infrared observations presented in Chapter 1 and the dust composition described in Chapter 3. In this session, the optical properties were discussed from the viewpoint of modeling the emission from the dust coma and the scattering in order to draw inference about the dust size distribution and composition. The optical properties are applied to the analysis of the infrared data in several ways, and these different uses should be kept in mind when judging the validity of the methods for applying optical constants to real grains.

  15. Optical and thermal properties of doped semiconductor

    NASA Astrophysics Data System (ADS)

    Abroug, S.; Saadallah, F.; Yacoubi, N.

    2008-01-01

    The knowledge of doping effects on optical and thermal properties of semiconductors is crucial for the development of optoelectronic compounds. The purpose of this work is to investigate theses effects by mirage effect technique and spectroscopic ellipsometry SE. The absorption spectra measured for differently doped Si and GaAs bulk samples, show that absorption in the near IR increases with dopant density and also the band gap shifts toward low energies. This behavior is due to free carrier absorption which could be obtained by subtracting phonon assisted absorption from the measured spectrum. This carrier absorption is related to the dopant density throw a semi-empirical model.

  16. Optical absorption spectra of dications of carotenoids

    SciTech Connect

    Jeevarajan, J.A.; Wei, C.C.; Jeevarajan, A.S.; Kispert, L.D.

    1996-04-04

    Quantitative optical absorption spectra of the cation radicals and the dications of canthaxanthin (I), {beta}carotene (II), 7`-cyano-7`-ethoxycarbonyl-7`-apo-{beta}-carotene (III), and 7`,7`-dimethyl-7`-apo-{beta}-carotene (IV) in dichloromethane solution are reported. Exclusive formation of dications occurs when the carotenoids are oxidized with ferric chloride. Addition of neutral carotenoid to the dications results in equilibrium formation of cation radicals. Oxidation with iodine in dichloromethane affords only cation radicals; electrochemical oxidation under suitable conditions yields both dications and cation radicals. Values of the optical parameters depend on the nature of the oxidative medium. The oscillator strengths calculated for gas phase cation radicals and dications of I-IV using the INDO/S method show the same trend as the experimental values. 31 refs., 4 figs., 2 tabs.

  17. Optical absorption of ion-beam sputtered amorphous silicon coatings

    NASA Astrophysics Data System (ADS)

    Steinlechner, Jessica; Martin, Iain W.; Bassiri, Riccardo; Bell, Angus; Fejer, Martin M.; Hough, Jim; Markosyan, Ashot; Route, Roger K.; Rowan, Sheila; Tornasi, Zeno

    2016-03-01

    Low mechanical loss at low temperatures and a high index of refraction should make silicon optimally suited for thermal noise reduction in highly reflective mirror coatings for gravitational wave detectors. However, due to high optical absorption, amorphous silicon (aSi) is unsuitable for being used as a direct high-index coating material to replace tantala. A possible solution is a multimaterial design, which enables exploitation of the excellent mechanical properties of aSi in the lower coating layers. The possible number of aSi layers increases with absorption reduction. In this work, the optimum heat treatment temperature of aSi deposited via ion-beam sputtering was investigated and found to be 450 °C . For this temperature, the absorption after deposition of a single layer of aSi at 1064 nm and 1550 nm was reduced by more than 80%.

  18. Spectral Absorption Properties of Atmospheric Aerosols

    NASA Technical Reports Server (NTRS)

    Bergstrom, R. W.; Pilewskie, P.; Russell, P. B.; Redemann, J.; Bond, T. C.; Quinn, P. K.; Sierau, B.

    2007-01-01

    We have determined the solar spectral absorption optical depth of atmospheric aerosols for specific case studies during several field programs (three cases have been reported previously; two are new results). We combined airborne measurements of the solar net radiant flux density and the aerosol optical depth with a detailed radiative transfer model for all but one of the cases. The field programs (SAFARI 2000, ACE Asia, PRIDE, TARFOX, INTEX-A) contained aerosols representing the major absorbing aerosol types: pollution, biomass burning, desert dust and mixtures. In all cases the spectral absorption optical depth decreases with wavelength and can be approximated with a power-law wavelength dependence (Absorption Angstrom Exponent or AAE). We compare our results with other recent spectral absorption measurements and attempt to briefly summarize the state of knowledge of aerosol absorption spectra in the atmosphere. We discuss the limitations in using the AAE for calculating the solar absorption. We also discuss the resulting spectral single scattering albedo for these cases.

  19. Optical absorption analysis and optimization of gold nanoshells.

    PubMed

    Tuersun, Paerhatijiang; Han, Xiang'e

    2013-02-20

    Gold nanoshells, consisting of a nanoscale dielectric core coated with an ultrathin gold shell, have wide biomedical applications due to their strong optical absorption properties. Gold nanoshells with high absorption efficiencies can help to improve these applications. We investigate the effects of the core material, surrounding medium, core radius, and shell thickness on the absorption spectra of gold nanoshells by using the light-scattering theory of a coated sphere. Our results show that the position and intensity of the absorption peak can be tuned over a wide range by manipulating the above-mentioned parameters. We also obtain the optimal absorption efficiencies and structures of hollow gold nanoshells and gold-coated SiO(2) nanoshells embedded in water at wavelengths of 800, 820, and 1064 nm. The results show that hollow gold nanoshells possess the maximum absorption efficiency (5.42) at a wavelength of 800 nm; the corresponding shell thickness and core radius are 4.8 and 38.9 nm, respectively. They can be used as the ideal photothermal conversation particles for biomedical applications. PMID:23435006

  20. Satellite material contaminant optical properties

    NASA Technical Reports Server (NTRS)

    Wood, B. E.; Bertrand, W. T.; Seiber, B. L.; Kiech, E. L.; Falco, P. M.; Holt, J. D.

    1990-01-01

    The Air Force Wright Research and Development Center and the Arnold Engineering Development Center are continuing a program for measuring optical effects of satellite material outgassing products on cryo-optic surfaces. Presented here are infrared (4000 to 700 cm(-1)) transmittance data for contaminant films condensed on a 77 K geranium window. From the transmittance data, the contaminant film refractive and absorptive indices (n, k) were derived using an analytical thin-film interference model with a nonlinear least-squares algorithm. To date 19 materials have been studied with the optical contents determined for 13 of those. The materials include adhesives, paints, composites, films, and lubricants. This program is continuing and properties for other materials will be available in the future.

  1. Optical Properties of Semiconductor Nanocrystals

    NASA Astrophysics Data System (ADS)

    Gaponenko, S. V.

    1998-10-01

    Low-dimensional semiconductor structures, often referred to as nanocrystals or quantum dots, exhibit fascinating behavior and have a multitude of potential applications, especially in the field of communications. This book examines in detail the optical properties of these structures, gives full coverage of theoretical and experimental results, and discusses their technological applications. The author begins by setting out the basic physics of electron states in crystals (adopting a "cluster-to-crystal" approach), and goes on to discuss the growth of nanocrystals, absorption and emission of light by nanocrystals, optical nonlinearities, interface effects, and photonic crystals. He illustrates the physical principles with references to actual devices such as novel light-emitters and optical switches. The book covers a rapidly developing, interdisciplinary field. It will be of great interest to graduate students of photonics or microelectronics, and to researchers in electrical engineering, physics, chemistry, and materials science.

  2. Optical adhesive property study

    SciTech Connect

    Sundvold, P.D.

    1996-01-01

    Tests were performed to characterize the mechanical and thermal properties of selected optical adhesives to identify the most likely candidate which could survive the operating environment of the Direct Optical Initiation (DOI) program. The DOI system consists of a high power laser and an optical module used to split the beam into a number of channels to initiate the system. The DOI requirements are for a high shock environment which current military optical systems do not operate. Five candidate adhesives were selected and evaluated using standardized test methods to determine the adhesives` physical properties. EC2216, manufactured by 3M, was selected as the baseline candidate adhesive based on the test results of the physical properties.

  3. Thermal properties of carbon black aqueous nanofluids for solar absorption

    NASA Astrophysics Data System (ADS)

    Han, Dongxiao; Meng, Zhaoguo; Wu, Daxiong; Zhang, Canying; Zhu, Haitao

    2011-07-01

    In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.

  4. Modeling optical absorption for thermoreflectance measurements

    NASA Astrophysics Data System (ADS)

    Yang, Jia; Ziade, Elbara; Schmidt, Aaron J.

    2016-03-01

    Optical pump-probe techniques based on thermoreflectance, such as time domain thermoreflectance and frequency domain thermoreflectance (FDTR), have been widely used to characterize the thermal conductivity of thin films and the thermal conductance across interfaces. These techniques typically use a transducer layer to absorb the pump light and improve the thermoreflectance signal. The transducer, however, complicates the interpretation of the measured signal because the approximation that all the energy from the pump beam is deposited at the transducer surface is not always accurate. In this paper, we consider the effect of laser absorption in the top layer of a multilayer sample, and derive an analytical solution for the thermoreflectance signal in the diffusion regime based on volumetric heating. We analyze the measurement sensitivity to the pump absorption depth for transducers with different thermal conductivities, and investigate the additional effect of probe laser penetration depth on the measured signal. We validate our model using FDTR measurements on 490 nm thick amorphous silicon films deposited on fused silica and silicon substrates.

  5. Scattering and Absorption Properties of Biomaterials for Dental Restorative Applications

    NASA Astrophysics Data System (ADS)

    Fernandez-Oliveras, A.; Rubiño, M.; Pérez, M. M.

    2013-08-01

    The physical understanding of the optical properties of dental biomaterials is mandatory for their final success in restorative applications.Light propagation in biological media is characterized by the absorption coefficient, the scattering coefficient, the scattering phase function,the refractive index, and the surface conditions (roughness). We have employed the inverse adding-doubling (IAD) method to combine transmittance and reflectance measurements performed using an integrating-sphere setup with the results of the previous scattering-anisotropygoniometric measurements. This has led to the determination of the absorption and the scattering coefficients. The aim was to optically characterize two different dental-resin composites (nanocomposite and hybrid) and one type of zirconia ceramic, and comparatively study them. The experimental procedure was conducted under repeatability conditions of measurement in order to determine the uncertainty associated to the optical properties of the biomaterials. Spectral variations of the refraction index and the scattering anisotropy factor were also considered. The whole experimental procedure fulfilled all the necessary requirements to provide optical-property values with lower associated uncertainties. The effective transport coefficient presented a similar spectral behavior for the two composites but completely different for the zirconia ceramic. The results demonstrated that the scattering anisotropy exerted a clearly distinct impact on the optical properties of the zirconia ceramic compared with those of the dental-resin composites.

  6. Optical absorption and scattering spectra of pathological stomach tissues

    NASA Astrophysics Data System (ADS)

    Giraev, K. M.; Ashurbekov, N. A.; Lakhina, M. A.

    2011-03-01

    Diffuse reflection spectra of biotissues in vivo and transmission and reflection coefficients for biotissues in vitro are measured over 300-800 nm. These data are used to determine the spectral absorption and scattering indices and the scattering anisotropy factor for stomach mucous membranes under normal and various pathological conditions (chronic atrophic and ulcerous defects, malignant neoplasms). The most importan tphysiological (hemodynamic and oxygenation levels) and structural-morphological (scatterer size and density) parameters are also determined. The results of a morphofunctional study correlate well with the optical properties and are consistent with data from a histomorphological analysis of the corresponding tissues.

  7. Continuous wavelet-transform analysis of photoacoustic signal waveform to determine optical absorption coefficient

    NASA Astrophysics Data System (ADS)

    Hirasawa, T.; Ishihara, M.; Tsujita, K.; Hirota, K.; Irisawa, K.; Kitagaki, M.; Fujita, M.; Kikuchi, M.

    2012-02-01

    In photo-acoustic (PA) imaging, valuable medical applications based on optical absorption spectrum such as contrast agent imaging and blood oxygen saturation measurement have been investigated. In these applications, there is an essential requirement to determine optical absorption coefficients accurately. In present, PA signal intensities have been commonly used to determine optical absorption coefficients. This method achieves practical accuracy by combining with radiative transfer analysis. However, time consumption of radiative transfer analysis and effects of signal generation efficiencies were problems of this method. In this research, we propose a new method to determine optical absorption coefficients using continuous wavelet transform (CWT). We used CWT to estimate instantaneous frequencies of PA signals which reflects optical absorption distribution. We validated the effectiveness of CWT in determination of optical absorption coefficients through an experiment. In the experiment, planar shaped samples were illuminated to generate PA signal. The PA signal was measured by our fabricated PA probe in which an optical fiber and a ring shaped P(VDFTrFE) ultrasound sensor were coaxially aligned. Optical properties of samples were adjusted by changing the concentration of dye solution. Tunable Ti:Sapphire laser (690 - 1000 nm) was used as illumination source. As a result, we confirmed strong correlation between optical absorption coefficients of samples and the instantaneous frequency of PA signal obtained by CWT. Advantages of this method were less interference of light transfer and signal generation efficiency.

  8. Optical absorption of nanoporous silicon: quasiparticle band gaps and absorption spectra

    NASA Astrophysics Data System (ADS)

    Shi, Guangsha; Kioupakis, Emmanouil

    2013-03-01

    Silicon is an earth-abundant material of great importance in semiconductors electronics, but its photovoltaic applications are limited by the low absorption coefficient in the visible due to its indirect band gap. One strategy to improve the absorbance is to perforate silicon with nanoscale pores, which introduce carrier scattering that enables optical transitions across the indirect gap. We used density functional and many-body perturbation theory in the GW approximation to investigate the electronic and optical properties of porous silicon for various pore sizes, spacings, and orientations. Our calculations include up to 400 atoms in the unit cell. We will discuss the connection of the band-gap value and absorption coefficient to the underlying nanopore geometry. The absorption coefficient in the visible range is found to be optimal for appropriately chosen nanopore size, spacing, and orientation. Our work allows us to predict porous-silicon structures that may have optimal performance in photovoltaic applications. This research was supported as part of CSTEC, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Computational resources were provided by the DOE NERSC facility.

  9. Optical absorption in semiconductor nanorings under electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Zhang, Tong-Yi; Cao, Jun-Cheng; Zhao, Wei

    2005-01-01

    The optical absorption in semiconductor nanorings under a lateral DC field and a perpendicular magnetic field is numerically simulated by coherent wave approach. The exciton dominated optical absorption is compared with the free-carrier interband absorption to demonstrate the key role of Coulomb interaction between electron and hole. The influence of the lateral DC field and the perpendicular magnetic field on the optical absorption are discussed in detail. It shows that the lateral DC field can significantly enhance the Aharonov-Bohm effect of the neutral excitons in semiconductor nanorings.

  10. Cirrus cloud optical and microphysical property retrievals from eMAS during SEAC4RS using bi-spectral reflectance measurements within the 1.88 µm water vapor absorption band

    NASA Astrophysics Data System (ADS)

    Meyer, Kerry; Platnick, Steven; Arnold, G. Thomas; Holz, Robert E.; Veglio, Paolo; Yorks, John; Wang, Chenxi

    2016-04-01

    Previous bi-spectral imager retrievals of cloud optical thickness (COT) and effective particle radius (CER) based on the Nakajima and King (1990) approach, such as those of the operational MODIS cloud optical property retrieval product (MOD06), have typically paired a non-absorbing visible or near-infrared wavelength, sensitive to COT, with an absorbing shortwave or mid-wave infrared wavelength sensitive to CER. However, in practice it is only necessary to select two spectral channels that exhibit a strong contrast in cloud particle absorption. Here it is shown, using eMAS observations obtained during NASA's SEAC4RS field campaign, that selecting two absorbing wavelength channels within the broader 1.88 µm water vapor absorption band, namely the 1.83 and 1.93 µm channels that have sufficient differences in ice crystal single scattering albedo, can yield COT and CER retrievals for thin to moderately thick single-layer cirrus that are reasonably consistent with other solar and IR imager-based and lidar-based retrievals. A distinct advantage of this channel selection for cirrus cloud retrievals is that the below-cloud water vapor absorption minimizes the surface contribution to measured cloudy top-of-atmosphere reflectance, in particular compared to the solar window channels used in heritage retrievals such as MOD06. This reduces retrieval uncertainty resulting from errors in the surface reflectance assumption and reduces the frequency of retrieval failures for thin cirrus clouds.

  11. The Optical Properties of Ion Implanted Silica

    NASA Technical Reports Server (NTRS)

    Smith, Cydale C.; Ila, D.; Sarkisov, S.; Williams, E. K.; Poker, D. B.; Hensley, D. K.

    1997-01-01

    We will present our investigation on the change in the optical properties of silica, 'suprasil', after keV through MeV implantation of copper, tin, silver and gold and after annealing. Suprasil-1, name brand of silica glass produced by Hereaus Amerisil, which is chemically pure with well known optical properties. Both linear nonlinear optical properties of the implanted silica were investigated before and after thermal annealing. All implants, except for Sn, showed strong optical absorption bands in agreement with Mie's theory. We have also used Z-scan to measure the strength of the third order nonlinear optical properties of the produced thin films, which is composed of the host material and the metallic nanoclusters. For implants with a measurable optical absorption band we used Doyle's theory and the full width half maximum of the absorption band to calculate the predicted size of the formed nanoclusters at various heat treatment temperatures. These results are compared with those obtained from direct observation using transmission electron microscopic techniques.

  12. Absorption Filter Based Optical Diagnostics in High Speed Flows

    NASA Technical Reports Server (NTRS)

    Samimy, Mo; Elliott, Gregory; Arnette, Stephen

    1996-01-01

    Two major regimes where laser light scattered by molecules or particles in a flow contains significant information about the flow are Mie scattering and Rayleigh scattering. Mie scattering is used to obtain only velocity information, while Rayleigh scattering can be used to measure both the velocity and the thermodynamic properties of the flow. Now, recently introduced (1990, 1991) absorption filter based diagnostic techniques have started a new era in flow visualization, simultaneous velocity and thermodynamic measurements, and planar velocity measurements. Using a filtered planar velocimetry (FPV) technique, we have modified the optically thick iodine filter profile of Miles, et al., and used it in the pressure-broaden regime which accommodates measurements in a wide range of velocity applications. Measuring velocity and thermodynamic properties simultaneously, using absorption filtered based Rayleigh scattering, involves not only the measurement of the Doppler shift, but also the spectral profile of the Rayleigh scattering signal. Using multiple observation angles, simultaneous measurement of one component velocity and thermodynamic properties in a supersonic jet were measured. Presently, the technique is being extended for simultaneous measurements of all three components of velocity and thermodynamic properties.

  13. Correction of optical absorption and scattering variations in laser speckle rheology measurements

    PubMed Central

    Hajjarian, Zeinab; Nadkarni, Seemantini K.

    2014-01-01

    Laser Speckle Rheology (LSR) is an optical technique to evaluate the viscoelastic properties by analyzing the temporal fluctuations of backscattered speckle patterns. Variations of optical absorption and reduced scattering coefficients further modulate speckle fluctuations, posing a critical challenge for quantitative evaluation of viscoelasticity. We compare and contrast two different approaches applicable for correcting and isolating the collective influence of absorption and scattering, to accurately measure mechanical properties. Our results indicate that the numerical approach of Monte-Carlo ray tracing (MCRT) reliably compensates for any arbitrary optical variations. When scattering dominates absorption, yet absorption is non-negligible, diffusing wave spectroscopy (DWS) formalisms perform similar to MCRT, superseding other analytical compensation approaches such as Telegrapher equation. The computational convenience of DWS greatly simplifies the extraction of viscoelastic properties from LSR measurements in a number of chemical, industrial, and biomedical applications. PMID:24663983

  14. Correction of optical absorption and scattering variations in Laser Speckle Rheology measurements.

    PubMed

    Hajjarian, Zeinab; Nadkarni, Seemantini K

    2014-03-24

    Laser Speckle Rheology (LSR) is an optical technique to evaluate the viscoelastic properties by analyzing the temporal fluctuations of backscattered speckle patterns. Variations of optical absorption and reduced scattering coefficients further modulate speckle fluctuations, posing a critical challenge for quantitative evaluation of viscoelasticity. We compare and contrast two different approaches applicable for correcting and isolating the collective influence of absorption and scattering, to accurately measure mechanical properties. Our results indicate that the numerical approach of Monte-Carlo ray tracing (MCRT) reliably compensates for any arbitrary optical variations. When scattering dominates absorption, yet absorption is non-negligible, diffusing wave spectroscopy (DWS) formalisms perform similar to MCRT, superseding other analytical compensation approaches such as Telegrapher equation. The computational convenience of DWS greatly simplifies the extraction of viscoelastic properties from LSR measurements in a number of chemical, industrial, and biomedical applications. PMID:24663983

  15. Optical properties of stabilized copper nanoparticles

    NASA Astrophysics Data System (ADS)

    Mohindroo, Jeevan Jyoti; Garg, Umesh Kumar; Sharma, Anshul Kumar

    2016-05-01

    Optical studies involving calculation of Band Gap of the synthesized copper nanoparticles were carried out in the wavelength range of 500 to 650 nm at room temperature, the particles showed high absorption at 550nm indicating their good absorptive properties. In this method water is used as the medium for reduction of copper ions in to copper Nanoparticles the stabilization of copper Nanoparticles was studied with starch both as a reductant and stabilizer,. The reaction mixture was heated using a kitchen microwave for about 5 minutes to attain the required temp for the reaction. The pH of the solution was adjusted to alkaline using 5%solution of NaOH. Formation of Copper Nanoparticles was indicated by change in color of the solution from blue to yellowish black which is supported by the UV absorption at 570nm.the synthesized particles were washed with water and alcohol. The optical properties depend upon absorption of radiations which in turn depends upon ratio of electrons and holes present in the material and also on the shape of the nanoparticles. In the present investigation it was observed that optical absorption increases with increase in particle size. The optical band gap for the Nanoparticles was obtained from plots between hv vs. (αhv)2 and hv vs. (αhv)1/2. The value of Band gap came out to be around 1.98-2.02 eV which is in close agreement with the earlier reported values

  16. Terahertz optical properties of the cornea

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Quan; Lu, Yuan-Fu; Jiao, Guo-Hua; Chen, Xian-Feng; Li, Jin-Ying; Chen, Si-Hai; Dong, Yu-Ming; Lv, Jian-Cheng

    2016-01-01

    We present a study aimed at developing a terahertz time domain spectroscopy (THz-TDS) system for detection of the optical properties of ex vivo rabbit corneal tissues with different water content at terahertz frequencies (0.1-0.3 THz). The refractive index decreased with frequency while the absorption coefficient increased with frequency. Our experimental results matched the theoretical calculation very well revealing that both the absorption coefficient and the refractive index of a hydrated cornea were much larger than that of a dehydrated cornea and the terahertz properties depended on the hydrate conditions of the biosamples.

  17. Control of enhanced optical absorption in {mu}c-Si

    SciTech Connect

    Kalkan, A.K.; Fonash, S.J.

    1997-07-01

    The influence of grain size on the enhanced optical absorption of {micro}c-Si has been investigated using films of various grain sizes prepared by solid phase crystallization. The authors show that they can control this grain size and therefore the degree of absorption changes. For grain sizes below a threshold range significant absorption enhancement can be seen in the photon energy range of 1 to {approximately}3 eV and the absorption characteristics of these films show that the dominant mode of optical transitions is indirect. A correlation between first order Raman peak broadening and enhanced absorption was found suggesting both effects are related to confinement. A simple model was developed to see how confinement in the crystallites could influence indirect optical transitions.

  18. Spatial variability of absorption properties in Lake Balaton, Hungary

    NASA Astrophysics Data System (ADS)

    Riddick, C. A.; Hunter, P. D.; Tyler, A. N.; Vicente, V. M.; Groom, S.; Horváth, H.; Kovacs, A.; Preston, T.; Presing, M.

    2013-12-01

    In order to improve robustness of current remote sensing algorithms for lake monitoring, it is vital to understand the variability of inherent optical properties (IOPs) within a lake. In this study, absorption coefficients were measured in situ at 38 stations in Lake Balaton, Hungary, using a WET Labs AC-S and AC-9 and compared to concurrent absorption measurements by dual beam spectrophotometry in the laboratory. The spatial variability of bulk and chlorophyll-specific absorption coefficients was examined across 5 basins, demonstrating a gradient in total absorption corresponding to the trophic gradient. Our data suggests that sampling conditions had an impact on particulate absorption, affecting the proportion attributed to non-algal particles (aNAP), phytoplankton (aph) or color dissolved organic matter (aCDOM). The specific absorption of phytoplankton (a*ph) spectra showed a distinct peak in the UV portion of the spectra in Basins 3 and 4 (east), which may be due to the presence of phytoplankton photoprotective pigments to compensate for lower CDOM levels in these basins. In contrast to oceans, particulate attenuation (cp) had a weaker relationship to chlorophyll-a (R2=0.15) than to total suspended matter (R2=0.84), particularly the inorganic fraction. Additionally, the relative contribution of particulate scattering (bp) to attenuation was significantly higher in Lake Balaton (up to 85-99%) than that found in previous lacustrine studies. bp also demonstrated a gradient across the lake, where values increased as the water progressed from phytoplankton-dominated to mineral-dominated. These results provide knowledge of the heterogeneity of the IOPs within Lake Balaton, which is to be considered for the future improvement of bio-optical algorithms for constituent retrieval in inland waters.

  19. Optical Absorption Microspectroscopy (μ-OAS) Based on Schwarzschild-Type Cassegrain Optics.

    PubMed

    Chassé, Mathieu; Lelong, Gérald; van Nijnatten, Peter; Schoofs, Ivo; de Wolf, Jürgen; Galoisy, Laurence; Calas, Georges

    2015-04-01

    A new experimental setup, combining a custom-designed Schwarzschild-type Cassegrain-based microscope and an ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometer, has been developed, focusing the light beam down to 20 μm diameter. Optical absorption spectra (in the 300-2500 nm range) have been measured on micrometer-sized natural glass inclusions providing information on iron speciation in magmatic melts. The absence of contribution from the host crystal matrix provides a test of the efficiency of micro-focusing. A microthermometric stage has been adapted on the microscope for measuring optical absorption spectra up to 900 K with application to the thermochromism of minute natural spinel crystals (MgAl2O4:Fe(2+),Cr(3+)). This experimental setup provides an easy and fast way to follow the evolution of spectral properties and color of glasses or crystals with temperature as well as the possibility of measuring spatially resolved optical absorption spectra. PMID:25741926

  20. Optical properties of thin graphitic nanopetal arrays

    NASA Astrophysics Data System (ADS)

    Bao, Hua; Kumar, Anurag; Cai, Yuannan; Ji, Yuzhong; Fisher, Timothy S.; Ruan, Xiulin

    2015-06-01

    Thermal radiative properties of thin graphitic petal arrays are theoretically and experimentally investigated. Finite-difference time-domain (FDTD) simulations are first performed to calculate optical properties of vertical graphitic arrays of different structures, namely, graphitic gratings, periodic graphitic cavities, and random graphitic cavities. For graphitic gratings, the absorptance and reflectance are relatively larger when the incident electric field is parallel to the graphitic plane, while the absorptance and reflectance are both significantly lower when the electric field is polarized perpendicular to the graphitic plane. Ordered graphitic petal cavity arrays show optical properties falling between the above two cases of different polarizations. Random vertical cavity arrays with various angles of orientation show similar properties to ordered petal cavities. For oblique gratings, the reflectance will increase with oblique angle for both polarizations, while the absorptance decreases with oblique angle for the in-plane polarization and increases with oblique angle for the out-of-plane polarization. The oblique effects are explained by the strong anisotropic nature of graphitic petals. The FDTD results are compared to effective medium theory to find that the latter describes the optical properties of the graphitic grating and cavity well, and we propose an approach based on effective medium theory to approximate the dielectric function of graphitic petals with random orientation. The predicted hemispherical total reflectance based on this model gives about 2% reflectance in the visible spectrum and agrees well with experimental data from a fabricated graphitic petals sample.

  1. Exploring the origin of high optical absorption in conjugated polymers.

    PubMed

    Vezie, Michelle S; Few, Sheridan; Meager, Iain; Pieridou, Galatia; Dörling, Bernhard; Ashraf, Raja Shahid; Goñi, Alejandro R; Bronstein, Hugo; McCulloch, Iain; Hayes, Sophia C; Campoy-Quiles, Mariano; Nelson, Jenny

    2016-07-01

    The specific optical absorption of an organic semiconductor is critical to the performance of organic optoelectronic devices. For example, higher light-harvesting efficiency can lead to higher photocurrent in solar cells that are limited by sub-optimal electrical transport. Here, we compare over 40 conjugated polymers, and find that many different chemical structures share an apparent maximum in their extinction coefficients. However, a diketopyrrolopyrrole-thienothiophene copolymer shows remarkably high optical absorption at relatively low photon energies. By investigating its backbone structure and conformation with measurements and quantum chemical calculations, we find that the high optical absorption can be explained by the high persistence length of the polymer. Accordingly, we demonstrate high absorption in other polymers with high theoretical persistence length. Visible light harvesting may be enhanced in other conjugated polymers through judicious design of the structure. PMID:27183327

  2. X-shaped Electro-Optic Chromophore with Remarkably Blue-Shifted Optical Absorption. Synthesis, Characterization, Linear/Nonlinear Optical Properties, Self-Assembly, and Thin Film Microstructural Characteristics

    SciTech Connect

    Kang,H.; Evmenenko, G.; Dutta, P.; Clays, K.; Song, K.; Marks, T.

    2006-01-01

    A novel type of 'X-shaped' two-dimensional electro-optic (EO) chromophore with extended conjugation has been synthesized and characterized. This chromophore is found to exhibit a remarkably blue-shifted optical maximum (357 nm in CH{sub 2}Cl{sub 2}) while maintaining a very large first hyperpolarizability ({beta}). Hyper-Rayleigh Scattering (HRS) measurements at 800 nm provide a {beta}{sub zzz} value of 1840 x 10{sup -30} esu. Self-assembled thin films of this chromophore were fabricated via a layer-by-layer chemisorptive siloxane-based approach. The chromophoric multilayers have been characterized by transmission optical spectroscopy, advancing contact angle measurements, synchrotron X-ray reflectivity, atomic force microscopy, and angle-dependent polarized second harmonic generation spectroscopy. The self-assembled chromophoric films exhibit a dramatically blue-shifted optical maximum (325 nm) while maintaining a large EO response ({chi}({sup 2}){sub 333} {approx} 232 pm/V at 1064 nm; r{sub 33} {approx} 45 pm/V at 1310 nm). This work demonstrates an attractive approach to developing EO materials offering improved nonlinearity-transparency trade-offs.

  3. X-Shaped electro-optic chromophore with remarkably blue-shifted optical absorption. Synthesis, characterization, linear/nonlinear optical properties, self-assembly, and thin film microstructural characteristics.

    PubMed

    Kang, Hu; Evmenenko, Guennadi; Dutta, Pulak; Clays, Koen; Song, Kai; Marks, Tobin J

    2006-05-10

    A novel type of "X-shaped" two-dimensional electro-optic (EO) chromophore with extended conjugation has been synthesized and characterized. This chromophore is found to exhibit a remarkably blue-shifted optical maximum (357 nm in CH(2)Cl(2)) while maintaining a very large first hyperpolarizability (beta). Hyper-Rayleigh Scattering (HRS) measurements at 800 nm provide a beta(zzz) value of 1840 x 10(-30) esu. Self-assembled thin films of this chromophore were fabricated via a layer-by-layer chemisorptive siloxane-based approach. The chromophoric multilayers have been characterized by transmission optical spectroscopy, advancing contact angle measurements, synchrotron X-ray reflectivity, atomic force microscopy, and angle-dependent polarized second harmonic generation spectroscopy. The self-assembled chromophoric films exhibit a dramatically blue-shifted optical maximum (325 nm) while maintaining a large EO response (chi(2)(333) approximately 232 pm/V at 1064 nm; r(33) approximately 45 pm/V at 1310 nm). This work demonstrates an attractive approach to developing EO materials offering improved nonlinearity-transparency trade-offs. PMID:16669690

  4. Optical properties of flyash

    SciTech Connect

    Self, S.A.

    1991-11-01

    This is the sixteenth quarterly report under DOE contract No. DE-AC22-87PC 79903 entitled Optical Properties of Flyash.'' Tasks 1 and 2 of this program were funded from September 15, 1987. Tasks 3 and 4 were funded from September 15, 1988. The general aims of this research are to provide a fundamental scientific basis for the physical understanding and reliable calculation of radiative heat transfer in coal combustion systems, particularly as it is influenced by the presence of inorganic constituents deriving from the mineral matter in coal. Some preliminary work in this area has been carried out at Stanford in the past several years with NSF support. The present program will greatly enlarge the scope of this work.

  5. Strain- and twist-engineered optical absorption of few-layer black phosphorus

    NASA Astrophysics Data System (ADS)

    Jia, Qian; Kong, XiangHua; Qiao, JingSi; Ji, Wei

    2016-09-01

    Density functional and many-body perturbation theories calculations were carried out to investigate fundamental and optical bandgap, exciton binding energy and optical absorption property of normal and strain- and twist-engineered few-layer black phosphorus (BP). We found that the fundamental bandgaps of few layer BP can be engineered by layer stacking and in-plane strain, with linear relationships to their associated exciton binding energies. The strain-dependent optical absorption behaviors are also anisotropic that the position of the first absorption peak monotonically blue-shifts as the strain applies to either direction for incident light polarized along the armchair direction, but this is not the case for that along the zigzag direction. Given those striking properties, we proposed two prototype devices for building potentially more balanced light absorbers and light filter passes, which promotes further applications and investigations of BP in nanoelectronics and optoelectronics.

  6. [Study of retrieving formaldehyde with differential optical absorption spectroscopy].

    PubMed

    Li, Yu-Jin; Xie, Pin-Hua; Qin, Min; Qu, Xiao-Ying; Hu, Lin

    2009-01-01

    The present paper introduces the method of retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS). The authors measured ambient HCHO in Beijing region with the help of differential optical absorption spectroscopy instrument made by ourself, and discussed numerous factors in retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS), especially, the choice of HCHO wave band, how to avoid absorption of ambient SO2, NO2 and O3, and the influence of the Xenon lamp spectrum structure on the absorption of ambient HCHO. The authors achieved the HCHO concentration by simultaneously retrieving the concentrations of HCHO, SO2, NO2 and O3 with non-linear least square fitting method, avoiding the effect of choosing narrow wave of HCHO and the residual of SO2, NO2, O3 and the Xenon lamp spectrum structure in retrieving process to attain the concentration of HCHO, Finally the authors analyzed the origin of error in retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS), and the total error is within 13.7% in this method. PMID:19385238

  7. Phosphate-free synthesis, optical absorption and photoelectric properties of Cu2ZnGeS4 and Cu2ZnGeSe4 uniform nanocrystals.

    PubMed

    Shi, Liang; Yin, Peiqun

    2013-10-01

    Copper-based quaternary chalcogenide semiconductor Cu2ZnGeS4 and Cu2ZnGeSe4 nanocrystals have been synthesized successfully via a simple and convenient one-pot phosphine-free solution approach. Oleylamine was used as both the solvent and reductant for Se or S and benefited the formation of homogeneous quaternary nanocrystals. Scanning transmission electron microscopy-EDS elemental mapping confirms the uniform spatial distribution of four elements in nanocrystals. UV-Vis absorption spectra of Cu2ZnGeS4 and Cu2ZnGeSe4 nanocrystals show strong photon absorption in the entire visible range. The photoresponsive behavior indicates the potential application of Cu2ZnGeSe4 nanocrystals in solar energy conversion systems. PMID:23900582

  8. Optical properties of cells with melanin

    NASA Astrophysics Data System (ADS)

    Rohde, Barukh; Coats, Israel; Krueger, James; Gareau, Dan

    2014-02-01

    The optical properties of pigmented lesions have been studied using diffuse reflectance spectroscopy in a noninvasive configuration on optically thick samples such as skin in vivo. However, it is difficult to un-mix the effects of absorption and scattering with diffuse reflectance spectroscopy techniques due to the complex anatomical distributions of absorbing and scattering biomolecules. We present a device and technique that enables absorption and scattering measurements of tissue volumes much smaller than the optical mean-free path. Because these measurements are taken on fresh-frozen sections, they are direct measurements of the optical properties of tissue, albeit in a different hydration state than in vivo tissue. Our results on lesions from 20 patients including melanomas and nevi show the absorption spectrum of melanin in melanocytes and basal keratinocytes. Our samples consisted of fresh frozen sections that were unstained. Fitting the spectrum as an exponential decay between 500 and 1100 nm [mua = A*exp(-B*(lambda-C)) + D], we report on the fit parameters of and their variation due to biological heterogeneity as A = 4.20e4 +/- 1.57e5 [1/cm], B = 4.57e-3 +/- 1.62e-3 [1/nm], C = 210 +/- 510 [nm] , D = 613 +/- 534 [1/cm]. The variability in these results is likely due to highly heterogeneous distributions of eumelanin and pheomelanin.

  9. Distributed Bragg Reflectors With Reduced Optical Absorption

    DOEpatents

    Klem, John F.

    2005-08-16

    A new class of distributed Bragg reflectors has been developed. These distributed Bragg reflectors comprise interlayers positioned between sets of high-index and low-index quarter-wave plates. The presence of these interlayers is to reduce photon absorption resulting from spatially indirect photon-assisted electronic transitions between the high-index and low-index quarter wave plates. The distributed Bragg reflectors have applications for use in vertical-cavity surface-emitting lasers for use at 1.55 .mu.m and at other wavelengths of interest.

  10. Electronic structure and optic absorption of phosphorene under strain

    NASA Astrophysics Data System (ADS)

    Duan, Houjian; Yang, Mou; Wang, Ruiqiang

    2016-07-01

    We studied the electronic structure and optic absorption of phosphorene (monolayer of black phosphorus) under strain. Strain was found to be a powerful tool for the band structure engineering. The in-plane strain in armchair or zigzag direction changes the effective mass components along both directions, while the vertical strain only has significant effect on the effective mass in the armchair direction. The band gap is narrowed by compressive in-plane strain and tensile vertical strain. Under certain strain configurations, the gap is closed and the energy band evolves to the semi-Dirac type: the dispersion is linear in the armchair direction and is gapless quadratic in the zigzag direction. The band-edge optic absorption is completely polarized along the armchair direction, and the polarization rate is reduced when the photon energy increases. Strain not only changes the absorption edge (the smallest photon energy for electron transition), but also the absorption polarization.

  11. Optical absorption spectra of palladium doped gold cluster cations

    SciTech Connect

    Kaydashev, Vladimir E.; Janssens, Ewald Lievens, Peter

    2015-01-21

    Photoabsorption spectra of gas phase Au{sub n}{sup +} and Au{sub n−1}Pd{sup +} (13 ≤ n ≤ 20) clusters were measured using mass spectrometric recording of wavelength dependent Xe messenger atom photodetachment in the 1.9–3.4 eV photon energy range. Pure cationic gold clusters consisting of 15, 17, and 20 atoms have a higher integrated optical absorption cross section than the neighboring sizes. It is shown that the total optical absorption cross section increases with size and that palladium doping strongly reduces this cross section for all investigated sizes and in particular for n = 14–17 and 20. The largest reduction of optical absorption upon Pd doping is observed for n = 15.

  12. [Spectral calibration for space-borne differential optical absorption spectrometer].

    PubMed

    Zhou, Hai-Jin; Liu, Wen-Qing; Si, Fu-Qi; Zhao, Min-Jie; Jiang, Yu; Xue, Hui

    2012-11-01

    Space-borne differential optical absorption spectrometer is used for remote sensing of atmospheric trace gas global distribution. This instrument acquires high accuracy UV/Vis radiation scattered or reflected by air or earth surface, and can monitor distribution and variation of trace gases based on differential optical absorption spectrum algorithm. Spectral calibration is the premise and base of quantification of remote sensing data of the instrument, and the precision of calibration directly decides the level of development and application of the instrument. Considering the characteristic of large field, wide wavelength range, high spatial and spectral resolution of the space-borne differential optical absorption spectrometer, a spectral calibration method is presented, a calibration device was built, the equation of spectral calibration was calculated through peak searching and regression analysis, and finally the full field spectral calibration of the instrument was realized. The precision of spectral calibration was verified with Fraunhofer lines of solar light. PMID:23387142

  13. Nonlinear intersubband optical absorption in a semiconductor quantum well

    NASA Technical Reports Server (NTRS)

    Ahn, D.; Chuang, S. L.

    1987-01-01

    The third-order nonlinear intersubband absorption in a semiconductor quantum well is studied theoretically using the density matrix formalism including intrasubband relaxation. It is shown that the peak absorption is reduced by half for an optical intensity 1 MW/sq cm for the well size L = 126.5 A with 3.0 x 10 to the 16th/cu cm electrons.

  14. Optical absorption enhancement of CdTe nanostructures by low-energy nitrogen ion bombardment

    NASA Astrophysics Data System (ADS)

    Akbarnejad, E.; Ghoranneviss, M.; Mohajerzadeh, S.; Hantehzadeh, M. R.; Asl Soleimani, E.

    2016-02-01

    In this paper we present the fabrication of cadmium telluride (CdTe) nanostructures by means of RF magnetron sputtering followed by low-energy ion implantation and post-thermal treatment. We have thoroughly studied the structural, optical, and morphological properties of these nanostructures. The effects of nitrogen ion bombardment on the structural parameters of CdTe nanostructures such as crystal size, microstrain, and dislocation density have been examined. From x-ray diffractometer (XRD) analysis it could be deduced that N+ ion fluence and annealing treatment helps to form (3 0 0) orientation in the crystalline structure of cadmium-telluride films. Fluctuations in optical properties like the optical band gap and absorption coefficient as a function of N+ ion fluences have been observed. The annealing of the sample irradiated by a dose of 1018 ions cm-2 has led to great enhancement in the optical absorption over a wide range of wavelengths with a thickness of 250 nm. The enhanced absorption is significantly higher than the observed value in the original CdTe layer with a thickness of 3 μm. Surface properties such as structure, grain size and roughness are noticeably affected by varying the nitrogen fluences. It is speculated that nitrogen bombardment and post-annealing treatment results in a smaller optical band gap, which in turn leads to higher absorption. Nitrogen bombardment is found to be a promising method to increase efficiency of thin film solar cells.

  15. Optical Absorption Spectra of Sodium Borate Cobalt Doped Glasses

    SciTech Connect

    Elokr, M. M.; Hassan, M. A.; Yaseen, A. M.; Elokr, R.

    2007-02-14

    Glassy system: xNa2O-(100-x-y)B2O3-yCo3O4 has been prepared by conventional melt quenching technique. Optical absorption spectra have been obtained in the range 300 - 2500 nm at room temperature. An absorption edge was observed in the near UV range, the analysis of which reveals that indirect transition is the dominant absorption mechanism. All prepared samples exhibit blue color, indicating that the Co ions are acted upon by tetrahedral ligand field. Obtained spectra were used to estimate some ligand field parameters.

  16. Metal nanoparticles enhanced optical absorption in thin film solar cells

    NASA Astrophysics Data System (ADS)

    Xie, Wanlu; Liu, Fang; Qu, Di; Xu, Qi; Huang, Yidong

    2011-12-01

    The plasmonic enhanced absorption for thin film solar cells with silver nanoparticles (NPs) deposited on top of the amorphous silicon film (a-Si:H) solar cells and embedded inside the active layer of organic solar cells (OSCs) has been simulated and analyzed. Obvious optical absorption enhancement is obtained not only at vertical incidence but also at oblique incidence. By properly adjusting the period and size of NPs, an increased absorption enhancement of about 120% and 140% is obtained for a-Si:H solar cells and OSCs, respectively.

  17. Optical absorption of several nanostructures arrays for silicon solar cells

    NASA Astrophysics Data System (ADS)

    Xu, Zhaopeng; Qiao, Huiling; Huangfu, Huichao; Li, Xiaowei; Guo, Jingwei; Wang, Haiyan

    2015-12-01

    To improve the efficiency and reduce the cost of solar cells, it's important to enhance the light absorption. Within the visible solar spectrum based on optimization simulations by COMSOL Multiphysics, the optical absorption of silicon cylindrical nanowires, nanocones and inverted nanocones was calculated respectively. The results reveal that the average absorption for the nanocones between 400 and 800 nm is 70.2%, which is better than cylindrical nanowires (55.3%), inverted nanocones (42.3%) and bulk silicon (42.2%). In addition, more than 95% of light from 630 to 800 nm is reflected for inverted nanocones, which can be used to enhance infrared reflection in photovoltaic devices.

  18. Differential optical absorption spectrometer for measurement of tropospheric pollutants

    NASA Astrophysics Data System (ADS)

    Evangelisti, F.; Baroncelli, A.; Bonasoni, P.; Giovanelli, G.; Ravegnani, F.

    1995-05-01

    Our institute has recently developed a differential optical absorption spectrometry system called the gas analyzer spectrometer correlating optical absorption differences (GASCOAD), which features as a detector a linear image sensor that uses an artificial light source for long-path tropospheric-pollution monitoring. The GASCOAD, its method of eliminating interference from background sky light, and subsequent spectral analysis are reported and discussed. The spectrometer was used from 7 to 22 February 1993 in Milan, a heavily polluted metropolitan area, to measure the concentrations of SO2, NO2, O3, and HNO2 averaged over a 1.7-km horizontal light path. The findings are reported and briefly discussed.

  19. Nonlinear absorption and transmission properties of Ge, Te and InAs using tuneable IR FEL

    SciTech Connect

    Amirmadhi, F.; Becker, K.; Brau, C.A.

    1995-12-31

    Nonlinear absorption properties of Ge, Te and InAs are being investigated using the transmission of FEL optical pulses through these semiconductors (z-scan method). Wavelength, intensity and macropulse dependence are used to differentiate between two-photon and free-carrier absorption properties of these materials. Macropulse dependence is resolved by using a Pockles Cell to chop the 4-{mu}s macropulse down to 100 ns. Results of these experiments will be presented and discussed.

  20. Absorption measurement of thin films by using photothermal techniques: The influence of thermal properties

    SciTech Connect

    Wu, Z.L.; Kuo, P.K.; Thomas, R.L.; Fan, Z.X.

    1995-12-31

    Photothermal techniques are widely used for measuring optical absorption of thin film coatings. In these applications the calibration of photothermal signal is typically based on the assumption that the thermal properties of the thin film make very little contribution. In this paper we take mirage technique as an example and present a detailed analysis of the influence of thin film thermal properties on absorption measurements. The results show that the traditional calibration method is not valid on surprisingly many situations.

  1. Deriving in situ phytoplankton absorption for bio-optical productivity models in turbid waters

    NASA Astrophysics Data System (ADS)

    Oliver, Matthew J.; Schofield, Oscar; Bergmann, Trisha; Glenn, Scott; Orrico, Cristina; Moline, Mark

    2004-07-01

    As part of Hyperspectral Coupled Ocean Dynamics Experiment, a high-resolution hydrographic and bio-optical data set was collected from two cabled profilers at the Long-Term Ecosystem Observatory (LEO). Upwelling- and downwelling-favorable winds and a buoyant plume from the Hudson River induced large changes in hydrographic and optical structure of the water column. An absorption inversion model estimated the relative abundance of phytoplankton, colored dissolved organic matter (CDOM) and detritus, as well as the spectral exponential slopes of CDOM and detritus from in situ WET Labs nine-wavelength absorption/attenuation meter (ac-9) absorption data. Derived optical weights were proportional to the parameter concentrations and allowed for their absorptions to be calculated. Spectrally weighted phytoplankton absorption was estimated using modeled spectral irradiances and the phytoplankton absorption spectra inverted from an ac-9. Derived mean spectral absorption of phytoplankton was used in a bio-optical model estimating photosynthetic rates. Measured radiocarbon uptake productivity rates extrapolated with water mass analysis and the bio-optical modeled results agreed within 20%. This approach is impacted by variability in the maximum quantum yield (ϕmax) and the irradiance light-saturation parameter (Ek(PAR)). An analysis of available data shows that ϕmax variability is relatively constrained in temperate waters. The variability of Ek(PAR) is greater in temperate waters, but based on a sensitivity analysis, has an overall smaller impact on water-column-integrated productivity rates because of the exponential decay of light. This inversion approach illustrates the utility of bio-optical models in turbid coastal waters given the measurements of the bulk inherent optical properties.

  2. Ultrafast laser-induced changes in optical properties of semiconductors

    SciTech Connect

    Chirila, C. C.; Lim, Freda C. H.; Gavaza, M. G.

    2012-04-01

    We study the effect of laser radiation on optical properties of semiconductors of industrial interest. The material is pumped with a laser of chosen central frequency, for which the absorption is maximal, thus inducing electron dynamics, which modifies the optical properties. By using an improved theoretical model, we study ultrafast dynamic changes in the refraction index and reflectivity corresponding to a wide frequency-interval of probing radiation and identify that interval where these optical changes are most significant.

  3. Inherent optical properties of the ocean: retrieval of the absorption coefficient of chromophoric dissolved organic matter from airborne laser spectral fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Hoge, Frank E.; Vodacek, Anthony; Swift, Robert N.; Yungel, James K.; Blough, Neil V.

    1995-10-01

    The absorption coefficient of chromophoric dissolved organic matter (CDOM) at 355 nm has been retrieved from airborne laser-induced and water Raman-normalized CDOM fluorescence. Four combined airborne and ship field experiments have demonstrated that (1) the airborne CDOM fluorescence-to--water Raman ratio is linearly related to concurrent quinine-sulfate-standardized CDOM shipboard fluorescence measurements over a wide range of water masses (coastal to blue water); (2) the vicarious calibration of the airborne fluorosensor in units traceable to a fluorescence standard can be established and then maintained over an extended time period by tungsten lamp calibration; (3) the vicariously calibrated airborne CDOM fluorescence-to-water Raman ratio can be directly applied to previously developed

  4. Optical absorption and luminescence study of cobalt-doped magnesium aluminosilicate glass ceramics

    NASA Astrophysics Data System (ADS)

    Malyarevich, A. M.; Denisov, I. A.; Yumashev, K. V.; Dymshits, O. S.; Zhilin, A. A.

    2002-08-01

    Linear and nonlinear optical properties of cobalt-doped magnesium aluminosilicate transparent glass ceramics that were prepared under different conditions have been studied. It has been shown that absorption and luminescence spectra and absorption bleaching of these glass ceramics are defined mainly by tetrahedrally coordinated Co 2+ ions located in magnesium aluminum spinel nanocrystals. The lifetimes of the 4 T 1 ( 4 F) and 4 T 2 ( 4 F) excited states of the tetrahedral Co 2+ ions were found to be in the ranges 2540 and 120450 ns, respectively, depending on the Co concentration. 2002 Optical Society of America

  5. Nonlinear Optical Properties and Applications of Polydiacetylene

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin; Paley, Mark S.; Witherow, William K.; Frazier, Donald O.

    2000-01-01

    Recently, we have demonstrated a picosecond all-optical switch, which also functions as a partial all-optical NAND logic gate using a novel polydiacetylene that is synthesized in our laboratory. The nonlinear optical properties of the polydiacetylene material are measured using the Z-scan technique. A theoretical model based on a three level system is investigated and the rate equations of the system are solved. The theoretical calculations are proven to match nicely with the experimental results. The absorption cross-sections for both the first and higher excited states are estimated. The analyses also show that the material suffers a photochemical change beyond a certain level of the laser power and its physical properties suffer radical changes. These changes are the cause for the partial NAND gate function and the switching mechanism.

  6. Connecting the Silicate Dust and Gas Properties of Distant Galaxies Using Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim; Morrison, Sean

    2016-01-01

    We present recent results from our program investigating the silicate dust properties in distant galaxies using quasar absorption systems. The dust and gas properties of distant galaxies can be characterized by studying the absorption features produced by them along the sightlines to luminous background quasars. Based on our prior finding that silicate dust absorption in z<1.5 quasar absorption systems exhibits a range of optical depths and absorption feature substructures, suggestive of silicate grain property variations, we are investigating silicate dust absorption in quasar absorption systems toward quasars with archival Spitzer Space Telescope Infrared Spectrograph (IRS) spectra. We present our measurements of the 10 and/or 18 micron silicate dust absorption feature(s) in these systems, and discuss constraints on the grain properties, such as composition and crystallinity, based on the shape and substructure present in these features. We also investigate the correlations between the silicate dust properties and the reddening. Connections between the silicate dust and gas phase metal absorption properties can also be probed for some of our targets with archival ground-based spectra. These relationships will yield valuable insights into the star formation history and evolution of metals and dust. This work is supported by NASA through ADAP grant NNX14AG74G and by an award issued by JPL/Caltech, and from US-NSF grant AST-1108830 to the University of South Carolina.

  7. Optical nonlinear absorption characteristics of Sb{sub 2}Se{sub 3} nanoparticles

    SciTech Connect

    Muralikrishna, Molli Kiran, Aditha Sai Ravikanth, B. Sowmendran, P. Muthukumar, V. Sai Venkataramaniah, Kamisetti

    2014-04-24

    In this work, we report for the first time, the nonlinear optical absorption properties of antimony selenide (Sb{sub 2}Se{sub 3}) nanoparticles synthesized through solvothermal route. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies revealed that the nanoparticles are in the range of 10 - 40 nm. Elemental analysis was performed using EDAX. By employing open aperture z-scan technique, we have evaluated the effective two-photon absorption coefficient of Sb{sub 2}Se{sub 3} nanoparticles to be 5e-10 m/W at 532 nm. These nanoparticles exhibit strong intensity dependent nonlinear optical absorption and hence could be considered to have optical power limiting applications in the visible range.

  8. Spectral Absorption and Scattering Properties of Normal and Bruised Apple Tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of the spectral absorption and scattering properties of apple tissue, especially bruised tissue, can help us develop an effective method for detecting bruises during postharvest sorting and grading. This research was intended to determine the optical properties of normal and bruised apple ...

  9. AIR MONITORING BY DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETRY IN BAYTOWN, TEXAS

    EPA Science Inventory

    This report documents the results of a field study carried out in Baytown, Texas in August 1993. ne goal of the field study was to evaluate calibration and audit procedures for a differential optical absorption spectrometry (DOAS) system. he other major goal of the study was to c...

  10. Focused optical and acoustic beams in media with nonlinear absorption

    NASA Astrophysics Data System (ADS)

    Rudenko, O. V.; Sukhorukov, A. A.

    1996-11-01

    Optical and acoustic beams are known to be useful for medical and biological applications, such as diagnostics, surgery, etc. At high intensities both nonlinear lens effects and nonlinear absorption can be significant for the beams. The nonlinear absorption arises due to two-photon optical processes or acoustic shock wave formation. The present work is devoted to the theoretical description of nonlinear beam propagation and focal spot formation taking into account the competition between focusing, diffraction and absorption. We derived a new nonlinear integro- differential equation describing the spatial evolution of the beam width. The general analytical solution of this equation is obtained for arbitrary boundary conditions. The simple formulas are derived for the angle divergence in the far field, as well as for beam width at nonlinear waist. The results of the analysis of these key parameters in different situations are presented.

  11. Tunable enhanced optical absorption of graphene using plasmonic perfect absorbers

    SciTech Connect

    Cai, Yijun; Zhu, Jinfeng; Liu, Qing Huo

    2015-01-26

    Enhancement and manipulation of light absorption in graphene is a significant issue for applications of graphene-based optoelectronic devices. In order to achieve this purpose in the visible region, we demonstrate a design of a graphene optical absorber inspired by metal-dielectric-metal metamaterial for perfect absorption of electromagnetic waves. The optical absorbance ratios of single and three atomic layer graphene are enhanced up to 37.5% and 64.8%, respectively. The graphene absorber shows polarization-dependence and tolerates a wide range of incident angles. Furthermore, the peak position and bandwidth of graphene absorption spectra are tunable in a wide wavelength range through a specific structural configuration. These results imply that graphene in combination with plasmonic perfect absorbers have a promising potential for developing advanced nanophotonic devices.

  12. Optical Properties of Nanosatellite Hardware

    NASA Technical Reports Server (NTRS)

    Finckenor, M. M.; Coker, R. F.

    2014-01-01

    Over the last decade, a number of very small satellites have been launched into space. These have been called nanosatellites (generally of a weight between 1 and 10 kg) or picosatellites (weight <1 kg). This also includes CubeSats, which are based on 10-cm cube units. With the addition of the Japanese Experiment Module (JEM) Small Satellite Orbital Deployer (J-SSOD) to the International Space Station (ISS), CubeSats are easily cycled through the JEM airlock and deployed into space (fig. 1). The number of CubeSats launched since 2003 was approaching 100 at the time of publication, and the authors expect this trend in research to continue, particularly for high school and college flight experiments. Because these spacecraft are so small, there is usually no allowance for shielding or active heating or cooling of the avionics and other hardware. Parts that are usually ignored in the thermal analysis of larger spacecraft may contribute significantly to the heat load of a tiny satellite. In addition, many small satellites have commercial-off-the-shelf (COTS) components. To reduce costs, many providers of COTS components do not include the optical and physical parameters necessary for accurate thermal analysis. Marshall Space Flight Center participated in the development and analysis of the Space Missile Defense Command-Operational Nanosatellite Effect (SMDC-ONE) and the Edison Demonstration of Smallsat Networks (EDSN) nanosatellites. These optical property measurements are documented here in hopes that they may benefit future nanosatellite and picosatellite programs and aid thermal analysis to ensure project goals are met, with the understanding that material properties may vary by vendor, batch, manufacturing process, and preflight handling. Where possible, complementary data are provided from ground simulations of the space environment and flight experiments, such as the Materials on International Space Station Experiment (MISSE) series. NASA gives no recommendation

  13. Optical properties and structure of beryllium lead silicate glasses

    SciTech Connect

    Zhidkov, I. S.; Zatsepin, A. F.; Cholakh, S. O.; Kuznetsova, Yu. A.

    2014-10-21

    Luminescence and optical properties and structural features of (BeO){sub x}(PbO⋅SiO{sub 2}){sub 1−x} glasses (x = 0 ÷ 0.3) are investigated by means of optical absorption and photoluminescence spectroscopy and X-ray diffraction. The regularities of the formation of the optical absorption edge and static disorder are studied. It is shown that the optical absorption and luminescence are determined by transitions between localized states of lead ions. The impact of beryllium oxide on optical and luminescence properties and electronic structure of bands tails is discussed. The presence of two different concentration ranges with various short-range order structure and band tails nature has been established.

  14. Optical absorption of thin film on a Lambertian reflector substrate

    NASA Astrophysics Data System (ADS)

    Sheng, P.

    1984-05-01

    A formula is derived for calculating the optical absorption of thin films deposited on a Lambertian reflector substrate. It is shown that compared with the case of flat reflecting substrate, the incoherent absorption is enhanced by a factor of m x epsilon (1) in the weak absorption limit, where epsilon (1) is the real part of the film dielectric constant and m near two is a slightly varying function of epsilon (1). For a 0.5-micron a-SiH(x) (bandgap 1.7 eV) solar cell with a Lambertian reflector substrate, the total absorption in terms of the short-circuit current is calculated to be 18.63 mA/sq cm.

  15. Marcasite revisited: Optical absorption gap at room temperature

    NASA Astrophysics Data System (ADS)

    Sánchez, C.; Flores, E.; Barawi, M.; Clamagirand, J. M.; Ares, J. R.; Ferrer, I. J.

    2016-03-01

    Jagadeesh and Seehra published in 1980 that the marcasite band gap energy is 0.34 eV. However, recent calculations and experimental approximations accomplished by several research groups point out that the marcasite band gap energy should be quite similar to that of pyrite (of the order of 0.8-1.0 eV). By using diffuse reflectance spectroscopy (DRS) we have determined that marcasite has no optical absorption gap at photon energies 0.06 ≤ hν ≤ 0.75 eV and that it has two well defined optical transitions at ~ 0.9 eV and ~ 2.2 eV quite similar to those of pyrite. Marcasite optical absorption gap appears to be Eg ≅ 0.83 ± 0.02 eV and it is due to an allowed indirect transition.

  16. Nonlinear optical properties of multipyrrole dyes

    PubMed Central

    Frenette, Mathieu; Hatamimoslehabadi, Maryam; Bellinger-Buckley, Stephanie; Laoui, Samir; Bag, Seema; Dantiste, Olivier; Rochford, Jonathan; Yelleswarapu, Chandra

    2014-01-01

    The nonlinear optical properties of a series of pyrrolic compounds consisting of BODIPY and aza-BODIPY systems are investigated using 532 nm nanosecond laser and the Z-scan technique. Results show that 3,5-distyryl extension of BODIPY to the red shifted MeO2BODIPY dye has a dramatic impact on its nonlinear absorption properties changing it from a saturable absorber to an efficient reverse saturable absorbing material with a nonlinear absorption coefficient of 4.64 × 10−10 m/W. When plotted on a concentration scale per mole of dye in solution MeO2BODIPY far outperforms the recognized zinc(II) phthalocyanine dye and is comparable to that of zinc(II) tetraphenylporphyrin. PMID:25242819

  17. Optical properties of polyimide/silica nanocomposite

    NASA Astrophysics Data System (ADS)

    Tommalieh, M. J.; Zihlif, A. M.

    2010-12-01

    The optical properties of thin films of polyimide/silica nanocomposites prepared via sol-gel process were investigated as a function of nanosilica particles content. Absorption and reflectance spectra were collected by a spectrophotometer giving UV-radiation of wavelength range 200-800 nm. The optical data obtained were analyzed in terms of absorption formula for non-crystalline materials. The calculated values of the optical energy gap and the width of the energy tails of the localized states exhibited silica concentration dependence. The direct optical energy gap for neat polyimide is about 1.95 eV, and decreases to a value of 1.8 eV for nanocomposite of 25 wt% nanosilica content. It was found that the calculated refractive index and dielectric constants of nanocomposites increase with silica particles content. The overall dependence of the optical and dielectrical constants on silica content in polyimide matrix is argued on the basis of the observed morphology and overlap of the localized energy sates of different color centers. The EMT model was fitted to the observed dielectric data.

  18. Imaging heterogeneous absorption distribution of advanced breast cancer by optical tomography

    NASA Astrophysics Data System (ADS)

    Xu, Yan; Zhu, Quing

    2010-11-01

    Tumor vascular patterns of advanced breast cancers are complex and heterogeneous. Two typical light absorption patterns of periphery enhancement and posterior shadowing have been observed when imaging these advanced cancers using optical tomography guided by ultrasound. We perform a series simulation and phantom experiments to systemically evaluate the effects of target parameters, target locations, and target optical properties on imaging periphery enhancement absorption distribution using reflection geometry. Large tumors are modeled as concentric semiellipsoidal targets of different outer shell and inner core optical properties. We show that larger targets of more than 3 to 4 cm diameter with outer shell thicknesses less than 1 cm can be resolved at a depth less than 3 cm. A clinical example is given to show the complex vasculature distributions seen from an advanced cancer.

  19. Optical Properties Of Ceramic Fabrics

    NASA Technical Reports Server (NTRS)

    Covington, M. A.; Sawko, P. M.

    1990-01-01

    Report discusses optical properties of ceramic fabrics woven from silica, aluminoborosilicate, and silicon carbide yarns. Directional hemispheric reflectance and transmittance data given for several different weave patterns, yarn constructions, and fabric weights.

  20. Nonreciprocal optical properties in resonant hybrid photonic crystals

    NASA Astrophysics Data System (ADS)

    D'Andrea, A.; Tomassini, N.

    2016-07-01

    The present work is devoted to the theoretical study of the nonreciprocal optical properties in hybrid (isotropic and anisotropic) periodic multilayers for photon energy values chosen close to the electronic energy gaps of semiconductors (excitons). The optical properties of these resonant nonmagnetic photonic crystals, where linear and quadratic spatial dispersion effects are both present, will be studied in the framework of exciton-polariton self-consistent solutions of the Maxwell and Schrödinger equations in the effective-mass approximation. The main interesting optical properties, namely, giant transmission, absorption suppression, and optical unidirectional propagation, will be computed by implementing a two-layer "minimum model."

  1. Optical properties of armchair (7, 7) single walled carbon nanotubes

    SciTech Connect

    Gharbavi, K.; Badehian, H.

    2015-07-15

    Full potential linearized augmented plane waves method with the generalized gradient approximation for the exchange-correlation potential was applied to calculate the optical properties of (7, 7) single walled carbon nanotubes. The both x and z directions of the incident photons were applied to estimate optical gaps, dielectric function, electron energy loss spectroscopies, optical conductivity, optical extinction, optical refractive index and optical absorption coefficient. The results predict that dielectric function, ε (ω), is anisotropic since it has higher peaks along z-direction than x-direction. The static optical refractive constant were calculated about 1.4 (z-direction) and 1.1 (x- direction). Moreover, the electron energy loss spectroscopy showed a sharp π electron plasmon peaks at about 6 eV and 5 eV for z and x-directions respectively. The calculated reflection spectra show that directions perpendicular to the tube axis have further optical reflection. Moreover, z-direction indicates higher peaks at absorption spectra in low range energies. Totally, increasing the diameter of armchair carbon nanotubes cause the optical band gap, static optical refractive constant and optical reflectivity to decrease. On the other hand, increasing the diameter cause the optical absorption and the optical conductivity to increase. Moreover, the sharp peaks being illustrated at optical spectrum are related to the 1D structure of CNTs which confirm the accuracy of the calculations.

  2. Charge-transfer optical absorption mechanism of DNA:Ag-nanocluster complexes

    NASA Astrophysics Data System (ADS)

    Longuinhos, R.; Lúcio, A. D.; Chacham, H.; Alexandre, S. S.

    2016-05-01

    Optical properties of DNA:Ag-nanoclusters complexes have been successfully applied experimentally in Chemistry, Physics, and Biology. Nevertheless, the mechanisms behind their optical activity remain unresolved. In this work, we present a time-dependent density functional study of optical absorption in DNA:Ag4. In all 23 different complexes investigated, we obtain new absorption peaks in the visible region that are not found in either the isolated Ag4 or isolated DNA base pairs. Absorption from red to green are predominantly of charge-transfer character, from the Ag4 to the DNA fragment, while absorption in the blue-violet range are mostly associated to electronic transitions of a mixed character, involving either DNA-Ag4 hybrid orbitals or intracluster orbitals. We also investigate the role of exchange-correlation functionals in the calculated optical spectra. Significant differences are observed between the calculations using the PBE functional (without exact exchange) and the CAM-B3LYP functional (which partly includes exact exchange). Specifically, we observe a tendency of charge-transfer excitations to involve purines bases, and the PBE spectra error is more pronounced in the complexes where the Ag cluster is bound to the purines. Finally, our results also highlight the importance of adding both the complementary base pair and the sugar-phosphate backbone in order to properly characterize the absorption spectrum of DNA:Ag complexes.

  3. Deep seawater inherent optical properties in the Southern Ionian Sea

    NASA Astrophysics Data System (ADS)

    Riccobene, G.; Capone, A.; Aiello, S.; Ambriola, M.; Ameli, F.; Amore, I.; Anghinolfi, M.; Anzalone, A.; Avanzini, C.; Barbarino, G.; Barbarito, E.; Battaglieri, M.; Bellotti, R.; Beverini, N.; Bonori, M.; Bouhadef, B.; Brescia, M.; Cacopardo, G.; Cafagna, F.; Caponetto, L.; Castorina, E.; Ceres, A.; Chiarusi, T.; Circella, M.; Cocimano, R.; Coniglione, R.; Cordelli, M.; Costa, M.; Cuneo, S.; D'Amico, A.; de Bonis, G.; de Marzo, C.; de Rosa, G.; de Vita, R.; Distefano, C.; Falchini, E.; Fiorello, C.; Flaminio, V.; Fratini, K.; Gabrielli, A.; Galeotti, S.; Gandolfi, E.; Grimaldi, A.; Habel, R.; Leonora, E.; Lonardo, A.; Longo, G.; Lo Presti, D.; Lucarelli, F.; Maccioni, E.; Margiotta, A.; Martini, A.; Masullo, R.; Megna, R.; Migneco, E.; Mongelli, M.; Montaruli, T.; Morganti, M.; Musumeci, M.; Nicolau, C. A.; Orlando, A.; Osipenko, M.; Osteria, G.; Papaleo, R.; Pappalardo, V.; Petta, C.; Piattelli, P.; Raffaelli, F.; Raia, G.; Randazzo, N.; Reito, S.; Ricco, G.; Ripani, M.; Rovelli, A.; Ruppi, M.; Russo, G. V.; Russo, S.; Russo, S.; Sapienza, P.; Sedita, M.; Schuller, J.-P.; Shirokov, E.; Simeone, F.; Sipala, V.; Spurio, M.; Taiuti, M.; Terreni, G.; Trasatti, L.; Urso, S.; Valente, V.; Vicini, P.

    2007-02-01

    The NEMO (NEutrino Mediterranean Observatory) Collaboration has been carrying out since 1998 an evaluation programme of deep sea sites suitable for the construction of the future Mediterranean km3 Čerenkov neutrino telescope. We investigated the seawater optical and oceanographic properties of several deep sea marine areas close to the Italian Coast. Inherent optical properties (light absorption and attenuation coefficients) have been measured as a function of depth using an experimental apparatus equipped with standard oceanographic probes and the commercial transmissometer AC9 manufactured by WETLabs. This paper reports on the visible light absorption and attenuation coefficients measured in deep seawater of a marine region located in the Southern Ionian Sea, 60 100 km SE of Capo Passero (Sicily). Data show that blue light absorption coefficient is about 0.015 m-1 (corresponding to an absorption length of 67 m) close to the one of optically pure water and it does not show seasonal variation.

  4. Two-Photon-Absorption Scheme for Optical Beam Tracking

    NASA Technical Reports Server (NTRS)

    Ortiz, Gerardo G.; Farr, William H.

    2011-01-01

    A new optical beam tracking approach for free-space optical communication links using two-photon absorption (TPA) in a high-bandgap detector material was demonstrated. This tracking scheme is part of the canonical architecture described in the preceding article. TPA is used to track a long-wavelength transmit laser while direct absorption on the same sensor simultaneously tracks a shorter-wavelength beacon. The TPA responsivity was measured for silicon using a PIN photodiode at a laser beacon wavelength of 1,550 nm. As expected, the responsivity shows a linear dependence with incident power level. The responsivity slope is 4.5 x 10(exp -7) A/W2. Also, optical beam spots from the 1,550-nm laser beacon were characterized on commercial charge coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) imagers with as little as 13.7 microWatts of optical power (see figure). This new tracker technology offers an innovative solution to reduce system complexity, improve transmit/receive isolation, improve optical efficiency, improve signal-to-noise ratio (SNR), and reduce cost for free-space optical communications transceivers.

  5. Optical Properties of Black Silicon: An Analysis

    NASA Astrophysics Data System (ADS)

    Marthi, Sita Rajyalaxmi; Sekhri, Suramya; Ravindra, N. M.

    2015-09-01

    Silicon (Si) continues to be the dominant semiconducting material used in photovoltaic technology for the manufacture of solar cells. Si, an indirect band gap semiconducting material, has a reflectance of about 30% in the visible range of wavelengths. Standard Si solar cells are not entirely useful in the infrared spectrum region. In order to enhance the performance of silicon solar cells, reflectance losses must be minimized and absorption must be maximized. In the solar cell industry, anti-reflection (AR) coating is used to suppress reflection losses. AR coatings are limited in use because they only reduce the reflectance for a narrow range of wavelengths and incident angle since their functionality is based on a quarter-wavelength coating. Surface texturing is a technique, by which the reflectivity is reduced in a wide range of wavelengths. Black silicon (B-Si) is a material with surface roughness in the micron scale. B-Si, when used instead of crystalline Si (c-Si), offers the possibility to increase the absorption of light in the visible and infrared range of wavelengths. B-Si has a very low reflectivity in the visible range of wavelengths. It exhibits high absorptance in the visible and infrared region. The main objective of this paper is to study the optical properties of B-Si by simulation and compare them with the simulated and experimental optical properties of B-Si and c-Si.

  6. Anomalous nonlinear absorption in epsilon-near-zero materials: optical limiting and all-optical control.

    PubMed

    Vincenti, M A; de Ceglia, D; Scalora, Michael

    2016-08-01

    We investigate nonlinear absorption in films of epsilon-near-zero materials. The combination of large local electric fields at the fundamental frequency and material losses at the harmonic frequencies induce unusual intensity-dependent phenomena. We predict that the second-order nonlinearity of a low-damping, epsilon-near-zero slab produces an optical limiting effect that mimics a two-photon absorption process. Anomalous absorption profiles that depend on low permittivity values at the pump frequency are also predicted for third-order nonlinearities. These findings suggest new opportunities for all-optical light control and novel ways to design reconfigurable and tunable nonlinear devices. PMID:27472631

  7. HAB detection based on absorption and backscattering properties of phytoplankton

    NASA Astrophysics Data System (ADS)

    Lei, Hui; Pan, Delu; Bai, Yan; Chen, Xiaoyan; Zhou, Yan; Zhu, Qiankun

    2011-11-01

    The coastal area of East China Sea (ECS) suffers from the harmful algal blooms (HAB) frequently every year in the warm season. The most common causative phytoplankton algal species of HAB in the ECS in recent years are Prorocentrum donghaiense (dinoflagellates), Karenia mikimotoi (dinoflagellates which could produce hemolytic and ichthyotoxins) and Skeletonema costatum (diatom). The discrimination between the dinoflagellates and diatom HAB through ocean color remote sensing approach can add the knowledge of HAB events in ECS and help to the precaution. A series of in-situ measurement consisted of absorption coefficient, total scattering and particulate backscattering coefficient was conducted in the southern coast of Zhejiang Province in May 2009, and the estuary of Changjiang River in August 2009 and December 2010, which encountered two HAB events and a moderate bloom. The Inherent Optical Properties (IOPs) of the bloom waters have significant difference between phytoplankton species in absorption and backscattering properties. The chlorophyll a specific absorption coefficient (a*phy(λ)) for the bloom patches (chlorophyll a concentration >6mg m-3) differ greatly from the adjacent normal seawater, with the a*phy(λ) of bloom water lower than 0.03 m2 mg-1 while the a*phy(λ) of the adjacent normal seawater is much higher (even up to 0.06 m2 mg-1). Meanwhile, the backscattering coefficients at 6 wavebands (420, 442, 470, 510, 590 and 700nm) are also remarkably lower for bloom waters (<0.01 m-1) than the normal seawater (> 0.02 m-1). The backscattering coefficient ratio (Rbp(λ)) is much lower for diatom bloom waters than for dinoflagellates types (0.01079 vs. 0.01227). A discrimination model based on IOPs is established, and several typical dinoflagellates and diatom bloom events including Prorocentrum donghaiense, Karenia mikimotoi and Skeletonema costatum in the ECS are picked out for testing with the MODIS-L2 and L3 ocean color remote sensing products from NASA

  8. Effective Dirac Hamiltonian for anisotropic honeycomb lattices: Optical properties

    NASA Astrophysics Data System (ADS)

    Oliva-Leyva, M.; Naumis, Gerardo G.

    2016-01-01

    We derive the low-energy Hamiltonian for a honeycomb lattice with anisotropy in the hopping parameters. Taking the reported Dirac Hamiltonian for the anisotropic honeycomb lattice, we obtain its optical conductivity tensor and its transmittance for normal incidence of linearly polarized light. Also, we characterize its dichroic character due to the anisotropic optical absorption. As an application of our general findings, which reproduce the previous case of uniformly strained graphene, we study the optical properties of graphene under a nonmechanical distortion.

  9. Birefringence and anisotropic optical absorption in porous silicon

    SciTech Connect

    Efimova, A. I. Krutkova, E. Yu.; Golovan', L. A.; Fomenko, M. A.; Kashkarov, P. K.; Timoshenko, V. Yu.

    2007-10-15

    The refractive indices and the coefficients of optical absorption by free charge carriers and local vibrations in porous silicon (por-Si) films, comprising nanometer-sized silicon residues (nanocrystals) separated by nanometer-sized pores (nanopores) formed in the course of electrochemical etching of the initial single crystal silicon, have been studied by polarization-resolved IR absorption spectroscopy techniques. It is shown that the birefringence observed in por-Si is related to the anisotropic shapes of nanocrystals and nanopores, while the anisotropy (dichroism) of absorption by the local vibrational modes is determined predominantly by the microrelief of the surface of nanocrystals. It is demonstrated that silicon-hydrogen surface bonds in nanocrystals can be restored by means of selective hydrogen thermodesorption with the formation of a considerable number of H-terminated surface Si-Si dimers.

  10. Neuron absorption study and mid-IR optical excitations

    NASA Astrophysics Data System (ADS)

    Guo, Dingkai; Chen, Xing; Vadala, Shilpa; Leach, Jennie; Kostov, Yordan; Bewley, William W.; Kim, Chul-Soo; Kim, Mijin; Canedy, Chadwick L.; Merritt, Charles D.; Vurgaftman, Igor; Meyer, Jerry R.; Choa, Fow-Sen

    2012-02-01

    Neuronal optical excitation can provide non-contacting tools to explore brain circuitry and a durable stimulation interface for cardiac pacing and visual as well as auditory sensory neuronal stimulation. To obtain accurate absorption spectra, we scan the transmission of neurons in cell culture medium, and normalize it by subtracting out the absorption spectrum of the medium alone. The resulting spectra show that the main neuronal absorption peaks are in the 3000- 6000nm band, although there is a smaller peak near 1450nm. By coupling the output of a 3μm interband cascade laser (ICL) into a mid-IR fluorozirconate fiber, we can effectively deliver more than 1J/cm2 photon intensity to the excitation site for neuronal stimulation.

  11. Probing molecular chirality by coherent optical absorption spectra

    SciTech Connect

    Jia, W. Z.; Wei, L. F.

    2011-11-15

    We propose an approach to sensitively probe the chirality of molecules by measuring their coherent optical-absorption spectra. It is shown that quantum dynamics of the cyclic three-level chiral molecules driven by appropriately designed external fields is total-phase dependent. This will result in chirality-dependent absorption spectra for the probe field. As a consequence, the charality-dependent information in the spectra (such as the locations and relative heights of the characteristic absorption peaks) can be utilized to identify molecular chirality and determinate enantiomer excess (i.e., the percentages of different enantiomers). The feasibility of the proposal with chiral molecules confined in hollow-core photonic crystal fiber is also discussed.

  12. Absorption and spectra of optical parameters in amorphous solid solutions of the Se-S system

    SciTech Connect

    Djalilov, N. Z.; Damirov, G. M.

    2011-04-15

    A study of the optical properties of the Se-S system has revealed a correlation between the dependences of optical absorption coefficient {alpha}, effective concentration of charged defects N{sub t}, and characteristic energy E{sub 0} corresponding to the Urbach optical absorption in the spectral region where the Urbach rule works for the Se-S system on the S concentration. These optical properties are controlled by charged defects. It is shown that concentrations of intrinsic charged defects can be changed by variation in composition of the Se-S system. Reflectance spectra of amorphous solid solutions of the Se-S system are studied within the energy range 1-6 eV. Using the Kramers-Kronig method, spectral dependences of optical constants and derivative optical and dielectric functions are calculated. Variation in the spectra of optical parameters with composition of the Se-S system are explained within a cluster model in which the density of electron states is a function of atomic configurations in clusters, i.e., of the character of a short-range order.

  13. Remark on: the neutron spherical optical-model absorption.

    SciTech Connect

    Smith, A. B.; Nuclear Engineering Division

    2007-06-30

    The energy-dependent behavior of the absorption term of the spherical neutron optical potential for doubly magic {sup 208}Pb and the neighboring {sup 209}Bi is examined. These considerations suggest a phenomenological model that results in an intuitively attractive energy dependence of the imaginary potential that provides a good description of the observed neutron cross sections and that is qualitatively consistent with theoretical concepts. At the same time it provides an alternative to some of the arbitrary assumptions involved in many conventional optical-model interpretations reported in the literature and reduces the number of the parameters of the model.

  14. Ultraviolet optical absorptions of semiconducting copper phosphate glasses

    NASA Technical Reports Server (NTRS)

    Bae, Byeong-Soo; Weinberg, Michael C.

    1993-01-01

    Results are presented of a quantitative investigation of the change in UV optical absorption in semiconducting copper phosphate glasses with batch compositions of 40, 50, and 55 percent CuO, as a function of the Cu(2+)/Cu(total) ratio in the glasses for each glass composition. It was found that optical energy gap, E(opt), of copper phosphate glass is a function of both glass composition and Cu(2+)/Cu(total) ratio in the glass. E(opt) increases as the CuO content for fixed Cu(2+)/Cu(total) ratio and the Cu(2+)/Cu(total) ratio for fixed glass composition are reduced.

  15. Local optical absorption spectra of h-BN–MoS2 van der Waals heterostructure revealed by scanning near-field optical microscopy

    NASA Astrophysics Data System (ADS)

    Nozaki, Junji; Kobayashi, Yu; Miyata, Yasumitsu; Maniwa, Yutaka; Watanabe, Kenji; Taniguchi, Takashi; Yanagi, Kazuhiro

    2016-06-01

    Van der Waals (vdW) heterostructures, in which different two-dimensional layered materials are stacked, can exhibit unprecedented optical properties. Development of a technique to clarify local optical properties of vdW heterostructures is of great importance for the correct understanding of their backgrounds. Here, we examined local optical absorption spectra of h-BN–MoS2 vdW heterostructures by scanning near-field microscopy measurements with a spatial resolution of 100 nm. In an as-grown sample, there was almost no site dependence of their optical absorption spectra. However, in a degraded sample where defects and deformations were artificially induced, a significant site-dependence of optical absorption spectra was observed.

  16. Study on the elemental mercury absorption cross section based on differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zheng, Haiming; Yao, Penghui

    2015-08-01

    With the method of ultraviolet absorption spectrum, the exact absorption cross-section with the light source of the low-pressure mercury lamp was determined, during which the optimum wavelength for mercury concentrations inversion was 253.69 nm, the highest detection limit was 0.177 μg/cm3, and the lowest detection limit was 0.034 μg/cm3. Furthermore, based on the differential optical absorption spectroscopy(DOAS), the relationship between the integral parameters (IP) and the concentration as well as the signal-noise ration (SNR) under the conditions of gas flow was determined and the lowest detection limit was figured out to be 0.03524 μg/cm3, providing a method of DOAS to de-noise through the comparison between the mercury concentration values produced by DOAS and that produced by the wavelet de-noising method (db5). It turned out that the differential optical absorption spectroscopy had a strong anti-interference ability, while the wavelet de-noising method was not suitable for measuring the trace concentration change.

  17. Optical absorption spectrum of Cu 2+ in calcium tartrate tetrahydrate

    NASA Astrophysics Data System (ADS)

    Swamy, Y. K. R.; Reddy, P. P.; Reddy, Y. P.

    1980-02-01

    Copper doped single crystals of calcium tartrate tetrahydrate are grown from silica gel. The optical absorption spectrum is investigated with polarised and unpolarised beams of incident light. The spectrum is attributed to the Cu 2+ ion in C 4V symmetry associated with spin-orbit coupling. The following crystal field parameters are evaluated: Dq = 1000 cm -1; λ = -830 cm -1; Ds = 1540 cm -1; Dt = 470 cm -1.

  18. Electron paramagnetic resonance and optical absorption spectral studies on chalcocite

    NASA Astrophysics Data System (ADS)

    Reddy, S. Lakshmi; Fayazuddin, Md.; Frost, Ray L.; Endo, Tamio

    2007-11-01

    A chalcocite mineral sample of Shaha, Congo is used in the present study. An electron paramagnetic resonance (EPR) study on powdered sample confirms the presence of Mn(II), Fe(III) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. Mid-infrared results are due to water and sulphate fundamentals.

  19. Electron paramagnetic resonance and optical absorption spectral studies on chalcocite.

    PubMed

    Reddy, S Lakshmi; Fayazuddin, Md; Frost, Ray L; Endo, Tamio

    2007-11-01

    A chalcocite mineral sample of Shaha, Congo is used in the present study. An electron paramagnetic resonance (EPR) study on powdered sample confirms the presence of Mn(II), Fe(III) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. Mid-infrared results are due to water and sulphate fundamentals. PMID:17324611

  20. Electronic structure and optical properties of resin

    NASA Astrophysics Data System (ADS)

    Rao, Zhi-Fan; Zhou, Rong-Feng

    2013-03-01

    We used the density of functional theory (DFT) to study the electronic structure and density of states of resin by ab initio calculation. The results show the band gap of resin is 1.7 eV. The covalent bond is combined C/O atoms with H atoms. The O 2p orbital is the biggest effect near the Fermi level. The results of optical properties show the reflectivity is low, and the refractive index is 1.7 in visible light range. The highest absorption coefficient peak is in 490 nm and the value is 75,000.

  1. Optical properties of graphene nanoflakes: Shape matters

    NASA Astrophysics Data System (ADS)

    Mansilla Wettstein, Candela; Bonafé, Franco P.; Oviedo, M. Belén; Sánchez, Cristián G.

    2016-06-01

    In recent years there has been significant debate on whether the edge type of graphene nanoflakes (GNFs) or graphene quantum dots (GQDs) are relevant for their electronic structure, thermal stability, and optical properties. Using computer simulations, we have proven that there is a fundamental difference in the absorption spectra between samples of the same shape, similar size but different edge type, namely, armchair or zigzag edges. These can be explained by the presence of electronic structures near the Fermi level which are localized on the edges. These features are also evident from the dependence of band gap on the GNF size, which shows three very distinct trends for different shapes and edge geometries.

  2. Optical properties of flyash

    SciTech Connect

    Self, S.A.

    1990-04-01

    In this research program, we have adopted the approach that by measuring fundamental properties (i.e, the complex refractive index, m) of the fly ash which participates in the radiation transfer, we can use well established theoretical principles (Mie theory) to compute the radiative properties of dispersions of fly ash as found in coal combustors. With this approach one can, understand the underlying principles that affect the radiative properties of an ash dispersion and more confidently predict how variations in the characteristics of the ash dispersion cause variations in its radiative properties. An important criterion in this approach is that the fly ash particles be spherical, homogeneous, and isotropic. Fortunately, fly ash particles are formed at high temperatures at which most of them are molten, leading primarily to spherical particles. Furthermore, one should expect that molten particles will be reasonably homogeneous and isotropic. On cooling, most fly ash particles form glassy spheres which are homogeneous and isotropic. Some ash particles form hollow shells (cenospheres) while others form as particles with bubbles'' or voids, but most fly ash particles are well approximated as homogeneous isotropic spheres. In the following sections we review some of the underlying principles that affect the radiative properties of fly ash dispersions and report on progress that has been made during the past quarter.

  3. Greatly Enhanced Optical Absorption of a Defective MoS2 Monolayer through Oxygen Passivation.

    PubMed

    Shu, Huabing; Li, Yunhai; Niu, Xianghong; Wang, Jinlan

    2016-05-25

    Structural defects in the molybdenum disulfide (MoS2) monolayer are widely reported and greatly degrade the transport and photoluminescence. However, how they influence the optical absorption properties remains unclear. In this work, by employing many-body perturbation theory calculations, we investigate the influence of sulfur vacancies (SVs), the main type of intrinsic defects in the MoS2 monolayer, on the optical absorption and exciton effect. Our calculations reveal that the presence of SVs creates localized midgap states in the bandgap, which results in a dramatic red-shift of the absorption peak and stronger absorbance in the visible light and near-infrared region. Nevertheless, the SVs can be finely repaired by oxygen passivation and are beneficial to the formation of the stable localized excitons, which greatly enhance the optical absorption in the spectral range. The defect-mediated/-engineered absorption mechanism is well understood, which offers insightful guides for improving the performance of two-dimensional dichalcogenide-based optoelectronic devices. PMID:27144902

  4. Optical constants and transient absorption of solution-deposited RuO2 thin films

    NASA Astrophysics Data System (ADS)

    Owrutsky, Jeffrey; Compton, Ryan; Long, James; Chrevin, Christopher; Bussmann, Konrad; Dunkelberger, Adam; Spann, Bryan; Palin, Irina; Rolison, Debra; Cunningham, Paul; Melinger, Joseph; Desario, Paul; Weidinger, Dan; Heilweil, Edwin

    2015-03-01

    Optical and electrical conductivity properties are determined for the promising, broadband transparent conductor material, solution-deposited RuO2 nanostructured films. The 10-30 nm thick films or nanoskins are less conductive but more optically transmissive than polycrystalline, sputtered RuO2 films which are inherently metallic. The optical constants (0.6 to 4.5 eV) determined by ellipsometry show that ɛ1 is positive for the nanoskins in the spectral region investigated so they are not plasmonic. Transient picosecond absorption with visible (400 nm) pump and various probe wavelengths (visible and THz) are performed for nanoskins calcined to different temperatures. When heated to 200°C the absorption increases in the visible and THz. After heating to 300°C, the films become more polycrystalline and there is evidence for the appearance of a new absorption. Deceased absorptions or bleaches are observed in the THz and for longer visible wavelengths (> 750 nm). The absorption is ascribed to a damped plasmon band of the crystalline nanoparticles formed in the film upon heating.

  5. Fabricating silver nanoplate/hybrid silica gel glasses and investigating their nonlinear optical absorption behavior

    NASA Astrophysics Data System (ADS)

    Zheng, Chan; Wenzhe, Chen; Xiaoyun, Ye; Cai, Shuguang; Xiao, Xueqing

    2014-03-01

    Silver nanoplate/hybrid silica gel glasses were prepared via the sol-gel technique. Analysis of ultraviolet-visible spectroscopy extinction spectra confirmed the successful incorporation of silver nanoplates into the hybrid silica gel glasses. The silver nanoplate/hybrid silica gel glass composites are completely noncrystalline because of their low doping level compared with that of the silica matrix. The nonlinear optical absorption behavior of the silver nanoplate/hybrid silica gel glass composites was studied via open-aperture Z-scan technique with 4 ns pulse durations at 532 nm and 1064 nm. The nonlinear optical properties of silver nanoplates are maintained after they were introduced into silica gel glasses. Furthermore, the silver nanoplate/hybrid silica gel glasses exhibit intensity-dependent transformation from saturable absorption (SA) to reverse saturable absorption (RSA). The SA behavior at low excitation intensity can be attributed to the bleaching of ground-state surface plasmon resonance absorption induced by the retarded electronic relaxation process in solid-state gel glasses. By contrast, the RSA at high incident influence may have resulted from excited-state absorption and two-photon absorption.

  6. Optical limiting and dynamical two-photon absorption of porphyrin with ruthenium outlying complexes for a picosecond pulse train

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Jin; Sun, Yu-Ping; Wang, Chuan-Kui

    2016-01-01

    Propagation and nonlinear optical absorption of a picosecond pulse train in strong reverse saturable absorption (RSA) materials (free-based tetrapyridyl porphyrin H2TPyP with ruthenium (Ru) outlying complexes) are investigated by solving coupled rate equations and field intensity equation. Influence of outlying Ru groups on optical limiting (OL) properties is studied. Propagation of the front subpulses is mainly affected by linear transition between the ground state and the first excited singlet state, while intensity of the latter subpulses is attenuated by the excited state absorption (ESA). These two different absorption mechanisms result in asymmetric distribution of the transmitted pulse. It is shown that effective population transfer time from the ground state to the lowest triplet state and RSA play important roles in the OL performance and pulse shaping. Moreover, our results indicate that the porphyrins studied are ideal optical limiters because of their large ESA cross section and long lifetime of the lowest triplet state. Compounds with the presence of Ru group possess preferable power limiting ability. Ligand group attached to Ru also influences the nonlinear optical absorption of compounds. Special attention has been paid on dynamical two-photon absorption (TPA) cross section which depends crucially on the duration of the subpulse as well as time interval between subpulses. The present study provides a way to modulate nonlinear optical absorption properties of the medium by changing parameters of the pulse train.

  7. Optical properties of photochromic and thermochromic materials

    NASA Astrophysics Data System (ADS)

    Mo, Yeon-Gon

    The optical properties of some thin film materials can be altered by an external stimulus. Photochromic and thermochromic materials, including inorganic and organic substances, have optical properties that can be changed in a reversible manner by irradiation and temperature respectively. These materials can be used in applications such as radiation or thermal sensors, information storage devices and smart window applications in buildings and cars. In this work, major effort was concentrated on passive thermal control coatings based on photochromic and thermochromic materials. The inorganic photochromic materials were based on tungsten and molybdenum oxide films and the organic photochromic materials included spiropyrans and spirooxazines. In addition, photochromic composite organic-inorganic films and thermochromic vanadium oxide films were prepared. The samples were synthesized using sputtering, sol-gel process, and thermal oxidation. The optical properties were investigated for the first time by ultraviolet/visible/infrared (UV/VIS/IR) spectroscopic ellipsometry, attenuated total reflection (ATR) infrared ellipsometry, spectrophotometry, and X-ray diffraction (XRD). For amorphous oxide films, the oxygen deficiency was important in determining the photochromic properties of the films. In the mid-infrared region, no photochromism was observed for the films. The optical properties of organic-inorganic composite films changed in the VIS/NIR wavelength region markedly in a reversible process, with UV irradiation. The composite films containing tungsten heteropolyoxometalate (HPOM) showed faster coloration and bleaching than pure tungsten oxide films. The composite films with molybdenum HPOM showed faster coloration and much slower bleaching than tungsten HPOM. The spiropyran and spirooxazine doped polymeric films were investigated for the first time using infrared and ATR ellipsometry. The infrared optical functions obtained by ATR measurements were a little smaller

  8. Impact of Foliage Surface Properties on Vegetation Reflection and Absorption

    NASA Astrophysics Data System (ADS)

    Yang, B.; Knyazikhin, Y.; Yan, L.; Zhao, Y.; Jiao, J.

    2013-12-01

    Optical properties of phytoelements and their distribution in the canopy space (i.e., canopy structure) are among key factors that determine light environment in vegetation canopies, which in turn drives various physiological and physical processes required for the functioning of plants. Canopy radiative response is the source of information about ecosystem properties from remote sensing. Understanding of how radiation interacts with foliage and traverses in the 3D vegetation canopy is essential to both modeling and remote sensing communities. Radiation scattered by a leaf includes information from two dissimilar sources - the leaf surface and leaf interior. The first component of scattered radiation emanates from light reflected at the air-cuticle interface. This portion of reflected radiation does not interact with biochemical constituents inside the leaf and depends on the properties of the leaf surface. The leaf cuticle acts as a "barrier" for photons to enter the mesophyll and be absorbed; thus, tending to increase the leaf scattering. The second component mainly results from radiation interactions within the leaf-interior. The canopy radiation regime is sensitive to canopy structure, leaf surface properties and leaf biochemical constituents. Impact of leaf surface properties on canopy reflection and absorption is poorly understood. Radiation scattered at the surface of leaves is partly polarized. Fresnel reflection is the principal cause of light polarization. Polarization measurements provide a means to assess the impact of leaf surface properties on canopy radiation regime. We measured Bidirectional Reflectance Factor (BRF) in the principal plane and its polarized portion of needles and shoots of two coniferous species in the 400 to 1000 nm spectral interval. The needle and shoot BRF spectra were decomposed into polarized (PBRF) and diffuse (DBRF) components: BRF=PBRF+DBRF. Our analyses indicate: 1) PBRF in forward directions can account for up to 70% of

  9. The effect of film thickness on the optical absorption edge and optical constants of the Cr(III) organic thin films

    NASA Astrophysics Data System (ADS)

    Yakuphanoglu, F.; Sekerci, M.; Balaban, A.

    2005-05-01

    The effect of film thickness on optical properties of the Cr(III) complex having 2-pyridincarbaldehye thiosemicarbazone thin films was investigated. The analyses of the optical absorption data revealed existence of direct and indirect transitions in the optical band gap. The optical constants (refractive index and dielectric constant) of the thin films were determined. The thickness of the films causes important changes in refractive index and real part-imaginary parts of the dielectric constant. The most significant result of the present study is to indicate that thickness of the film can be used to modify in the optical band gaps and optical constant of the thin films.

  10. Nonlinear optical absorption and refraction in a strained anisotropic multi-level quantum dot system

    NASA Astrophysics Data System (ADS)

    Negi, C. M. S.; Gupta, Saral K.; Kumar, Dharmendra; Kumar, Jitendra

    2013-08-01

    Linear and nonlinear optical properties of disc shaped anisotropic multi-level quantum dot (QD) system has been theoretically investigated. The effect of dot size, shape anisotropy, strain and incident optical intensity on linear absorption, nonlinear absorption and nonlinear refractive index has been explored. The QD is modeled by in-plane anisotropic parabolic potential along x-y plane and by finite well potential along growth direction (z-axis). The contribution of strain is incorporated through various deformation potentials. The energy and wave function calculations are performed by multi-band envelope function approach based on k.p theory. The formulation is applied to the CdSe/CdS QD system. The numerical results show that, dot size, anisotropy and optical intensity have important effect on linear and nonlinear optical properties. The effect of strain is simultaneous red and blue shift of heavy hole (hh) and light hole (lh) transitions, respectively, which is clearly visible in terms of well resolved optical spectra. The theoretical results obtained are compared with the available experimental data and the results are in good agreement. Large blue shift and enhancement in magnitude of linear and nonlinear optical spectra of QD with size, anisotropy and strain make QD a promising candidate for application in tunable Nano-optoelectronic devices.

  11. Assessing multiple quality attributes of peaches using spectral absorption and scattering properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to measure the spectral absorption and reduced scattering coefficients of peaches, using a hyperspectral imaging-based spatially-resolved method, for maturity/quality assessment. A newly developed optical property measuring instrument was used for acquiring hypersp...

  12. Molecular level all-optical logic with chlorophyll absorption spectrum and polarization sensitivity

    NASA Astrophysics Data System (ADS)

    Raychaudhuri, B.; Bhattacharyya (Bhaumik), S.

    2008-06-01

    Chlorophyll is suggested as a suitable medium for realizing optical Boolean logic at the molecular level in view of its wavelength-selective property and polarization sensitivity in the visible region. Spectrophotometric studies are made with solutions of total chlorophyll and chromatographically isolated components, viz. chlorophyll a and b and carotenoids extracted from pumpkin leaves of different maturity stages. The absorption features of matured chlorophyll with two characteristic absorption peaks and one transmission band are molecular properties and independent of concentration. A qualitative explanation of such an absorption property is presented in terms of a ‘particle in a box’ model and the property is employed to simulate two-input optical logic operations. If both of the inputs are either red or blue, absorption is high. If either one is absent and replaced by a wavelength of the transmission band, e.g. green, absorption is low. Assigning these values as 0 s or 1 s, AND and OR operations can be performed. A NOT operation can be simulated with the transmittance instead of the absorbance. Also, the shift in absorbance values for two different polarizations of the same monochromatic light can simulate two logical states with a single wavelength. Cyclic change in absorbance is noted over a rotation of 360° for both red and blue peaks, although the difference is not very large. Red monochromatic light with polarizations apart by 90°, corresponding to maximum and minimum absorption, respectively, may be assigned as the two logical states. The fluorescence emissions for different pigment components are measured at different excitation wavelengths and the effect of fluorescence on the red absorbance is concluded to be negligible.

  13. Third order nonlinear optical susceptibility of fluorescein-containing polymers determined by electro-absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Gomez-Sosa, Gustavo; Beristain, Miriam F.; Ortega, Alejandra; Martínez-Viramontes, Jaquelin; Ogawa, Takeshi; Fernández-Hernández, Roberto C.; Tamayo-Rivera, Lis; Reyes-Esqueda, Jorge-Alejandro; Isoshima, Takashi; Hara, Masahiko

    2012-03-01

    Novel polymers containing xanthene groups with high dye concentrations were prepared, and their third order nonlinear optical properties were studied by electroabsorption spectroscopy technique. The polymers were amorphous with refractive indices above 1.6 in the non-resonant region. The UV-Visible absorption spectra indicate the fluoresceins molecules in the polymers are H-aggregated. They showed third order nonlinear susceptibility, χ(3) (-ω:ω, 0, 0), of 2.5-3.5 × 10-12 esu.

  14. Thermo-optical Properties of Nanofluids

    NASA Astrophysics Data System (ADS)

    Ortega, Maria Alejandra; Rodriguez, Luis; Castillo, Jimmy; Fernández, Alberto; Echevarria, Lorenzo

    2008-04-01

    In this work, we report thermo-optical properties of nanofluids. Spherical gold nanoparticles obtained by laser ablation in condensed media were characterized using thermal lens spectroscopy in SDS-water solution pumping at 532 nm with a 10 ns pulsed laser-Nd-YAG system. Nanoparticles obtained by laser ablation were stabilized in the time by surfactants (Sodium Dodecyl-Sulfate or SDS) in different molar concentrations. The morphology and size of the gold nanoparticles were determined by transmission electron microscopy (TEM). The plasmonic resonance bands in gold nanoparticles are responsible of the light optical absorption of this wavelength. The position of the absorption maximum and width band in the UV-Visible spectra is given by the morphological characteristics of these systems. The thermo-optical constant such as thermal diffusion, thermal conductivity and dn/dT are functions of nanoparticles sizes and dielectric constant of the media. The theoretical model existents do not describe completely this relations because is not possible separate the contributions due to nanoparticles size, factor form and dielectric constant. The thermal lens signal obtained is also dependent of nanoparticles sizes. This methodology can be used in order to evaluate nanofluids and characterizing nanoparticles in different media. These results are expected to have an impact in bioimaging, biosensors and other technological applications such as cooler system.

  15. Thermo-optical Properties of Nanofluids

    SciTech Connect

    Ortega, Maria Alejandra; Echevarria, Lorenzo; Rodriguez, Luis; Castillo, Jimmy; Fernandez, Alberto

    2008-04-15

    In this work, we report thermo-optical properties of nanofluids. Spherical gold nanoparticles obtained by laser ablation in condensed media were characterized using thermal lens spectroscopy in SDS-water solution pumping at 532 nm with a 10 ns pulsed laser-Nd-YAG system. Nanoparticles obtained by laser ablation were stabilized in the time by surfactants (Sodium Dodecyl-Sulfate or SDS) in different molar concentrations. The morphology and size of the gold nanoparticles were determined by transmission electron microscopy (TEM). The plasmonic resonance bands in gold nanoparticles are responsible of the light optical absorption of this wavelength. The position of the absorption maximum and width band in the UV-Visible spectra is given by the morphological characteristics of these systems. The thermo-optical constant such as thermal diffusion, thermal conductivity and dn/dT are functions of nanoparticles sizes and dielectric constant of the media. The theoretical model existents do not describe completely this relations because is not possible separate the contributions due to nanoparticles size, factor form and dielectric constant. The thermal lens signal obtained is also dependent of nanoparticles sizes. This methodology can be used in order to evaluate nanofluids and characterizing nanoparticles in different media. These results are expected to have an impact in bioimaging, biosensors and other technological applications such as cooler system.

  16. [Retrieval of monocyclic aromatic hydrocarbons with differential optical absorption spectroscopy].

    PubMed

    Xie, Pin-Hua; Fu, Qiang; Liu, Jian-Guo; Liu, Wen-Qing; Qin, Min; Li, Ang; Liu, Shi-Sheng; Wei, Qing-Nong

    2006-09-01

    Differential optical absorption spectroscopy (DOAS) technique has been used to measure trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range, e. g. SO2, NO2, O3 etc. However, unlike the absorption spectra of SO2 and NO2, the analysis of aromatic compounds is difficult and strongly suffers from the cross interference of other absorbers (Herzberg bands of oxygen, ozone and sulfur dioxide), especially with relatively low concentrations of aromatic compounds in the atmosphere. In the present paper, the DOAS evaluation of aromatic compounds was performed by nonlinear least square fit with two interpolated oxygen optical density spectra at different path lengths and reference spectra of ozone at different temperature and SO2 cross section to correct the interference from absorbers of O2, O3 and SO2. The measurement of toluene, benzene, (m, p, o) xylene and phenol with a DOAS system showed that DOAS method is suitable for monocyclic aromatic compounds monitoring in the atmosphere. PMID:17112022

  17. Interpretation of the optical absorption spectrum of Co3O4 with normal spinel structure from first principles calculations

    NASA Astrophysics Data System (ADS)

    Lima, A. F.

    2014-01-01

    First principles calculations based on density functional theory have been employed to study the electronic, magnetic and optical properties of Co3O4 in a cubic normal spinel structure. Exchange and correlation effects between electrons were treated by a B3PW91 hybrid functional, which produced better results than others scheme, such as GGA+U or PBE0 hybrid functionals or mBJ semilocal potential. The work focuses on clarifying the nature of the optical absorption bands, which have motivated various theoretical and experimental works in the literature. The calculated optical absorption spectrum was compared with available experimental data. On the basis of this calculated electronic and magnetic structure, the optical absorption peaks (theoretical and experimental) could be satisfactorily explained in terms of d3d charge transfer transitions between both CO2+→CO2+ and CO3+→CO3+ ions. The calculations also predicted that the crystal field splittings at both octahedral and tetrahedral sites in the Co3O4 compound are of the same magnitude. First principles calculations were used to predict optical properties of Co3O4. Exchange-correlation electronic effects were treated by a B3PW91 hybrid functional. Calculated optical absorption spectrum was compared with experimental data. Optical absorption peaks could be satisfactorily explained.

  18. Femtosecond nonlinear optical properties of carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Dan; Liu, Ye; Yang, Heqing; Qian, Shixiong

    2002-09-01

    The nonlinear optical properties and ultrafast electron-relaxation dynamics of carbon nanoparticles were investigated by using the femtosecond optical Kerr effect and pump-probe techniques. The blueshift of the absorption edge with the decrease of the size of the nanoparticles reveals the opening of the gap. The magnitude of chi(3) for carbon nanoparticles is calculated to be 8.3 x10-13 esu, which arises from the contribution of delocalized feature of the pi electrons. The decay of photobleaching includes a fast and a slow component, which are assigned to the relaxation of the free carriers and trapped carriers, respectively. It is found that the lifetimes of two components of bleaching decrease as temperature of heat treatment is increased.

  19. Optical Absorption Spectra of Hydrous Wadsleyite to 32 GPa

    NASA Astrophysics Data System (ADS)

    Thomas, S.; Goncharov, A. F.; Jacobsen, S. D.; Bina, C. R.; Frost, D. J.

    2009-05-01

    Optical absorption spectra of high-pressure minerals can be used as indirect tools to calculate radiative conductivity of the Earth's interior [e.g., 1]. Recent high-pressure studies show that e.g. ringwoodite, γ-(Mg,Fe)2SiO4, does not become opaque in the near infrared and visible region, as previously assumed, but remains transparent to 21.5 GPa [2]. Therefore, it has been concluded that radiative heat transfer does not necessarily become blocked at high pressures of the mantle and ferromagnesian minerals actually could contribute to the heat flow in the Earth's interior [2]. In this study we use gem-quality single-crystals of hydrous Fe-bearing wadsleyite, β-(Mg,Fe)2SiO4, that were synthesized at 18 GPa and 1400 °C in a multianvil apparatus. Crystals were analyzed by Mössbauer and Raman spectroscopy, electron microprobe analysis and single-crystal X-ray diffraction. For absorption measurements a double-polished 50 μm sized single-crystal of wadsleyite was loaded in a diamond-anvil cell with neon as pressure medium. Optical absorption spectra were recorded at ambient conditions as well as up to 32 GPa from 400 to 50000 cm-1. At ambient pressure the absorption spectrum reveals two broad bands at - 10000 cm-1 and -15000 cm-1, and an absorption edge in the visible-ultraviolet range. With increasing pressure the absorption spectrum changes, both bands continuously shift to higher frequencies as has been observed for ringwoodite [2], but is contrary to earlier presumptions for wadsleyite [3]. Here, we will discuss band assignment along with the influence of iron, compare our results to previous absorption studies of mantle materials [2], and analyze possible implications for radiative conductivity of the transition zone. References: [1] Goncharov et al. (2008), McGraw Yearbook Sci. Tech., 242-245. [2] Keppler & Smyth (2005), Am. Mineral., 90 1209-1212. [3] Ross (1997), Phys. Chem. Earth, 22 113-118.

  20. Optical properties of silver nano-cubes

    NASA Astrophysics Data System (ADS)

    Das, Ratan; Sarkar, Sumit

    2015-10-01

    Here in this work we are interested in the optical properties of uniform sized cubic silver nano-crystals. These silver nano-crystals are prepared by simple chemical reduction method using PVP as a capping agent. High Resolution Transmission Electron Microscopy (HRTEM) images and X-ray diffraction (XRD) analysis reveal that the produced nano-crystals are FCC in structure with a cubic morphology having an average size of 100 nm approximately. Further High Performance Liquid Chromatography (HPLC) study reveals the monodispersity of the prepared sample. UV/Vis study shows an absorption peak due to surface plasmon resonance (SPR) in the visible range which remains steady for more than two months and after that absorption peak position gets red shifted slowly as samples becomes more aged, confirming the agglomeration after two months. Most important optical property shown by the sample is the photoluminescence (PL), which gives an emission spectra in the visible range, confirming a band gap in the silver nano-cubes. It has been observed that the different PL spectra show an emission peak at 482 nm with different intensity for different excitation wavelength.

  1. Calculating nonlocal optical properties of structures with arbitrary shape.

    SciTech Connect

    McMahon, J. M.; Gray, S. K.; Schatz, G. C.; Northwestern Univ.

    2010-07-16

    In a recent Letter [J. M. McMahon, S. K. Gray, and G. C. Schatz, Phys. Rev. Lett. 103, 097403 (2009)], we outlined a computational method to calculate the optical properties of structures with a spatially nonlocal dielectric function. In this paper, we detail the full method and verify it against analytical results for cylindrical nanowires. Then, as examples of our method, we calculate the optical properties of Au nanostructures in one, two, and three dimensions. We first calculate the transmission, reflection, and absorption spectra of thin films. Because of their simplicity, these systems demonstrate clearly the longitudinal (or volume) plasmons characteristic of nonlocal effects, which result in anomalous absorption and plasmon blueshifting. We then study the optical properties of spherical nanoparticles, which also exhibit such nonlocal effects. Finally, we compare the maximum and average electric field enhancements around nanowires of various shapes to local theory predictions. We demonstrate that when nonlocal effects are included, significant decreases in such properties can occur.

  2. Nonlinear optical properties of bacteriorhodopsin

    NASA Astrophysics Data System (ADS)

    Hendrickx, Eric; Verbiest, Thierry; Clays, Koen J.; Persoons, Andre P.

    1993-04-01

    In this paper we show the applicability of Hyper-Rayleigh scattering to obtain hyperpolarizabilities of ionic and biochemical compounds. It was found that dark-adapted bacteriorhodopsin and its isolated chromophore have considerable second order nonlinear optical properties. Information obtained from depolarization studies of the scattered light is discussed.

  3. Absorptance Measurements of Optical Coatings - A Round Robin

    SciTech Connect

    Chow, R; Taylor, J R; Wu, Z L; Boccara, C A; Broulik, U; Commandre, M; DiJon, J; Fleig, C; Giesen, A; Fan, Z X; Kuo, P K; Lalezari, R; Moncur, K; Obramski, H-J; Reicher, D; Ristau, D; Roche, P; Steiger, B; Thomsen, M; von Gunten, M

    2000-10-26

    An international round robin study was conducted on the absorption measurement of laser-quality coatings. Sets of optically coated samples were made by a ''reactive DC magnetron'' sputtering and an ion beam sputtering deposition process. The sample set included a high reflector at 514 nm and a high reflector for the near infrared (1030 to 1318 nm), single layers of silicon dioxide, tantalum pentoxide, and hafnium dioxide. For calibration purposes, a sample metalized with hafnium and an uncoated, superpolished fused silica substrate were also included. The set was sent to laboratory groups for absorptance measurement of these coatings. Whenever possible, each group was to measure a common, central area and another area specifically assigned to the respective group. Specific test protocols were also suggested in regards to the laser exposure time, power density, and surface preparation.

  4. Two-photon absorption induced by electric field gradient of optical near-field and its application to photolithography

    SciTech Connect

    Yamaguchi, Maiku; Kawazoe, Tadashi; Yatsui, Takashi; Nobusada, Katsuyuki

    2015-05-11

    An electric field gradient is an inherent property of the optical near-field (ONF). We investigated its effect on electron excitation in a quantum dot via model calculations combining a density matrix formalism and a classical Lorentz model. The electric field gradient of the ONF was found to cause two-photon absorption by an unusual mechanism. Furthermore, the absorption exhibits a nonmonotonic dependence on the spatial arrangement of the nanosystem, completely different from that of conventional two-photon absorption induced by an intense electric field. The present two-photon absorption process was verified in a previous experimental observation by reinterpreting the results of ONF photolithography.

  5. Optical Path Switching Based Differential Absorption Radiometry for Substance Detection

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor)

    2000-01-01

    A system and method are provided for detecting one or more substances. An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. The first wavelength band and second wavelength band are unique. Further, spectral absorption of a substance of interest is different at the first wavelength band as compared to the second wavelength band. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

  6. In-vivo absorption properties of algal pigments

    NASA Astrophysics Data System (ADS)

    Bidigare, Robert R.; Ondrusek, Michael E.; Morrow, John H.; Kiefer, Dale A.

    1990-09-01

    Estimates of the in vivo specific absorption coefficients (m2 mg'; 400-750 nm, 2 nm intervals) for the major algal pigment groups (chlorophylls, carotenoids and phycobilins) are presented. "Unpackaged" absorption coefficients were initially obtained by measuring the absorption properties of pure pigment standards spectrophotometrically and "shifting" their absorption maxima to match in vivo positions. Two approaches for estimating the phytoplankton absorption coefficient (spectral reconstruction and spectral decomposition) are compared by linear regression analysis, incorporating concurrent measurements of particulate absorption and pigmentation performed in the Sargasso Sea. Results suggest that "pigment package" effects are minimal for natural assemblages of open-oceanic phytoplankton and that accessory pigments do not always co-vary with chlorophyll a over depth and time.

  7. Microstructure Related Properties of Optical Thin Films.

    NASA Astrophysics Data System (ADS)

    Wharton, John James, Jr.

    Both the optical and physical properties of thin film optical interference coatings depend upon the microstructure of the deposited films. This microstructure is strongly columnar with voids between the columns. Computer simulations of the film growth process indicate that the two most important factors responsible for this columnar growth are a limited mobility of the condensing molecules and self-shadowing by molecules already deposited. During the vacuum deposition of thin films, the microstructure can be influenced by many parameters, such as substrate temperature and vacuum pressure. By controlling these parameters and introducing additional ones, thin film coatings can be improved. In this research, ultraviolet irradiation and ion bombardment were examined as additional parameters. Past studies have shown that post-deposition ultraviolet irradiation can be used to relieve stress and reduce absorption in the far ultraviolet of silicon dioxide films. Ion bombardment has been used to reduce stress, improve packing density, and increase resistance to moisture penetration. Three refractory oxide materials commonly used in thin film coatings were studied; they are silicon dioxide, titanium dioxide, and zirconium dioxide. Both single-layer films and narrowband filters made of these materials were examined. A 1000-watt mercury-xenon lamp was used to provide ultraviolet irradiation. An inverted magnetron ion source was used to produce argon and oxygen ions. Ultraviolet irradiation was found to reduce the absorption and slightly increase the index of refraction in zirconium oxide films. X-ray diffraction analysis revealed that ultraviolet irradiation caused titanium oxide films to become more amorphous; their absorption in the ultraviolet was slightly reduced. No changes were noted in film durability. Ion bombardment enhanced the tetragonal (lll) peak of zirconium oxide but increased the absorption of both zirconium oxide and titanium oxide films. The titanium oxide

  8. Optical properties of sea ice in Liaodong Bay, China

    NASA Astrophysics Data System (ADS)

    Xu, Zhantang; Yang, Yuezhong; Wang, Guifen; Cao, Wenxi; Li, Zhijun; Sun, Zhaohua

    2012-03-01

    Many industrial, agricultural, and residential areas surrounding Liaodong Bay are responsible for much of the particulate matter (PM) and colored dissolved organic matter (CDOM) found in the sea ice in the bay. Understanding the optical properties of "dirty" sea ice is important for analyzing remote sensing data and calculating energy balances. We designed a hyperspectral radiation instrument to observe the optical properties of sea ice. The results show that albedo peaks ranged from 0.3 to 0.85 and that the peaks shifted to a longer wavelength for high PM and CDOM concentrations. The absorption and scattering coefficients for sea ice were obtained. The bulk absorption coefficient shows that bulk absorption is primarily determined by PM and CDOM at shorter wavelengths, while pure ice and brine pockets become more important at longer wavelengths. Scattering coefficients for sea ice ranged from 197 to 1072 m-1, and showed consistent variations with gas bubble and brine pocket concentrations. The effects of PM and CDOM on the bulk absorption coefficient of sea ice were studied. At 440 nm, particulates accounted for 55-98% and CDOM accounted for 2-37% of the bulk absorption. Ratios between particulate absorption and bulk absorption for sea ice were almost constant from 400 to 550 nm, and began to decrease sharply for wavelengths >550 nm. Ratios between CDOM and bulk absorption decreased almost linearly with increasing wavelength.

  9. Photoacoustic determination of optical absorption to extinction ratio in aerosols.

    PubMed

    Roessler, D M; Faxvog, F R

    1980-02-15

    The photoacoustic technique has been used in conjunction with an optical transmission measurement to determine the fraction of light absorbed in cigarette and acetylene smoke aerosols. At 0.5145-microm wavelength,the absorption-to-extinction fraction is 0.01 +/- 0.003 for cigarette smoke and is in excellent agreement with predictions from Mie theory for smoke particles having a refractive index of 1.45-0.00133i and a median diameter in the 0.15-0.65-microm range. For acetylene smoke the absorbed fraction was 0.85 +/- 0.05. PMID:20216896

  10. First-principles calculation of optical absorption spectra in conjugated polymers: Role of electron-hole interaction

    SciTech Connect

    Rohlfing, Michael; Tiago, M.L.; Louie, Steven G.

    2000-03-20

    Experimental and theoretical studies have shown that excitonic effects play an important role in the optical properties of conjugated polymers. The optical absorption spectrum of trans-polyacetylene, for example, can be understood as completely dominated by the formation of exciton bound states. We review a recently developed first-principles method for computing the excitonic effects and optical spectrum, with no adjustable parameters. This theory is used to study the absorption spectrum of two conjugated polymers: trans-polyacetylene and poly-phenylene-vinylene(PPV).

  11. Indium sulfide microflowers: Fabrication and optical properties

    SciTech Connect

    Zhu Hui; Wang Xiaolei; Yang Wen; Yang Fan; Yang Xiurong

    2009-10-15

    With the assistance of urea, uniform 2D nanoflakes assembled 3D In{sub 2}S{sub 3} microflowers were synthesized via a facile hydrothermal method at relative low temperature. The properties of the as-obtained In{sub 2}S{sub 3} flowers were characterized by various techniques. In this work, the utilization of urea and L-cysteine, as well as the amount of them played important roles in the formation of In{sub 2}S{sub 3} with different nanostructures. Inferred from their morphology evolution, a urea induced precursor-decomposition associated with the Ostwald-ripening mechanism was proposed to interpret these hierarchical structure formation. Furthermore, the optical properties of these In{sub 2}S{sub 3} microflowers were investigated via UV-vis absorption and photoluminescence (PL) spectroscopies in detail.

  12. All-optical reservoir computer based on saturation of absorption.

    PubMed

    Dejonckheere, Antoine; Duport, François; Smerieri, Anteo; Fang, Li; Oudar, Jean-Louis; Haelterman, Marc; Massar, Serge

    2014-05-01

    Reservoir computing is a new bio-inspired computation paradigm. It exploits a dynamical system driven by a time-dependent input to carry out computation. For efficient information processing, only a few parameters of the reservoir needs to be tuned, which makes it a promising framework for hardware implementation. Recently, electronic, opto-electronic and all-optical experimental reservoir computers were reported. In those implementations, the nonlinear response of the reservoir is provided by active devices such as optoelectronic modulators or optical amplifiers. By contrast, we propose here the first reservoir computer based on a fully passive nonlinearity, namely the saturable absorption of a semiconductor mirror. Our experimental setup constitutes an important step towards the development of ultrafast low-consumption analog computers. PMID:24921786

  13. Excellent microwave absorption property of Graphene-coated Fe nanocomposites

    PubMed Central

    Zhao, Xingchen; Zhang, Zhengming; Wang, Liaoyu; Xi, Kai; Cao, Qingqi; Wang, Dunhui; Yang, Yi; Du, Youwei

    2013-01-01

    Graphene has evoked extensive interests for its abundant physical properties and potential applications. It is reported that the interfacial electronic interaction between metal and graphene would give rise to charge transfer and change the electronic properties of graphene, leading to some novel electrical and magnetic properties in metal-graphene heterostructure. In addition, large specific surface area, low density and high chemical stability make graphene act as an ideal coating material. Taking full advantage of the aforementioned features of graphene, we synthesized graphene-coated Fe nanocomposites for the first time and investigated their microwave absorption properties. Due to the charge transfer at Fe-graphene interface in Fe/G, the nanocomposites show distinct dielectric properties, which result in excellent microwave absorption performance in a wide frequency range. This work provides a novel approach for exploring high-performance microwave absorption material as well as expands the application field of graphene-based materials. PMID:24305606

  14. Optical properties of a multibarrier structure under intense laser fields

    NASA Astrophysics Data System (ADS)

    Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

    2015-11-01

    Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

  15. Nonlinear optical and optical limiting properties of graphene oxide dispersion in femtosecond regime

    NASA Astrophysics Data System (ADS)

    Zheng, Zebo; Zhu, Liang; Zhao, Fuli

    2014-08-01

    The third-order nonlinear optical properties of graphene oxide (GO) dispersion in distilled water were investigated in femtosecond regime, using a single beam z-scan technique. Induced by a focused Gaussian beam (λ~800 nm) with 150 fs pulse duration, the graphene oxide shows strong nonlinear absorption, which was dominated by reverse saturable absorption (RSA), originates from two-photon absorption (TPA) in GO. In addition, the optical limiting performance of GO was experimentally derived, indicating that the occurrence of RSA make GO a candidate for optical limiting. In addition, the further increasing of input intensity would enhance the nonlinear scattering effects in the sample so that the optical limiting threshold was reached.

  16. Matrix formalism for light propagation and absorption in thick textured optical sheets.

    PubMed

    Eisenlohr, Johannes; Tucher, Nico; Höhn, Oliver; Hauser, Hubert; Peters, Marius; Kiefel, Peter; Goldschmidt, Jan Christoph; Bläsi, Benedikt

    2015-06-01

    In this paper, we introduce a simulation formalism for determining the Optical Properties of Textured Optical Sheets (OPTOS). Our matrix-based method allows for the computationally-efficient calculation of non-coherent light propagation and absorption in thick textured sheets, especially solar cells, featuring different textures on front and rear side that may operate in different optical regimes. Within the simulated system, the angular power distribution is represented by a vector. This light distribution is modified by interaction with the surfaces of the textured sheets, which are described by redistribution matrices. These matrices can be calculated for each individual surface texture with the most appropriate technique. Depending on the feature size of the texture, for example, either ray- or wave-optical methods can be used. The comparison of the simulated absorption in a sheet of silicon for a variety of surface textures, both with the results from other simulation techniques and experimentally measured data, shows very good agreement. To demonstrate the versatility of this newly-developed approach, the absorption in silicon sheets with a large-scale structure (V-grooves) at the front side and a small-scale structure (diffraction grating) at the rear side is calculated. Moreover, with minimal computational effort, a thickness parameter variation is performed. PMID:26072875

  17. Optical absorption signature of a self-assembled dye monolayer on graphene

    PubMed Central

    Sghaier, Tessnim; Le Liepvre, Sylvain; Fiorini, Céline; Douillard, Ludovic

    2016-01-01

    Summary A well-organized monolayer of alkylated perylene-3,4,9,10-tetracarboxylic-3,4,9,10-diimide (PTCDI) has been formed onto CVD graphene transferred on a transparent substrate. Its structure has been probed by scanning tunnelling microscopy and its optical properties by polarized transmission spectroscopy at varying incidence. The results show that the transition dipoles of adsorbed PTCDI are all oriented parallel to the substrate. The maximum absorption is consistent with the measured surface density of molecules and their absorption cross section. The spectrum presents mainly a large red-shift of the absorption line compared with the free molecules dispersed in solution, whereas the relative strengths of the vibronic structures are preserved. These changes are attributed to non-resonant interactions with the graphene layer and the neighbouring molecules. PMID:27547603

  18. Investigation of Third Order Optical Nonlinearity and Reverse Saturable Absorption of Octa-alkoxy Metallophthalocyanines

    NASA Technical Reports Server (NTRS)

    Sanghadasa, Mohan; Shin, In-Seek; Barr, Thomas A.; Clark, Ronald D.; Guo, Huai-Song; Martinez, Angela; Penn, Benjamin G.

    1998-01-01

    In recent years, there has been a growing interest in the development of passive optical power limiters for the protection of the human eye and solid-state sensors from damage caused by energetic light pulses and also for other switching applications. One of the key issues involved is the search for appropriate materials that show effective reverse saturable absorption. Phthalocyanines seem to be good candidates for such applications because of their higher third order nonlinearity and the unique electronic absorption characteristics. A series of 1,4,8,11,15, 18,22,25-octa-alkoxy metallophthalocyanines containing various central metal atoms such as zinc, copper, palladium, cobalt and nickel were characterized for their third order nonlinearity and for their nonlinear absorptive properties to evaluate their suitability to function as reverse saturable absorbers.

  19. Simultaneous measurement of thermal diffusivity and optical absorption coefficient using photothermal radiometry. II Multilayered solids

    NASA Astrophysics Data System (ADS)

    Salazar, Agustín; Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Celorrio, R.

    2011-08-01

    The aim of this work is to analyze the ability of modulated photothermal radiometry to retrieve the thermal diffusivity and the optical absorption coefficient of layered materials simultaneously. First, we extend the thermal quadrupole method to calculate the surface temperature of semitransparent multilayered materials. Then, this matrix method is used to evaluate the influence of heat losses by convection and radiation, the influence of the use of thin paint layers on the accuracy of thermal diffusivity measurements, and the effect of lateral heat diffusion due to the use of Gaussian laser beams. Finally, we apply the quadrupole method to retrieve (a) the thermal contact resistance in glass stacks and (b) the thermal diffusivity and optical absorption coefficient depth profiles in heterogeneous materials with continuously varying physical properties, as is the case of functionally graded materials and partially cured dental resins.

  20. In-vivo local determination of tissue optical properties

    NASA Astrophysics Data System (ADS)

    Bevilacqua, Frederic; Piguet, D.; Marquet, Pierre; Gross, Jeffrey D.; Tromberg, Bruce J.; Depeursinge, Christian D.

    1997-12-01

    Local and superficial optical characterization of biological tissues can be achieved by measuring the spatially resolved diffuse reflectance at small source-detector separations. The sensitivity of the signal to the phase function, absorption and scattering coefficients were studied using Monte Carlo simulations. Measurements of spatially resolved reflectance were performed in vivo on human brain with source-detector separations from 0.3 to 1.5 mm. Distinct optical properties were found between normal cortex, astrocytoma of optic nerve and normal optic nerve.

  1. In-vivo local determination of tissue optical properties

    NASA Astrophysics Data System (ADS)

    Bevilacqua, Frederic P.; Piguet, Dominique; Marquet, Pierre; Gross, Jeffrey D.; Tromberg, Bruce J.; Depeursinge, Christian D.

    1998-01-01

    Local and superficial optical characterization of biological tissues can be achieved by measuring the spatially resolved diffuse reflectance at small source-detector separations. The sensitivity of the signal to the phase function, absorption and scattering coefficients were studied using Monte Carlo simulations. Measurements of spatially resolved reflectance were performed in vivo on human brain with source-detector separations from 0.3 to 1.5 mm. Distinct optical properties were found between normal cortex, astrocytoma of optic nerve and normal optic nerve.

  2. Impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data

    NASA Astrophysics Data System (ADS)

    Li, Xiaoqi; Jiang, Huabei

    2013-02-01

    We present a study through extensive simulation that considers the impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data collected from media mimicking breast tissue. We found that while the impact of scattering heterogeneities/targets is modest on photoacoustic recovery of optical absorption coefficients, the impact of scattering contrast caused by adipose tissue, a layer of normal tissue along the boundary of the breast, is dramatic on reconstruction of optical absorption coefficients using photoacoustic data—up to 25.8% relative error in recovering the absorption coefficient is estimated in such cases. To overcome this problem, we propose a new method to enhance photoacoustic recovery of the optical absorption coefficient in heterogeneous media by considering inhomogeneous scattering coefficient distribution provided by diffuse optical tomography (DOT). Results from extensive simulations show that photoacoustic recovery of absorption coefficient maps can be improved considerably with a priori scattering information from DOT.

  3. Microwave absorption properties of pyrolytic carbon nanofilm

    PubMed Central

    2013-01-01

    We analyzed the electromagnetic (EM) shielding effectiveness in the Ka band (26 to 37 GHz) of highly amorphous nanometrically thin pyrolytic carbon (PyC) films with lateral dimensions of 7.2 × 3.4 mm2, which consists of randomly oriented and intertwined graphene flakes with a typical size of a few nanometers. We discovered that the manufactured PyC films, whose thickness is thousand times less than the skin depth of conventional metals, provide a reasonably high EM attenuation. The latter is caused by absorption losses that can be as high as 38% to 20% in the microwave frequency range. Being semi-transparent in visible and infrared spectral ranges and highly conductive at room temperature, PyC films emerge as a promising material for manufacturing ultrathin microwave (e.g., Ka band) filters and shields. PMID:23388194

  4. Metal incorporated M-DNA: structure, magnetism, optical absorption

    NASA Astrophysics Data System (ADS)

    Mizoguchi, Kenji

    2011-09-01

    DNA is an interesting material from the viewpoint of the materials science. This paper discusses the electronic states of the metal incorporated M-DNA complexes with several species of metal ions. M-DNA prepared by the ordinary methanol precipitation technique has been investigated with ESR, STM and optical absorption, and concluded that the metal ion hydrated with several water molecules locates in between the bases of a base pair and that the divalent metal ions are incorporated into DNA in place of two Na cations as the counter ion for PO-4in the DNA backbones. Only in Fe-DNA, it was confirmed that the Fe2+ in the FeCl2 aqueous solution reacts with DNA to form Fe-DNA complex with Fe3+, where the charge would transfer to DNA. Within 30 min, the hydrolysis of Fe2+ to form Fe3+O(OH) did not occur in the FeCl2 aqueous solution at room temperature. The optical absorption spectra of Fe-DNA is similar to that for FeCl3 with the ionic character, but definitely differs from that of Fe3+O(OH) with the covalent bonding nature, suggesting the ionic character of Fe3+ in Fe-DNA. Finally, the possible two kinds of electronic states for Zn-DNA with different bonding nature will be discussed in relation to the recent report on Zn-DNA.

  5. Management of light absorption in extraordinary optical transmission based ultra-thin-film tandem solar cells

    NASA Astrophysics Data System (ADS)

    Mashooq, Kishwar; Talukder, Muhammad Anisuzzaman

    2016-05-01

    Although ultra-thin-film solar cells can be attractive in reducing the cost, they suffer from low absorption as the thickness of the active layer is usually much smaller than the wavelength of incident light. Different nano-photonic techniques, including plasmonic structures, are being explored to increase the light absorption in ultra-thin-film solar cells. More than one layer of active materials with different energy bandgaps can be used in tandem to increase the light absorption as well. However, due to different amount of light absorption in different active layers, photo-generated currents in different active layers will not be the same. The current mismatch between the tandem layers makes them ineffective in increasing the efficiency. In this work, we investigate the light absorption properties of tandem solar cells with two ultra-thin active layers working as two subcells and a metal layer with periodically perforated holes in-between the two subcells. While the metal layer helps to overcome the current mismatch, the periodic holes increase the absorption of incident light by helping extraordinary optical transmission of the incident light from the top to the bottom subcell, and by coupling the incident light to plasmonic and photonic modes within ultra-thin active layers. We extensively study the effects of the geometry of holes in the intermediate metal layer on the light absorption properties of tandem solar cells with ultra-thin active layers. We also study how different metals in the intermediate layer affect the light absorption; how the geometry of holes in the intermediate layer affects the absorption when the active layer materials are changed; and how the intermediate metal layer affects the collection of photo-generated electron-hole pairs at the terminals. We find that in a solar cell with 6,6-phenyl C61-butyric acid methyl ester top subcell and copper indium gallium selenide bottom subcell, if the periodic holes in the metal layer are square or

  6. Nonlinear optical properties of bismuth selenide

    NASA Astrophysics Data System (ADS)

    Bas, Derek; Babakiray, Sercan; Stanescu, Tudor; Lederman, David; Bristow, Alan

    Bismuth selenide (Bi2Se3) is a topological insulator with many interesting photonic properties. Much research has been done involving various types of photocurrents in an attempt to highlight the differences between the bulk electronic states and massless conducting surface states. Here, Bi2Se3 films varying in thickness from 6 to 40 quintuple layers have been produced via molecular beam epitaxy as a means to vary the relative contributions of bulk and surface. On these samples, optical measurements were performed at around 1.6 eV, which is enough energy to stimulate transitions from the Fermi level to a region near the second Dirac cone. Z-scan was used to measure saturable absorption, time-resolved two-color pump-probe was used to measure two-photon absorption, and a Fourier transform infrared spectrometer was used to measure linear absorption. Results were examined and analyzed with respect to thickness. Thickness-dependent band structures were produced using a tight-binding model and used to compare with experimental results.

  7. Optical properties of thylakoid stacks

    NASA Astrophysics Data System (ADS)

    Shibayev, Pavel; Shibaev, Petr

    2012-02-01

    Optical properties of grana are simulated by means of 4x4 matrix approach (Berreman method). The results of calculations lead to a conclusion that even small degree of chirality, that may be present in a granum structure, results in the dramatic changes of its optical properties. Depending on the birefringence and degree of chirality in granum organization the reflection of left or right handed circularly polarized light can be greatly suppressed. This can explain the light induced difference in the growth of pea and lentil shoots irradiated by left and right handed circularly polarized light [1]. [4pt] [1] Pavel P. Shibayev, R.G. Pergolizzi, The effect of circularly polarized light on the growth of plants, International journal of botany, 7, 113 (2011)

  8. Cadmium sulfide and lead sulfide quantum dots in glass: Processing, growth, and optical absorption

    NASA Astrophysics Data System (ADS)

    Rao, Pratima Gattu Naga

    Glasses containing cadmium sulfide and lead sulfide particles were prepared, and their properties were studied. These particles exhibit quantum confinement behavior when they are smaller than their Bohr exciton radii. Quantum confinement leads to size dependence in the optical absorption of particles. This size dependence can tune the optical absorption of the material to a particular wavelength or energy and possibly enhances the nonlinear optical absorption of the particles. These properties have potential applications in photonic devices. To control the growth of these semiconductor particles in glass, the glass processing conditions were studied. CdS-doped glasses were initially prepared with CdO and ZnS. The sublimation temperature for ZnS is at 1185°C; whereas, CdO sublimes at 1559°C, and CdS at 980°C. Loss of both cadmium and sulfur was observed in open crucible melts, even when CdO and ZnS were used. Improvements in glass processing were made by use of preheat and a cover during the glass melting, resulting in better retention of both dopants. Direct CdS addition to the glasses was possible with these improvements, thus eliminating complications of zinc incorporation during the growth of the semiconductor particles. These methods were successfully applied to the synthesis of PbS-doped glasses. CdS and PbS particles were grown in alkali borosilicate glasses, and their optical absorption spectra were measured as a function of heat treatment temperature and time. The position of the absorption peak and edge shifted to longer wave-lengths, or lower energies, with longer heat treatments at a constant temperature. Both CdS and PbS particles exhibited quantum confinement. These measurements were used to calculate particle sizes from quantum confinement models. Comparisons with transmission electron microscopy (TEM) demonstrated that the 1-term effective-mass approximation was appropriate for estimating CdS particle sizes. A sophisticated four-band envelope

  9. All-Optical Wavelength Conversion by Picosecond Burst Absorption in Colloidal PbS Quantum Dots.

    PubMed

    Geiregat, Pieter; Houtepen, Arjan J; Van Thourhout, Dries; Hens, Zeger

    2016-01-26

    All-optical approaches to change the wavelength of a data signal are considered more energy- and cost-effective than current wavelength conversion schemes that rely on back and forth switching between the electrical and optical domains. However, the lack of cost-effective materials with sufficiently adequate optoelectronic properties hampers the development of this so-called all-optical wavelength conversion. Here, we show that the interplay between intraband and band gap absorption in colloidal quantum dots leads to a very strong and ultrafast modulation of the light absorption after photoexcitation in which slow components linked to exciton recombination are eliminated. This approach enables all-optical wavelength conversion at rates matching state-of-the-art convertors in speed, yet with cost-effective solution-processable materials. Moreover, the stronger light-matter interaction allows for implementation in small-footprint devices with low switching energies. Being a generic property, the demonstrated effect opens a pathway toward low-power integrated photonics based on colloidal quantum dots as the enabling material. PMID:26692112

  10. Optical Properties of Thin Film Molecular Mixtures

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.; Shumway, Dean A.

    2003-01-01

    Thin films composed of molecular mixtures of metal and dielectric are being considered for use as solar selective coatings for a variety of space power applications. By controlling the degree of molecular mixing, the solar selective coatings can be tailored to have the combined properties of high solar absorptance, , and low infrared emittance, . On orbit, these combined properties would simultaneously maximize the amount of solar energy captured by the coating and minimize the amount of thermal energy radiated. Mini-satellites equipped with solar collectors coated with these cermet coatings may utilize the captured heat energy to power a heat engine to generate electricity, or to power a thermal bus that directs heat to remote regions of the spacecraft. Early work in this area identified the theoretical boundary conditions needed to operate a Carnot cycle in space, including the need for a solar concentrator, a solar selective coating at the heat inlet of the engine, and a radiator.1 A solar concentrator that can concentrate sunlight by a factor of 100 is ideal. At lower values, the temperature of the solar absorbing surface becomes too low for efficient heat engine operation, and at higher values, cavity type heat receivers become attractive. In designing the solar selective coating, the wavelength region yielding high solar absorptance must be separated from the wavelength region yielding low infrared emittance by establishing a sharp transition in optical properties. In particular, a sharp transition in reflectance is desired in the infrared to achieve the desired optical performance. For a heat engine operating at 450 C, a sharp transition at 1.8 micrometers is desired.2 The radiator completes the heat flow through the Carnot cycle.

  11. Optical properties of fluids in microfabricated channels

    SciTech Connect

    French, T.; Gourley, P.L.; McDonald, A.E.

    1997-03-01

    Microfabricated channels are widely thought to be the key to realizing chemical analysis on a microscopic scale. Chemical and biological information in the microchannels is often probed with optical techniques such as fluorescence, Raman and absorption spectroscopy. However, the optical effects of a microchannel are not well characterized. For example, it is important to understand the optics of the channel in order to optimize optical coupling efficiency. The authors consider various designs for enhancing the sensitivity of fluorescence detection in a microchannel.

  12. OPTICAL AND DYNAMIC PROPERTIES OF UNDOPED AND DOPED SEMICONDUCTOR NANOSTRUCTURES

    SciTech Connect

    Grant, C D; Zhang, J Z

    2007-09-28

    This chapter provides an overview of some recent research activities on the study of optical and dynamic properties of semiconductor nanomaterials. The emphasis is on unique aspects of these properties in nanostructures as compared to bulk materials. Linear, including absorption and luminescence, and nonlinear optical as well as dynamic properties of semiconductor nanoparticles are discussed with focus on their dependence on particle size, shape, and surface characteristics. Both doped and undoped semiconductor nanomaterials are highlighted and contrasted to illustrate the use of doping to effectively alter and probe nanomaterial properties. Some emerging applications of optical nanomaterials are discussed towards the end of the chapter, including solar energy conversion, optical sensing of chemicals and biochemicals, solid state lighting, photocatalysis, and photoelectrochemistry.

  13. All-Optical Switching in Bacteriorhodopsin Based on Excited-State Absorption

    NASA Astrophysics Data System (ADS)

    Roy, Sukhdev

    2008-03-01

    Switching light with light is of tremendous importance for both fundamental and applied science. The advent of nano-bio-photonics has led to the design, synthesis and characterization of novel biomolecules that exhibit an efficient nonlinear optical response, which can be utilized for designing all-optical biomolecular switches. Bacteriorhodopsin (bR) protein found in the purple membrane of Halobacterium halobium has been the focus of intense research due to its unique properties that can also be tailored by physical, chemical and genetic engineering techniques to suit desired applications. The talk would focus on our recent results on all-optical switching in bR and its mutants, based on excited-state absorption, using the pump-probe technique. We would discuss the all-optical control of various features of the switching characteristics such as switching contrast, switching time, switching pump intensity, switched probe profile and phase, and relative phase-shift. Optimized conditions for all-optical switching that include optimized values of the small-signal absorption coefficient (for cw case), the pump pulse width and concentration for maximum switching contrast (for pulsed case), would be presented. We would discuss the desired optimal spectral and kinetic properties for device applications. We would also discuss the application of all-optical switching to design low power all-optical computing devices, such as, spatial light modulators, logic gates and multiplexers and compare their performance with other natural photoreceptors such as pharaonis phoborhodopsin, proteorhodopsin, photoactive yellow protein and the blue light plant photoreceptor phototropin.

  14. Optical properties of soot particles: measurement - model comparison

    NASA Astrophysics Data System (ADS)

    Forestieri, S.; Lambe, A. T.; Lack, D.; Massoli, P.; Cross, E. S.; Dubey, M.; Mazzoleni, C.; Olfert, J.; Freedman, A.; Davidovits, P.; Onasch, T. B.; Cappa, C. D.

    2013-12-01

    Soot, a product of incomplete combustion, plays an important role in the earth's climate system through the absorption and scattering of solar radiation. In order to accurately model the direct radiative impact of black carbon (BC), the refractive index and shape dependent scattering and absorption characteristics must be known. At present, the assumed shape remains highly uncertain because BC particles are fractal-like, being agglomerates of smaller (20-40 nm) spherules, yet traditional optical models such as Mie theory typically assume a spherical particle morphology. To investigate the ability of various optical models to reproduce observed BC optical properties, we measured light absorption and extinction coefficients of methane and ethylene flame soot particles. Optical properties were measured by multiple instruments: absorption by a dual cavity ringdown photoacoustic spectrometer (CRD-PAS), absorption and scattering by a 3-wavelength photoacoustic/nephelometer spectrometer (PASS-3) and extinction and scattering by a cavity attenuated phase shift spectrometer (CAPS). Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA) and mobility size was measured with a scanning mobility particle sizer (SMPS). Measurements were made for nascent soot particles and for collapsed soot particles following coating with dioctyl sebacate or sulfuric acid and thermal denuding to remove the coating. Wavelength-dependent refractive indices for the sampled particles were derived by fitting the observed absorption and extinction cross-sections to spherical particle Mie theory and Rayleigh-Debye-Gans theory. The Rayleigh-Debye-Gans approximation assumes that the absorption properties of soot are dictated by the individual spherules and neglects interaction between them. In general, Mie theory reproduces the observed absorption and extinction cross-sections for particles with volume equivalent diameters (VED) < ~160 nm, but systematically predicts lower

  15. Ultrafast recovery time and broadband saturable absorption properties of black phosphorus suspension

    SciTech Connect

    Wang, Yingwei; Huang, Guanghui; Chen, Jiazhang; Xiao, Si He, Jun; Mu, Haoran; Bao, Qiaoliang; Lin, Shenghuang

    2015-08-31

    As a new type of two-dimensional crystal material, black phosphorus (BP) exhibits excellent electronics and optical performance. Herein, we focus on carrier relaxation dynamics and nonlinear optical properties of BP suspension. Atomic force microscopy, transmission electron microscopy, and optical transmission spectrum are employed to characterize the structure and linear optical properties of the BP. Additionally, pump-probe experiments at wavelength of 1550 nm were carried out to study the carrier dynamics in BP suspension, and ultrafast recovery time was observed (τ{sub s} = 24 ± 2 fs). Furthermore, we demonstrate the saturable absorption signals by open aperture Z-scan experiments at wavelengths of 1550 nm, 532 nm, and 680 nm. The results indicate that BP has broadband saturable absorption properties and the nonlinear absorption coefficients were determined to be β{sub 2} = −0.20 ± 0.08 × 10{sup −3 }cm/GW (532 nm), β{sub 2} = −0.12 ± 0.05 × 10{sup −3 }cm/GW (680 nm), and β{sub 2} = −0.15 ± 0.09 × 10{sup −3 }cm/GW (1550 nm)

  16. Optical Absorption Cross Section of Individual Multi-Walled Carbon Nanotubes in the Visible Region.

    PubMed

    Shahzad, Muhammad Imran; Shahzad, Nadia; Tagliaferro, Alberto

    2016-01-01

    The aim of the present work is to determine the optical absorption cross section for visible radiation of various types of multiwall carbon nanotubes (MWCNTs) having different dimensions through macroscopic optical measurements. This is achieved by dispersing MWCNTs in polydimethylsiloxane (PDMS) and preparing composite films. Different percentages (0.0% to 1.5%) of each MWCNTs type were mixed into the PDMS matrix using high speed mechanical stirring (~1000 rpm) and ultrasonication (~37 kHz) to reach optimal dispersion. By using doctor blading technique, 100 µm thick uniform films were produced on glass. They were then thermally cured and detached from the glass to get flexible and self-standing films. Field-Emission Scanning Electron Microscope (FESEM) analysis of cryo-fractured composite samples was used to check the dispersion of MWCNTs in PDMS, while Raman spectroscopy and FTIR were employed to rule out possible structural changes of the polymer in the composite that would have altered its optical properties. Total and specular reflection and transmission spectra were measured for all films. The absorption coefficient, which represents the fractional absorption per unit length and is proportional to the concentration of absorbing sites (i.e., MWCNTs at photon energies upon which PDMS is non-absorbing), was extracted. For each MWCNTs type, the absorption cross section of an individual MWCNT was obtained from the slope of absorption coefficient versus MWCNTs number density curve. It was found to be related with MWCNT volume. This method can be applied to all other nanoparticles as far as they can be dispersed in a host transparent matrix. PMID:27398474

  17. Radiative properties of the background aerosol: absorption component of extinction.

    PubMed

    Clarke, A D; Charlson, R J

    1985-07-19

    The light-scattering and light-absorption coefficients of the global background aerosol define its single-scatter albedo. Continuous, simultaneous measurements of these optical coefficients were made on a daily basis for the remote marine mid-troposphere; such measurements are essential for assessment of the effects of aerosol on atmospheric radiative transfer. Measurements of light-absorption coefficients made at the Mauna Loa Observatory in Hawaii were higher than expected, and the single-scatter albedo was lower than the value often used in radiative transfer models. Soot appears to be the most likely primary absorber, and hemispheric dispersal of this combustion-derived material is suggested. PMID:17759145

  18. HAC: Band Gap, Photoluminescence, and Optical/Near-Infrared Absorption

    NASA Technical Reports Server (NTRS)

    Witt, Adolf N.; Ryutov, Dimitri; Furton, Douglas G.

    1996-01-01

    We report results of laboratory measurements which illustrate the wide range of physical properties found among hydrogenated amorphous carbon (HAC) solids. Within this range, HAC can match quantitatively the astronomical phenomena ascribed to carbonaceous coatings on interstellar grains. We find the optical band gap of HAC to be well correlated with other physical properties of HAC of astronomical interest, and conclude that interstellar HAC must be fairly hydrogen-rich with a band gap of E(sub g) is approx. greater than 2.0 eV.

  19. Optical Properties of Ferromagnetic Semiconductors

    NASA Astrophysics Data System (ADS)

    Burch, Kenneth

    2006-03-01

    Ferromagnetic semiconductors hold great promise for numerous magneto-optics applications. In this talk I detail recent optical spectroscopic studies of as grown and annealed thin films and digitally doped superlattices of Ga1-xMnxAs, prepared in the group of D.D. Awschalom (UCSB) and annealed in the group of N.Samarth (PSU). Annealing induces a large strengthening of the optical conductivity (σ1(φ)), while the frequency dependence of σ1(φ) remains unchanged. This indicates that the scattering rate and Fermi level have not been effected by annealing, despite the large increase in hole density. Our Infrared work on Digital Ferromagnetic Heterostructures reveals a unique ability to tune their optical properties as well as their intrinsic electronic structure without changing the doping/defect level. This work is in collaboration with D.B. Shrekenhamer, E.J. Singley, D.N. Basov (University of California, San Diego) J. Stephens, R.K. Kawakami, D.D. Awschalom(University of California, Santa Barbara), B.L. Sheu, and N. Samarth (Pennsylvania State University).

  20. Optical performance and metallic absorption in nanoplasmonic systems.

    PubMed

    Arnold, Matthew D; Blaber, Martin G

    2009-03-01

    Optical metrics relating to metallic absorption in representative plasmonic systems are surveyed, with a view to developing heuristics for optimizing performance over a range of applications. We use the real part of the permittivity as the independent variable; consider strengths of particle resonances, resolving power of planar lenses, and guiding lengths of planar waveguides; and compare nearly-free-electron metals including Al, Cu, Ag, Au, Li, Na, and K. Whilst the imaginary part of metal permittivity has a strong damping effect, field distribution is equally important and thus factors including geometry, real permittivity and frequency must be considered when selecting a metal. Al performs well at low permittivities (e.g. sphere resonances, superlenses) whereas Au & Ag only perform well at very negative permittivities (shell and rod resonances, LRSPP). The alkali metals perform well overall but present engineering challenges. PMID:19259225

  1. Optical properties of titanium dioxide nanotube arrays

    SciTech Connect

    Abdelmoula, Mohamed; Sokoloff, Jeffrey; Lu, Wen-Tao; Menon, Latika; Close, Thomas; Richter, Christiaan

    2014-01-07

    We present experimental measurements and a theoretical analysis of the near UV to NIR optical properties of free standing titania nanotube arrays. An improved understanding of the optical physics of this type of nanostructure is important to several next generation solar energy conversion technologies. We measured the transmission, reflection, and absorption of the electromagnetic spectrum from 300 nm to 1000 nm (UV to NIR) of titania nanotube arrays. We measured the total, specular, and diffuse reflection and transmission using both single point detection and an integrating sphere spectrometer. We find that the transmission, but not the reflection, of light (UV to NIR) through the nanotube array is well-explained by classic geometric optics using an effective medium model taking into account the conical geometry of the nanotubes. For wavelengths shorter than ∼500 nm, we find the surprising result that the reflection coefficient for light incident on the open side of the nanotube array is greater than the reflection coefficient for light incident on the closed “floor” of the nanotube array. We consider theoretical models based on the eikonal approximation, photonic crystal band theory, and a statistical treatment of scattering to explain the observed data. We attribute the fact that light with wavelengths shorter than 500 nm is more highly reflected from the open than the closed tube side as being due to disorder scattering inside the nanotube array.

  2. Absorption and emission properties of photonic crystals and metamaterials

    SciTech Connect

    Peng, Lili

    2007-08-03

    We study the emission and absorption properties of photonic crystals and metamaterials using Comsol Multiphysics and Ansoft HFSS as simulation tools. We calculate the emission properties of metallic designs using drude model and the results illustrate that an appropriate termination of the surface of the metallic structure can significantly increase the absorption and therefore the thermal emissivity. We investigate the spontaneous emission rate modifications that occur for emitters inside two-dimensional photonic crystals and find the isotropic and directional emissions with respect to different frequencies as we have expected.

  3. Optical re-injection in cavity-enhanced absorption spectroscopy

    PubMed Central

    Leen, J. Brian; O’Keefe, Anthony

    2014-01-01

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10−10 cm−1/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\sqrt {{\\rm Hz;}}$\\end{document} Hz ; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features. PMID:25273701

  4. Optical re-injection in cavity-enhanced absorption spectroscopy.

    PubMed

    Leen, J Brian; O'Keefe, Anthony

    2014-09-01

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10(-10) cm(-1)/√Hz; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features. PMID:25273701

  5. Optical re-injection in cavity-enhanced absorption spectroscopy

    SciTech Connect

    Leen, J. Brian O’Keefe, Anthony

    2014-09-15

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10{sup −10} cm{sup −1}/√(Hz;) an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features.

  6. Excitonic Effects and Optical Absorption Spectrum of Doped Graphene

    NASA Astrophysics Data System (ADS)

    Jornada, Felipe; Deslippe, Jack; Louie, Steven

    2012-02-01

    First-principles calculations based on the GW-Bethe-Salpeter Equation (GW-BSE) approach and subsequent experiments have shown large excitonic effects in the optical absorbance of graphene. Here we employ the GW-BSE formalism to probe the effects of charge carrier doping and of having an external electric field on the absorption spectrum of graphene. We show that the absorbance peak due to the resonant exciton exhibits systematic changes in both its position and profile when graphene is gate doped by carriers, in excellent agreement to very recent measurementsootnotetextTony F. Heinz, private communications.. We analyze the various contributions to these changes in the absorption spectrum, such as the effects of screening by carriers to the quasiparticle energies and electron-hole interactions. This work was supported by National Science Foundation Grant No. DMR10-1006184, the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, and the U.S. DOD - Office of Naval Research under RTC Grant No. N00014-09-1-1066. Computer time was provided by NERSC.

  7. Accurate simulation of optical properties in dyes.

    PubMed

    Jacquemin, Denis; Perpète, Eric A; Ciofini, Ilaria; Adamo, Carlo

    2009-02-17

    Since Antiquity, humans have produced and commercialized dyes. To this day, extraction of natural dyes often requires lengthy and costly procedures. In the 19th century, global markets and new industrial products drove a significant effort to synthesize artificial dyes, characterized by low production costs, huge quantities, and new optical properties (colors). Dyes that encompass classes of molecules absorbing in the UV-visible part of the electromagnetic spectrum now have a wider range of applications, including coloring (textiles, food, paintings), energy production (photovoltaic cells, OLEDs), or pharmaceuticals (diagnostics, drugs). Parallel to the growth in dye applications, researchers have increased their efforts to design and synthesize new dyes to customize absorption and emission properties. In particular, dyes containing one or more metallic centers allow for the construction of fairly sophisticated systems capable of selectively reacting to light of a given wavelength and behaving as molecular devices (photochemical molecular devices, PMDs).Theoretical tools able to predict and interpret the excited-state properties of organic and inorganic dyes allow for an efficient screening of photochemical centers. In this Account, we report recent developments defining a quantitative ab initio protocol (based on time-dependent density functional theory) for modeling dye spectral properties. In particular, we discuss the importance of several parameters, such as the methods used for electronic structure calculations, solvent effects, and statistical treatments. In addition, we illustrate the performance of such simulation tools through case studies. We also comment on current weak points of these methods and ways to improve them. PMID:19113946

  8. Optical Properties of Aerosols and Clouds: The Software Package OPAC.

    NASA Astrophysics Data System (ADS)

    Hess, M.; Koepke, P.; Schult, I.

    1998-05-01

    The software package OPAC (Optical Properties of Aerosols and Clouds) is described. It easily provides optical properties in the solar and terrestrial spectral range of atmospheric particulate matter. Microphysical and optical properties of six water clouds, three ice clouds, and 10 aerosol components, which are considered as typical cases, are stored as ASCII files. The optical properties are the extinction, scattering, and absorption coefficients, the single scattering albedo, the asymmetry parameter, and the phase function. They are calculated on the basis of the microphysical data (size distribution and spectral refractive index) under the assumption of spherical particles in case of aerosols and cloud droplets and assuming hexagonal columns in case of cirrus clouds. Data are given for up to 61 wavelengths between 0.25 and 40 m and up to eight values of the relative humidity. The software package also allows calculation of derived optical properties like mass extinction coefficients and Ångström coefficients.Real aerosol in the atmosphere always is a mixture of different components. Thus, in OPAC it is made possible to get optical properties of any mixtures of the basic components and to calculate optical depths on the base of exponential aerosol height profiles. Typical mixtures of aerosol components as well as typical height profiles are proposed as default values, but mixtures and profiles for the description of individual cases may also be achieved simply.

  9. Optical Properties of Metallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Vallée, F.

    The bright and changing colours obtained by dispersing metallic compounds in a glass matrix have been known empirically for centuries. Indeed, glasses have been coloured in the bulk by inclusion of metallic powders since ancient times to make jewellery and ornaments (see Chap. 25). Then in the Middle Ages, they were used for stained glass windows and later on for coloured glass artefacts, e.g., ruby red glass objects. However, the role played by nanoparticles in this colouring effect, i.e., the effects of nanoparticles on optical properties, were only first studied scientifically in the nineteenth century, by Michael Faraday [1].

  10. Photochromism induced nonlinear optical absorption enhancement and ultrafast responses of several dithienylethene compounds

    NASA Astrophysics Data System (ADS)

    Wang, Yaochuan; Yan, Yongli; Liu, Dajun; Wang, Guiqiu; Pu, Shouzhi

    2015-11-01

    The nonlinear optical properties and ultrafast dynamics of three dithienylethene photochromic derivatives (i.e., P1, P2, and P3) were investigated by two-photon fluorescence, open-aperture Z-scan, and femtosecond pump-probe experiments. Photoinduced ring-closure and ring-opening phenomena, as well as a photochromism induced nonlinear optical property enhancement, were observed. For both the ring-opening and ring-closure state, the curve exhibited an ultrafast absorption peak approximately 200 fs followed by a fast decay process (i.e., ˜1 ps) and a long decay process that had a duration longer than 5 ps. The ultrafast peak followed by a fast decay process and the long decay process were attributable to a special two-photon absorption process, the formation of a charge separation state, and the relaxation of the charge separation state, respectively. However, the magnitude of the signal under the ring-closure state is approximately fivefold greater than that of the ring-opening state, which is in good agreement with nonlinear optical results. Intramolecular charge transfer processes were observed in the dynamics curves of the P2' and P3' isomers with D- π-A and D- π-D structures.

  11. Optical and Electrical Properties of Ar+ Implanted PET

    NASA Astrophysics Data System (ADS)

    Kumar, Rajiv; Shekhawat, Nidhi; Sharma, Annu; Aggarwal, Sanjeev; Kumar, Praveen; Kanjilal, D.

    2011-07-01

    In the present work, the effect of 100 keV argon ion implantation on the optical and electrical properties of PET has been studied. A continuous reduction in optical band gap (from 3.63 to 1.93 eV) with increasing implantation dose has been observed as analyzed using UV-Visible absorption spectroscopy. Current-Voltage (I-V) characteristics have been studied which clearly indicate the enhancement in the conductivity of PET specimens as an effect of implantation. This increase in conductivity has been correlated with the decrease in optical band gap.

  12. Microwave absorption properties of Ni/(C, silicides) nanocapsules

    PubMed Central

    2012-01-01

    The microwave absorption properties of Ni/(C, silicides) nanocapsules prepared by an arc discharge method have been studied. The composition and the microstructure of the Ni/(C, silicides) nanocapsules were determined by means of X-ray diffraction, X-ray photoelectric spectroscopy, and transmission electron microscope observations. Silicides, in the forms of SiOx and SiC, mainly exist in the shells of the nanocapsules and result in a large amount of defects at the ‘core/shell’ interfaces as well as in the shells. The complex permittivity and microwave absorption properties of the Ni/(C, silicides) nanocapsules are improved by the doped silicides. Compared with those of Ni/C nanocapsules, the positions of maximum absorption peaks of the Ni/(C, silicides) nanocapsules exhibit large red shifts. An electric dipole model is proposed to explain this red shift phenomenon. PMID:22548846

  13. Optical Properties of Thin Film Molecular Mixtures

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.; Shumway, Dean A.; Lyons, Valerie (Technical Monitor)

    2002-01-01

    Thin films composed of molecular mixtures of metal and dielectric are being considered for use as solar selective coatings for a variety of space power applications. By controlling the degree of molecular mixing, the solar selective coatings can be tailored to have the combined properties of high solar absorptance, alpha, and low infrared emittance, epsilon. On orbit, these combined properties would simultaneously maximize the amount of solar energy captured by the coating and minimize the amount of thermal energy radiated. Mini-satellites equipped with solar collectors coated with these cermet coatings may utilize the captured heat energy to power a heat engine to generate electricity, or to power a thermal bus that directs heat to remote regions of the spacecraft. Early work in this area identified the theoretical boundary conditions needed to operate a Carnot cycle in space, including the need for a solar concentrator, a solar selective coating at the heat inlet of the engine, and a radiator. A solar concentrator that can concentrate sunlight by a factor of 100 is ideal. At lower values, the temperature of the solar absorbing surface becomes too low for efficient heat engine operation, and at higher values, cavity type heat receivers become attractive. In designing the solar selective coating, the wavelength region yielding high solar absorptance must be separated from the wavelength region yielding low infrared emittance by establishing a sharp transition in optical properties. In particular, a sharp transition in reflectance is desired in the infrared to achieve the desired optical performance. For a heat engine operating at 450C, a sharp transition at 1.8 micrometers is desired. The radiator completes the heat flow through the Carnot cycle. Additional work has been done supporting the use of molecular mixtures for terrestrial applications. Sputter deposition provides a means to apply coatings to the tubes that carry a working fluid at the focus of trough

  14. ESTIMATION OF INHERENT OPTICAL PROPERTIES AND THE WATER QUALITY COMPONENTS IN THE NEUSE RIVER-PAMLICO SOUND ESTUARINE SYSTEM

    EPA Science Inventory

    Field observations carried out in the Neuse River-Pamlico Sound Estuarine System (NRE-PS), North Carolina, USA were used to develop optical algorithms for assessing inherent optical properties, IOPs (absorption and backscattering) associated with water quality components (WQC).

  15. Characterization and measurement results of fluorescence in absorption optical filter glass

    NASA Astrophysics Data System (ADS)

    Reichel, S.; Biertümpfel, R.; Engel, A.

    2015-09-01

    Optical filter glasses (absorption filters) are for example used for spectroscopy. The filter glass absorbs the unwanted light and has a nearly angle independent spectral characteristic. The absorbed light can lead to (self-) fluorescence, i. e. the filter glass itself re-emits fluorescence light at a different wavelength - compared to the incident (excitation) light. This fluorescence light can disturb the measurement signal. In order to obtain an optimized optical design the fluorescence properties of the glasses must be known. By knowing fluorescence properties one can design a system with a good signal-to-noise ratio. We will present our measurement set-up for fluorescence measurements of optical filter glass. This set-up was used to obtain fluorescence measurement results for different optical filter glasses. For the first time we present results on the fluorescence level for different optical filter glasses. In addition the effect of excitation wavelength on the fluorescence level will be studied. Besides other factors, fluorescence depends on impurities of the raw material of the glass melt. Due to small fluctuations of the raw material used for the glass production the fluorescence of the same filter glass type can fluctuate from melt-to-melt. Thus, results from different melts will be shown for the same filter glass type.

  16. Optical properties of graphite oxide and reduced graphite oxide

    NASA Astrophysics Data System (ADS)

    Jung, Eilho; Lee, Seokbae; Roh, Seulki; Hwang, Eunhee; Lee, Junghyun; Lee, Hyoyoung; Hwang, Jungseek

    2014-07-01

    We studied the optical properties of a graphite oxide and a reduced graphite oxide by using the optical spectroscopic technique. The graphite oxide does not show a finite dc conductivity and has several characteristic absorption modes in the mid-infrared region, caused by an epoxide functional group and hydroxyl and carboxyl moieties in the mid-infrared range. The reduced graphite oxide shows a Drude-like response in the far-infrared region and the estimated dc conductivity and electric mobility are around 200 Ω-1cm-1 and ˜100 cm2V-1s-1, respectively. We found that the optical conductivity cannot be fitted with a simple Drude model, which indicates that the charge carriers are correlated. We applied an extended Drude model and obtained the optical scattering rate and the optical effective mass. We found that the optical effective mass can carry information of both the enhanced mass by correlation and the electronic band structure.

  17. Structure-property relation and third order nonlinear optical absorption study of a new organic crystal: 1-(3,4-Dimethoxyphenyl)-3-(2-fluorophenyl) prop-2-en-1-one

    NASA Astrophysics Data System (ADS)

    Chidan Kumar, C. S.; Raghavendra, S.; Chia, Tze Shyang; Chandraju, Siddegowda; Dharmaprakash, S. M.; Fun, Hoong-Kun; Quah, Ching Kheng

    2015-11-01

    A new third order centrosymmetric organic crystal: 1-(3,4-dimethoxyphenyl)-3-(2-fluorophenyl) prop-2-en-1-one (2FRDP) belonging to chalcone family has been synthesized and characterized by FTIR, CHNS and UV-Visible spectroscopy. Single crystal X-ray diffraction reveals that compound crystallizes in C2/c monoclinic space group. The X-ray powder diffraction of the crystal was carried out and hkl values are indexed for the diffraction pattern using mercury software. UV-Visible spectrum showed that 2FRDP is transparent in the entire visible region. The thermal stability of the grown 2FRDP crystal was analyzed by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The dielectric study revealed that, 2FRDP possesses low dielectric constant and dielectric loss at high frequency. The third order nonlinear optical absorption and the optical limiting experiment were carried out using open aperture Z-scan data using an Nd:YAG laser operating at the wavelength 532 nm.

  18. Second-order bosonic Kadanoff-Baym equations for plasmon-accompanied optical absorption

    NASA Astrophysics Data System (ADS)

    Schüler, Michael; Pavlyukh, Yaroslav

    2016-03-01

    The availability of ultra-short and strong light sources opens the door for a variety of new experiments such as transient absorption, where optical properties of systems can be studied in extreme nonequilibrium situations. The nonequilibrium Green's function formalism is an efficient approach to investigate these processes theoretically. Here we apply the method to the light-matter interaction of the magnesium 2p core level accompanied by electron-plasmon interaction due to collective excitations in the conduction band. The plasmons are described as massive bosonic quasi-particle excitations, leading to a second-order equations of motion, requiring a new approach for their propagation.

  19. Absorption and related optical dispersion effects on the spectral response of a surface plasmon resonance sensor

    SciTech Connect

    Nakkach, Mohamed; Lecaruyer, Pierre; Bardin, Fabrice; Sakly, Jaouhar; Lakhdar, Zohra Ben; Canva, Michael

    2008-11-20

    Surface plasmon resonance (SPR) sensing is an optical technique that allows real time detection of small changes in the physical properties, in particular in the refractive index, of a dielectric medium near a metal film surface. One way to increase the SPR signal shift is then to incorporate a substance possessing a strong dispersive refractive index in the range of the plasmon resonance band. In this paper, we investigate the impact of materials possessing a strong dispersive index integrated to the dielectric medium on the SPR reflectivity profile. We present theoretical results based on chromophore absorption spectra and on their associated refractive index obtained from the Lorentz approach and Kramers-Kroenig equations. As predicted by the theory, the experimental results show an enhancement of the SPR response, maximized when the chromophore absorption band coincides with the plasmon resonant wavelength. This shows that chromophores labeling can provide a potential way for SPR response enhancement.

  20. Long term measurements of optical properties and their hygroscopic enhancement

    NASA Astrophysics Data System (ADS)

    Hervo, M.; Sellegri, K.; Pichon, J. M.; Roger, J. C.; Laj, P.

    2014-11-01

    Optical properties of aerosols were measured from the GAW Puy de Dôme station (1465 m) over a seven year period (2006-2012). The impact of hygroscopicity on aerosol optical properties was calculated over a two year period (2010-2011). The analysis of the spatial and temporal variability of the optical properties showed that while no long term trend was found, a clear seasonal and diurnal variation was observed on the extensive parameters (scattering, absorption). Scattering and absorption coefficients were highest during the warm season and daytime, in concordance with the seasonality and diurnal variation of the PBL height reaching the site. Intensive parameters (single scattering albedo, asymmetry factor, refractive index) did not show such a strong diurnal variability, but still indicated different values depending on the season. Both extensive and intensive optical parameters were sensitive to the air mass origin. A strong impact of hygroscopicity on aerosol optical properties was calculated, mainly on aerosol scattering, with a dependence on the aerosol type. At 90% humidity, the scattering factor enhancement (fσsca) was more than 4.4 for oceanic aerosol that have mixed with a pollution plume. Consequently, the aerosol radiative forcing was estimated to be 2.8 times higher at RH = 90% and 1.75 times higher at ambient RH when hygroscopic growth of the aerosol was considered. The hygroscopicity enhancement factor of the scattering coefficient was parameterized as a function of humidity and air mass type.

  1. The optical properties of crystalline melilite

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Koike, C.; Tsuchiyama, A.

    We report the optical properties of the two end members of melilite group minerals in the infrared region by use of powdered synthesized single crystals for the first time. Melilite is known as one of a high temperature condensates, and a major constituent mineral in the CAIs (Ca and Al-rich inclusions) in the primitive carbonaceous chondrite. The chemical formula of the melilite is represented as (Ca,Na)2 [Mg,Fe2+,Al,Si)3O7]. Particularly in the CAIs, the melilite system is a solid solution of the Al-end member, gehlenite (Ca2Al2SiO7) and the Mg-end member,Å kermanite (Ca2MgSi2O7). The absorption spectral features of both end members are complex. The numbers of main absorption bands are 14 ˜15 in the region from 5 to 100 microns. In the 10 micron region, spectral features consist of several absorption bands as same as other silicate crystals. However, in particular forÅ kermanite, the feature consists of very sharp and strong bands which are not seen in other silicate crystals such as olivine and pyroxene. The most prominent absorption peaks located at 21 and 24 microns for gehlenite andÅ kermanite, respectively. In addition, both of two samples have very broad features in the Far-IR region. While from the recent ISO-SWS observations, it was reported that the detection of 22 micron emission feature in the Carina nebula Hii region (Chan & Onaka 2000) and in the Cas A supernova remnant (Arendt et al. 1999). From the comparison of laboratory data by Dorschner et al. (1980), Mg, Ca and Fe ``protosilicate" are considered as the possible carrier of this unidentified feature. In order to discuss the possibility of the identification of this feature by melilite, we tried to compare the observational data and the laboratory data multiplied by Plank distributions. From a preliminary analysis, we found that the laboratory absorption spectra of melilites are very similar to the unidentified 22 micron feature, though there are some minor discrepancies such as peak position

  2. Thermally induced nonlinear optical absorption in metamaterial perfect absorbers

    NASA Astrophysics Data System (ADS)

    Guddala, Sriram; Kumar, Raghwendra; Ramakrishna, S. Anantha

    2015-03-01

    A metamaterial perfect absorber consisting of a tri-layer (Al/ZnS/Al) metal-dielectric-metal system with top aluminium nano-disks was fabricated by laser-interference lithography and lift-off processing. The metamaterial absorber had peak resonant absorbance at 1090 nm and showed nonlinear absorption for 600ps laser pulses at 1064 nm wavelength. A nonlinear saturation of reflectance was measured to be dependent on the average laser power incident and not the peak laser intensity. The nonlinear behaviour is shown to arise from the heating due to the absorbed radiation and photo-thermal changes in the dielectric properties of aluminium. The metamaterial absorber is seen to be damage resistant at large laser intensities of 25 MW/cm2.

  3. Thermally induced nonlinear optical absorption in metamaterial perfect absorbers

    SciTech Connect

    Guddala, Sriram Kumar, Raghwendra; Ramakrishna, S. Anantha

    2015-03-16

    A metamaterial perfect absorber consisting of a tri-layer (Al/ZnS/Al) metal-dielectric-metal system with top aluminium nano-disks was fabricated by laser-interference lithography and lift-off processing. The metamaterial absorber had peak resonant absorbance at 1090 nm and showed nonlinear absorption for 600ps laser pulses at 1064 nm wavelength. A nonlinear saturation of reflectance was measured to be dependent on the average laser power incident and not the peak laser intensity. The nonlinear behaviour is shown to arise from the heating due to the absorbed radiation and photo-thermal changes in the dielectric properties of aluminium. The metamaterial absorber is seen to be damage resistant at large laser intensities of 25 MW/cm{sup 2}.

  4. Probing iron spin state by optical absorption in laser-heated diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Lobanov, S.; Goncharov, A. F.; Holtgrewe, N.; Lin, J. F.

    2015-12-01

    Pressure-induced spin-pairing transitions in iron-bearing minerals have been in the focus of geophysical studies1. Modern consensus is that iron spin state in the lower mantle is a complex function of crystal structure, composition, pressure, and temperature. Discontinuities in physical properties of lower mantle minerals have been revealed over the spin transition pressure range, but at room temperature. In this work, we have used a supercontinuum laser source and an intensified CCD camera to probe optical properties of siderite, FeCO3, and post-perovskite, Mg0.9Fe0.1SiO3, across the spin transition in laser-heated diamond anvil cell. Synchronously gating the CCD with the supercontinuum pulses (Fig. 1A) allowed diminishing thermal background to ~8.3*10-4. Utilizing the experimental setup we infer the spin state of ferrous iron in siderite at high pressure and temperature conditions (Fig. 1B). Similar behavior is observed for low spin ferric iron in post-perovskite at 130 GPa indicating that all iron in post-perovskite is high spin at lower mantle conditions. Also, our experimental setup holds promise for measuring radiative thermal conductivity of mantle minerals at relevant mantle conditions. Figure 1. (A) Timing of the optical absorption measurements at high temperature. (B) High temperature siderite absorption spectra at 45 GPa. Before heating and quenched after 1300 K spectra are shown in light and dark blue, respectively. Green and red curves are absorption spectra at 1200 K and 1300 K, respectively. Spectra shown in black represent room temperature absorption data on HS (43 GPa) and LS (45.5 GPa) siderite after Lobanov et al., 2015, shown for comparison.

  5. Parametric distortion of the optical absorption edge of a magnetic semiconductor by a strong laser field

    SciTech Connect

    Nunes, O.A.C.

    1985-09-15

    The influence of a strong laser field on the optical absorption edge of a direct-gap magnetic semiconductor is considered. It is shown that as the strong laser intensity increases the absorption coefficient is modified so as to give rise to an absorption tail below the free-field forbidden gap. An application is made for the case of the EuO.

  6. Optical Absorption and Electron Paramagnetic Resonance studies of two different solid solutions of Pyralspite Garnet

    NASA Astrophysics Data System (ADS)

    Watanabe, S.; Espinoza, S. R. Q.; Chubaci, J. F. D.; Cano, N. F.; Cornejo, D. R.

    2015-04-01

    Two different solid solutions of pyralspite garnet have been investigated as to their optical absorption and EPR properties. The absorption band around 9850 cm-1 is due to Fe2+. After heating above 950 °C we found this band diminishes considerably; which was interpreted as Fe2+ loosing an electron to become Fe3+. The EPR spectrum of sample consisted of a straight line with angular coefficient of about 176°. After 600°C/1hr annealing, the spectrum starts deviating from a straight line. A strong typical EPR signal is observed around g = 2.0 after annealing at 850°C. We assume that with high temperature annealing a large number of Fe2+ are converted to Fe3+ as the optical absorption has shown. These results were also confirmed by chemical reaction. The susceptibility vs. magnetic field measurement has shown that the samples annealed at temperatures below 850°C present normal paramagnetic behavior, however, annealed above 900 °C, they show hysteresis, namely ferromagnetic behavior.

  7. Shape-Dependent Nonlinear Optical Properties of Anisotropic Gold Nanoparticles.

    PubMed

    Hua, Yi; Chandra, Kavita; Dam, Duncan Hieu M; Wiederrecht, Gary P; Odom, Teri W

    2015-12-17

    This Letter reports the shape-dependent third-order nonlinear optical properties of anisotropic gold nanoparticles. We characterized the nonlinear absorption coefficients of nanorods, nanostars, and nanoshells using femtosecond Z-scan measurements. By comparing nanoparticle solutions with a similar linear extinction at the laser excitation wavelength, we separated shape effects from that of the localized surface plasmon wavelength. We found that the nonlinear response depended on particle shape. Using pump-probe spectroscopy, we measured the ultrafast transient response of nanoparticles, which supported the strong saturable absorption observed in nanorods and weak nonlinear response in nanoshells. We found that the magnitude of saturable absorption as well as the ultrafast spectral responses of nanoparticles were affected by the linear absorption of the nanoparticles. PMID:26595327

  8. Optical Properties of Multi-Layered Insulation

    NASA Technical Reports Server (NTRS)

    Rodriguez, Heather M.; Abercromby, Kira J.; Barker, Edwin

    2007-01-01

    , which is due to the copper color of Kapton. If the debris is MLI and the outer layer of copper coloring of Kapton is present, evidence would be seen spectrally by the specific absorption feature as well as using R-B (red-blue) light curves. Using laboratory photometric measurements and the results from spectral laboratory measurements, an optical property database is provided for an object with a high A/m. The benefits of this database for remote optical measurements of orbital debris are shown by illustrating the optical properties expected for a high A/m object, specifically common satellite and rocket body MLI.

  9. Physical and optical absorption studies of Fe3+ - ions doped lithium borate glasses containing certain alkaline earths

    NASA Astrophysics Data System (ADS)

    Bhogi, Ashok; Kumar, R. Vijaya; Kistaiah, P.

    2016-05-01

    Iron ion doped lithium borate glasses with the composition 15RO-25Li2O-59B2O3-1Fe2O3 (where R= Ca, Sr and Ba) have been prepared by the conventional melt quenching technique and characterized to investigate the physical and optical properties using XRD, density, molar volume and UV-Visible spectroscopy. The optical absorption spectra exhibit a band at around 460 nm which is assigned to 6A1g(S) → 4Eg (G) of Fe3+ ions with distorted octahedral symmetry. From ultraviolet absorption edges, the optical band gap and Urbach energies have been evaluated. The effect of alkaline earths on these properties is discussed.

  10. Optical properties of silicon inverse opals

    NASA Astrophysics Data System (ADS)

    Wei, Hong

    Silicon inverse opals are artificial structures in which nearly monodisperse, close-packed air bubbles are embedded in a silicon matrix. If properly tailored, this structure can exhibit a photonic band gap (PBG) in the near infrared spectral region. The PBG can block light propagation in any direction, allowing the control of light flow in the material. Silicon inverse opals can be fabricated by infiltrating amorphous silicon into silica colloidal crystals and then etching away the silica. In this thesis, the structural defects of silica colloidal crystals and the optical properties of silicon inverse opals are studied. First, by using laser-scanning confocal microscopy, the concentration and distribution of stacking faults and vacancies were quantified in silica colloidal crystals. It's shown that silica colloidal crystals show strong tendency toward face-center-cubic structure with the vacancy density as small as 5 x 10-4. Second, by combining optical microscopy and Fourier Transform Infrared (FTIR) spectroscopy, the transmission and reflection spectra of silicon inverse opals along the [111] direction were measured. Combined with the calculation of transmission and reflection spectra by Transfer Matrix Methods, it is concluded that the strong light attenuation in silicon inverse opals is due to the enhanced absorption (>600%) in silicon materials. Third, by using optical pump-probe techniques, the photo-induced ultra-fast reflection changes in silicon inverse opals were examined. The pump-generated free carriers cause the reflection in the band gap region to change after ˜0.5 ps. For the first few ps, the main effect is a decrease in reflectivity due to nonlinear absorption. After ˜5 ps, this effect disappears and an unexpected blue spectral shift is seen in the photonic band gap. The refractive index decreases due to optically-induced strain born the thermal expansion mismatch between silicon and its native oxide. Finally, by infiltrating silicon inverse

  11. Optical Properties of Acrylate-Based Negative-Type Photoresist and Its Application to Optical Waveguide Fabrication

    NASA Astrophysics Data System (ADS)

    Gustafik, Pavol; Sugihara, Okihiro; Okamoto, Naomichi

    2004-04-01

    In this article, we present some of the optical properties of a polymeric acrylate-based photoresist material called PNME, by its principal components, which are pentaerythritol triacrylate, n-methyldiethanolamine, and eosin. The refractive index and absorption spectra were measured. Because of the low absorption of PNME in the datacom and telecom regions, PNME was studied with respect to its suitability for the fabrication of a channel waveguide and/or an optical fiber. A multimode optical waveguide was fabricated using a cold UV stamping fabrication method, and propagation losses at 1.3 μm were measured. An optical fiber core was fabricated using a light-induced self-writing fabrication method. In our study, it was found that optical waveguides made from PNME have low propagation losses due to smooth sidewalls and the low absorption of PNME. An optical waveguide with a corrugated core was also fabricated.

  12. Nonlinear optical properties of composite materials

    NASA Technical Reports Server (NTRS)

    Haus, Joseph W.; Inguva, Ramarao

    1991-01-01

    The optical properties of a new class of composite nonlinear materials composed of coated grains, such as cadmium sulfide with a silver coating, are examined. These materials exhibit intrinsic optical bistability and resonantly enhanced conjugate reflectivity. The threshold for intrinsic optical bistability is low enough for practical applications in optical communications and optical computing. Some problems associated with the fabrication of these materials are addressed. Based on preliminary results, switching times are expected to be in the subpicosecond range.

  13. Electronic, optical and bonding properties of MgCO 3

    NASA Astrophysics Data System (ADS)

    Hossain, Faruque M.; Dlugogorski, B. Z.; Kennedy, E. M.; Belova, I. V.; Murch, Graeme E.

    2010-05-01

    The electronic, optical and bonding properties of MgCO 3 (magnesite, rhombohedral calcite-type structure) are calculated using a first-principles density-functional theory (DFT) method considering the exchange-correlation function within the local density approximation (LDA) and the generalized gradient approximation (GGA). The indirect band gap of magnesite is estimated to be 5.0 eV, which is underestimated by ˜1.0 eV. The fundamental absorption edge, which indicates the exact optical transitions from occupied valence bands to the unoccupied conduction band, is estimated by calculating the photon energy dependent imaginary part of the dielectric function using scissors approximations (rigid shift of unoccupied bands). The optical properties show consistent results with the experimental calcite-type structure and also show a considerable optical anisotropy of the magnesite structure. The density of states and Mulliken population analyses reveal the bonding nature between the atoms.

  14. Laboratory atomic transition data for precise optical quasar absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Murphy, Michael T.; Berengut, Julian C.

    2014-02-01

    Quasar spectra reveal a rich array of important astrophysical information about galaxies which intersect the quasar line of sight. They also enable tests of the variability of fundamental constants over cosmological time- and distance-scales. Key to these endeavours are the laboratory frequencies, isotopic and hyperfine structures of various metal-ion transitions. Here, we review and synthesize the existing information about these quantities for 43 transitions which are important for measuring possible changes in the fine-structure constant, α, using optical quasar spectra, i.e. those of Na, Mg, Al, Si, Ca, Cr, Mn, Fe, Ni and Zn. We also summarize the information currently missing that precludes more transitions being used. We present an up-to-date set of coefficients, q, which define the sensitivity of these transitions to variations in α. New calculations of isotopic structures and q-coefficients are performed for Si II and Ti II, including Si II λ1808 and Ti IIλλ1910.6/1910.9 for the first time. Finally, simulated absorption-line spectra are used to illustrate the systematic errors expected if the isotopic/hyperfine structures are omitted from profile fitting analyses. To ensure transparency, repeatability and currency of the data and calculations, we supply a comprehensive data base as Supporting Information. This will be updated as new measurements and calculations are performed.

  15. Enhanced Optical Absorption Induced by Dense Nanocavities Inside Titania Nanorods

    SciTech Connect

    Han,W.; Wu, L.; Klie, R.; Zhu, Y.

    2007-01-01

    Titania, a wide band gap semiconductor, can generate powerful oxidants and reductants by absorbing photon energies. Titania has been extensively used in photoelectrochemical systems, such as dye-sensitized titania, a wide band gap semiconductor, can generate powerful oxidants and reductants by absorbing photon energies. To improve the photoreactivity of titania, several approaches, including doping and metal loading have been proposed. Nanocavities are isolated entities inside a solid and hence are very different from nanoporous, whose pores (often amorphous and irregular) connect together and open to the surface. Dense polyhedral nanocavities inside single-crystalline anatase titania nanorods were successfully synthesized by simply heating titanate nanorods. The size of the nanocavities is typically about 10 nm. The surfaces of the nanocavity polyhedron are determined to be the crystallographic low-index planes of the titania crystal. We found that these dense nanocavities significantly enhance the optical absorption coefficient of titania in the near-ultraviolet region, thereby providing a new approach to increasing the photoreactivity of the titania nanorods in the applications related to absorbing photons.

  16. Retrieval of Aerosol Profiles using Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS)

    NASA Astrophysics Data System (ADS)

    Yilmaz, Selami; Frieß, Udo; Apituley, Arnoud; Henzing, Bas; Baars, Holger; Heese, Birgit; Althausen, Dietrich; Adam, Mariana; Putaud, Jean-Philippe; Zieger, Paul; Platt, Ulrich

    2010-05-01

    Multi Axis Differential Absorption Spectroscopy (MAX-DOAS) is a well established measurement technique to derive atmospheric trace gas profiles. Using MAX-DOAS measurements of trace gases with a known vertical profile, like the oxygen-dimer O4, it is possible to retrieve information on atmospheric aerosols. Based on the optimal estimation method, we have developed an algorithm which fits simultaneously measured O4 optical densities and relative intensities at several wavelengths and elevation angles to values simulated by a radiative transfer model. Retrieval parameters are aerosol extinction profile and optical properties such as single scattering albedo, phase function and Angström exponent. In 2008 and 2009 several intercomparison campaigns with established aerosol measurement techniques took place in Cabauw/Netherlands, Melpitz/Germany, Ispra/Italy and Leipzig/Germany, where simultaneous DOAS, lidar, Sun photometer and Nephelometer measurements were performed. Here we present results of the intercomparisons for cloud free conditions. The correlation of the aerosol optical thickness retrieved by the DOAS technique and the Sun photometer shows coefficients of determination from 0.96 to 0.98 and slopes from 0.94 to 1.07. The vertical structure of the DOAS retrieved aerosol extinction profiles compare favourably with the structures seen by the backscatter lidar. However, the vertical spatial development of the boundary layer is reproduced with a lower resolution by the DOAS technique. Strategies for the near real-time retrieval of trace gas profiles, aerosol profiles and optical properties will be discussed as well.

  17. Optical absorption in transparent PDMS materials applied for multimode waveguides fabrication

    NASA Astrophysics Data System (ADS)

    Cai, D. K.; Neyer, A.; Kuckuk, R.; Heise, H. M.

    2008-03-01

    The optical properties of transparent PDMS polymer materials, which can be integrated into general printed circuit board (PCB) for data communication, are of great interest due to the substantial market expectations for the near future. For the present paper, it was found that the absorption loss in polydimethylsiloxane (PDMS) is mainly caused by the vibrational overtone and combination bands of the CH 3-groups of the polymer in the spectral datacom region of 600-900 nm. Based on observed positions of fundamental, overtone and combination bands of the methyl-group, as recorded within the mid- and near-infrared spectra, anharmonicity constants and normal vibration frequencies were determined. Thus, an empirical equation for estimating the wavelengths with the most significant intrinsic absorption loss due to the corresponding band positions was formulated, which was found to agree well with the experimental data. In addition, PDMS multimode waveguides were fabricated and the respective optical insertion loss was measured at 850 nm, which is commercially used for optical datacom transmission and finally the thermal stability of PDMS multimode waveguides was verified as well.

  18. Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique Christine; Kulkarni, Varsha P.; York, Donald; Welty, Daniel; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli

    2015-08-01

    Gas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. Recent studies of QASs also find trends in both the gas and dust properties, such as correlations in metallicity with redshift and dust depletions. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of gas-phase element abundances based on archival high-resolution optical spectra. We also discuss our measurements of the strengths of the 10 and 18 micron silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between absorption redshift, gas metallicity, metal depletions, and silicate dust abundance, which will yield valuable insights into the star formation history. Support is provided by NASA through grant NNX14AG74G and by an award issued by JPL/Caltech, and from US-NSF grants AST-0908890 and AST-1108830 to the U. of S. Carolina.

  19. Advances in optical property measurements of spacecraft materials

    NASA Technical Reports Server (NTRS)

    Smith, Charles A.; Dever, Joyce A.; Jaworske, Donald A.

    1997-01-01

    Some of the instruments and experimental approaches, used for measuring the optical properties of thermal control systems, are presented. The instruments' use in studies concerning the effects of combined contaminants and space environment on these materials, and in the qualification of hardware for spacecraft, are described. Instruments for measuring the solar absorptance and infrared emittance offer improved speed, accuracy and data handling. A transient method for directly measuring material infrared emittance is described. It is shown that oxygen exposure before measuring the solar absorptance should be avoided.

  20. Plasmon enhanced broadband optical absorption in ultrathin silicon nanobowl array for photoactive devices applications

    NASA Astrophysics Data System (ADS)

    Sun, Rui-Nan; Peng, Kui-Qing; Hu, Bo; Hu, Ya; Zhang, Fu-Qiang; Lee, Shuit-Tong

    2015-07-01

    Both photonic and plasmonic nanostructures are key optical components of photoactive devices for light harvesting, enabling solar cells with significant thickness reduction, and light detectors capable of detecting photons with sub-band gap energies. In this work, we study the plasmon enhanced broadband light absorption and electrical properties of silicon nanobowl (SiNB) arrays. The SiNB-metal photonic-plasmonic nanostructure-based devices exhibited superior light-harvesting ability across a wide range of wavelengths up to the infrared regime well below the band edge of Si due to effective optical coupling between the SiNB array and incident sunlight, as well as electric field intensity enhancement around metal nanoparticles due to localized surface plasmon resonance. The photonic-plasmonic nanostructure is expected to result in infrared-light detectors and high-efficiency solar cells by extending light-harvesting to infrared frequencies.

  1. Plasmon enhanced broadband optical absorption in ultrathin silicon nanobowl array for photoactive devices applications

    SciTech Connect

    Sun, Rui-Nan; Peng, Kui-Qing Hu, Bo; Hu, Ya; Zhang, Fu-Qiang; Lee, Shuit-Tong

    2015-07-06

    Both photonic and plasmonic nanostructures are key optical components of photoactive devices for light harvesting, enabling solar cells with significant thickness reduction, and light detectors capable of detecting photons with sub-band gap energies. In this work, we study the plasmon enhanced broadband light absorption and electrical properties of silicon nanobowl (SiNB) arrays. The SiNB-metal photonic-plasmonic nanostructure-based devices exhibited superior light-harvesting ability across a wide range of wavelengths up to the infrared regime well below the band edge of Si due to effective optical coupling between the SiNB array and incident sunlight, as well as electric field intensity enhancement around metal nanoparticles due to localized surface plasmon resonance. The photonic-plasmonic nanostructure is expected to result in infrared-light detectors and high-efficiency solar cells by extending light-harvesting to infrared frequencies.

  2. The Optical Properties of Liquid Selenium-Tellurium Alloys

    NASA Astrophysics Data System (ADS)

    Silva, Larry Allen

    Techniques have been developed to prepare films of liquid semiconductors with sub-micrometer thicknesses. This makes it possible to determine the complex dielectric function at photon energies where interband transitions take place using information about both the transmissivity and reflectivity of the liquid, and provides a more direct probe of the electronic structure than an analysis of the reflectivity properties alone. Optical measurements have been performed on the liquid system Se_{rm x} Te_{rm 1-x} in composition steps of 20 atomic percent, and at temperatures from the melting point to 500^circ C. In this range of temperatures the optical absorption data for the liquids containing 0-80% Te show the presence of an optical band gap; these liquids are semiconductors. Possible forms for the density of electron states at the valence and conduction band edges have been derived using the non -direct transition model for optical absorption. Evidence for the onset of a transition from semiconducting to metal-like properties first appears in the Se _{20}Te_{80 } data at the highest measured temperatures. The data for liquid Te clearly show semimetallic properties: the reflectivity is large at far-infrared photon energies, decreasing at higher energies, and the absorption coefficient data extrapolate to a negative band gap energy. The complex dielectric function of liquid Te has been separated into interband and intraband components using the Drude model to determine the optical properties of the free charge carriers (holes). The energy dependence of the interband component of the data was found to be consistent with the preservation of 2-fold bonding across the semiconductor -semimetal transition. Data for the absorption coefficient at photon energies below the band gap of the Se-rich liquids have also been measured. The absorption edge of pure Se varies exponentially with photon energy. The behavior of the edge in the alloys is similar to that of Se, but a non

  3. Study of Aerosol Chemical Composition Based on Aerosol Optical Properties

    NASA Astrophysics Data System (ADS)

    Berry, Austin; Aryal, Rudra

    2015-03-01

    We investigated the variation of aerosol absorption optical properties obtained from the CIMEL Sun-Photometer measurements over three years (2012-2014) at three AERONET sites GSFC; MD Science_Center and Tudor Hill, Bermuda. These sites were chosen based on the availability of data and locations that can receive different types of aerosols from land and ocean. These absorption properties, mainly the aerosol absorption angstrom exponent, were analyzed to examine the corresponding aerosol chemical composition. We observed that the retrieved absorption angstrom exponents over the two sites, GSFC and MD Science Center, are near 1 (the theoretical value for black carbon) and with low single scattering albedo values during summer seasons indicating presence of black carbon. Strong variability of aerosol absorption properties were observed over Tudor Hill and will be analyzed based on the air mass embedded from ocean side and land side. We will also present the seasonal variability of these properties based on long-range air mass sources at these three sites. Brent Holben, NASA GSFC, AERONET, Jon Rodriguez.

  4. Optical absorption in ion-implanted lead lanthanum zirconate titanate ceramics

    SciTech Connect

    Seager, C.H.; Land, C.E.

    1984-08-15

    Optical absorption measurements have been performed on unmodified and on ion-implanted lead lanthanum zirconate titanate ceramics using the photothermal deflection spectroscopy technique. Bulk absorption coefficients depend on the average grain size of the material while the absorption associated with the ion-damaged layers does not. The damage-induced surface absorptance correlates well with the photosensitivity observed in implanted PLZT devices, supporting earlier models for the enhanced imaging efficiency of the materials.

  5. Optical properties of Tm 3+ ions in lithium borate glasses

    NASA Astrophysics Data System (ADS)

    Jayasankar, C. K.; Renuka ^Devi, A.

    1996-09-01

    Optical properties of Tm 3+ ions are investigated in the following lithium borate (LBO) glasses: Li 2CO 3 + H 3BO 3 and MCO 3 + Li 2CO 3 + H 3BO 3 (M = Mg, Ca, Sr and Ba). The assigned energy level data of Tm 3+ (4f 12) in these borate glasses as well as the data that are available for some other systems in the literature are analysed in terms of a parametrized Hamiltonian model that includes 14 free-ion parameters. The absorption linestrengths are measured for Tm 3+:LBO glasses. Using these data, intensity parameters (Ω λ, λ = 2, 4, 6), radiative transition probabilities, radiative lifetimes, fluorescence branching ratios and integrated absorption cross-sections for fluorescent levels of Tm 3+:LBO glasses are calculated by applying Judd-Ofelt theory. The effect of glass network formers and glass modifiers on the optical properties of Tm 3+:glasses are discussed.

  6. A study of optical absorption of cysteine-capped CdSe nanoclusters using first-principles calculations.

    PubMed

    Cui, Yingqi; Lou, Zhaoyang; Wang, Xinqin; Yu, Shengping; Yang, Mingli

    2015-04-14

    Understanding the size-dependent structures and properties of ligand-capped nanoclusters in solvent is of particular interest for the design, synthesis and application of II-VI colloidal QDs. Using DFT and TDDFT calculations, we studied the structure and optical property evolution of the cysteine-capped (CdSe)N clusters of N = 1-10, 13, 16 and 19 in gas, toluene, water and alkaline aqueous solution, and made a comparison with their corresponding bare clusters. The cysteine binds with (CdSe)Nvia several patterns depending on the medium they exist in, affecting the cluster structures and in consequence their optical absorption. In general, the absorption bands of (CdSe)N blueshift when cysteine is added, and the shift varies with the interaction strength between the cluster and the ligand, and the dielectric constant of the solvent. However, bare clusters retain their size sensitivity, in particular the redshift trend with increasing cluster size, and some similarity was noted for the optical absorption of the bare and ligated clusters regardless of the gas or solvent media. Population analysis reveals that the excitations are mainly from orbitals distributing on the (CdSe)N part, while the ligand is negligibly involved in the excitations. This is an important feature for the II-VI QDs as biosensors with which the information of biomolecules is detected from the size dependent optical absorption or emission of the QDs other than the biomolecules. PMID:25761258

  7. Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces.

    PubMed

    Goldschmidt, Benjamin S; Rudy, Anna M; Nowak, Charissa A; Tsay, Yowting; Whiteside, Paul J D; Hunt, Heather K

    2016-01-01

    Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. Optical property evaluation of thin films and the surfaces of bulk materials is an important step in understanding new optical material systems and their applications. The method presented can estimate thickness, refractive index, and use absorptive properties of materials for detection. This metrology system uses evanescent field-based photoacoustics (EFPA), a field of research based upon the interaction of an evanescent field with the photoacoustic effect. This interaction and its resulting family of techniques allow the technique to probe optical properties within a few hundred nanometers of the sample surface. This optical near field allows for the highly accurate estimation of material properties on the same scale as the field itself such as refractive index and film thickness. With the use of EFPA and its sub techniques such as total internal reflection photoacoustic spectroscopy (TIRPAS) and optical tunneling photoacoustic spectroscopy (OTPAS), it is possible to evaluate a material at the nanoscale in a consolidated instrument without the need for many instruments and experiments that may be cost prohibitive. PMID:27500652

  8. Optimum Compromise Between Optical Absorption and Electrical Property of the Planar Multi-Heterojunction Organic Solar Cells Based with New Thiazol Derivative, the (2-THIOXO-3-N-(2-METHOXYPHENYL) THIAZOLIDIN-4-ONE), as Electron Donor

    NASA Astrophysics Data System (ADS)

    Toumi, A. Lakhdar; Khelil, A.; Bernède, J. C.; Mouchaal, Y.; Djafri, A.; Toubal, K.; Hellal, N.; Cattin, L.

    2015-03-01

    The synthesis of a new thiazol derivative, the (2-thioxo-3-N-(2-methoxyphenyl) thiazolidin-4-one) (called TH-2) is described. After characterization of the TH-2, the cyclic voltammetry study coupled with optical absorbance measurements show that its LUMO and HOMO are -3.5 and -5.5 respectively. Then the TH-2 is used as electron donor (ED) in organic solar cells (OSCs). The anode buffer layer being CuI the devices are based on the planar heterojunction TH-2/fullerene. Homogeneous amorphous films of TH-2 are obtained when it is deposited onto CuI. For an optimum TH-2 thickness of 20 nm, a power conversion efficiency of 0.42% is obtained. Then, in order to broaden the absorption range of the OSCs, it is coupled with the tetraphenyl-dibenzoperiflanthene, whose band structure matches the band structure of TH-2. Such new multilayer structure allows achieving a power conversion efficiency of 0.49%.

  9. Surface structure and the optical properties of black chrome

    NASA Astrophysics Data System (ADS)

    Smith, G. B.; McPhedran, R. C.; Derrick, G. H.

    1985-04-01

    A new optical model is presented for solar-selective black chrome. Surface texture is shown to be the primary factor which gives thin films of black chrome a uniformly high absorptance in the visible and near-infrared regions. Internal composition of the films is a secondary influence on their optical properties. We present results consistent with experimental data obtained from films having widely varying structures and compositions, both before and after heat treatment. Our optical model does not rely on the quasistatic approximation, hitherto universally employed in theoretical studies of solar-selective black chrome. Instead, we use a rigorous diffraction formulation for doubly-periodic surfaces (bigratings). The key parameters of the surface morphology are determined from stereo-pair electronmicrographs, and are used in the bigrating model. We present the predicted variation of spectral absorptance with wavelength, as well as integrated absorptance and thermal emittance, for roughened chromium. We give results both for bare metal, and for the metal conformally overcoated either with a thin layer of Cr2O3 or with a Cr/Cr2O3 cermet. Various shapes of surface features are examined, and surface profile is shown not to be crucial in determining optical properties.

  10. Optical Properties of Photovoltaic Organic-Inorganic Lead Halide Perovskites.

    PubMed

    Green, Martin A; Jiang, Yajie; Soufiani, Arman Mahboubi; Ho-Baillie, Anita

    2015-12-01

    Over the last several years, organic-inorganic lead halide perovskites have rapidly emerged as a new photovoltaic contender. Although energy conversion efficiency above 20% has now been certified, improved understanding of the material properties contributing to these high performance levels may allow the progression to even higher efficiency, stable cells. The optical properties of these new materials are important not only to device design but also because of the insight they provide into less directly accessible properties, including energy-band structures, binding energies, and likely impact of excitons, as well as into absorption and inverse radiative recombination processes. PMID:26560862

  11. Identifying Aerosol Type/Mixture from Aerosol Absorption Properties Using AERONET

    NASA Technical Reports Server (NTRS)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Dickerson, R. R.; Thompson, A. M.; Slutsker, I.; Li, Z.; Tripathi, S. N.; Singh, R. P.; Zibordi, G.

    2010-01-01

    Aerosols are generated in the atmosphere through anthropogenic and natural mechanisms. These sources have signatures in the aerosol optical and microphysical properties that can be used to identify the aerosol type/mixture. Spectral aerosol absorption information (absorption Angstrom exponent; AAE) used in conjunction with the particle size parameterization (extinction Angstrom exponent; EAE) can only identify the dominant absorbing aerosol type in the sample volume (e.g., black carbon vs. iron oxides in dust). This AAE/EAE relationship can be expanded to also identify non-absorbing aerosol types/mixtures by applying an absorption weighting. This new relationship provides improved aerosol type distinction when the magnitude of absorption is not equal (e.g, black carbon vs. sulfates). The Aerosol Robotic Network (AERONET) data provide spectral aerosol optical depth and single scattering albedo - key parameters used to determine EAE and AAE. The proposed aerosol type/mixture relationship is demonstrated using the long-term data archive acquired at AERONET sites within various source regions. The preliminary analysis has found that dust, sulfate, organic carbon, and black carbon aerosol types/mixtures can be determined from this AAE/EAE relationship when applying the absorption weighting for each available wavelength (Le., 440, 675, 870nm). Large, non-spherical dust particles absorb in the shorter wavelengths and the application of 440nm wavelength absorption weighting produced the best particle type definition. Sulfate particles scatter light efficiently and organic carbon particles are small near the source and aggregate over time to form larger less absorbing particles. Both sulfates and organic carbon showed generally better definition using the 870nm wavelength absorption weighting. Black carbon generation results from varying combustion rates from a number of sources including industrial processes and biomass burning. Cases with primarily black carbon showed

  12. Atmospheric aerosols: Their Optical Properties and Effects

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Measured properties of atmospheric aerosol particles are presented. These include aerosol size frequency distribution and complex retractive index. The optical properties of aerosols are computed based on the presuppositions of thermodynamic equilibrium and of Mie-theory.

  13. Optical properties of liquids for fluidic optics.

    PubMed

    Liebetraut, Peter; Waibel, Philipp; Nguyen, Phuong Ha Cu; Reith, Patrick; Aatz, Bernd; Zappe, Hans

    2013-05-10

    We present the dispersion characteristics of 18 liquids and one resin, which are widely used as media for liquid lenses in adaptive and tunable optics and for index matching in spectrochemical analysis. These are measured by using a refractometer operating at six different wavelengths. We provide a short description of the measurement setup and present a detailed uncertainty analysis of the measurement system to provide a measure of the reliability of the data. We conclude with a catalog of refractive indices and Sellmeier coefficients of the measured liquids and show the location of the analyzed materials in an Abbe diagram. PMID:23669831

  14. Nocturnal Measurements of HONO by Differential Optical Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wojtal, P.; McLaren, R.

    2011-12-01

    Differential optical absorption spectroscopy (DOAS) was used to quantify the concentration of HONO, NO2 and SO2 in the nocturnal urban atmosphere at York University over a period of one year. These measurements form a comprehensive HONO data set, including a large range of temperatures, relative humidity, surface conditions (snow, water, dry, etc.) and NO2 concentrations. Laboratory studies and observations within the nocturnal boundary layer reported in the literature suggest heterogeneous conversion of NO2 on surface adsorbed water as the major nighttime source of HONO. HONO formation and photolysis is believed to represent a major source term in the hydroxyl radical budget in polluted continental regions. Currently, most air quality models tend to significantly underpredict HONO, caused by the lack of understanding of HONO formation processes and the parameters that affect its concentration. Recently, we reported nocturnal pseudo steady states (PSS) of HONO in an aqueous marine environment and a conceptual model for HONO formation on aqueous surfaces was proposed. The data set collected at York University is being analyzed with a view towards further understanding the nighttime HONO formation mechanism and testing several hypotheses: 1) A HONO PSS can exist during certain times at night in an urban area in which the HONO concentration is independent of NO2, given the surface contains sufficient water coverage and is saturated with nitrogen containing precursors; 2) The concentration of HONO is positively correlated with temperature during periods where a PSS exists; 3) Different conversion efficiencies of NO2 to HONO exist on dry, wet and snow surfaces; 4) HONO formation has a NO2 order dependence between 0 and 2nd order, dependant on NO2 concentration, relative humidity, etc. The data set will be presented along with statistical analysis that sheds new light on the source of HONO in urban areas at night.

  15. Optical properties of normal and diseased breast tissues: prognosis for optical mammography

    NASA Astrophysics Data System (ADS)

    Troy, Tamara L.; Page, David L.; Sevick-Muraca, Eva M.

    1996-07-01

    The use of near-infrared measurements of photon migration has been recently demonstrated for the detection of breast cancer in Europe. Yet the clinical success of this potential screening tool depends upon consistent detection of the disease at earlier stages than is currently possible with conventional x-ray mammography. In this paper, we present the optical property measurements of 115 histologically classified breast tissue specimens in order to determine whether consistent and significant optical contrast exists for detection of the disease. Our in vitro optical properties measured with a double integrating sphere technique show consistent changes in effective scattering coefficients, (mu) s', with tissue classification of infiltrating carcinoma, ductal carcinoma in situ, mucinous carcinoma, normal fatty, and normal fibrous tissues. However, there is little change in the in vitro tissue absorption coefficient, (mu) a, measured at 749, 789, and 836 nm. For normal and diseased tissue specimens extracted from the same patient, we found differences in optical properties, indicating optical contrast. Using a finite- element prediction of light propagation, we evaluated this optical contrast for photon migration detection of ductal carcinoma in situ tissues using these optical properties measured in vitro.

  16. MEASUREMENT OF THE OPTICAL PROPERTIES OF APPLES BY HYPERSPECTRAL IMAGING FOR ASSESSING FRUIT QUALITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Absorption and reduced scattering coefficients are two fundamental optical properties for turbid materials. The objective of this research was to use a newly developed hyperspectral imaging technique for determining the absorption and reduced scattering coefficients of apples and to relate them to f...

  17. Luminescent properties of bismuth centres in aluminosilicate optical fibres

    SciTech Connect

    Bulatov, Lenar I; Mashinskii, Valerii M; Dvoirin, Vladislav V; Dianov, Evgenii M; Kustov, Evgenii F

    2010-02-28

    The shape and spectral position of the luminescence bands of bismuth-doped aluminosilicate glass fibres are shown to depend on excitation power and wavelength. This indicates that the red and IR luminescence bands are composed of several components. The absorption and radiative transitions involved are identified, and a diagram of energy levels and transitions is obtained for four modifications of a bismuth centre in different environments in the aluminosilicate glass network. The effect of local environment on the optical properties of the bismuth centres is examined. (optical fibres and waveguides)

  18. Double quantum dot in a quantum dash: Optical properties

    SciTech Connect

    Kaczmarkiewicz, Piotr Machnikowski, Paweł; Kuhn, Tilmann

    2013-11-14

    We study the optical properties of highly elongated, highly flattened quantum dot structures, also referred to as quantum dashes, characterized by the presence of two trapping centers located along the structure. Such a system can exhibit some of the properties characteristic for double quantum dots. We show that sub- and super-radiant states can form for certain quantum dash geometries, which is manifested by a pronounced transfer of intensity between spectral lines, accompanied by the appearance of strong electron-hole correlations. We also compare exciton absorption spectra and polarization properties of a system with a single and double trapping center and show how the geometry of multiple trapping centers influences the optical properties of the system. We show that for a broad range of trapping geometries the relative absorption intensity of the ground state is larger than that of the lowest excited states, contrary to the quantum dash systems characterized by a single trapping center. Thus, optical properties of these structures are determined by fine details of their morphology.

  19. Infrared Optical Properties of Diamond

    NASA Astrophysics Data System (ADS)

    Smith, David; Karstens, William

    2001-03-01

    We have developed a Taylor-series representation for the refractive index of intrinsic elemental semiconductors in a transparent region starting from the Kramers-Kronig relations. Cauchy proposed a similar expansion on the basis of aether theory, but the present formulation requires just causality and linear response. Only terms in even powers of energy occur; their coefficients are the inverse odd moments of the interband extinction coefficient. Inclusion of low-energy extrinsic absorptions yields a Laurent series; coefficients of the negative-power terms are the odd moments of the extrinsic absorption. We demonstrate this formulation for natural diamond over the energy range 0.05 - 5 eV. An index vs. photon-energy-squared plot is very nearly linear, corresponding to the first terms in a Taylor-series for interband absorption. However, the index dips sharply below 0.5 eV. Experience(D.Y. Smith, Mitio Inokuti, and W. Karstens, Physics Essays) (in press) with similar deviations in Si and Ge indicates this corresponds to Laurent-series terms for free-electron intraband or defect absorption. The coefficient of the ω-2 term is related to the f-sum rule and gives the plasma frequency for the extrinsic absorption. We find that, unlike nominally pure silicon where free-carriers account for the low-energy absorption, absorption by defects or impurities are the most likely extrinsic culprits in diamond.

  20. Optical absorption components of light-modulated absorption spectrum of CdS

    NASA Technical Reports Server (NTRS)

    Conway, E. J.; Long, E. R.

    1975-01-01

    The amplitude and decay coefficient of light-induced modulation of absorption (LIMA) was measured as a function of wavelength from 535 to 850 nm for single-crystal CdS. The decay coefficient exhibited a discontinuous resonance at 710 nm which was due to the overlap and cancellation of two opposing absorption changes. A method was developed to separate these opposing absorption changes using the measured decay coefficients. The discrete-level-to-band energy for one absorption change was found to be 1.64 eV. An improved model was developed which contains two associated levels in the band gap separated by 0.32 eV.

  1. Absorption and scattering properties of carbon nanohorn-based nanofluids for direct sunlight absorbers

    PubMed Central

    2011-01-01

    In the present work, we investigated the scattering and spectrally resolved absorption properties of nanofluids consisting in aqueous and glycol suspensions of single-wall carbon nanohorns. The characteristics of these nanofluids were evaluated in view of their use as sunlight absorber fluids in a solar device. The observed nanoparticle-induced differences in optical properties appeared promising, leading to a considerably higher sunlight absorption with respect to the pure base fluids. Scattered light was found to be not more than about 5% with respect to the total attenuation of light. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device. PACS 78.40.Ri, 78.35.+c, 78.67.Bf, 88.40.fh, 88.40.fr, 81.05.U. PMID:21711795

  2. Optical Properties of Snow and Sea-ice, Barrow Alaska

    NASA Astrophysics Data System (ADS)

    Reay, H. J.; France, J. L.; King, M. D.

    2009-12-01

    Sunlit snowpacks and sea-ice produce a flux of chemicals from the snow or ice to the atmosphere. The chemical flux (1) changes the oxidising capacity of the atmosphere above the snowpack (2) alters chemical concentrations in snow, via reaction with photo-generated hydroxyl radicals. Photochemistry in snow and ice affect concentration chemicals in ice cores which are used to infer past (and therefore future) climates. Impurities in snow changes the optical absorption properties of the snowpack and thus the efficiency with which they melt as highlighted by the IPCC. Measurements of the solar irradiance in the snow and above the snow were undertaken as part of the OASIS 2009 campaign Barrow, Alaska. A model has been used to compute the amount of chemistry driven by this sunlight in and above the snow and to calculate fluxes of NO, NO2 from the snow and depth integrated hydroxyl radical production rate. The values can be compared to measurements of these gases at Barrow as part of the large OASIS field campaign. We have studied the optical properties of different Arctic snowpacks at UV-visible wavelength (350-700nm) by measuring the e-folding depth and albedos of many windpacks. Optically the snowpacks can be classified into four main snowpack types: snow on sea-ice, snow inland, soft and hard windpack. The albedo was measured using nadir reflectance and the e-folding depth was measured by recording the diffuse irradiance using fibre optic probes inserted into the snow at known depths. Using the TUV-Snow radiative transfer model we have determined the optical variables for scattering and absorption. We have produce absorption spectra of the impurities in the snowpack demonstrating a combination of black carbon and humic-like material (fig1). Fig 1. Absorption spectrum of inland snow

  3. The retrieval of optical properties from terrestrial dust devil vortices

    NASA Astrophysics Data System (ADS)

    Mason, Jonathon P.; Patel, Manish R.; Lewis, Stephen R.

    2014-03-01

    The retrieval of the optical properties of desert aerosols in suspension within terrestrial dust devils is presented with possible future application for martian dust devils. The transmission of light through dust devil vortices was measured in situ to obtain the wavelength-dependent attenuation by the aerosols. A Monte Carlo model was applied to each dust devil with the retrieved optical properties corresponding to the set of parameters which lead to the best model representation of the observed transmission spectra. The retrieved optical properties agree well with single scattering theory and are consistent with previous studies of dust aerosols. The enhanced absorption observed for dust devils with a higher tangential wind speed, and in comparison to atmospheric aerosol studies, suggests that larger dust particles are lofted and suspended around dust devil vortices. This analysis has shown that the imaginary refractive indices (and thus the optical properties of the suspended dust) are generally overestimated when these larger dust grains entrained by dust devils are neglected. This will lead to an overestimation of the amount of solar radiation absorbed by the small particles that remain in suspension after the dust devil terminates. It is also demonstrated that a 10% uncertainty in the particle size distribution of the dust entrained in the dust devils can result in a 50% increase in the predicted amount of incident solar radiation absorbed by the dust particles once the dust devil has terminated. The method used here provides the capability to retrieve the optical properties of the dust entrained in martian dust devils by taking advantage of transits over surface spacecraft which are capable of making optical measurements at ultraviolet and visible wavelengths. Our results suggest that we would observed higher absorption at all wavelengths for dust particles entrained in dust devil vortices compared to the ubiquitous dust haze.

  4. Calibration of scattering and absorption properties of a liquid diffusive medium at NIR wavelengths. CW method.

    PubMed

    Martelli, Fabrizio; Zaccanti, Giovanni

    2007-01-22

    In spite of many progresses achieved both with theories and with experiments in studying light propagation through diffusive media, a reliable method for accurate measurements of the optical properties of diffusive media at NIR wavelengths is, in our opinion, still missing. It is therefore difficult to create a diffusive medium with well known optical properties to be used as a reference. In this paper we describe a method to calibrate the reduced scattering coefficient, mu'(s) , of a liquid diffusive medium and the absorption coefficient, mu(a), of an absorbing medium with a standard error smaller than 2% both on mu'(s) and on mu(a). The method is based on multidistance measurements of fluence into an infinite medium illuminated by a CW source. The optical properties are retrieved with simple inversion procedures (linear fits) exploiting the knowledge of the absorption coefficient of the liquid into which the diffuser and the absorber are dispersed. In this study Intralipid diluted in water has been used as diffusive medium and Indian ink as absorber. For a full characterization of these media measurements of collimated transmittance have also been carried out, from which the asymmetry factor of the scattering function of Intralipid and the single scattering albedo of Indian ink have been determined. PMID:19532267

  5. Characterization of ion-assisted induced absorption in A-Si thin-films used for multivariate optical computing

    NASA Astrophysics Data System (ADS)

    Nayak, Aditya B.; Price, James M.; Dai, Bin; Perkins, David; Chen, Ding Ding; Jones, Christopher M.

    2015-06-01

    Multivariate optical computing (MOC), an optical sensing technique for analog calculation, allows direct and robust measurement of chemical and physical properties of complex fluid samples in high-pressure/high-temperature (HP/HT) downhole environments. The core of this MOC technology is the integrated computational element (ICE), an optical element with a wavelength-dependent transmission spectrum designed to allow the detector to respond sensitively and specifically to the analytes of interest. A key differentiator of this technology is it uses all of the information present in the broadband optical spectrum to determine the proportion of the analyte present in a complex fluid mixture. The detection methodology is photometric in nature; therefore, this technology does not require a spectrometer to measure and record a spectrum or a computer to perform calculations on the recorded optical spectrum. The integrated computational element is a thin-film optical element with a specific optical response function designed for each analyte. The optical response function is achieved by fabricating alternating layers of high-index (a-Si) and low-index (SiO2) thin films onto a transparent substrate (BK7 glass) using traditional thin-film manufacturing processes (e.g., ion-assisted e-beam vacuum deposition). A proprietary software and process are used to control the thickness and material properties, including the optical constants of the materials during deposition to achieve the desired optical response function. The ion-assisted deposition is useful for controlling the densification of the film, stoichiometry, and material optical constants as well as to achieve high deposition growth rates and moisture-stable films. However, the ion-source can induce undesirable absorption in the film; and subsequently, modify the optical constants of the material during the ramp-up and stabilization period of the e-gun and ion-source, respectively. This paper characterizes the unwanted

  6. Tunable van Hove Singularities and Optical Absorption of Twisted Bilayer Graphene

    NASA Astrophysics Data System (ADS)

    Liang, Yufeng; Yang, Li

    2013-03-01

    We perform the first-principles GW-Bethe-Salpeter Equation (BSE) simulation to study the optical absorption spectra of isolated twisted bilayer graphene (TBLG). The twisting generates new van Hove singularities (VHS), and these VHSs and corresponding optical absorption peaks can be tuned in a wide range by the twist angle. Enhanced electron-electron and electron-hole interactions are shown to be important to understand both optical absorption peak positions and their lineshapes. With these many-electron effects included, our calculation satisfactorily explains recent experimental measurements.

  7. Modified optical absorption of molecules on metallic nanoparticles at sub-monolayer coverage

    NASA Astrophysics Data System (ADS)

    Darby, Brendan L.; Auguié, Baptiste; Meyer, Matthias; Pantoja, Andres E.; Le Ru, Eric C.

    2016-01-01

    Enhanced optical absorption of molecules in the vicinity of metallic nanostructures is key to a number of surface-enhanced spectroscopies and of great general interest to the fields of plasmonics and nano-optics. However, experimental access to this absorbance has long proven elusive. Here, we present direct measurements of the surface absorbance of dye molecules adsorbed onto silver nanospheres and, crucially, at sub-monolayer concentrations where dye-dye interactions become negligible. With a large detuning from the plasmon resonance, distinct shifts and broadening of the molecular resonances reveal the intrinsic properties of the dye in contact with the metal colloid, in contrast to the often studied strong-coupling regime where the optical properties of the dye molecules cannot be isolated. The observation of these shifts together with the ability to routinely measure them has broad implications in the interpretation of experiments involving resonant molecules on metallic surfaces, such as surface-enhanced spectroscopies and many aspects of molecular plasmonics.

  8. Annealing effects on optical properties of natural alexandrite

    NASA Astrophysics Data System (ADS)

    Fernandes Scalvi, Rosa M.; Li, Máximo Siu; Scalvi, Luis V. A.

    2003-11-01

    Natural alexandrite (BeAl2O4:Cr3+) crystals are investigated as regards the effects of annealing on their optical properties. Optical absorption spectra are measured from the ultraviolet (190 nm) to the near infrared (900 nm), for a sample subjected to consecutive annealing processes, where time and temperature are varied. Besides this, luminescence spectra are simultaneously obtained for this sample, excited with a Kr+ laser source, tuned on an ultraviolet multi-line mode (337.5, 350.7 and 356.4 nm). We observe from absorption as well as from emission data that annealing mainly influences the distribution of Cr3+ and Fe3+ ions, located on sites of a mirror plane (Cs symmetry), which are responsible for the optical properties of alexandrite. The results obtained lead to the conclusion that annealing induces a modification of the population of Cr3+ on Cs sites as well as on sites located on an inversion plane (Ci). Annealing could improve the optical properties of this material, as regards its application as a tunable laser.

  9. Mechanical properties and energy absorption characteristics of a polyurethane foam

    SciTech Connect

    Goods, S.H.; Neuschwanger, C.L.; Henderson, C.; Skala, D.M.

    1997-03-01

    Tension, compression and impact properties of a polyurethane encapsulant foam have been measured as a function of foam density. Significant differences in the behavior of the foam were observed depending on the mode of testing. Over the range of densities examined, both the modulus and the elastic collapse stress of the foam exhibited power-law dependencies with respect to density. The power-law relationship for the modulus was the same for both tension and compression testing and is explained in terms of the elastic compliance of the cellular structure of the foam using a simple geometric model. Euler buckling is used to rationalize the density dependence of the collapse stress. Neither tension nor compression testing yielded realistic measurements of energy absorption (toughness). In the former case, the energy absorption characteristics of the foam were severely limited due to the inherent lack of tensile ductility. In the latter case, the absence of a failure mechanism led to arbitrary measures of energy absorption that were not indicative of true material properties. Only impact testing revealed an intrinsic limitation in the toughness characteristics of the material with respect to foam density. The results suggest that dynamic testing should be used when assessing the shock mitigating qualities of a foam.

  10. Characterization of Spectral Absorption Properties of Aerosols Using Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, O.; Jethva, H.; Bhartia, P. K.; Ahn, C.

    2012-01-01

    The wavelength-dependence of aerosol absorption optical depth (AAOD) is generally represented in terms of the Angstrom Absorption Exponent (AAE), a parameter that describes the dependence of AAOD with wavelength. The AAE parameter is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses high spectral resolution measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measured reflectance (rho lambda) is approximately given by Beer's law rho lambda = rho (sub 0 lambda) e (exp -mtau (sub abs lambda)) where rho(sub 0 lambda) is the cloud reflectance, m is the geometric slant path and tau (sub abs lambda) is the spectral AAOD. The rho (sub 0 lambda) term is determined by means of radiative transfer calculations using as input the cloud optical depth derived as described in Torres et al. [JAS, 2012] that accounts for the effects of aerosol absorption. In the second step, corrections for molecular and aerosol scattering effects are applied to the cloud reflectance term, and the spectral AAOD is then derived by inverting the equation above. The proposed technique will be discussed in detail and application results will be presented. The technique can be easily applied to hyper-spectral satellite measurements that include UV such as OMI, GOME and SCIAMACHY, or to multi-spectral visible measurements by other sensors provided that the aerosol-above-cloud events are easily identified.

  11. Retrieval of Aerosol Absorption Properties from Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, Omar; Bhartia, Pawan K.; Jethva, H.; Ahn, Chang-Woo

    2012-01-01

    The Angstrom Absorption Exponent (AAE) is a parameter commonly used to characterize the wavelength-dependence of aerosol absorption optical depth (AAOD). It is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses multi-spectral measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measurement can be explained, using an approximations of Beer's Law (BL), as the upwelling reflectance at the cloud top attenuated by the absorption effects of the overlying aerosol layer. The upwelling reflectance at the cloud-top in an aerosol-free atmospheric column is mainly a function of cloud optical depth (COD). In the proposed method of AAE derivation, the first step is determining COD which is retrieved using a previously developed color-ratio based approach. In the second step, corrections for molecular scattering effects are applied to both the observed ad the calculated cloud reflectance terms, and the spectral AAOD is then derived by an inversion of the BL approximation. The proposed technique will be discussed in detail and application results making use of OMI multi-spectral measurements in the UV-Vis. will be presented.

  12. Optical properties of porphyrin: graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Harsha Vardhan Reddy, M.; Al-Shammari, Rusul M.; Al-Attar, Nebras; Lopez, Sergio; Keyes, Tia E.; Rice, James H.

    2014-08-01

    In this work we aim to (via a non-invasive functionalization approach) tune and alter the intrinsic features of optically "transparent" graphene, by integrating water-soluble porphyrin aggregates. We explore the potential to combine porphyrin aggregates and graphene oxide to assess the advantages of such as a composite compared to the individual systems. We apply a range of optical spectroscopy methods including photo-absorption, fluorescence assess ground-state and excited state interactions. Our studies show that comparing resonant Raman scattering with optical transmission and fluorescence microscopy that the presence of influences the microscopic structures of the resulting composites.

  13. Measuring the Optical Absorption Cross-sections of Au-Ag Nanocages and Au Nanorods by Photoacoustic Imaging

    PubMed Central

    Cho, Eun Chul; Kim, Chulhong; Zhou, Fei; Cobley, Claire M.; Song, Kwang Hyun; Chen, Jingyi; Li, Zhi-Yuhan; Wang, Lihong V.; Xia, Younan

    2009-01-01

    This paper presents a method for measuring the optical absorption cross-sections (σa) of Au-Ag nanocages and Au nanorods. The method is based on photoacoustic (PA) imaging, where the detected signal is directly proportional to the absorption coefficient (μa) of the nanostructure. For each type of nanostructure, we firstly obtained μa from the PA signal by benchmarking against a linear calibration curve (PA signal vs. μa) derived from a set of methylene blue solutions with different concentrations. We then calculated σa by dividing the μa by the corresponding concentration of the Au nanostructure. Additonally, we obtained the extinction cross-section (σe, sum of absorption and scattering) from the extinction spectrum recorded using a conventional UV-vis-NIR spectrometer. From the measurements of σa and σe, we were able to easily derive both the absorption and scattering cross-sections for each type of gold nanostructure. The ratios of absorption to extinction obtained from experimental and theoretical approaches agreed well, demonstrating the potential use of this method in determining the optical absorption and scattering properties of gold nanostructures and other types of nanomaterials. PMID:19680423

  14. Optical properties of epitaxial YAG:Yb films

    NASA Astrophysics Data System (ADS)

    Ubizskii, S. B.; Matkovskii, A. O.; Melnyk, S. S.; Syvorotka, I. M.; Müller, V.; Peters, V.; Petermann, K.; Beyertt, A.; Giesen, A.

    2004-03-01

    This work deals with the investigation of the optical properties of epitaxial YAG:Yb films and their suitability as gain media for thin disk lasers. Epitaxial films of YAG:Yb were grown by the liquid phase epitaxy method in air on the (111)-oriented YAG substrates. The thickness of the grown layers was from 30 to 260 m. The melt composition was varied to obtain the desired doping level from 10 to 15% and to optimize the optical properties. The best epitaxial films were colourless and had an Yb3+ luminescence lifetime of more than 950 s, which is very close to the intrinsic lifetime of the Yb ions in the bulk YAG single crystals. These films were tested in a thin disk laser setup with 24 absorption passes of the 940 nm pumping beam. The maximum output power at 1.03 m wavelength in CW operation reached more than 60 W and the optical efficiency was close to 30%.

  15. Broadband optical absorption by tunable Mie resonances in silicon nanocone arrays

    PubMed Central

    Wang, Z. Y.; Zhang, R. J.; Wang, S. Y.; Lu, M.; Chen, X.; Zheng, Y. X.; Chen, L. Y.; Ye, Z.; Wang, C. Z.; Ho, K. M.

    2015-01-01

    Nanostructure arrays such as nanowire, nanopillar, and nanocone arrays have been proposed to be promising antireflection structures for photovoltaic applications due to their great light trapping ability. In this paper, the optical properties of Si nanopillar and nanocone arrays in visible and infrared region were studied by both theoretical calculations and experiments. The results show that the Mie resonance can be continuously tuned across a wide range of wavelength by varying the diameter of the nanopillars. However, Si nanopillar array with uniform diameter exhibits only discrete resonance mode, thus can't achieve a high broadband absorption. On the other hand, the Mie resonance wavelength in a Si nanocone array can vary continuously as the diameters of the cross sections increase from the apex to the base. Therefore Si nanocone arrays can strongly interact with the incident light in the broadband spectrum and the absorbance by Si nanocone arrays is higher than 95% over the wavelength from 300 to 2000 nm. In addition to the Mie resonance, the broadband optical absorption of Si nanocone arrays is also affected by Wood-Rayleigh anomaly effect and metal impurities introduced in the fabrication process. PMID:25589290

  16. In situ measurements of the optical absorption of dioxythiophene-based conjugated polymers

    NASA Astrophysics Data System (ADS)

    Hwang, J.; Schwendeman, I.; Ihas, B. C.; Clark, R. J.; Cornick, M.; Nikolou, M.; Argun, A.; Reynolds, J. R.; Tanner, D. B.

    2011-05-01

    Conjugated polymers can be reversibly doped by electrochemical means. This doping introduces new subband-gap optical absorption bands in the polymer while decreasing the band-gap absorption. To study this behavior, we have prepared an electrochemical cell allowing in situ measurements of the optical properties of the polymer. The cell consists of a thin polymer film deposited on gold-coated Mylar behind which is another polymer that serves as a counterelectrode. An infrared transparent window protects the upper polymer from ambient air. By adding a gel electrolyte and making electrical connections to the polymer-on-gold films, one may study electrochromism in a wide spectral range. As the cell voltage (the potential difference between the two electrodes) changes, the doping level of the conjugated polymer films is changed reversibly. Our experiments address electrochromism in poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-dimethylpropylenedioxythiophene) (PProDOT-Me2). This closed electrochemical cell allows the study of the doping induced subband-gap features (polaronic and bipolaronic modes) in these easily oxidized and highly redox switchable polymers. We also study the changes in cell spectra as a function of polymer thickness and investigate strategies to obtain cleaner spectra, minimizing the contributions of water and gel electrolyte features.

  17. Laser induced deflection (LID) method for absolute absorption measurements of optical materials and thin films

    NASA Astrophysics Data System (ADS)

    Mühlig, Christian; Bublitz, Simon; Paa, Wolfgang

    2011-05-01

    We use optimized concepts to measure directly low absorption in optical materials and thin films at various laser wavelengths by the laser induced deflection (LID) technique. An independent absolute calibration, using electrical heaters, is applied to obtain absolute absorption data without the actual knowledge of the photo-thermal material properties. Verification of the absolute calibration is obtained by measuring different silicon samples at 633 nm where all laser light, apart from the measured reflection/scattering, is absorbed. Various experimental results for bulk materials and thin films are presented including measurements of fused silica and CaF2 at 193 nm, nonlinear crystals (LBO) for frequency conversion and AR coated fused silica for high power material processing at 1030 nm and Yb-doped silica raw materials for high power fiber lasers at 1550 nm. In particular for LBO the need of an independent calibration is demonstrated since thermal lens generation is dominated by stress-induced refractive index change which is in contrast to most of the common optical materials. The measured results are proven by numerical simulations and their influence on the measurement strategy and the obtained accuracy are shown.

  18. Broadband optical absorption by tunable Mie resonances in silicon nanocone arrays

    DOE PAGESBeta

    Wang, Z. Y.; Zhang, R. J.; Wang, S. Y.; Lu, M.; Chen, X.; Zheng, Y. X.; Chen, L. Y.; Ye, Z.; Wang, C. Z.; Ho, K. M.

    2015-01-15

    Nanostructure arrays such as nanowire, nanopillar, and nanocone arrays have been proposed to be promising antireflection structures for photovoltaic applications due to their great light trapping ability. In this paper, the optical properties of Si nanopillar and nanocone arrays in visible and infrared region were studied by both theoretical calculations and experiments. The results show that the Mie resonance can be continuously tuned across a wide range of wavelength by varying the diameter of the nanopillars. However, Si nanopillar array with uniform diameter exhibits only discrete resonance mode, thus can't achieve a high broadband absorption. On the other hand, themore » Mie resonance wavelength in a Si nanocone array can vary continuously as the diameters of the cross sections increase from the apex to the base. Therefore Si nanocone arrays can strongly interact with the incident light in the broadband spectrum and the absorbance by Si nanocone arrays is higher than 95% over the wavelength from 300 to 2000 nm. In addition to the Mie resonance, the broadband optical absorption of Si nanocone arrays is also affected by Wood-Rayleigh anomaly effect and metal impurities introduced in the fabrication process.« less

  19. Broadband optical absorption by tunable Mie resonances in silicon nanocone arrays

    SciTech Connect

    Wang, Z. Y.; Zhang, R. J.; Wang, S. Y.; Lu, M.; Chen, X.; Zheng, Y. X.; Chen, L. Y.; Ye, Z.; Wang, C. Z.; Ho, K. M.

    2015-01-15

    Nanostructure arrays such as nanowire, nanopillar, and nanocone arrays have been proposed to be promising antireflection structures for photovoltaic applications due to their great light trapping ability. In this paper, the optical properties of Si nanopillar and nanocone arrays in visible and infrared region were studied by both theoretical calculations and experiments. The results show that the Mie resonance can be continuously tuned across a wide range of wavelength by varying the diameter of the nanopillars. However, Si nanopillar array with uniform diameter exhibits only discrete resonance mode, thus can't achieve a high broadband absorption. On the other hand, the Mie resonance wavelength in a Si nanocone array can vary continuously as the diameters of the cross sections increase from the apex to the base. Therefore Si nanocone arrays can strongly interact with the incident light in the broadband spectrum and the absorbance by Si nanocone arrays is higher than 95% over the wavelength from 300 to 2000 nm. In addition to the Mie resonance, the broadband optical absorption of Si nanocone arrays is also affected by Wood-Rayleigh anomaly effect and metal impurities introduced in the fabrication process.

  20. Customized three-dimensional printed optical phantoms with user defined absorption and scattering

    NASA Astrophysics Data System (ADS)

    Pannem, Sanjana; Sweer, Jordan; Diep, Phuong; Lo, Justine; Snyder, Michael; Stueber, Gabriella; Zhao, Yanyu; Tabassum, Syeda; Istfan, Raeef; Wu, Junjie; Erramilli, Shyamsunder; Roblyer, Darren M.

    2016-03-01

    The use of reliable tissue-simulating phantoms spans multiple applications in spectroscopic imaging including device calibration and testing of new imaging procedures. Three-dimensional (3D) printing allows for the possibility of optical phantoms with arbitrary geometries and spatially varying optical properties. We recently demonstrated the ability to 3D print tissue-simulating phantoms with customized absorption (μa) and reduced scattering (μs`) by incorporating nigrosin, an absorbing dye, and titanium dioxide (TiO2), a scattering agent, to acrylonitrile butadiene styrene (ABS) during filament extrusion. A physiologically relevant range of μa and μs` was demonstrated with high repeatability. We expand our prior work here by evaluating the effect of two important 3D-printing parameters, percent infill and layer height, on both μa and μs`. 2 cm3 cubes were printed with percent infill ranging from 10% to 100% and layer height ranging from 0.15 to 0.40 mm. The range in μa and μs` was 27.3% and 19.5% respectively for different percent infills at 471 nm. For varying layer height, the range in μa and μs` was 27.8% and 15.4% respectively at 471 nm. These results indicate that percent infill and layer height substantially alter optical properties and should be carefully controlled during phantom fabrication. Through the use of inexpensive hobby-level printers, the fabrication of optical phantoms may advance the complexity and availability of fully customizable phantoms over multiple spatial scales. This technique exhibits a wider range of adaptability than other common methods of fabricating optical phantoms and may lead to improved instrument characterization and calibration.

  1. Optical properties of mouse biotissues and their optical phantoms

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    Based on spectrophotometric measurements in the range of 700-1100 nm performed with the use of an integrating sphere, we have obtained absorption and scattering spectra of internal organs of mouse, as well as of aqueous solutions of India ink and Lipofundin, which are basic model media for creating optical phantoms of biological tissues. To retrieve the spectra of optical characteristics, we have used original formulas that relate the parameters of the medium with measured spectrophotometric characteristics and that are constructed based on classical analytical models of propagation of light in turbid media. As a result of comparison of spectra of biotissues and model media, we have developed a mixture of Lipofundin and India ink serving as mouse optical phantoms for problems of optical medical diagnostics.

  2. Third order nonlinear optical property of Bi₂Se₃.

    PubMed

    Lu, Shunbin; Zhao, Chujun; Zou, Yanhong; Chen, Shuqing; Chen, Yu; Li, Ying; Zhang, Han; Wen, Shuangchun; Tang, Dingyuan

    2013-01-28

    The third order nonlinear optical property of Bi₂Se₃, a kind of topological insulator (TI), has been investigated under femto-second laser excitation. The open and closed aperture Z-scan measurements were used to unambiguously distinguish the real and imaginary part of the third order optical nonlinearity of the TI. When excited at 800 nm, the TI exhibits saturable absorption with a saturation intensity of 10.12 GW/cm² and a modulation depth of 61.2%, and a giant nonlinear refractive index of 10⁻¹⁴ m²/W, almost six orders of magnitude larger than that of bulk dielectrics. This finding suggests that the TI:Bi₂Se₃ is indeed a promising nonlinear optical material and thus can find potential applications from passive laser mode locker to optical Kerr effect based photonic devices. PMID:23389188

  3. Quantitation and mapping of tissue optical properties using modulated imaging.

    PubMed

    Cuccia, David J; Bevilacqua, Frederic; Durkin, Anthony J; Ayers, Frederick R; Tromberg, Bruce J

    2009-01-01

    We describe the development of a rapid, noncontact imaging method, modulated imaging (MI), for quantitative, wide-field characterization of optical absorption and scattering properties of turbid media. MI utilizes principles of frequency-domain sampling and model-based analysis of the spatial modulation transfer function (s-MTF). We present and compare analytic diffusion and probabilistic Monte Carlo models of diffuse reflectance in the spatial frequency domain. Next, we perform MI measurements on tissue-simulating phantoms exhibiting a wide range of l values (0.5 mm to 3 mm) and (micro(s) (')micro(a)) ratios (8 to 500), reporting an overall accuracy of approximately 6% and 3% in absorption and reduced scattering parameters, respectively. Sampling of only two spatial frequencies, achieved with only three camera images, is found to be sufficient for accurate determination of the optical properties. We then perform MI measurements in an in vivo tissue system, demonstrating spatial mapping of the absorption and scattering optical contrast in a human forearm and dynamic measurements of a forearm during venous occlusion. Last, metrics of spatial resolution are assessed through both simulations and measurements of spatially heterogeneous phantoms. PMID:19405742

  4. Determination of inherent optical properties of Lake Ontario coastal waters.

    PubMed

    Bukata, R P; Jerome, J H; Bruton, J E; Jain, S C

    1979-12-01

    Two optical models (one based upon Monte Carlo simulations of the solutions of the radiative transfer equations and one based upon exponential/quasi-single scattering simulations) relating the apparent and inherent optical properties of natural water masses are utilized in conjunction with directly measured values of the irradiance attenuation coefficient K(0), the diffuse reflectance R(0), and the total attenuation coefficient c to determine the inherent optical properties of Lake Ontario coastal waters. Tables are presented displaying the calculated values of scattering albedo omega(0), forwardscattering probability F, backscattering probability B, absorption coefficient a, and scattering coefficient b as a function of wavelength. From the tables of calculated values, it is shown that both F and b display a spectral invariance, while omega(0) displays distinct spectral variations, the spectral variations apparent in the measured values of c may be attributable to spectral variations in a, and B displays a spectral change that varies inversely with the spectral change in a and c. The volume scattering phase function beta(theta) appears to be altered by the absorption characteristics of the water mass, contrary to the generally accepted premise that absorption and particulate backscattering are independent processes. PMID:20216727

  5. Frequency-domain method for measuring spectral properties in multiple-scattering media: methemoglobin absorption spectrum in a tissuelike phantom

    NASA Astrophysics Data System (ADS)

    Fishkin, Joshua B.; So, Peter T. C.; Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio; Franceschini, Maria Angela

    1995-03-01

    We have measured the optical absorption and scattering coefficient spectra of a multiple-scattering medium (i.e., a biological tissue-simulating phantom comprising a lipid colloid) containing methemoglobin by using frequency-domain techniques. The methemoglobin absorption spectrum determined in the multiple-scattering medium is in excellent agreement with a corrected methemoglobin absorption spectrum obtained from a steady-state spectrophotometer measurement of the optical density of a minimally scattering medium. The determination of the corrected methemoglobin absorption spectrum takes into account the scattering from impurities in the methemoglobin solution containing no lipid colloid. Frequency-domain techniques allow for the separation of the absorbing from the scattering properties of multiple-scattering media, and these techniques thus provide an absolute

  6. Size dependent nonlinear optical properties of YCrO{sub 3} nanosystems

    SciTech Connect

    Krishnan, Shiji; Shafakath, K.; Philip, Reji; Kalarikkal, Nandakumar

    2014-01-28

    We report size-dependent optical limiting response of YCrO{sub 3} nanosystems upon illumination by nanosecond laser pulses at 532 nm. The limiting properties were investigated using the open aperture z-scan technique. Three-photon absorption coefficient is found to increase with particle size within the range of our investigations. We propose that the obtained nonlinearity is caused by two photon absorption, followed by excited state absorption.

  7. Detection of gastrointestinal cancer by elastic scattering and absorption spectroscopies with the Los Alamos Optical Biopsy System

    SciTech Connect

    Mourant, J.R.; Boyer, J.; Johnson, T.M.; Lacey, J.; Bigio, I.J.; Bohorfoush, A.; Mellow, M.

    1995-03-01

    The Los Alamos National Laboratory has continued the development of the Optical Biopsy System (OBS) for noninvasive, real-time in situ diagnosis of tissue pathologies. In proceedings of earlier SPIE conferences we reported on clinical measurements in the bladder, and we report here on recent results of clinical tests in the gastrointestinal tract. With the OBS, tissue pathologies are detected/diagnosed using spectral measurements of the elastic optical transport properties (scattering and absorption) of the tissue over a wide range of wavelengths. The use of elastic scattering as the key to optical tissue diagnostics in the OBS is based on the fact that many tissue pathologies, including a majority of cancer forms, exhibit significant architectural changes at the cellular and sub-cellular level. Since the cellular components that cause elastic scattering have dimensions typically on the order of visible to near-IR wavelengths, the elastic (Mie) scattering properties will be wavelength dependent. Thus, morphology and size changes can be expected to cause significant changes m an optical signature that is derived from the wavelength-dependence of elastic scattering. Additionally, the optical geometry of the OBS beneficially enhances its sensitivity for measuring absorption bands. The OBS employs a small fiber-optic probe that is amenable to use with any endoscope or catheter, or to direct surface examination, as well as interstitial needle insertion. Data acquistion/display time is <1 second.

  8. Optical and chemical properties of tholins

    NASA Astrophysics Data System (ADS)

    Khare, Bishun N.; McKay, Christopher P.; Cruikshank, Dale P.; Sekine, Yasuhito; Wilhite, Patrick; Ishihara, Tomoko

    2008-10-01

    For over three decades tholins have been synthesized from mixtures of the cosmically abundant gases CH4, C2H6, NH3, H2O, HCHO, N2, and H2, previously in the Laboratory for Planetary Studies at Cornell University and in recent years at NASA Ames Research Center. The tholin synthesized by UV light or spark discharge on sequential and non-sequential pyrolysis GC-MS revealed hundreds of compounds, and on hydrolysis produced a large number of amino acids including racemic protein amino acids. Optical constants have been measured of many of the tholins, tholins produced from a condensed mixture of water and ethane at 77 K, poly HCN, and Titan tholin produced on electrical discharge through a mixture of 90% N2 and 10% CH4. Its optical constants were measured from soft x-rays to microwave for the first time. Here we report the absorption properties of Titan tholin that is produced in the temperature range 135 to 178 K where tholins are produced by magnetospheric charged particles, then pass through lower temperature at 70 K and finally to the ground at 95 K. While descending to the ground, it gets coated and processed on the way by other sources of energy such as long UV and cosmic rays. It is therefore expected that the stable products of CH4 photolysis react with Titan tholin to recycle the CH4 supply in Titan's atmosphere. Furthermore, the reactions of gaseous C2H6 with the reactive materials on the surface of the tholin could incorporate atmospheric C2H6 into the tholin and therefore might reduce the deposition rate of C2H6 onto the ground of Titan.

  9. Light absorption properties and radiative effects of primary organic aerosol emissions.

    PubMed

    Lu, Zifeng; Streets, David G; Winijkul, Ekbordin; Yan, Fang; Chen, Yanju; Bond, Tami C; Feng, Yan; Dubey, Manvendra K; Liu, Shang; Pinto, Joseph P; Carmichael, Gregory R

    2015-04-21

    Organic aerosols (OAs) in the atmosphere affect Earth's energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called "brown carbon" (BrC) component. However, the absorptivities of OAs are not represented or are poorly represented in current climate and chemical transport models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle's absorptivity) and their uncertainties for the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parametrize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, indicating that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory, and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ∼27% reduction in the amount of the net global average POA cooling compared to results from the nonabsorbing assumption. PMID:25811601

  10. Optical properties of borate crystals in terahertz region

    NASA Astrophysics Data System (ADS)

    Antsygin, V. D.; Mamrashev, A. A.; Nikolaev, N. A.; Potaturkin, O. I.; Bekker, T. B.; Solntsev, V. P.

    2013-11-01

    In this paper we study the optical properties of a family of borate crystals comprising alpha and beta barium borates, barium fluoroborate, lithium triborate, and lithium tetraborate in the frequency range from 0.3 to 2.0 THz. We extract the refractive indices and absorption coefficients for both ordinary and extraordinary beams from terahertz time-domain spectroscopy data. All of the investigated crystals exhibit substantial birefringence and dichroism, which qualifies them as potential materials for terahertz polarization-optical devices. We also find an additional absorption band in barium borate crystals, which is not defined by the group of phonon modes lying above 2 THz. We argue that this phenomenon may be caused by excessive sodium atoms and ions in the crystal lattice.

  11. Modeling silica aerogel optical performance by determining its radiative properties

    NASA Astrophysics Data System (ADS)

    Zhao, Lin; Yang, Sungwoo; Bhatia, Bikram; Strobach, Elise; Wang, Evelyn N.

    2016-02-01

    Silica aerogel has been known as a promising candidate for high performance transparent insulation material (TIM). Optical transparency is a crucial metric for silica aerogels in many solar related applications. Both scattering and absorption can reduce the amount of light transmitted through an aerogel slab. Due to multiple scattering, the transmittance deviates from the Beer-Lambert law (exponential attenuation). To better understand its optical performance, we decoupled and quantified the extinction contributions of absorption and scattering separately by identifying two sets of radiative properties. The radiative properties are deduced from the measured total transmittance and reflectance spectra (from 250 nm to 2500 nm) of synthesized aerogel samples by solving the inverse problem of the 1-D Radiative Transfer Equation (RTE). The obtained radiative properties are found to be independent of the sample geometry and can be considered intrinsic material properties, which originate from the aerogel's microstructure. This finding allows for these properties to be directly compared between different samples. We also demonstrate that by using the obtained radiative properties, we can model the photon transport in aerogels of arbitrary shapes, where an analytical solution is difficult to obtain.

  12. Light absorption properties of laboratory-generated tar ball particles

    NASA Astrophysics Data System (ADS)

    Hoffer, A.; Tóth, A.; Nyirő-Kósa, I.; Pósfai, M.; Gelencsér, A.

    2016-01-01

    Tar balls (TBs) are a specific particle type that is abundant in the global troposphere, in particular in biomass smoke plumes. These particles belong to the family of atmospheric brown carbon (BrC), which can absorb light in the visible range of the solar spectrum. Albeit TBs are typically present as individual particles in biomass smoke plumes, their absorption properties have been only indirectly inferred from field observations or calculations based on their electron energy-loss spectra. This is because in biomass smoke TBs coexist with various other particle types (e.g., organic particles with inorganic inclusions and soot, the latter emitted mainly during flaming conditions) from which they cannot be physically separated; thus, a direct experimental determination of their absorption properties is not feasible. Very recently we have demonstrated that TBs can be generated in the laboratory from droplets of wood tar that resemble atmospheric TBs in all of their observed properties. As a follow-up study, we have installed on-line instruments to our laboratory set-up, which generate pure TB particles to measure the absorption and scattering, as well as the size distribution of the particles. In addition, samples were collected for transmission electron microscopy (TEM) and total carbon (TC) analysis. The effects of experimental parameters were also studied. The mass absorption coefficients of the laboratory-generated TBs were found to be in the range of 0.8-3.0 m2 g-1 at 550 nm, with absorption Ångström exponents (AAE) between 2.7 and 3.4 (average 2.9) in the wavelength range 467-652 nm. The refractive index of TBs as derived from Mie calculations was about 1.84 - 0.21i at 550 nm. In the brown carbon continuum, these values fall closer to those of soot than to other light-absorbing species such as humic-like substances (HULIS). Considering the abundance of TBs in biomass smoke and the global magnitude of biomass burning emissions, these findings may have

  13. Light absorption properties of laboratory generated tar ball particles

    NASA Astrophysics Data System (ADS)

    Hoffer, A.; Tóth, A.; Nyirő-Kósa, I.; Pósfai, M.; Gelencsér, A.

    2015-06-01

    Tar balls (TBs) are a specific particle type which is abundant in the global troposphere, in particular in biomass smoke plumes. These particles belong to the family of atmospheric brown carbon (BrC) which can absorb light in the visible range of the solar spectrum. Albeit TBs are typically present as individual particles in biomass smoke plumes, their absorption properties have been only indirectly inferred from field observations or calculations based on their electron energy-loss spectra. This is because in biomass smoke TBs coexist with various other particle types (e.g. organic particles with inorganic inclusions and soot, the latter is emitted mainly during flaming conditions) from which they cannot be physically separated; thus, a direct experimental determination of their absorption properties is not feasible. Very recently we have demonstrated that TBs can be generated in the laboratory from droplets of wood tar that resemble atmospheric TBs in all of their observed properties. As a follow-up study we have installed on-line instruments to our laboratory set-up generating pure TB particles to measure the absorption and scattering, as well as size distribution of the particles. In addition, samples were collected for transmission electron microscopy (TEM) and total carbon (TC) analysis. The effects of experimental parameters were also studied. The mass absorption coefficients of the laboratory generated TBs were found to be in the range of 0.8-3.0 m2 g-1 at 550 nm, with absorption Ångström exponents (AAE) between 2.7 and 3.4 (average 2.9) in the wavelength range 467-652 nm. The refractive index of TBs as derived from Mie calculations was about 1.84-0.21i at 550 nm. In the brown carbon continuum these values fall closer to those of soot than to other light-absorbing species such as humic-like substances (HULIS). Considering the abundance of TBs in biomass smoke and the global magnitude of biomass burning emissions, these findings may have substantial

  14. Multi-spectral optical absorption in substrate-free nanowire arrays

    SciTech Connect

    Zhang, Junpeng; Chia, Andrew; Boulanger, Jonathan; LaPierre, Ray; Dhindsa, Navneet; Khodadad, Iman; Saini, Simarjeet

    2014-09-22

    A method is presented of fabricating gallium arsenide (GaAs) nanowire arrays of controlled diameter and period by reactive ion etching of a GaAs substrate containing an indium gallium arsenide (InGaP) etch stop layer, allowing the precise nanowire length to be controlled. The substrate is subsequently removed by selective etching, using the same InGaP etch stop layer, to create a substrate-free GaAs nanowire array. The optical absorptance of the nanowire array was then directly measured without absorption from a substrate. We directly observe absorptance spectra that can be tuned by the nanowire diameter, as explained with rigorous coupled wave analysis. These results illustrate strong optical absorption suitable for nanowire-based solar cells and multi-spectral absorption for wavelength discriminating photodetectors. The solar-weighted absorptance above the bandgap of GaAs was 94% for a nanowire surface coverage of only 15%.

  15. Ultrasensitive optical absorption in graphene based on bound states in the continuum

    PubMed Central

    Zhang, Mingda; Zhang, Xiangdong

    2015-01-01

    We have designed a sphere-graphene-slab structure so that the electromagnetic wave can be well confined in the graphene due to the formation of a bound state in a continuum (BIC) of radiation modes. Based on such a bound state, we have realized strong optical absorption in the monolayer graphene. Such a strong optical absorption exhibits many advantages. It is ultrasensitive to the wavelength because the Q factor of the absorption peak can be more than 2000. By taking suitable BICs, the selective absorption for S and P waves has not only been realized, but also all-angle absorption for the S and P waves at the same time has been demonstrated. We have also found that ultrasensitive strong absorptions can appear at any wavelength from mid-infrared to far-infrared band. These phenomena are very beneficial to biosensing, perfect filters and waveguides. PMID:25652437

  16. Experimental measurements of the spectral absorption coefficient of pure fused silica optical fibers.

    PubMed

    Moore, Travis J; Jones, Matthew R

    2015-02-20

    Knowledge of the spectral absorption coefficient of fused silica optical fibers is important in modeling heat transfer in the processes and applications in which these fibers are used. An experimental method used to measure the spectral absorption coefficient of optical fibers is presented. Radiative energy from a blackbody radiator set at different temperatures is directed through the optical fibers and into an FTIR spectrometer. Spectral instrument response functions are calculated for different fiber lengths. The ratios of the slopes of the instrument response functions for the different lengths of fibers are used to solve for the spectral absorption coefficient of the fibers. The spectral absorption coefficient of low OH pure fused silica optical fibers is measured between the wavelengths 1.5 and 2.5 μm. PMID:25968202

  17. Characterization and Processing of Organic Nonlinear Optical Materials using Ellipsometric, Waveguiding, and Absorption Spectroscopy Techniques

    NASA Astrophysics Data System (ADS)

    Olbricht, Benjamin C.

    The first focus of this work is to describe methods for characterizing organic electro-optic materials. Teng-Man Ellipsometry and Attenuated Total Internal Reflection are reviewed. Experimental techniques for these instruments are described and the calculation of an electro-optic activity is derived. The two techniques are compared; it has been found that in Situ Teng-Man ellipsometry is useful to determine poling conditions but not for reliably evaluating electro-optic activity. Attenuated Total Internal Reflection is found to provide very reliable and precise measurements of electro-optic activity and linear optical constants. As a reference, many materials systems have been evaluated and their electro-optic activities are recorded herein. Methods for fabricating devices for test by Teng-Man ellipsometry and Attenuated Total Internal Reflection are presented. A process for inducing Pockel's response via contact-geometry electric field poling is also described, along with modifications to the simple slab dielectric device to enhance the efficacy of poling. An additional method for enhancing the efficiency of poling is presented. This technique relies on the photoisomerization of azobenzene dyes under 532nm radiation to reduce the dimensionality accessible to chromophores doped into the azobenzene matrix. This effect is known as "Laser Assisted Poling" and is shown to increase poling efficiency by more than two fold. The second purpose of this work is to present an experimental technique to measure the order parameter = 3cos 2q -12 . This method is known as Variable-Angle Polarization-Referenced Absorption Spectroscopy (VAPRAS). The experimental apparatus used for VAPRAS introduces small alterations to a UV/Vis Spectrophotometer and an order parameter is derived by exclusively using classical models for transmittance. VAPRAS provides an effective refractive index for the electro-optic material film which is used to calculate the order of absorbers in the film

  18. Electromagnetic absorption properties of graphene/Fe nanocomposites

    SciTech Connect

    Chen, Yujin; Lei, Zhenyu; Wu, Hongyu; Zhu, Chunling; Gao, Peng; Ouyang, Qiuyun; Qi, Li-Hong; Qin, Wei

    2013-09-01

    Graphical abstract: - Highlights: • Graphene/Fe nanocomposites were prepared by a facile and green method. • 10 nm Fe nanoparticles were uniformly dispersed over the surface of the graphene sheets. • The nanocomposites exhibited strong electromagnetic wave absorption properties. - Abstract: Graphene (G)/Fe nanocomposites with ferromagnetic properties at room temperature were fabricated by a facile and green method. Transmission electron microscope (TEM) and atomic force microscopy (AFM) amylases reveal that the α-Fe nanoparticles with a diameter of only about 10 nm were uniformly dispersed over the surface of the graphene sheets. Compared with other magnetic materials and the graphene, the nanocomposites exhibited significantly enhanced electromagnetic absorption properties. The maximum reflection loss to electromagnetic wave was up to −31.5 dB at a frequency of 14.2 GHz for G/Fe nanocomposites with a thickness of 2.5 mm. Importantly, the addition of the nanocomposites is only about 20 wt.% in the matrix. The enhanced mechanism is discussed and it is related to high surface areas of G/Fe nanocomposites, interfacial polarizations between graphene and iron, synergetic effect and efficient dispersity of magnetic NPs.

  19. Discrepancy between ambient annealing and H+ implantation in optical absorption of ZnO

    NASA Astrophysics Data System (ADS)

    Lv, Jinpeng; Li, Chundong

    2016-05-01

    The discrepancy between sub-bandgap absorption in ZnO induced by thermal annealing and H+ implantation is investigated in this study for the first time. Results indicate that nonreductive annealing-induced optical absorption is independent of annealing ambient, and can be assigned to VO, whereas the absorption centers caused by H+ implantation and H2 annealing are primarily associated with VO and ionized Zni.

  20. Effect of Central Metal on Nonlinear Optical Properties of Porphyrins and Their Graphene Composites

    NASA Astrophysics Data System (ADS)

    Leng, Jian-Cai; Zhao, Li-Yun; Zhang, Yu-Jin; Ma, Hong

    2016-09-01

    The nonlinear optical properties of a series of newly synthesized porphyrins with different central metals and their covalently linked graphene composites are theoretically studied by numerically solving the rate equations and field intensity equation. Calculated results show that all the studied compounds are promising candidates for optical limiters, and graphene-porphyrin composites are expected to be preferable optical limiters because of their excellent nonlinear absorption abilities. In addition, the central metal in the porphyrin is found to be crucial to the optical power limiting and two-photon absorption performances of the compounds. Our results reproduce the experimental measurements. Additionally, special emphasis is placed on the factors that can affect the nonlinear optical properties of the compounds, indicating that one can create favorable nonlinear optical properties of the compounds by changing either the parameters of the absorber, including the concentration and thickness, or the pulse duration.

  1. Exciton states and optical properties of carbon nanotubes.

    PubMed

    Ajiki, Hiroshi

    2012-12-01

    Exciton states and related optical properties of a single-walled carbon nanotube are reviewed, primarily from a theoretical viewpoint. The energies and wavefunctions of excitons are discussed using a screened Hartree-Fock approximation with an effective-mass or k·p approximation. The close relationship between a long-range electron-hole exchange interaction and a depolarization effect is clarified. I discuss optical properties including the radiative lifetime of excitons, absorption spectra and radiation force. To describe these properties in a unified scheme, a self-consistent method is introduced for calculating the scattering light and induced current density due to excitons. I also briefly review experimental results on the Aharonov-Bohm effect in excitons and quasi-dark excitons excited by light polarized perpendicular to the tube axis. PMID:23139202

  2. Optical properties of natural topaz

    NASA Astrophysics Data System (ADS)

    Skvortsova, V.; Mironova-Ulmane, N.; Trinkler, L.; Chikvaidze, G.

    2013-12-01

    The results of investigation of infrared, Raman and UV-Visible absorption spectra of natural topaz crystals from Ukraine before and after fast neutron irradiation are presented. We assume that the ~ 620 nm band in topaz crystals is associated with the presence of Cr3+, Fe2+ and Mn2+ impurities. The broad band with maxima at 650 cm-1 observed in Raman spectra for topaz irradiated by fast neutrons may be connected with lattice disorder. Exchange interaction between radiation defect and impurity ions during neutron irradiation leads to appearance of additional absorption band in UV-VIS spectra and bands broadening in infrared and Raman spectra of investigated crystals.

  3. Tight binding model of conformational disorder effects on the optical absorption spectrum of polythiophenes.

    PubMed

    Bombile, Joel H; Janik, Michael J; Milner, Scott T

    2016-05-14

    Semiconducting polymers are soft materials with many conformational degrees of freedom. The limited understanding of how conformational disorder affects their optoelectronic properties is a key source of difficulties that limits their widespread usage in electronic devices. We develop a coarse-grained approach based on the tight binding approximation to model the electronic degrees of freedom of polythiophene chains, taking into account conformational degrees of freedom. Particularly important is dihedral disorder, which disrupts extended electronic states. Our tight binding model is parameterized using density functional theory (DFT) calculations of the one-dimensional band structures for chains with imposed periodic variations in dihedral angles. The model predicts valence and conduction bands for these chain conformations that compare well to DFT results. As an initial application of our model, we compute the optical absorption spectrum of poly(3-hexylthiophene) chains in solution. We observe a broadening of the absorption edge resulting from dihedral disorder, just shy of the experimental broadening. We conclude that the effects of molecular disorder on the optoelectronic properties of conjugated polymer single chains can be mostly accounted for by torsional disorder alone. PMID:27087455

  4. Effect of UV Absorption on Fabrication of Fiber-Optic Bragg Gratings

    NASA Technical Reports Server (NTRS)

    Wang, Ying; Sharma, Anup; Burdine, Robert (Technical Monitor)

    2000-01-01

    UV light is used to fabricate fiber-optic gratings also heats up the fiber due to absorption by either the fiber-buffer, fiber-cladding, doped with titania or a thin coating of paint. Significant enhancement in the rate of grating fabrication is observed due to UV light absorption.

  5. OPTICAL ABSORPTION AND PHOTOLUMINESCENCE IN PRISTINE AND PHOTOPOLYMERIZED C60 SOLID FILMS

    EPA Science Inventory

    The optical absorption (OA) and photoluminescence (PL) spectra of pristine, oxygen-free C60 films in the vicinity of the absorption edge across the highest-occupied-molecular-orbital to lowest-unoccupied-molecular-orbital (HOMO-LUMO) gap are studied to elucidate the nature of the...

  6. Differential optical absorption techniques for diagnostics of coal gasification. Technical progress report, April-June 1983

    SciTech Connect

    Not Available

    1983-08-01

    The application of differential optical absorption (DOA) techniques for the in-situ determination of the chemical composition of coal gasification process streams is investigated. Absorption spectra of relevant molecular species and the temperature and pressure effects on DOA-determined spectral characteristics of these species will be determined and cataloged. A system will be configured, assembled, and tested. 10 references, 1 figure.

  7. Plasmonic nanogels with robustly tunable optical properties

    NASA Astrophysics Data System (ADS)

    Cong, Tao; Wani, Satvik N.; Zhou, Georo; Baszczuk, Elia; Sureshkumar, Radhakrishna

    2011-10-01

    Low viscosity fluids with tunable optical properties can be processed to manufacture thin film and interfaces for molecular detection, light trapping in photovoltaics and reconfigurable optofluidic devices. In this work, self-assembly in wormlike micelle solutions is used to uniformly distribute various metallic nanoparticles to produce stable suspensions with localized, multiple wavelength or broad-band optical properties. Their spectral response can be robustly modified by varying the species, concentration, size and/or shape of the nanoparticles. Structure, rheology and optical properties of these plasmonic nanogels as well as their potential applications to efficient photovoltaics design are discussed.

  8. Design and synthesis of liquid crystals with controlled absorption properties in the midwave infrared region

    NASA Astrophysics Data System (ADS)

    Tripathi, Suvagata

    The infrared region of electromagnetic radiation is attractive for communication applications as the scattering is lower compared to that in the visible spectrum. Infrared lasers are widely used in bar-code scanners, laser rangefinders and topology mapping applications. Typically, the direction of a laser beam is altered by mechanically moving a mirror or a lens. But this process can impose severe limitations on critical performance parameters (longevity, precision, response time etc.) of the device. Thus, electro-optic control of the direction of the beam is highly desired. Commercial liquid crystals (LCs) are less than ideal for this purpose because they almost invariably have several absorption bands in the infrared region. For example, several absorption bands exist in the mid-infrared region (3-5 mum) due to common structure features found in LCs such as CH, CH 2, CH3 and CN. In the off-resonance regions, the baseline absorption coefficient can take very high value (up to alpha ~10/cm). This absorption loss becomes especially significant if the optical path is long. As the molecular vibration frequency (o) depends upon the spring constant (kappa) and the effective mass (m) of a diatomic group by the equation = √(kappa/m), replacement of hydrogen atoms in a molecule with heavier atoms can shift the absorptions to the far infrared region, thus making the midwave infrared region more transparent. Another strategy has been to develop high birefringence LCs so that lower liquid crystal cell gap can be used, thus minimizing the absorption loss due to the LC layer. But most of these materials have problems with UV stability. In the scope of this thesis, several strategies are investigated to mitigate the absorption loss in the midwave infrared region. The ultimate goal of this thesis is to develop LCs that will have both high birefringence and low absorption properties in the midwave-infrared region. Another goal of the thesis is to develop materials for

  9. Gold nanorods-silicone hybrid material films and their optical limiting property

    NASA Astrophysics Data System (ADS)

    Li, Chunfang; Qi, Yanhai; Hao, Xiongwen; Peng, Xue; Li, Dongxiang

    2015-10-01

    As a kind of new optical limiting materials, gold nanoparticles have optical limiting property owing to their optical nonlinearities induced by surface plasmon resonance (SPR). Gold nanorods (GNRs) possess transversal SPR absorption and tunable longitudinal SPR absorption in the visible and near-infrared region, so they can be used as potential optical limiting materials against tunable laser pulses. In this letter, GNRs were prepared using seed-mediated growth method and surface-modified by silica coating to obtain good dispersion in polydimethylsiloxane prepolymers. Then the silicone rubber films doped with GNRs were prepared after vulcanization, whose optical limiting property and optical nonlinearity were investigated. The silicone rubber samples doped with more GNRs were found to exhibit better optical limiting performance.

  10. Neutron-induced changes in optical properties of MgAl 2O 4 spinel

    NASA Astrophysics Data System (ADS)

    Ibarra, A.; Garner, F. A.; Hollenberg, G. L.

    1995-03-01

    High purity MgAl 2O 4 spinel specimens irradiated in FFTF-MOTA to very high neutron exposures have been examined by three techniques to determine changes in their optical properties. Significant changes were observed in optical absorption, photoluminescence and radioluminescence, indicating that a variety of radiation-induced defects are present in these specimens.

  11. Unified theory of electron-phonon renormalization and phonon-assisted optical absorption

    NASA Astrophysics Data System (ADS)

    Patrick, Christopher E.; Giustino, Feliciano

    2014-09-01

    We present a theory of electronic excitation energies and optical absorption spectra which incorporates energy-level renormalization and phonon-assisted optical absorption within a unified framework. Using time-independent perturbation theory we show how the standard approaches for studying vibronic effects in molecules and those for addressing electron-phonon interactions in solids correspond to slightly different choices for the non-interacting Hamiltonian. Our present approach naturally leads to the Allen-Heine theory of temperature-dependent energy levels, the Franck-Condon principle, the Herzberg-Teller effect and to phonon-assisted optical absorption in indirect band gap materials. In addition, our theory predicts sub-gap phonon-assisted optical absorption in direct gap materials, as well as an exponential edge which we tentatively assign to the Urbach tail. We also consider a semiclassical approach to the calculation of optical absorption spectra which simultaneously captures energy-level renormalization and phonon-assisted transitions and is especially suited to first-principles electronic structure calculations. We demonstrate this approach by calculating the phonon-assisted optical absorption spectrum of bulk silicon.

  12. Studying Velocity Turbulence from Doppler-broadened Absorption Lines: Statistics of Optical Depth Fluctuations

    SciTech Connect

    Lazarian, A.; Pogosyan, D.

    2008-10-10

    We continue our work on developing techniques for studying turbulence with spectroscopic data. We show that Doppler-broadened absorption spectral lines, in particular, saturated absorption lines, can be used within the framework of the previously introduced technique termed the velocity coordinate spectrum (VCS). The VCS relates the statistics of fluctuations along the velocity coordinate to the statistics of turbulence; thus, it does not require spatial coverage by sampling directions in the plane of the sky. We consider lines with different degree of absorption and show that for lines of optical depth less than one, our earlier treatment of the VCS developed for spectral emission lines is applicable, if the optical depth is used instead of intensity. This amounts to correlating the logarithms of absorbed intensities. For larger optical depths and saturated absorption lines, we show that only wings of the line are available for the analysis. In terms of the VCS formalism, this results in introducing an additional window, whose size decreases with the increase of the optical depth. As a result, strongly saturated absorption lines only carry the information about the small-scale turbulence. Nevertheless, the contrast of the fluctuations corresponding to the small-scale turbulence increases with the increase of the optical depth, which provides advantages for studying turbulence by combining lines with different optical depths. By combining different absorption lines one can develop a tomography of the turbulence in the interstellar gas in all its complexity.

  13. Alloyed Noble Metal Nanoparticles with Tunable Optical Properties

    NASA Astrophysics Data System (ADS)

    Wessler, Garrett C.; Gong, Chen; Rebello de Sousa Dias, Mariama; Tailon, Joshua A.; Salamanca-Riba, Lourdes G.; Leite, Marina S.

    Noble metal nanoparticles (NPs) have been widely used in sensing, optics, and catalysis applications by taking advantage of surface plasmon resonance (SPR). This response is slightly tuned by varying the size and shape of the NPs; however, a method to obtain truly on-demand plasmonic responses is still lacking due to the intrinsic nature of a metal's dielectric function. Here, we fabricate size and composition controlled metal alloy NP arrays by deposit-and-anneal methods and through-template depositions. We control the composition of the metal NPs by co-sputtering and by alternating electron-beam evaporation of the Ag and Au targets. To characterize the NPs, macroscopic transmission measurements are combined with spectrally dependent near-field scanning optical microscopy to show the local optical properties around the NPs. By varying the atomic fraction of Ag and Au in the alloys, we modulate the optical properties of the NPs for different applications. For example, hot carrier plasmonic devices necessitate high absorption in the visible range, while photovoltaic applications require low absorption by the NPs.

  14. Tunable optical and magneto-optical properties of ferrofluid in the terahertz regime.

    PubMed

    Chen, Sai; Fan, Fei; Chang, Shengjiang; Miao, Yinping; Chen, Meng; Li, Jining; Wang, Xianghui; Lin, Lie

    2014-03-24

    The dielectric property and magneto-optical effects of ferrofluids have been investigated in the terahertz (THz) regime by using THz time-domain spectroscopy. The experiment results show that the refractive index and absorption coefficient of ferrofluid for THz waves rise up with the increase of nanoparticle concentration in the ferrofluid. Moreover, two different THz magneto-optical effects have been found with different external magnetic fields, of which mechanisms have been theoretically explained well by microscopic structure induced refractive index change in the magnetization process and the transverse magneto-optical effect after the saturation magnetization, respectively. This work suggests that ferrofluid is a promising magneto-optical material in the THz regime which has widely potential applications in THz functional devices for THz sensing, modulation, phase retardation, and polarization control. PMID:24663979

  15. Designing Optical Properties in DNA-Programmed Nanoparticle Superlattices

    NASA Astrophysics Data System (ADS)

    Ross, Michael Brendan

    can be used to influence the properties of mesoscale single crystal superlattices, such that they exhibit either plasmonic absorption or photonic scattering. This concept is generalized through simulation, which demonstrates that the crystal habit (size, shape, and morphology) is a powerful design parameter for optical properties in mesoscale nanoparticle assemblies. Finally, chapter 7 summarizes these data and their impact, and puts them in context regarding future opportunities. This work presents a comprehensive demonstration that the optical properties of nanoparticle-based architectures can be precisely controlled and deliberately designed a priori using the unique programmability of DNA and the use of several levels of predictive electromagnetic theory.

  16. Noise-driven optical absorption coefficients of impurity doped quantum dots

    NASA Astrophysics Data System (ADS)

    Ganguly, Jayanta; Saha, Surajit; Pal, Suvajit; Ghosh, Manas

    2016-01-01

    We make an extensive investigation of linear, third-order nonlinear, and total optical absorption coefficients (ACs) of impurity doped quantum dots (QDs) in presence and absence of noise. The noise invoked in the present study is a Gaussian white noise. The quantum dot is doped with repulsive Gaussian impurity. Noise has been introduced to the system additively and multiplicatively. A perpendicular magnetic field acts as a source of confinement and a static external electric field has been applied. The AC profiles have been studied as a function of incident photon energy when several important parameters such as optical intensity, electric field strength, magnetic field strength, confinement energy, dopant location, relaxation time, Al concentration, dopant potential, and noise strength take on different values. In addition, the role of mode of application of noise (additive/multiplicative) on the AC profiles has also been analyzed meticulously. The AC profiles often consist of a number of interesting observations such as one photon resonance enhancement, shift of AC peak position, variation of AC peak intensity, and bleaching of AC peak. However, presence of noise alters the features of AC profiles and leads to some interesting manifestations. Multiplicative noise brings about more complexity in the AC profiles than its additive counterpart. The observations indeed illuminate several useful aspects in the study of linear and nonlinear optical properties of doped QD systems, specially in presence of noise. The findings are expected to be quite relevant from a technological perspective.

  17. Optical properties of dielectric thin films including quantum dots

    NASA Astrophysics Data System (ADS)

    Flory, F.; Chen, Y. J.; Lee, C. C.; Escoubas, L.; Simon, J. J.; Torchio, P.; Le Rouzo, J.; Vedraine, S.; Derbal-Habak, Hassina; Ackermann, Jorg; Shupyk, Ivan; Didane, Yahia

    2010-08-01

    Depending on the minimum size of their micro/nano structure, thin films can exhibit very different behaviors and optical properties. From optical waveguides down to artificial anisotropy, through diffractive optics and photonic crystals, the application changes when decreasing the minimum feature size. Rigorous electromagnetic theory can be used to model most of the components but when the size is of a few nanometers, quantum theory has also to be used. These materials including quantum structures are of particular interest for other applications, in particular for solar cells, because of their luminescent and electronic properties. We show that the properties of electrons in multiple quantum wells can be easily modeled with a formalism similar to that used for multilayer waveguides. The effects of different parameters, in particular coupling between wells and well thickness dispersion, on possible discrete energy levels or energy band of electrons and on electron wave functions is given. When such quantum confinement appears the spectral absorption and the extinction coefficient dispersion with wavelength is modified. The dispersion of the real part of the refractive index can then be deduced from the Kramers- Krönig relations. Associated with homogenization theory this approach gives a new model of refractive index for thin films including quantum dots. Absorption spectra of samples composed of ZnO quantum dots in PMMA layers are in preparation are given.

  18. Synthesizing Diacetylenes With Nonlinear Optical Properties

    NASA Technical Reports Server (NTRS)

    Mcmanus, Samuel P.; Frazier, Donald P.; Paley, Mark S.

    1993-01-01

    Diacetylene compounds being investigated to determine whether they have nonlinear optical properties making them useful for four-wave mixing, generation of third harmonics, phase conjugation, and like. Diacetylene monomers synthesized by sequences of chemical reactions. Monomers polymerized by ultraviolet light, forming potentially useful nonlinear optical materials.

  19. Study of the nanosurface properties by analyzing its absorption and scattering cross-section

    NASA Astrophysics Data System (ADS)

    Bariakhtar, Irina

    The interest to study the nanoparticles absorbed on the dielectric or semiconductor substrate is caused by the multiple practical applications of these systems such as nanosensors, electronic devices and lately in PV elements for improving of their efficiency. The author suggests a method of examining the properties of the nanosurface with the absorbed nanoparticle by calculating the absorption and scattering of the electromagnetic field by such system based on construction of its effective electric susceptibility. It was built based on the Green's function approach. The computer simulations show good correspondence with the theory. It was shown that this approach can be applied to investigate the optical absorption and scattering on the nanoparticles on the substrate to be used in PV engineering.

  20. Absorption Coefficient Imaging by Near-Field Scanning Optical Microscopy in Bacteria

    NASA Astrophysics Data System (ADS)

    de Paula, Ana M.; Chaves, Claudilene R.; Silva, Haroldo B.; Weber, Gerald

    2003-06-01

    We present a method for obtaining a position-dependent absorption coefficient from near-field scanning optical transmission microscopy. We show that the optical transmission intensity can be combined with the topography, resulting into an absorption coefficient that simplifies the analysis of different materials within a sample. The method is tested with the dye rhodamine 6G, and we show some analysis in biological samples such as bacteria Klebsiella pneumoniae and Pseudomonas aeruginosa . The calculated absorption coefficient images show important details of the bacteria, in particular for P. aeruginosa , in which membrane vesicles are clearly seen.

  1. Systems having optical absorption layer for mid and long wave infrared and methods for making the same

    SciTech Connect

    Kuzmenko, Paul J

    2013-10-01

    An optical system according to one embodiment includes a substrate; and an optical absorption layer coupled to the substrate, wherein the optical absorption layer comprises a layer of diamond-like carbon, wherein the optical absorption layer absorbs at least 50% of mid wave infrared light (3-5 .mu.m wavelength) and at least 50% of long wave infrared light (8-13 .mu.m wavelength). A method for applying an optical absorption layer to an optical system according to another embodiment includes depositing a layer of diamond-like carbon of an optical absorption layer above a substrate using plasma enhanced chemical vapor deposition, wherein the optical absorption layer absorbs at least 50% of mid wave infrared light (3-5 .mu.m wavelength) and at least 50% of long wave infrared light (8-13 .mu.m wavelength). Additional systems and methods are also presented.

  2. Effects of crossed electric and magnetic fields on the interband optical absorption spectra of variably spaced semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Zuleta, J. N.; Reyes-Gómez, E.

    2016-05-01

    The interband optical absorption spectra of a GaAs-Ga1-xAlxAs variably spaced semiconductor superlattice under crossed in-plane magnetic and growth-direction applied electric fields are theoretically investigated. The electronic structure, transition strengths and interband absorption coefficients are analyzed within the weak and strong magnetic-field regimes. A dramatic quenching of the absorption coefficient is observed, in the weak magnetic-field regime, as the applied electric field is increased, in good agreement with previous experimental measurements performed in a similar system under growth-direction applied electric fields. A decrease of the resonant tunneling in the superlattice is also theoretically obtained in the strong magnetic-field regime. Moreover, in this case, we found an interband absorption coefficient weakly dependent on the applied electric field. Present theoretical results suggest that an in-plane magnetic field may be used to tune the optical properties of variably spaced semiconductor superlattices, with possible future applications in solar cells and magneto-optical devices.

  3. Optical properties of Aeolian dusts common to West Texas

    NASA Astrophysics Data System (ADS)

    Ma, Lulu; Zobeck, Ted M.; Hsieh, Daniel H.; Holder, Dean; Morgan, Cristine L. S.; Thompson, Jonathan E.

    2011-11-01

    Both recent models and historical events such as the Dust Bowl and volcanic eruptions have illustrated aerosols can play a significant role in climate change through direct and indirect optical effects. Soil dust aerosols generated by Aeolian processes represent a significant fraction of the total mass burden of atmospheric particles. Central to a better understanding of the climate effects of dust aerosols is knowledge of their optical properties. This research study utilized a dust generator and several instruments to determine certain optical properties of Aeolian dust mimics created by the Amarillo and Pullman soil types native to the panhandle of Texas, USA. Values for the mass-extinction coefficient ranged between 1.74 and 2.97 m 2 g -1 at 522 nm depending on how mass concentration was determined. Single-scatter albedo (SSA) for both soil types ranged from 0.947 to 0.980 at visible wavelengths with SSA increasing at longer wavelengths. Angstrom absorption exponents were measured as 1.73 for Pullman and 2.17 for Amarillo soil. Observed Angstrom extinction exponents were 0.110 and 0.168 for the Pullman and Amarillo soil types. The optical properties reported may be of use for optical based estimates of soil erosion and aid in understanding how regional soil dusts may alter radiative transport presently and during historical events such as the Dust Bowl era.

  4. Designing Ligand-Enhanced Optical Absorption of Thiolated Gold Nanoclusters

    SciTech Connect

    Sementa, Luca; Barcaro, Giovanni; Dass, Amala; Stener, Mauro; Fortunelli, Alessandro

    2015-05-07

    The optical spectra of thiolated Au25(SR)18/Au23(SR)16 clusters with different R residues are investigated via TDDFT simulations. Significant enhancements in the optical region and effective electron delocalization are simultaneously achieved by tuning the ligands' steric hindrance and electronic conjugating features, producing a resonance phenomenon between the Au–S core motif and the ligand fragments.

  5. Experimental and theoretical optical properties of methylammonium lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Leguy, Aurélien M. A.; Azarhoosh, Pooya; Alonso, M. Isabel; Campoy-Quiles, Mariano; Weber, Oliver J.; Yao, Jizhong; Bryant, Daniel; Weller, Mark T.; Nelson, Jenny; Walsh, Aron; van Schilfgaarde, Mark; Barnes, Piers R. F.

    2016-03-01

    The optical constants of methylammonium lead halide single crystals CH3NH3PbX3 (X = I, Br, Cl) are interpreted with high level ab initio calculations using the relativistic quasiparticle self-consistent GW approximation (QSGW). Good agreement between the optical constants derived from QSGW and those obtained from spectroscopic ellipsometry enables the assignment of the spectral features to their respective inter-band transitions. We show that the transition from the highest valence band (VB) to the lowest conduction band (CB) is responsible for almost all the optical response of MAPbI3 between 1.2 and 5.5 eV (with minor contributions from the second highest VB and the second lowest CB). The calculations indicate that the orientation of [CH3NH3]+ cations has a significant influence on the position of the bandgap suggesting that collective orientation of the organic moieties could result in significant local variations of the optical properties. The optical constants and energy band diagram of CH3NH3PbI3 are then used to simulate the contributions from different optical transitions to a typical transient absorption spectrum (TAS).The optical constants of methylammonium lead halide single crystals CH3NH3PbX3 (X = I, Br, Cl) are interpreted with high level ab initio calculations using the relativistic quasiparticle self-consistent GW approximation (QSGW). Good agreement between the optical constants derived from QSGW and those obtained from spectroscopic ellipsometry enables the assignment of the spectral features to their respective inter-band transitions. We show that the transition from the highest valence band (VB) to the lowest conduction band (CB) is responsible for almost all the optical response of MAPbI3 between 1.2 and 5.5 eV (with minor contributions from the second highest VB and the second lowest CB). The calculations indicate that the orientation of [CH3NH3]+ cations has a significant influence on the position of the bandgap suggesting that collective

  6. Optical path switching based differential absorption radiometry for substance detection

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor)

    2003-01-01

    An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

  7. Optical path switching based differential absorption radiometry for substance detection

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor)

    2005-01-01

    An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

  8. Influence of laser radiation on induced absorption spectra of pure quartz glass optical fibers

    NASA Astrophysics Data System (ADS)

    Dianov, Y. M.; Karpechev, V. N.; Korniyenko, L. S.; Rybaltovskiy, A. O.; Chernov, P. V.

    1986-01-01

    The influence of laser radiation on radiation color centers and their associated induced absorption in the spectra of irradiated glass optical fibers is investigated. The glass fiber specimens employed had 40 to 50 micron diameter cores made of day pure quartz glass. The optical fibers were 6 to 20 meters long, produced by chemical precipitation from the gaseous phase and clad with reflecting borosilicate glass. Spectral measurements of the induced absorption in the ultraviolet region were made using an FEU-71 photodetector and a sounding radiation source. The stimulated laser emission power in the cross section of the optical fiber was measured by a photodiode; the absorption spectra were recorded by the fragment method. Eight different types of color centers were isolated whose bands cover practically the entire observed absorption spectra. The connection found between color centers and a 340 nm absorption band, and color center with absorption in the infrared band, indicate that absorption in the ultraviolet band can have a significant influence on the amount of induced absorption in the infrared band.

  9. Impact of intermediate localized states on nonlinear optical absorption of Ga-Ge-Se nanocolloidal solutions

    NASA Astrophysics Data System (ADS)

    Sebastian, Indu; Divya, S.; Nampoori, V. P. N.; Radhakrishnan, P.; Thomas, Sheenu

    2013-01-01

    We present the linear and nonlinear optical studies on nanocolloidal solutions of Ga9Ge27Se64 glass with varying concentrations. Optical bandgap of the material is found to vary with respect to the concentration of the solute in the solution. An intermediate peak in the band tail of the absorption spectra is observed due to the presence of energy band in the forbidden gap. The existence of fluorescence emission confirms the above argument. Nonlinear absorption is studied using open aperture Z-scan technique. The mechanism behind nonlinear absorption is predicted as two photon as well as two step photon absorption. Nonlinearity increases with decrease in optical bandgap which in turn depends on the concentration of the nanocolloidal solutions.

  10. Optical and Thermo-optical Properties of Polyimide-Single-Walled Carbon Nanotube Films: Experimental Results and Empirical Equations

    NASA Technical Reports Server (NTRS)

    Smith, Joseph G., Jr.; Connell, John W.; Watson, Kent A.; Danehy, Paul M.

    2005-01-01

    The incorporation of single-walled carbon nanotubes (SWNTs) into the bulk of space environmentally durable polymers at loading levels greater than or equal to 0.05 wt % has afforded thin films with surface and volume resistivities sufficient for electrostatic charge mitigation. However, the optical transparency at 500 nm decreased and the thermo-optical properties (solar absorptivity and thermal emissivity) increased with increaed SWNT loading. These properties were also dependent on film thickness. The absorbance characteristics of the films as a function of SWNT loading and film thickness were measured and determined to follow the classical Beer-Lambert law. Based on these results, an empirical relationship was derived and molar absorptivities determined for both the SWNTs and polymer matrix to provide a predictive approximation of these properties. The molar absorptivity determined for SWNTs dispersed in the polymer was comparable to reported solution determined values for HiPco SWNTs.

  11. Optical properties of a hurricane

    NASA Astrophysics Data System (ADS)

    Kokhanovsky, Alexander A.; von Hoyningen-Huene, W.

    2004-01-01

    This paper is devoted to study of the distribution of the reflection function, spherical albedo, and optical thickness for a hurricane Erin, located in the western Atlantic (39.3°N, 60.4°W) on September 13th, 2001(16:21 UTC). The limitations and possibilities of using SeaWiFS imagery for remote sensing of hurricanes are discussed. In particular, it is found that the mode of the hurricane spherical albedo spatial distribution is equal to 0.86 and the transport optical thickness is in the range 4-10 on average for the central core of a hurricane. A simple analytical method to derive the hurricane optical thickness distribution is proposed.

  12. Fabricating optical phantoms to simulate skin tissue properties and microvasculatures

    NASA Astrophysics Data System (ADS)

    Sheng, Shuwei; Wu, Qiang; Han, Yilin; Dong, Erbao; Xu, Ronald

    2015-03-01

    This paper introduces novel methods to fabricate optical phantoms that simulate the morphologic, optical, and microvascular characteristics of skin tissue. The multi-layer skin-simulating phantom was fabricated by a light-cured 3D printer that mixed and printed the colorless light-curable ink with the absorption and the scattering ingredients for the designated optical properties. The simulated microvascular network was fabricated by a soft lithography process to embed microchannels in polydimethylsiloxane (PDMS) phantoms. The phantoms also simulated vascular anomalies and hypoxia commonly observed in cancer. A dual-modal multispectral and laser speckle imaging system was used for oxygen and perfusion imaging of the tissue-simulating phantoms. The light-cured 3D printing technique and the soft lithography process may enable freeform fabrication of skin-simulating phantoms that embed microvessels for image and drug delivery applications.

  13. Electronic and optical properties of graphene nanoribbons in external fields.

    PubMed

    Chung, Hsien-Ching; Chang, Cheng-Peng; Lin, Chiun-Yan; Lin, Ming-Fa

    2016-03-01

    A review work is done for the electronic and optical properties of graphene nanoribbons in magnetic, electric, composite, and modulated fields. Effects due to the lateral confinement, curvature, stacking, non-uniform subsystems and hybrid structures are taken into account. The special electronic properties, induced by complex competitions between external fields and geometric structures, include many one-dimensional parabolic subbands, standing waves, peculiar edge-localized states, width- and field-dependent energy gaps, magnetic-quantized quasi-Landau levels, curvature-induced oscillating Landau subbands, crossings and anti-crossings of quasi-Landau levels, coexistence and combination of energy spectra in layered structures, and various peak structures in the density of states. There exist diverse absorption spectra and different selection rules, covering edge-dependent selection rules, magneto-optical selection rule, splitting of the Landau absorption peaks, intragroup and intergroup Landau transitions, as well as coexistence of monolayer-like and bilayer-like Landau absorption spectra. Detailed comparisons are made between the theoretical calculations and experimental measurements. The predicted results, the parabolic subbands, edge-localized states, gap opening and modulation, and spatial distribution of Landau subbands, have been identified by various experimental measurements. PMID:26744847

  14. Diffraction patterns and nonlinear optical properties of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Majles Ara, M. H.; Dehghani, Z.; Sahraei, R.; Daneshfar, A.; Javadi, Z.; Divsar, F.

    2012-03-01

    Stable gold nanoparticles have been prepared by using soluble starch as both the reducing and stabilizing agents; this reaction was carried out at 40 °C for 5 h. The obtained gold nanoparticles were characterized by UV-Vis absorption spectroscopy, transmission electron microscopy (TEM) and z-scan technique. The size of these nanoparticles was found to be in the range of 12-22 nm as analyzed using transmission electron micrographs. The optical properties of gold nanoparticles have been measured showing the surface plasmon resonance. The second-order nonlinear optical (NLO) properties were investigated by using a continuous-wave (CW) He-Ne laser beam with a wavelength of 632.8 nm at three different incident intensities by means of single beam techniques. The nonlinear refractive indices of gold nanoparticles were obtained from close aperture z-scan in order of 10-7 cm2/W. Then, they were compared with diffraction patterns observed in far-field. The nonlinear absorption of these nanoparticles was obtained from open aperture z-scan technique. The values of nonlinear absorption coefficient are obtained in order of 10-1 cm/W.

  15. Design of differential optical absorption spectroscopy long-path telescopes based on fiber optics.

    PubMed

    Merten, André; Tschritter, Jens; Platt, Ulrich

    2011-02-10

    We present a new design principle of telescopes for use in the spectral investigation of the atmosphere and the detection of atmospheric trace gases with the long-path differential optical absorption spectroscopy (DOAS) technique. A combination of emitting and receiving fibers in a single bundle replaces the commonly used coaxial-Newton-type combination of receiving and transmitting telescope. This very simplified setup offers a higher light throughput and simpler adjustment and allows smaller instruments, which are easier to handle and more portable. The higher transmittance was verified by ray-tracing calculations, which result in a theoretical factor threefold improvement in signal intensity compared with the old setup. In practice, due to the easier alignment and higher stability, up to factor of 10 higher signal intensities were found. In addition, the use of a fiber optic light source provides a better spectral characterization of the light source, which results in a lower detection limit for trace gases studied with this instrument. This new design will greatly enhance the usability and the range of applications of active DOAS instruments. PMID:21343997

  16. Generating Nanostructures with Multiphoton Absorption Polymerization using Optical Trap Assisted Nanopatterning

    NASA Astrophysics Data System (ADS)

    Tsai, Yu-Cheng; Leitz, Karl-Heinz; Fardel, Romain; Schmidt, Michael; Arnold, Craig B.

    The need to generate sub 100 nm features is of interest for a variety of applications including optics, optoelectronics, and plasmonics. To address this requirement, several advanced optical lithography techniques have been developed based on either multiphoton absorption polymerization or near-field effects. In this paper, we combine strengths from multiphoton absorption and near field using optical trap assisted nanopatterning (OTAN). A Gaussian beam is used to position a microsphere in a polymer precursor fluid near a substrate. An ultrafast laser is focused by that microsphere to induce multiphoton polymerization in the near field, leading additive direct-write nanoscale processing.

  17. Numerical study of optical absorption in two-dimensional metal-insulator and normal-superconductor composites

    SciTech Connect

    Zeng, X.C.; Hui, P.M.; Stroud, D.

    1989-01-15

    We analyze a random resistor-inductor-capacitor (RLC) lattice model for the optical properties of a two-dimensional normal-metal--insulator composite, using the Y-..delta.. transformation algorithm developed by Frank and Lobb. Within such a model, the surface plasmon resonances of a Drude-metal--insulator composite are modeled by the ac resonances of a random RLC network. The real part of the effective conductance is found to show a broad surface plasmon resonance peak below and above the metal percolation threshold, and a Drude peak above the threshold. An effective-medium-approximation (EMA) calculation is in excellent agreement with the results of the simulations. We also calculate the far-infrared absorption in a model composite of normal metal and superconductor, using a lattice model. The absorption shows a strong absorption below the superconducting energy gap. An approximate calculation based on the EMA is again in excellent agreement with these results.

  18. Luminescence and photoinduced absorption in ytterbium-doped optical fibres

    SciTech Connect

    Rybaltovsky, A A; Aleshkina, S S; Likhachev, M E; Bubnov, M M; Umnikov, A A; Yashkov, M V; Gur'yanov, Aleksei N; Dianov, Evgenii M

    2011-12-31

    Photochemical reactions induced in the glass network of an ytterbium-doped fibre core by IR laser pumping and UV irradiation have been investigated by analysing absorption and luminescence spectra. We have performed comparative studies of the photoinduced absorption and luminescence spectra of fibre preforms differing in core glass composition: Al{sub 2}O{sub 3} : SiO{sub 2}, Al{sub 2}O{sub 3} : Yb{sub 2}O{sub 3} : SiO{sub 2}, and P{sub 2}O{sub 5} : Yb{sub 2}O{sub 3} : SiO{sub 2}. The UV absorption spectra of unirradiated preform core samples show strong bands peaking at 5.1 and 6.5 eV, whose excitation plays a key role in photoinduced colour centre generation in the glass network. 'Direct' UV excitation of the 5.1- and 6.5-eV absorption bands at 244 and 193 nm leads to the reduction of some of the Yb{sup 3+} ions to Yb{sup 2+}. The photodarkening of ytterbium-doped fibres by IR pumping is shown to result from oxygen hole centre generation. A phenomenological model is proposed for the IR-pumping-induced photodarkening of ytterbium-doped fibres. The model predicts that colour centre generation in the core glass network and the associated absorption in the visible range result from a cooperative effect involving simultaneous excitation of a cluster composed of several closely spaced Yb{sup 3+} ions.

  19. Probing Interstellar Silicate Dust Grain Properties in Quasar Absorption Systems at Redshifts z<1.4

    NASA Astrophysics Data System (ADS)

    Aller, M.; Kulkarni, V. P.; York, D. G.; Welty, D. E.; Vladilo, G.; Som, D.

    indications of trends between silicate dust absorption strength and both carbonaceous dust properties and gas-phase metal properties, such as the gas velocity spread, determined from UV/optical spectra.

  20. Nonlinear optical properties of methyl red under CW irradiation

    NASA Astrophysics Data System (ADS)

    Zheng, Yu; Ye, Qing; Wang, Chen; Wang, Jin; Deng, Zhichao; Mei, Jianchun; Zhou, Wenyuan; Zhang, Chunping; Tian, Jianguo

    2015-12-01

    Organic materials have wide potential application in nonlinear optical devices. The nonlinear optical (NLO) properties of methyl red (MR) doped polymethyl methacrylate (MR-PMMA) are investigated under CW laser irradiation at 473 nm, 532 nm and 632.8 nm, respectively. By combining Kramers-Kronig (K-K) relation and CW Z-scan technique, the effective refractive index n2 and the change of refractive index Δn are obtained under different scanning speed at 473 nm and 532 nm. Δn is positive at 473 nm, while Δn is negative at 532 nm. The experimental result is consistent with that of K-K relation. With the scanning speed decreasing, the NLO properties of MR-PMMA are enhanced. With different laser powers at 632.8 nm, MR-PMMA has only nonlinear absorption rather than nonlinear refraction. Meanwhile, the sample is investigated under pulse laser irradiation at 532 nm. Through the comparison of results of CW Z-scan and pulse Z-scan, the influence of the cumulative thermal effect on NLO properties of material is investigated. The results indicate that, under CW irradiation near the absorption peak wavelength, the cumulative thermal effect has great influence to the NLO properties of MR-PMMA.

  1. Optical absorption enhancement of μc-SiGe:H films deposited via high pressure and high power

    NASA Astrophysics Data System (ADS)

    Li, Tian-wei; Zhang, Jian-jun; Cao, Yu; Huang, Zhen-hua; Ma, Jun; Ni, Jian; Zhao, Ying

    2014-05-01

    Hydrogenated microcrystalline silicon-germanium (μc-SiGe:H) films are fabricated by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). The optical absorption coefficient and the photosensitivity of the μc-SiGe:H films increase dramatically by increasing the plasma power and deposition pressure simultaneously. Additionally, the microstructural properties of the μc-SiGe:H films are also studied. By combining Raman, Fourier transform infrared (FTIR) and X-ray fluoroscopy (XRF) measurements, it is shown that the Ge-bonding configuration and compactability of the μc-SiGe:H thin films play a crucial role in enhancing the optical absorption and optimizing the quality of the films via a significant reduction in the defect density.

  2. The Optical Properties of Biological Tissue.

    NASA Astrophysics Data System (ADS)

    Bews, Jeffrey Alan

    The ability of light to propagate through biological tissue has found much application in medicine (ie. Photodynamic therapy and Diaphanography). However, a poor understanding of this transport phenomenon has served to limit the effectiveness of those modalities employing it in their operation. This thesis is a study of light propagation through biological tissue, its goal being to improve on the lack of knowledge that presently exists. A spectrophotometer type instrument (DICOM-8) was developed to measure the diffuse spectra extinction of biological tissue. Results were obtained for both normal and diseased breast tissue. Extinction curves for the two tissues exhibited a similar shape (extinction monotonically decreasing with increasing wavelength) but differed in magnitude below 700 nm with carcinoma possessing a higher extinction than normal. Data obtained from these tissue measurements served as the basis for developing a homogeneous liquid (TEM) for simulating the optical properties of tissue over the range 550 to 900 nm. Bench-top Diaphanography studies carried out on a breast phantom constructed of TEM demonstrated the improved tumor visualization attainable with short wavelength light. TEM also functioned as a test medium in which light distributions resulting from highly controlled irradiation geometries (isotropic point and planar sources) were measured and compared with those predicted by Linear Transport (LT) theory. The mean free path (MFP) of TEM ranged from 0.206 mm at 550 nm to 0.495 mm at 900 nm and was found to be directly proportional to the square of the wavelength. The scatter/absorption coefficient (c) was 0.9986459 at 550 nm and 0.9997315 at 850 nm. Agreement between experimental and theoretical distributions was found to be extremely good. Theoretical distributions generated with LT theory revealed the fact that small changes in MFP will have little effect on light transport. Similar changes in c, meanwhile, will drastically alter the

  3. A study of aerosol optical properties using a lightweight optical particle spectrometer and sun photometer from an unmanned aerial system

    NASA Astrophysics Data System (ADS)

    Telg, H.; Murphy, D. M.; Bates, T. S.; Johnson, J. E.; Gao, R. S.

    2015-12-01

    A miniaturized printed optical particle spectrometer (POPS) and sun photometer (miniSASP) have been developed recently for unmanned aerial systems (UAS) and balloon applications. Here we present the first scientific data recorded by the POPS and miniSASP from a Manta UAS during a field campaign on Svalbard, Norway, in April 2015. As part of a payload composed of five different aerosol instruments (absorption photometer, condensation particle counter, filter sampler, miniSASP and POPS) we collected particle size distributions, the optical depth (OD) and the sky brightness from 0 to 3000 m altitude. The complementary measurement approaches of the miniSASP and POPS allow us to calculate aerosol optical properties such as the aerosol optical depth and the angstrom exponent or the asymmetry parameter independently. We discuss deviation between results with respect to aerosol properties, e.g. hygroscopicity and absorption, as well as instrumental limitations.

  4. A One-Dimensional Solution of the Photoacoustic Wave Equation and its Relationship with Optical Absorption

    NASA Astrophysics Data System (ADS)

    Cywiak, D.; Barreiro-Argüelles, M. D.; Cywiak, M.; Landa-Curiel, A.; Garcia-Segundo, C.; Gutierrez-Juárez, G.

    2013-09-01

    A study based on the general solution of the one-dimensional photoacoustic (PA) wave equation for an acoustic plane source is presented. This study relies on obtaining the impulse response of the PA system considering a heating function proportional to the Lambert-Beer law and spatially bounded by a rectangle function. The PA pressure is obtained by convoluting the impulse response with the temporal profile of the exciting pulse of light. With the obtained solution, it is possible to comprise, on a single expression, the PA pressure profile for optically thin samples (whose dimensions are smaller than the optical absorption length) and optically opaque samples (whose dimensions are larger than the optical absorption length). In the limit of weak absorption, the solution is in good agreement with the one for a uniform distribution of energy. Also, a study of the dependence of the acoustic pressure with the duration of the laser pulse is included.

  5. Defects forming the optical absorption edge in TlGaSe2 layered crystal

    NASA Astrophysics Data System (ADS)

    Seyidov, MirHasan Yu.; Suleymanov, Rauf A.; Şale, Yasin

    2016-09-01

    In this work, we present the results of optical experiments designed to investigate the changes in optical absorption spectra of TlGaSe2 ferroelectric-semiconductor with incommensurate (INC) phase in experimental conditions where crystal is kept several hours within the INC-phase (the regime of so called "memory" effect). The fundamental absorption of TlGaSe2, experimentally investigated by optical transmission measurements performed in the temperature range 15-300 K. An extraordinary modification of the optical absorption edge in the range of Urbach's tail is discovered as a result of the annealing within the INC-phase. The role of native defects forming the band edge in the observed phenomena in TlGaSe2 is discussed.

  6. Remote sensing of optical properties in continuously stratified waters

    NASA Technical Reports Server (NTRS)

    Gordon, H. R.

    1978-01-01

    The radiative transfer equation is solved by Monte Carlo methods for natural waters in which the optical properties are distributed with depth. It is demonstrated that interpreting the reflectance of a continuously stratified ocean in terms of an equivalent homogeneous ocean yields the average of a particular combination of the water's optical properties over the dimensionless penetration depth. Although in general the dimensionless penetration depth cannot be remotely measured, a method is presented for estimating the actual penetration depth from the remote observations if the medium's absorption coefficient is known, independent of depth, and sufficiently large. The application of this to the remote measurement of the vertical distribution of suspended sediments is discussed in detail.

  7. Spatially resolved optical absorption spectroscopy of single- and few-layer MoS2 by hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Castellanos-Gomez, Andres; Quereda, Jorge; van der Meulen, Herko P.; Agraït, Nicolás; Rubio-Bollinger, Gabino

    2016-03-01

    The possibility of spatially resolving the optical properties of atomically thin materials is especially appealing as they can be modulated at the micro- and nanoscale by reducing their thickness, changing the doping level or applying a mechanical deformation. Therefore, optical spectroscopy techniques with high spatial resolution are necessary to get a deeper insight into the properties of two-dimensional (2D) materials. Here we study the optical absorption of single- and few-layer molybdenum disulfide (MoS2) in the spectral range from 1.24 eV to 3.22 eV (385 nm to 1000 nm) by developing a hyperspectral imaging technique that allows one to probe the optical properties with diffraction limited spatial resolution. We find hyperspectral imaging very suited to study indirect bandgap semiconductors, unlike photoluminescence which only provides high luminescence yield for direct gap semiconductors. Moreover, this work opens the door to study the spatial variation of the optical properties of other 2D systems, including non-semiconducting materials where scanning photoluminescence cannot be employed.

  8. Spatially resolved optical absorption spectroscopy of single- and few-layer MoS₂ by hyperspectral imaging.

    PubMed

    Castellanos-Gomez, Andres; Quereda, Jorge; van der Meulen, Herko P; Agraït, Nicolás; Rubio-Bollinger, Gabino

    2016-03-18

    The possibility of spatially resolving the optical properties of atomically thin materials is especially appealing as they can be modulated at the micro- and nanoscale by reducing their thickness, changing the doping level or applying a mechanical deformation. Therefore, optical spectroscopy techniques with high spatial resolution are necessary to get a deeper insight into the properties of two-dimensional (2D) materials. Here we study the optical absorption of single- and few-layer molybdenum disulfide (MoS2) in the spectral range from 1.24 eV to 3.22 eV (385 nm to 1000 nm) by developing a hyperspectral imaging technique that allows one to probe the optical properties with diffraction limited spatial resolution. We find hyperspectral imaging very suited to study indirect bandgap semiconductors, unlike photoluminescence which only provides high luminescence yield for direct gap semiconductors. Moreover, this work opens the door to study the spatial variation of the optical properties of other 2D systems, including non-semiconducting materials where scanning photoluminescence cannot be employed. PMID:26876671

  9. Nonlinear optical properties and optical power limiting effect of Giemsa dye

    NASA Astrophysics Data System (ADS)

    Al-Saidi, Imad Al-Deen Hussein A.; Abdulkareem, Saif Al-Deen

    2016-08-01

    The nonlinear optical properties of Giemsa dye in chloroform solution for different concentrations and dye mixed with poly(methylmethacrylate) (PMMA) as a dye-doped polymer film were investigated using continuous wave (CW) low power solid-state laser (SSL) operating at wavelength of 532 nm as an excitation source. Using the single beam z-scan technique, the nonlinear refractive index (n2), the nonlinear absorption coefficient (β), and the third-order nonlinear optical susceptibility (χ(3)) of Giemsa dye were measured. The measurements reveal that both n2 and β are dependent on the dye concentration. The obtained results indicate that the Giemsa dye exhibits positive nonlinear saturable absorption (SA) and negative refraction nonlinearity, manifestation of self-defocusing effect. Optical power limiting characteristics of the Giemsa dye at different concentrations in solution and polymer film were studied. The observed large third-order optical nonlinearity of Giemsa dye confirms that Giemsa dye is a promising nonlinear material for the optical power limiting and photonic devices applications.

  10. Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Liu, Qiang; Huang, Hong-Hua; Wang, Yao; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

    2014-06-01

    The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm-1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.

  11. Optical properties of actinide and lanthanide ions

    SciTech Connect

    Hessler, J.P.; Carnall, W.T.

    1980-01-01

    This paper reviews some of the recent developments in this area of spectroscopy, emphasizing the optical properties of the tripositive lanthanide and actinide ions. In particular, the single ion properties of line positon, intensity, width, and fluorescence lifetime are discussed. 53 reference, 3 figures, 4 tables.

  12. Organic Aerosols from SÃO Paulo and its Relationship with Aerosol Absorption and Scattering Properties

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Brito, J. F.; Rizzo, L. V.

    2012-12-01

    The megacity of São Paulo with its 19 million people and 7 million cars is a challenge from the point of view of air pollution. High levels of organic aerosols, PM10, black carbon and ozone and the peculiar situation of the large scale use of ethanol fuel makes it a special case. Little is known about the impact of ethanol on air quality and human health and the increase of ethanol as vehicle fuel is rising worldwide An experiment was designed to physico-chemical properties of aerosols in São Paulo, as well as their optical properties. Aerosol size distribution in the size range of 1nm to 10 micrometers is being measured with a Helsinki University SMPS (Scanning Mobility Particle Sizer), an NAIS (Neutral ion Spectrometer) and a GRIMM OPC (Optical Particle Counter). Optical properties are being measured with a TSI Nephelometer and a Thermo MAAP (Multi Angle Absorption Photometer). A CIMEL sunphotometer from the AERONET network measure the aerosol optical depth. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to real-time VOC analysis and aerosol composition, respectively. The ACSM was operated for 3 months continuosly during teh wintertime of 2012. The measured total particle concentration typically varies between 10,000 and 30,000 cm-3 being the lowest late in the night and highest around noon and frequently exceeding 50,000 cm-3. Clear diurnal patterns in aerosol optical properties were observed. Scattering and absorption coefficients typically range between 20 and 100 Mm-1 at 450 nm, and between 10 to 40 Mm-1 at 637 nm, respectively, both of them peaking at 7:00 local time, the morning rush hour. The corresponding single scattering albedo varies between 0.50 and 0.85, indicating a significant contribution of primary absorbing particles to the aerosol population. During the first month a total of seven new particle formation events were observed with growth rates ranging from 9 to 25

  13. Optical properties of laser spinel

    NASA Astrophysics Data System (ADS)

    Mironova-Ulmane, Nina; Skvortsova, Vera; Smirnovs, Andrejs; Riekstinya, Daina; Litvinov, L.; Sildos, Ilmo; Osvet, Andris

    1997-02-01

    The present work summarizes the results of absorption and luminescence spectra investigation of natural and synthetic magnesium aluminum spinels (MgO*nAl2O3) containing chromium and manganese ions. The spectra have been analyzed with an aim to determine the effect of stoichiometry 'n' on distribution of emitting ions. The Mn2+ is observed in both tetrahedral and octahedral coordinations providing green or orange emission. Absorption bands have been explained in terms of the Mn2+ configuration model. Laser excitation of chromium-comprising magnesium aluminum spinel crystals has been carried out at 7 K with the purpose to detect the nearest neighbors of Cr3+ ions. Luminescence emission spectra have been obtained for natural sample and three synthetic samples (MgO*nAl2O3, n equals 1, 2, 2.8). Decay time has been measured at different wavelengths and compared for crystals of different stoichiometry. In case n equals 2 or 2.8, computer simulation has been used to decompose smeared luminescence spectra in the 680 - 700 nm region. Gaussian curves corresponding to R- and N-lines of natural spinel spectrum have been applied as components in the calculations of nonstoichiometric spinel spectra. This suggests that there aren't normally arranged Cr-occupied octahedral positions in nonstoichiometric spinel (n equals 2.8, e.g.).

  14. Measurement of bidirectional optical properties of complex shading devices

    SciTech Connect

    Klems, J.H.; Warner, J.L.

    1995-01-01

    A new method of predicting the solar heat gain through complex fenestration systems involving nonspecular layers such as shades or blinds has been examined in a project jointly sponsored by ASHRAE and DOE. In this method, a scanning radiometer is used to measure the bidirectional radiative transmittance and reflectance of each layer of a fenestration system. The properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation. The calculation produces the total directional-hemispherical transmittance of the fenestration system and the layer-by-layer absorptances. These properties are in turn combined with layer-specific measurements of the inward-flowing fractions of absorbed solar energy to produce the overall solar heat gain coefficient. This paper describes the method of measuring the spatially averaged bidirectional optical properties using an automated, large-sample gonioradiometer/photometer, termed a ``Scanning Radiometer.`` Property measurements are presented for one of the most optically complex systems in common use, a venetian blind. These measurements will form the basis for optical system calculations used to test the method of determining performance.

  15. Optical absorption of gamma-irradiated lithium-borate glasses doped with different transition metal oxides

    NASA Astrophysics Data System (ADS)

    Marzouk, S. Y.; Elalaily, N. A.; Ezz-Eldin, F. M.; Abd-Allah, W. M.

    2006-06-01

    We have investigated the effect of gamma irradiation on the optical properties of Li 2O-B 2O 3 containing two concentrations (0.2 or 0.5 g) of each one of the following transition metals, V, Mn, Fe or Ni oxide glass samples. We studied the impacts of gamma irradiation in terms of the mechanism by which radiation-induced defects are generated. A resolution of the observed absorption spectra showed several bands which were induced by photo-reduction or photo-oxidation assumed to take place by photo-chemical reaction according to the type of transition metal oxide (TMO). Small deviations of these induced bands characteristic of the glass constituents were observed and explained in terms of the physical properties, in relation to different oxidation states of TMO in the glass matrix. The series Mn 2+, Fe 2+ and Ni 2+ ions shows a trend of increased photo-oxidation with increasing electronegativity or decreasing mass of the ions. The prepared samples were studied in terms of their dosimetric characteristics: calibration curves from 1.0524 to 42.096 kGy and fading at (25 and 50 °C). Thermal bleaching of irradiated glass was found to permit the reduction of the larger part of TMO ions in Li 2O-B 2O 3. Also, the results showed that the degeneration of the induced bands was faster at 50 than at 25 °C. The optical energy gap Eg was found to decrease with the increase of the radiation dose, and it is suggested that the mechanism of optical transition is forbidden by indirect transition.

  16. The Importance of Optical Pathlength Control for Plasma Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.; Rao, M. V. V. S.; Sharma, Surendra P.; Meyyappan, M.; Partridge, Harry (Technical Monitor)

    2001-01-01

    An inductively coupled GEC Cell with modified viewing ports has been used to measure in-situ absorption in CF4 plasmas via Fourier Transform Infrared Spectroscopy, and the results compared to those obtained in a standard viewport configuration. The viewing ports were modified so that the window boundary is inside, rather than outside, of the GEC cell. Because the absorption obtained is a spatially integrated absorption, measurements made represent an averaging of absorbing species inside and outside of the plasma. This modification is made to reduce this spatial averaging and thus allow a more accurate estimation of neutral species concentrations and temperatures within the plasmas. By reducing this pathlength, we find that the apparent CF4 consumption increases from 65% to 95% and the apparent vibrational temperature of CF4 rises by 50-75 K. The apparent fraction of etch product SiF4 decreases from 4% to 2%. The data suggests that these density changes may be due to significant temperature gradients between the plasma and chamber viewports.

  17. Magneto-optical transport properties of monolayer WSe2

    NASA Astrophysics Data System (ADS)

    Tahir, M.; Vasilopoulos, P.

    2016-07-01

    The recent experimental realization of a high quality WSe2 leads to the possibility of magneto-optical measurements and the manipulation of the spin and valley degrees of freedom. We study the influence of the very strong spin-orbit coupling and of the anisotropic lifting of the valley pseudospin degeneracy on its magnetotransport properties. The energy spectrum of WSe2 is derived and discussed in the presence of a perpendicular magnetic field B . Correspondingly we evaluate the magneto-optical Hall conductivity and the optical longitudinal conductivity as functions of the frequency, magnetic field, and Fermi energy. They are strongly influenced by the field B and the strong spin splitting. The former exhibits valley polarization and the latter beatings of oscillations. The magneto-optical responses can be tuned in two different regimes: the microwave-to-terahertz regime and the visible-frequency one. The absorption peaks involving the n =0 LL appear in between these two regimes and show a magnetic control of the spin and valley splittings. We also evaluate the power absorption spectrum.

  18. Thermo-optical properties of gold nanoparticles in colloidal systems

    NASA Astrophysics Data System (ADS)

    Ortega, M. A.; Rodriguez, L.; Castillo, J.; Piscitelli, V.; Fernandez, A.; Echevarria, L.

    2008-10-01

    In this work, we report the thermo-optical properties of nanoparticles in colloidal suspensions. Spherical gold nanoparticles obtained by laser ablation in condensed media were characterized using thermal lens spectroscopy pumping at 532 nm with a 10 ns pulse laser-Nd-YAG system. The obtained nanoparticles were stabilized in the time by surfactants (sodium dodecyl sulfate or SDS) in water with different molar concentrations. The morphology and size of the gold nanoparticles were determined by transmission electron microscopy (TEM) and UV-visible techniques. The plasmonic resonance bands in gold nanoparticles are responsible for the light optical absorption, and the positions of the absorption maximum and bandwidth in the UV-visible spectra are given by the morphological characteristics of these systems. The thermo-optical constants such as thermal diffusion, thermal diffusivity, and (dn/dT) are functions of the nanoparticle sizes and the dielectric function of the media. For these reasons, the thermal lens (TL) signal is also dependent on nanoparticle sizes. An analysis of the TL signal of the nanoparticles reveals the existence of an inverse dependence between the thermo-optical functions and the size. This methodology can be used in order to evaluate these systems and characterize nanoparticles in different media. These results are expected to have an impact in bioimaging, biosensors, and other technological applications such as cooling systems.

  19. Absorption properties of micellar lipid metabolites into Caco2 cells.

    PubMed

    Tsuzuki, Wakako

    2007-07-01

    To elucidate the absorption characteristics of dietary lipids in the human intestine, we investigated the cellular uptake of lipid metabolites using a differential monolayer of the Caco2 cells. As lipid metabolites, several free fatty acids and 2-monoacylglycerols, were formed a mixed micelle by bile salts and lysophospholipids and they were supplied to the Caco2 cells. To estimate the effect of the mixed micelles on the permeability of cells' membranes during incubation with the mixed micelles, the transepitherial electrical resistance (TEER) value was monitored, and no pronounced changes of TEER was detected. This suggested that mixed micelles did not affect their cellular properties of the barrier measured by TEER. The lipid metabolites transferred from the mixed micelle into the Caco2 cells were determined quantitatively by an enzymatic colorimetric method and were done by thin layer chromatography (TLC) for a species of acylglycerols. These highly sensitive methods enabled us to monitor the transepithelial transports of various kinds of non-isotope-labeled various lipid metabolites. Newly re-synthesized triacylglycerols were accumulated in Caco2 cells after 30 min incubation with the mixed micelles, and their amounts increased gradually for 4 h. The secretion of re-esterified triacylglycerols into a basolateral medium from the Caco2 cells began at 2 h after the mixed micelles were added to the apical medium. The intake of external lipid metabolites by the Caco2 cells were evaluated by an initial 2-h incubation with the mixed micelles. For example, 2-monomyristin and 2-monopalmitin were more rapidly transferred into the Caco2 cells from the mixed micelles than 2-monocaprin was. On the other hand, the absorption rates of capric acid, lauric acid and myristic acid by the cells were larger than those of stearic acid and oleic acid. It revealed that the side-chain structure of these lipid metabolites affected their absorption by the Caco2 cells. The results of this

  20. Optical Properties of Bismuth Germanate (BGO)

    SciTech Connect

    Jellison Jr, Gerald Earle; Auluck, S.; Singh, David J; Boatner, Lynn A

    2010-01-01

    The optical dielectric function of bismuth germanate Bi4Ge3O12 has been measured using spectroscopic ellipsometry and optical transmission. Analysis near the direct band edge indicates that there are at least three critical points at 4.44 low intensity and at 4.75 and 4.91 high intensity. Using transmission measurements, the band gap is determined to be 4.20 eV, which is likely determined by the defects in the material. Comparisons are made with relativistic electronic structure and optical calculations based on the Engel Vosko generalized gradient approximation. The near-absorption-edge critical points are associated with spin-orbit-split bands which significantly modify the conduction bands.

  1. An organic dye-polymer (phenol red-poly (vinyl alcohol)) composite architecture towards tunable -optical and -saturable absorption characteristics

    NASA Astrophysics Data System (ADS)

    Sreedhar, Sreeja; Illyaskutty, Navas; Sreedhanya, S.; Philip, Reji; Muneera, C. I.

    2016-05-01

    Herein, we demonstrate that blending an organic dye (guest/filler), with a vinyl polymer (host template), is an inexpensive and simple approach for the fabrication of multifunctional photonic materials which could display an enhancement in the desirable properties of the constituent materials and, at the same time provide novel synergistic properties for the guest-host system. A new guest-host nanocomposite system comprising Phenol Red dye and poly (vinyl alcohol) as guest and host template, respectively, which exhibits tunable optical characteristics and saturable absorption behavior, is introduced. The dependence of local electronic environment provided by the polymer template and the interactions of the polymer molecules with the encapsulated guest molecules on the observed optical/nonlinear absorption behavior is discussed. An understanding of the tunability of the optical/ photophysical processes, with respect to the filler content, as discussed herein could help in the design of improved optical materials for several photonic device applications like organic light emitting diodes and saturable absorbers.

  2. Quantum Plasmonics: Optical Properties and Tunability of Metallic Nanorods

    SciTech Connect

    Zuloaga, Jorge; Prodan, Emil; Nordlander, Peter

    2010-09-28

    The plasmon resonances in metallic nanorods are investigated using fully quantum mechanical time-dependent density functional theory. The computed optical absorption curves display well-defined longitudinal and transverse plasmon resonances whose energies depend on the aspect ratio of the rods, in excellent agreement with classical electromagnetic modeling. The field enhancements obtained from the quantum mechanical calculations, however, differ significantly from classical predictions for distances shorter than 0.5 nm from the nanoparticle surfaces. These deviations can be understood as arising from the nonlocal screening properties of the conduction electrons at the nanoparticle surface.

  3. Development of graphene oxide materials with controllably modified optical properties

    NASA Astrophysics Data System (ADS)

    Naumov, Anton; Galande, Charudatta; Mohite, Aditya; Ajayan, Pulickel; Weisman, R. Bruce

    2015-03-01

    One of the major current goals in graphene research is modifying its optical and electronic properties through controllable generation of band gaps. To achieve this, we have studied the changes in optical properties of reduced graphene oxide (RGO) in water suspension upon the exposure to ozone. Ozonation for the periods of 5 to 35 minutes has caused a dramatic bleaching of its absorption and the concurrent appearance of strong visible fluorescence in previously nonemissive samples. These observed spectral changes suggest a functionalization-induced band gap opening. The sample fluorescence induced by ozonation was found to be highly pH-dependent: sharp and structured emission features resembling the spectra of molecular fluorophores were present at basic pH values, but this emission reversibly broadened and red-shifted in acidic conditions. These findings are consistent with excited state protonation of the emitting species in acidic media. Oxygen-containing addends resulting from the ozonation were detected by XPS and FTIR spectroscopy and related to optical transitions in localized graphene oxide fluorophores by computational modeling. Further research will be directed toward producing graphene-based optoelectronic devices with tailored and controllable optical properties.

  4. Asymmetric effects on the optical properties of double-quantum well systems

    NASA Astrophysics Data System (ADS)

    Silotia, Poonam; Batra, Kriti; Prasad, Vinod

    2014-02-01

    Linear, nonlinear, and total absorption coefficient and refractive index changes of double-quantum well (DQW) systems are studied theoretically in the presence of external static electric field applied along the growth direction. The analytical expression for the linear and nonlinear optical properties is obtained using density matrix method. Emphasis is laid on the effect of asymmetry in the shapes of DQW system on optical properties. Some interesting results are obtained and explained.

  5. Selectivity of the optical-absorption method based on an instrumental pick out of Fourier components in the absorption spectrum

    NASA Astrophysics Data System (ADS)

    Pisarevsky, Yu. V.; Kolesnikov, S. A.; Kolesnikova, E. S.; Turutin, Yu. A.; Konopelko, L. A.; Shor, N. B.

    2016-06-01

    The introduction of interference-polarization filters (IPFs) in the structure of an optical-absorption analyzer makes it possible to pick out a harmonic (a Fourier component of the absorption spectrum) providing measurement with the highest sensitivity. The selectivity of such a method of analysis is determined by overlapping the oscillations of the measured and interfering components. By the example of measurement in benzene in the presence of an interfering component (toluene), the possibility is considered for the optimization of selectivity due to the variation of the path-difference dispersion for ordinary and extraordinary interfering rays. The metrological characteristics of the interference-polarization analyzer of C6H6 confirming the results of calculations are given.

  6. Optical properties of mice skin for optical therapy relevant wavelengths: influence of gender and pigmentation

    NASA Astrophysics Data System (ADS)

    Sabino, C. P.; Deana, A. M.; Silva, D. F. T.; França, C. M.; Yoshimura, T. M.; Ribeiro, M. S.

    2015-03-01

    Red and near-infrared light have been widely employed in optical therapies. Skin is the most common optical barrier in non-invasive techniques and in many cases it is the target tissue itself. Consequently, to optimize the outcomes brought by lightbased therapies, the optical properties of skin tissue must be very well elucidated. In the present study, we evaluated the dorsal skin optical properties of albino (BALB/c) and pigmented (C57BL/6) mice using the Kubelka-Munk photon transport model. We evaluated samples from male and female young mice of both strains. Analysis was performed for wavelengths at 630, 660, 780, 810 and 905 nm due to their prevalent use in optical therapies, such as low-level light (or laser) and photodynamic therapies. Spectrophotometric measurements of diffuse transmittance and reflectance were performed using a single integrating sphere coupled to a proper spectrophotometer. Statistic analysis was made by two-way ANOVA, with Tukey as post-test and Levenne and Shapiro-Wilks as pre-tests. Statistical significance was considered when p<0.05. Our results show only a slight transmittance increment (<10 %) as wavelengths are increased from 630 to 905 nm, and no statistical significance was observed. Albino male mice present reduced transmittance levels for all wavelengths. The organization and abundance of skin composing tissues significantly influence its scattering optical properties although absorption remains constant. We conclude that factors such as subcutaneous adiposity and connective tissue structure can have statistically significant influence on mice skin optical properties and these factors have relevant variations among different gender and strains.

  7. Electrical and optical properties of carbon films

    NASA Astrophysics Data System (ADS)

    Kulkarni, Pranita

    Carbon and carbon-based materials, including graphite, diamond, and other thin-film structures, are being intensively researched for a wide range of electronic applications. A variety of graphitic, nano-structured carbon materials can be synthesized that have current or potential applications as thin-film transistors, photovoltaics, and supercapacitors. Diamond has been pursued for many years for electronics that can be used in extreme conditions, such as high temperature, high power, high frequency, and radiation environments. In this research study, electronic properties of diamond and graphitic films with crystallite or grain sizes in the nanometer range were investigated. The nano-structured graphitic carbon films were grown using a previously developed method based on the pyrolysis of poly(acrylonitrile) and poly(n-butyl acrylate) block copolymers (PAN-b-PBA). An important characteristic of these films is that the morphology (and therefore other properties) can be controlled by the compositions and processing of the starting block copolymers. Spherical, cylindrical, lamellar, and branched morphologies have been fabricated. The crystallite sizes, optical absorption, and morphology of PAN-b-PBA (containing 17.8% PAN) pyrolyzed between 400 and 600°C were determined and were compared to those derived by pyrolysis of PAN homopolymers at the same temperatures. Hall-effect measurements on pyrolyzed PAN-b-PBA films with spherical, cylindrical, and branched morphologies and homopolymer PAN films pyrolyzed at the same temperatures revealed that both PAN-b-PBA with different morphologies and PAN homopolymer-derived films had n-type conductivity; differences in carrier concentration and mobility values were correlated with the morphological differences of the films. Optical absorption measurements in the ultra-violet through visible wavelength range were also conducted on these films; measurements of the pseudo band-gaps and absorption coefficients were correlated with

  8. Subwavelength-resolution photoacoustic microscopy for label-free detection of optical absorption in vivo

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Maslov, Konstantin; Wang, Lihong V.

    2011-03-01

    Mainstream optical microscopy technologies normally detect fluorescence or scattering, which may require undesirable labeling, but cannot directly sense optical absorption, which provides essential biological functional information. Here we reported in vivo and label-free subwavelength-resolution photoacoustic microscopy (SW-PAM) by using a waterimmersion optical objective with a 1.23 NA. Capable of detecting nonfluorescent endogenous pigments, SW-PAM provides exquisitely high optical-absorption contrast. And, as a result of background-free detection, the sensitivity of SW-PAM to optical absorption reaches 100%. SW-PAM was demonstrated with wide-field optical microscopy by imaging gold nanospheres, ex vivo cells, and in vivo vasculature and melanoma. It was shown that SW-PAM has approached the ultimate diffraction-limited optical resolution-220 nm resolution at 532 nm wavelength. Subcellular organelles, such as melanosomes, can be resolved by SW-PAM. Vasculature and early-stage melanoma were imaged with 21:1 and 34:1 contrasts, respectively, without labeling. For all these applications, SW-PAM has contrasts orders of magnitude higher than wide-field optical microscopy. Therefore, SW-PAM is expected to join the mainstream microscopy technologies.

  9. Optical Property Analyses of Plant Cells for Adaptive Optics Microscopy

    NASA Astrophysics Data System (ADS)

    Tamada, Yosuke; Murata, Takashi; Hattori, Masayuki; Oya, Shin; Hayano, Yutaka; Kamei, Yasuhiro; Hasebe, Mitsuyasu

    2014-04-01

    In astronomy, adaptive optics (AO) can be used to cancel aberrations caused by atmospheric turbulence and to perform diffraction-limited observation of astronomical objects from the ground. AO can also be applied to microscopy, to cancel aberrations caused by cellular structures and to perform high-resolution live imaging. As a step toward the application of AO to microscopy, here we analyzed the optical properties of plant cells. We used leaves of the moss Physcomitrella patens, which have a single layer of cells and are thus suitable for optical analysis. Observation of the cells with bright field and phase contrast microscopy, and image degradation analysis using fluorescent beads demonstrated that chloroplasts provide the main source of optical degradations. Unexpectedly, the cell wall, which was thought to be a major obstacle, has only a minor effect. Such information provides the basis for the application of AO to microscopy for the observation of plant cells.

  10. Optical Properties of Multi-Layered Insulation

    NASA Astrophysics Data System (ADS)

    Rodriguez, H.; Abercromby, K.; Mulrooney, M.; Barker, E.

    spectral measurements were acquired for each MLI sample. Spectral data will be combined to match the wavelength region of photometric data to establish a fiduciary reference for the photometric measurements. Not only will this help validate the color photometry, but it will also assist interpretation and analysis of telescopic data. As an example, copper-colored Kapton shows a strong absorption feature near 4800 angstroms. If the observed debris is MLI and the outer layer of copper coloring of Kapton is present, evidence of this material should be seen spectroscopically by the specific absorption feature as well as photometrically (eg. by using R-B (red-blue) light curves). Using laboratory photometric and spectroscopic measurements an optical property database is provided for a representative high A/m object. These results should directly aid the accurate interpretation of telescopically acquired optical orbital debris photometry of both high A/m targets as well as satellites and spacecraft that incorporate MLI.

  11. Experimental and theoretical optical properties of methylammonium lead halide perovskites.

    PubMed

    Leguy, Aurélien M A; Azarhoosh, Pooya; Alonso, M Isabel; Campoy-Quiles, Mariano; Weber, Oliver J; Yao, Jizhong; Bryant, Daniel; Weller, Mark T; Nelson, Jenny; Walsh, Aron; van Schilfgaarde, Mark; Barnes, Piers R F

    2016-03-17

    The optical constants of methylammonium lead halide single crystals CH3NH3PbX3 (X = I, Br, Cl) are interpreted with high level ab initio calculations using the relativistic quasiparticle self-consistent GW approximation (QSGW). Good agreement between the optical constants derived from QSGW and those obtained from spectroscopic ellipsometry enables the assignment of the spectral features to their respective inter-band transitions. We show that the transition from the highest valence band (VB) to the lowest conduction band (CB) is responsible for almost all the optical response of MAPbI3 between 1.2 and 5.5 eV (with minor contributions from the second highest VB and the second lowest CB). The calculations indicate that the orientation of [CH3NH3](+) cations has a significant influence on the position of the bandgap suggesting that collective orientation of the organic moieties could result in significant local variations of the optical properties. The optical constants and energy band diagram of CH3NH3PbI3 are then used to simulate the contributions from different optical transitions to a typical transient absorption spectrum (TAS). PMID:26477295

  12. Theoretical prediction of optical absorption maxima for photosensory receptor mutants

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Kazutomo; Yamato, Takahisa

    2006-10-01

    We found a linear correlation between the theoretically predicted shifts and experimentally observed absorption spectra for various mutants of photoactive yellow protein, a photosensory receptor. Excitation energies of mutants were evaluated by the combination of the high level ab initio calculation for the chromophore inside and the low level ab initio calculation for the surrounding protein environment. Importantly, the electronic states of these two regions were treated both as variables and they are solved consistently to each other. The protein-chromophore interaction has been accurately reproduced by this method.

  13. Optical properties of a scorpion (Centruroides limpidus)

    NASA Astrophysics Data System (ADS)

    Ullrich, Bruno; Duckworth, Robyn M.; Singh, Akhilesh K.; Barik, Puspendu; Mejía-Villanueva, Vicente O.; Garcia-Pérez, Alberto C.

    2016-04-01

    Scorpions, elusive by nature, tend to appear nocturnally and are usually not appreciated when encountered. The exoskeleton is capable of fluorescing allowing for their detection at night in order to prevent undesirable encounters. The specificity of their fluorescing suggests specialized optical features. However, despite the blue-green fluorescence, to the best of our knowledge, no further results have been published on the optical properties of scorpions. Their exoskeletal structure whose versatility provides them protection, camouflage, and flexibility has not been studied under laser excitation and monochromatic light. The experiments reveal the nonlinear optical properties, infrared photoluminescence, and photoconductivity of the epicuticle of scorpions, demonstrating that the scorpion’s outer-covering is a prototype of a semiconducting inherently integrated multifunctional polymeric film with appealing potential applications such as optical logics, photonic frequency converters, novel multiplexers handling electronic and photonic inputs, and lasers.

  14. Optical properties of CuS nanoparticles at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Yang, Y. P.; Zhang, Z. W.; Feng, S.; Chen, X.; Wang, Y. Q.; Wang, W. Z.

    2010-11-01

    The low-frequency optical properties of CuS nanoparticles in the composite samples were measured by the terahertz time-domain spectroscopy. Then, the power absorption, refractive index, complex dielectric function and conductivity of pure CuS nanoparticles are extracted by applying Bruggeman effective medium theory. The measured dielectric function and conductivity are consistent with the Lorentz theory of dielectric response as well as the Drude-smith model of conductivity in the frequency range from 0.2 to 1.5 THz, respectively. In addition, the extrapolation of the measured data indicates that the absorption is dominated by the lattice vibration localized at 4.7 +/- 0.2 THz and the time constant for the carrier scattering is only 64.3 fs due to increased electron interaction with interfaces and grain boundaries.

  15. Confined optical-phonon-assisted cyclotron resonance in quantum wells via two-photon absorption process

    NASA Astrophysics Data System (ADS)

    Phuc, Huynh Vinh; Hien, Nguyen Dinh; Dinh, Le; Phong, Tran Cong

    2016-06-01

    The effect of confined phonons on the phonon-assisted cyclotron resonance (PACR) via both one and two photon absorption processes in a quantum well is theoretically studied. We consider cases when electrons are scattered by confined optical phonons described by the Fuchs-Kliewer slab, Ridley's guided, and Huang-Zhu models. The analytical expression of the magneto-optical absorption coefficient (MOAC) is obtained by relating it to the transition probability for the absorption of photons. It predicts resonant peaks caused by transitions between Landau levels and electric subband accompanied by confined phonons emission in the absorption spectrum. The MOAC and the full-width at half-maximum (FWHM) for the intra- and inter-subband transitions are given as functions of the magnetic field, temperature, and quantum well width. In narrow quantum wells, the phonon confinement becomes more important and should be taken into account in studying FWHM.

  16. Magnetic field control of the intraband optical absorption in two-dimensional quantum rings

    SciTech Connect

    Olendski, O.; Barakat, T.

    2014-02-28

    Linear and nonlinear optical absorption coefficients of the two-dimensional semiconductor ring in the perpendicular magnetic field B are calculated within independent electron approximation. Characteristic feature of the energy spectrum are crossings of the levels with adjacent nonpositive magnetic quantum numbers as the intensity B changes. It is shown that the absorption coefficient of the associated optical transition is drastically decreased at the fields corresponding to the crossing. Proposed model of the Volcano disc allows to get simple mathematical analytical results, which provide clear physical interpretation. An interplay between positive linear and intensity-dependent negative cubic absorption coefficients is discussed; in particular, critical light intensity at which additional resonances appear in the total absorption dependence on the light frequency is calculated as a function of the magnetic field and levels' broadening.

  17. Tailoring the Spectroscopic Properties of Semiconductor Nanowires via Surface-Plasmon-Based Optical Engineering

    PubMed Central

    2014-01-01

    Semiconductor nanowires, due to their unique electronic, optical, and chemical properties, are firmly placed at the forefront of nanotechnology research. The rich physics of semiconductor nanowire optics arises due to the enhanced light–matter interactions at the nanoscale and coupling of optical modes to electronic resonances. Furthermore, confinement of light can be taken to new extremes via coupling to the surface plasmon modes of metal nanostructures integrated with nanowires, leading to interesting physical phenomena. This Perspective will examine how the optical properties of semiconductor nanowires can be altered via their integration with highly confined plasmonic nanocavities that have resulted in properties such as orders of magnitude faster and more efficient light emission and lasing. The use of plasmonic nanocavities for tailored optical absorption will also be discussed in order to understand and engineer fundamental optical properties of these hybrid systems along with their potential for novel applications, which may not be possible with purely dielectric cavities. PMID:25396030

  18. A method for determination of the absorption and scattering properties interstitially in turbid media.

    PubMed

    Dimofte, Andreea; Finlay, Jarod C; Zhu, Timothy C

    2005-05-21

    We have developed a method to quickly determine tissue optical properties (absorption coefficient mu(a) and transport scattering coefficient mu'(s)) by measuring the ratio of light fluence rate to source power along a linear channel at a fixed distance (5 mm) from an isotropic point source. Diffuse light is collected by an isotropic detector whose position is determined by a computer-controlled step motor, with a positioning accuracy of better than 0.1 mm. The system automatically records and plots the light fluence rate per unit source power as a function of position. The result is fitted with a diffusion equation to determine mu(a) and mu'(s). We use an integrating sphere to calibrate each source-detector pair, thus reducing uncertainty of individual calibrations. To test the ability of this algorithm to accurately recover the optical properties of the tissue, we made measurements in tissue simulating phantoms consisting of Liposyn at concentrations of 0.23, 0.53 and 1.14% (mu'(s) = 1.7-9.1 cm(-1)) in the presence of Higgins black India ink at concentrations of 0.002, 0.012 and 0.023% (mu(a) = 0.1-1 cm(-1)). For comparison, the optical properties of each phantom are determined independently using broad-beam illumination. We find that mu(a) and mu'(s) can be determined by this method with a standard (maximum) deviation of 8% (15%) and 18% (32%) for mu(a) and mu'(s), respectively. The current method is effective for samples whose optical properties satisfy the requirement of the diffusion approximation. The error caused by the air cavity introduced by the catheter is small, except when mu(a) is large (mu(a) > 1 cm(-1)). We presented in vivo data measured in human prostate using this method. PMID:15876668

  19. Bio-optical properties of oceanic waters: A reappraisal

    NASA Astrophysics Data System (ADS)

    Morel, André; Maritorena, StéPhane

    2001-04-01

    The apparent optical properties (AOPs) of oceanic case 1 waters were previously analyzed [Morel, 1988] and statistically related to the chlorophyll concentration ([Chl]) used as a global index describing the trophic conditions of water bodies. From these empirical relationships a bio-optical model of the upper layer was developed. With objectives and structure similar to those of the previous study the present reappraisal utilizes AOPs determined during recent Joint Global Ocean Flux Study cruises, namely, spectral attenuation for downward irradiance Kd(λ) and irradiance reflectance R(λ). This revision also benefits from improved knowledge of inherent optical properties (IOPs), namely, pure water absorption coefficients and particle scattering and absorption coefficients, and from better pigment quantification (via a systematic use of high-performance liquid chromatography). Nonlinear trends, already observed between optical properties and algal biomass, are fully confirmed, yet with numerical differences. The previous Kd(λ) model, and subsequently the R(λ) model, is modified to account for these new relationships. The R(λ) values predicted as a function of [Chl] and the predicted ratios of reflectances at two wavelengths, which are commonly used in ocean color algorithms, compare well with field values (not used when developing the reflectance model). This good agreement means that semianalytical ocean color algorithms can be successfully applied to satellite data. Going further into purely analytical approaches, ideally based on radiative transfer computations combined with a suite of relationships between the IOPs and [Chl], remains presently problematic, especially because of the insufficient knowledge of the phase function and backscattering efficiency of oceanic particles.

  20. Electronic and optical properties of novel carbon allotropes

    DOE PAGESBeta

    Wang, Zhanyu; Dong, F.; Shen, B.; Zhang, R. J.; Zheng, Y. X.; Chen, L. Y.; Wang, S. Y.; Wang, C. Z.; Ho, K. M.; Fan, Yuan -Jia; et al

    2016-01-22

    The vibrational properties, electronic structures and optical properties of novel carbon allotropes, such as monolayer penta-graphene (PG), double-layer PG and T12-carbon, were studied by first-principles calculations. Results of phonon calculations demonstrate that these exotic carbon allotropes are dynamically stable. The bulk T12 phase is an indirect-gap semiconductor having a quasiparticle (QP) bandgap of ~5.19 eV. When the bulk material transforms to a two-dimensional (2D) phase, the monolayer and double-layer PG become quasi-direct gap semiconductors with smaller QP bandgaps of ~4.48 eV and ~3.67 eV, respectively. Furthermore, the partial charge density analysis indicates that the 2D phases retain part of themore » electronic characteristics of the T12 phase. The linear photon energy-dependent dielectric functions and related optical properties including refractive index, extinction coefficient, absorption spectrum, reflectivity, and energy-loss spectrum were also computed and discussed. Additionally, the chemical stability of monolayer PG and the electronic and optical properties of double-side hydrogenated monolayer PG were also investigated. Furthermore, the results obtained from our calculations are beneficial to practical applications of these exotic carbon allotropes in optoelectronics and electronics.« less

  1. Mass specific optical absorption coefficients of mineral dust components measured by a multi wavelength photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.

    2014-09-01

    Mass specific optical absorption coefficients of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at wavelengths of 1064, 532, 355 and 266 nm. These values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. These results are expected to have considerable importance in global radiative forcing calculations. They can also serve as reference for validating calculated wavelength dependent imaginary parts (κ) of complex refractive indices which up to now have been typically deduced from bulk phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk phase measurements.

  2. Enhanced light absorption in graphene via a liquid-crystalline optical diode

    NASA Astrophysics Data System (ADS)

    Pantazi, Aikaterini Iria; Yannopapas, Vassilios

    2016-09-01

    We demonstrate theoretically that light absorption in graphene can be boosted via a light-trapping mechanism based on a liquid-crystalline optical diode. The optical diode consists of twisted-nematic and nematic liquid-crystalline slabs. In particular, we show that, using a proper optical-diode setup, the absorption in a single graphene layer can be enhanced by a factor of four. By varying the pitch of the twisted-nematic liquid-crystalline slabs comprising the diode, one can tune the operating spectral region of the diode and thus enhance the absorption of graphene within a desired spectral window. Our calculations are based on Berreman's 4×4 method which treats anisotropic, isotropic and/ or inhomogeneous layered systems on equal footing.

  3. 1- and 2-photon absorption by laser-cooled 85Rb using an optical nanofiber

    NASA Astrophysics Data System (ADS)

    Russell, L.; Daly, M.; Chormaic, S. Nic

    2012-09-01

    The characteristics of a cold cloud of 85Rb can be non-destructively examined using an optical nanofiber. The nanofiber is a submicron-diameter cylindrical waveguide fabricated from commercially-available optical fiber using a heat-and-pull rig. The nanofiber can be used as a 'dark' or 'bright' probe depending on whether laser light is coupled into the nanofiber. We demonstrate the use of an optical nanofiber as an absorption spectroscopy tool for cold atoms. A frequency-scanned probe beam is launched through the nanofiber and the resonant light is absorbed at the waist of the nanofiber by nearby cold 85Rb atoms. We present recent singlephoton absorption results and comment on the role of surface interactions. Future work on 2-photon absorption using excited state electronic transitions in 85Rb is discussed.

  4. [Retrieval of tropospheric NO2 by multi axis differential optical absorption spectroscopy].

    PubMed

    Xu, Jin; Xie, Pin-hua; Si, Fu-qi; Dou, Ke; Li, Ang; Liu, Yu; Liu, Wen-qing

    2010-09-01

    A method of retrieving NO2 in troposphere based on multi axis differential optical absorption spectroscopy (MAX-DOAS) was introduced. The differential slant column density (dSCD) of NO2 was evaluated by differential optical absorption spectroscopy (DOAS), removing the Fraunhofer structure and Ring effect. Combining the results of different observing directions, the tropospheric NO2 differential slant column density (deltaSCD) was evaluated, and the air mass factor (AMF) was calculated with the radiative transfer model SCIATRAN and the tropospheric NO2 vertical column density (VCD) was retrieved. To ensure the accuracy of the results, it was compared with the results of long path differential optical absorption spectroscopy (LP-DOAS), a good accordance was shown with the correlation coefficients of 0.94027 and 0.96924. PMID:21105419

  5. Instability of photoinduced optical absorption of Bi12SiO20: Al crystals

    NASA Astrophysics Data System (ADS)

    Panchenko, T. V.; Dyachenko, A. A.; Khmelenko, O. V.

    2015-04-01

    The results of the experimental investigation of the instability of the establishment and relaxation of a photochromic effect in aluminum-doped Bi12SiO20 crystals have been presented. The oscillating and nonmonotonic kinetic dependences of the photoinduced optical absorption have been observed. The absorption oscillations are associated with the competition of the formation and destruction of [AlSiO4]0 photochromic centers.

  6. Optical absorption of Ni2+ and Ni3+ ions in gadolinium gallium garnet epitaxial films

    NASA Astrophysics Data System (ADS)

    Vasileva, N. V.; Gerus, P. A.; Sokolov, V. O.; Plotnichenko, V. G.

    2012-12-01

    Single-crystal Ni-doped gadolinium gallium garnet films were grown for the first time from supercooled Bi2O3-B2O3-based melt solutions by liquid-phase epitaxy. Optical absorption bands due to Ni2+, Ni3+ and Bi3+ ions were observed in those films. Interpretation and tabulation of all absorption bands of nickel ions occupying octahedral and tetrahedral sites in the garnet lattice are presented.

  7. Magnetically Responsive Nanostructures with Tunable Optical Properties.

    PubMed

    Wang, Mingsheng; Yin, Yadong

    2016-05-25

    Stimuli-responsive materials can sense specific environmental changes and adjust their physical properties in a predictable manner, making them highly desired components for designing novel sensors, intelligent systems, and adaptive structures. Magnetically responsive structures have unique advantages in applications, as external magnetic stimuli can be applied in a contactless manner and cause rapid and reversible responses. In this Perspective, we discuss our recent progress in the design and fabrication of nanostructured materials with various optical responses to externally applied magnetic fields. We demonstrate tuning of the optical properties by taking advantage of the magnetic fields' abilities to induce magnetic dipole-dipole interactions or control the orientation of the colloidal magnetic nanostructures. The design strategies are expected to be extendable to the fabrication of novel responsive materials with new optical effects and many other physical properties. PMID:27115174

  8. Influence of dissolved organic materials on turbid water optical properties and remote-sensing reflectance

    NASA Technical Reports Server (NTRS)

    Witte, W. G.; Whitlock, C. H.; Harriss, R. C.; Usry, J. W.; Poole, L. R.; Houghton, W. M.; Morris, W. D.; Gurganus, E. A.

    1982-01-01

    The effects of dissolved organic materials on turbid-water optical properties are assessed, by means of field measurements and laboratory simulations in which upwelled reflectance, attenuation, absorption, and backscatter spectral properties at wavelengths from 450 to 800 nm are examined in relation to water chemistry. The data show that dissolved organic materials decrease upwelled reflectance from turbid waters, and that the decrease in reflectance is a nonlinear function of concentration with the largest gradients at low carbon concentrations, depending on wavelength. Upwelled reflectance is found to be highly correlated with two backscatter-absorption parameters used in some optical models, which are nonlinear with dissolved organic material concentration change.

  9. Nonlinear optical properties of multilayer graphene in the infrared.

    PubMed

    Demetriou, Giorgos; Bookey, Henry T; Biancalana, Fabio; Abraham, Eitan; Wang, Yu; Ji, Wei; Kar, Ajoy K

    2016-06-13

    A negative value for the nonlinear refraction in graphene is experimentally observed and unambiguously verified by performing a theoretical analysis arising from the conductivity of the graphene monolayer. The nonlinear optical properties of multi-layer graphene are experimentally studied by employing the Z-scan technique. The measurements are carried out at 1150, 1550, 1900 and 2400 nm with a 100-femtosecond laser source. Under laser illumination the multi-layer graphene exhibits a transmittance increase due to saturable absorption, followed by optical limiting due to two-photon absorption. The saturation irradiance Isat and the two-photon absorption coefficient β are measured in the operating wavelength range. Furthermore, an irradiance-dependent nonlinear refraction is observed and discriminated from the conventional nonlinear refraction coefficient n2, which is not irradiance dependent. The values obtained for the irradiance-dependent nonlinear refraction are in the order of ∼10-9 cm2W-1, approximately 8 orders of magnitude larger than any bulk dielectrics. PMID:27410322

  10. Ovarian tissue characterization using bulk optical properties

    NASA Astrophysics Data System (ADS)

    Tavakoli, B.; Xu, Y.; Zhu, Q.

    2013-03-01

    Ovarian cancer, the deadliest of all gynecologic cancers, is not often found in its early stages due to few symptoms and no reliable screening test. Optical imaging has a great potential to improve the ovarian cancer detection and diagnosis. In this study we have characterized the bulk optical properties of 26 ex-vivo human ovaries using a Diffuse Optical Tomography system. The quantitative values indicated that, in the postmenopausal group, malignant ovaries showed significantly lower scattering coefficient than normal ones. The scattering parameter is largely related to the collagen content that has shown a strong correlation with the cancer development.

  11. Optical diffusion property of chicken tissue

    NASA Astrophysics Data System (ADS)

    Schneider, Patricia S.; Flamholz, Alex; Wong, Peter K.; Lieberman, David H.; Cheung, Tak D.; Itoka, Harriet; Minott, Troy; Quizhpi, Janie; Rodriguez, Jacquelin

    2004-11-01

    Chicken tissue acts as a turbid medium in optical wavelength. Optical characterization data of fresh chicken dark and white meat were studied using the theory of light diffusion. The gaussian-like transmission profile was used to determine the transport mean free path and absorption. The refractive index, a fundamental parameter, was extracted via transmission correlation function analysis without using index-matching fluid. The variation in refractive index also produced various small shifts in the oscillatory feature of the intensity spatial correlation function at distance shorter than the transport mean free path. The optical system was calibrated with porous silicate slabs containing different water contents and also with a solid alumina slab. The result suggested that the selective scattering/absorption of myoglobin and mitochondria in the dark tissues is consistent with the transmission data. The refractive index was similar for dark and white tissues at the He-Ne wavelength and suggested that the index could serve as a marker for quality control. Application to chicken lunchmeat samples revealed that higher protein and lower carbohydrate would shift the correlation toward smaller distance. The pure fat refractive index was different from that of the meat tissue. Application of refractive index as a fat marker is also discussed

  12. Nonlinear dynamics of optical absorption of intense beams

    NASA Astrophysics Data System (ADS)

    Corbett, D.; van Oosten, C. L.; Warner, M.

    2008-07-01

    On traversing materials with absorbing dyes, weak optical beams decay exponentially (a Beer profile), while intense beams develop in time a profile that is spatially linear until at great depth it becomes spatially exponential. This anomalous, deep penetration, due to photobleaching of surface layers, is important for heavy dye loading and intense beams, for instance in photo-actuation. We address the problem of the evolution in time from initial Beer’s Law to a finally deeply-penetrating optical profile in dyes. Our largely analytic solution of the coupled, nonlinear, partial differential equations governing the spatiotemporal decay of the Poynting flux and the nonlinear population dynamics of the photo-active molecules under intense irradiation has application to optomechanical devices.

  13. Optical Properties of Nanoporous Germanium Thin Films.

    PubMed

    Cavalcoli, Daniela; Impellizzeri, Giuliana; Romano, Lucia; Miritello, Maria; Grimaldi, Maria Grazia; Fraboni, Beatrice

    2015-08-12

    In the present article we report enhanced light absorption, tunable size-dependent blue shift, and efficient electron-hole pairs generation in Ge nanoporous films (np-Ge) grown on Si. The Ge films are grown by sputtering and molecular beam epitaxy; subsequently, the nanoporous structure is obtained by Ge+ self-implantation. We show, by surface photovoltage spectroscopy measurements, blue shift of the optical energy gap and strong signal enhancement effects in the np-Ge films. The blue shift is related to quantum confinement effects at the wall separating the pore in the structure, the signal enhancement to multiple light-scattering events, which result in enhanced absorption. All these characteristics are highly stable with time. These findings demonstrate that nanoporous Ge films can be very promising for photovoltaic applications. PMID:26177652

  14. Exploring the electronic and optical properties of AgInO2

    NASA Astrophysics Data System (ADS)

    Bhamu, K. C.; Priolkar, K. R.

    2016-05-01

    We computed the energy band and density of states for electronic properties while for optical properties we computed dielectric function, absorption coefficient, optical conductivity and refractive index. The origin of energy bands is interpreted in terms of density of states. The electronic transitions in energy bands are explained from frequency dependent dielectric constant. Our computed band structure predicts AgInO2 as indirect band gap semiconductor while from optical properties we have predicted importance of AgInO2 in photovoltaic applications. We also reported valence charge density for this compound. Our computed results are in better agreement with available experimental data than those of earlier theoretically reported.

  15. Optical properties of carbon microcoils

    SciTech Connect

    Hikita, Muneaki; Cao, Li E-mail: klafdi1@udayton.edu; Lafdi, Khalid E-mail: klafdi1@udayton.edu

    2014-01-27

    Carbon microcoils (CMCs) have emerged as versatile material artifacts for a variety of applications due to their helical and spiral structures. Embedded in matrix, CMCs have already been demonstrated for their potential tactile/proximity sensor application. In this study, CMCs were prepared using a conventional chemical vapor deposition method, and then were functionalized with octadecylamine. Upon photoexcitation, the functionalized CMCs exhibited photoluminescence in the visible region, which has never been found before. Similar to carbon based nanoparticles, the photoluminescence of CMCs was attributed to electron-hole radiative recombination after surface passivation. The results suggested that this kind of fluorescent functionalized CMCs might be used as a promising class of optical agents for biological applications.

  16. Optical Properties Of Turbidity Standards

    NASA Astrophysics Data System (ADS)

    Ronald, J.; Zaneveld, V.; Spinrad, Richard W.; Bartz, Robert

    1980-03-01

    Measurements of light scattering and light attenuation were made for suspensions of formazin and diatomaceous earth. Light scattering was measured for light of wavelength 632.8 nm at angles from 0.1° to 1.0° and for light of wavelengths 400, 500, 550, 600, 650, and 700 nm at 45°. Light attenuation was measured over a 25 cm pathlength for light of 660 nm. These measurements were made for suspensions which varied from 0 to 40 Jackson Turbidity Units of formazin and 0 to 40 mg/1 of diatomaceous earth. The results indicate the necessity for multiple optical measurements for determinations of turbidity of water. In addition the tables and curves presented may be used in the calibration of light scattering meters and transmissometers which are used for turbidity studies.

  17. Polyethylene laser welding based on optical absorption variations

    NASA Astrophysics Data System (ADS)

    Galtieri, G.; Visco, A.; Nocita, D.; Torrisi, L.; Ceccio, G.; Scolaro, C.

    2016-04-01

    Polymeric materials, both pure and containing nanostructures, can be prepared as thin sheets in order to produce joints with an interface between an optically transparent sheet and an optically absorbent substrate to be welded by infrared pulsed laser irradiation. The Laser Transmission Welding (LTW) technique has been successfully applied in order to join two or more thermoplastic polymeric sheets that must have a similar chemical composition. In this research work, polymeric joints of Ultra High Molecular Weight Polyethylene sheets were realized, characterized and welded. Some polymer sheets were doped, at different concentrations, with carbon nano-particles absorbent the laser radiation. A pulsed laser operating in the wavelength region 532 nm with intensity of the order of 109 Watt/cm2 was employed to be transmitted by the transparent polymer and to be absorbed by the carbon enriched surface. At the interface of the two polymers the released energy induces melting, that is assisted by pressure, producing a fast and resistant welding zone. Mechanical and optical characterizations and surface analyses are presented and discussed.

  18. The nonlinear absorption and optical limiting in phenoxy-phthalocyanines liquid in nano- and femto-second regime: Experimental studies

    NASA Astrophysics Data System (ADS)

    Zhang, Yun-Dong; Zhao, Zhen-Yu; Yao, Cheng-Bao; Yang, Lan; Li, Jin; Yuan, Ping

    2014-06-01

    The nonlinear optical properties of 2, 9, 16, 23-phenoxy-phthalocyanine (Pc1) and 2, 9, 16, 23-phenoxy-phthalocyanine-zinc (Pc2) in solution, have been investigated using the Z-scan technique at 800 nm with 100 fs pulse width and at 532 nm with 10 ns pulse width, respectively. It is found that the reverse saturable absorption (RSA) with femtosecond pulse excitation is much larger than that of nanosecond pulse excitation. The nonlinear absorption properties in nanosecond regime and femtosecond regime were analyzed by using five-level model and singlet four-level model, respectively. The results show that the critical intensity value of Pc2 is higher than Pc1 when the contribution of the high excited-state absorption is introduced in the sample. Moreover, optical limiting based on RSA was performed and limiting thresholds were evaluated for both samples. The results show that the Pc1 and Pc2 exhibit better limiting characteristics because of its stronger RSA response.

  19. Optical properties of KD*P modulators

    NASA Technical Reports Server (NTRS)

    West, E. A.; Bhatia, S. S.

    1990-01-01

    Longitudinal KD*P modulators are used in ground-based solar magnetographs to eliminate seeing effects. Although the modulators can be used as variable retarders, the optical properties when zero voltage is applied influences the performance on instruments requiring very accurate polarization measurements. Measurements at the Marshall Space Flight Center are discussed in terms of the optical properties of KD*P modulators when zero voltage is applied. The measurements can be used to predict the modulation characteristics of the devices and to determine the polarization accuracy that can be expected from the vector magnetograph.

  20. Single snapshot imaging of optical properties

    PubMed Central

    Vervandier, Jean; Gioux, Sylvain

    2013-01-01

    A novel acquisition and processing method that enables single snapshot wide field imaging of optical properties in the Spatial Frequency Domain (SFD) is described. This method makes use of a Fourier transform performed on a single image and processing in the frequency space to extract two spatial frequency images at once. The performance of the method is compared to the standard six image SFD acquisition method, assessed on tissue mimicking phantoms and in vivo. Overall both methods perform similarly in extracting optical properties. PMID:24409392

  1. Optical properties of water at high temperature

    SciTech Connect

    French, Martin; Redmer, Ronald

    2011-04-15

    We calculate optical properties of water along the principal Hugoniot curve from ambient conditions up to temperatures of 130 000 K with density functional theory (DFT) and the Kubo-Greenwood formula. The effect of the exchange correlation functional is examined by comparing the generalized gradient approximation with a hybrid functional that contains Fock exchange. We find noticeable but moderate differences between the respective results which decrease rapidly above 80 000 K. The reflectivity along the principal Hugoniot is calculated and a good qualitative but fair quantitative agreement with available experimental data is found. Our results are of general relevance for calculations of optical properties with DFT at zero and elevated temperature.

  2. Absorption spectroscopy of powdered materials using time-resolved diffuse optical methods.

    PubMed

    D'Andrea, Cosimo; Obraztsova, Ekaterina A; Farina, Andrea; Taroni, Paola; Lanzani, Guglielmo; Pifferi, Antonio

    2012-11-10

    In this paper a novel method, based on time-resolved diffuse optical spectroscopy, is proposed to measure the absorption of small amounts of nanostructured powder materials independent of scattering. Experimental validation, in the visible and near-infrared spectral range, has been carried out on India Inkparticles. The effectiveness of the technique to measure scattering-free absorption is demonstrated on carbon nanotubes. The comparison between the absorption spectra acquired by the proposed method and conventional measurements performed with a commercial spectrophotometer is discussed. PMID:23142900

  3. Ultraviolet absorption of common spacecraft contaminants. [to control effects of contaminants on optical systems

    NASA Technical Reports Server (NTRS)

    Colony, J. A.

    1979-01-01

    Organic contamination of ultraviolet optical systems is discussed. Degradation of signal by reflection, scattering, interference, and absorption is shown. The first three processes depend on the physical state of the contaminant while absorption depends on its chemical structure. The latter phenomenon is isolated from the others by dissolving contaminants in cyclohexane and determining absorption spectra from 2100A to 3600A. A variety of materials representing the types of contaminants responsible for most spaceflight hardware problems is scanned and the spectra is presented. The effect of thickness is demonstrated for the most common contaminant, di(2 ethyl hexyl)phthalate, by scanning successive dilutions.

  4. The Optical Absorption Coefficient of Bean Seeds Investigated Using Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sanchez-Hernandez, G.; Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.; Perez-Reyes, M. C. J.; Martinez, E. Moreno

    2015-06-01

    A knowledge about seed optical parameters is of great relevance in seed technology practice. Such parameters provide information about its absorption and reflectance, which could be useful for biostimulation processes, by light sources, in early stages of seed germination. In the present research photoacoustic spectroscopy (PAS) and the Rosencwaig and Gersho model were used to determine the optical absorption coefficient () of five varieties of bean seeds ( Phaseolus vulgaris L.), of different productive cycles; the seeds were biostimulated by laser treatment to evaluate the effects of biostimulation pre-sowing. It was found that the bean varieties V1, V2, V4, and V5 were optically opaque in the visible spectrum; in the case of the V3 variety, this sample was optically transparent from 680 nm. The varieties of the studied bean seeds showed significant statistical differences in sizes and also in their optical absorption spectra. The biostimulation effects showed that the seed samples with a higher optical penetration length had a positive biostimulation, in the percentage of germination, obtaining an enhancement of 47 % compared to the control sample. The utility of PAS for the optical characterization of seeds has been demonstrated in this study of the laser biostimulation process of this kind of samples.

  5. Laser modulation of optical absorption in ZnSe

    NASA Technical Reports Server (NTRS)

    Major, R. W.

    1971-01-01

    The possibility of producing and detecting laser induced modulation of absorption (LIMA) in ZnSe crystals using a moderate laser intensity of about 6 mw output was investigated. The modulation is smaller than that previously obtained with higher laser photon flux, but is not too difficult to detect. Modulation of the order of a few parts in 10 to the 5th power, up to one part in 10 to the 4th power appears typical at the present. LIMA pulse shapes were recorded with varying system resolutions at a half dozen wavelengths in the visible, from 4800 A to 6000 A. Detailed data were taken, particularly at 5000 A, for a range of time intervals following laser pulse turn-on. Quantitative study of the excitation and decay kinetics of these is underway, though analysis is not complete. Major features are discussed with attention centered upon the detailed measurements made most recently at 5000 A.

  6. Optical properties of polydimethylsiloxane (PDMS) during nanosecond laser processing

    NASA Astrophysics Data System (ADS)

    Stankova, N. E.; Atanasov, P. A.; Nikov, Ru. G.; Nikov, R. G.; Nedyalkov, N. N.; Stoyanchov, T. R.; Fukata, N.; Kolev, K. N.; Valova, E. I.; Georgieva, J. S.; Armyanov, St. A.

    2016-06-01

    This article presents experimental investigations of effects of the process parameters on the medical grade polydimethylsiloxane (PDMS) elastomer processed by laser source with irradiation at UV (266 and 355 nm), VIS (532 nm) and NIR (1064 nm). Systematic experiments are done to characterize how the laser beam parameters (wavelength, fluence, and number of pulses) affect the optical properties and the chemical composition in the laser treated areas. Remarkable changes of the optical properties and the chemical composition are observed. Despite the low optical absorption of the native PDMS for UV, VIS and NIR wavelengths, successful laser treatment is accomplished due to the incubation process occurring below the polymer surface. With increasing of the fluence and the number of the pulses chemical transformations are revealed in the entire laser treated area and hence decreasing of the optical transmittance is observed. The incubation gets saturation after a certain number of pulses and the laser ablation of the material begins efficiently. At the UV and VIS wavelengths the number of the initial pulses, at which the optical transmittance begins to reduce, decreases from 16 up to 8 with increasing of the laser fluence up to 1.0, 2.5 and 10 J cm-2 for 266, 355 and 532 nm, respectively. In the case of 1064 nm the optical transmittance begins to reduce at 11th pulse incident at a fluence of 13 J cm-2 and the number of the pulses decreases to 8 when the fluence reaches value of 16 J cm-2. The threshold laser fluence needed to induce incubation process after certain number of pulses of 8 is different for every wavelength irradiation as the values increase from 1.0 for 266 nm up to 16 J cm-2 for 1064 nm. The incubation and the ablation processes occur in the PDMS elastomer material during its pulsed laser treatment are a complex function of the wavelength, fluence, number of pulses and the material properties as well.

  7. Physical oceanographic processes influence bio-optical properties in the Tasman Sea

    NASA Astrophysics Data System (ADS)

    Cherukuru, Nagur; Davies, Peter L.; Brando, Vittorio E.; Anstee, Janet M.; Baird, Mark E.; Clementson, Lesley A.; Doblin, Martina A.

    2016-04-01

    Remote sensing observations show optical signatures to conform to the physical oceanographic patterns in the Tasman Sea. To test the link between physical oceanographic processes and bio-optical properties we investigated an in situ bio-optical dataset collected in the Tasman Sea. Analysis of in situ observations showed the presence of four different water masses in the Tasman Sea, formed by the relatively warm and saline East Australia Current (EAC) water, a mesoscale cold core eddy on the continental slope, cooler Tasman Sea water on the shelf and river plume water. The distribution of suspended substances and their inherent optical properties in these water masses were distinctly different. Light absorption and attenuation budgets indicate varying optical complexity between the water masses. Specific inherent optical properties of suspended particulate and dissolved substances in each group were different as they were influenced by physical and biogeochemical processes specific to that water mass. Remote sensing reflectance signature varied in response to changing bio-optical properties between the water masses; thus providing the link between physical oceanographic processes, bio-optical properties and the optical signature. Findings presented here extend our knowledge of the Tasman Sea, its optical environment and the role of physical oceanographic processes in influencing the inherent optical properties and remote sensing signature in this complex oceanographic region.

  8. Influence of Dose on Particle Size and Optical Properties of Colloidal Platinum Nanoparticles

    PubMed Central

    Gharibshahi, Elham; Saion, Elias

    2012-01-01

    Attempts to produce colloidal platinum nanoparticles by using steady absorption spectra with various chemical-based reduction methods often resulted in the fast disappearance of the absorption maxima leaving reduced platinum nanoparticles with little information on their optical properties. We synthesized colloidal platinum nanoparticles in an aqueous solution of polyvinyl pyrrolidone by gamma radiolytic reduction method, which produced steady absorption spectra of fully reduced and highly pure platinum nanoparticles free from by-product impurities or reducing agent contamination. The average particle size was found to be in the range of 3.4–5.3 nm and decreased with increasing dose due to the domination of nucleation over ion association in the formation of metal nanoparticles by the gamma radiolytic reduction method. The platinum nanoparticles exhibit optical absorption spectra with two absorption peaks centered at about 216 and 264 nm and the peaks blue shifted to lower wavelengths with decreasing particle size. The absorption spectra of platinum nanoparticles were also calculated using quantum mechanical treatment and coincidently a good agreement was obtained between the calculated and measured absorption peaks at various particle sizes. This indicates that the 216 and 264-nm absorption peaks of platinum nanoparticles conceivably originated from the intra-band transitions of conduction electrons of (n = 5, l = 2) and (n = 6, l = 0) energy states respectively to higher energy states. The absorption energies, i.e., conduction band energies of platinum nanoparticles derived from the absorption peaks increased with increasing dose and decreased with increasing particle size. PMID:23203091

  9. Electro-optical properties of Rydberg excitons

    NASA Astrophysics Data System (ADS)

    Zielińska-Raczyńska, Sylwia; Ziemkiewicz, David; Czajkowski, Gerard

    2016-07-01

    We show how to compute the electro-optical functions (absorption, reflection, and transmission) when Rydberg exciton-polaritons appear, including the effect of the coherence between the electron-hole pair and the electromagnetic field. With the use of the real density matrix approach, numerical calculations applied for the Cu2O crystal are performed. We also examine in detail and explain the dependence of the resonance displacement on the state number and applied electric field strength. We report a fairly good agreement with recently published experimental data.

  10. Dynamics and two-photon absorption properties of chromophore functionalized semiconductor nanoparticles

    NASA Astrophysics Data System (ADS)

    Varaganti, Shankar; Gessesse, Mathias; Obare, Sherine O.; Ramakrishna, Guda

    2009-08-01

    Two photon absorption cross-sections and fluorescence dynamics of Riboflavin, Fluorescein 548, Coumarin 519 and Quinizarin adsorbed onto reactive (TiO2) and non-reactive (ZrO2) semiconductor nanoparticles have been investigated. These dye molecules are chosen because of their inherently different anchoring groups with which they can bind to semiconductor nanoparticles giving a handle to probe the influence of anchoring group as well as molecule-nanoparticle electronic coupling on the two-photon absorption and nonlinear optical properties. Two-photon excited fluorescence technique has been utilized to monitor the two photon absorption cross-sections and the dynamics of singlet states are followed with femto second fluorescence upconversion. Interesting cross-section trends have been observed where the TPA cross-section of chromophore on ZrO2 surface is similar or lower to that of the free dye while the cross-sections seem to be higher on the surface of reactive TiO2 nanoparticle surface. Fluorescence upconversion investigations were able to probe the electronic interactions of the chromophore with semiconductor nanoparticle and also the adsorption of the chromophores on the surface of the nanoparticle.

  11. Optical properties of graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Karimi, Farhad; Knezevic, Irena

    We calculate the dielectric function and optical conductivity of ultra-narrow armchair graphene nanoribbons (AGNRs) and zigzag graphene nanoribbons (ZGNRs) by a self- consistent-field approach within a Markovian master-equation formalism (SCF-MMEF) coupled with full-wave electromagnetic equations. Based on third-nearest-neighbor tight-binding, with appropriate modifications for AGNRs and ZGNRs, we calculate electron dispersions and Bloch wave functions in excellent agreement with the local spin-density approximation (LSDA) results. A generalized Markovian master equation of the Lindblad form, which maintains the positivity of the density matrix, is derived to describe the interaction of the electronic system with an external electromagnetic field (to first order) and with a dissipative environment (to second order). Not only does the SCF-MMEF capture the interband electron-hole-pair generation, but it also accurately accounts for concurrent interband and intraband electron scattering with phonons and impurities. We employ the SCF-MMEF to calculate the dielectric function, complex conductivity, and loss function for both suspended and supported AGNRs and ZGNRs with different widths. Then, we obtain the plasmon dispersion and propagation length from the loss-function maximum. Support by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0008712.

  12. Effect of Sn on the optical band gap determined using absorption spectrum fitting method

    SciTech Connect

    Heera, Pawan; Kumar, Anup; Sharma, Raman

    2015-05-15

    We report the preparation and the optical studies on tellurium rich glasses thin films. The thin films of Se{sub 30}Te{sub 70-x} Sn{sub x} system for x= 0, 1.5, 2.5 and 4.5 glassy alloys prepared by melt quenching technique are deposited on the glass substrate using vacuum thermal evaporation technique. The analysis of absorption spectra in the spectral range 400nm–4000 nm at room temperature obtained from UV-VIS-NIR spectrophotometer [Perkin Elmer Lamda-750] helps us in the optical characterization of the thin films under study. The absorption spectrum fitting method is applied by using the Tauc’s model for estimating the optical band gap and the width of the band tail of the thin films. The optical band gap is calculated and is found to decrease with the Sn content.

  13. Monitoring of volcanic sulphur dioxide emissions using differential absorption lidar (DIAL), differential optical absorption spectroscopy (DOAS), and correlation spectroscopy (COSPEC)

    NASA Astrophysics Data System (ADS)

    Weibring, P.; Edner, H.; Svanberg, S.; Cecchi, G.; Pantani, L.; Ferrara, R.; Caltabiano, T.

    1998-10-01

    The total fluxes of sulphur dioxide from the Italian volcanoes Etna, Stromboli, and Vulcano were studied using optical remote sensing techniques in three shipborne field experiments (1992, 1994, and 1997). The main purpose of the experiments was to compare active (laser) techniques with passive monitoring. Differential absorption lidar (DIAL) measurements were implemented by placing the Swedish mobile lidar system on board the Italian research vessel Urania, sailing under the volcanic plumes. Simultaneously, the passive differential optical absorption spectroscopy (DOAS) technique was used for assessing the total overhead gas burden. Finally, correlation spectroscopy (COSPEC) was also implemented in one of the campaigns. Differences in integrated gas column assessment are expected and observed, mostly connected to complex scattering conditions influencing the passive measurements. Since such measurements are much employed in routine volcanic monitoring it is of great interest to model and provide corrections to the raw data obtained. Lidar measurements proved to be quite useful for this purpose. By combining the integrated gas concentration over the plume cross section with wind velocity data, SO2 fluxes of the order of 1000, 100, and 10 tonnes/day were measured for Mt. Etna, Stromboli, and Vulcano, respectively.

  14. Optical And Protective Properties Of Hard Carbon Coatings

    NASA Astrophysics Data System (ADS)

    Dischler, B.; Bubenzer, A.; Koidl, P.; Brandt, G.

    1983-09-01

    In recent years amorphous carbon coatings found growing interest because of their optical and protective properties. We have deposited hydrogenated amorphous carbon films (a-C:H) from an RF excited discharge in benzene vapour. Substrates include germanium, glass and MgF2. The refractive index can be tuned between 1.8 and 2.2 and efficient antireflection coatings on Ge have been prepared. We have determined the optical absorption from the UV to the IR range (0.2 - 25 μm). A typical 1 µm thick a-C:H film is transparent (> 50% transmission) from 750 nm to the far infrared. Amorphous carbon films are harder than sapphire and are resistant to concentrated acids and bases.

  15. Electrical engineering of the optical properties in silicene

    NASA Astrophysics Data System (ADS)

    Bao, Hairui; Guo, Junji; Liao, Wenhu; Zhao, Heping

    2015-02-01

    Based on the intersubband transition theorem of the semiconductors, we have theoretically investigated the optical properties of a three-terminal silicene-based device under the irradiation of a circularly polarized terahertz electromagnetic field. The system spin-orbit-coupled electronic structure may be engineered to topological insulated (TI) and band insulated (BI) state, respectively, by the staggered sublattice potential from the back-gate voltage. It has been demonstrated that the dielectric functions and optical absorption spectra from the TI spin-up and spin-down subbands behave redshift and blueshift, respectively, with the increase in the sublattice potential, while those from the BI spin-up and spin-down subbands have been proven to be continually blue-shifted with the staggered sublattice potential. The novel features may be useful in the design of the spintronic and optoelectronic devices based on silicene.

  16. Nonlinear optical properties of lead sulfide nanocrystals in polymeric coatings

    NASA Astrophysics Data System (ADS)

    Lu, S. W.; Sohling, U.; Mennig, M.; Schmidt, H.

    2002-10-01

    Lead sulfide (PbS) nanocrystals with a particle size of 3.3 +/- 0.7 nm have been synthesized in a poly vinyl alcohol (PVA) coating on fused silica glass substrates. The coating was dip-coated from a PVA aqueous solution, in which PbS nanocrystals were precipitated and stabilized in the polymer matrix. Third-order nonlinear optical susceptibility of PbS nanocrystals is dependent on the wavelength with its maximum located near the first excitonic absorption peak resulting from the quantum confinement effect, according to the results of degenerate four wave-mixing. This suggests an enhancement of the nonlinear optical property by excitonic resonance. The maximum figure of merit, χ(3) /α, is as high as 2.91 × 10-12 esu m as measured at 595 nm.

  17. Optical properties of laser-induced heavily doped Si

    NASA Astrophysics Data System (ADS)

    Ravindra, N. M.; Mhoronge, J. F.; Jouanne, M.

    1985-09-01

    An analysis of experimental studies (Slaoui et al., 1983) of the optical properties of laser-induced heavily doped Si layers is presented. The analysis has been made on the basis of models like those of Penn (1962) and Breckenridge et al. (1974). The calculations show that, in general, the effective number of electrons contributing to optically induced electronic transitions, increases as does the imaginary part of the complex dielectric constant. This reflects an increased absorption coefficient for these As-doped samples. These studies have been carried out on samples of Si heavily doped by ion-implantation followed by a laser-annealing process. The conclusions based on these studies are seen to be in accord with those of Aspnes et al. (1984) and Vina and Cardona (1984).

  18. Optical Properties of Black and Brown Carbon Aerosols from Laboratory Combustion of Wildland Fuels

    NASA Astrophysics Data System (ADS)

    Beres, N. D.; Molzan, J.

    2015-12-01

    Aerosol light absorption in the solar spectral region (300 nm - 2300 nm) of the atmosphere is key for the direct aerosol radiative forcing, which is determined by aerosol single scattering albedo (SSA), asymmetry parameter, and by the albedo of the underlying surface. SSA is of key importance for the sign and quantity of aerosol direct radiative forcing; that is, does the aerosol make the earth look darker (heating) or whiter (cooling)? In addition, these optical properties are needed for satellite retrievals of aerosol optical depth and properties. During wildland fires, aerosol optical absorption is largely determined by black carbon (BC) and brown carbon (BrC) emissions. BC is strongly absorbing throughout the solar spectrum, while BrC absorption strongly increases toward shorter wavelength and can be neglected in the red and infrared. Optical properties of BrC emitted from wildland fires are poorly understood and need to be studied as function of fuel type and moisture content and combustion conditions. While much more is known about BC optical properties, knowledge for the ultraviolet (UV) spectral region is still lacking and critically needed for satellite remote sensing (e.g., TOMS, OMI) and for modeling of tropospheric photochemistry. Here, a project to better characterize biomass burning aerosol optical properties is described. It utilizes a laboratory biomass combustion chamber to generate aerosols through combustion of different wildland fuels of global and regional importance. Combustion aerosol optics is characterized with an integrating nephelometer to measure aerosol light scattering and a photoacoustic instrument to measure aerosol light absorption. These measurements will yield optical properties that are needed to improve qualitative and quantitative understanding of aerosol radiative forcing and satellite retrievals for absorbing carbonaceous aerosols from combustion of wildland fuels.

  19. [Study on using apparent spectrum to retrieve the inherent optical properties of ocean water].

    PubMed

    Zhang, Min-wei; Dong, Qing; Tang, Jun-wu; Song, Qing-jun

    2011-05-01

    The inherent optical properties are needed when establishing the semi-analytic model in the ocean color retrieval algorithm. Using the in-situ measurements, a retrieval model for inherent optical properties from remote sensing reflectance was established. The in-situ data measured in the 2003 spring cruise over the Yellow and East China Seas is introduced. The measurement method for remote sensing reflectance, particle backscattering and absorption coefficients are detailed. Based on the bio-optical model, the inherent optical properties were retrieved by optimization of Nelder-Mead simplex. The retrieval results of the absorption and backscattering coefficients for the material other than pure water were compared with the counterpart of the in-situ measurements. The comparison shows that the root-mean-square relative error for the absorption coefficient of materials other than water is less than 33%. The value is 30% for the particle backscattering coefficient. The analysis of the error shows that the retrieval model established in this paper can provide an efficient approach to retrieving the absorption and backscattering coefficients. The retrieval model can provide a reference for the application of remotely sensed data to the research on the bio-optical properties of Yellow and East China Seas. PMID:21800610

  20. Structural, thermal, linear and nonlinear optical studies of an organic optical limiter based on reverse saturable absorption

    NASA Astrophysics Data System (ADS)

    Menezes, Anthoni Praveen; Raghavendra, S.; Jayarama, A.; Sarveshwara, H. P.; Dharmaprakash, S. M.

    2016-09-01

    A new derivative of chalcone, 3-(4-bromophenyl)-1-(pyridin-4-yl) prop-2-en-1-one (4BP4AP), crystallizing in centrosymmetric structure has been synthesized using the Claisen-Schmidt condensation reaction method. The FTIR and FT-Raman spectral studies were carried out on 4BP4AP for structural conformation. The single crystals were grown using slow evaporation solution growth technique. The single crystal XRD of the crystal shows that the crystal system of 4BP4AP is triclinic with space group P-1. Scanning electron microscope images enunciate the surface smoothness and the two dimensional growth mechanisms in the crystal. The crystal is transparent in the entire visible region as indicated by the UV-VIS-NIR spectrum. The thermal stability and phase transition of the compound was studied by thermogravimetric and differential scanning calorimetric analysis and found to be stable up to 200 °C. By performing the open aperture z-scan experiment, nonlinear absorption and optical limiting behavior of the crystal were studied. The crystal can be used for optoelectronic application due to its excellent photo-physical properties.

  1. Optical Properties of Suspended and Substrate Graphene

    NASA Astrophysics Data System (ADS)

    Meera, V.

    2010-03-01

    Graphene, a two-dimensional material made purely of carbon atoms arranged in a hexagonal lattice has attracted the attention of scientific community since it was first produced in 2004. Due to the peculiarity in its band structure and various striking characteristics (eg. high electrical conductivity, mechanical robustness, large thermal conductivity, tunable carrier type and mobility etc.) this has become significant both technologically as well as for fundamental research. Both experimental and theoretical investigations have been taking place to study its various properties viz. transport, electronic, thermal and optical properties. In this work, optical properties of suspended monolayer-graphene and monolayer-graphene deposited on dielectric substrates are studied by calculating the optical quantities such as coefficient of reflection and reflected polarization analytically with the help of Maxwell's equations for the respective systems. Behavior of above mentioned optical quantities with respect to various parameters are studied to compare the two systems. This study can be used to obtain the conductivity tensor of graphene with its anisotropic behavior obtained from the azimuthal angle dependence of the optical quantities. The substrate-graphene is also interesting due to the observation of Brewster's phenomena with Brewster's angle varying with respect to the azimuthal angle (an oscillation with a period of 180 degrees).

  2. Magnetic colloid by PLA: Optical, magnetic and thermal transport properties

    NASA Astrophysics Data System (ADS)

    Pandey, B. K.; Shahi, A. K.; Gopal, Ram

    2015-08-01

    Ferrofluids of cobalt and cobalt oxide nanoparticles (NPs) have been successfully synthesized using liquid phase-pulse laser ablation (LP-PLA) in ethanol and double distilled water, respectively. The mechanism of laser ablation in liquid media and formation process for Co target in double distilled water (DDW) and ethanol are speculated based on the reactions between laser generated highly nascent cobalt species and vaporized solvent media in a confined high temperature and pressure at the plume-surrounding liquid interface region. Optical absorption, emission, vibrational and rotational properties have been investigated using UV-vis absorption, photoluminescence (PL) and Fourier transform-infra red (FT-IR) spectroscopy, respectively. In this study optical band gap of cobalt oxide ferrofluids has been engineered using different pulse energy of Nd:YAG laser in the range of (2.80-3.60 eV). Vibrating sample magnetometer (VSM) is employed to determine the magnetic properties of ferrofluids of cobalt and cobalt oxide NPs while their thermal conductivities are examined using rotating disc method. Ferrofluids have gained enormous curiosity due to many technological applications, i.e. drug delivery, coolant and heating purposes.

  3. Optical absorption and small-polaron hopping in oxygen deficient and lithium-ion-intercalated amorphous titanium oxide films

    NASA Astrophysics Data System (ADS)

    Triana, C. A.; Granqvist, C. G.; Niklasson, G. A.

    2016-01-01

    Optical absorption in oxygen-deficient and Li+-ion inserted titanium oxide films was studied in the framework of small-polaron hopping. Non-stoichiometric TiOy films with 1.68 ≤ y ≤ 2.00 were deposited by reactive DC magnetron sputtering and were subjected to electrochemical intercalation of Li+-ions and charge-balancing electrons to obtain LixTiOy films with 0.12 ≤ x ≤ 0.34. Dispersion analysis was applied to calculate the complex dielectric function ɛ(ℏω) ≡ ɛ1(ℏω) + i ɛ2(ℏω) from numerical inversion of optical transmittance and reflectance spectra; a superposition of Tauc-Lorentz and Lorentz oscillator models was used for this purpose. Data on ɛ2(ℏω) were employed to calculate the optical conductivity and fit this property to a small-polaron model for disordered systems with strong electron-phonon interaction and involving transitions near the Fermi level. The introduction of oxygen vacancies and/or Li+ insertion yielded band gap widening by ˜0.20-0.35 eV, and both processes induced similar low-energy optical absorption. The small-polaron-based analysis indicated increases in the Fermi level by ˜0.15-0.3 eV for sub-stoichiometric and/or Li+-inserted films. This suggests the existence of polaronic Ti3+ states in the lower part of the conduction band arising from transfer of electrons from oxygen vacancies and/or inserted Li+ species. The present article is a sequel to an earlier paper on oxygen-deficient and/or Li+-inserted amorphous WOy thin films and forms part of a comprehensive investigation of optical absorption in amorphous transition metal oxides with different valence states of the metallic ions.

  4. Structure and properties of optical waveguides in stoichiometric LiNbO{sub 3} crystals

    SciTech Connect

    Kostritskii, S. M. Korkishko, Yu. N.; Fedorov, V. A.; Frolova, M. V.; Korepanov, N. S.; Moretti, P.

    2009-12-15

    The structures of proton-exchanged and implanted waveguides are studied by X diffraction analysis and vibration spectroscopy. On the basis of the absorption's spectroscopy data in the visible region and the data on the shift of the fundamental absorption edge in the nearultraviolet region, a comparative analysis of technologically conditioned variations in the nonlinear optical properties of proton-exchanged and implanted waveguides in stoichiometric LiNbO{sub 3} crystals is conducted.

  5. Preparation and optical property of anatase hollow microsphere with mesoporosity

    SciTech Connect

    Li Guohua Zhu Jingtao; Tian Wei; Ma Chunan

    2009-02-04

    Anatase hollow sphere with mesoporosity was prepared by sol pyrogenation used TiCl{sub 4} as precursor only. The samples were characterized by X-ray diffraction and scan electron microscopy, their specific surface area was measured by N{sub 2} adsorption. The results show that the sample calcined at 500 deg. C for 2 h is phase pure anatase, the morphology of the particle of the sample is hollow sphere, and the wall of the hollow sphere is constituted of anatase nanoparticle and mesoporosity. The crystallinity, the crystal size, the pore width, the specific surface area and the crystal phase of the sample are changing along with the calcined temperature. The optical property was measured by ultraviolet radiation vis absorption spectra of the suspension of the samples. The results show that the optical property of the sample is better than that of nanoanatase particle, and the optical property of hollow sphere titania with mesoporosity is related to its crystal phase, specific surface area, crystal size, porosity size and crystallinity.

  6. Growth, Optical Properties, and Optimization of Infrared Optoelectronic Materials

    NASA Astrophysics Data System (ADS)

    Webster, Preston Thomas

    superlattices, including bismide-based designs. The software has the capability to limit results to designs that can be produced with high structural and optical quality, and optimized designs in terms of maximizing absorption are identified for several infrared superlattice systems at the GaSb lattice constant. The accuracy of the software predictions are tested with the design and growth of an optimized mid-wave infrared InAs/InAsSb superlattice which exhibits superior optical and absorption properties.

  7. Light scattering and absorption properties of aerosol particles in the urban environment of Granada, Spain

    NASA Astrophysics Data System (ADS)

    Lyamani, H.; Olmo, F. J.; Alados-Arboledas, L.

    Surface measurements of optical and physical aerosol properties were made at an urban site, Granada (Spain) (37.18°N, 3.58°W, 680 m a.s.l), during winter 2005-2006. Measurements included the aerosol scattering, σsca, and backscattering coefficients, σbsca, at three wavelengths (450, 550 and 700 nm) measured at low relative humidity (RH<50%) by an integrating nephelometer, the absorption coefficient at 670 nm, σabs, measured with a multi-angle absorption photometer, and aerosol size distribution in the 0.5-20 μm aerodynamic diameter range registered by an aerodynamic aerosol sizer (APS-3321, TSI). The hourly average of σsca (550 nm) ranged from 2 to 424 M m -1 with an average value of 84±62 M m -1 (±S.D.). The Angstrom exponent presented an average value of 1.8±0.3, suggesting a large fraction of fine particles at the site, an observation confirmed by aerosol size distribution measurements. The hourly average of σabs (670 nm) ranged from 1.7 to 120.5 M m -1 with an average value of 28±20 M m -1. The results indicate that the aerosol absorption coefficient in Granada was relatively large. The largest σsca value was associated with air masses that passed over heavily polluted European areas and local stagnation conditions. High absorbing aerosol level was obtained during dust transport from North Africa probably due to the presence of hematite. Based on the measured scattering and absorption coefficients, a very low average value of the single scattering albedo of 0.66±0.11 at 670 nm was calculated, suggesting that urban aerosols in this region contain a large fraction of absorbing material. A clear diurnal pattern was observed in scattering and absorption coefficients and particle concentrations with two local maxima occurring in early morning and late evening. This behavior can be explained in terms of local conditions that control the particle sources associated with traffic and upward mixing of the aerosol during the daytime development of a

  8. Measurements of the optical absorption coefficient of Ar8+ ion implanted silicon layers using the photothermal radiometry and the modulated free carrier absorption methods

    NASA Astrophysics Data System (ADS)

    Chrobak, Ł.; Maliński, M.; Pawlak, M.

    2014-11-01

    This paper presents a method of the measurement of the optical absorption coefficient of the Ar8+ ions implanted layers in the p-type silicon substrate. The absorption coefficient is calculated using a value of the attenuation of amplitudes of a photothermal radiometry (PTR) and/or a modulation free carrier absorption (MFCA) signals and the implanted layer thickness calculated by means of the TRIM program. The proposed method can be used to indicate the amorphization of the ions implanted layers.

  9. Optical properties of Apollo 12 moon samples.

    NASA Technical Reports Server (NTRS)

    O'Leary, B.; Briggs, F.

    1973-01-01

    We present the photometric phase function, color, normal albedo, polarimetric phase function, and spectrophotometry of the Apollo 12 soil. With a few minor exceptions, the optical properties of the Apollo 12 soil are very similar to those of the Apollo 11 soil and of lunar mare surfaces.

  10. Optical Properties of Bruised Apple Tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the optical properties of apple tissue, especially bruised tissue, can help us prevent or mitigate bruise occurrence during harvest and postharvest operations, and develop an effective method for detecting bruises during sorting and grading. This research was aimed at determining the o...

  11. Nonlinear quantum optical properties of graphene

    NASA Astrophysics Data System (ADS)

    Semnani, Behrooz; Hamed Majedi, Amir; Safavi-Naeini, Safieddin

    2016-03-01

    We present a semiclassical theory of the linear and nonlinear optical response of graphene. The emphasis is placed on the nonlinear optical response of graphene from the standpoint of the underlying chiral symmetry. The Bloch quasiparticles in the low-energy limit around the degeneracy points are dominantly chiral. It is shown that this chiral behavior in conjunction with scale invariance in graphene around the Dirac points results in the strong nonlinear optical response. Explicit expressions for the linear and nonlinear conductivity tensors are derived based on semiconductor Bloch equations (SBEs). The linear terms agree with the result of Kubo formulation. The three main additive mechanisms contribute in the nonlinear optical response of graphene: pure intraband, pure interband and the interplay between them. For each contribution, an explicit response function is derived. The Kerr-type nonlinearity of graphene is then numerically studied and it is demonstrated that the nonlinear refractive index of graphene can be tuned and enhanced by applying a gate voltage. It is also discussed that a strong Kerr nonlinearity can be achieved in a gated graphene monolayer. However, this nonlinearity is accompanied with a significant amount of absorption loss.

  12. Near-infrared diode laser based spectroscopic detection of ammonia: a comparative study of photoacoustic and direct optical absorption methods

    NASA Technical Reports Server (NTRS)

    Bozoki, Zoltan; Mohacsi, Arpad; Szabo, Gabor; Bor, Zsolt; Erdelyi, Miklos; Chen, Weidong; Tittel, Frank K.

    2002-01-01

    A photoacoustic spectroscopic (PAS) and a direct optical absorption spectroscopic (OAS) gas sensor, both using continuous-wave room-temperature diode lasers operating at 1531.8 nm, were compared on the basis of ammonia detection. Excellent linear correlation between the detector signals of the two systems was found. Although the physical properties and the mode of operation of both sensors were significantly different, their performances were found to be remarkably similar, with a sub-ppm level minimum detectable concentration of ammonia and a fast response time in the range of a few minutes.

  13. Enhancement of two photon absorption properties and intersystem crossing by charge transfer in pentaaryl boron-dipyrromethene (BODIPY) derivatives.

    PubMed

    Küçüköz, B; Sevinç, G; Yildiz, E; Karatay, A; Zhong, F; Yılmaz, H; Tutel, Y; Hayvalı, M; Zhao, J; Yaglioglu, H G

    2016-05-11

    Novel BODIPY derivatives containing N,N-diphenylamine, 4-methoxyphenyl, 2,4-dimethoxyphenyl, triphenylamine, and 1-pyrene moieties were designed and synthesized for the first time by employing the palladium-catalyzed Suzuki-Miyaura coupling on pentaaryl boron dipyrromethene compounds. The effect of various moieties and charge transfer on linear and nonlinear optical absorption was investigated. It was found that moieties with strong electron donor properties and long conjugation lengths increase charge transfer and enhance intersystem crossing in the investigated compounds. Besides, the investigated compounds showed strong two photon absorption properties at near infrared wavelengths (800 nm and 900 nm), which is required for two photon photodynamic therapy. Two photon absorption cross section values were found to be 83, 454, 331, 472 and 413 GM for , , , and compounds at 800 nm wavelength, respectively. The highest two-photon absorption cross-section value was obtained for the compound containing a triphenylamine moiety due to its more efficient charge transfer characteristics. Strong two-photon absorption properties in the near infrared region, efficient intersystem crossing and heavy atom free nature of the investigated compounds make them good candidates for two photon photodynamic therapy applications. We believe that this work will be one of the leading studies for two-photon photodynamic therapy applications of pentaaryl BODIPY derivatives. PMID:27138347

  14. Nonlinear optical properties of colloidal silver nanoparticles produced by laser ablation in liquids

    SciTech Connect

    Karavanskii, V A; Krasovskii, V I; Ivanchenko, P V; Simakin, Aleksandr V

    2004-07-31

    The optical and nonlinear optical properties of colloidal solutions of silver obtained by laser ablation in water and ethanol are studied. It is shown that freshly prepared colloids experience a full or partial sedimentation by changing their nonlinear optical properties. Aqueous colloids undergo a partial sedimentation and their nonlinear optical absorption changes to nonlinear optical transmission. The obtained results are interpreted using the Drude model for metal particles taking the particle size into account and can be explained by the sedimentation of larger silver particles accompanied by the formation of a stable colloid containing silver nanoparticles with a tentatively silver oxide shell. The characteristic size of particles forming such a stable colloid is determined and its optical nonlinearity is estimated. (nonlinear optical phenomena)

  15. Gas concentration measurement by optical similitude absorption spectroscopy: methodology and experimental demonstration.

    PubMed

    Anselmo, Christophe; Welschinger, Jean-Yves; Cariou, Jean-Pierre; Miffre, Alain; Rairoux, Patrick

    2016-06-13

    We propose a new methodology to measure gas concentration by light-absorption spectroscopy when the light source spectrum is larger than the spectral width of one or several molecular gas absorption lines. We named it optical similitude absorption spectroscopy (OSAS), as the gas concentration is derived from a similitude between the light source and the target gas spectra. The main OSAS-novelty lies in the development of a robust inversion methodology, based on the Newton-Raphson algorithm, which allows retrieving the target gas concentration from spectrally-integrated differential light-absorption measurements. As a proof, OSAS is applied in laboratory to the 2ν3 methane absorption band at 1.66 µm with uncertainties revealed by the Allan variance. OSAS has also been applied to non-dispersive infra-red and the optical correlation spectroscopy arrangements. This all-optics gas concentration retrieval does not require the use of a gas calibration cell and opens new tracks to atmospheric gas pollution and greenhouse gases sources monitoring. PMID:27410280

  16. Nonlinear optical properties and nonlinear optical probes of organic materials

    NASA Astrophysics Data System (ADS)

    Meredith, Gerald R.

    1992-02-01

    Nonlinear optical processes and electro-optical effects are expected to have increasing importance as the information age matures and photonics augment electronics in various high density and high bandwidth technologies. Whereas for electronics the emphasis is in construction of smaller device structures from a few parent materials, for organic materials the direction of materials research has been reversed. For some time it's been known that some molecular structures engender exceptionally large molecular nonlinear-polarization responses. If such molecules could be assembled in convenient, versatile, and reliable ways, the resulting materials would be very useful or even enabling in various photonics applications. The mature science and art of chemistry allows very good control over molecular composition and structure and, as will be illustrated in this talk, our knowledge of hyperpolarizability structure- property relationships is advancing rapidly. However, the science of fabrication and arrangement in molecular ensembles and polymers is rather primitive. Thus the goal to develop the appropriately structured materials for utilization in nonlinear and electro-optics has fostered the widespread use of nonlinear optical processes to probe the nature of supramolecular order and assembly. Examples of intrinsic and artificially assembled structures of crystals, molecular aggregates, polymeric orientational electrets and molecular mono- and multi-layer thin films will be shown. Nonlinear optical processes, primarily second-harmonic generation, provide unique probes of these structures, their assembly, and evolution.

  17. Double-integrating-sphere system for measuring the optical properties of tissue.

    PubMed

    Pickering, J W; Prahl, S A; van Wieringen, N; Beek, J F; Sterenborg, H J; van Gemert, M J

    1993-02-01

    A system is described and evaluated for the simultaneous measurement of the intrinsic optical properties of tissue: the scattering coefficient, the absorption coefficient, and the anisotropy factor. This system synthesizes the theory of two integrating spheres and an intervening scattering sample with the inverse adding-doubling algorithm, which employs the adding-doubling solution of the radiative transfer equation to determine the optical properties from the measurement of the light flux within each sphere and of the unscattered transmission. The optical properties may be determined simultaneously, which allows for measurements to be made while the sample undergoes heating, chemical change, or some otherexternal stimulus. An experimental validation of the system with tissue phantoms resulted in the determination of the optical properties with a < 5% deviation when the optical density was between 1 and 10 and the albedo was between 0.4 and 0.95. PMID:20802704

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Time-resolved chirp properties of semiconductor optical amplifiers in high-speed all-optical switches

    NASA Astrophysics Data System (ADS)

    Chen, Ligong; Lu, Rongguo; Zhang, Shangjian; Li, Jianfeng; Liu, Yong

    2013-03-01

    The chirp properties of semiconductor optical amplifiers in all-optical switches are numerically investigated using a field propagation model. The chirp dynamics in the blue-shift and red-shift sideband are analyzed under the injection of random optical pump pulses. We also analyze the impact of the blue-detuned filtering scheme that is used to eliminate the pattern effect and enhance the operating speed of the optical switching. The reason for overshoots in eye diagrams in the blue-detuned filtering scheme is explained. We find that overshoots result from the ultrafast blue chirp induced by carrier heating and two-phonon absorption. These results are very useful for semiconductor optical amplifier-based ultrafast all-optical signal processing.

  20. Atomistic simulations of the optical absorption of type-II CdSe/ZnTe superlattices

    PubMed Central

    2012-01-01

    We perform accurate tight binding simulations to design type-II short-period CdSe/ZnTe superlattices suited for photovoltaic applications. Absorption calculations demonstrate a very good agreement with optical results with threshold strongly depending on the chemical species near interfaces. PMID:23031315

  1. Optical absorption and luminescence in neutron-irradiated, silica-based fibers

    SciTech Connect

    Cooke, D.W.; Farnum, E.H.; Clinard, F.W.

    1995-04-01

    The objectives of this work are to assess the effects of thermal annealing and photobleaching on the optical absorption of neutron-irradiated, silica fibers of the type proposed for use in ITER diagnostics, and to measure x-ray induced luminescence of unirradiated (virgin) and neutron-irradiated fibers.

  2. LONG PATH DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER AND EPA-APPROVED FIXED POINT METHODS INTERCOMPARISON

    EPA Science Inventory

    Differential optical absorption spectrometry (DOAS) has been used by a number of investigators over the past 10 years to measure a wide range of gaseous air pollutants. ecently OPSIS AB, Lund, Sweden, has developed and made commercially available DOAS instrument that has a number...

  3. AIR QUALITY MONITORING IN ATLANTA WITH THE DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER

    EPA Science Inventory

    During July and August of 1990, a differential optical absorption spectrometer (DOAS) made by OPSIS Inc. was used to measure gaseous air pollutants over three separate open paths in Atlanta, GA. ver path 1 (1099 m) and path 2 (1824 m), ozone (O3), sulfur dioxide (SO2), nitrogen d...

  4. Improving optical absorptivity of natural dyes for fabrication of efficient dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Hemmatzadeh, Reza; Mohammadi, Ahmad

    2013-11-01

    Efficient and cheap dye-sensitized solar cells (DSSCs) were fabricated using natural dyes from Pastinaca sativa and Beta vulgaris. Natural dyes are environmentally and economically superior to ruthenium-based dyes because they are nontoxic and cheap. However, the conversion efficiency of dye-sensitized solar cells based on natural dyes is low. One way to improve the DSSC performance is to enhance the absorptivity of extracted dyes. We investigated the influence of various factors in the extraction process, such as utilization of different extraction approaches, the acidity of extraction solvent, and different compounds of solvents on the optical absorption spectra. It was found that we could considerably enhance the optical absorptivity of dye and consequently the performance of DSSC by choosing a proper mixture of ethanol and water for extracting solvent and also the acidity of dye solution.

  5. Cell damage in near-infrared multimode optical traps as a result of multiphoton absorption

    NASA Astrophysics Data System (ADS)

    König, K.; Liang, H.; Berns, M. W.; Tromberg, B. J.

    1996-07-01

    We report on cell damage of single cells confined in continuous-wave (cw), near-infrared (NIR) multimode optical traps as a result of multiphoton absorption phenomena. Trapping beams at NIR wavelengths less than 800 nm are capable of damaging cells through a two-photon absorption process. Cell damage is more pronounced in multimode cw traps compared with single-frequency true cw NIR traps because of transient power enhancement by longitudinal mode beating. Partial mode locking in tunable cw Ti:sapphire lasers used as trapping beam sources can produce unstable subnanosecond pulses at certain wavelengths that amplify multiphoton absorption effects significantly. We recommend the use of single-frequency long-wavelength NIR trapping beams for optical micromanipulation of vital cells.

  6. Optical properties of sulfur copolymers for infrared applications

    NASA Astrophysics Data System (ADS)

    Namnabat, Soha; Gabriel, Jared J.; Pyun, Jeffrey; Norwood, Robert A.

    2014-03-01

    The development of organic polymers with high refractive indices has been widely investigated, as a possible alternative to inorganic metal oxide, semiconductor, or chalcogenide-based materials for a variety of optical devices and components, such as waveguides, anti-reflective coatings, charge-coupled devices and fiber optic cables. In principle, organic-based polymers are attractive for these applications because of their low weight, ease of processing, mechanical toughness, and facile chemical variation using commercially available precursors. However, one of the fundamental challenges associated with organic polymers is their generally low refractive indices in comparison to their inorganic counterparts. Herein we report on the optical characterization of a new class of sulfur copolymers that are readily moldable, transparent above 500nm, possess high refractive index (n < 1.8) and take advantage of the low infrared absorption of S‒S bonds for potential use in the mid-infrared at 3-5 microns. These materials are largely made from elemental sulfur by an inverse vulcanization process; in the current study we focus on the properties of a chemically stable, branched copolymer of poly(sulfur-random-1,3-diisopropenylbenzene) (poly(S-r-DIB). Copolymers with elemental sulfur content ranging from 50% to 80% by weight were studied by UV-VIS spectroscopy, FTIR, and prism coupling for refractive index measurement. Clear correlation between material composition and the optical properties was established, confirming that the high polarizability of the sulfur atom leads to high refractive index while also maintaining low optical loss. Applications of the materials for bulk optics, high-density photonic circuits, and infrared components will also be discussed.

  7. Extended Pre-Transit Structures and the Exosphere Detected for HD189733b in Optical Hydrogen Balmer Line Absorption

    NASA Astrophysics Data System (ADS)

    Redfield, Seth; Cauley, P. Wilson; Jensen, Adam G.; Barman, Travis; Endl, Michael; Cochran, William

    2015-12-01

    We present two separate observations of HD189733b in the three strongest hydrogen Balmer lines (H-alpha, H-beta, and H-gamma), with HiRES on Keck I that show definitive in-transit absorption, confirming the detection with the HET by Jensen et al. (2012), as well as, significant pre-transit absorption. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a planetary bow shock, however our observations are the first to densely time-sample and redundantly detect these extended planetary structures. While our first observations (obtained in 2013 and presented in Cauley et al. 2015), were consistent with a bow shock, our subsequent observation taken in August 2015 show pre-transit absorption but with a pattern that is inconsistent with the 2013 model. Instead, the observations indicate significant variability in the strength and timing of the pre-transit absorption. We also find differences in the strength of the in-transit exospheric absorption as well. These changes could be indicative of variability in the extreme stellar wind properties found at just 8 stellar radii, which could drive the extended atmospheric interaction between star and planet. The pre-transit absorption in 2013 was first observed 65 minutes prior to transit (corresponding to a linear distance of ~7 planetary radii), although it could have started earlier. The pre-transit signal in 2015, which is well sampled, is first detected 165 minutes prior to transit (a linear distance of ~17 planetary radii). The line shape of the pre-transit feature and the shape of the time series absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around the exoplanet. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. If part of this extended structure is a bow shock mediated

  8. Quantum optical properties in plasmonic systems

    SciTech Connect

    Ooi, C. H. Raymond

    2015-04-24

    Plasmonic metallic particle (MP) can affect the optical properties of a quantum system (QS) in a remarkable way. We develop a general quantum nonlinear formalism with exact vectorial description for the scattered photons by the QS. The formalism enables us to study the variations of the dielectric function and photon spectrum of the QS with the particle distance between QS and MP, exciting laser direction, polarization and phase in the presence of surface plasmon resonance (SPR) in the MP. The quantum formalism also serves as a powerful tool for studying the effects of these parameters on the nonclassical properties of the scattered photons. The plasmonic effect of nanoparticles has promising possibilities as it provides a new way for manipulating quantum optical properties of light in nanophotonic systems.

  9. Water absorption properties of ultrasonic treated brown rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To understand the effect of ultrasonic treated on brown rice, it is important to research the water absorption processing of brown rice before and after ultrasonic treatment. The objective of this study was investigate and modeling water absorption characteristics of brown rice using Peleg’s equatio...

  10. Optical absorption of neutron-irradiated silica fibers

    SciTech Connect

    Cooke, D.W.; Farnum, E.H.; Bennett, B.L.

    1996-10-01

    Induced-loss spectra of silica-based optical fibers exposed to high (10{sup 23} n-m{sup {minus}2}) and low (10{sup 21} n-m{sup {minus}2}) fluences of neutrons at the Los Alamos Spallation Radiation Effects Facility (LASREF) have been measured. Two types of fibers consisting of a pure fused silica core with fluorine-doped ({approximately}4 mole %) cladding were obtained from Fiberguide Industries and used in the as-received condition. Anhydroguide{trademark} and superguide{trademark} fibers contained less than 1 ppm, and 600 to 800 ppm of OH, respectively. The data suggest that presently available silica fibers can be used in plasma diagnostics, but the choice and suitability depends upon the spectral region of interest. Low-OH content fibers can be used for diagnostic purposes in the interval {approximately}800 to 1400 mn if the exposure is to high-fluence neutrons. For low-fluence neutron exposures, the low-OH content fibers are best suited for use in the interval {approximately}800 to 2000 nm, and the high-OH content fibers are the choice for the interval {approximately}400 to 800 nm.

  11. Potassium doping: Tuning the optical properties of graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Qian, Fuli; Li, Xueming; Tang, Libin; Lai, Sin Ki; Lu, Chaoyu; Lau, Shu Ping

    2016-07-01

    Doping with hetero-atoms is an effective way to tune the properties of graphene quantum dots (GQDs). Here, potassium-doped GQDs (K-GQDs) are synthesized by a one-pot hydrothermal treatment of sucrose and potassium hydroxide solution. Optical properties of the GQDs are altered as a result of K-doping. The absorption peaks exhibit a blue shift. Multiple photoluminescence (PL) peaks are observed as the excitation wavelength is varied from 380 nm to 620 nm. New energy levels are introduced into the K-GQDs and provide alternative electron transition pathways. The maximum PL intensity of the K-GQDs is obtained at an excitation wavelength of 480 nm which is distinct from the undoped GQDs (375 nm). The strong PL of the K-GQDs at the longer emission wavelengths is expected to make K-GQDs more suitable for bioimaging and optoelectronic applications.

  12. Observation of temperature dependence of the IR hydroxyl absorption bands in silica optical fiber

    NASA Astrophysics Data System (ADS)

    Yu, Li; Bonnell, Elizabeth; Homa, Daniel; Pickrell, Gary; Wang, Anbo; Ohodnicki, P. R.; Woodruff, Steven; Chorpening, Benjamin; Buric, Michael

    2016-07-01

    This study reports on the temperature dependent behavior of silica based optical fibers upon exposure to high temperatures in hydrogen and ambient air. The hydroxyl absorption bands in the wavelength range of 1000-2500 nm of commercially available multimode fibers with pure silica and germanium doped cores were examined in the temperature range of 20-800 °C. Two hydroxyl-related infrared absorption bands were observed: ∼2200 nm assigned to the combination of the vibration mode of Si-OH bending and the fundamental hydroxyl stretching mode, and ∼1390 nm assigned to the first overtone of the hydroxyl stretching. The absorption in the 2200 nm band decreased in intensity, while the 1390 nm absorption band shifted to longer wavelengths with an increase in temperature. The observed phenomena were reversible with temperature and suspected to be due, in part, to the conversion of the OH spectral components into each other and structural relaxation.

  13. Optical design of transparent metal grids for plasmonic absorption enhancement in ultrathin organic solar cells.

    PubMed

    Kim, Inho; Lee, Taek Seong; Jeong, Doo Seok; Lee, Wook Seong; Kim, Won Mok; Lee, Kyeong-Seok

    2013-07-01

    Transparent metal grid combining with plasmonic absorption enhancement is a promising replacement to indium tin oxide thin films. We numerically demonstrate metal grids in one or two dimension lead to plasmonic absorption enhancements in ultrathin organic solar cells. In this paper, we study optical design of metal grids for plasmonic light trapping and identify different plasmonic modes of the surface plasmon polaritons excited at the interfaces of glass/metal grids, metal grids/active layers, and the localized surface plasmon resonance of the metal grids using numerical calculations. One dimension metal grids with the optimal design of a width and a period lead to the absorption enhancement in the ultrathin active layers of 20 nm thickness by a factor of 2.6 under transverse electric polarized light compared to the case without the metal grids. Similarly, two dimensional metal grids provide the absorption enhancement by a factor of 1.8 under randomly polarized light. PMID:24104493

  14. Optical Transmission Properties of Dielectric Aperture Arrays

    NASA Astrophysics Data System (ADS)

    Yang, Tao

    Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index

  15. An integrated fiber-optic probe combined with support vector regression for fast estimation of optical properties of turbid media.

    PubMed

    Zhou, Yang; Fu, Xiaping; Ying, Yibin; Fang, Zhenhuan

    2015-06-23

    A fiber-optic probe system was developed to estimate the optical properties of turbid media based on spatially resolved diffuse reflectance. Because of the limitations in numerical calculation of radiative transfer equation (RTE), diffusion approximation (DA) and Monte Carlo simulations (MC), support vector regression (SVR) was introduced to model the relationship between diffuse reflectance values and optical properties. The SVR models of four collection fibers were trained by phantoms in calibration set with a wide range of optical properties which represented products of different applications, then the optical properties of phantoms in prediction set were predicted after an optimal searching on SVR models. The results indicated that the SVR model was capable of describing the relationship with little deviation in forward validation. The correlation coefficient (R) of reduced scattering coefficient μ'(s) and absorption coefficient μ(a) in the prediction set were 0.9907 and 0.9980, respectively. The root mean square errors of prediction (RMSEP) of μ'(s) and μ(a) in inverse validation were 0.411 cm(-1) and 0.338 cm(-1), respectively. The results indicated that the integrated fiber-optic probe system combined with SVR model were suitable for fast and accurate estimation of optical properties of turbid media based on spatially resolved diffuse reflectance. PMID:26092344

  16. Influences of hydrogen dilution on microstructure and optical absorption characteristics of nc-SiOx:H film

    NASA Astrophysics Data System (ADS)

    Zhao, Wei; Du, Lin-Yuan; Jiang, Zhao-Yi; Yin, Chen-Chen; Yu, Wei; Fu, Guang-Sheng

    2015-10-01

    By using the plasma enhanced chemical vapor deposition (PECVD) technique, amorphous silicon oxide films containing nanocrystalline silicon grain (nc-SiOx:H) are deposited, and the bonding configurations and optical absorption properties of the films are investigated. The grain size can be well controlled by varying the hydrogen and oxygen content, and the largest size is obtained when the hydrogen dilution ratio R is 33. The results show that the crystallinity and the grain size of the film first increased and then decreased as R increased. The highest degree of crystallinity is obtained at R = 30. The analyses of bonding characteristics and light absorption characteristics show that the incorporation of hydrogen leads to an increase of overall bonding oxygen content in the film, and the film porosity first increases and then decreases. When R = 30, the film can be more compact, the optical absorption edge of the film is blue shifted, and the film has a lower activation energy. Project supported by the Key Basic Research Project of Hebei Province, China (Grant No. 12963930D) and the Natural Science Foundation of Hebei Province, China (Grant Nos. F2013201250 and B2012402011).

  17. Photo-physical properties and triplet-triplet absorption of platinum(II) acetylides in solid PMMA matrices

    NASA Astrophysics Data System (ADS)

    Glimsdal, Eirik; Westlund, Robert; Lindgren, Mikael

    2009-05-01

    Because of their strong nonlinear optical properties, Platinum(II) acetylides are investigated as potential chromophores for optical power limiting (OPL) applications. The strong excited state absorption and efficient intersystem crossing to the triplet states in these materials are desired properties for good OPL performance. We recently reported on OPL and photo-physical properties of Pt(II)-acetylide chromophores in solution, modified with thiophenyl or triazole groups. [R. Westlund et al. J. Mater. Chem. 18, 166 (2008); E. Glimsdal et al. Proc. SPIE 6740, 67400M (2007)] The chromophores were later incorporated into poly(methyl-methacrylate) (PMMA) glasses. A variety of doped organic solids were prepared, reaching concentrations of up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices proved that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photo-physical properties (absorption, emission and inter-system crossing) observed for the solute molecules in THF are maintained also in the solid state. In particular, the phosphorescence lifetime stays in the order of μs to ms, just as in the oxygen evacuated liquid samples. Also, the wavelength dependence and time-dynamics of the triplet absorption spectra of the dyes, dissolved in THF solution and dispersed in solid PMMA matrices, were investigated and compared. Ground state UV absorption spectra between 300 and 420 nm have corresponding broad band visible triplet-triplet absorption between 400 and 800 nm. The triplet state extinction coefficients were determined to be in the order of 104 M-1cm-1.

  18. Morphology and Optical Properties of Mixed Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Fard, Mehrnoush M.; Krieger, Ulrich; Rudich, Yinon; Marcolli, Claudia; Peter, Thomas

    2015-04-01

    Experiments and modeling studies have shown that deliquesced aerosols can be present not only as one-phase system containing organics, inorganic salts and water, but often as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase 1,2. Recent laboratory studies conducted with model mixtures representing tropospheric aerosols1,2,3, secondary organic aerosol (SOA) from smog chamber experiments4, and field measurements5 suggest that liquid- liquid phase separations (LLPS) is indeed a common phenomenon in mixed organic/ ammonium sulfate (AS) particles. During LLPS, particles may adopt different morphologies mainly core- shell and partially engulfed. A core- shell configuration will have consequences for heterogeneous chemistry and hygroscopicity and as a result will alter the optical properties of the particles since the aqueous inorganic-rich phase will be totally enclosed by a probably highly viscous organic coating with low diffusivity for reactants and water. The primary objective of this project is to establish a method for investigating the morphology of mixed inorganic and absorbing organic compounds of atmospheric relevance and study their radiative properties before, during, and after phase transitions mainly during LLPS. This will be the first study looking into the radiative effect of LLPS in detail. In this first experiment, the behavior of single droplets of carminic acid (CA)/ AS/ H2O mixture was monitored during relative humidity (RH) cycles using optical microscopy. The same mixture particle was levitated in an electrodynamic balance (EDB) and the change in its absorption properties was measured at varying RH. We also intend to determine the occurrence of LLPS in accumulation- sized particles and the change in their absorption using a cavity ring down aerosol spectrometer. If LLPS alters the absorptive properties of the suggested model aerosols significantly, absorption measurements of accumulation mode

  19. Nonlinear optical properties of zinc oxide doped bismuth thin films using Z-scan technique

    NASA Astrophysics Data System (ADS)

    Abed, S.; Bouchouit, K.; Aida, M. S.; Taboukhat, S.; Sofiani, Z.; Kulyk, B.; Figa, V.

    2016-06-01

    ZnO doped Bi thin films were grown on glass substrates by spray ultrasonic technique. This paper presents the effect of Bi doping concentration on structural and nonlinear optical properties of zinc oxide thin films. These thin films were characterized by X-ray diffractometer technique. XRD analysis revealed that the ZnO:Bi thin films indicated good preferential orientation along c-axis perpendicular to the substrate. The nonlinear optical properties such as nonlinear absorption coefficient (β) and third order nonlinear susceptibility (Imχ(3)) are investigated. The calculations have been performed with a Z scan technique using Nd:YAG laser emitting 532 nm. The reverse saturable absorption (RSA) mechanism was responsible for the optical limiting effect. The results suggest that this material considered as a promising candidate for future optical device applications.

  20. Optical absorption in lithiated tungsten oxide thin films: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Berggren, Lars; Jonsson, Jacob C.; Niklasson, Gunnar A.

    2007-10-01

    Amorphous tungsten oxide exhibits electrochromism when intercalated with protons, lithium, sodium, and other ions. Thin films of the material were prepared by dc magnetron sputtering and then electrochemically intercalated with lithium. The optical absorption in the wavelength range of 300-2500nm was measured for a number of lithium concentrations. The optical absorption shows a maximum for lithium/tungsten ratios of 0.3-0.5. The optical spectra can be fitted by a superposition of three Gaussian peaks, representing the three possible electronic transitions between W6+, W5+, and W4+ sites. The variation of the peak strength with lithium concentration is consistent with an extended site-saturation theory.