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Sample records for optical absorption properties

  1. Optical absorption and scattering properties in the East China Sea

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan; He, Xian-qiang; Chen, Xiao-yan; Hao, Zeng-zhou; Huang, Haiqing; Zhu, Qiankun

    2011-11-01

    The absorption and particulate backscattering coefficients are the basic parameters of the water inherent optical properties (IOPs), which are also the basic parameters for the development and validation of the semi-analysis models of the ocean color remote sensing. In this work, the absorption and backscattering coefficients in the East China Sea (ECS) were measured in the summer and winter of 2009 using the three in-situ optical instruments, including the WET Labs acs, and the HOBI Labs HydroScat-6. Based on the in-situ measured data, the distribution of the absorption and backscattering coefficients in the ECS are analyzed. The results show that in the summer the water absorption coefficient at 440nm (a(440nm),excluding the absorption of the pure sea water) in the surface layer is ranged from 0.022 to 0.067 m-1, and the particulate backscattering coefficient at 442nm(bbp(442nm), is between 0.00064 and 0.03274 m-1. As a whole, both of the absorption and backscattering coefficients decrease with the offshore direction, and the high values located at the mouth of Changjiang River. In the winter, a(440nm) is between 0.051 and 0.887 m-1, and bbp(442nm) is ranged from 0.000639 to 0.14614 m-1 at the surface layer. The spatial distributions in winter are similar as the summer, with the high value in the coast and low value in the offshore. The absorption and backscattering coefficients in winter are significantly larger than the summer's, especially in coastal area near the mouth of Changjiang River, which maybe caused by the southward Fujian-Zhejiang coastal current occurring in winter. As the vertical profile distributions, we find that both of the absorption and backscattering coefficients present a layer structure, which caused by the stratification of the sea water in the summer; while in the winter, affected by the strong wind disturbing, both of the absorption and backscattering coefficients are thoroughly vertical mixing. To our knowledge, it is the first time

  2. Nanofluid optical property characterization: towards efficient direct absorption solar collectors.

    PubMed

    Taylor, Robert A; Phelan, Patrick E; Otanicar, Todd P; Adrian, Ronald; Prasher, Ravi

    2011-03-15

    Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

  3. Nanofluid optical property characterization: towards efficient direct absorption solar collectors

    PubMed Central

    2011-01-01

    Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase. PMID:21711750

  4. 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...

  5. 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

  6. 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.

  7. 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.

  8. The tunable electronic structure and optic absorption properties of phosphorene by a normally applied electric field

    NASA Astrophysics Data System (ADS)

    Yang, Mou; Duan, Hou-Jian; Wang, Rui-Qiang

    2016-10-01

    We studied the electronic structure and optical absorption properties of phosphorene (a monolayer black phosphorus) under a normally applied electric field. The electric field enlarges the energy gap, weakens the effective mass anisotropy, and increases the effective mass component along the armchair direction (x-direction) for both conduction and valence bands but provides little change to the component along the zigzag direction (y-direction). The band edge optical absorption is completely polarized in the x-direction, and decreases when increasing the electric field. If the exciting frequency is beyond the energy gap, the absorption for the y-polarized light becomes nonzero, but the absorption is still highly polarized.

  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. 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.

  12. 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.

  13. 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

  14. 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.

  15. Optical absorption and emission properties of Nd3+-doped oxyfluorosilicate glasses for solid state lasers

    NASA Astrophysics Data System (ADS)

    Ramachari, D.; Rama Moorthy, L.; Jayasankar, C. K.

    2014-11-01

    Optical absorption and near-infrared luminescent properties of Nd3+ ions doped oxyfluorosilicate (NKZLSNd) glasses were investigated. Raman spectrum was recorded to investigate the structural properties of NKZLSNd glasses. The Judd-Ofelt theory (JO) has been applied to the absorption spectrum of 1.0 mol% Nd3+-doped oxyfluorosilicate glass to derive the JO intensity parameters (Ωλ), which are in turn used to calculate the radiative properties of Nd3+ ions luminescent levels. The near-infrared emission spectra recorded with 808 nm laser diode excitation revealed the effective bandwidths values around 30-40 nm for the 4F3/2 level of Nd3+-doped oxyfluorosilicate glasses. The measured decay times of 4F3/2 level decreased with increasing Nd3+ ions concentration due to the concentration quenching.

  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. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. '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.

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Optical absorption measurements and quantum-chemical simulations of optical properties of novel fluoro derivatives of pyrazoloquinoline

    NASA Astrophysics Data System (ADS)

    Brik, M. G.; Kuznik, W.; Gondek, E.; Kityk, I. V.; Uchacz, T.; Szlachcic, P.; Jarosz, B.; Plucinski, K. J.

    2010-05-01

    The results of experimental research and quantum-chemical simulations of the absorption spectra of 1-(4-fluorophenyl)-3,4-diphenyl, 3-(4-fluorophenyl)-1,4-diphenyl, and 4-(4-fluorophenyl)-1,3-diphenyl-pyrazolo[3,4- b] quinoline are presented. Although the fluorine atom is located on different phenyl rings in these molecules, the absorption spectra do not differ significantly. Semi-empirical AM1, PM3 and RM1 methods, as well as ab initio ADF code-based calculations were used to optimize geometry, calculate the infrared and visible spectra of the afore mentioned compounds and analyze the molecular orbitals schemes. The results of calculations are in good agreement with the experimental data. It was also demonstrated that the positions of the fluorescence maxima depend significantly on the solvent (contrary to the absorption spectra), in which the molecules are embedded, which allows for manipulating with fluorescence properties of the synthesized molecules by changing the solvent.

  12. 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.

  13. 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.

  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.

  15. 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.

  16. 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...

  17. Nonlinear optical absorption and switching properties of gold nanoparticle doped SiO2-TiO2 sol-gel films.

    PubMed

    Venkatram, N; Kumar, R Sai Santosh; Rao, D Narayana; Medda, S K; De, Sucheta; De, Goutam

    2006-07-01

    The nonlinear optical absorption and switching properties of sol-gel derived of Au nanoparticle doped SiO2-TiO2 sol-gel films having different Au-surface plasmon absorption positions are reported in this paper. The Au nanoparticles are embedded in SiO2 and SiO2-TiO2 mixed glassy film matrices with different refractive index values. To study the nonlinear absorption properties, lasers with three different wavelengths are used. The optical switching behavior is studied by using the pump-probe technique with 532 nm as the excitation wavelength. Ground state conduction band, surface plasmon band, and the free carrier band are taken as three level model to explain theoretically the obtained RSA and SA behaviors.

  18. 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+}.

  19. 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

  20. 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.

  1. Development of an in-situ structure/photo-absorption coincident measurement system for precise structure-optical property relationship research at SPring-8

    NASA Astrophysics Data System (ADS)

    Kim, Jungeun; Kato, Kenichi; Moritomo, Yutaka; Takata, Masaki

    2010-06-01

    We have developed the structure and optical property coincident measurement system equipped with the photo-absorption system to the Large Debye-Scherrer Camera at BL44B2 of the SPring-8. Both photo-absorption detecting systems, the Si pin-photo diode for a 532 nm CW laser and the absorption spectrum covered the range of UV-IR (200˜1400 nm) for a white beam, are adopted. In order to verify the coincident measurement system, the X-ray powder diffraction and photo-absorption with the cyanide complex were performed individually and simultaneously under the temperature changes. As a result, the coincident measurement system performed successfully the one-to-one corresponding measurement between X-ray diffraction and photo-absorption. In addition, the monitoring of the photo-absorption informed us the property change of the material for the measurement condition and the sample transformation by temperature, laser etc. as well as damage by high-brilliance synchrotron radiation X-ray beam.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. Optical absorption spectra of pairs of small metal particles

    NASA Astrophysics Data System (ADS)

    Quinten, M.; Kreibig, U.; Schönauer, D.; Genzel, L.

    1985-06-01

    The influence of plasma resonance coupling in small Au particle pairs on their optical properties was calculated including retardation effects. The latter prove to be important for sizes above 15 nm. For pairs of smaller particles a Maxwell-Garnett formula is derived and absorption spectra are calculated explicitly. Comparison with optical absorption spectra measured on aggregated Au particle hydrosols, gives good agreement concerning the splitting up of the dipolar single-particle plasma resonance band.

  11. Electric modulation of optical absorption in nanowires

    NASA Astrophysics Data System (ADS)

    Sakr, M. R.

    2016-11-01

    We have calculated the effect of an external electric field on the intersubband optical absorption of a nanowire subjected to a perpendicular magnetic field and Rashba effect. The absorption peaks due to optical transitions that are forbidden in the absence of the intersubband coupling experience strong amplitude modulation. This effect is quadratic in electric fields applied along the direction of quantum confinement or perpendicularly to tune the Rashba parameter. The electric field also induces frequency modulation in the associated spectrum. On the other hand, transitions that are normally allowed show, to a large extent, a parallel band effect, and accordingly they are responsible for strong optical absorption.

  12. Distance redshift from an optical metric that includes absorption

    SciTech Connect

    Chen, B.; Kantowski, R.

    2009-08-15

    We show that it is possible to equate the intensity reduction of a light wave caused by weak absorption with a geometrical reduction in intensity caused by a 'transverse' conformal transformation of the spacetime metric in which the wave travels. We are consequently able to modify Gordon's optical metric to account for electromagnetic properties of ponderable material whose properties include both refraction and absorption. Unlike refraction alone, however, including absorption requires a modification of the optical metric that depends on the eikonal of the wave itself. We derive the distance-redshift relation from the modified optical metric for Friedman-Lemaitre-Robertson-Walker spacetimes whose cosmic fluid has associated refraction and absorption coefficients. We then fit the current supernovae data and provide an alternate explanation (other than dark energy) of the apparent acceleration of the Universe.

  13. 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.

  14. [Variations in the optical absorption and attenuation properties of cultured phytoplankton and their relationships with cell size].

    PubMed

    Zhou, Wen; Sun, Zhao-Hua; Cao, Wen-Xi; Wang, Gui-Fen

    2012-12-01

    The spectral absorption and attenuation coefficients of 16 phytoplankton species were measured in the laboratory using acs instrument. Ancillary measurements included particle size distribution and chlorophyll a concentration (Chl a). The results indicated that both algal cell size and Chl a were the two major factors dominating the magnitudes of the spectral absorption and attenuation coefficients. The spectral behaviors of attenuation spectra were dominated by algal cell size, the relationship of them didn't follow the monotonic function. Both the ratio of absorption in blue and red waveband and the spectral slope of absorption coefficient were influenced by the product of algal cell density and squares of cell size rather than algal cell size alone. The relationship between algal cell size and both absorption and attenuation spectra would be interpreted by Mie theory for homogenous sphere, which imply that the heterogeneity and non-spherical shape in algal cell morphology and internal structure have little effect on the inherent association among them.

  15. Extraordinary Optical Absorption through Plasmonic Subwavelength Slits

    NASA Astrophysics Data System (ADS)

    White, Justin; Veronis, Georgios; Yu, Zongfu; Barnard, Edward; Chandran, Anu; Fan, Shanhui; Brongersma, Mark

    2009-03-01

    We report on the ability of resonant plasmonic slits to efficiently concentrate electromagnetic energy into a nanoscale volume of absorbing material placed inside or right behind the slit. This gives rise to extraordinary optical absorption (EOA) characterized by an absorption enhancement factor that well-exceeds the enhancements seen for extraordinary optical transmission (EOT) through slits. A semi-analytic Fabry-Perot model for the resonant absorption is developed and shown to quantitatively agree with full-field simulations. We show that absorption enhancements of nearly 1000% can be realized at 633nm for slits in aluminum films filled with silicon. This effect can be utilized in a wide range of applications, including high speed photodetectors, optical lithography and recording, and biosensors.

  16. Optical properties and chemical composition of aerosol particles at an urban location: An estimation of the aerosol mass scattering and absorption efficiencies

    NASA Astrophysics Data System (ADS)

    Titos, G.; Foyo-Moreno, I.; Lyamani, H.; Querol, X.; Alastuey, A.; Alados-Arboledas, L.

    2012-02-01

    We investigated aerosol optical properties, mass concentration and chemical composition over a 1 year period (from March 2006 to February 2007) at an urban site in Southern Spain (Granada, 37.18°N, 3.58°W, 680 m above sea level). Light-scattering and absorption measurements were performed using an integrating nephelometer and a MultiAngle Absorption Photometer (MAAP), respectively, with no aerosol size cut-off and without any conditioning of the sampled air. PM10 and PM1 (ambient air levels of atmospheric particulate matter finer than 10 and 1 microns) were collected with two high volume samplers, and the chemical composition was investigated for all samples. Relative humidity (RH) within the nephelometer was below 50% and the weighting of the filters was also at RH of 50%. PM10 and PM1 mass concentrations showed a mean value of 44 ± 19 μg/m3 and 15 ± 7 μg/m3, respectively. The mineral matter was the major constituent of the PM10-1 fraction (contributing more than 58%) whereas organic matter and elemental carbon (OM+EC) contributed the most to the PM1 fraction (around 43%). The absorption coefficient at 550 nm showed a mean value of 24 ± 9 Mm-1 and the scattering coefficient at 550 nm presented a mean value of 61 ± 25 Mm-1, typical of urban areas. Both the scattering and the absorption coefficients exhibited the highest values during winter and the lowest during summer, due to the increase in the anthropogenic contribution and the lower development of the convective mixing layer during winter. A very low mean value of the single scattering albedo of 0.71 ± 0.07 at 550 nm was calculated, suggesting that urban aerosols in this site contain a large fraction of absorbing material. Mass scattering and absorption efficiencies of PM10 particles exhibited larger values during winter and lower during summer, showing a similar trend to PM1 and opposite to PM10-1. This seasonality is therefore influenced by the variations on PM composition. In addition, the mass

  17. 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

  18. 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.

  19. Stochastic Approach to Phonon-Assisted Optical Absorption

    NASA Astrophysics Data System (ADS)

    Zacharias, Marios; Patrick, Christopher E.; Giustino, Feliciano

    2015-10-01

    We develop a first-principles theory of phonon-assisted optical absorption in semiconductors and insulators which incorporates the temperature dependence of the electronic structure. We show that the Hall-Bardeen-Blatt theory of indirect optical absorption and the Allen-Heine theory of temperature-dependent band structures can be derived from the present formalism by retaining only one-phonon processes. We demonstrate this method by calculating the optical absorption coefficient of silicon using an importance sampling Monte Carlo scheme, and we obtain temperature-dependent line shapes and band gaps in good agreement with experiment. The present approach opens the way to predictive calculations of the optical properties of solids at finite temperature.

  20. 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.

  1. 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

  2. Light absorption properties and absorption budget of Southeast Pacific waters

    NASA Astrophysics Data System (ADS)

    Bricaud, Annick; Babin, Marcel; Claustre, Hervé; Ras, JoséPhine; TièChe, Fanny

    2010-08-01

    Absorption coefficients of phytoplankton, nonalgal particles (NAPs), and colored dissolved organic matter (CDOM), and their relative contributions to total light absorption, are essential variables for bio-optical and biogeochemical models. However, their actual variations in the open ocean remain poorly documented, particularly for clear waters because of the difficulty in measuring very low absorption coefficients. The Biogeochemistry and Optics South Pacific Experiment (BIOSOPE) cruise investigated a large range of oceanic regimes, from mesotrophic waters around the Marquesas Islands to hyperoligotrophic waters in the subtropical gyre and eutrophic waters in the upwelling area off Chile. The spectral absorption coefficients of phytoplankton and NAPs were determined using the filter technique, while the CDOM absorption coefficients were measured using a 2 m capillary waveguide. Over the whole transect, the absorption coefficients of both dissolved and particulate components covered approximately two orders of magnitude; in the gyre, they were among the lowest ever reported for open ocean waters. In the oligotrophic and mesotrophic waters, absorption coefficients of phytoplankton and NAPs were notably lower than those measured in other oceanic areas with similar chlorophyll contents, indicating some deviation from the standard chlorophyll-absorption relationships. The contribution of absorption by NAPs to total particulate absorption showed large vertical and horizontal variations. CDOM absorption coefficients covaried with algal biomass, albeit with a high scatter. The spectral slopes of both NAP and CDOM absorption revealed structured spatial variability in relation with the trophic conditions. The relative contributions of each component to total nonwater absorption were (at a given wavelength) weakly variable over the transect, at least within the euphotic layer.

  3. 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.

  4. 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.

  5. 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

  6. Climatology of aerosol optical properties and black carbon mass absorption cross section at a remote high-altitude site in the western Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Pandolfi, M.; Ripoll, A.; Querol, X.; Alastuey, A.

    2014-06-01

    Aerosol light scattering (σsp), backscattering (σbsp) and absorption (σap) were measured at Montsec (MSC; 42°3' N, 0°44' E, 1570 m a.s.l.), a remote high-altitude site in the western Mediterranean Basin. Mean (±SD) σsp, σbsp and σap were 18.9 ± 20.8, 2.6 ± 2.8 and 1.5 ± 1.4 Mm-1, respectively at 635 nm during the period under study (June 2011-June 2013). Mean values of single-scattering albedo (SSA, 635 nm), the scattering Ångström exponent (SAE, 450-635 nm), backscatter-to-scatter ratio (B / S, 635 nm), asymmetry parameter (g, 635 nm), black carbon mass absorption cross section (MAC, 637 nm) and PM2.5 mass scattering cross section (MSCS, 635 nm) were 0.92 ± 0.03, 1.56 ± 0.88, 0.16 ± 0.09, 0.53 ± 0.16, 10.9 ± 3.5 m2 g-1 and 2.5 ± 1.3 m2 g-1, respectively. The scattering measurements performed at MSC were in the medium/upper range of values reported by Andrews et al. (2011) for other mountaintop sites in Europe due to the frequent regional recirculation scenarios (SREG) and Saharan dust episodes (NAF) occurring mostly in spring/summer and causing the presence of polluted layers at the MSC altitude. However, the development of upslope winds and the possible presence of planetary boundary layer air at MSC altitude in summer may also have contributed to the high scattering observed. Under these summer conditions no clear diurnal cycles were observed for the measured extensive aerosol optical properties (σsp, σbsp and σap). Conversely, low σsp and σap at MSC were measured during Atlantic advections (AA) and winter regional anticyclonic episodes (WREG) typically observed during the cold season in the western Mediterranean. Therefore, a season-dependent decrease in the magnitude of aerosol extensive properties was observed when MSC was in the free troposphere, with the highest free-troposphere vs. all-data difference observed in winter and the lowest in spring/summer. The location of MSC station allowed for a reliable characterization of aerosols

  7. 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.

  8. Optical absorption coefficients of pure water

    NASA Astrophysics Data System (ADS)

    Lu, Zheng; Zhao, Xianzhen; Fry, Edward S.

    2002-10-01

    The integrating cavity absorption meter(ICAM), which is independent of scattering effect, is used to measure the absolute values of small optical absorption coefficients of liquid. A modified ICAM is being used to measure the absorption of water in the wavelength range 300 to 700 nm. The ultrapure water produced by a two-stages water purification system reaches Type I quality. This is equal to or better than ASTM,CAP and NCCLS water quality standards. To avoid the fact that dissolved oxygen absorbs ultraviolet light due to the photochemical effect, the water sample is delivered through a nitrogen sealed system which will prevent the sample from contacting with oxygen. A compassion of our absorption spectrum with other existing data is given.

  9. 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.

  10. 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).

  11. 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

  12. 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.

  13. Optical properties of ALON (aluminum oxynitride)

    NASA Astrophysics Data System (ADS)

    Hartnett, T. M.; Bernstein, S. D.; Maguire, E. A.; Tustison, R. W.

    1998-06-01

    The optical properties of ALON (aluminum oxynitride) are presented. Optical scatter and index of refraction, and absorption of several different compositions of ALON are compared. The temperature dependence of emissivity of ALON was measured in the temperature range 46°C to 1200°C.

  14. 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.

  15. Manifestation of the Kondo effect in nonlinear optical absorption

    NASA Astrophysics Data System (ADS)

    Shahbazyan, T. V.; Perakis, I. E.; Raikh, M. E.

    2000-03-01

    We study the nonlinear optical absorption due to transitions from a deep impurity to states above a Fermi sea. Previous calculations(See, e.g., S. Mukamel, Principles of Nonlinear Optical Spectroscopy), (Oxford University Press, 1995). of \\chi^(3) included contributions from virtual processes involving doubly occupied impurity state. This indicates the necessity of incorporating the Hubbard repulsion of electrons at the impurity in calculation of nonlinear optical properties. Detailed calculations are performed for pump-probe spectrum. We demonstrate that Hubbard-repulsion-induced suppression of two-electron states leads to the divergency in \\chi^(3) near the absorption threshold. The origin of this divergency lies in the Kondo-physics;(See, e.g., A. C. Hewson, The Kondo Problem to Heavy Fermions), (Cambridge University Press, 1993). a monochromatic optical field induces the coupling between the impurity and conduction band states that is similar to the hybridization terms in the Anderson model.^3 Remarkably, for light-induced Kondo-absorption, the Kondo temperature can be tuned by the intensity and frequency of the pump field.

  16. Differential optical spectroscopy for absorption characterization of scattering media.

    PubMed

    Billet, Cyril; Sablong, Raphaël

    2007-11-15

    Reflectance techniques are commonly used to characterize the optical properties of tissues. However, the precise determination of local chromophore concentrations in turbid media is usually difficult because of the nonlinear dependence of light intensity as a function of scattering and absorption coefficients. A technique is presented to easily determine absorbent compound concentration ratios in a turbid media from three optical reflectance spectra, in the visible range, measured for source-detector distances less than 1cm. The validity of the method is experimentally established, in cases of sets of diluted milk containing absorbent inks, over a relatively wide range of absorption (0.05-0.5 cm(-1)) and reduced scattering (10-20 cm(-1)) coefficients.

  17. 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

  18. 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.

  19. 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.

  20. Satellite material contaminant optical properties

    NASA Astrophysics Data System (ADS)

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

    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) transmittance data for contaminant films condensed on a 77 K germanium 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. Satellite material contaminant optical properties

    NASA Astrophysics Data System (ADS)

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

    1990-03-01

    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 germanium 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.

  2. Satellite Material Contaminant Optical Properties

    NASA Astrophysics Data System (ADS)

    Wood, Bobby E.; Bertrand, William T.; Seiber, Bryan L.; Kiech, E. L.; Falco, Patrick 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. This paper presents 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 contants 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.

  3. 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.

  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. Thermal properties of carbon black aqueous nanofluids for solar absorption

    PubMed Central

    2011-01-01

    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. PMID:21767359

  6. 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.

  7. 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.

  8. 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.

  9. Optical absorptance and thermomodulation studies of several A-15 compounds

    SciTech Connect

    McKee, R.C.

    1983-06-01

    The purpose of this work was to investigate the optical properties of several high T/sub c/ compounds in the form of sputtered films. The measurements are used toward this end: optical absorptance (using a calorimetric technique near 4.2K), which yields (after Kramers-Kronig analysis) the complex dielectric function, and thermoreflectance (which measures the change in reflectance in the optical range when a 1 to 10/sup 0/K temperature wave is applied), performed at two ambient temperatures (80 and 300/sup 0/K), yielding the differential dielectric function. The sputtered films included Nb/sub 3/Ge, Nb/sub 3/Al, V/sub 3/Ga and Nb/sub 3/Ir. It is noted that Nb/sub 3/Ir is not a high T/sub c/ superconductor. The thermoreflectance on the bulk samples V/sub 3/Si, V/sub 3/Ge and single crystal Cr/sub 3/Si were not performed because the samples were not in the form of thin films. The thermomodulation studies are correlated with the absorptance measurements in comparison to band structure calculations. When thermomodulation studies are performed on semiconductors, these studies yield information about critical points, but studies on metals indicate that Fermi-level transitions become important. It is thought that A-15 structured compounds, which have a high density of electron states around the Fermi level, will produce spectra due to this high density of states. Procedures and results are detailed.

  10. Thermally detected optical absorption in sophisticated nitride structures

    NASA Astrophysics Data System (ADS)

    Vasson, A.; Shubina, T. V.; Leymarie, J.

    2005-02-01

    The thermally detected optical absorption (TDOA) is applied to elucidate peculiarities of absorption in nitride structures of unusual morphology like GaN nanocolumns or InN layers with various imperfections. A study of GaN structures permits us to establish position of an absorption edge in TDOA spectra. We demonstrate that the absorption edge is different in GaN regions of opposite polarities. In InN with metallic In inclusions, this technique enable separation of InN interband absorption and extinction related to the Mie resonances, if the latter are below the principal absorption edge.

  11. Cooperative luminescence and absorption in ytterbium doped aluminosilicate glass optical fibres and preforms

    NASA Astrophysics Data System (ADS)

    Ryan, Tom G.; Jackson, Stuart D.

    2007-05-01

    The cooperative luminescence and absorption properties of Yb 3+ doped aluminosilicate glass optical fibres and preforms are investigated in detail. In accordance with previous investigations, both the visible cooperative luminescence and the infrared luminescence decay measurements have been resolved into a single exponential decay component. We show that for a glass with similar Yb 3+ dopant concentration but more Al 3+, the glass emits less visible luminescence. Absorption loss measurements completed on fibre samples revealed a broad absorption in the 350-500 nm range, which we propose is due to a combination of Yb 2+ absorption and cooperative absorption from Yb 3+ ion pairs.

  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. Optical properties of detonation nanodiamond hydrosols

    NASA Astrophysics Data System (ADS)

    Aleksenskii, A. E.; Vul', A. Ya.; Konyakhin, S. V.; Reich, K. V.; Sharonova, L. V.; Eidel'man, E. D.

    2012-03-01

    Studies of the optical properties of hydrosols of 4-nm detonation nanodiamond particles performed in the 0.2-1.1 μm range have revealed a novel effect, a strong increase of absorption at the edges of the spectral range, and provided its explanation in terms of absorption of radiation by the dimer chains (the so-called Pandey chains) fixed on the surface of a nanodiamond particle. The effect of particle size distribution in a hydrosol on the relative intensity of Rayleigh scattering and light absorption by nanodiamond particles in this range has been analyzed.

  14. 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

  15. In-line absorption sensor based on coiled optical microfiber

    NASA Astrophysics Data System (ADS)

    Lorenzi, Roberto; Jung, Yongmin; Brambilla, Gilberto

    2011-04-01

    We fabricated and tested an evanescent-wave absorption sensor consisting of an optical microfiber coil resonator embedded in fluidic channel walls. Low concentrations of flowing analyte show optical losses in agreement with a modified Beer-Lambert law. Higher concentration causes a limit value of the measured optical losses arising from adsorption mechanisms.

  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. Optical properties of flyash

    SciTech Connect

    Self, S.A.

    1990-10-01

    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. Work is organized under four tasks: Characterization of Flyash: The chemical composition and size distribution of representative flyashes are being measured by appropriate microanalytical techniques; Measurements of the Optical Constants of Slags: Measurements of the infrared optical constants (i.e., the complex reflective index m = n {minus} ik) of synthetic slags are being made as a function of wavelength and temperature for controlled compositions. Particular attention will be given to the contribution of the Fe{sub 2}O{sub 3} content and its valence state. The data is being reduced to yield formulae giving the complex refractive index over relevant ranges of wavelength and temperatures, as a function of the relevant metal oxide constituents; Sample Calculations of the Radiant Properties of Flyash Dispersions: This component comprises various calculations to guide and evaluate the experimental work under the other three tasks; and Measurement of the Radiant Properties of Flyash Dispersions: This bench-scale experiment is planned to compare the measured radiant properties of a dispersion of well-characterized ash with computations based on data developed under the first two tasks. Progress is described in all areas. 10 refs., 20 figs., 5 tabs.

  18. Effect of idler absorption in pulsed optical parametric oscillators.

    PubMed

    Rustad, Gunnar; Arisholm, Gunnar; Farsund, Øystein

    2011-01-31

    Absorption at the idler wavelength in an optical parametric oscillator (OPO) is often considered detrimental. We show through simulations that pulsed OPOs with significant idler absorption can perform better than OPOs with low idler absorption both in terms of conversion efficiency and beam quality. The main reason for this is reduced back conversion. We also show how the beam quality depends on the beam width and pump pulse length, and present scaling relations to use the example simulations for other pulsed nanosecond OPOs.

  19. 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.

  20. Properties of quasar broad absorption line outflows

    NASA Astrophysics Data System (ADS)

    Capellupo, Daniel Moshin

    2012-06-01

    Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that likely exist in all quasars and could play a major role in feedback to galaxy evolution. In this dissertation, I use two methods to illuminate important properties of these outflows with the goal of a better understanding of these outflow systems and ultimately of the connection between quasars and their host galaxies. The variability of BALs can help us understand the structure, evolution, and basic physical properties of the outflows. I report here on a BAL monitoring programme of a sample of 24 luminous quasars at redshifts 1.2absorption to try to ascertain the cause(s) of the variability. I find that Si IV BALs are more likely to vary than C IV BALs. When both C IV and Si IV varied, those changes always occurred in the same sense (either getting weaker or stronger). The multi-epoch data, including up to 10 epochs of data per quasar, show that the BAL changes were not generally monotonic across the full ˜5 to ˜8 yr time span of our observations, suggesting that the characteristic time-scale for significant line variations, and (perhaps) for structural changes in the outflows, is less than a few years. The evidence presented here indicates that the cause of variability is likely a complex mixture of changing ionization in the outflowing

  1. Absorption properties of metal-semiconductor hybrid nanoparticles.

    PubMed

    Shaviv, Ehud; Schubert, Olaf; Alves-Santos, Marcelo; Goldoni, Guido; Di Felice, Rosa; Vallée, Fabrice; Del Fatti, Natalia; Banin, Uri; Sönnichsen, Carsten

    2011-06-28

    The optical response of hybrid metal-semiconductor nanoparticles exhibits different behaviors due to the proximity between the disparate materials. For some hybrid systems, such as CdS-Au matchstick-shaped hybrids, the particles essentially retain the optical properties of their original components, with minor changes. Other systems, such as CdSe-Au dumbbell-shaped nanoparticles, exhibit significant change in the optical properties due to strong coupling between the two materials. Here, we study the absorption of these hybrids by comparing experimental results with simulations using the discrete dipole approximation method (DDA) employing dielectric functions of the bare components as inputs. For CdS-Au nanoparticles, the DDA simulation provides insights on the gold tip shape and its interface with the semiconductor, information that is difficult to acquire by experimental means alone. Furthermore, the qualitative agreement between DDA simulations and experimental data for CdS-Au implies that most effects influencing the absorption of this hybrid system are well described by local dielectric functions obtained separately for bare gold and CdS nanoparticles. For dumbbell shaped CdSe-Au, we find a shortcoming of the electrodynamic model, as it does not predict the "washing out" of the optical features of the semiconductor and the metal observed experimentally. The difference between experiment and theory is ascribed to strong interaction of the metal and semiconductor excitations, which spectrally overlap in the CdSe case. The present study exemplifies the employment of theoretical approaches used to describe the optical properties of semiconductors and metal nanoparticles, to achieve better understanding of the behavior of metal-semiconductor hybrid nanoparticles.

  2. 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

  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. Optical properties of coumarins containing copolymers

    NASA Astrophysics Data System (ADS)

    Skowronski, L.; Krupka, O.; Smokal, V.; Grabowski, A.; Naparty, M.; Derkowska-Zielinska, B.

    2015-09-01

    We investigate the optical properties such as absorption coefficient, refractive index, real and imaginary parts of dielectric function and energy band gap of coumarin-containing copolymers thin films by means of spectroscopic ellipsometry (SE) combined with transmittance measurements (T) and atomic force microscopy (AFM). We found that the optical properties of coumarin-containing copolymers strongly depend from length of alkyl spacer as well as the type of substitution in coumarin moiety. In our case the refractive index as well as the energy band gap of coumarin-containing copolymer decrease with increase the length of alkyl spacer. Additionally, the lengthening of the alkyl spacer brings the bathochromic shifts of the absorption spectra towards longer wavelengths.

  6. Effect of thickness on nonlinear absorption properties of graphite oxide thin films

    NASA Astrophysics Data System (ADS)

    Sreeja, V. G.; Cheruvalathu, Ajina; Reshmi, R.; Anila, E. I.; Thomas, Sheenu; Jayaraj, M. K.

    2016-10-01

    We report the thickness dependent structural, linear and nonlinear optical properties of graphite oxide (GO) thin films synthesized by spin coating method. We observed that the structural, linear and nonlinear optical properties can be tuned by the film thickness in GO. The nonlinear absorption studies by open aperture z scan technique exhibited a saturable absorption. The nonlinear absorption coefficient and saturation intensity varies with film thickness which is attributed to increased localized defect states in the energy band gap. Our results emphasize relatively large thickness dependent optical nonlinearity of GO thin films and its potential for optical pulse generation, exploring the way to GO based nonlinear applications in Q switched mode locking laser systems. All the coated GO films were characterized by X-Ray diffraction method (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-Vis absorption spectroscopy (UV-Vis), Photoluminescence (PL) and Scanning electron microscope (SEM) measurements.

  7. 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.

  8. [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

  9. 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.

  10. Optical properties of bismuth borate glasses

    NASA Astrophysics Data System (ADS)

    Oprea, Isabella-Ioana; Hesse, Hartmut; Betzler, Klaus

    2004-08-01

    Optical properties of glasses in the binary system bismuth oxide (Bi 2O 3)-boric oxide (B 2O 3) are measured for the composition range 25-65 mol% Bi 2O 3. Both, refractive indices and ultraviolet absorption edge, show an expressed dependence on composition. A generalized Sellmeier formula is derived to describe the refractive indices for the whole composition range and a wide wavelength range.

  11. Tunable optical absorption and interactions in graphene via oxygen plasma

    NASA Astrophysics Data System (ADS)

    Santoso, Iman; Singh, Ram Sevak; Gogoi, Pranjal Kumar; Asmara, Teguh Citra; Wei, Dacheng; Chen, Wei; Wee, Andrew T. S.; Pereira, Vitor M.; Rusydi, Andrivo

    2014-02-01

    We report significant changes of optical conductivity (σ1) in single-layer graphene induced by mild oxygen plasma exposure and explore the interplay between carrier doping, disorder, and many-body interactions from their signatures in the absorption spectrum. The first distinctive effect is the reduction of the excitonic binding energy that can be extracted from the renormalized saddle point resonance at 4.64 eV. Secondly, σ1 is nearly completely suppressed (σ1≪σ0) below an exposure-dependent threshold in the near-infrared range. The clear steplike suppression follows the Pauli blocking behavior expected for doped monolayer graphene. The nearly zero residual conductivity below ω ˜ 2EF can be interpreted as arising from the weakening of the electronic self-energy. Our data shows that mild oxygen exposure can be used to controllably dope graphene without introducing the strong physical and chemical changes that are common in other approaches to oxidized graphene, allowing a controllable manipulation of the optical properties of graphene.

  12. Optical-induced absorption tunability of Barium Strontium Titanate film

    NASA Astrophysics Data System (ADS)

    Luo, Chunya; Ji, Jie; Yue, Jin; Rao, Yunkun; Yao, Gang; Li, Dan; Zeng, Ying; Li, Renkui; Xiao, Longsheng; Liu, Xinxing; Yao, Jianquan; Ling, Furi

    2016-10-01

    The absorption tunability of 100 nm thickness of ferroelectric Barium Strontium Titanate (Ba0.5Sr0.5TiO3) thin films with different densities of pumped optical field is measured by terahertz time-domain spectroscopy in the range of 0.2 THz - 1.2 THz at 19 °C. Experimental results show that the absorption coefficient of BST film is approximately at 5000 cm-1-20000 cm-1 in the range of 0.2 THz - 1.2 THz and the absorption coefficient reached up to 16% when we applied the optical field up to 600 mW. The theoretical calculations reveal that increasing photoexcitation fluences is responsible for the increasing of transmission change in the conduction current density cause the absorption coefficient varied.

  13. 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.

  14. 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.

  15. Reconstruction of optical absorption coefficient maps of heterogeneous media by photoacoustic tomography coupled with diffusion equation based regularized Newton method.

    PubMed

    Yuan, Zhen; Wang, Qiang; Jiang, Huabei

    2007-12-24

    We describe a novel reconstruction method that allows for quantitative recovery of optical absorption coefficient maps of heterogeneous media using tomographic photoacoustic measurements. Images of optical absorption coefficient are obtained from a diffusion equation based regularized Newton method where the absorbed energy density distribution from conventional photoacoustic tomography serves as the measured field data. We experimentally demonstrate this new method using tissue-mimicking phantom measurements and simulations. The reconstruction results show that the optical absorption coefficient images obtained are quantitative in terms of the shape, size, location and optical property values of the heterogeneities examined.

  16. [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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Tunable many-body interactions in semiconducting graphene: Giant excitonic effect and strong optical absorption

    NASA Astrophysics Data System (ADS)

    Dvorak, Marc; Wu, Zhigang

    2015-07-01

    Electronic and optical properties of graphene depend strongly on many-body interactions. Employing the highly accurate many-body perturbation approach based on Green's functions, we find a large renormalization over independent particle methods of the fundamental band gaps of semiconducting graphene structures with periodic defects. Additionally, their exciton binding energies are larger than 0.4 eV, suggesting significantly strengthened electron-electron and electron-hole interactions. Their absorption spectra show two strong peaks whose positions are sensitive to the defect fraction and distribution. The strong near-edge optical absorption and excellent tunability make these two-dimensional materials promising for optoelectronic applications.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Optical properties and structure of beryllium lead silicate glasses

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    Luminescence and optical properties and structural features of (BeO)x(PbOṡSiO2)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.

  8. 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

  9. An optical absorption cell with vapor cross flow.

    NASA Technical Reports Server (NTRS)

    Hendrickson, P. E.; Walls, W. L.; Broersma, S.

    1973-01-01

    Description of a water vapor cross flow system that simulates meteorological conditions and effectively curbs any disturbing effects of walls and vacuum connections in an optical absorption cell. Vapor equilibrium is established within 30 min. A 6.3 micron infrared beam traverses the pressure, temperature, and humidity controlled vapor column. The effect of these thermodynamic parameters can be examined.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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. Plasmonic metamaterials with tuneable optical properties

    NASA Astrophysics Data System (ADS)

    Zayats, Anatoly

    2008-03-01

    Negative refraction in metamaterials has recently attracted significant attention due to its possible numerous applications in high-resolution imaging and photolithography with the so-called ``perfect lenses,'' for electromagnetic shielding (invisibility cloak), optical signal manipulation, etc. Among various realizations of negative index materials, plasmonic nanostructures play a prominent role as they allow negative refraction properties to be engineered in the visible and near infrared spectral ranges. The coupling of light to plasmonic modes, that are collective electronic excitations in metallic nanostructures, provides the possibility to confine the electromagnetic field on the sub-wavelength scale and manipulate it with high precision to achieve the desired mode dispersion and, thus, reflection, absorption and transmission properties of the nanostructures. In this talk we will discuss various pathways to control dispersion of the electromagnetic waves in plasmonic metamaterials, including plasmon polaritonic crystals and plasmonic nanorod arrays, and the approaches to active tuneability of their optical properties using optical and electric control signals. Both approaches take advantage of the very high sensitivity of surface plasmon mode dispersion on the refractive index of the dielectric adjacent to metallic nanostructure. Hybridization of plasmonic nanostructures with molecular species exhibiting nonlinear optical response allows the development of metamaterials with high effective nonlinear susceptibility due to the electromagnetic field enhancement related to plasmonic excitations. Signal and control light are then coupled to plasmonic modes that strongly interact via nonlinearity introduced by the hybridization. Concurrently, the use of electro-optically active dielectrics incorporated into plasmonic nanostructures provides the route to control optical signals electronically. Plasmonic metamaterials with tuneable optical properties can be used to

  13. 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."

  14. 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

  15. Optical properties of cometary dust

    NASA Technical Reports Server (NTRS)

    Lien, David J.

    1991-01-01

    The application of measured optical constants to the interaction of electromagnetic radiation with small cometary dust particles is discussed, with emphasis on the interpretation of cometary observations. It is found that in some spectral regions optical constants vary greatly with wavelength. The optical constants may be incorrect. Because of errors in measurement, or the application of the Kramers-Kronig relationship over too small a spectral region, or an improperly prepared sample, the derived optical constants may be in error. It is suggested that a full Kramers-Kronig analysis and application of the more important sum rules should be performed on any set of optical constants whose accuracy is important. Optical constants derived from the measurement of inhomogeneous materials, where the inhomogeneities are of comparable size to that of the beam of radiation used in the experiment, should not be used to predict the optical properties of small particles.

  16. 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.

  17. 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.

  18. Absorption and fluorescence properties of fluorescein

    NASA Astrophysics Data System (ADS)

    Sjöback, Robert; Nygren, Jan; Kubista, Mikael

    1995-06-01

    We have characterized the protolytic equilibria of fluorescein and determined the spectroscopic properties of its protolytic forms. The protolytic constants relating the chemical activities (which at low ionic strength equal concentrations) of the cation, neutral form, anion and dianion are p K1 = 2.08, p K2 = 4.31, and p K3 = 6.43. All forms have rather high molar absorptivities being ɛ437FH 3 1 = 53 000, ɛ434FH 2 = 11 000, ɛ453FH- = 29 000 ( ɛ472FH = 29 000) and ɛ490F 2 = 76 900 M -1 cm -1 for the cation, neutral form, anion and dianion, respectively. The dianion has the most intense fluorescence with a quantum yield of 0.93 but also the anion shows considerable fluorescence with a quantum yield of 0.37. The neutral and cationic species are upon excitation converted into the anion and fluoresce with quantum yields of about 0.30 and 0.18, respectively.

  19. Self-aggregation and optical absorption of stilbazolium merocyanine in chloroform.

    PubMed

    Silva, Daniel L; Murugan, N Arul; Kongsted, Jacob; Ågren, Hans; Canuto, Sylvio

    2014-02-20

    Dipolar aggregation is in many cases detrimental for the functioning of optical materials. In this study we investigate self-aggregation and optical absorption of stilbazolium merocyanine (SM) in chloroform solution by performing classical Molecular Dynamics (MD) simulations under ambient conditions. The reversal solvatochromic shift, the large bathochromic shift, and the structured absorption band presented by SM in chloroform solution are all aspects of its optical absorption behavior for which the existence of self-aggregation is yet not completely understood. Moreover, the spectroscopic properties of SM oligomers and their occurrence in solvent of low polarity remain a relevant topic that deserves to be investigated. Our analysis of the aggregation behavior of SM in chloroform verified that the majority of the chromophores are involved in the formation of oligomers in solution, where the whole dimer and part of the trimer populations present a stable π-stacking structure. The optical properties of the monomers and oligomers in solution were evaluated by means of a discrete polarizable embedding quantum mechanical/molecular mechanical (PE-QM/MM) response scheme where the quantum part is described at the level of density functional theory. The visible absorption spectrum of SM in chloroform is simulated using time average values obtained for the monomeric and oligomeric forms of SM from the PE-QM/MM calculations performed on uncorrelated configurations extracted from the classical MD simulations. This study shows that the self-aggregation of SM in chloroform may exist, but it is not essential for reproducing the reversal solvatochromic shift in chloroform and that the process does not contribute to enhance the bathochromic shift nor explain the structure observed in its absorption band. Moreover, it is verified that since the electronic transitions of the monomer and oligomers are close together, changes in the interplane separation between the monomeric units

  20. 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.

  1. Optical absorption characteristics in thermally reduced Er:LiNbO 3 crystals

    NASA Astrophysics Data System (ADS)

    Zhang, De-Long; Ma, Rui; Pun, E. Y. B.

    2006-03-01

    Influence of thermal reduction on intrinsic (bipolarons), extrinsic (Er3+) defects and OH- groups in Er:LiNbO3 crystals, which were as-grown and VTE-treated (VTE: vapor transport equilibration) before being reduced, was studied by measuring the polarised or unpolarised optical absorption in visible and near infrared regions. A wide and strong band extending from the optical absorption edge up to the infrared region and peaking around 500 nm (∼2.5 eV), resulting from the absorption of reduction-induced bipolarons, is observed. Meanwhile, the thermal reduction also induces an additional, relatively much narrow absorption band around 370 nm in a crystal whether it is Er-doped or undoped and whether it is congruent or originally VTE-treated. Both the 500 nm and the 370 nm bands show similar polarisation dependence. The thermal reduction treatment hardly influences Er3+ spectroscopic properties such as absorption amplitude, linewidth, peaking position and polarisation dependence. The original VTE effects on the spectroscopic properties of Er:LiNbO3 crystal are essentially retained still. The thermal reduction has a similar effect on the OH- absorption to a strong VTE treatment: the removal of the OH- groups contained in the crystal.

  2. Optical properties of InN related to surface plasmons

    NASA Astrophysics Data System (ADS)

    Shubina, T. V.; Leymarie, J.; Jmerik, V. N.; Toropov, A. A.; Vasson, A.; Amano, H.; Schaff, W. J.; Monemar, B.; Ivanov, S. V.

    2005-11-01

    We report on the complex nature of infrared luminescence and absorption in InN films, which cannot be entirely explained by the concept of a conventional narrow-gap semiconductor. In particular, it concerns the detection of peaks near absorption edges by both thermally detected optical absorption and photoluminescence excitation spectroscopy and the observation of extraordinarily strong resonant enhancement of emission. To describe the experimental data a model is proposed, which takes into account surface plasmons in metal-like inclusions, modifying the optical properties of InN.

  3. 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.

  4. Obtaining optical properties using Representative Layer Theory

    NASA Astrophysics Data System (ADS)

    Razavi, Neema; Yust, Brain; Sardar, Dhiraj

    2011-03-01

    Reliable and minimally invasive methods for diagnosis of toxicity and onset of disease are important for advances in clinical practices. This is commonly achieved through the optical properties, such as a change in the absorption or scattering strength of the diseased tissue. Thus, being able to quantitatively characterize these changes is important to advancements in medical diagnostic methods. By adapting the Representative Layer Theory to the integrating sphere technique, very thin biological samples may be optically characterized, yielding a quick and easy method for monitoring optical changes as a function of disease progression. Samples, consisting of cells, dyes, and nanoparticles of known concentrations were optically characterized at multiple wavelengths. Optical properties obtained by the Representative Layer Theory are compared to those obtained through other methods, such as Kubelka-Munk and Inverse Adding Doubling which are known to have sample thickness limitations. This work is also supported in part by National Science Foundation PREM Grant No. DMR - 0934218 and UTSA Collaborative Research Seed Grant Program (CRSGP).

  5. Intrinsic fiber optic absorption sensor for the detection of volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Klunder, Gregory L.; Silva, Robert J.; Russo, Richard E.

    1994-03-01

    A core-based intrinsic fiber optic absorption sensor has been developed for the detection of volatile organic compounds. The sensor can detect organics in aqueous solutions or in the vapor phase without a chemical reaction. The distal ends of transmission and receiving fibers are connected by a small section of an optically clear silicone rubber. The silicone rubber section acts both as a lightpipe and as a selective membrane into which the analyte molecules can diffuse. Absorption spectra obtained in the nearinfrared (NIR) provide qualitative and quantitative information about the analyte. Water, which has strong broadband absorption in aqueous solutions of the NIR, is excluded from the spectra due to the hydrophobic properties of the silicone rubber. In a stirred solution, the sensor reaches equilibrium in approximately 10 minutes. The current limit of detection is 1.0 ppm for TCE in an aqueous solution.

  6. Research development of designing flow cells for optical absorption detectors.

    PubMed

    Yang, Sandong; Tang, Tao; Li, Tong; Wang, Fengyun; Hao, Qingli

    2016-02-01

    The optical absorption detector is one of the most commonly used detectors for high performance liquid chromatography (HPLC). As a core part of this kind of detector, the designs of flow cells, where light passes through samples for acquiring samples information, will affect the performance of a detector. In order to enhance the signal to noise ratio of detectors and reduce the bands broadening that come from flow cells, it is necessary to design a flow cell with a longer optical path length and a less cell volume while maintaining the luminous flux. However the limitations of the machining capacity make it difficult to increase the optical path length, reduce the cell volume and keep or increase the luminous flux simultaneously. It is a challenge to optimize the designing and machining of flow cells so as to improve the performance of detectors. This review discusses the development of designing flow cells based on the detection principle in some aspects of increasing the optical path length, reducing the cell volume, taking the advantages of total reflection and so on. At the same time, some of the designs are illustrated in detail. These various ideas and structures are significant references for designing flow cells and developing optical absorption detectors. PMID:27382716

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. 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.

  17. Time-resolved diffuse optical spectroscopy: a differential absorption approach

    NASA Astrophysics Data System (ADS)

    Taroni, Paola; Bassi, Andrea; Spinelli, Lorenzo; Cubeddu, Rinaldo; Pifferi, Antonio

    2009-07-01

    A method was developed to estimate spectral changes of the absorption properties of turbid media from time-resolved reflectance/transmittance measurements. It was derived directly from the microscopic Beer-Lambert law, and tested against simulations and phantom measurements.

  18. 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.

  19. A Parallel Reconstruction Scheme in Fluorescence Tomography Based on Contrast of Independent Inversed Absorption Properties

    PubMed Central

    Yi, Ji; Bai, Jing

    2006-01-01

    Based on an independent forward model in fluorescent tomography, a parallel reconstructed scheme for inhomogeneous mediums with unknown absorption property is proposed in this paper. The method considers the two diffusion equations as separately describing the propagation of excited light in tissues with and without fluorescent probes inside. Then the concentration of fluorophores is obtained directly through the difference between two estimations of absorption coefficient which can be parallel inversed. In this way, the multiparameter estimation problem in fluorescent tomography is transformed into two independent single-coefficient determined schemes of diffusion optical tomography (DOT). Any algorithms proved to be efficient and effective in DOT can be directly applied here. In this study the absorption property is estimated from the independent diffusion equations by a gradient-based optimization method with finite element method (FEM) solving the forward model. Simulation results of three representative occasions show that the reconstructed method can well estimate fluorescent property and tissue absorption distribution. PMID:23165045

  20. 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.

  1. 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.

  2. Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 2. Closure study.

    PubMed

    Müller, Thomas; Müller, Detlef; Dubois, René

    2006-04-01

    Spectral particle extinction coefficients of atmospheric aerosols were measured with, to the best of our knowledge, a newly designed differential optical absorption spectroscopy (DOAS) instrument. A closure study was carried out on the basis of optical and microphysical aerosol properties obtained from nephelometer, particle soot/absorption photometer, hygroscopic tandem differential mobility analyzer, twin differential mobility particle sizer, aerodynamic particle sizer, and Berner impactors. The data were collected at the urban site of Leipzig during a period of 10 days in March 2000. The performance test also includes a comparison of the optical properties measured with DOAS to particle optical properties calculated with a Mie-scattering code. The computations take into account dry and ambient particle conditions. Under dry particle conditions the linear regression and the correlation coefficient for particle extinction are 0.95 and 0.90, respectively. At ambient conditions these parameters are 0.89 and 0.97, respectively. An inversion algorithm was used to retrieve microphysical particle properties from the extinction coefficients measured with DOAS. We found excellent agreement within the retrieval uncertainties.

  3. Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 2. Closure study.

    PubMed

    Müller, Thomas; Müller, Detlef; Dubois, René

    2006-04-01

    Spectral particle extinction coefficients of atmospheric aerosols were measured with, to the best of our knowledge, a newly designed differential optical absorption spectroscopy (DOAS) instrument. A closure study was carried out on the basis of optical and microphysical aerosol properties obtained from nephelometer, particle soot/absorption photometer, hygroscopic tandem differential mobility analyzer, twin differential mobility particle sizer, aerodynamic particle sizer, and Berner impactors. The data were collected at the urban site of Leipzig during a period of 10 days in March 2000. The performance test also includes a comparison of the optical properties measured with DOAS to particle optical properties calculated with a Mie-scattering code. The computations take into account dry and ambient particle conditions. Under dry particle conditions the linear regression and the correlation coefficient for particle extinction are 0.95 and 0.90, respectively. At ambient conditions these parameters are 0.89 and 0.97, respectively. An inversion algorithm was used to retrieve microphysical particle properties from the extinction coefficients measured with DOAS. We found excellent agreement within the retrieval uncertainties. PMID:16607998

  4. 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.

  5. Microwave absorption properties of composite powders with low density

    NASA Astrophysics Data System (ADS)

    Mu, Guohong; Shen, Haigen; Qiu, Jianxun; Gu, Mingyuan

    2006-12-01

    The composites of barium ferrite coated on hollow ceramic microspheres were prepared using sol-gel technique. The crystal structure, morphology and microwave absorption properties of composite powders with different weight ratio of microspheres were studied with XRD, EDS, FESEM and vector network analyzer. The results show that the microwave absorption properties of composite powders are greatly improved. The maximum microwave loss of composite powders reaches 31 dB with an amount of 50 wt.% microspheres, and its density is only about 1.80 g/cm 3. The effect of hollow ceramic microspheres on the microwave absorption property is also discussed.

  6. Near-infrared radiation absorption properties of covellite (CuS) using first-principles calculations

    NASA Astrophysics Data System (ADS)

    Xiao, Lihua; Wu, Jianming; Ran, Jingyu; Liu, Yike; Qiu, Wei; Lu, Fanghai; Shao, Fang; Tang, Dongsheng; Peng, Ping

    2016-08-01

    First-principles density functional theory was used to investigate the electronic structure, optical properties and the origin of the near-infrared (NIR) absorption of covellite (CuS). The calculated lattice constant and optical properties are found to be in reasonable agreement with experimental and theoretical findings. The electronic structure reveals that the valence and conduction bands of covellite are determined by the Cu 3d and S 3p states. By analyzing its optical properties, we can fully understand the potential of covellite (CuS) as a NIR absorbing material. Our results show that covellite (CuS) exhibits NIR absorption due to its metal-like plasma oscillation in the NIR range.

  7. Density and optical properties of SPARCS plumes

    NASA Technical Reports Server (NTRS)

    Brown, W. A.; Kumer, J. B.; Cooper, C. E., Jr.

    1972-01-01

    Propellant gases emitted by attitude control systems such as SPARCS (Solar Pointing Aerobee Rocket Control System) and possible interference with experiments aboard the payloads are discussed. The optical properties of seven actual and potential gases emitted by propellant systems (CF4, N2H4, NH3, N2, CO2, Ar, and He) are presented. A compilation of absorption coefficients from 1 Angstrom to 50 microns and a summary of fluorescent spectra and efficiencies are provided. Since Freon-14 (CF4) is of primary importance to SPARCS, an experimental search for the fluorescent spectrum of CF4 was performed by exciting the gas with 920 Angstrom UV photons. The result was compared with an electron impact induced spectrum of CF4, and conclusions drawn about the nature of the radiating species. A detailed study of the CF4 flow fields and plume densities for typical SPARCS controlled payloads was made using gas dynamic codes which included the effects of vehicle shading and condensation. The importance of the optical properties of CF4 plumes was investigated and it is concluded that absorption is negligible but fluoresence may be significant in some cases.

  8. Optical absorption and transmission in a molybdenum disulfide monolayer

    NASA Astrophysics Data System (ADS)

    Rukelj, Zoran; Štrkalj, Antonio; Despoja, Vito

    2016-09-01

    Our recently proposed theoretical formulation [presented in D. Novko et al., Phys. Rev. B 93, 125413 (2016), 10.1103/PhysRevB.93.125413] is used to study optical absorption and transmission in molybdenum disulfide (MoS2) monolayer as a function of incident photon energy and angle. The investigation is not focused on exploration of well-documented spin-orbit split excitons around optical absorption onset, but rather on the most intensive features in absorption spectrum in the visible and near-ultraviolet photon energy range (1.7 -4 eV ). It is shown that three most intensive peaks, at 2.7, 3.1, and 3.7 eV, result from transitions between Mo(d ) and S(p ) valence and conduction bands and that the character of their charge/current density fluctuations is intrinsically in plane, located in the molybdenum plane. This also implies that MoS2 monolayer is completely transparent when illuminated by grazing incidence p -polarized light. The validity of the presented results is supported by our effective two-band tight-binding model and finally by good agreement with some recent experimental results.

  9. Quantum quench of Kondo correlations in optical absorption

    NASA Astrophysics Data System (ADS)

    Weichselbaum, Andreas

    2013-03-01

    Absorption spectra of individual semiconductor quantum dots tunnel-coupled to a degenerate electron gas in the Kondo regime have recently become accessible to the experiment. The absorption of a single photon leads to an abrupt change in the system Hamiltonian, which can be tailored such that it results in a quantum quench of the Kondo correlations. This is accompanied by a clear signature in the form of an Anderson orthogonality catastrophe, induced by a vanishing overlap between initial and final many-body wave functions and with power-law exponents that can be tuned by an applied magnetic field. We have modeled the experiment in terms of an Anderson impurity model undergoing an optically induced quench, and studied this Kondo exciton in detail using both analytical methods and the Numerical Renormalization Group (NRG). Our NRG results reproduce the measured absorption line shapes very well, showing that NRG is ideally suited for the study of Kondo excitons. In summary, the experiments demonstrate that optical measurements on single artificial atoms offer new perspectives on many-body phenomena previously studied using transport spectroscopy only. Co-authors: Andreas Weichselbaum, Markus Hanl, and Jan von Delft, Ludwig Maximilians University.

  10. Direct absorption measurements in thin rods and optical fibers

    NASA Astrophysics Data System (ADS)

    Mühlig, Christian; Bublitz, Simon; Lorenz, Martin

    2015-11-01

    We report on the first realization of direct absorption measurements in thin rods and optical fibers using the laser induced deflection (LID) technique. Typically, along the fiber processing chain more or less technology steps are able to introduce additional losses to the starting material. After the final processing, the fibers are commonly characterized regarding losses using the so-called cut-back technique in combination with spectrometers. This, however, only serves for a total loss determination. For optimization of the fiber processing, it would be of great interest to not only distinguish between different loss mechanisms but also have a better understanding of possible causes. For measuring the absorption losses along the fiber processing, a particular concept for the LID technique is introduced and requirements, calibration procedure as well as first results are presented. It allows to measure thin rods, e.g. during preform manufacturing, as well as optical fibers. In addition, the results show the prospects to also apply the new concept to topics like characterizing unwanted absorption after fiber splicing or Bragg grating inscription.

  11. Stability properties of wines by absorption spectra

    NASA Astrophysics Data System (ADS)

    Larena, A.; Vega, J.

    1986-03-01

    The temporal evolution of absorption spectra (370-700 nm) of different spanish wines has been studied by us under the influence of air presence, and the light exposition. In particular, we have exposed the wines to a magenta light. Nevertheless, the color coordinates of wine show a little relative variation (0.1-1 %)

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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).

  18. Investigating cloud absorption effects: Global absorption properties of black carbon, tar balls, and soil dust in clouds and aerosols

    NASA Astrophysics Data System (ADS)

    Jacobson, Mark Z.

    2012-03-01

    This study examines modeled properties of black carbon (BC), tar ball (TB), and soil dust (SD) absorption within clouds and aerosols to understand better Cloud Absorption Effects I and II, which are defined as the effects on cloud heating of absorbing inclusions in hydrometeor particles and of absorbing aerosol particles interstitially between hydrometeor particles at their actual relative humidity (RH), respectively. The globally and annually averaged modeled 550 nm aerosol mass absorption coefficient (AMAC) of externally mixed BC was 6.72 (6.3-7.3) m2/g, within the laboratory range (6.3-8.7 m2/g). The global AMAC of internally mixed (IM) BC was 16.2 (13.9-18.2) m2/g, less than the measured maximum at 100% RH (23 m2/g). The resulting AMAC amplification factor due to internal mixing was 2.41 (2-2.9), with highest values in high RH regions. The global 650 nm hydrometeor mass absorption coefficient (HMAC) due to BC inclusions was 17.7 (10.6-19) m2/g, ˜9.3% higher than that of the IM-AMAC. The 650 nm HMACs of TBs and SD were half and 1/190th, respectively, that of BC. Modeled aerosol absorption optical depths were consistent with data. In column tests, BC inclusions in low and mid clouds (CAE I) gave column-integrated BC heating rates ˜200% and 235%, respectively, those of interstitial BC at the actual cloud RH (CAE II), which itself gave heating rates ˜120% and ˜130%, respectively, those of interstitial BC at the clear-sky RH. Globally, cloud optical depth increased then decreased with increasing aerosol optical depth, consistent with boomerang curves from satellite studies. Thus, CAEs, which are largely ignored, heat clouds significantly.

  19. 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.

  20. 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

  1. Absorption property and nanosensing via double metal films with rectangle holes array

    NASA Astrophysics Data System (ADS)

    Chen, Fang; Zhang, Huafeng

    2016-11-01

    A theoretical investigation of plasmonic absorption and nanosensing based on a three dimensional nanostructure is presented. The structure consists of double metal films covered with rectangle nanoholes array. A dielectric layer is located between the double metal films with the function of confining electromagnetic fields. Optical absorption properties of the designed nanostructure are investigated by finite-difference time-domain method, obvious peaks appear in the absorption spectra is due to the Fabry-Perot resonance effect and localized surface plasmon resonance of the rectangle nanoholes. The absorption spectra dependence on the environmental and dielectric layer refractive index, which makes it an outstanding candidate for nanosensing. The results of this study may have potential application in absorption switching and nanosensors.

  2. 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

  3. 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.

  4. CRC handbook of laser science and technology. Volume 3. Optical materials, Part 1 - Nonlinear optical properties/radiation damage

    SciTech Connect

    Weber, M.J.

    1986-01-01

    This book examines the nonlinear optical properties of laser materials. The physical radiation effects on laser materials are also considered. Topics considered include: nonlinear optical properties; nonlinear and harmonic generation materials; two-photon absorption; nonlinear refractive index; stimulated Raman scattering; radiation damage; crystals; and glasses.

  5. Improvement of differential optical absorption spectroscopy with a multichannel scanning technique.

    PubMed

    Brauers, T; Hausmann, M; Brandenburger, U; Dorn, H P

    1995-07-20

    Differential optical absorption spectroscopy (DOAS) of atmospheric trace gases requires the detection of optical densities below 0.1%. Photodiode arrays are used more and more as detectors for DOAS because they allow one to record larger spectral intervals simultaneously. This type of optical multichannel analyzer (OMA), however, shows sensitivity differences among the individual photodiodes (pixels), which are of the order of 1%. To correct for this a sensitivity reference spectrum is usually recorded separately from the trace-gas measurements. Because of atmospheric turbulence the illumination of the detector while an atmospheric absorption spectrum is being recorded is different from the conditions during the reference measurement. As a result the sensitivity patterns do not exactly match, and the corrected spectra still show a residual structure that is due to the sensitivity difference. This effect usually limits the detection of optical densities to approximately 3 × 10(-4). A new method for the removal of the sensitivity pattern is presented in this paper: Scanning the spectrometer by small wavelength increments after each readout of the OMA allows one to separate the OMA-fixed pattern and the wavelength-fixed structures (absorption lines). The properties of the new method and its applicability are demonstrated with simulated spectra. Finally, first atmospheric measurements with a laser long-path instrument demonstrate a detection limit of 3 × 10(-5) of a DOAS experiment. PMID:21052280

  6. 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

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

    PubMed

    Li, Xiaoqi; Jiang, Huabei

    2013-02-21

    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.

  8. 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

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

    PubMed

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

    2016-01-01

    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

  10. 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.

  11. 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

  12. 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.

  13. 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)

  14. Anisotropic nonlinear optical absorption of gold nanorods in a silica matrix

    NASA Astrophysics Data System (ADS)

    Lamarre, Jean-Michel; Billard, Franck; Kerboua, Chahineze Harkati; Lequime, Michel; Roorda, Sjoerd; Martinu, Ludvik

    2008-01-01

    Nanocomposite films consisting of gold nanospheres or gold nanorods embedded in a silica matrix have been prepared using a hybrid deposition technique consisting of plasma-enhanced chemical vapor deposition of SiO2 and co-sputtering of gold, followed by annealing at 900 °C. Subsequent irradiation with 30 MeV heavy ions (Cu5+) was used to form gold nanorods. Linear and nonlinear optical properties of this material are closely related with the surface plasmon resonance in the visible. The nonlinear absorption coefficient (α2@532 nm) for the films containing gold nanospheres was measured by Z-scan and P-scan techniques, and it was found to be isotropic and equal to -4.8 × 10-2 cm/W. On the contrary, gold nanorods films exhibited two distinct surface plasmon resonance absorption bands giving rise to a strong anisotropic behavior, namely a polarization-dependent linear absorption and saturable absorption. Z-scan and P-scan measurements using various light polarization directions yielded nonlinear absorption coefficient (α2@532 nm) values varying from -0.9 × 10-2 cm/W up to -3.0 × 10-2 cm/W. Linearity of the P-scan method in the context of nanocomposite saturable absorption is also discussed.

  15. 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

  16. Theoretical study on the structures and optical absorption of Si172 nanoclusters

    NASA Astrophysics Data System (ADS)

    Qin, Wei; Lu, Wen-Cai; Xia, Lin-Hua; Zhao, Li-Zhen; Zang, Qing-Jun; Wang, C. Z.; Ho, K. M.

    2015-08-01

    The structures and optical properties of silicon nanoclusters (Si NCs) have attracted continuous interest in the last few decades. However, it is a great challenge to determine the structures of Si NCs for accurate property calculation due to the complication and competition of various structural motifs. In this work, a Si172 NC with a size of about 1.8 nm was investigated using a genetic algorithm combined with tight-binding and DFT calculations. We found that a diamond crystalline core with 50 atoms (1.2 nm) was formed in the Si172 NC. It can be expected that at a size of about 172 atoms, a diamond crystalline structure can nucleate from the center of the Si NCs. The optical properties of the pure and hydrogenated Si172 NC structures also have been studied using the TDDFT method. Compared with the pure Si172 NC, the absorption peaks of the hydrogenated Si172 NC are obviously blue-shifted.

  17. Inferring inherent optical properties and water constituent profiles from apparent optical properties.

    PubMed

    Fan, Yongzhen; Li, Wei; Calzado, Violeta Sanjuan; Trees, Charles; Stamnes, Snorre; Fournier, Georges; McKee, David; Stamnes, Knut

    2015-07-27

    The BP09 experiment conducted by the Centre for Maritime Research and Experimentation in the Ligurian Sea in March 2009 provided paired vertical profiles of nadir-viewing radiances L(u)(z) and downward irradiances E(d)(z) and inherent optical properties (IOPs, absorption, scattering and backscattering coefficients). An inversion algorithm was implemented to retrieve IOPs from apparent optical properties (AOPs, radiance reflectance R(L), irradiance reflectance R(E) and diffuse attenuation coefficient K(d)) derived from the radiometric measurements. Then another inversion algorithm was developed to infer vertical profiles of water constituent concentrations, including chlorophyll-a concentration, non-algal particle concentration, and colored dissolved organic matter from the retrieved IOPs based on a bio-optical model. The algorithm was tested on a synthetic dataset and found to give reliable results with an accuracy better than 1%. When the algorithm was applied to the BP09 dataset it was found that good retrievals of IOPs could be obtained for sufficiently deep waters, i.e. for L(u)(z) and E(d)(z) measurements conducted to depths of 50 m or more. This requirement needs to be satisfied in order to obtain a good estimation of the backscattering coefficient. For such radiometric measurements a correlation of 0.88, 0.96 and 0.93 was found between retrieved and measured absorption, scattering and backscattering coefficients, respectively. A comparison between water constituent values derived from the measured IOPs and in-situ measured values, yielded a correlation of 0.80, 0.78, and 0.73 for chlorophyll-a concentration, non-algal particle concentration, and absorption coefficient of colored dissolved organic matter at 443 nm, respectively. This comparison indicates that adjustments to the bio-optical model are needed in order to obtain a better match between inferred and measured water constituent values in the Ligurian Sea using the methodology developed in this paper.

  18. 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.

  19. 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.

  20. 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

  1. 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)

  2. 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

  3. 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.

  4. Strain-controlled optical absorption in epitaxial ferroelectric BaTiO{sub 3} films

    SciTech Connect

    Chernova, E.; Pacherova, O.; Chvostova, D.; Dejneka, A.; Kocourek, T.; Jelinek, M.; Tyunina, M.

    2015-05-11

    A lattice strain of 0.3%–1.3% is achieved in epitaxial tetragonal BaTiO{sub 3} films grown on (001)-oriented SrTiO{sub 3} single-crystal substrates. Our experimental studies of absorption spectra in the range of 0.74–9.0 eV demonstrate that epitaxy produces significant changes in the optical properties of the films compared with those of a reference polydomain BaTiO{sub 3} crystal: the absorption edge and the peak at 5 eV strongly blue-shift by 0.2–0.4 eV, the magnitude of the peak at 5 eV drops, and certain spectral features disappear, whereas the absorption peak at 8.5 eV remains unchanged. The observed behavior is attributed to ferroelectric polarization, which is enhanced by epitaxial strain in the films. Our results indicate that epitaxially induced variations of ferroelectric polarization may be used to tailor the optical properties of thin films for photonic and optoelectronic applications.

  5. 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

  6. 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

  7. 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.

  8. Optical properties of substituted polyacetylenes

    NASA Astrophysics Data System (ADS)

    Gontia, Ilarie I.

    In this work we present continuous wave (CW) optical spectroscopies of sustituted polyacetylenes: poly-disabstituted-acetylene (PDPA-nBu) and polyphenylacetylene (PPA). We found that although PDPA-nBu is a degenerate ground state polymer, it shows strong photoluminescence (PL) with quantum efficiency larger than 60%. Polarized PL measurements show that PDPA-nBu emission originates from intrachain excitons rather than from the side groups of the polymer chain. The absorption bands were identified, correlating the experimental results with the model proposed in the literature. The CW photomodulation (PM) spectra of pristine unoxidized and oxidized PDPA-nBu films showed that both solitons and polarons are simultaneously photogenerated. On the contrary, the PM spectrum of PDPA-nBu in toluene solution showed only polaron photogeneration. Using the photoinduced absorption detected magnetic resonance (PADMR) spectroscopy and doping induced electron spin resonance (ESR) we identified the spin of the photogenerated species. For spin 1/2 resonance, polaron, neutral soliton, and charged soliton bands were observed in the lambda-PADMR spectrum. We also investigated the charge transfer (CT) process in the PDPA-nBu/ C60 composites. The absorption spectra in the visible and infrared ranges of PDPA-nBu/C60 blend do not show any evidence for CT in the ground state. Using PL, PM and PADMR spectroscopies we show that in the PDPA-nBu/C60 blends the charge transfer reaction takes place in the excited state. PL spectra measured in films with different C60 concentration showed exciton quenching that is due to the fast CT process. The PM spectrum showed the signature of CT, namely, a PA band that peaks at about 1.15 eV, which is associated with C60 ion resulting from the excitons separation into positively charged polaron on the polymer chain and negative C60 ion. PADMR spectra also showed the signature of the CT reaction. We observed two resonances that were identified in H

  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. Absorption and emission properties of photonic crystals and metamaterials

    SciTech Connect

    Peng, Lili

    2007-01-01

    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.

  11. 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).

  12. 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

  13. Optical band-edge absorption of oxide compound SnO 2

    NASA Astrophysics Data System (ADS)

    Roman, L. S.; Valaski, R.; Canestraro, C. D.; Magalhães, E. C. S.; Persson, C.; Ahuja, R.; da Silva, E. F.; Pepe, I.; da Silva, A. Ferreira

    2006-05-01

    Tin oxide (SnO 2) is an important oxide for efficient dielectrics, catalysis, sensor devices, electrodes and transparent conducting coating oxide technologies. SnO 2 thin film is widely used in glass applications due to its low infra-red heat emissivity. In this work, the SnO 2 electronic band-edge structure and optical properties are studied employing a first-principle and fully relativistic full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The optical band-edge absorption α( ω) of intrinsic SnO 2 is investigated experimentally by transmission spectroscopy measurements and their roughness in the light of the atomic force microscopy (AFM) measurements. The sample films were prepared by spray pyrolysis deposition method onto glass substrate considering different thickness layers. We found for SnO 2 qualitatively good agreement of the calculated optical band-gap energy as well as the optical absorption with the experimental results.

  14. Optical properties of DNA in aqueous solution.

    PubMed

    Umazano, J P; Bertolotto, J A

    2008-04-01

    In the study of DNA electric birefringence, it is usual to use theories that consider that molecules in solution are small in relation to the light wavelength. In this work, we study the DNA electric birefringence using a broken-rod macroion (BRM) model composed of two cylindrical arms which does not restrict the size of the molecules. To achieve this, we include the inhomogeneity effect of the light electric field through the molecule and the interaction between its different parts. To analyze the interaction between a molecule and the incident beam of light, we apply the discrete dipole approximation (DDA), according to which each molecule is described as a finite array of electronic coupled oscillators. The electric birefringence is calculated from the oscillator polarizability. This is obtained from experimental data of electric birefringence saturation and from the increment of the solution refraction index in relation to that of the solvent. Furthermore, the oscillator polarizability is also estimated from DNA absorption spectrum using the Kronig-Kramers relations. This allows us to analyze the contributions of the different absorption bands of DNA to the electric birefringence. We analyze the influence of the inhomogeneity of the light electric field and of the intramolecular interactions in the characterization of DNA optical properties using electric birefringence measurements.

  15. 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.

  16. 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.

  17. Influence of the triethanolamine concentration on the optical properties of tin sulphide thin films by the Photothermal Deflection Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gaied, I.; Akkari, A.; Yacoubi, N.; Kamoun, N.

    2010-03-01

    The optical properties of Tin sulphide thin films grown on a glass substrate by chemical bath deposition were investigated by the Photothermal Deflection Spectroscopy. The experimental normalised amplitude curves of the photothermal signal versus wavelength are compared to the corresponding theoretical ones versus optical absorption coefficient in order to determine the optical absorption spectrum. Then using the Tauc law, one can deduce the energy gap. The influence of the triethanolamine concentration (TEA) in the solution bath on the optical properties was successfully studied.

  18. 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

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

    NASA Astrophysics Data System (ADS)

    Jiang, Jingjing; Wang, Han; Guo, Huaihong; Yang, Teng; Tang, Wen-Shu; Li, Da; Ma, Song; Geng, Dianyu; Liu, Wei; Zhang, Zhidong

    2012-05-01

    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.

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

    PubMed

    Jiang, Jingjing; Wang, Han; Guo, Huaihong; Yang, Teng; Tang, Wen-Shu; Li, Da; Ma, Song; Geng, Dianyu; Liu, Wei; Zhang, Zhidong

    2012-05-01

    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.

  1. Temperature measurement of cold atoms using transient absorption of a resonant probe through an optical nanofibre

    NASA Astrophysics Data System (ADS)

    Kumar, Ravi; Gokhroo, Vandna; Bhushan Tiwari, Vibhuti; Chormaic, Síle Nic

    2016-11-01

    Optical nanofibres are ultrathin optical fibres with a waist diameter typically less than the wavelength of light being guided through them. Cold atoms can couple to the evanescent field of the nanofibre-guided modes and such systems are emerging as promising technologies for the development of atom-photon hybrid quantum devices. Atoms within the evanescent field region of an optical nanofibre can be probed by sending near or on-resonant light through the fibre; however, the probe light can detrimentally affect the properties of the atoms. In this paper, we report on the modification of the local temperature of laser-cooled 87Rb atoms in a magneto-optical trap centred around an optical nanofibre when near-resonant probe light propagates through it. A transient absorption technique has been used to measure the temperature of the affected atoms and temperature variations from 160 μk to 850 μk, for a probe power ranging from 0 to 50 nW, have been observed. This effect could have implications in relation to using optical nanofibres for probing and manipulating cold or ultracold atoms.

  2. Electro-optic properties of novel azobenzene polymers

    NASA Astrophysics Data System (ADS)

    Krupka, O.; Derkowska, B.; Kajzar, F.; Smokal, V.; Studzinsky, S.; Davidenko, N.

    2013-10-01

    Polymers containing azobenzene dyes or azobenzene lateral groups are of special interest for their application as optically active media, particularly, as polarization sensitive media for such applications: optical data storage, surface nanostructuration, photoswitching, alignment of liquid crystals, active optical elements etc. An intensive research was carried out previous years on synthesizis and investigation of the second order nonlinear optical response of azobenzene/polymer systems. The desirable properties of these materials are attributed to the highly efficient photoinduced trans-cis and vice versa isomerization of azobenzene moieties. This transformation is connected with the volume change of molecules, followed by an increase of their rotational mobility. The trans-cis izomerization process is exploited also in all optical poling of polymers and plays an important role in optical depoling. Generally these phenomena are induced by light with frequencies corresponding to one-photon absorption. They are possible also by multiphoton absorptions. In this paper we report the synthesis of side chain methacrylic polymers functionalized with azobenzene chromophores. A reversible change of thin film absorption is observed when illuminating it with monochromatic, linearly polarized light under the applied external DC field. The amount of change depends on the angle between the light polarization and the DC electric field direction.

  3. 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.

  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. 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}.

  6. 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.

  7. 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.

  8. 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

  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 chiral nanotubes

    NASA Astrophysics Data System (ADS)

    Cecilia, Noguez; Román-Velázquez Carlos, E.; Ariadna, Sánchez; Montes Lilia, Meza

    2004-03-01

    A recent theoretical model [1] is applied to study the optical properties chiral nanostructures like carbon nanotubes. We calculate the Circular Dichroism (CD) spectra for carbon nanotubes with different chirality. The calculated CD spectra show features that allow us to distinguish between nanotubes with different indexes of chirality. Other nanostructures, like chiral fullerenes are also investigated.These results provide theoretical support for the quantification of chirality and its measurement, using the CD lineshapes of chiral. This work has been partly financed by CONACyT grant No. 36651-E and by DGAPA-UNAM grants No. IN104201. [1] C. E. Roman-Velazquez, et al., J. of Phys. Chem. B (Letter) 107, 12035 (2003)

  11. 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.

  12. 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.

  13. 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

  14. Urban ozone measurements using differential optical absorption spectroscopy.

    PubMed

    Morales, J A; Treacy, J; Coffey, S

    2004-05-01

    In order to improve the air quality in Europe the European Commission has issued a number of directives with regard to acceptable levels of a range of gaseous pollutants, which includes ozone. Therefore, monitoring of this compound is necessary to comply with EU legislation, to provide improved pollution warnings for those who are sensitive to air pollutants as well as providing valuable data for environmental planning. Open-path spectroscopic techniques, such as differential optical absorption spectroscopy (DOAS), are ideal for monitoring pollutants because of the advantages they offer over classical methods and point-source analysers. A DOAS system has been installed in Dublin city centre to monitor a range of criteria pollutants including ozone. Observations of urban background ozone concentrations are presented. The measurements are compared with those obtained using a UV point-source analyser and are presented in the context of the current EU directive. The influence of trans-boundary pollution from mainland Europe leading to ozone episodes is also discussed. Observations of high ozone during this measurement campaign coincided with the influx of photochemically polluted air masses which originated over continental Europe. For the analysed time interval, the data suggest that the ground ozone level in Dublin might be significantly influenced by long-range transport from the United Kingdom and continental Europe. PMID:14963627

  15. UV optical absorption spectra analysis of spodumene crystals from Brazil

    NASA Astrophysics Data System (ADS)

    Isotani, Sadao; Watari, Kazunori; Mizukami, Akiyoshi; Bonventi, Waldemar; Ito, Amando Siuiti

    2007-04-01

    The spectral decomposition analysis was applied to the optical absorption spectra of spodumene crystals from the Brazilian eastern pegmatitic province. The analyzed samples were natural, treated at 400 °C for 24 h and those irradiated with γ rays of 60Co with doses up to 5 MGy. The attributions of the lines were made taking in account highly accurate quantum mechanical calculations. The heated sample had only three lines, which were not affected by irradiation. One of them at 7.58 eV was attributed to an oxygen vacancy defect and the other two at 5.07 and 4.64 eV to a peroxy-type defect. The analysis of the growth of the lines with the irradiation showed that they belong to two groups of defects. The first group of lines at 4.2, 5.3 and 5.9 eV was attributed to a silanone-type defect. The other group of lines at 1.36, 2.0, 2.6, 3.6 and 5.0 eV was attributed to a type of Mn 3+ defect. The natural and irradiated samples also showed a line at 2.3 eV, which was attributed to another type of diamagnetic Mn 3+ defect.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1984-08-01

    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.

  18. 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

  19. Optical properties of liquid Se-Te alloys

    NASA Astrophysics Data System (ADS)

    Silva, Larry A.; Cutler, Melvin

    1990-10-01

    Thin films have been used to determine the optical properties of the liquid-alloy system SexTe100-x in the photon energy range of 0.4 to 5.0 eV, and at temperatures from the melting point to 500 °C. These liquids are semiconductors at Se-rich compositions, and undergo a transition to metallic behavior at high Te concentrations. The effects of this transition first appear in the optical data at 80 at. % Te. Possible forms for the electronic band structure in the semiconducting phase of the liquid are derived from the nondirect transition model for optical absorption. The optical properties of liquid Te (metallic phase) are separated into intraband and interband components, modeling the intraband component by Drude behavior, to test previously proposed mechanisms for the semiconductor-metal transition. Our results are consistent with the preservation of two-fold covalent bonding across this transition, and predict a ~0.4 eV gap between a Fermi level within the valence-band and the conduction-band edge. We have also measured the sub-band-gap absorption coefficient in semiconducting liquids containing 0, 20, and 40 at. % Te, and find that the extent of the exponential absorption edge decreases with increasing Te concentration.

  20. 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.

  1. 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.

  2. 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.

  3. Light absorption properties of brown carbon in the high Himalayas

    NASA Astrophysics Data System (ADS)

    Kirillova, Elena N.; Marinoni, Angela; Bonasoni, Paolo; Vuillermoz, Elisa; Facchini, Maria Cristina; Fuzzi, Sandro; Decesari, Stefano

    2016-08-01

    The light-absorbing properties of water-soluble brown carbon (WS-BrC) and methanol-soluble brown carbon (MeS-BrC) were studied in PM10 aerosols collected at the "Nepal Climate Observatory-Pyramid" (NCO-P) station (5079 m above sea level) during the period 2013-2014. The light absorption coefficients of WS-BrC and MeS-BrC were the highest during the premonsoon season and the lowest during monsoon. MeS-BrC absorbs about 2 times higher at 365 nm and about 3 times more at 550 nm compared to WS-BrC. The mass absorption cross section (MAC) of WS-BrC measured at 365 nm is similar to that observed previously at South Asian low-altitude sites. Fractional solar radiation absorption by BrC compared to BC considering the full solar spectrum showed that WS-BrC absorbs 4 ± 1% and MeS-BrC absorbs 9 ± 2% compared to BC at NCO-P. Such ratios become 8 ± 1% (for WS-BrC respect to BC) and 17 ± 5% (for MeS-BrC respect to BC) when accounting for correction factors proposed by previous studies to convert absorption coefficients in bulk solutions into light absorption by accumulation mode aerosol particles. These results confirm the importance of BrC in contributing to light-absorbing aerosols in this region of the world. However, the BrC absorption at 550 nm appears small compared to that of BC (1-5%, or 3-9% with conversion factors), and it is lower compared to global model estimates constrained by Aerosol Robotic Network observations. Finally, our study provides no clear evidence of a change in the fractional contribution of BrC with respect to BC to light absorption in the middle troposphere respect to the Indo-Gangetic plain boundary layer.

  4. 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

  5. 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

  6. Optical absorption and photocurrent enhancement in semi-insulating gallium arsenide by femtosecond laser pulse surface microstructuring.

    PubMed

    Zhao, Zhen-Yu; Song, Zhi-Qiang; Shi, Wang-Zhou; Zhao, Quan-Zhong

    2014-05-19

    We observe an enhancement of optical absorption and photocurrent from semi-insulating gallium arsenide (SI-GaAs) irradiated by femtosecond laser pulses. The SI-GaAs wafer is treated by a regeneratively amplified Ti: Sapphire laser of 120 fs laser pulse at 800 nm wavelength. The laser ablation induced 0.74 μm periodic ripples, and its optical absorption-edge is shifted to a longer wavelength. Meanwhile, the steady photocurrent of irradiated SI-GaAs is found to enhance 50%. The electrical properties of samples are calibrated by van der Pauw method. It is found that femtosecond laser ablation causes a microscale anti-reflection coating surface which enhances the absorption and photoconductivity.

  7. 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.

  8. 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

  9. Electronic Structure and Optical Properties of Boron Difluoride Dibenzoylmethane Derivatives.

    PubMed

    Tikhonov, Sergey A; Vovna, Vitaliy I; Gelfand, Natalia A; Osmushko, Ivan S; Fedorenko, Elena V; Mirochnik, Anatoliy G

    2016-09-22

    Electronic structure and optical properties of boron difluoride dibenzoylmethanate BF2Dbm and its four derivatives were studied using X-ray photoelectron spectroscopy, absorption and luminescence spectroscopy, and quantum chemistry (DFT and TDDFT). In a series of the studied compounds, the relationship of molecular design and optical properties has been revealed. At the transition from BF2Dbm to BF2Dbm(OCH3)2, the HOMO-LUMO energy gap decreases, resulting in a bathochromic shift of the optical spectra. Substitution of one methoxy group by the nitro group in BF2Dbm(OCH3)2 causes a decrease in the contribution of the chelate ring π-orbital in the LUMO, resulting in a lower value of charge transfer from the substituents to the chelate ring in the case of the first excited state, which determines the characteristics of the main absorption bands. The nitro group transition from the m- to p-position of the benzene ring causes a change in the nature of the main bands of the optical spectra due to the increase of the splitting value of the LUMO and LUMO+1 levels. The main band in the optical spectra of the complex containing the C10H7 group is associated with the charge transfer transitions. PMID:27580170

  10. Optical properties of chiral nanostructures

    NASA Astrophysics Data System (ADS)

    Cecilia, Noguez; Román-Velázquez, Carlos E.; Garzón, Ignacio L.

    2004-03-01

    We present a computational model to study the optical properties chiral nanostructures[1] . In this work the nanostructures of interest are composed by N atoms, where each one is represented by a polarizable point dipole located at theposition of the atom. We assume that the dipole located is characterized by a polarizability. The nanostructure is excited by a circularly polarized incident wave, such that, each dipole is subject to a total electric field due to: (i) the incident radiation field, plus (ii) the radiation field resulting from all of the other induced dipoles. Once we solve the complex-linear equations, the dipole moment on each atom in the cluster can be determined and we can find the extinction cross section of the whole nanoparticle. Circular dichroism (CD) spectra of chiral bare and thiol-passivated gold nanoclusters have been calculated within the dipole approximation. The calculated CD spectra show features that allow us to distinguish between clusters with different indexes of chirality. The main factor responsible of the differences in the CD lineshapes is the distribution of interatomic distances that characterize the chiral cluster geometry. These results provide theoretical support for the quantification of chirality and its measurement, using the CD lineshapes of chiral metal nanoclusters. [1] C. E. Roman-Velazquez, et al., J. of Phys. Chem. B (Letter) 107, 12035 (2003) This work has been partly supported by DGAPA-UNAM grants No. IN104201 and IN104402, and by CONACyT grant 36651-E.

  11. 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.

  12. 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

  13. 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.

  14. On the relation between X-ray absorption and optical extinction in AGN

    NASA Astrophysics Data System (ADS)

    Ordovás-Pascual, Ignacio; Mateos, Silvia; Carrera, Francisco J.; Wiersema, Klaas; Caccianiga, Alessandro; Severgnini, Paola; Della Ceca, Roberto; Ballo, Lucia; Moretti, Alberto

    2016-08-01

    According to the Unified Model of Active Galactic Nuclei (AGN), an X-ray unabsorbed AGN should appear as unobscured in the optical (Type-1) and viceversa (Type-2). However, there is an important fraction (10-30%) of AGN whose optical and X-ray classifications do not match. To provide insight into the origin of such apparent discrepancies, we have conducted two analyses: 1) a detailed study of the UV-to-near-IR emission of two X-ray unabsorbed Type-2 AGN drawn from the Bright Ultra-Hard XMM-Newton Survey (BUXS); 2) a statistical analysis of the optical obscuration and X-ray absorption properties of 159 Type-1 AGN drawn from BUXS to determine the distribution of dust-to-gas ratios in AGN over a broad range of luminosities and redshifts. In our works we have also determined the impact of contamination from the AGN hosts in the optical classification of AGNs. Our studies are already provided very exciting results such as the detection of objects with extreme dust-to-gas ratios, between 300-10000 times below the Galactic dust-to-gas ratio.

  15. Optical absorption characteristics of polycrystalline AgGaSe2 thin films

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. R. A.; Firoz Hasan, S. M.

    2006-12-01

    Silver gallium di-selenide (AgGaSe2) composite thin films have been formed onto ultrasonically and chemically cleaned glass substrates by in situ thermal annealing of the stack of successively evaporated individual elemental layers in vacuum. The structural properties of the films were ascertained by the x-ray diffraction method. The diffractogram indicated that these films were polycrystalline in nature having tetragonal structure with lattice parameters, a ap 6.00 Å and c ap 10.92 Å and average grain dimension 40 nm. The optical properties and atomic compositions of the films have been determined by UV-VIS-NIR spectrophotometry (photon wavelength ranging between 300 and 2500 nm) and energy dispersive analysis of x-ray, respectively. The typical optical absorption characteristic of the films has been critically analysed. The optical absorption coefficients vary from 103 to 105 cm-1 in the measured wavelength range of photons. The films have more than one type of fundamental electronic transitions. Direct allowed and direct forbidden transitions vary from 1.628 to 1.748 eV and 2.077 to 2.193 eV, respectively, depending on the composition of the films. The former transitions are found to have a general tendency to be symmetric around non-molecularity ΔX = 0, defined by ΔX = [(Ag/Ga)] - 1, while the latter shows no such dependence. Stoichiometric or slightly silver-deficient films show electron transition energies closer to the single crystal value. Spin-orbit splitting of the valence band becomes minimum at perfect stoichiometry.

  16. 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

  17. Influence of absorption and scattering on the quantification of fluorescence diffuse optical tomography using normalized data.

    PubMed

    Abascal, Juan Felipe Perez-Juste; Aguirre, Juan; Chamorro-Servent, Judit; Schweiger, Martin; Arridge, Simon; Ripoll, Jorge; Vaquero, Juan J; Desco, Manuel

    2012-03-01

    Reconstruction algorithms for imaging fluorescence in near infrared ranges usually normalize fluorescence light with respect to excitation light. Using this approach, we investigated the influence of absorption and scattering heterogeneities on quantification accuracy when assuming a homogeneous model and explored possible reconstruction improvements by using a heterogeneous model. To do so, we created several computer-simulated phantoms: a homogeneous slab phantom (P1), slab phantoms including a region with a two- to six-fold increase in scattering (P2) and in absorption (P3), and an atlas-based mouse phantom that modeled different liver and lung scattering (P4). For P1, reconstruction with the wrong optical properties yielded quantification errors that increased almost linearly with the scattering coefficient while they were mostly negligible regarding the absorption coefficient. This observation agreed with the theoretical results. Taking the quantification of a homogeneous phantom as a reference, relative quantification errors obtained when wrongly assuming homogeneous media were in the range +41 to +94% (P2), 0.1 to -7% (P3), and -39 to +44% (P4). Using a heterogeneous model, the overall error ranged from -7 to 7%. In conclusion, this work demonstrates that assuming homogeneous media leads to noticeable quantification errors that can be improved by adopting heterogeneous models.

  18. Influence of absorption and scattering on the quantification of fluorescence diffuse optical tomography using normalized data

    NASA Astrophysics Data System (ADS)

    Abascal, Juan Felipe Perez-Juste; Aguirre, Juan; Chamorro-Servent, Judit; Schweiger, Martin; Arridge, Simon; Ripoll, Jorge; Vaquero, Juan J.; Desco, Manuel

    2012-03-01

    Reconstruction algorithms for imaging fluorescence in near infrared ranges usually normalize fluorescence light with respect to excitation light. Using this approach, we investigated the influence of absorption and scattering heterogeneities on quantification accuracy when assuming a homogeneous model and explored possible reconstruction improvements by using a heterogeneous model. To do so, we created several computer-simulated phantoms: a homogeneous slab phantom (P1), slab phantoms including a region with a two- to six-fold increase in scattering (P2) and in absorption (P3), and an atlas-based mouse phantom that modeled different liver and lung scattering (P4). For P1, reconstruction with the wrong optical properties yielded quantification errors that increased almost linearly with the scattering coefficient while they were mostly negligible regarding the absorption coefficient. This observation agreed with the theoretical results. Taking the quantification of a homogeneous phantom as a reference, relative quantification errors obtained when wrongly assuming homogeneous media were in the range +41 to +94% (P2), 0.1 to -7% (P3), and -39 to +44% (P4). Using a heterogeneous model, the overall error ranged from -7 to 7%. In conclusion, this work demonstrates that assuming homogeneous media leads to noticeable quantification errors that can be improved by adopting heterogeneous models.

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

    DOE PAGES

    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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

    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 (μs'/μa) 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.

  2. 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.

  3. Optical absorption coefficients in GaN/Al(Ga)N double inverse parabolic quantum wells under static external electric field

    NASA Astrophysics Data System (ADS)

    El Kadadra, A.; Fellaoui, K.; Abouelaoualim, D.; Oueriagli, A.

    2016-09-01

    In this work, we have investigated theoretically the effects of applied electric field on the linear and nonlinear optical properties in a GaN/AlxGa1-xN double inverse parabolic quantum well for different Al concentrations at the well center. Our calculations are based on the potential morphing method in the effective mass approximation. The systematic theoretical investigation contains results with all possible combinations of the involved parameters, such as quantum well width, quantum barrier width, Al concentration at each well center and magnitude of the external electric field. Our results show that the electric fields strengths, the parameter of nanostructure and incident optical intensity have a great effect on the optical characteristics of these nanostructures. Thus, the absorption coefficients which can be suitable for great performance optical modulators and multiple infrared optical device applications can be easily obtained by tuning the external electric field value and the Al concentration at the well center.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. AlN bandgap temperature dependence from its optical properties

    NASA Astrophysics Data System (ADS)

    Silveira, E.; Freitas, J. A.; Schujman, S. B.; Schowalter, L. J.

    2008-08-01

    In the present work we report on the AlN gap energy temperature dependence studied through the optical properties of high-quality large bulk AlN single crystals grown by a sublimation-recondensation technique. The cathodoluminescence, transmission/absorption as well as optical reflectance measurements at low temperature show a clear feature at about 6.03 eV, which could be attributed to the free exciton A. Even using a rather thick sample it was possible to observe the absorption due to the free exciton A in this energy range due to its large binding energy. We followed the temperature evolution of these features up to room temperature and inferred the gap energy temperature dependence using the exciton binding energy obtained by our group in the past.

  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. 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.

  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. 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

  13. 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.

  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

    NASA Astrophysics Data System (ADS)

    Zhang, Mingda; Zhang, Xiangdong

    2015-02-01

    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.

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

    PubMed

    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

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. [The Establishment of the Method of the Fiber Optic Chemical Sensor Synchronous Absorption-Fluorescence].

    PubMed

    Zhang Li-hua; Iburaim, Arkin

    2016-03-01

    A new method of simultaneously measuring fiber-optic chemical sensor absorption spectrum and fluorescence spectrum is established. Make synchronous absorption-fluorescence cuvette, establish synchronous absorption-fluorescence spectrometry instrumentation combined by fiber optic chemical sensor technology, measure the synchronous absorption-fluorescence spectrums of solutions of rhodamine B, vitamin B2 and vitamin B6, compared by absorption spectroscopy measured by traditional UV-Visible photometric method and fluorescence spectroscopy measured by traditional fluorescence method. Synchronous absorption-fluorescence method measure absorption spectrums and fluorescence spectrums the same to traditional photometric and fluorescence spectroscopy of rhodamine B, vitamin B2 and vitamin B6. The maximum wavelength of fluorescence intensity method has high accuracy relatively compared with fluorescence, but the maximum wavelength of absorption has a slight deviation. Synchronous absorption-fluorescence method means simultaneously measure the absorption spectrums and fluorescence spectrums of the fluorescent substance, making two spectrums to one. The method measured the maximum emission wavelength with high accuracy, though in measuring maximum absorption wavelength there is a slight deviation, but it is worth further studying. PMID:27400519

  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. Effect of phytoplankton community composition and cell size on absorption properties in eutrophic shallow lakes: field and experimental evidence.

    PubMed

    Zhang, Yunlin; Yin, Yan; Wang, Mingzhu; Liu, Xiaohan

    2012-05-21

    We investigated phytoplankton absorption properties of Lake Taihu, in the spring and summer of 2005 and 2006, and for 17 days studied laboratory cultures of Scenedesmus obliquus (chlorophyta) and Microcystis aeruginosa (cyanophyta) to determine the effect of phytoplankton community composition and cell size on the absorption properties. There were significant seasonal differences in phytoplankton community composition and absorption coefficients. In spring, the phytoplankton community was dominated by chlorophyta with large cells, whereas in summer was dominated by cyanophyta with small cells. Phytoplankton absorption coefficients increased significantly from spring to summer, with the increase in chlorophyll a (Chla) concentration. In addition, Chla-specific absorption coefficients increased with the phytoplankton community succession from chlorophyta to cyanophyta. In culture, the cells density of S. obliquus was generally lower than that of M. aeruginosa, and Chla concentrations of S. obliquus were significantly higher than those of M. aeruginosa. Correspondingly, the Chla-specific absorption coefficients of S. obliquus were significantly lower than those of M. aeruginosa. Significant exponential correlations were found between absorption and Chla-specific absorption coefficients and Chla concentration for S. obliquus and M. aeruginosa. In addition, we developed a model to predict absorption and Chla-specific absorption coefficients using Chla concentration and cell size when data from two species was grouped together. Field and experimental results both showed that the Chla-specific absorption coefficients of cyanophyta were significantly higher than those of chlorophyta. The variability in specific absorption can attributed to phytoplankton community composition, cell size and pigment composition. As phytoplankton community composition changed significantly with season in the lake, and as variation in the cell sizes and accessory pigments of the phytoplankton

  4. Quantitative photoacoustic tomography: Recovery of optical absorption coefficient maps of heterogeneous media

    NASA Astrophysics Data System (ADS)

    Yuan, Zhen; Jiang, Huabei

    2006-06-01

    We report on experimental demonstration of photoacoustic tomography for reconstructing the optical absorption coefficient images of heterogeneous media. Photoacoustic images are obtained from a series of tissuelike phantom experiments using a finite element-based reconstruction algorithm coupled with a scanning photoacoustic imaging system. The experimental results show that optical absorption images can be quantitatively reconstructed when the photon diffusion model is coupled with the Helmholtz photoacoustic wave equation.

  5. Thermoluminescence, electron paramagnetic resonance and optical absorption in natural and synthetic rhodonite crystals

    NASA Astrophysics Data System (ADS)

    Paião, J. R. B.; Watanabe, S.

    2008-10-01

    Thermoluminescence, electron paramagnetic resonance and optical absorption properties of rhodonite, a natural silicate mineral, have been investigated and compared to those of synthetic crystal, pure and doped. The TL peaks grow linearly for radiation dose up to 4 kGy, and then saturate. In all the synthetic samples, 140 and 340°C TL peaks are observed; the difference occurs in their relative intensities, but only 340°C peak grows strongly for high doses. Al2O3 and Al2O3 + CaO-doped synthetic samples presented several decades intenser TL compared to that of synthetic samples doped with other impurities. A heating rate of 4°C/s has been used in all the TL readings. The EPR spectrum of natural rhodonite mineral has only one huge signal around g = 2.0 with width extending from 1,000 to 6,000 G. This is due to Mn dipolar interaction, a fact proved by numerical calculation based on Van Vleck dipolar broadening expression. The optical absorption spectrum is rich in absorption bands in near-UV, visible and near-IR intervals. Several bands in the region from 540 to 340 nm are interpreted as being due to Mn3+ in distorted octahedral environment. A broad and intense band around 1,040 nm is due to Fe2+. It decays under heating up to 900°C. At this temperature it is reduced by 80% of its original intensity. The pink, natural rhodonite, heated in air starts becoming black at approximately 600°C.

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Microwave absorption properties of graphite flakes-phenolic resin composite

    NASA Astrophysics Data System (ADS)

    Gogoi, Jyoti P.; Gogoi, Pragyan J.; Bhattacharyya, Nidhi S.

    2013-01-01

    In the present investigation, microwave absorption properties of a conductor back single layer designed on graphite flakes (GF)-novolac phenolic resin (NPR) composites is studied. The complex permittivity of the developed composite enhance for higher GF percentages. The reflection loss(RL) measured using E8362C VNA shows a maximum RL values -25 dB at 9.8 GHz for 7 wt. % composition with -10 dB bandwidth of 0.3 GHz. The developed composites are being light weight and cost effective shows potential to be used as dielectric absorber.

  13. 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.

  14. 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.

  15. Tuning optical absorption and photoexcited recombination dynamics in La1-xSrxFeO3-δ through A-site substitution and oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Smolin, Sergey; Scafetta, Mark; Choquette, Amber; Sfeir, Matthew; Baxter, Jason; May, Steven

    We study optical absorption and recombination dynamics in La1-xSrxFeO3-δ thin films, uncovering the effects of tuning nominal Fe valence via A-site substitution and oxygen stoichiometry. Variable angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25 eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic optoelectronic properties were studied with ultrafast transient reflectance spectroscopy, revealing similar nanosecond photoexcited carrier lifetimes for oxygen deficient and stoichiometric films with the same nominal Fe valence. These results demonstrate that while the static optical absorption is strongly dependent on Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in the recombination kinetics. Nsf: ECCS-1201957, MRI DMR-0922929, MRI DMR-1040166. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

  16. 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.

  17. Systems having optical absorption layer for mid and long wave infrared and methods for making the same

    DOEpatents

    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.

  18. Luminescence and photoinduced absorption in ytterbium-doped optical fibres

    NASA Astrophysics Data System (ADS)

    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.

    2011-12-01

    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: Al2O3 : SiO2, Al2O3 : Yb2O3 : SiO2, and P2O5 : Yb2O3 : SiO2. 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 Yb3+ ions to Yb2+. 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 Yb3+ ions.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Structure and optical properties of CdSe chalcogenide semiconductors

    NASA Astrophysics Data System (ADS)

    Ganaie, Mohsin; Prince, Zulfequar, M.

    2015-08-01

    CdSe bulk sample has been prepared by melt-quenching technique and were characterized with XRD, SEM, FTIR, and electrical measurements. Thin films were deposited by thermal evaporation technique on ultra clean glass substrates under a high vacuum of 10-6 Torr. An XRD measurement reveals the coexistence of glassy and crystalline phase in bulk sample. SEM studies shows single phase, porous, and granular surface morphology of powder CdSe alloy. Optical properties (optical gap, absorption coefficient, extinction coefficient, refractive index) are calculated in the range of 190-1100nm. Analysis of the optical measurement shows that the non-direct transition is predominant and the band gap come outs to be 1.751eV. Dc conductivity measurement is thermally activated process which shows the semiconducting nature of the sample having activation energy 0.31eV.

  4. Optical properties of cadmium telluride in the transparence region

    NASA Astrophysics Data System (ADS)

    Savitskii, A. V.; Slipeniuk, T. S.; Ulianitskii, K. S.

    1980-11-01

    The paper describes an experimental study of the influence of the means of surface finishing of CdTe specimens and the degree of their structural perfection on their optical properties in the infrared region (2-25 microns). Single-crystal specimens obtained by the Bridgeman method were used. The transmission coefficient was studied as a function of incident-radiation wavelength for stage-by-stage mechanical (i.e., abrasive) finishing of the surface. Measurements of optical transmission have revealed a lengthwise optical inhomogeneity in the specimen. In addition, it is shown that the examination of nonselective absorption by free carriers can be an effective tool for the fault inspection of CdTe crystals.

  5. 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.

  6. Microwave absorption properties of carbon nanotubes dispersed in alumina ceramic

    NASA Astrophysics Data System (ADS)

    Chojnacki, E.; Huang, Q.; Mukherjee, A. K.; Holland, T. B.; Tigner, M.; Cherian, K.

    2011-12-01

    Ceramic nanocomposites of alumina and carbon nanotubes (CNTs) are experimentally studied for use as microwave absorbers in particle accelerators. The weight percentage of multi-walled CNTs in SPS sintered nanocomposite samples is varied from 0.5 to 10% and the complex permittivity is measured. The RF absorption is strong and relatively flat in the frequency band 1-40 GHz for a CNT weight percentage in the range 1-2.5%, which is just above the percolation threshold. The permittivity is observed to increase dramatically with increasing CNT weight percentage above the percolation threshold as observed elsewhere, and in accordance with theoretical treatments. The electromagnetic properties of the nanocomposites are little changed in going from 294 K to 77 K. The DC conductivity of the alumina-CNT nanocomposite is also sufficient to drain static charge in particle accelerator beamline environments, even at cryogenic temperatures. Fabrication of the nanocomposites using an industrial RF sintering process compatible with large sizes shows that the microwave absorption properties of small samples are similar to those of the SPS sintered samples.

  7. Optical absorption of sodium copper chlorophyllin thin films in UV-vis-NIR region.

    PubMed

    Farag, A A M

    2006-11-01

    The optical absorption studies of sodium copper chlorophyllin thin films (SCC), prepared by spray pyrolysis, in the UV-vis-NIR region was reported for the first time. Several new discrete transitions are observed in the UV-vis region of the spectra in addition to a strong continuum component in the IR region. The spectra of the infrared absorption allow characterization of vibration modes for the powder and thin films of SCC. The absorption spectrum recorded in the UV-vis region showed different absorption bands, namely the Soret (B) in the region 340-450 nm and Q-band in the region 600-700 nm and other band labeled N in the 240-320 region. Some important spectral parameters namely optical absorption coefficient (alpha), molar extinction coefficient (epsilon(molar)), oscillator strength (f), electric dipole strength (q(2)) and absorption half bandwidth (Deltalambda) of the principle optical transitions were evaluated. The analysis of the absorption coefficient in the absorption region revealed direct transitions and the energy gap was estimated as 1.63 eV. Discussion of the obtained results and their comparison with the previous published data are also given.

  8. 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.

  9. Acousto-optic differential optical absorption spectroscopy for atmospheric measurement of nitrogen dioxide in Hong Kong.

    PubMed

    Cheng, Andrew Y S; Chan, M H

    2004-12-01

    Measurement of the atmospheric concentration of nitrogen dioxide (NO(2)) pollutant was demonstrated by differential optical absorption spectroscopy (DOAS) using a visible acousto-optic tunable filter. In a traditional spectral scanning DOAS system for atmospheric concentration monitoring, a highly stable light source is required. When the light intensity fluctuates during scanning, the concentration retrieval will be inaccurate. In order to reduce the error due to intensity fluctuations, a modified DOAS system has been developed by introducing a broadband light intensity monitoring channel. Using the measured intensity of the broadband channel as the intensity of the light source, the spectrum can be de-biased and the residual intensity variation will primarily result from atmospheric extinction. In addition, by employing the lock-in detection technique, the background light interference is also removed in the modified DOAS system. The atmospheric NO(2) concentration measurement was performed at the campus of City University of Hong Kong, and the results were compared with the concentration reported from a nearby monitoring station in Sham Shui Po, operated by the Hong Kong Environmental Protection Department.

  10. 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.

  11. 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

  12. 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.

  13. Theory of absorption bands in molecular dimers: Interpolating between optical asymmetries

    SciTech Connect

    Wagenknecht, Hans; Esser, Bernd

    2003-02-01

    Absorption band shapes of an asymmetric dimer system constituted by monomers with different excitation energies and optical transition matrix elements are considered in the semiclassical parameter region. Optical transition matrix elements originating from arbitrary initial vibrational states are analyzed on the basis of a spin representation of the eigenstates of an associated symmetry broken spin-boson Hamiltonian. Correlations between the spin-down and spin-up coefficients of these eigenstates are shown to exist and investigated in detail. Using these correlations, an asymmetry interpolation of the intensity of absorption lines between dimer configurations with different optical monomer transition matrix elements is proposed.

  14. 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.

  15. Singular topology of optical absorption in biaxial crystals.

    PubMed

    Joly, Simon; Petit, Yannick; Boulanger, Benoît; Segonds, Patricia; Félix, Corinne; Ménaert, Bertrand; Aka, Gérard

    2009-10-26

    We show for the first time that biaxial crystals exhibit continua of directions of propagation where the absorption coefficient is the same for the two associated polarization modes. This statement is supported by both calculations and experimental data obtained in Nd:YCOB.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Effect of disorder on the optical properties of short period superlattices

    NASA Technical Reports Server (NTRS)

    Strozier, J. A.; Zhang, Y. A.; Horton, C.; Ignatiev, A.; Shih, H. D.

    1993-01-01

    The optical properties of disordered short period superlattices are studied using a one-dimensional tight-binding model. A difference vector and disorder structure factor are proposed to characterize the disordered superlattice. The density of states, participation number, and optical absorption coefficients for both ordered and disordered superlattices are calculated as a function of energy. The results show that introduction of disorder into an indirect band gap material enhances the optical transition near the indirect band edge.

  2. 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.

  3. 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.

  4. Correction to the Beer-Lambert-Bouguer law for optical absorption.

    PubMed

    Abitan, Haim; Bohr, Henrik; Buchhave, Preben

    2008-10-10

    The Beer-Lambert-Bouguer absorption law, known as Beer's law for absorption in an optical medium, is precise only at power densities lower than a few kW. At higher power densities this law fails because it neglects the processes of stimulated emission and spontaneous emission. In previous models that considered those processes, an analytical expression for the absorption law could not be obtained. We show here that by utilizing the Lambert W-function, the two-level energy rate equation model is solved analytically, and this leads into a general absorption law that is exact because it accounts for absorption as well as stimulated and spontaneous emission. The general absorption law reduces to Beer's law at low power densities. A criterion for its application is given along with experimental examples.

  5. 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.

  6. Optical properties of nanowire metamaterials with gain

    NASA Astrophysics Data System (ADS)

    Lima, Joaquim; Adam, Jost; Rego, Davi; Esquerre, Vitaly; Bordo, Vladimir

    2016-11-01

    The transmittance, reflectance and absorption of a nanowire metamaterial with optical gain are numerically simulated and investigated. It is assumed that the metamaterial is represented by aligned silver nanowires embedded into a semiconductor matrix, made of either silicon or gallium phosphide. The gain in the matrix is modeled by adding a negative imaginary part to the dielectric function of the semiconductor. It is found that the optical coefficients of the metamaterial depend on the gain magnitude in a non-trivial way: they can both increase and decrease with gain depending on the lattice constant of the metamaterial. This peculiar behavior is explained by the field redistribution between the lossy metal nanowires and the amplifying matrix material. These findings are significant for a proper design of nanowire metamaterials with low optical losses for diverse applications.

  7. Optical properties of porous chalcogenide films for sensor application

    NASA Astrophysics Data System (ADS)

    Lalova, A.; Todorov, R.

    2012-12-01

    The object of the present work is investigation of the optical properties of obliquely deposited thin films from As - S - Ge system. Aiming to obtain high porous coatings the deposition rate was varied in the range of 0.05-10 nm/s. The conditions for deposition of thin As - S - Ge films with columnar structure and high porosity were established. The role of the actual deposition conditions on the optical properties is examined. The optical constants (refractive index, n and absorption coefficient, α) and thickness, d as well as the optical band gap, Eg, and slope parameter B in dependence of the deposition angle and rate are determined from specrophotometric measurements in the spectral range 400-2000 nm applying the Swanepoel's envelope method and Tauc's procedure. Increasing of the value of n from 2.40 to 1.83 for thin film with composition As10Ge30S60 with increasing deposition angle from 0° to 75° is observed. The possibility of using the thin films for optical sensing of SO2 and H2S was examined. Reversible changes of the refractive index, Δn = 0.015 were observed as a consequence of treatment virgin - exposure to H2SO4 vapors- annealing at 120 °C.

  8. 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

  9. 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.

  10. In situ optical absorption mercury continuous emission monitor.

    PubMed

    Thiebaud, Jérôme; Thomson, Murray J; Mani, Reza; Morrow, William H; Morris, Eric A; Jia, Charles Q

    2009-12-15

    This paper reports the development of an in situ continuous emission monitor (CEM) for measuring elemental mercury (Hg(0)) concentration in the exhaust stream of coal-fired power plants. The instrument is based on the ultraviolet atomic absorption of a mercury lamp emission line by elemental mercury and a light-emitting diode (LED) background correction system. This approach allows an in situ measurement since the absorption of other species such as SO(2) can be removed to monitor the Hg(0) contribution only. Proof of concept was established through a laboratory-based investigation, and a limit of detection, [Hg(0)](min), of 2 microg/m(3) was measured for a 1-min averaged sample and an absorption path length of 49 cm. [Hg(0)](min) is anticipated to be better than 0.2 microg/m(3) across a 7 m diameter stack. Finally, the apparatus was field-tested in a 230 MW coal-fired power plant. The operability of the measurement in real conditions was demonstrated, leading to the first Hg(0) concentration values recorded by the in situ CEM. Comparison with an accepted standard method is required for validation.

  11. 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.

  12. Optical Properties of Selective Emitter Materials for Thermophotovoltaic Applications

    NASA Technical Reports Server (NTRS)

    Hambourger, Paul D.

    1996-01-01

    We investigate the optical properties of new "selective emitter" materials for possible use in high-efficiency thermophotovoltaic power systems. These are systems which directly convert heat to radiation at a wavelength closely matched to the bandgap energy of the solar cell. Candidate materials which have strong absorption lines fairly close to the bandgap of good solar-cell materials were chosen for study. Their emittance was measured as a function of wavelength to evaluate their promise as selective TPV emitters. Useful and informative results were obtained. Some of these results were presented at a January 1996 solar energy conference of the American Institute of Aeronautics and Astronautics.

  13. Optical Properties of Poly(pentafluorophenylsilyne) Prepared by Electrochemical Polymerization

    NASA Astrophysics Data System (ADS)

    Watanabe, Akira; Ito, Osamu; Miwa, Takao

    1995-09-01

    The first polysilyne having a perfluorinated aryl group, poly(pentafluorophenylsilyne), was prepared through a combination of the Grignard reaction of bromopentafluorobenzene and tetrachlorosilane and the subsequent electrochemical polymerization using a magnesium electrode. The absorption and emission spectra of the polymer showed the characteristic of polysilyne which has a silicon network structure. The emission decay of poly (pentafluorophenylsilyne) measured by the time-resolved single photon counting technique showed non-single exponential kinetics. These optical properties were compared with those of poly(phenylsilyne).

  14. The optical properties and spectral features of malignant skin melanocytes in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Goryachuk, A. A.; Begaeva, V. A.; Khodzitsky, M. K.; Truloff, A. S.

    2016-08-01

    The samples of cells of mice's melanocytes have been investigated. Their optical properties and spectral features were investigated by terahertz time-domain spectroscopy (TDS) in transmission mode. It was found that the optical properties of oncological melanocytes and normal cells are different and oncological cells have spectral features of absorption coefficient so it can be concluded that it is easy to discriminate mice's oncological skin melanocytes by using THz TDS.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

    2016-03-28

    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

  20. UV optical properties of thin film oxide layers deposited by different processes.

    PubMed

    Pellicori, Samuel F; Martinez, Carol L

    2011-10-01

    UV optical properties of thin film layers of compound and mixed oxide materials deposited by different processes are presented. Japan Electron Optics Laboratory plasma ion assisted deposition (JEOL PIAD), electron beam with and without IAD, and pulsed DC magnetron sputtering were used. Comparisons are made with published deposition process data. Refractive indices and absorption values to as short as 145 nm were measured by spectroscopic ellipsometry (SE). Electronic interband defect states are detected that are deposition-process dependent. SE might be effective in identifying UV optical film quality, especially in defining processes and material composition beneficial for high-energy excimer laser applications and environments requiring stable optical properties.

  1. Optical properties of iron oxides

    NASA Astrophysics Data System (ADS)

    Musfeldt, Janice

    2012-02-01

    Magnetoelectric coupling in materials like multiferroics, dilute magnetic semiconductors, and topological insulators has attracted a great deal of attention, although most work has been done in the static limit. Optical spectroscopy offers a way to investigate the dynamics of charge-spin coupling, an area where there has been much less effort. Using these techniques, we discovered that charge fluctuation in LuFe2O4, the prototypical charge ordered multiferroic, has an onset well below the charge ordering transition, supporting the ``order by fluctuation'' mechanism for the development of charge order superstructure. Bragg splitting and large magneto-optical contrast suggest a low temperature monoclinic distortion that can be driven by both temperature and magnetic field. At the same time, dramatic splitting of the LuO2 layer phonon mode is attributed to charge-rich/poor proximity effects, and its temperature dependence reveals the antipolar nature of the W layer pattern. Using optical techniques, we also discovered that α-Fe2O3, a chemically-similar parent compound and one of the world's oldest and most iconic antiferromagnetic materials, appears more red in applied magnetic field than in zero field conditions. This effect is driven by a field-induced reorientation of magnetic order. The oscillator strength lost in the color band is partially transferred to the magnon side band, a process that also reveals a new exciton pattern induced by the modified exchange coupling. Analysis of the exciton pattern exposes C2/c monoclinic symmetry in the high field phase of hematite. Taken together, these findings advance our understanding of iron-based materials under extreme conditions. [4pt] Collaborators include: X. S. Xu, P. Chen, Q. -C. Sun, T. V. Brinzari (Tennessee); S. McGill (NHMFL); J. De Groot, M. Angst, R. P. Hermann (Julich); A. D. Christianson, B. C. Sales, D. Mandrus (ORNL); A. P. Litvinchuk (Houston); J. -W. Kim (Ames); Z. Islam (Argonne); N. Lee, S. -W. Cheong

  2. 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.

  3. Lunar surface: composition inferred from optical properties.

    PubMed

    Hapke, B

    1968-01-01

    The optical characteristics (intensity, polarization, spectrum, and albedo) of the moon surface are compared with those of rock and meteorite powders. The only materials whose optical properties match those of the lunar surface are basic rocks containing lattice iron but little or no free iron, and then only after irradiation of these rocks by a simulated solar wind. Optical properties of chondritic meteorite powders differ from those of the moon in significant respects. The lunar crust is probably not chondritic, but is similar in composition to terrestrial iron-rich basalts. These results are independent of those from the Surveyor V alpha-scattering experiment and, in addition, provide a basis for extrapolating the Surveyor V analysis to other areas of the moon. The Surveyor V experiment has thus confirmed the value of earth-based optical techniques for the study of the structure and composition of the surfaces of other planets.

  4. 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.

  5. 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

  6. Optical properties of electrochromic vanadium pentoxide

    SciTech Connect

    Cogan, S. F.; Nguyen, N. M.; Perrotti, S. J.; Rauh, R. D.

    1989-08-01

    Electrochemical and spectroscopic measurements were used to characterize the electrochromic behavior of sputtered V/sub 2/O/sub 5/ films. In response to lithium intercalation, the fundamental optical absorption edge of V/sub 2/O/sub 5/ shifts to high energies by 0.20--0.31 eV as the lithium concentration increases from Li/sub 0.0/V/sub 2/O/sub 5/ to Li/sub 0.86/V/sub 2/O/sub 5/. There is a corresponding increase in the near-infrared absorption that exhibits Beer's law behavior at low lithium concentrations. The shift in absorption edge results in a large decrease in absorbance in the 350--450 nm wavelength range. This effect is most prevalent in thin films which exhibit a yellow to colorless optical modulation on lithium intercalation. The cathodic coloration in the near infrared is relatively weak with a maximum coloration efficiency of 35 cm/sup 2//C.

  7. Influence from relative size and absorption contrast of inhomogeneity on NIR diffuse optical image reconstruction

    NASA Astrophysics Data System (ADS)

    Zhao, Huijuan; Gao, Feng; Tanikawa, Yukari; Homma, Kazuhiro; Yamada, Yukio

    2005-04-01

    Near infrared (NIR) diffused optical tomography (DOT) is emerging as a potential tool of non-invasively diagnosing woman breast cancers, neonatal brain hypoxia, and other human organ diseases. The intensive and worldwide investigations in theory and experiment have revealed the possibility of NIR DOT in providing both anatomical and functional information of biological tissue simultaneously, which is important for distinguishing between healthy and diseased tissues, such as benign and malignant tumors. In this paper, our recent DOT experiments on human lower legs and forearms are presented using our time-resolved measuring system and image reconstruction algorithm based on the modified generalized pulse spectrum technique. It was found that the image quality in the experiments, including both the spatial resolution and the quantitativeness of the targets, was rather poor, and the interior blood vessels undisclosed in the absorption images. To clarify this issue, the influences of target contrast and size on the image reconstruction were investigated with simulated data. We have accordingly obtained the following observations: the quantitativeness of the reconstructed optical properties was prone to be spoiled by the small size ratio and high contrast of the interior targets (such as blood vessels) to the background, and the incompleteness of information embedded in the featured data-types, in addition to the experimental noise, evidently answers for the degradation of the spatial resolution and quantitativeness. It was shown in a further simulative investigation that the image quality could be substantially improved by making full use of the time-resolved data.

  8. Changes in optical properties of rat skin during thermal coagulation

    NASA Astrophysics Data System (ADS)

    Thomsen, Sharon L.; Vijverberg, Helene; Huang, Robert; Schwartz, Jon A.

    1993-07-01

    Thermal coagulation of albino rat skin heated in vitro results in prominent changes of light scattering but relatively little in light absorption based on measurements using an integrating sphere spectrometer. The reduced scattering coefficients, (mu) s(1-g), gradually increase as temperatures increase from room temperature to 55 degree(s)C then rapidly decrease to plateau after 70 degree(s)C is reached. The differences among the (mu) s(1-g) values for the different wavelengths were greater at the lower temperatures than at higher temperatures. The absorption coefficient, (mu) a, changed very little over the test temperature range (room temperature to 90 degree(s)C) and then only at higher temperatures and for longer wavelengths. The optical property changes were associated with thermally induced light microscopic and ultrastructural changes in the dermal collagen, a major tissue component of skin.

  9. 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.

  10. Round-robin test on optical absorption at 10.6 μm

    NASA Astrophysics Data System (ADS)

    Ristau, Detlev; Niederwald, Hansjoerg S.; Erdelyi, D.; Meja, Peter; Giesen, Adolf; Plass, Wilfried; Krupka, Rene; Kennedy, Michael; Oertel, E.; Lu, Zhiming; Le, T. V.; Lee, Kwang M.; Reedy, Herman E.; Scatena, D.; Ellis, Nick; Greening, David

    1996-05-01

    The approved Draft International Standard 11551 on test methods for absorptance of optical laser components recently passed the international voting procedure. The utility of this standard practice document is the subject of the present round robin test. In order to cover a broad range of CO2-laser optical components, different types of metal mirrors and transmissive ZnSe-optics were included in the master sample set. After an initial inspection, this set passed through a series of optical laboratories in the United States, the United Kingdom, and Germany. The absorption of the samples was measured by calorimetric methods according to ISO DIS 11551, and the measurement results were compiled by the coordinating institute. The evaluation of the experiment was not started until all tests were completed. The results of the round robin test are discussed, compared and evaluated with respect to ageing mechanisms in optical coatings for CO2-laser systems. Although a great variety of different test facilities was employed by the round robin partners, a good agrement of the absorption values was observed for the wavelength of 10.6 micrometers . This demonstrates the versatility of the approved Draft International Standard 11551 for the calorimetric measurement of optical absorption in CO2-laser components.

  11. MEASUREMENTS OF BLACK CARBON PARTICLES CHEMICAL, PHYSICAL, AND OPTICAL PROPERTIES

    SciTech Connect

    Onasch, T.B.; Sedlacek, A.; Cross, E. S.; Davidovits, P.; Worsnop, D. R.; Ahern, A.; Lack, D. A.; Cappa, C. D.; Trimborn, A.; Freedman, A.; Olfert, J. S.; Jayne, J. T.; Massoli, P.; Williams, L. R.; Mazzoleni, C.; Schwarz, J. P.; Thornhill, D. A.; Slowik, J. G.; Kok, G. L.; Brem, B. T.; Subramanian, R.; Spackman, J. R.; Freitag, S.; and Dubey, M. K.

    2009-12-14

    Accurate measurements of the chemical, physical, and optical properties of aerosol particles containing black carbon are necessary to improve current estimates of the radiative forcing in the atmosphere. A collaborative research effort between Aerodyne Research, Inc. and Boston College has focused on conducting field and laboratory experiments on carbonaceous particles and the development and characterization of new particulate instrumentation. This presentation will focus on the chemical, physical, and optical properties of black carbon particles measured in the laboratory in order to understand the effects of atmospheric processing on black carbon particles. Results from a three-week study during July 2008 of mass- and optical-based black carbon measurements will be presented. The project utilized the Boston College laboratory flame apparatus and aerosol conditioning and characterization equipment. A pre-mixed flat flame burner operating at controlled fuel-to-air ratios produced stable and reproducible concentrations of soot particles with known sizes, morphologies, and chemical compositions. In addition, other black carbon particle types, including fullerene soot, glassy carbon spheres, oxidized flame soot, Regal black, and Aquadag, were also atomized, size selected, and sampled. The study covered an experimental matrix that systematically selected particle mobility size (30 to 300 nm) and black carbon particle mass, particle number concentration, particle shape (dynamic shape factor and fractal dimension), and particle chemistry and density (changed via coatings). Particles were coated with a measured thickness (few nm to {approx}150 nm) of sulfuric acid or bis (2-ethylhexyl) sebacate and passed through a thermal denuder to remove the coatings. Highlights of the study to be presented include: (1) Characterization of the chemical and physical properties of various types of black carbon particles, (2) Mass specific absorption measurements as a function of fuel

  12. Sunlight absorption engineering for thermophotovoltaics: contributions from the optical design.

    PubMed

    Míguez, Hernán

    2015-03-01

    Nowadays, solar thermophotovoltaic systems constitute a platform in which sophisticated optical material designs are put into practice with the aim of achieving the long sought after dream of developing an efficient energy conversion device based on this concept. Recent advances demonstrate that higher efficiencies are at reach using photonic nanostructures amenable to mass production and scale-up. PMID:25677828

  13. Sunlight absorption engineering for thermophotovoltaics: contributions from the optical design.

    PubMed

    Míguez, Hernán

    2015-03-01

    Nowadays, solar thermophotovoltaic systems constitute a platform in which sophisticated optical material designs are put into practice with the aim of achieving the long sought after dream of developing an efficient energy conversion device based on this concept. Recent advances demonstrate that higher efficiencies are at reach using photonic nanostructures amenable to mass production and scale-up.

  14. Electronic and optical properties of novel carbon allotropes

    DOE PAGES

    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

  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

    NASA Astrophysics Data System (ADS)

    Olendski, O.; Barakat, T.

    2014-02-01

    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. Magnetic field control of the optical absorption in two-dimensional semiconductor rings

    NASA Astrophysics Data System (ADS)

    Olendski, Oleg; Barakat, Thabit

    2014-03-01

    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 m 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 allow 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. Authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding this work through research group no RGP-VPP-217.

  18. A tunable fiber-coupled optical cavity for agile enhancement of detector absorption

    NASA Astrophysics Data System (ADS)

    Heath, Robert M.; Tanner, Michael G.; Kirkwood, Robert A.; Miki, Shigehito; Warburton, Richard J.; Hadfield, Robert H.

    2016-09-01

    Maximizing photon absorption into thin active structures can be the limiting factor for photodetector efficiency. In this work, a fiber-coupled tunable cavity is demonstrated, designed to achieve close to unity absorption of photons into a thin film superconducting nanowire single photon detector (SNSPD). A technique for defining a stable cavity between the end of a telecommunications optical fiber and a reflective substrate is described and realized. Cavity resonances are demonstrated both through the tuning of input wavelength and cavity length. The resulting optical cavity can tune the resonant absorption in situ over a wavelength range of 100 nm. This technique is used to maximize the single photon absorption into both a back-side-coupled Au mirror SNSPD and a front-side-coupled distributed Bragg reflector cavity SNSPD. The system detection efficiency (SDE) is limited by imperfections in the thin films, but in both cases we demonstrate an improvement of the SDE by 40% over bare fiber illumination.

  19. 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.

  20. Microscopic optical model calculations of 4He, 12C-nucleus absorption cross sections

    NASA Technical Reports Server (NTRS)

    Dubey, R. R.; Khandelwal, G. S.; Cucinotta, F. A.; Wilson, J. W.

    1996-01-01

    Calculations of absorption cross sections using a microscopic first-order optical potential for heavy-ion scattering are compared with experiments. In-medium nucleon-nucleon (NN) cross sections were used to calculate the two-body scattering amplitude. A medium-modified first-order optical potential was obtained for heavy-ion scattering using the in-medium two-body scattering amplitude. A partial wave expansion of the Lippmann-Schwinger equation in momentum space was used to calculate the absorption cross sections for various systems. The results are presented for the absorption cross sections for 4He-nucleus and 12C-nucleus scattering systems and are compared with the experimental values in the energy range 18-83A MeV. The use of the in-medium NN cross sections is found to result in significant reduction of the free space absorption cross sections in agreement with experiment.

  1. Photothermal absorption measurements for improved thermal stability of high-power laser optics

    NASA Astrophysics Data System (ADS)

    Stubenvoll, M.; Schäfer, B.; Mann, K.; Walter, A.; Zittel, L.

    2013-11-01

    An absorption measurement system was set up deploying a Hartmann-Shack wavefront sensor with extreme sensitivity to accomplish spatially resolved monitoring of thermally induced wavefront distortions. Photothermal absorption measurements in the near-infrared range were performed for both the characterization of optical materials and complete F-Theta lenses, utilizing a 500 W Yb fiber laser (λ = 1070 nm) to induce thermal load. Different combinations of bulk materials and AR coatings were examined to minimize absorption and to evaluate potential approaches for thermal compensation. Additionally, bulk and surface / coating absorption coefficients were determined by means of curve-fitting procedures. Furthermore, F-Theta lenses were tested to gain understanding of the thermal behavior of the entire optical system.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. [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

  8. 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.

  9. Growth of High Quality AlN Single Crystals and Their Optical Properties

    NASA Astrophysics Data System (ADS)

    Strassburg, M.; Senawiratne, J.; Dietz, N.; Haboeck, U.; Hoffmann, A.; Noveski, V.; Dalmau, R.; Schlesser, R.; Sitar, Z.

    2005-06-01

    Growth and optical properties of high quality AlN single crystals grown by physical vapor transport using powder sublimation is presented. Crystallinity, incorporated impurities and their effects on the optical properties are evaluated for different crucible materials and growth environments. A significant reduction of impurity incorporation was achieved using a two-step growth process in a TaN crucible. Crystal defects and the effect of incorporated impurities on the optical properties have been analyzed by their characteristic photoluminescence and absorption, Raman- and glow discharge mass spectroscopy.

  10. Strong mid-infrared optical absorption by supersaturated sulfur doping in silicon

    NASA Astrophysics Data System (ADS)

    Umezu, I.; Kohno, A.; Warrender, J. M.; Takatori, Y.; Hirao, Y.; Nakagawa, S.; Sugimura, A.; Charnvanichborikarn, S.; Williams, J. S.; Aziz, M. J.

    2011-12-01

    Single crystalline silicon supersaturated with sulfur was prepared by ion implantation followed by pulsed laser melting and rapid solidification. A strong and broad optical absorption band and free-carrier absorption appeared for this sample around 0.5 eV and below 0.2 eV, respectively. A possible candidate for the origin of the 0.5 eV band is the formation of an impurity band by supersaturated doping.

  11. 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.

  12. Development of Fourier transform spectrometry for UV-visible differential optical absorption spectroscopy measurements of tropospheric minor constituents.

    PubMed

    Vandaele, A C; Carleer, M

    1999-04-20

    Concentration measurements of trace gases in the atmosphere require the use of highly sensitive and precise techniques. The UV-visible differential optical absorption spectroscopy technique is one that is heavily used for tropospheric measurements. To assess the advantages and drawbacks of using a Fourier transform spectrometer, we built a differential optical absorption spectroscopy optical setup based on a Bruker IFS 120M spectrometer. The characteristics and the capabilities of this setup have been studied and compared with those of the more conventional grating-based instruments. Two of the main advantages of the Fourier transform spectrometer are (1) the existence of a reproducible and precise wave-number scale, which greatly simplifies the algorithms used to analyze the atmospheric spectra, and (2) the possibility of recording large spectral regions at relatively high resolution, enabling the simultaneous detection of numerous chemical species with better discriminating properties. The main drawback, on the other hand, is due to the fact that a Fourier transform spectrometer is a scanning device for which the scanning time is small compared with the total measurement time. It does not have the signal integration capabilities of the CCD or photodiode array-based grating spectrographs. The Fourier transform spectrometer therefore needs fairly large amounts of light and is limited to short to medium absorption path lengths when working in the UV.

  13. A method for determination of the absorption and scattering properties interstitially in turbid media

    NASA Astrophysics Data System (ADS)

    Dimofte, Andreea; Finlay, Jarod C.; Zhu, Timothy C.

    2005-05-01

    We have developed a method to quickly determine tissue optical properties (absorption coefficient μa and transport scattering coefficient μ'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 μa and μ'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% (μ'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% (μa = 0.1-1 cm-1). For comparison, the optical properties of each phantom are determined independently using broad-beam illumination. We find that μa and μ's can be determined by this method with a standard (maximum) deviation of 8% (15%) and 18% (32%) for μa and μ'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 μa is large (μa > 1 cm-1). We presented in vivo data measured in human prostate using this method.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. [Novel analysis algorithms for differential optical absorption spectroscopy for pollution monitoring].

    PubMed

    Zhang, Xue-Dian; Huang, Xian; Xu, Ke-Xin

    2007-11-01

    Differential optical absorption spectroscopy, or DOAS, is a widely used method to determine concentrations of atmospheric species. The principle of DOAS for measuring the concentration of air pollutants is presented in briefly. Using the linear relationship between the area of the measured differential absorbance curve and that of the differential absorption cross-section curve as taken from the literature, an alternative method for calculating the gas concentration on the basis of the proportionality between differential absorbance and differential absorption cross section of the gas under study was developed. The method can be used on its own for single-component analysis or as a complement to the standard technique in multi-component cases. The procedure can be used with differential absorption cross sections measured in the laboratory or taken from the literature. In addition, the method provides a criterion to discriminate between different species having absorption features in the same wavelength range.

  2. Optical absorption issues in CdGeAs2 single crystals

    NASA Astrophysics Data System (ADS)

    Nagashio, K.; Bai, Lihua; DeMattei, R.; Giles, N. C.; Feigelson, R. S.

    2005-08-01

    Cadmium germanium diarsenide (CdGeAs2,) crystals are very promising for infrared second harmonic generation. However, their use has been limited by optical absorption in the 5 pm region. The role of composition and dopants has been extensively studied, and some point defects have been identified which do affect transparency. While some low absorption material has been produced, it has not been reproducible and variations within boules have been a serious problem. In this paper, which reviews some recent work on this problem, we describe a surprising and complex correlation between optical transparency, dislocations and point defects.

  3. Absorption spectra and optical parameters of lithium-potassium sulphate single crystals

    NASA Astrophysics Data System (ADS)

    El-Fadl, A. Abu; Gaffar, M. A.; Omar, M. H.

    1999-09-01

    The optical transmittance and reflectance near the fundamental absorption region along the c- and a-axes of lithium potassium sulphate single crystal (LKS) are measured at room temperature. From the data the absorption coefficient ( α) and the optical band gap ( Eopt.g) were deduced. The type of transition was determined. The steepness parameter ( σ), the temperature dependence of the energy gap and the exciton energy ( E0) were also calculated. The extinction coefficient, the refractive index and both the real and imaginary parts of the dielectric permittivity were calculated as functions of the photon energy.

  4. 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.

  5. 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

  6. 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.

  7. Quasiparticle band structures and optical properties of magnesium fluoride

    NASA Astrophysics Data System (ADS)

    Yi, Zhijun; Jia, Ran

    2012-02-01

    The quasiparticle and optical properties of magnesium fluoride (MgF2) are computed within the GW approximation based on many-body perturbation theory (MBPT). The many-body effects appearing in self-energy and electron-hole interactions have an important influence on the electronic and optical properties. The DFT-LDA calculation shows a 6.78 eV band gap. Two methods are employed to evaluate the self-energy within the GW approximation in the present work. The generalized plasmon pole model (GPP) provides a band gap of 12.17 eV, which agrees well with the experimental value of 12.4 eV (Thomas et al 1973 Phys. Status Solidi b 56 163). Another band gap value of 11.30 eV is obtained by using a full frequency-dependent self-energy, which is also not far from the experimental value and is much better than the result from the LDA calculation. The calculated optical spectrum within DFT is significantly different from the experiment. Although the calculated optical absorption threshold within the GW method is close to the experiment, the overall shape of the spectrum is still similar to the case of DFT. However, the overall shape of the spectrum via the Bethe-Salpeter equation (BSE) method agrees well with the experiment.

  8. Quasiparticle band structures and optical properties of magnesium fluoride.

    PubMed

    Yi, Zhijun; Jia, Ran

    2012-02-29

    The quasiparticle and optical properties of magnesium fluoride (MgF(2)) are computed within the GW approximation based on many-body perturbation theory (MBPT). The many-body effects appearing in self-energy and electron-hole interactions have an important influence on the electronic and optical properties. The DFT-LDA calculation shows a 6.78 eV band gap. Two methods are employed to evaluate the self-energy within the GW approximation in the present work. The generalized plasmon pole model (GPP) provides a band gap of 12.17 eV, which agrees well with the experimental value of 12.4 eV (Thomas et al 1973 Phys. Status Solidi b 56 163). Another band gap value of 11.30 eV is obtained by using a full frequency-dependent self-energy, which is also not far from the experimental value and is much better than the result from the LDA calculation. The calculated optical spectrum within DFT is significantly different from the experiment. Although the calculated optical absorption threshold within the GW method is close to the experiment, the overall shape of the spectrum is still similar to the case of DFT. However, the overall shape of the spectrum via the Bethe-Salpeter equation (BSE) method agrees well with the experiment.

  9. Effects of sample preparation on the optical properties of breast tissue

    NASA Astrophysics Data System (ADS)

    Marks, Fay A.

    1996-04-01

    The optical properties of biological tissue should be determined in vivo whenever possible. However, for those instances when in vivo studies are impractical, too expensive or inappropriate, and when blood flow is not an issue, the ability to perform in vitro studies then becomes invaluable. Optical absorption spectroscopy shows that it may be possible to obtain meaningful information about the optical properties of human breast tissue from in vitro samples if strict preparation and measuring protocols are used. That a strict protocol for storing and handling tissue is critical can be seen from our observations of changes in the optical absorption spectra that occur in response to formalin fixation, the passage of time, application of stains and dyes, and storage in growth medium of the excised tissue. In vivo optical absorption spectroscopy measurements have been made on human breast cancer xenografts and compared with in vitro measurements on breast biopsies prepared according to precise collection and treatment protocols. There is a 'window of opportunity' before time dependent changes in the UV optical absorption spectra of the excised tissue specimens occur. This time window of opportunity widens at longer wavelengths with the least changes occurring in the optical spectra in the NIR.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Intraband optical absorption in a single quantum ring: Hydrostatic pressure and intense laser field effects

    NASA Astrophysics Data System (ADS)

    Barseghyan, M. G.

    2016-11-01

    The intraband optical absorption in GaAs/Ga0.7Al0.3As two-dimensional single quantum ring is investigated. Considering the combined effects of hydrostatic pressure and intense laser field the energy of the ground and few excited states has been found using the effective mass approximation and exact diagonalization technique. The energies of these states and the corresponding threshold energy of the intraband optical transitions are examined as a function of hydrostatic pressure for the different values of the laser field parameter. We also investigated the dependencies of the intraband optical absorption coefficient as a function of incident photon energy for different values of hydrostatic pressure and laser field parameter. It is found that the effects of hydrostatic pressure and intense laser field lead to redshift and blueshift of the intraband optical spectrum respectively.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Nonlinear absorption, optical limiting behavior and structural study of a new chalcone derivative-1-(3, 4-dimethylphenyl)-3-[4(methylsulfanyl) phenyl] prop-2-en-1-one

    NASA Astrophysics Data System (ADS)

    Chandra Shekhara Shetty, T.; Raghavendra, S.; Chidan Kumar, C. S.; Dharmaprakash, S. M.

    2016-03-01

    A new third order nonlinear optical (NLO) organic material-1-(3, 4-dimethylphenyl)-3-[4(methylsulfanyl) phenyl] prop-2-en-1-one (4DPMS) belonging to chalcone family has been crystallized in acetone solution. The 4DPMS crystals are characterized by CHNS analysis, FTIR, UV-visible spectral and thermal techniques. The single crystal X-ray diffraction study reveals that 4DPMS crystallizes in monoclinic system with P21/n space group. The linear optical absorption spectrum revealed that the 4DPMS crystals are transparent in the entire visible region. Thermogravimetric data shows absence of phase transition before melting point and from differential scanning calorimetry analysis the melting point of the crystal is found to be 106 °C. Third order nonlinear absorption and optical limiting experiment on 4DPMS was carried out using open aperture Z-scan technique with Nd: YAG laser operating at 532 nm. It was found that the calculated values of excited state absorption cross section for 4DPMS molecules is much greater than the ground state absorption cross section. A decrease in effective nonlinear absorption coefficient was observed with increase in the input irradiance of laser. The observed optical limiting property in 4DPMS is attributed to reverse saturable absorption.

  20. Optical and dielectric properties of nanocomposites systems based on epoxy resins and reactive polyhedral oligosilsquioxanes

    NASA Astrophysics Data System (ADS)

    Eed, H.; Hassouneh, O.; Ramadin, Y.; Zihlif, A.; Ragosta, G.; Elimat, Z. M.

    2013-01-01

    An epoxy network structure made of diglycidylether of bisphenol-A and diamino diphenylsulfone was modified by adding various amounts of an epoxy functionalized polyhedral oligomeric silsesquioxane. The obtained nanocomposites were characterized in terms of optical and dielectric properties. The UV-absorption spectra were collected in the wavelength range of 400-800 nm. The optical data were analyzed in terms of absorption formula for non-crystalline materials. The optical energy gap and other basic constants, such as energy tails, dielectric constants, refractive index and optical conductivity, were determined and showed a clear dependence on the POSS concentration. It was found that the optical energy gap for the neat epoxy resin is less than for nanocomposites, and it decreases with increase in the POSS content. The refractive index of nanocomposites was determined from the calculated values of absorption and reflectance. It was found that the refractive index and the dielectric constants increased with increase in the POSS concentration. The optical conductivity, which is a measure of the optical absorption, increased with the POSS content. Furthermore, it was found that the glass transition temperature and the optical energy gap correlate well with the POSS filler concentration.

  1. Characterization of Aerogel's Optical Properties

    NASA Astrophysics Data System (ADS)

    Justen, Abigail; Young, Jonathan

    2013-10-01

    Aerogel is used in the kaon aerogel Cerenkov detector at Jefferson Lab. Kaons are identified by the number of photons created through Cerenkov radiation emitted as the kaon travels through the aerogel. Depending on the refractive index of the aerogel, kaons of different momenta can be detected and distinguished from protons. Therefore, a uniform refractive index in the detector is important to reduce uncertainty in the Cerenkov radiation. We found the refractive index of the aerogel by shining a red construction laser through it and measuring how far the beam refracted. The refractive index of aerogel is also directly related to the density of aerogel. The humidity in the air, if absorbed, could also affect the refractive index. To test the effect of humidity on aerogel we used a humidity controlled environment between 80 and 100 percent on aerogel from Matsushita Electric Works, Ltd, Japan Fine Ceramic Center, and Novosibirsk. Finally, we tested the transmittance of aerogel tiles with a UV/Vis photospectrometer to find the correlation between transmittance and the tile's properties. Tiles with the highest transmittance will allow for the most accurate count of the photons produced through Cerenkov radiation. The results from these experiments will be presented. Supported in Part by NSF Grant 1019521 and 1039446.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. Structures, optical absorption and electrical properties of pulsed-laser-deposited CuIn0.8Ga0.2Se2 thin films and their use in CIGS/PCBM photovoltaic structures

    NASA Astrophysics Data System (ADS)

    Zhao, Yu; Wu, JiaDa; Xu, Ning

    2016-10-01

    Polycrystalline CuIn0.8Ga0.2Se2 (CIGS) thin films are deposited on ITO-glass substrates at different substrate temperatures by pulsed laser deposition using a Nd:YAG laser. The crystallinity of the as-deposited CIGS films significantly improved as the substrate temperature increased. The experimental results indicate that the ordered defect compound model is also applicable to the CIGS films deposited in these experiments. All the as-deposited CIGS thin films show absorption coefficients of 105 cm‑1 magnitude in a wavelength range of 400–900 nm. The CIGS thin films deposited at substrate temperatures lower than 400 °C exhibit n-type conductivity while those deposited at a substrate temperature of 500 °C display p-type conductivity. The CIGS/phenyl-C61-butyric acid methyl ester (PCBM) photovoltaic structure, with a CIGS layer as the only absorber, demonstrates an apparent photovoltaic response with a short circuit current density of 0.389 mA cm‑2 and an open circuit voltage of 0.327 V.

  9. Sensitive photothermal deflection technique for measuring absorption in optically thin media

    SciTech Connect

    Boccara, A. C.; Jackson, Warren; Amer, Nabil M.; Fournier, D.

    1980-01-01

    We present a highly sensitive and simple photothermal scheme for determining optical absorptions in condensed matter samples. {alpha}l values as low as 10{sup -7} and 10{sup -8} were measured for thin films and coatings and for liquids, respectively. A comparison with thermal lens effect is given, and the experimental factors limiting our sensitivity are discussed.

  10. Influence of refractive index and solar concentration on optical power absorption in slabs

    NASA Technical Reports Server (NTRS)

    Williams, M. D.

    1988-01-01

    The optical power absorbed by a slab at the focus of a parabolic dish concentrator is calculated. The calculations are plotted versus maximum angle of incidence of irradiation (which corresponds to solar concentration) with absorption coefficient as a parameter for several different indices of refraction that represent real materials.

  11. 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

  12. 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.

  13. Optical characterization of the nematic lyotropic chromonic liquid crystals: light absorption, birefringence, and scalar order parameter.

    PubMed

    Nastishin, Yu A; Liu, H; Schneider, T; Nazarenko, V; Vasyuta, R; Shiyanovskii, S V; Lavrentovich, O D

    2005-10-01

    We report on the optical properties of the nematic (N) phase formed by lyotropic chromonic liquid crystals (LCLCs) in well aligned planar samples. LCLCs belong to a broad class of materials formed by one-dimensional molecular self-assembly and are similar to other systems such as "living polymers" and "wormlike micelles." We study three water soluble LCLC forming materials: disodium chromoglycate, a derivative of indanthrone called Blue 27, and a derivative of perylene called Violet 20. The individual molecules have a planklike shape and assemble into rodlike aggregates that form the phase once the concentration exceeds about 0.1 M. The uniform surface alignment of the N phase is achieved by buffed polyimide layers. According to the light absorption anisotropy data, the molecular planes are on average perpendicular to the aggregate axes and thus to the nematic director. We determined the birefringence of these materials in the N and biphasic N-isotropic (I) regions and found it to be negative and significantly lower in the absolute value as compared to the birefringence of typical thermotropic low-molecular-weight nematic materials. In the absorbing materials Blue 27 and Violet 20, the wavelength dependence of birefringence is nonmonotonic because of the effect of anomalous dispersion near the absorption bands. We describe positive and negative tactoids formed as the nuclei of the new phase in the biphasic N-I region (which is wide in all three materials studied). Finally, we determined the scalar order parameter of the phase of Blue 27 and found it to be relatively high, in the range 0.72-0.79, which puts the finding into the domain of general validity of the Onsager model. However, the observed temperature dependence of the scalar order parameter points to the importance of factors not accounted for in the athermal Onsager model, such as interaggregate interactions and the temperature dependence of the aggregate length.

  14. Optical Properties of Single-Crystal Sapphire Fibers

    NASA Astrophysics Data System (ADS)

    Merberg, Glenn N.

    1992-01-01

    The optical properties of edge-defined, film-fed growth (EFG) and laser heated pedestal growth (LHPG) sapphire fibers were characterized, and the utility of these fibers for medical and industrial applications assessed. While EFG fibers are not yet produced with good optical quality, they offer enormous potential for mass production of sapphire fibers. The LHPG process has been successfully employed to produce good optical quality sapphire. This dissertation focussed on the optical attenuation mechanisms which limit the transmission properties of both EFG and LHPG sapphire fibers. The EFG fibers obtained for this research were found to contain bubbles along the fiber axes. As a result of the bubble inclusions, the measured optical scattering coefficients of the fibers were quite high. At a wavelength of 2.94 mum, a typical 280 μm diameter EFG fiber had a total attenuation coefficient of 18 dB/m. The contribution of scattering to this loss was measured as 17 dB/m, and the absorptive component as measured by laser calorimetry was 1 dB/m. The wavelength dependence of the scattering in EFG fibers was found to be lambda^{-1.5}, which is consistent with a Mie scattering model for scattering of light by bubbles on the dimensional order of the wavelength. Some of the LHPG fibers grown at Rutgers had measured attenuation coefficients of less than 2 dB/m at 2.94 μm wavelength. The absorptive component of this loss was measured by laser calorimetry as 0.7 dB/m, while the scattering loss was 1 dB/m. Optical scattering in Rutgers LHPG fibers had a lambda^ {-4} wavelength dependence, although the scattering coefficients were considerably higher than predicted for intrinsic scattering. Although visible absorbing color -centers were discovered in Rutgers LHPG fibers, excessive optical scattering dominated the attenuation in this spectral region. Melt extruded Teflon-FEP claddings were applied to LHPG fibers. The claddings were very effective in reducing evanescent coupling of Er

  15. Theory of edge-state optical absorption in two-dimensional transition metal dichalcogenide flakes

    NASA Astrophysics Data System (ADS)

    Trushin, Maxim; Kelleher, Edmund J. R.; Hasan, Tawfique

    2016-10-01

    We develop an analytical model to describe sub-band-gap optical absorption in two-dimensional semiconducting transition metal dichalcogenide (s-TMD) nanoflakes. The material system represents an array of few-layer molybdenum disulfide crystals, randomly orientated in a polymer matrix. We propose that optical absorption involves direct transitions between electronic edge states and bulk bands, depends strongly on the carrier population, and is saturable with sufficient fluence. For excitation energies above half the band gap, the excess energy is absorbed by the edge-state electrons, elevating their effective temperature. Our analytical expressions for the linear and nonlinear absorption could prove useful tools in the design of practical photonic devices based on s-TMDs.

  16. Optical pumping effect in absorption imaging of F =1 atomic gases

    NASA Astrophysics Data System (ADS)

    Kim, Sooshin; Seo, Sang Won; Noh, Heung-Ryoul; Shin, Y.

    2016-08-01

    We report our study of the optical pumping effect in absorption imaging of 23Na atoms in the F =1 hyperfine spin states. Solving a set of rate equations for the spin populations in the presence of a probe beam, we obtain an analytic expression for the optical signal of the F =1 absorption imaging. Furthermore, we verify the result by measuring the absorption spectra of 23Na Bose-Einstein condensates prepared in various spin states with different probe-beam pulse durations. The analytic result can be used in the quantitative analysis of F =1 spinor condensate imaging and readily applied to other alkali-metal atoms with I =3 /2 nuclear spin such as 87Rb.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Determination of optical property changes by laser treatments using inverse adding-doubling method

    NASA Astrophysics Data System (ADS)

    Honda, Norihiro; Ishii, Katsunori; Kimura, Akinori; Sakai, Makoto; Awazu, Kunio

    2009-02-01

    It is widely recognized for the realization of the pre-estimated treatment effects that the knowledge about the optical properties of the target tissues used to understanding the prediction of propagation and distribution of light within tissues would suffer from the technical problem such as the kinetic changes of the optical properties in laser irradiation. In this study, the optical properties of normal and laser coagulated chicken breast tissues and porcine intervertebral disks, normal and laser ablation have been determined in vitro in the spectral range between 350 and 1000 nm. In addition, the optical properties of the normal and photodynamic therapy (PDT) treated tumor, Lewis lung carcinoma, tissues have been determined. Diffuse reflectance and total transmittance of the samples are measured using an integrating-sphere technique. From these experimental data, the absorption coefficients and the reduced scattering coefficients of the samples are determined employing an inverse adding-doubling method. Laser coagulations and ablations have clearly increased the reduced scattering coefficient and slightly reduced the absorption coefficient. PDT treatment has increased absorption and reduced scattering coefficient. It is our expectation that these data will provide fundamental understandings on laser irradiation interactions behavior with tissues. The changes of the optical properties should be accounted for while planning the therapeutic procedure for the realization of safe laser treatments.

  4. 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.

  5. Distinct optical properties of relativistically degenerate matter

    SciTech Connect

    Akbari-Moghanjoughi, M.

    2014-06-15

    In this paper, we use the collisional quantum magnetohydrodynamic (CQMHD) model to derive the transverse dielectric function of a relativistically degenerate electron fluid and investigate various optical parameters, such as the complex refractive index, the reflection and absorption coefficients, the skin-depth and optical conductivity. In this model we take into accounts effects of many parameters such as the atomic-number of the constituent ions, the electron exchange, electron diffraction effect and the electron-ion collisions. Study of the optical parameters in the solid-density, the warm-dense-matter, the big-planetary core, and the compact star number-density regimes reveals that there are distinct differences between optical characteristics of the latter and the former cases due to the fundamental effects of the relativistic degeneracy and other quantum mechanisms. It is found that in the relativistic degeneracy plasma regime, such as found in white-dwarfs and neutron star crusts, matter possess a much sharper and well-defined step-like reflection edge beyond the x-ray electromagnetic spectrum, including some part of gamma-ray frequencies. It is also remarked that the magnetic field intensity only significantly affects the plasma reflectivity in the lower number-density regime, rather than the high density limit. Current investigation confirms the profound effect of relativistic degeneracy on optical characteristics of matter and can provide an important plasma diagnostic tool for studying the physical processes within the wide scope of quantum plasma regimes be it the solid-density, inertial-confined, or astrophysical compact stars.

  6. 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

  7. 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.

  8. 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

  9. Influence of sputtering power on the optical properties of ITO thin films

    SciTech Connect

    K, Aijo John; M, Deepak T, Manju; Kumar, Vineetha V.

    2014-10-15

    Tin doped indium oxide films are widely used in transparent conducting coatings such as flat panel displays, crystal displays and in optical devices such as solar cells and organic light emitting diodes due to the high electrical resistivity and optical transparency in the visible region of solar spectrum. The deposition parameters have a commendable influence on the optical and electrical properties of the thin films. In this study, ITO thin films were prepared by RF magnetron sputtering. The properties of the films prepared under varying sputtering power were compared using UV- visible spectrophotometry. Effect of sputtering power on the energy band gap, absorption coefficient and refractive index are investigated.

  10. Influence of sputtering power on the optical properties of ITO thin films

    NASA Astrophysics Data System (ADS)

    K, Aijo John; Kumar, Vineetha V.; M, Deepak; T, Manju

    2014-10-01

    Tin doped indium oxide films are widely used in transparent conducting coatings such as flat panel displays, crystal displays and in optical devices such as solar cells and organic light emitting diodes due to the high electrical resistivity and optical transparency in the visible region of solar spectrum. The deposition parameters have a commendable influence on the optical and electrical properties of the thin films. In this study, ITO thin films were prepared by RF magnetron sputtering. The properties of the films prepared under varying sputtering power were compared using UV- visible spectrophotometry. Effect of sputtering power on the energy band gap, absorption coefficient and refractive index are investigated.

  11. Improved nonlinear optical and optical limiting properties in non-covalent functionalized reduced graphene oxide/silver nanoparticle (NF-RGO/Ag-NPs) hybrid

    NASA Astrophysics Data System (ADS)

    Sakho, El hadji Mamour; Oluwafemi, Oluwatobi S.; Sreekanth, P.; Philip, Reji; Thomas, Sabu; Kalarikkal, Nandakumar

    2016-08-01

    Nonlinear optical (NLO) response under near infrared (800 nm) and visible (532 nm) laser excitations, of 100 fs (fs) and 5 ns (ns) pulse durations respectively, of reduced graphene oxide (RGO), non-covalent functionalized reduced graphene oxide (NF-RGO) and NF-RGO decorated with various concentration of silver nanoparticles (NF-RGO/Ag-NPs) have been investigated using the Open-aperture Z-Scan technique. For both femtosecond and nanosecond laser excitations, the studied graphene-based materials exhibit good nonlinear optical power limiting properties (OL), with NF-RGO/Ag-NPs sample prepared with 0.1 M AgNO3 showing the best nonlinear optical properties. For the ns regime, the optical limiting threshold decreased from 8.3 J/cm2 in NF-RGO to 4.3 J/cm2 in NF-RGO/Ag-NPs, while at fs regime, the nonlinear absorption coefficient (β) was found to increase with decrease in concentration of Ag-NPs in the hybrid. Two-photon absorption (2 PA) in combination with saturable absorption (SA) in femtosecond regime, and reverse saturable absorption (RSA) along with saturable absorption (SA) in the nanosecond regime, are responsible for the observed nonlinear optical absorption (NLA) behavior in these materials. These findings show that the as-synthesized NF-RGO/Ag-NPs hybrid is a relatively better material for nonlinear optical limiting applications.

  12. All-optical switching in a symmetric three-waveguide coupler with phase-mismatched absorptive central waveguide.

    PubMed

    Chen, Yijing; Ho, Seng-Tiong; Krishnamurthy, Vivek

    2013-12-20

    All-optical switching operation based on manipulation of absorption in a three-waveguide directional coupler is theoretically investigated. The proposed structure consists of one absorptive central waveguide and two identical passive side waveguides. Optically induced absorption change in the central waveguide effectively controls the coupling of light between the two side waveguides, leading to optical switching action. The proposed architecture alleviates the fabrication challenges and waveguide index matching conditions that limit previous demonstrations of similar switching schemes based on a two-waveguide directional coupler. The proposed device accommodates large modal index difference between absorptive and passive waveguides without compromising the switching extinction ratio.

  13. Polarized optical absorption of MnGa2S4 single crystals

    NASA Astrophysics Data System (ADS)

    Niftiev, N. N.; Tagiev, O. B.

    2016-09-01

    Optical absorption of MnGa2S4 single crystals is studied at two light polarizations ( E || C and E⊥ C). The polarization splitting of the absorption edge points to a splitting of the valence band of MnGa2S4. A contribution to the crystal-field splitting is made by two factors, namely, by a difference in the pseudopotential of cationic sublattice atoms and by tetragonal compression of the lattice along the C axis. A scheme of optical transitions in MnGa2S4 in the Brillouin zone center is suggested, according to which the optical transitions D3 + D4 → D1 occur in the polarization E ⊥ C, and the D2 → D1 transitions occur in the polarization E || C.

  14. Many-body effects in the optical absorption of lithium azide (LiN3)

    NASA Astrophysics Data System (ADS)

    Gordienko, A. B.; Filippov, S. I.

    2016-07-01

    Until recently most of the understanding achieved for solid explosives has been obtained using various semi-empirical approaches due to a major role of excitonic effects in the mechanisms of decomposition. Nevertheless, during the last two decades, thanks to the ongoing progress in iterative computational methods, the inclusion of the electron-hole interaction in ab initio calculations has become a standard approach in solid-state theory. In this paper, the electronic structure and optical properties of bulk lithium azide are investigated, taking into account the electron-hole interaction via the Bethe-Salpeter equation (BSE). Here, we employ the kernel polynomial method (KPM), which significantly reduces the computational cost compared to direct diagonalization methods. The calculations of the imaginary part of the polarization dependent dielectric function including excitonic effects are reported for the first time. Then, we show a density map of the two-particle wave function and propose an alternative interpretation of the initial stages of the externally triggered chemical decomposition, based on the analysis of two-particle states near the absorption edge.

  15. Optical properties of X-rays--dynamical diffraction.

    PubMed

    Authier, André

    2012-01-01

    The first attempts at measuring the optical properties of X-rays such as refraction, reflection and diffraction are described. The main ideas forming the basis of Ewald's thesis in 1912 are then summarized. The first extension of Ewald's thesis to the X-ray case is the introduction of the reciprocal lattice. In the next step, the principles of the three versions of the dynamical theory of diffraction, by Darwin, Ewald and Laue, are given. It is shown how the comparison of the dynamical and geometrical theories of diffraction led Darwin to propose his extinction theory. The main optical properties of X-ray wavefields at the Bragg incidence are then reviewed: Pendellösung, shift of the Bragg peak, fine structure of Kossel lines, standing waves, anomalous absorption, paths of wavefields inside the crystal, Borrmann fan and double refraction. Lastly, some of the modern applications of the dynamical theory are briefly outlined: X-ray topography, location of adsorbed atoms at crystal surfaces, optical devices for synchrotron radiation and X-ray interferometry.

  16. Characterization of temperature-dependent optical material properties of polymer powders

    SciTech Connect

    Laumer, Tobias; Stichel, Thomas; Bock, Thomas; Amend, Philipp; Schmidt, Michael

    2015-05-22

    In former works, the optical material properties of different polymer powders used for Laser Beam Melting (LBM) at room temperature have been analyzed. With a measurement setup using two integration spheres, it was shown that the optical material properties of polymer powders differ significantly due to multiple reflections within the powder compared to solid bodies of the same material. Additionally, the absorption behavior of the single particles shows an important influence on the overall optical material properties, especially the reflectance of the powder bed. Now the setup is modified to allow measurements at higher temperatures. Because crystalline areas of semi-crystalline thermoplastics are mainly responsible for the absorption of the laser radiation, the influence of the temperature increase on the overall optical material properties is analyzed. As material, conventional polyamide 12 and polypropylene as new polymer powder material, is used. By comparing results at room temperature and at higher temperatures towards the melting point, the temperature-dependent optical material properties and their influence on the beam-matter interaction during the process are discussed. It is shown that the phase transition during melting leads to significant changes of the optical material properties of the analyzed powders.

  17. Absorptive carbon nanotube electrodes: Consequences of optical interference loss in thin film solar cells

    NASA Astrophysics Data System (ADS)

    Tait, Jeffrey G.; de Volder, Michaël F. L.; Cheyns, David; Heremans, Paul; Rand, Barry P.

    2015-04-01

    A current bottleneck in the thin film photovoltaic field is the fabrication of low cost electrodes. We demonstrate ultrasonically spray coated multiwalled carbon nanotube (CNT) layers as opaque and absorptive metal-free electrodes deposited at low temperatures and free of post-deposition treatment. The electrodes show sheet resistance as low as 3.4 Ω □-1, comparable to evaporated metallic contacts deposited in vacuum. Organic photovoltaic devices were optically simulated, showing comparable photocurrent generation between reflective metal and absorptive CNT electrodes for photoactive layer thickness larger than 600 nm when using archetypal poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl C61-butyric acid methyl ester (PCBM) cells. Fabricated devices clearly show that the absorptive CNT electrodes display comparable performance to solution processed and spray coated Ag nanoparticle devices. Additionally, other candidate absorber materials for thin film photovoltaics were simulated with absorptive contacts, elucidating device design in the absence of optical interference and reflection.A current bottleneck in the thin film photovoltaic field is the fabrication of low cost electrodes. We demonstrate ultrasonically spray coated multiwalled carbon nanotube (CNT) layers as opaque and absorptive metal-free electrodes deposited at low temperatures and free of post-deposition treatment. The electrodes show sheet resistance as low as 3.4 Ω □-1, comparable to evaporated metallic contacts deposited in vacuum. Organic photovoltaic devices were optically simulated, showing comparable photocurrent generation between reflective metal and absorptive CNT electrodes for photoactive layer thickness larger than 600 nm when using archetypal poly(3-hexylthiophene) (P3HT) : (6,6)-phenyl C61-butyric acid methyl ester (PCBM) cells. Fabricated devices clearly show that the absorptive CNT electrodes display comparable performance to solution processed and spray coated Ag nanoparticle

  18. 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.

  19. Modeling optical properties of silicon clusters by first principles: From a few atoms to large nanocrystals

    SciTech Connect

    Nurbawono, Argo; Liu, Shuanglong; Zhang, Chun

    2015-04-21

    Time dependent density functional tight binding (TDDFTB) method is implemented with sparse matrix techniques and improved parallelization algorithms. The method is employed to calculate the optical properties of various Si nanocrystals (NCs). The calculated light absorption spectra of small Si NCs from TDDFTB were found to be comparable with many body perturbation methods utilizing planewave basis sets. For large Si NCs (more than a thousand atoms) that are beyond the reach of conventional approaches, the TDDFTB method is able to produce reasonable results that are consistent with prior experiments. We also employed the method to study the effects of surface chemistry on the optical properties of large Si NCs. We learned that the optical properties of Si NCs can be manipulated with small molecule passivations such as methyl, hydroxyl, amino, and fluorine. In general, the shifts and profiles in the absorption spectra can be tuned with suitably chosen passivants.

  20. Evaluation of a time-resolved stress detection method to determine tissue optical properties

    NASA Astrophysics Data System (ADS)

    Vijverberg, Helene; Thomsen, Sharon L.; Jacques, Steven L.; Oraevsky, Alexander A.

    1995-01-01

    A new method to determine optical properties of biological tissue, time-resolved stress detection (TRSD), was tested on albino rat skin, heated in vitro. The TRSD method is based on the detection of pressure waves that are generated by short laser pulses. The pressure waves carry information about the optical properties (absorption and effective attenuation coefficients) of the medium. The evaluation was done in a systematic way by comparing the results of the TRSD method with results obtained using an integrating sphere. Measurements for both methods were performed on the same skin samples to minimize biological variations. The TRSD method proved to be reasonably successful to determine optical properties of tissue for the used wavelength of 355 nm: (1) The effective attenuation coefficients of both methods agreed very well; (2) The TRSD method gave absorption coefficients of a factor 2 + 0.5 times higher than the integrating sphere method; and (3) The reduced scattering coefficients were sensitive to error.

  1. Performance of a lookup table-based approach for measuring tissue optical properties with diffuse optical spectroscopy

    PubMed Central

    Rajaram, Narasimhan; Tunnell, James W.

    2012-01-01

    Abstract. Diffuse optical spectroscopy (DOS) provides a powerful tool for fast and noninvasive disease diagnosis. The ability to leverage DOS to accurately quantify tissue optical parameters hinges on the model used to estimate light-tissue interaction. We describe the accuracy of a lookup table (LUT)-based inverse model for measuring optical properties under different conditions relevant to biological tissue. The LUT is a matrix of reflectance values acquired experimentally from calibration standards of varying scattering and absorption properties. Because it is based on experimental values, the LUT inherently accounts for system response and probe geometry. We tested our approach in tissue phantoms containing multiple absorbers, different sizes of scatterers, and varying oxygen saturation of hemoglobin. The LUT-based model was able to extract scattering and absorption properties under most conditions with errors of less than 5 percent. We demonstrate the validity of the lookup table over a range of source-detector separations from 0.25 to 1.48 mm. Finally, we describe the rapid fabrication of a lookup table using only six calibration standards. This optimized LUT was able to extract scattering and absorption properties with average RMS errors of 2.5 and 4 percent, respectively. PMID:22612140

  2. Performance of a lookup table-based approach for measuring tissue optical properties with diffuse optical spectroscopy.

    PubMed

    Nichols, Brandon S; Rajaram, Narasimhan; Tunnell, James W

    2012-05-01

    Diffuse optical spectroscopy (DOS) provides a powerful tool for fast and noninvasive disease diagnosis. The ability to leverage DOS to accurately quantify tissue optical parameters hinges on the model used to estimate light-tissue interaction. We describe the accuracy of a lookup table (LUT)-based inverse model for measuring optical properties under different conditions relevant to biological tissue. The LUT is a matrix of reflectance values acquired experimentally from calibration standards of varying scattering and absorption properties. Because it is based on experimental values, the LUT inherently accounts for system response and probe geometry. We tested our approach in tissue phantoms containing multiple absorbers, different sizes of scatterers, and varying oxygen saturation of hemoglobin. The LUT-based model was able to extract scattering and absorption properties under most conditions with errors of less than 5 percent. We demonstrate the validity of the lookup table over a range of source-detector separations from 0.25 to 1.48 mm. Finally, we describe the rapid fabrication of a lookup table using only six calibration standards. This optimized LUT was able to extract scattering and absorption properties with average RMS errors of 2.5 and 4 percent, respectively. PMID:22612140

  3. Structural and Optical Properties of Single Crystalline Bismuth Nanoparticles in Polymer

    NASA Astrophysics Data System (ADS)

    Kabir, Lutful; Mandal, Swapan K.

    We report here the structural and optical properties of Bi nanoparticles in polymer (polypyrrole) matrix. The nanoparticles are synthesized following a wet chemical route. The X-ray diffraction data clearly shows the growth of single crystalline Bi nanoparticles within the host polymer. The microstructure of the Bi nanoparticles obtained by transmission electron microscopy (TEM) reveals clearly the formation of spherical shaped nanoparticles of average size˜27 nm with a narrow size distribution. The optical absorption spectrum exhibits a distinct peak at 278 nm which is attributed to the surface plasmon band of Bi nanoparticles. The absorption spectrum is found to be described well following Mie theory.

  4. Influence of erbium doping on phase transition and optical properties of strontium barium niobate

    NASA Astrophysics Data System (ADS)

    Oprea, Isabella-Ioana; Voelker, Uwe; Niemer, Alexander; Pankrath, Rainer; Podlozhenov, Sergey; Betzler, Klaus

    2009-11-01

    The optical properties of erbium impurities in strontium barium niobate are investigated measuring optical absorption and emission in the visible and near infrared spectral region. For the main fluorescence band at 1.55 μm, an anomalous dependence of the fluorescence decay time on dopant concentration is found which, however, can be consistently explained by reabsorption effects. A Judd-Ofelt analysis of the absorption spectra together with an appropriate analysis of the reabsorption yields a radiative quantum efficiency of approximately 60%. In addition, erbium dopants are shown to efficiently influence the phase transition temperature of strontium barium niobate.

  5. Spectral optical properties of selected photosynthetic microalgae producing biofuels

    NASA Astrophysics Data System (ADS)

    Lee, Euntaek; Heng, Ri-Liang; Pilon, Laurent

    2013-01-01

    This paper presents the spectral complex index of refraction of biofuel producing photosynthetic microalgae between 400 and 750 nm. They were retrieved from their experimentally measured average absorption and scattering cross-sections. The microalgae were treated as homogeneous polydisperse spheres with equivalent diameter such that their surface area was identical to that of their actual spheroidal shape. An inverse method was developed combining Lorentz-Mie theory as the forward method and genetic algorithm. The unicellular green algae Chlamydomonas reinhardtii strain CC125 and its truncated chlorophyll antenna transformants tla1, tlaX, and tla1-CW+ as well as Botryococcus braunii, Chlorella sp., and Chlorococcum littorale were investigated. These species were selected for their ability to produce either hydrogen gas or lipids for liquid fuel production. Their retrieved real and imaginary parts of the complex index of refraction were continuous functions of wavelength with absorption peaks corresponding to those of in vivo Chlorophylls a and b. The T-matrix method was also found to accurately predict the experimental measurements by treating the microalgae as axisymmetric spheroids with the experimentally measured major and minor diameter distributions and the retrieved spectral complex index of refraction. Finally, pigment mass fractions were also estimated from the retrieved absorption index. The method and/or the reported optical properties can be used in various applications from ocean remote sensing, carbon cycle study, as well as photobiological carbon dioxide mitigation and biofuel production.

  6. Spatial variability of absorption coefficients over a biogeochemical gradient in a large and optically complex shallow lake

    NASA Astrophysics Data System (ADS)

    Riddick, Caitlin A. L.; Hunter, Peter D.; Tyler, Andrew N.; Martinez-Vicente, Victor; Horváth, Hajnalka; Kovács, Attila W.; Vörös, Lajos; Preston, Tom; Présing, Mátyás.

    2015-10-01

    In order to improve robustness of remote sensing algorithms for lakes, it is vital to understand the variability of inherent optical properties (IOPs) and their mass-specific representations (SIOPs). In this study, absorption coefficients for particulate and dissolved constituents were measured at 38 stations distributed over a biogeochemical gradient in Lake Balaton, Hungary. There was a large range of phytoplankton absorption (aph(λ)) over blue and red wavelengths (aph(440) = 0.11-4.39 m-1, aph(675) = 0.048-2.52 m-1), while there was less variability in chlorophyll-specific phytoplankton absorption (a*ph(λ)) in the lake (a*ph(440) = 0.022 ± 0.0046 m2 mg-1, a*ph(675) = 0.010 ± 0.0020 m2 mg-1) and adjoining wetland system, Kis-Balaton (a*ph(440) = 0.017 ± 0.0015 m2 mg-1, a*ph(675) = 0.0088 ± 0.0017 m2 mg-1). However, in the UV, a*ph(350) significantly increased with increasing distance from the main inflow (Zala River). This was likely due to variable production of photoprotective pigments (e.g., MAAs) in response to the decreasing gradient of colored dissolved organic matter (CDOM). The slope of CDOM absorption (SCDOM) also increased from west to east due to larger terrestrial CDOM input in the western basins. Absorption by nonalgal particles (aNAP(λ)) was highly influenced by inorganic particulates, as a result of the largely mineral sediments in Balaton. The relative contributions to the absorption budget varied more widely than oceans with a greater contribution from NAP (up to 30%), and wind speed affected the proportion attributed to NAP, phytoplankton, or CDOM. Ultimately, these data provide knowledge of the heterogeneity of (S)IOPs in Lake Balaton, suggesting the full range of variability must be considered for future improvement of analytical algorithms for constituent retrieval in inland waters.

  7. Absorption and Fluorescence Properties of Chromophoric Dissolved Organic Matter Produced by Algae.

    PubMed

    Peng, Tong; Lu, Xiao-lan; Su, Rong-guo; Zhang, Dong-mei

    2015-09-01

    Four kinds of diatom (Chaetoceros curvisetus, Phaeodactylum tricornutum, Nitzschia closterium f. minutissima and Navicula halophile) and two kinds of dinoflagellates (Prorocentrum donghaiense and Gymnodinium) were cultured under laboratory conditions. Variations of optical properties of chromophoric dissolved organic matter (CDOM) were studied with absorption and fluorescence excitation-emission matrix spectroscopy(EEM) during growth of marine microalgae in incubation experiment. Absorption spectrum revealed absorption coefficient a(355) (CDOM absorption coefficients at 355 nm) of 6 kinds of marine microalgae above increased by 64.8%, 242.3%, 535.1%, 903.2%, 836% and 196.4%, respectively. Simultaneously, the absorption spectral slope (Sg), determined between 270 and 350 nm, representing the size of molecular weight of CDOM and humic-like composition, decreased by 8.7%, 34.6%, 39.4%, 53.1%, 46.7%, and 35.7%, respectively. Applying parallel factor analysis (PARAFAC) together with EEM got four components of CDOM: C1(Ex/Em=350(260) nm/450 nm), C2 (Ex/Em=260(430) nm/525 nm), C3 (Ex/Em=325 nm/400 nm) and C4(Ex/Em=275 nm/325 nm), which were relative to three humic-like and one protein-like fluorescent components of Nitzschia closterium f. minutissima and Navicula halophile. In incubation experiment, fluorescence intensity of these four components during growth of Nitzschia closterium f. minutissima increased by, respectively, 8.68, 24.9, 7.19 and 39.8 times, and those of Navicula halophile increased by 2.64, 0.07, 4.39 and 12.4 times, respectively. Significant relationships were found between the fluorescence intensity of four components of CDOM, a(355) and Sg. All results demonstrated that both content and molecular weight of CDOM produced by diatom and dinoflagellate studied in incubation experiment increased, but these two parameters changed more obviously of the diatom than those of dinoflagellate; the proportion of humic-like components in the composition of CDOM

  8. Absorption and Fluorescence Properties of Chromophoric Dissolved Organic Matter Produced by Algae.

    PubMed

    Peng, Tong; Lu, Xiao-lan; Su, Rong-guo; Zhang, Dong-mei

    2015-09-01

    Four kinds of diatom (Chaetoceros curvisetus, Phaeodactylum tricornutum, Nitzschia closterium f. minutissima and Navicula halophile) and two kinds of dinoflagellates (Prorocentrum donghaiense and Gymnodinium) were cultured under laboratory conditions. Variations of optical properties of chromophoric dissolved organic matter (CDOM) were studied with absorption and fluorescence excitation-emission matrix spectroscopy(EEM) during growth of marine microalgae in incubation experiment. Absorption spectrum revealed absorption coefficient a(355) (CDOM absorption coefficients at 355 nm) of 6 kinds of marine microalgae above increased by 64.8%, 242.3%, 535.1%, 903.2%, 836% and 196.4%, respectively. Simultaneously, the absorption spectral slope (Sg), determined between 270 and 350 nm, representing the size of molecular weight of CDOM and humic-like composition, decreased by 8.7%, 34.6%, 39.4%, 53.1%, 46.7%, and 35.7%, respectively. Applying parallel factor analysis (PARAFAC) together with EEM got four components of CDOM: C1(Ex/Em=350(260) nm/450 nm), C2 (Ex/Em=260(430) nm/525 nm), C3 (Ex/Em=325 nm/400 nm) and C4(Ex/Em=275 nm/325 nm), which were relative to three humic-like and one protein-like fluorescent components of Nitzschia closterium f. minutissima and Navicula halophile. In incubation experiment, fluorescence intensity of these four components during growth of Nitzschia closterium f. minutissima increased by, respectively, 8.68, 24.9, 7.19 and 39.8 times, and those of Navicula halophile increased by 2.64, 0.07, 4.39 and 12.4 times, respectively. Significant relationships were found between the fluorescence intensity of four components of CDOM, a(355) and Sg. All results demonstrated that both content and molecular weight of CDOM produced by diatom and dinoflagellate studied in incubation experiment increased, but these two parameters changed more obviously of the diatom than those of dinoflagellate; the proportion of humic-like components in the composition of CDOM

  9. [Research on the influence of LED temperature shifts on differential optical absorption spectroscopy for measuring NO2].

    PubMed

    Ling, Liu-Yi; Xie, Pin-Hua; Qin, Min; Zheng, Ni-Na; Ye, Cong-Lei; Li, Ang; Hu, Ren-Zhi

    2012-11-01

    Influences of LEDs (without etalon structure and center wavelengths are respectively 370 nm (near-UV), 452 nm (blue) and 660 nm(red)) temperature shifts on differential optical absorption spectroscopy(DOAS) for measuring NO2 were studied. NO2 absorption spectra were formed using LED emitting spectra at 10 degrees C. The measured LED spectra at other temperatures were used as reference spectra of DOAS. Thus, NO2 differential optical densities under different LED temperature shifts were acquired and then NO2 differential cross-sections were fitted to the acquired differential optical densities. From fitting results, the linear relations of 0.995, 0.945 and 0.989 correlation between delta of fitting residual and near-UV, blue and red LEDs temperature shifts were found and their slopes are respectively 1.12 x 10(-3), 5.25 x 10(-5) and 7.45 x 10(-4) degrees C(-1). The fitting results show that the influence of temperature shifts of blue LED on DOAS retrieval is negligible and the temperature shifts of near-UV and red LED are impressible to DOAS measurement resulting in degradation of detection sensitivity. The retrieval results of blue LED with and without etalon with similar temperature properties were compared and showed that etalon of LED will greatly increase the influence of temperature shifts of LED on DOAS retrieval. PMID:23387143

  10. Third-Order Nonlinear Optical Properties and Optical Switching of Palladium (I) Complex

    NASA Astrophysics Data System (ADS)

    Manjunatha, K. B.; Dileep, R.; Vikas, M. Shelar; Umesh, G.; Satyanarayan, M. N.; Bhat, B. Ramachandra

    2011-10-01

    We report the third-order nonlinear optical, optical power limiting and optical switching study of palladium-N-(2-pyridyl)-N'- (5-amino salicylidene) hydrazine triphenylphosphine, using Z-scan technique and pump-probe technique. The measured nonlinear refractive index is n2 = -6.022×10-9 esu. The complex exhibits the reverse saturable absorption (RSA), the nonlinear absorption coefficient of β = 10.748×10-9 m/W. The good optical power limiting and optical switching behavior were observed in this complex. These suggest that this complex is a potential molecule for photonic applications.

  11. Properties of an optical soliton gas

    NASA Astrophysics Data System (ADS)

    Schwache, A.; Mitschke, F.

    1997-06-01

    We consider light pulses propagating in an optical fiber ring resonator with anomalous dispersion. New pulses are fed into the resonator in synchronism with its round-trip time. We show that solitary pulse shaping leads to a formation of an ensemble of subpulses that are identified as solitons. All solitons in the ensemble are in perpetual relative motion like molecules in a fluid; thus we refer to the ensemble as a soliton gas. Properties of this soliton gas are determined numerically.

  12. Modelling of thermally detected optical absorption and luminescence of (In,Ga)N/GaN heterostructures

    NASA Astrophysics Data System (ADS)

    Siozade, L.; Leymarie, J.; Disseix, P.; Vasson, A.; Mihailovic, M.; Grandjean, N.; Leroux, M.; Massies, J.

    2000-08-01

    Thermally detected optical absorption (TDOA) and photoluminescence (PL) experiments are performed at 0.35 and 4 K, respectively, on In xGa 1- xN ( x≤0.12) layers grown on GaN by molecular beam epitaxy. The modelling of absorption allows us to extract the absorption coefficients and bandgap energies of (In,Ga)N alloy. A bowing parameter equal to 2.4 eV is deduced. The knowledge of the GaN complex refractive index, previously measured, enables us to account for the Fabry-Perot interferences which structure the TDOA and PL spectra. A procedure is proposed to remove the latter in the PL spectrum of nitride based heterostructures. The model is based on the description of the light propagation in an active layer sandwiched between two heterostructures. The parameters deduced from the absorption line shape adjustment are used to take the absorption and optical path into account in the different layers of the samples.

  13. Polymer based nanocomposites with tailorable optical properties

    NASA Astrophysics Data System (ADS)

    Colombo, Annalisa; Simonutti, Roberto

    2014-09-01

    Transparent polymers are extensively used in everyday life, from windows to computer displays, from food packaging to lenses. A possible approach for modulating their optical properties (refractive index, transparency, color and luminescence) is to change the chemical structure of the polymer, however this option is in many cases economically prohibitive. Our approach, instead, relies in the use of standard polymers with the supplement of specific nanostructured additives able to tune the final property of the material. Among others, the cases of luminescent solar concentrators based on poly(methylmethacrylate) containing luminescent quantum dots and highly transparent polymer nanocomposites with high refractive index will be presented.

  14. All-electron first-principles GW+Bethe-Salpeter calculation for optical absorption spectra of sodium clusters

    SciTech Connect

    Noguchi, Yoshifumi; Ohno, Kaoru

    2010-04-15

    The optical absorption spectra of sodium clusters (Na{sub 2n}, n{<=} 4) are calculated by using an all-electron first-principles GW+Bethe-Salpeter method with the mixed-basis approach within the Tamm-Dancoff approximation. In these small systems, the excitonic effect strongly affects the optical properties due to the confinement of exciton in the small system size. The present state-of-the-art method treats the electron-hole two-particle Green's function by incorporating the ladder diagrams up to the infinite order and therefore takes into account the excitonic effect in a good approximation. We check the accuracy of the present method by comparing the resulting spectra with experiments. In addition, the effect of delocalization in particular in the lowest unoccupied molecular orbital in the GW quasiparticle wave function is also discussed by rediagonalizing the Dyson equation.

  15. [Measurement of atmospheric NO3 radical with long path differential optical absorption spectroscopy based on red light emitting diodes].

    PubMed

    Li, Su-Wen; Liu, Wen-Qing; Wang, Jiang-Tao; Xie, Pin-Hua; Wang, Xu-De

    2013-02-01

    Nitrate radical (NO3) is the most important oxidant in the tropospheric nighttime chemistry. Due to its high reactivity and low atmospheric concentrations, modern red light emitting diodes (LEDs) was proposed as light source in long path differential optical absorption spectroscopy (LP-DOAS) to measure NO3 radical in the atmosphere. The spectral properties of Luxeon LXHL-MD1D LEDs were analyzed in the present paper. The principle of LEDs-DOAS system to measure nitrate radical was studied in this paper. The experimental setup and retrieval method of NO3 radical were discussed in this paper. The retrieved example of NO3 was given and the time series of NO3 concentrations was performed for a week. The results showed that the detection limits of LEDs-DOAS system were 12 ppt for atmospheric NO3 radical when the optical path of LEDs-DOAS system was 2.8 km. PMID:23697129

  16. Remote-Sensing Reflectance and Inherent Optical Properties for Optically Deep Waters: A Revisit

    NASA Technical Reports Server (NTRS)

    Lee, Zhong-Ping; Carder, Kendall L.; Du, Ke-Ping

    2001-01-01

    Remote-sensing reflectance (r(rs)) is defined as the ratio of upwelling radiance to downwelling irradiance. Relationships between remote-sensing reflectance and inherent optical properties serve as the basis for ocean-color modeling, as well as for spectral deduction of oceanic constituents through analytical/semi-analytical models of ocean color. A decade ago, a simple and concise formula based on Monte Carlo simulations was developed by relating rrs to a property u, the ratio of backscattering (b(b)) to the sum of absorption (a) and backscattering (u = b(b)/(a+b(b))). This relationship generally ignored the shape differences in phase functions between molecular scattering and particle scattering. In this study, the relationship is updated with separate parameters for molecular and particle scattering, based on the Radiative Transfer Equation through use of Hydrolight numerical solutions. The new approach fits r(rs) better than an earlier traditional formula, for both clear and turbid waters.

  17. Crystal structure and nonlinear optical absorption of a new chalcone derivative: a promising candidate for optical switching

    NASA Astrophysics Data System (ADS)

    Chandra Shekhara Shetty, T.; Raghavendra, S.; Chidan Kumar, C. S.; Dharmaprakash, S. M.

    2016-07-01

    A new nonlinear optical material, 4-[(2 E)-3-(3-fluorophenyl) prop-2-enoyl] benzonitrile (3FPB), belonging to chalcone family was synthesized and characterized by FTIR and linear absorption spectroscopy. Single-crystal X-ray diffraction reveals that the new material crystallizes in monoclinic system with P21/c space group and lattice parameters a = 6.4841(2) Å, b = 13.6038(5) Å, c = 14.6418(6) Å, α = 90.00°, β = 94.552(2)° and γ = 90°. The crystallographic perfection of the synthesized material has been analyzed by X-ray powder diffraction. The X-ray powder diffraction peaks of the sample were indexed with hkl values. The UV-visible spectrum for 3FPB crystals showed the optical transmittance window and a lower cutoff wavelength of absorption at 343 nm. The direct transition band gap energy and indirect transition energy gap were determined using Tauc's plots. The thermal stability and melting point of the material have been investigated by thermogravimetric analysis/differential thermal analysis (TGA/DTA). The Thermogravimetric curve showed the absence of any phase transition before melting point. Third-order nonlinear absorption and optical limiting experiment were carried out using open-aperture Z-scan experiment with Nd:YAG laser nanosecond pulses at a wavelength of 532 nm.

  18. Optical properties of neonatal skin measured in vivo as a function of age and skin pigmentation

    NASA Astrophysics Data System (ADS)

    Bosschaart, Nienke; Mentink, Rosaline; Kok, Joke H.; van Leeuwen, Ton G.; Aalders, Maurice C. G.

    2011-09-01

    Knowledge of the optical properties of neonatal skin is invaluable when developing new, or improving existing optical techniques for use at the neonatal intensive care. In this article, we present in vivo measurements of the absorption μa and reduced scattering coefficient μs' of neonatal skin between 450 and 600 nm and assess the influence of age and skin pigmentation on the optical properties. The optical properties were measured using a spatially resolved, steady state diffuse reflectance spectroscopy setup, combined with a modified spatially resolved diffusion model. The method was validated on phantoms with known values for the absorption and reduced scattering coefficient. Values of μa and μs' were obtained from the skin at four different body locations (forehead, sternum, hand, and foot) of 60 neonates with varying gestational age, postnatal age, and skin pigmentation. We found that μa ranged from 0.02 to 1.25 mm-1 and μs' was in the range of 1 to 2.8 mm-1 (5th to 95th percentile of the patient population), independent of body location. In contrast to previous studies, no to very weak correlation was observed between the optical properties and gestational maturity, but a strong dependency of the absorption coefficient on postnatal age was found for dark skinned patients.

  19. Electronic and optical properties of K-doped ZnO: Ab initio study

    NASA Astrophysics Data System (ADS)

    Aimouch, D. E.; Meskine, S.; Hayn, R.; Zaoui, A.; Boukortt, A.

    2016-08-01

    We present the results of ab initio calculations of K-doped ZnO in the wurtzite structure using a supercell of 32 atoms and density functional theory. A complete analysis of its electronic, optical and magnetic properties is provided. The local spin density approximation (LSDA) has been used to analyze the density of states and to understand the K influence at different concentration values. The material is revealed to become a p-type doped semiconductor. The optical constant or refractive index, the dielectric function, and the absorption coefficient were determined and show a good agreement with available experimental data. Potassium doping leads to an absorption peak at about 380 nm. That peak might improve the absorption characteristics of ZnO for solar cell or optical applications.

  20. Spectroscopic and fiber optic ethanol sensing properties Gd doped ZnO nanoparticles.

    PubMed

    Noel, J L; Udayabhaskar, R; Renganathan, B; Muthu Mariappan, S; Sastikumar, D; Karthikeyan, B

    2014-11-11

    We report the structural, optical and gas sensing properties of prepared pure and Gd doped ZnO nanoparticles through solgel method at moderate temperature. Structural studies are carried out by X-ray diffraction method confirms hexagonal wurtzite structure and doping induced changes in lattice parameters is observed. Optical absorption spectral studies shows red shift in the absorption peak corresponds to band-gap from 3.42 eV to 3.05 eV and broad absorption in the visible range after Gd doping is observed. Scanning electron microscopic studies shows increase in particle size where the particle diameters increase from few nm to micrometers after Gd doping. The clad modified ethanol fiber-optic sensor studies for ethanol sensing exhibits best sensitivity for the 3% Gd doped ZnO nanoparticles and the sensitivity get lowered incase of higher percentage of Gd doped ZnO sample.

  1. Spectroscopic and fiber optic ethanol sensing properties Gd doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Noel, J. L.; Udayabhaskar, R.; Renganathan, B.; Muthu Mariappan, S.; Sastikumar, D.; Karthikeyan, B.

    2014-11-01

    We report the structural, optical and gas sensing properties of prepared pure and Gd doped ZnO nanoparticles through solgel method at moderate temperature. Structural studies are carried out by X-ray diffraction method confirms hexagonal wurtzite structure and doping induced changes in lattice parameters is observed. Optical absorption spectral studies shows red shift in the absorption peak corresponds to band-gap from 3.42 eV to 3.05 eV and broad absorption in the visible range after Gd doping is observed. Scanning electron microscopic studies shows increase in particle size where the particle diameters increase from few nm to micrometers after Gd doping. The clad modified ethanol fiber-optic sensor studies for ethanol sensing exhibits best sensitivity for the 3% Gd doped ZnO nanoparticles and the sensitivity get lowered incase of higher percentage of Gd doped ZnO sample.

  2. Linear and nonlinear optical properties of gold nanoparticle-Eu oxide composite thin films

    NASA Astrophysics Data System (ADS)

    Henari, F. Z.; Dakhel, A. A.

    2008-08-01

    In this work, nanogold particles incorporated onto europium oxide films at levels of 4% and 7% were fabricated by a vacuum evaporation technique on glass and silicon substrates held at 200 °C. Samples were investigated by x-ray diffraction and linear and nonlinear optical absorption. The linear optical absorption data were measured in the UV-visible-near infrared spectral regions and from these data the energy gap and the surface plasmon resonance were determined. The third order nonlinear optical properties of the nanogold particles incorporated onto europium oxide films were measured using the Z-scan technique. Nonlinear absorption and refraction were performed using a continuous wave laser at 633 nm. A large value of third order nonlinearities was obtained with the samples.

  3. Spectral properties of microwave graphs with local absorption.

    PubMed

    Allgaier, Markus; Gehler, Stefan; Barkhofen, Sonja; Stöckmann, H-J; Kuhl, Ulrich

    2014-02-01

    The influence of absorption on the spectra of microwave graphs has been studied experimentally. The microwave networks were made up of coaxial cables and T junctions. First, absorption was introduced by attaching a 50Ω load to an additional vertex for graphs with and without time-reversal symmetry. The resulting level-spacing distributions were compared with a generalization of the Wigner surmise in the presence of open channels proposed recently by Poli et al. [Phys. Rev. Lett. 108, 174101 (2012)]. Good agreement was found using an effective coupling parameter. Second, absorption was introduced along one individual bond via a variable microwave attenuator, and the influence of absorption on the length spectrum was studied. The peak heights in the length spectra corresponding to orbits avoiding the absorber were found to be independent of the attenuation, whereas, the heights of the peaks belonging to orbits passing the absorber once or twice showed the expected decrease with increasing attenuation.

  4. Ultraviolet absorption and luminescence properties of some cannabis constituents.

    PubMed

    Bowd, A; Byrom, P; Hudson, J B; Turnbull, J H

    1971-07-01

    The characteristics of the absorption, fluorescence and phosphorescence spectra of the cannabinols have been determined. The data provide a basis for the detection of these compounds at concentrations down to 10 ng ml .

  5. Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

    DOEpatents

    Cremers, D.A.; Keller, R.A.

    1982-06-08

    The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be rlated to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10/sup -5/ cm/sup -1/ has been demonstrated using this technique.

  6. Apparatus and method for measurement of weak optical absorptions by thermally induced laser pulsing

    DOEpatents

    Cremers, David A.; Keller, Richard A.

    1985-01-01

    The thermal lensing phenomenon is used as the basis for measurement of weak optical absorptions when a cell containing the sample to be investigated is inserted into a normally continuous-wave operation laser-pumped dye laser cavity for which the output coupler is deliberately tilted relative to intracavity circulating laser light, and pulsed laser output ensues, the pulsewidth of which can be related to the sample absorptivity by a simple algorithm or calibration curve. A minimum detection limit of less than 10.sup.-5 cm.sup.-1 has been demonstrated using this technique.

  7. Research of difference absorption optical fiber CO gas sensor based on FBG

    NASA Astrophysics Data System (ADS)

    Wang, Yanju; Liu, Zhihua; Kang, Yueyi; Wang, Yutian

    2009-07-01

    Based on analysis of the near infrared spectral absorption of CO molecule and considering factors such as compatibility with the transmission characteristics of silica optical fiber and the price, a kind of allfiber remote sensor utilizing Fiber Bragg Grating(FBG) filters and 1.567μm high power light-emitting diode (LED) was developed for real time absorption measurement. FBG has a low insert loss and can be produced easily compared with dielectric interference filters. Theory and experiment proved that the system has simple construct and high sensibility.

  8. Optical absorption and luminescence studies of fast neutron-irradiated complex oxides for jewellery applications

    NASA Astrophysics Data System (ADS)

    Mironova-Ulmane, N.; Skvortsova, V.; Popov, A. I.

    2016-07-01

    We studied the optical absorption and luminescence of agate (SiO2), topaz (Al2[SiO4](F,OH)2), beryl (Be3Al2Si6O18), and prehnite (Ca2Al(AlSi3O10)(OH)2) doped with different concentrations of transition metal ions and exposed to fast neutron irradiation. The exchange interaction between the impurity ions and the defects arising under neutron irradiation causes additional absorption as well as bands' broadening in the crystals. These experimental results allow us to suggest the method for obtaining new radiation-defect induced jewellery colors of minerals due to neutron irradiation.

  9. Performance of a high-resolution mid-IR optical-parametric-oscillator transient absorption spectrometer.

    PubMed

    Echebiri, Geraldine O; Smarte, Matthew D; Walters, Wendell W; Mullin, Amy S

    2014-06-16

    We report on a mid-IR optical parametric oscillator (OPO)-based high resolution transient absorption spectrometer for state-resolved collisional energy transfer. Transient Doppler-broadened line profiles at λ = 3.3 μm are reported for HCl R7 transitions following gas-phase collisions with vibrationally excited pyrazine. The instrument noise, analyzed as a function of IR wavelength across the absorption line, is as much as 10 times smaller than in diode laser-based measurements. The reduced noise is attributed to larger intensity IR light that has greater intensity stability, which in turn leads to reduced detector noise and better frequency locking for the OPO.

  10. Recent Progress Towards Quantum Dot Solar Cells with Enhanced Optical Absorption

    NASA Astrophysics Data System (ADS)

    Zheng, Zerui; Ji, Haining; Yu, Peng; Wang, Zhiming

    2016-05-01

    Quantum dot solar cells, as a promising candidate for the next generation solar cell technology, have received tremendous attention in the last 10 years. Some recent developments in epitaxy growth and device structures have opened up new avenues for practical quantum dot solar cells. Unfortunately, the performance of quantum dot solar cells is often plagued by marginal photon absorption. In this review, we focus on the recent progress made in enhancing optical absorption in quantum dot solar cells, including optimization of quantum dot growth, improving the solar cells structure, and engineering light trapping techniques.

  11. Recent Progress Towards Quantum Dot Solar Cells with Enhanced Optical Absorption.

    PubMed

    Zheng, Zerui; Ji, Haining; Yu, Peng; Wang, Zhiming

    2016-12-01

    Quantum dot solar cells, as a promising candidate for the next generation solar cell technology, have received tremendous attention in the last 10 years. Some recent developments in epitaxy growth and device structures have opened up new avenues for practical quantum dot solar cells. Unfortunately, the performance of quantum dot solar cells is often plagued by marginal photon absorption. In this review, we focus on the recent progress made in enhancing optical absorption in quantum dot solar cells, including optimization of quantum dot growth, improving the solar cells structure, and engineering light trapping techniques.

  12. Metallic nanoshells with semiconductor cores: optical characteristics modified by core medium properties.

    PubMed

    Bardhan, Rizia; Grady, Nathaniel K; Ali, Tamer; Halas, Naomi J

    2010-10-26

    It is well-known that the geometry of a nanoshell controls the resonance frequencies of its plasmon modes; however, the properties of the core material also strongly influence its optical properties. Here we report the synthesis of Au nanoshells with semiconductor cores of cuprous oxide and examine their optical characteristics. This material system allows us to systematically examine the role of core material on nanoshell optical properties, comparing Cu(2)O core nanoshells (ε(c) ∼ 7) to lower core dielectric constant SiO(2) core nanoshells (ε(c) = 2) and higher dielectric constant mixed valency iron oxide nanoshells (ε(c) = 12). Increasing the core dielectric constant increases nanoparticle absorption efficiency, reduces plasmon line width, and modifies plasmon energies. Modifying the core medium provides an additional means of tailoring both the near- and far-field optical properties in this unique nanoparticle system. PMID:20860401

  13. EPR, optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

    NASA Astrophysics Data System (ADS)

    De Vicente, F. S.; Santos, F. A.; Simões, B. S.; Dias, S. T.; Siu Li, M.

    2014-12-01

    Antimony phosphate glasses (SbPO) doped with 3 and 6 mol% of Cr3+ were studied by Electron Paramagnetic Resonance (EPR), UV-VIS optical absorption and luminescence spectroscopy. The EPR spectra of Cr3+-doped glasses showed two principal resonance signals with effective g values at g = 5.11 and g = 1.97. UV-VIS optical absorption spectra of SbPO:Cr3+ presented four characteristics bands at 457, 641, 675, and 705 nm related to the transitions from 4A2(F) to 4T1(F), 4T2(F), 2T1(G), and 2E(G), respectively, of Cr3+ ions in octahedral symmetry. Optical absorption spectra of SbPO:Cr3+ allowed evaluating the crystalline field Dq, Racah parameters (B and C) and Dq/B. The calculated value of Dq/B = 2.48 indicates that Cr3+ ions in SbPO glasses are in strong ligand field sites. The optical band gap for SbPO and SbPO:Cr3+ were evaluated from the UV optical absorption edges. Luminescence measurements of pure and Cr3+-doped glasses excited with 350 nm revealed weak emission bands from 400 to 600 nm due to the 3P1 → 1S0 electronic transition from Sb3+ ions. Cr3+-doped glasses excited with 415 nm presented Cr3+ characteristic luminescence spectra composed by two broad bands, one band centered at 645 nm (2E → 4A2) and another intense band from 700 to 850 nm (4T2 → 4A2).

  14. The effect of implanting boron on the optical absorption and electron paramagnetic resonance spectra of silica

    NASA Astrophysics Data System (ADS)

    Magruder, R. H.; Stesmans, A.; Weeks, R. A.; Weller, R. A.

    2008-09-01

    Silica samples (type III, Corning 7940) were implanted with B using multiple energies to produce a layer ˜600 nm thick in which the concentration of B ranged from 0.034 to 2.04 at. %. Optical absorption spectra were measured from 1.8 to 6.5 eV. Electron paramagnetic resonance (EPR) measurements were generally made at ˜20.3 and 33 GHz for sample temperatures ranging from 77 to 100 K. Based on the EPR spectra three types of defects, namely, Eγ', the E'-type 73 G split doublet (E73'), and the peroxyradical (POR) were identified. No oxygen-associated hole centers (OHCs) nor specific B-associated paramagnetic defects were detected, not even at the largest B concentration of 2.04 at. %. Unlike previous assignments, there was no correlation between the 4.83 eV optical absorption band and the observed PORs. From these results, we infer that in addition to POR, there is at least one additional Si-related state absorbing in the 4.8-4.9 eV range that is likely diamagnetic. The 5.85 eV optical absorption band is found to be due to the Eγ' and E73' centers, with, in average, quite similar oscillator strengths inferred as before. Both the optical absorption and the electron spin resonance data can be satisfactorily explained without the need for specific B-associated defect site (s). As no OHCs are detected by ESR, these do not seem to make a detectable contribution to the optical spectra.

  15. A universal feature in the optical absorption spectrum associated with hydrogenated amorphous silicon: A dimensionless joint density of states analysis

    NASA Astrophysics Data System (ADS)

    Thevaril, Jasmin J.; O'Leary, Stephen K.

    2016-10-01

    Using a dimensionless joint density of states formalism for the quantitative characterization of the optical response associated with hydrogenated amorphous silicon, a critical comparative analysis of a large number of different optical absorption data sets is considered. When these data sets are cast into this dimensionless framework, we observe a trend that is almost completely coincident for all of the data sets considered. This suggests that there is a universal feature associated with the optical absorption spectrum of hydrogenated amorphous silicon.

  16. Molecular dynamics simulations for the study of optical properties in conjugated semiconducting molecules

    NASA Astrophysics Data System (ADS)

    Wildman, Jack; Denis, Jean-Christophe; Repiščák, Peter; Paterson, Martin J.; Galbraith, Ian

    Conformational disorder of conjugated polymers strongly influences their optical and electronic properties. Molecular Dynamics (MD) simulations can provide a quantitative understanding of these effects. Given the ever-expanding range of molecules with potential for device applications, it is critical to systematically establish accurate MD parameters for such simulations. We present an experimentally verified, general and optimised procedure, based on a computationally inexpensive methodology for generating the required MD parameters for conjugated molecules. By combining a large sample (~1000) of MD generated conformations with DFT calculations for the resulting electronic states we can explore the influence of conformational disorder on the optical properties. Using this scheme, we determine the effect of conformational variation on both linear and two-photon absorption spectra in a number of different conjugated semiconducting oligomers. Our results indicate that, while there exists significant inhomogeneous broadening in the linear absorption, there is only a weak conformational influence on the two-photon absorption spectrum.

  17. Optical absorption spectra of substitutional Co2+ ions in Mgx Cd1-x Se alloys

    NASA Astrophysics Data System (ADS)

    Jin, Moon-Seog; Kim, Chang-Dae; Jang, Kiwan; Park, Sang-An; Kim, Duck-Tae; Kim, Hyung-Gon; Kim, Wha-Tek

    2006-09-01

    Optical absorption spectra of substitutional Co2+ ions in Mgx Cd1-x Se alloys were investigated in the composition region of 0.0 x 0.4 and in the wavelength region of 300 to 2500 nm at 4.8 K and 290 K. We observed several absorption bands in the wavelength regions corresponding to the 4A2(4F) 4T1(4P) transition and the 4A2(4F) 4T1(4F) transition of Co2+ at a tetrahedral Td point symmetry point in the host crystals, as well as unknown absorption bands. The several absorption bands were analyzed in the framework of the crystal-field theory along with the second-order spin-orbit coupling. The unknown absorption bands were assigned as due to phonon-assisted absorption bands. We also investigated the variations of the crystal-field parameter Dq and the Racah parameter B with composition x in the Mgx Cd1-x Se system. The results showed that the crystal-field parameter (Dq ) increases, on the other hand, the Racah parameter (B ) decreases with increasing composition x, which may be connected with an increase in the covalency of the metal-ligand bond with increasing composition x in the Mgx Cd1-x Se system.

  18. pH-Induced Modulation of One- and Two-Photon Absorption Properties in a Naphthalene-Based Molecular Probe.

    PubMed

    Murugan, N Arul; Kongsted, Jacob; Ågren, Hans

    2013-08-13

    Presently, there is a great demand for small probe molecules that can be used for two-photon excitation microscopy (TPM)-based monitoring of intracellular and intraorganelle activity and pH. The candidate molecules should ideally possess a large two-photon absorption cross section with optical properties sensitive to pH changes. In the present work, we investigate the potential of a methoxy napthalene (MONAP) derivative for its suitability to serve as a pH sensor using TPM. Using an integrated approach rooted in hybrid quantum mechanics/molecular mechanics, the structures, dynamics, and the one- and two-photon properties of the probe in dimethylformamide solvent are studied. It is found that the protonated form is responsible for the optical property of MONAP at moderately low pH, for which the calculated pH-induced red shift is in good agreement with experiments. A 2-fold increase in the two-photon absorption cross section in the IR region of the spectrum is predicted for the moderately low pH form of the probe, suggesting that this can be a potential probe for pH monitoring of living cells. We also propose some design principles aimed at obtaining control of the absorption spectral range of the probe by structural tuning. Our work indicates that the integrated approach employed is capable of capturing the pH-induced changes in structure and optical properties of organic molecular probes and that such in silico tools can be used to draw structure-property relationships to design novel molecular probes suitable for a specific application.

  19. Symmetry, Optical Properties and Thermodynamics of Neptunium(V) Complexes

    SciTech Connect

    Rao, Linfeng; Tian, Guoxin

    2009-12-21

    Recent results on the optical absorption and symmetry of the Np(V) complexes with dicarboxylate and diamide ligands are reviewed. The importance of recognizing the 'silent' feature of centrosymmetric Np(V) species in analyzing the absorption spectra and calculating the thermodynamic constants of Np(V) complexes is emphasized.

  20. Optical closure in marine waters from in situ inherent optical property measurements.

    PubMed

    Lefering, Ina; Bengil, Fethi; Trees, Charles; Röttgers, Rüdiger; Bowers, David; Nimmo-Smith, Alex; Schwarz, Jill; McKee, David

    2016-06-27

    Optical closure using radiative transfer simulations can be used to determine the consistency of in situ measurements of inherent optical properties (IOPs) and radiometry. Three scattering corrections are applied to in situ absorption and attenuation profile data for a range of coastal and oceanic waters, but are found to have only very limited impact on subsequent closure attempts for these stations. Best-fit regressions on log-transformed measured and modelled downwards irradiance, Ed, and upwards radiance, Lu, profiles have median slopes between 0.92 - 1.24, revealing a tendency to underestimate Ed and Lu with depth. This is only partly explained by non-inclusion of fluorescence emission from CDOM and chlorophyll in the simulations. There are several stations where multiple volume scattering function related data processing steps perform poorly which suggests the potential existence of unresolved features in the modelling of the angular distribution of scattered photons. General optical closure therefore remains problematic, even though there are many cases in the data set where the match between measured and modelled radiometric data is within 25% RMS%E. These results are significant for applications that rely on optical closure e.g. assimilating ocean colour data into coupled physical-ecosystem models. PMID:27410565

  1. Optical properties of polypropylene upon recycling.

    PubMed

    De Santis, Felice; Pantani, Roberto

    2013-01-01

    In the last few years there has been an increasing interest in the possibility of recycling polymeric materials, using physical recycling. However, is it well known that polymers experience a depletion of all the properties upon recycling. These effects have been widely characterized in the literature for what concerns the mechanical or rheological properties. The changes of optical properties after recycling have been much less studied, even if, especially in food packaging, optical characteristics (above all the opacity) are of extreme importance, and thus it is quite significant to assess the effect of recycling on these properties. In this work, the influence of recycling steps on the opacity of films of a commercial grade of isotactic polypropylene (i-PP) was studied. The material was extruded several times to mimic the effect of recycling procedures. After extrusion, films were obtained by cooling samples of material at different cooling rates. The opacity of the obtained films was then measured and related to their crystallinity and morphology. It was found that opacity generally increases on increasing the amount of α phase and for the same amount of α phase on increasing the size of the spherulites.

  2. Optical properties of polypropylene upon recycling.

    PubMed

    De Santis, Felice; Pantani, Roberto

    2013-01-01

    In the last few years there has been an increasing interest in the possibility of recycling polymeric materials, using physical recycling. However, is it well known that polymers experience a depletion of all the properties upon recycling. These effects have been widely characterized in the literature for what concerns the mechanical or rheological properties. The changes of optical properties after recycling have been much less studied, even if, especially in food packaging, optical characteristics (above all the opacity) are of extreme importance, and thus it is quite significant to assess the effect of recycling on these properties. In this work, the influence of recycling steps on the opacity of films of a commercial grade of isotactic polypropylene (i-PP) was studied. The material was extruded several times to mimic the effect of recycling procedures. After extrusion, films were obtained by cooling samples of material at different cooling rates. The opacity of the obtained films was then measured and related to their crystallinity and morphology. It was found that opacity generally increases on increasing the amount of α phase and for the same amount of α phase on increasing the size of the spherulites. PMID:24288478

  3. Optical Properties of Polypropylene upon Recycling

    PubMed Central

    2013-01-01

    In the last few years there has been an increasing interest in the possibility of recycling polymeric materials, using physical recycling. However, is it well known that polymers experience a depletion of all the properties upon recycling. These effects have been widely characterized in the literature for what concerns the mechanical or rheological properties. The changes of optical properties after recycling have been much less studied, even if, especially in food packaging, optical characteristics (above all the opacity) are of extreme importance, and thus it is quite significant to assess the effect of recycling on these properties. In this work, the influence of recycling steps on the opacity of films of a commercial grade of isotactic polypropylene (i-PP) was studied. The material was extruded several times to mimic the effect of recycling procedures. After extrusion, films were obtained by cooling samples of material at different cooling rates. The opacity of the obtained films was then measured and related to their crystallinity and morphology. It was found that opacity generally increases on increasing the amount of α phase and for the same amount of α phase on increasing the size of the spherulites. PMID:24288478

  4. Investigation of nonlinear optical properties of various organic materials by the Z-scan method

    NASA Astrophysics Data System (ADS)

    Ganeev, R. A.; Boltaev, G. S.; Tugushev, R. I.; Usmanov, T.

    2012-06-01

    We have studied the nonlinear optical properties of various organic materials (vegetable oil, juice, wine, cognac, Coca-Cola and Fanta drinks, Nescafé coffee, tea, gasoline, clock oil, glycerol, and polyphenyl ether) that are used in everyday life. Their nonlinearities have been studied by the Z-scan method in the near-IR and visible spectral ranges. We have shown that the majority of samples possess a nonlinear absorption; however, some of the studied materials show a strong saturated absorption and nonlinear refraction. Red wine and glycerol proved to be the most interesting materials. For these samples, we have observed a change in the sign of the nonlinear absorption with increasing laser intensity, which was attributed to the competition between two-photon absorption and saturated absorption.

  5. Measurement of the optical properties of rat brain tissue using contact spatially resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Gysbrechts, Barbara; Nguyen Do Trong, Nghia; Wang, Ling; Cabral, Henrique; Navratilova, Zaneta; Battaglia, Francesco P.; Saeys, Wouter; Bartic, Carmen

    2014-05-01

    Nowadays, biophotonics is widely used in neuroscience. The effectiveness of biophotonic techniques, such as fluorescence imaging and optogenetics, is affected by the optical properties of the examined tissue. Therefore, knowledge of these properties is essential to carefully plan experiments. Mice and rats are widely used in neuroscience studies. However, reports about optical properties of their brains are very rare. We measured optical absorption μa and reduced scattering μ's coefficients of native rat brain in the visible and near-infrared wavelength region, using contact spatially resolved spectroscopy (SRS). In this study, we estimate μa and μ's for the rat cortex and discuss their stability in time. Additionally, variations in optical properties within and between samples were characterized. The results extend the range of known optical properties for the rat cortex, especially in the visible range, relevant to optogenetics. μa and μ's are stable within a time span of four hours, and show low variation in and between brain samples. This indicates that a suitable protocol was used to estimate optical properties of rodent brain tissue. Since contact SRS is a non-destructive method, this technique could be used also to measure μa and μ's in living animals. Moreover, the probe has small dimensions, allowing the characterization of optical properties in different structures of the brain.

  6. Significant enhancement of optical absorption through nano-structuring of copper based oxide semiconductors: possible future materials for solar energy applications.

    PubMed

    Bhaumik, Anagh; Shearin, Austin M; Patel, Rishi; Ghosh, Kartik

    2014-06-14

    The optical absorption coefficient is a crucial parameter in determining solar cell efficiency under operational conditions. It is well known that inorganic nanocrystals are a benchmark model for solar cell nanotechnology, given that the tunability of optical properties and stabilization of specific phases are uniquely possible at the nanoscale. A hydrothermal method was employed to fabricate nanostructured copper oxides where the shape, size and phase were tailored by altering the growth parameters, namely the base media used, the reaction temperature, and the reaction time. The nano crystalline structures, phases, morphology, molecular vibrational modes, and optical properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL), and UV-vis spectroscopy. A significantly large optical absorption coefficient, of the order of twice that of Si in the visible range, was observed in a particular phase mixture of nanostructured copper oxides. An optical absorption coefficient of 7.05 10(+5) cm(-1) at 525 nm was observed in a particular nanostructured phase mixture of copper oxides which is appreciably larger than commercially pure CuO (1.19 10(+5) cm(-1)) and Si (1.72 10(+5) cm(-1)). A possible mechanism of formation of phase mixtures and morphology of copper oxides has also been discussed, which opens up a roadmap in synthesis of similar morphology nanostructures for efficient solar cells.

  7. Active optics for dynamical correction of fluctuations of atmospheric refraction on a differential optical absorption spectroscopy device.

    PubMed

    Fuentes-Inzunza, Rodrigo A; Gutiérrez, Javier; Saavedra, Carlos

    2012-10-20

    We have designed and developed a feedback mechanism for continuous monitoring in a long-pass differential optical absorption spectroscopy (LP-DOAS) setup. This allows one to correct photo-thermal deflection due to the local fluctuations refraction index of the air. For this purpose, using an unbalanced beam splitter, a small fraction of the collected DOAS signal is imaged onto a low-cost CCD camera using a biconvex lens, while the other portion of the signal is coupled into a fiber optic for trace gas detection. By monitoring the registered signal at the CCD camera, a feedback mechanism acting on the transversal position of the lens is able to compensate an arbitrary transversal displacement of the collected signal at the focal plane of the receiver telescope, allowing an optimal coupling into the optical fiber. PMID:23089775

  8. Optical properties monitor: Experiment definition phase

    NASA Technical Reports Server (NTRS)

    Wilkes, Donald R.; Bennett, Jean M.; Hummer, Leigh L.; Chipman, Russell A.; Hadaway, James B.; Pezzaniti, Larry

    1990-01-01

    The stability of materials used in the space environment will continue to be a limiting technology for space missions. The Optical Properties Monitor (OPM) Experiment provides a comprehensive space research program to study the effects of the space environment (both natural and induced) on optical, thermal and space power materials. The OPM Experiment was selected for definition under the NASA/OAST In-Space Technology Experiment Program. The results of the OPM Definition Phase are presented. The OPM experiment will expose selected materials to the space environment and measure the effects with in-space optical measurements. In-space measurements include total hemispherical reflectance total integrated scatter and VUV reflectance/transmittance. The in-space measurements will be augmented with extensive pre- and post-flight sample measurements to determine other optical, mechanical, electrical, chemical or surface effects of space exposure. Environmental monitors will provide the amount and time history of the sample exposure to solar irradiation, atomic oxygen and molecular contamination.

  9. Optical properties monitor: Experiment definition phase

    NASA Technical Reports Server (NTRS)

    Wilkes, Donald R.; Bennett, Jean M.; Hummer, Leigh L.; Chipman, Russell A.; Hadaway, James B.; Pezzaniti, Larry

    1989-01-01

    The stability of materials used in the space environment will continue to be a limiting technology for space missions. The Optical Properties Monitor (OPM) Experiment provides a comprehensive space research program to study the effects of the space environment-both natural and induced-on optical, thermal and space power materials. The OPM Experiment was selected for definition under the NASA/OAST In-Space Technology Experiment Program. The results of the OPM Definition Phase are presented. The OPM Experiment will expose selected materials to the space environment and measure the effects with in-space optical measurements. In-space measurements include total hemispherical reflectance total integrated scatter and VUV reflectance/transmittance. The in-space measurements will be augmented with extensive pre- and post-flight sample measurements to determine other optical, mechanical, electrical, chemical or surface effects of space exposure. Environmental monitors will provide the amount and time history of the sample exposure to solar irradiation, atomic oxygen and molecular contamination.

  10. Fiber-optic thermometer using temperature dependent absorption, broadband detection, and time domain referencing

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Piltch, Nancy D.

    1986-01-01

    A fiber-optic thermometer based on temperature dependent absorption in Nd(3+) doped glass is demonstrated over the 298-573 K range. A broadband detection technique allows the use of the complete spectrum of a pulse modulated light emitting diode. A fiber-optic recirculating loop is employed to construct a reference channel in the time domain by generating a train of pulses from one initial pulse. A theoretical model is developed, and experimental data are shown to compare well with the theory. Possible sources of error and instability are identified, and ways to enhance the performance of the system are proposed.

  11. Optical absorption enhancement in slanted silicon nanocone hole arrays for solar photovoltaics

    NASA Astrophysics Data System (ADS)

    Zhang, Shu-Yuan; Liu, Wen; Li, Zhao-Feng; Liu, Min; Liu, Yu-Sheng; Wang, Xiao-Dong; Yang, Fu-Hua

    2016-10-01

    We investigate slanted silicon nanocone hole arrays as light absorbing structures for solar photovoltaics via simulation. With only 1-μm equivalent thickness, a maximum short-circuit current density of 34.9 mA/cm2 is obtained. Moreover, by adding an Ag mirror under the whole structure, a short-circuit current density of 37.9 mA/cm2 is attained. It is understood that the optical absorption enhancement mainly results from three aspects. First, the silicon nanocone holes provide a highly efficient antireflection effect. Second, after breaking the geometric symmetry, the slanted silicon nanocone hole supports more resonant absorption modes than vertical structures. Third, the Fabry-Perot resonance enhances the light absorption after adding an Ag mirror. Project supported by the National Natural Science Foundation of China (Grant Nos. 61274066, 61474115, and 61504138) and the National High Technology Research and Development Program of China (Grant No. 2014AA032602).

  12. Spectrum sensing of trace C(2)H(2) detection in differential optical absorption spectroscopy technique.

    PubMed

    Chen, Xi; Dong, Xiaopeng

    2014-09-10

    An improved algorithm for trace C(2)H(2) detection is presented in this paper. The trace concentration is accurately calculated by focusing on the absorption spectrum from the frequency domain perspective. The advantage of the absorption spectroscopy frequency domain algorithm is its anti-interference capability. First, the influence of the background noise on the minimum detectable concentration is greatly reduced. Second, the time-consuming preprocess of spectra calibration in the differential optical absorption spectroscopy technique is skipped. Experimental results showed the detection limit of 50 ppm is achieved at a lightpath length of 0.2 m. This algorithm can be used in real-time spectrum analysis with high accuracy.

  13. Optical absorption of dilute nitride alloys using self-consistent Green’s function method

    PubMed Central

    2014-01-01

    We have calculated the optical absorption for InGaNAs and GaNSb using the band anticrossing (BAC) model and a self-consistent Green’s function (SCGF) method. In the BAC model, we include the interaction of isolated and pair N levels with the host matrix conduction and valence bands. In the SCGF approach, we include a full distribution of N states, with non-parabolic conduction and light-hole bands, and parabolic heavy-hole and spin-split-off bands. The comparison with experiments shows that the first model accounts for many features of the absorption spectrum in InGaNAs; including the full distribution of N states improves this agreement. Our calculated absorption spectra for GaNSb alloys predict the band edges correctly but show more features than are seen experimentally. This suggests the presence of more disorder in GaNSb alloys in comparison with InGaNAs. PMID:24475947

  14. Optical absorption and emission characterization of P3HT: graphene composite for its prospective photovoltaic application

    NASA Astrophysics Data System (ADS)

    Singh, Joginder; Prasad, Neetu; Nirwal, Varun Singh; Gautam, Khyati; Peta, Koteswara Rao; Bhatnagar, P. K.

    2016-05-01

    In the present work, regioregular P3HT (Poly (3-hexylthiophene-2, 5-diyl) was blended with graphene nanopowder and the optical spectroscopic characterization of the composite has been performed. It was observed that at low concentration of graphene (up to 0.1 wt %) there is no significant variation in absorption intensity or wavelength range. But at higher concentration (> 0.1 wt %) the absorption intensity starts reducing. Whereas, the photoluminescence of the composite solution quenches as we increase the concentration of graphene. It reveals that charge recombination decreases with increase in concentration (0.05 to 0.5 wt %) of graphene. Therefore 0.1 wt % seems to be the optimized concentration of graphene in the composite for which appropriate quenching of PL was observed without any significant reduction in absorption of photons. Thus maximum efficiency in P3HT: graphene composite photovoltaic cell is expected for 0.1 wt % of graphene concentration in our typical case.

  15. Optical absorption and radiative heat transport in olivine at high temperature

    NASA Technical Reports Server (NTRS)

    Shankland, T. J.; Nitsan, U.; Duba, A. G.

    1979-01-01

    Results are presented of measurements of the optical absorption spectra (300-8000 nm) of olivine as a function of temperature (300-1700 K) under conditions of controlled and known oxygen fugacity within the stability field of the samples. The absorption spectra are used to calculate the temperature-dependent radiative transfer coefficient of olivine and to numerically study the accuracy of the method. The present absorption measurements in olivine under oxidizing conditions known to be within the olivine stability field indicate that the effective radiative conductivity K(R) is lower than that obtained in previous studies under different experimental conditions. The lower value of K(R) makes it more likely that some of the earth's internal heat is removed by convection and less likely that thermal models involving conduction and radiation alone will satisfactorily explain thermal conditions in the earth's mantle.

  16. Quantitative photoacoustic tomography by stochastic search: direct recovery of the optical absorption field.

    PubMed

    Venugopal, Mamatha; van Es, Peter; Manohar, Srirang; Roy, Debasish; Vasu, Ram Mohan

    2016-09-15

    We present, perhaps for the first time, a stochastic search algorithm in quantitative photoacoustic tomography (QPAT) for a one-step recovery of the optical absorption map from time-resolved photoacoustic signals. Such a direct recovery is free of the numerical inaccuracies inherent in conventional two-step approaches that depend on an accurate estimation of the absorbed energy distribution. The absorption profile parameterized as a vector stochastic process is additively updated over time recursions so as to drive the measurement-prediction misfit to a zero-mean white noise. The derivative-free additive update is a welcome departure from the conventional gradient-based methods requiring evaluation of Jacobians at every recursion. The quantitative accuracy of the recovered absorption map from both numerical and experimental data is good with an overall error of less than 10%.

  17. Magnetopolaron effects on the optical absorptions in a parabolic quantum dot

    NASA Astrophysics Data System (ADS)

    Shihua, Chen

    2016-09-01

    We investigate the influence of magnetic field on the linear and nonlinear optical absorptions in a parabolic quantumdot(QD) through electron—LO-phonon interaction by using the Lee-Low-Pines-Huybrecht variational calculation for all coupling strengths. We apply our calculations to GaAs which is a good candidate in III–V group semiconductors. We find that all the absorption spectra are strongly affected by the electron—LO-phonon interaction, the applied magnetic field, and the Coulomb binding potential. Furthermore, due to the Zeeman splitting, the response of all the absorption values in transition (+1→0) and (‑1→0) closely depends on the magnetic field increasing.

  18. Quantitative photoacoustic tomography by stochastic search: direct recovery of the optical absorption field.

    PubMed

    Venugopal, Mamatha; van Es, Peter; Manohar, Srirang; Roy, Debasish; Vasu, Ram Mohan

    2016-09-15

    We present, perhaps for the first time, a stochastic search algorithm in quantitative photoacoustic tomography (QPAT) for a one-step recovery of the optical absorption map from time-resolved photoacoustic signals. Such a direct recovery is free of the numerical inaccuracies inherent in conventional two-step approaches that depend on an accurate estimation of the absorbed energy distribution. The absorption profile parameterized as a vector stochastic process is additively updated over time recursions so as to drive the measurement-prediction misfit to a zero-mean white noise. The derivative-free additive update is a welcome departure from the conventional gradient-based methods requiring evaluation of Jacobians at every recursion. The quantitative accuracy of the recovered absorption map from both numerical and experimental data is good with an overall error of less than 10%. PMID:27628357

  19. Solar absorptance degradation of optical solar reflector radiators on the Spacenet satellites

    NASA Technical Reports Server (NTRS)

    Naegeli, Charles R.

    1992-01-01

    Telemetry data are presented for two communications hybrid satellites, Spacenet I and Spacenet II, collected to determine the long-term temperature trend and associated solar absorptance degradation of the optical solar reflectors (OSRs). A thermal model was used to calculate the thermal sensitivity of various OSR components to changes in the solar absorptance and to determine absolute values of solar absorptance. The separation of the data into sunlit and nonsunlit periods made it possible to confirm the hypothesis that degradation occurs under the catalytic activity of direct sunlight on the spacecraft contaminants. The differences found between the degradation rates for Spacenet-I and Spacenet-II satellites and between the present results and published reports on other satellites are considered to be related to variations in the volume of spacecraft contaminants.

  20. Coherent Control of the Optical Absorption in a Plasmonic Lattice Coupled to a Luminescent Layer

    NASA Astrophysics Data System (ADS)

    Pirruccio, Giuseppe; Ramezani, Mohammad; Rodriguez, Said Rahimzadeh-Kalaleh; Rivas, Jaime Gómez

    2016-03-01

    We experimentally demonstrate the coherent control, i.e., phase-dependent enhancement and suppression, of the optical absorption in an array of metallic nanoantennas covered by a thin luminescent layer. The coherent control is achieved by using two collinear, counterpropagating, and phase-controlled incident waves with wavelength matching the absorption spectrum of dye molecules coupled to the array. Symmetry arguments shed light on the relation between the relative phase of the incident waves and the excitation efficiency of the optical resonances of the system. This coherent control is associated with a phase-dependent distribution of the electromagnetic near fields in the structure which enables a significant reduction of the unwanted dissipation in the metallic structures.