Science.gov

Sample records for active optical properties

  1. Optical properties of actively controlled reflection and transmission gratings

    NASA Astrophysics Data System (ADS)

    Rodriguez, Miguel Angel

    2001-05-01

    Reflection and transmission gratings have found a wide variety of applications as optical filters and beam steering elements. In this work we have studied the optical properties of reflection and transmission gratings whose diffraction properties could be actively controlled. Two different material systems were utilized for the study. Reflection gratings in optical fibers were used and reflection and transmission gratings were fabricated holographically in a polymer dispersed liquid crystal (PDLC) material. The optical properties of refractive index-shifted gratings were studied using the fiber Bragg gratings. It was found that narrow, high transmission spikes developed inside a high reflectivity stopgap when the refractive index of a section of the grating is shifted. The refractive index-shift was achieved using the thermo- optic effect. Experimental as well as theoretical results are presented and discussed. The optical properties of electrically switchable reflection and transmission gratings fabricated in polymer dispersed liquid crystal materials were also studied. The PDLC material is electro-optic and therefore by applying an external electric field to the gratings the diffraction properties are modified. Gratings were fabricated holographically. From the study of the transmission properties of the reflection gratings we found that the reflection of the structures can be switched off by applying an external electric field and that the reflectivity is polarization insensitive for normal incidence. We also studied the diffraction properties of PDLC transmission gratings. In our analysis of the diffraction properties of these electrically- switchable liquid crystal gratings we found that it was necessary to use a generalized two-wave coupled mode theory that includes the effects of the optical anisotropy of the liquid crystal. We found that the morphology of the PDLC gratings depends on the specific PDLC mixture used to fabricate the grating.

  2. Optical Properties of Active Regions in Terahertz Quantum Cascade Lasers

    NASA Astrophysics Data System (ADS)

    Dyksik, M.; Motyka, M.; Rudno-Rudziński, W.; Sęk, G.; Misiewicz, J.; Pucicki, D.; Kosiel, K.; Sankowska, I.; Kubacka-Traczyk, J.; Bugajski, M.

    2016-07-01

    In this work, AlGaAs/GaAs superlattice, with layers' sequence and compositions imitating the active and injector regions of a quantum cascade laser designed for emission in the terahertz spectral range, was investigated. Three independent absorption-like optical spectroscopy techniques were employed in order to study the band structure of the minibands formed within the conduction band. Photoreflectance measurements provided information about interband transitions in the investigated system. Common transmission spectra revealed, in the target range of intraband transitions, mainly a number of lines associated with the phonon-related processes, including two-phonon absorption. In contrast, differential transmittance realized by means of Fourier-transform spectroscopy was utilized to probe the confined states of the conduction band. The obtained energy separation between the second and third confined electron levels, expected to be predominantly contributing to the lasing, was found to be ~9 meV. The optical spectroscopy measurements were supported by numerical calculations performed in the effective mass approximation and XRD measurements for layers' width verification. The calculated energy spacings are in a good agreement with the experimental values.

  3. Optically active substituted polyacetylene@carbon nanotube hybrids: Preparation, characterization and infrared emissivity property study

    SciTech Connect

    Bu, Xiaohai; Zhou, Yuming Zhang, Tao; Wang, Yongjuan; Zhang, Zewu; He, Man

    2014-08-15

    Optically active substituted polyacetylene@multiwalled carbon nanotubes (SPA@MWCNTs) nanohybrids were fabricated by wrapping helical SPA copolymers onto the surface of modified nanotubes through ester bonding linkage. SPA copolymer based on chiral phenylalanine and serine was pre-polymerized by a rhodium zwitterion catalyst in THF, and evidently proved to possess strong optical activity and adopt a predominately one-handed helical conformation. Various characterizations including Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) demonstrated that the SPA had been covalently grafted onto the nanotubes without destroying their original graphite structure. The wrapped SPA was found to exhibit an enhancement in thermal stability and still maintained considerable optical activity after grafting. The infrared emissivity property of the nanohybrids at 8–14 μm was investigated in addition. The results indicated that the SPA@MWCNTs hybrid matrix could possess a much lower infrared emissivity value (ε=0.707) than raw MWCNTs, which might be due to synergistic effect of the unique helical conformation of optically active SPA and strengthened interfacial interaction between the organic polymers and inorganic nanoparticles. - Graphical abstract: Optically active SPA@MWCNTs nanohybrids with low infrared emissivity. - Highlights: • Synthesis of optically active SPA copolymer derived from serine and phenylalanine. • Preparation and characterization of optically active SPA@MWCNTs nanohybrids. • Application study of the SPA@MWCNTs nanohybrids (ε=0.707) in lowering the infrared emissivity.

  4. Charge density and optical properties of multicomponent crystals containing active pharmaceutical ingredients or their analogues.

    PubMed

    Gryl, Marlena

    2015-08-01

    Active pharmaceutical ingredients (APIs), through their favourable donor/acceptor spatial distribution and synthon formation flexibility, are attractive building blocks in modern materials crystallography. The optical properties of a crystal strongly depend on two factors, i.e. the spatial distribution of molecules in the crystal structure and the electronic properties of molecular building blocks (dipole moments, polarizabilities, hyperpolarizabilities). Although the latter are easy to predict through ab initio calculations, the former are not. Only a combination of experimental and theoretical charge density studies together with prediction and measurement of optical properties enable full analysis of the obtained functional material in terms of its usefulness in practical applications. This article presents design strategies of optical materials based on selected pharmaceutical molecules. Factors that contribute to molecular recognition in the four selected polar/chiral crystal phases (derived through charge density and Hirshfeld surfaces analysis) have been determined. Theoretically predicted optical properties of the molecular/ionic building blocks as well as bulk effects have been confirmed experimentally. This research is a first step in the design of novel optical materials based on push-pull molecules and APIs.

  5. Active control of the optical properties of nanoscale coatings using 'smart' nanoparticles

    NASA Astrophysics Data System (ADS)

    Cortie, Michael B.; Barnett, Michael; Ford, Michael J.

    2007-09-01

    Coatings that can self-modulate their optical properties as a function of an external stimulus are of significant technological interest. In this regard, the possibilities for thermo- or electrochromic materials such as VO II and WO 3 are already comparatively well-known. Here, however, we explore a new kind of 'smart' coating, based on the active control of a plasmon resonance in nanoparticles. One possible system is based on the modulation of the plasmon resonance of a precious metal nanorod or nanosphere by an active dielectric shell. The active dielectric undergoes an insulator-to-metal transition on increase of temperature which modulates the plasmon resonance of the underlying precious metal nanoparticle, thereby changing the wavelength at which its optical extinction is maximum. In the case of nanorods, the absorption maximum of the longitudinal plasmon is particularly sensitive to the aspect ratio of the nanoparticle and the dielectric properties of the environment, and may be readily tuned across the visible and near-infrared portions of the spectrum. In addition, nanoparticles of certain thermochromic dielectrics, such as VO II, are expected to have a plasmon resonance of their own which can be switched on or off by control of the temperature. We consider some of the possibilities, using both the discrete dipole approximation and the exact analytical solution due to Mie to calculate the optical properties.

  6. Tailored spectroscopic and optical properties in rare earth-activated glass-ceramics planar waveguides

    NASA Astrophysics Data System (ADS)

    Ristic, Davor; Van Tran, Thi Thanh; Dieudonné, Belto; Cristina, Armellini; Berneschi, Simone; Chiappini, Andrea; Chiasera, Alessandro; Varas, Stefano; Carpentiero, Alessandro; Mazzola, Maurizio; Nunzi Conti, Gualtiero; Pelli, Stefano; Speranza, Giorgio; Feron, Patrice; Duverger Arfuso, Claire; Cibiel, Gilles; Turrell, Sylvia; Tran Ngoc, Khiem; Boulard, Brigitte; Righini, Giancarlo C.; Ferrari, Maurizio

    2013-03-01

    Glass ceramic activated by rare earth ions are nanocomposite systems that exhibit specific morphologic, structural and spectroscopic properties allowing to develop interesting new physical concepts, for instance the mechanism related to the transparency, as well as novel photonic devices based on the enhancement of the luminescence. At the state of art the fabrication techniques based on bottom-up and top-down approaches appear to be viable although a specific effort is required to achieve the necessary reliability and reproducibility of the preparation protocols. In particular, the dependence of the final product on the specific parent glass and on the employed synthesis still remain an important task of the research in material science. Glass-ceramic waveguides overcome some of the efficiency problems experienced with conventional waveguides. These two-phase materials are composed of nanocrystals embedded in an amorphous matrix. The respective volume fractions of the crystalline and amorphous phases determine the properties of the glass ceramic. They also represent a valid alternative to widely used glass hosts such as silica as an effective optical medium for light propagation and luminescence enhancement. Looking to application, the enhanced spectroscopic properties typical of glass ceramic in respect to those of the amorphous structures constitute an important point for the development of integrated optics devices, including optical amplifiers, monolithic waveguide laser, novel sensors, coating of spherical microresonators, and up and down converters for solar energy exploitation.

  7. Properties of the long-term optical activity of the prototype polar AM Herculis

    NASA Astrophysics Data System (ADS)

    Šimon, Vojtěch

    2016-12-01

    AM Her displays strong long-term activity with the high and low states. This investigation uses AAVSO optical data for a time series analysis of the long-term variations. Rapid changes of brightness (e.g. the orbital modulation) were smoothed out to emphasize the activity on super-orbital time-scale. I show that the character of this activity changed considerably on time-scales of years, which is reflected in a large evolution of the complicated histogram of the optical brightness. The high states are not the well-defined, narrow levels of brightness. I also show that AM Her displays transitions between the high and low states with the intermittently existing cycles. The longest uninterrupted series of transitions from the high to low state consists of seven episodes (about 6 yr). The existence of this series can be controlled by the lifetime of the active regions on the donor, which modulates the mass transfer rate. I show that the episodes of the high and low states accumulate in clusters, which produces an additional cycle after smoothing by the moving averages. The cycles of activity of the donor can explain this modulation. A single isolated short episode of the low state does not imply a break of this cycle. I also argue that the specific properties of star-spots and their migration caused by the differential rotation of the donor would be needed to explain the complex activity of AM Her.

  8. From tunable core-shell nanoparticles to plasmonic drawbridges: Active control of nanoparticle optical properties

    PubMed Central

    Byers, Chad P.; Zhang, Hui; Swearer, Dayne F.; Yorulmaz, Mustafa; Hoener, Benjamin S.; Huang, Da; Hoggard, Anneli; Chang, Wei-Shun; Mulvaney, Paul; Ringe, Emilie; Halas, Naomi J.; Nordlander, Peter; Link, Stephan; Landes, Christy F.

    2015-01-01

    The optical properties of metallic nanoparticles are highly sensitive to interparticle distance, giving rise to dramatic but frequently irreversible color changes. By electrochemical modification of individual nanoparticles and nanoparticle pairs, we induced equally dramatic, yet reversible, changes in their optical properties. We achieved plasmon tuning by oxidation-reduction chemistry of Ag-AgCl shells on the surfaces of both individual and strongly coupled Au nanoparticle pairs, resulting in extreme but reversible changes in scattering line shape. We demonstrated reversible formation of the charge transfer plasmon mode by switching between capacitive and conductive electronic coupling mechanisms. Dynamic single-particle spectroelectrochemistry also gave an insight into the reaction kinetics and evolution of the charge transfer plasmon mode in an electrochemically tunable structure. Our study represents a highly useful approach to the precise tuning of the morphology of narrow interparticle gaps and will be of value for controlling and activating a range of properties such as extreme plasmon modulation, nanoscopic plasmon switching, and subnanometer tunable gap applications. PMID:26665175

  9. Determining the Scattering Properties of Vertically-Structured Nepheloid Layers from the Fusion of Active and Passive Optical Sensors

    DTIC Science & Technology

    2016-06-07

    Determining the Scattering Properties of Vertically- Structured Nepheloid Layers from the Fusion of Active and Passive Optical Sensors Curtis D...and water-column inherent optical properties including, if possible, the retrieval of the vertical structure of water-column and benthic- boundary...kilometers a day, possibly providing estimates of the vertical structure of IOPs, as well as bathymetry and bottom classification, with concomitant

  10. 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.

  11. Optical properties and photocatalytic activities of tungsten oxide (WO3) with platinum co-catalyst addition

    NASA Astrophysics Data System (ADS)

    Widiyandari, Hendri; Firdaus, Iqbal; Kadarisman, Vincencius Gunawan Slamet; Purwanto, Agus

    2016-02-01

    This research reported the optical properties and photocatalytic activities of tungsten oxide with platinum co-catalyst addition (WO3/Pt) film. The platinum was deposited on the surface of WO3 particle using photo deposition method, while the film formation of WO3/Pt on the glass substrate was prepared using spray deposition method. The addition of Pt of 0, 1, 2, and 4 wt.% resulted that the energy band gap value of the films were shifted to 2.840, 2.752, 2.623 and 2.507 eV, respectively. The as-prepared films were tested for methylene blue (MB) dye photo-degradation using the LED (light emitting diode) lamp as a visible domestic source light. The enhancement of photocatalytic activity was observed after the addition of Pt as a co-catalyst. The degradation kinetics analysis of the photo-catalyst showed that the Pt addition resulted increasing of photo-catalysis reaction rate constant, k.

  12. 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.

  13. Structural and optical properties of Eu3+ activated low cost zinc soda lime silica glasses

    NASA Astrophysics Data System (ADS)

    Omar, Nur Alia Sheh; Fen, Yap Wing; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd; Samsudin, Nur Farhana

    A low cost method was employed to synthesize ZnO-SLS:xEu3+ phosphors using recyclable bottle glass as silica source. The structural and optical properties of ZnO-SLS:xEu3+ (x = 0, 1, 2, 3, 4 and 5 wt.%) glasses were determined using X-ray diffraction (XRD), Fourier transform infrared reflectance (FTIR), UV-visible (Uv-Vis) and photoluminescence (PL) spectroscopy. Structural investigation using XRD measurement had broadened the halo peak with the doping of dopants. FTIR spectra showed the glass system consists of -OH and SiO4 bands. Meanwhile, the optical measurement using UV-Vis absorption has been induced a blue shift of the electronic absorption edge. The emission peak intensity of ZnO-SLS:xEu3+ phosphors was enhanced with the progression of doping concentration and thus, revealed their potential as red emitting phosphors under 400 nm excitation.

  14. Novel silica surface charge density mediated control of the optical properties of embedded optically active materials and its application for fiber optic pH sensing at elevated temperatures.

    PubMed

    Wang, Congjun; Ohodnicki, Paul R; Su, Xin; Keller, Murphy; Brown, Thomas D; Baltrus, John P

    2015-02-14

    Silica and silica incorporated nanocomposite materials have been extensively studied for a wide range of applications. Here we demonstrate an intriguing optical effect of silica that, depending on the solution pH, amplifies or attenuates the optical absorption of a variety of embedded optically active materials with very distinct properties, such as plasmonic Au nanoparticles, non-plasmonic Pt nanoparticles, and the organic dye rhodamine B (not a pH indicator), coated on an optical fiber. Interestingly, the observed optical response to varying pH appears to follow the surface charge density of the silica matrix for all the three different optically active materials. To the best of our knowledge, this optical effect has not been previously reported and it appears universal in that it is likely that any optically active material can be incorporated into the silica matrix to respond to solution pH or surface charge density variations. A direct application of this effect is for optical pH sensing which has very attractive features that can enable minimally invasive, remote, real time and continuous distributed pH monitoring. Particularly, as demonstrated here, using highly stable metal nanoparticles embedded in an inorganic silica matrix can significantly improve the capability of pH sensing in extremely harsh environments which is of increasing importance for applications in unconventional oil and gas resource recovery, carbon sequestration, water quality monitoring, etc. Our approach opens a pathway towards possible future development of robust optical pH sensors for the most demanding environmental conditions. The newly discovered optical effect of silica also offers the potential for control of the optical properties of optically active materials for a range of other potential applications such as electrochromic devices.

  15. Active optical zoom system

    DOEpatents

    Wick, David V.

    2005-12-20

    An active optical zoom system changes the magnification (or effective focal length) of an optical imaging system by utilizing two or more active optics in a conventional optical system. The system can create relatively large changes in system magnification with very small changes in the focal lengths of individual active elements by leveraging the optical power of the conventional optical elements (e.g., passive lenses and mirrors) surrounding the active optics. The active optics serve primarily as variable focal-length lenses or mirrors, although adding other aberrations enables increased utility. The active optics can either be LC SLMs, used in a transmissive optical zoom system, or DMs, used in a reflective optical zoom system. By appropriately designing the optical system, the variable focal-length lenses or mirrors can provide the flexibility necessary to change the overall system focal length (i.e., effective focal length), and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses. The active optics can provide additional flexibility by allowing magnification to occur anywhere within the FOV of the system, not just on-axis as in a conventional system.

  16. 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.

  17. Optical properties of stanene

    NASA Astrophysics Data System (ADS)

    Pratap Chaudhary, Raghvendra; Saxena, Sumit; Shukla, Shobha

    2016-12-01

    Successful synthesis of graphene has created a runaway effect in the exploration of other similar two-dimensional materials. These materials are important as they provide large surface areas and have led to the exploration of new physical phenomena. Even though graphene has exotic electronic properties, its spin-orbit coupling is very weak. Tin, being one of the heaviest elements in this group, is expected to have enhanced spin-orbit coupling in addition to other exotic properties of graphene. Here we report optical signatures of free standing stanene obtained using UV-vis absorption spectroscopy. Raman measurements were performed on a transmission electron microscope (TEM) grid. Interlayer spacing, phonon frequencies and the imaginary part of the complex dielectric function obtained using first principles methods are in good agreement with the experimental data. Occurrence of parallel bands suggests the possibility of the presence of excitonic effects in stanene.

  18. 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

  19. Modal demultiplexing properties of tapered and nanostructured optical fibers for in vivo optogenetic control of neural activity.

    PubMed

    Pisanello, Marco; Della Patria, Andrea; Sileo, Leonardo; Sabatini, Bernardo L; De Vittorio, Massimo; Pisanello, Ferruccio

    2015-10-01

    Optogenetic approaches to manipulate neural activity have revolutionized the ability of neuroscientists to uncover the functional connectivity underlying brain function. At the same time, the increasing complexity of in vivo optogenetic experiments has increased the demand for new techniques to precisely deliver light into the brain, in particular to illuminate selected portions of the neural tissue. Tapered and nanopatterned gold-coated optical fibers were recently proposed as minimally invasive multipoint light delivery devices, allowing for site-selective optogenetic stimulation in the mammalian brain [Pisanello , Neuron82, 1245 (2014)]. Here we demonstrate that the working principle behind these devices is based on the mode-selective photonic properties of the fiber taper. Using analytical and ray tracing models we model the finite conductance of the metal coating, and show that single or multiple optical windows located at specific taper sections can outcouple only specific subsets of guided modes injected into the fiber.

  20. 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.

  1. Optical properties of flyash

    SciTech Connect

    Self, S.A.

    1989-07-01

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

  2. Optically active quantum dots

    NASA Astrophysics Data System (ADS)

    Gerard, Valerie; Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii K.

    2015-10-01

    The main goal of our research is to develop new types of technologically important optically active quantum dot (QD) based materials, study their properties and explore their biological applications. For the first time chiral II-VI QDs have been prepared by us using microwave induced heating with the racemic (Rac), D- and L-enantiomeric forms of penicillamine as stabilisers. Circular dichroism (CD) studies of these QDs have shown that D- and L-penicillamine stabilised particles produced mirror image CD spectra, while the particles prepared with a Rac mixture showed only a weak signal. It was also demonstrated that these QDs show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. These QDs have demonstrated highly specific chiral recognition of various biological species including aminoacids. The utilisation of chiral stabilisers also allowed the preparation of new water soluble white emitting CdS nano-tetrapods, which demonstrated circular dichroism in the band-edge region of the spectrum. Biological testing of chiral CdS nanotetrapods displayed a chiral bias for an uptake of the D- penicillamine stabilised nano-tetrapods by cancer cells. It is expected that this research will open new horizons in the chemistry of chiral nanomaterials and their application in nanobiotechnology, medicine and optical chemo- and bio-sensing.

  3. Structure-activity predictions of properties of organophosphorus pesticides and chemical agents important for optical detection. Master`s thesis

    SciTech Connect

    Porte, R.E.

    1995-12-01

    This thesis presents the results of an investigation for estimating various physicochemical properties of chemical warfare agents and organophosphorus pesticides. The determination of aqueous solubility, - octanol/water partition coefficients, and alkaline hydrolysis rate constants will be used in the development of a chemical sensor using fiber optic spectroscopy. These three parameters will effect the limit of detection for each compound by limiting the concentration in the detector. The parameters were estimated by linear free energy relationships and quantitative structure activity relationships using experimental data for compounds of similar chemical structure. The results of this thesis showed that the hydrophobic medium represented by 1-octanol did concentrate the OP pesticides but did not significantly concentrate CWA, CWA simulants, or CWA hydrolysis products. Correlations were evaluated for six classes of organophosphorus compounds. The limitation of this approach to predicting physicochemical parameters is not in the molecular descriptors used in the regression equations but in the availability of existing experimental data.

  4. Formation mechanism, structural characterization, optical properties and photocatalytic activity of hierarchically arranged sisal-like ZnO architectures

    NASA Astrophysics Data System (ADS)

    Xu, Fen; Du, Gao-Hui; Halasa, Matej; Su, Bao-Lian

    2006-07-01

    A simple low-temperature solution-based self-construction approach has been demonstrated for fabricating the highly uniform assembly of ZnO nanocones with much higher aspect ratio, in which a highly non-equilibrium chemical environment favors for the large-scale generation of the complex architectures mimicking the sisal-like structures. The formation mechanism has been studied at molecular level. The optical and photocatalytic properties of the as-synthesized product have been correlated with their chemical composition, morphology and structural features. These sisal-like ZnO nanocone assemblies have shown a strong UV emission with a broad blue emission band and a high photocatalytic activity in decomposition of polyaromatics, suggesting their potentials in light and field emission and environmental applications.

  5. Effect of temperature on the active properties of erbium-doped optical fibres

    SciTech Connect

    Kotov, L V; Ignat'ev, A D; Bubnov, M M; Likhachev, M E

    2016-03-31

    We have studied the effect of heating on the performance of erbium-doped fibre based devices and determined temperaturedependent absorption and emission cross sections of the erbium ion in silica glass. The results demonstrate that heating of fibres in claddingpumped high-power (∼100 W) erbium-doped fibre lasers causes no significant decrease in their efficiency. In contrast, superluminescent sources operating in the long-wavelength region (1565 – 1610 nm) are extremely sensitive to temperature changes. (fiber optics)

  6. Synthesis, structural and optical properties, ferromagnetic behaviour, cytotoxicity and NLO activity of lithium sulphate doped L-threonine

    NASA Astrophysics Data System (ADS)

    Theras, J. Elberin Mary; Kalaivani, D.; Mani, J. Arul Martin; Jayaraman, D.; Joseph, V.

    2016-09-01

    Lithium Sulphate doped L-threonine (Li2SO4-LT), a semi-organic crystal, has been synthesised and grown by slow evaporation technique at room temperature. The grown crystal was subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Li2SO4-LT crystal belongs to the orthorhombic crystal system (a=7.66 Å, b=5.11 Å, c=13.60 Å) with space group P212121. Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) study was carried out to quantify the concentration of lithium element in the grown crystal. The results show that 0.07 mol of lithium sulphate has been incorporated into the parent system. The grown material has been found to possess wide transparency in the range 240-1100 nm with lower cut-off wavelength at 240 nm. The optical band gap was calculated as 4.92 eV using optical absorption spectrum and Tauc's relation. Fourier transform infrared (FTIR) spectroscopic study was performed to identify the functional groups present in the grown crystal. The surface features of the grown crystal were analyzed using Scanning Electron Microscope (SEM) analysis. The magnetic property was studied with the help of Vibrating Sample Magnetometer (VSM). The coercivity and retentivity of the material were measured from the hysteresis curve as 550.06 G and 79.50×10-6 emu respectively. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay method was performed to understand the cytotoxicity or anticancer activity of the sample. The cell viability and cytotoxicity of the sample against MCF-7 cells were estimated as 49.41% and 50.59% respectively at a concentration of 250 μg. The second harmonic generation (SHG) efficiency was measured by the Kurtz powder technique using Nd:YAG laser and was found to be 1.46 times that of standard potassium dihydrogen phosphate (KDP).

  7. Optical properties and CCN activity of aerosols in a high-altitude Himalayan environment: Results from RAWEX-GVAX

    NASA Astrophysics Data System (ADS)

    Gogoi, Mukunda M.; Babu, S. Suresh; Jayachandran, V.; Moorthy, K. Krishna; Satheesh, S. K.; Naja, Manish; Kotamarthi, V. R.

    2015-03-01

    The seasonality and mutual dependence of aerosol optical properties and cloud condensation nuclei (CCN) activity under varying meteorological conditions at the high-altitude Nainital site (~2 km) in the Indo-Gangetic Plains were examined using nearly year-round measurements (June 2011 to March 2012) at the Atmospheric Radiation Measurement mobile facility as part of the Regional Aerosol Warming Experiment-Ganges Valley Aerosol Experiment of the Indian Space Research Organization and the U.S. Department of Energy. The results from collocated measurements provided enhanced aerosol scattering and absorption coefficients, CCN concentrations, and total condensation nuclei concentrations during the dry autumn and winter months. The CCN concentration (at a supersaturation of 0.46) was higher during the periods of high aerosol absorption (single scattering albedo (SSA) < 0.80) than during the periods of high aerosol scattering (SSA > 0.85), indicating that the aerosol composition seasonally changes and influences the CCN activity. The monthly mean CCN activation ratio (at a supersaturation of 0.46) was highest (>0.7) in late autumn (November); this finding is attributed to the contribution of biomass-burning aerosols to CCN formation at high supersaturation conditions.

  8. Photochemical and Photophysical Properties of Phthalocyanines Modified with Optically Active Alcohols.

    PubMed

    Ramos, Aline A; Nascimento, Francisco B; de Souza, Thaiza F M; Omori, Alvaro T; Manieri, Tânia M; Cerchiaro, Giselle; Ribeiro, Anderson O

    2015-07-24

    Three phthalocyanine derivatives were synthesized and characterized: one modified with a racemic mixture of 1-(4-bromophenyl)ethanol and two other macrocycles modified with each one of the enantioenriched isomers (R)-1-(4-bromophenyl)ethanol and (S)-1-(4-bromophenyl)ethanol. The compounds were characterized by 1H-NMR spectroscopy, mass spectrometry, UV-Vis absorption, and excitation and emission spectra. Additionally, partition coefficient values and the quantum yield of the generation of oxygen reactive species were determined. Interestingly, the phthalocyanine containing a (R)-1-(4-bromophenyl)ethoxy moiety showed higher quantum yield of reactive oxygen species generation than other compounds under the same conditions. In addition, the obtained fluorescence microscopy and cell viability results have shown that these phthalocyanines have different interactions with mammary MCF-7 cells. Therefore, our results indicate that the photochemical and biological properties of phthalocyanines with chiral ligands should be evaluated separately for each enantiomeric species.

  9. Determination of local optical properties of the rat barrel cortex during neural activation: Monte-Carlo approach to light propagation

    NASA Astrophysics Data System (ADS)

    Migacheva, E. V.; Chamot, S. R.; Seydoux, O.; Weber, B.; Depeursinge, C.; Marquet, P.; Magistretti, P. J.

    2010-04-01

    Spatially-spectrally-resolved reflectance measurements allow in vivo measuring the optical coefficients of absorption and scattering within the cortical tissue. This method, if applied to neural tissue during enhanced activity, could allow a straightforward monitoring of the blood oxygen saturation changes occurring in the brain cortex during hemodynamic responses. Furthermore, it may provide valuable information on possible absorption and scattering changes occurring during stimulation. The feasibility of such measurements was investigated by carrying a preliminary numerical study using a Monte-Carlo light propagation routine. Experimental parameters such as the geometry of the optical probe, baseline cortex optical coefficients retrieved from the literature and anatomical characteristics of the rat barrel cortex were used as an input for the simulations. The sensitivity of the probe to the local variations of optical coefficients was investigated with this numerical approach. Additionally, the influence of the barrel cortex dimensions and the probe positioning relatively to the activated region were studied for instrumental optimization purpose. It was found that typical variations of optical coefficients can be detected if the activated region of barrel cortex has a volume of typically 1 mm3 or larger. The decay of the probe sensitivity to changes was studied as a function of the depth of the activated region. The results showed that the best sensitivity is achieved by placing the light injection fiber of the optical probe aligned onto the center of the cylindrical barrel.

  10. Optical Properties of Snow

    DTIC Science & Technology

    1982-01-01

    basalt, and the most common volcanic ash is andesite (R. Cadle, personal communication, 1980). Both of these rocks have very similar optical proper...giving no color to the snow; but in order to mimic a given ties for short waves: mi., - I x 10-1, constant across the concentration of soot, the andesite ...refractive v.o8 0. r~soo, 02.o5 % •%•, "index is taken as that of andesite (mt = 1.47) from Pollack et 0o..o al. [1973]. The imaginary index mim (k) was

  11. 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.

  12. The optical properties of beryllium

    SciTech Connect

    Arakawa, E.T. ); Callcott, T.A.; Chang, Yun-ching Tennessee Univ., Knoxville, TN . Dept. of Physics)

    1990-02-01

    We review the published data on the optical properties of beryllium for the spectral region from 0.03 to 300 eV. In the visible and infrared spectral regions, where published data from various authors show very large variations, we have performed experiments that identify the most probable sources of error, and use this information to select the best data from published sources. The effects of surface oxide overlayers have also been studied. In the far infrared spectral region, where only normal incidence reflectance data are available, and in the extreme ultraviolet, where only transmission data are available, there is insufficient information to fully determine the optical properties at each photon energy. Between 0.06 and 26 eV, however, a normal incidence reflectance curve is fully determined. This curve has been used for a Kramers{endash}Kronig analysis to determine the optical properties in this spectral range. 10 refs., 13 figs., 3 tabs.

  13. MBiO{sub 2}Cl (M=Sr, Ba) as novel photocatalysts: Synthesis, optical property and photocatalytic activity

    SciTech Connect

    Huang, Hongwei Wang, Shuobo; Zhang, Yihe Han, Xu

    2015-02-15

    Novel quaternary photocatalysts MBiO{sub 2}Cl (M=Sr, Ba) have been successfully developed for efficient photodecomposition of RhB. Their photocatalytic mechanism was also investigated. - Highlights: • Two Bi-based compounds SrBiO{sub 2}Cl and BaBiO{sub 2}Cl were explored as photocatalysts. • They were successfully synthesized by a solid-state reaction. • RhB can be effectively photodecomposed by SrBiO{sub 2}Cl and BaBiO{sub 2}Cl under UV light. • ·OH radicals serving as active species play important roles in degradation process. - Abstract: Two Bi-based compounds SrBiO{sub 2}Cl and BaBiO{sub 2}Cl were successfully synthesized by a solid-state reaction and investigated as new photocatalysts for the first time. Their microstructures and optical properties were characterized by XRD, SEM and DRS. The band gaps of SrBiO{sub 2}Cl and BaBiO{sub 2}Cl were separately determined to be 3.52 and 3.71 eV, and their E{sub CB} and E{sub VB} were also estimated. The photocatalytic activities of the as-prepared samples were evaluated by photodecomposition of rhodamine B (RhB) in aqueous solution. The results revealed that both SrBiO{sub 2}Cl and BaBiO{sub 2}Cl can be used as effective photocatalysts under UV irradiation, and SrBiO{sub 2}Cl exhibits a higher photocatalytic activity than BaBiO{sub 2}Cl, which was also verified by the PL spectra. Terephthalic acid photoluminescence probing technique (TA-PL) demonstrated that ·OH radicals serving as active species play an important role in photooxidative degradation of RhB over SrBiO{sub 2}Cl and BaBiO{sub 2}Cl. Moreover, a larger amount of ·OH radicals generation was observed over SrBiO{sub 2}Cl, which is in agreement with its higher photocatalytic activity.

  14. Active optical zoom system.

    PubMed

    Wang, Di; Wang, Qiong-Hua; Shen, Chuan; Zhou, Xin; Liu, Chun-Mei

    2014-11-01

    In this work, we propose an active optical zoom system. The zoom module of the system is formed by a liquid lens and a spatial light modulator (SLM). By controlling the focal lengths of the liquid lens and the encoded digital lens on the SLM panel, we can change the magnification of an image without mechanical moving parts and keep the output plane stationary. The magnification can change from 1/3 to 3/2 as the focal length of the encoded lens on the SLM changes from infinity to 24 cm. The proposed active zoom system is simple and flexible, and has widespread application in optical communications, imaging systems, and displays.

  15. Actively coupled optical waveguides

    NASA Astrophysics Data System (ADS)

    Alexeeva, N. V.; Barashenkov, I. V.; Rayanov, K.; Flach, S.

    2014-01-01

    We consider light propagation through a pair of nonlinear optical waveguides with absorption, placed in a medium with power gain. The active medium boosts the in-phase component of the overlapping evanescent fields of the guides, while the nonlinearity of the guides couples it to the damped out-of-phase component creating a feedback loop. As a result, the structure exhibits stable stationary and oscillatory regimes in a wide range of gain-loss ratios. We show that the pair of actively coupled (AC) waveguides can act as a stationary or integrate-and-fire comparator sensitive to tiny differences in their input powers.

  16. 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.

  17. 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)

  18. 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

  19. Optical properties of semiconductor microcavities

    NASA Astrophysics Data System (ADS)

    Son, Joong-Kon

    Thanks to the difference in energy gap between two semiconductors and to their different indices of refraction, semiconductor heterostructures can confine electrons as well as photons. This property makes it possible to build semiconductor-based optical resonators (microcavities) with a radiation dipole (a quantum well) in its midst to investigate the coupling between the optical modes of the microcavity with the exciton modes of the quantum well. Such an interaction, besides its intrinsic interest, is relevant to vertically-emitting semiconductor lasers, based on the quantum well- microcavity system. In this thesis, we will present experimental evidence of temperature and electric-field dependent exciton-cavity coupling in GaAs-GaAlAs microcavities.

  20. 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].

  1. 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.

  2. Properties and characteristics of optical glass

    SciTech Connect

    Marker, A.J. III.

    1988-01-01

    This book contains the proceedings of SPIE on properties and characteristics of optical glass. Topics covered include IR reflectance measurement of ion-implanted silica, specifying optical materials, and impurity absorption coefficient measurements in phosphate glass melted under oxidizing conditions.

  3. Manganese-Vanadate Hybrids: Impact of Organic Ligands on Their Structures, Thermal Stabilities, Optical Properties, and Photocatalytic Activities.

    PubMed

    Luo, Lan; Zeng, Yuhan; Li, Le; Luo, Zhixiang; Smirnova, Tatyana I; Maggard, Paul A

    2015-08-03

    Manganese(II)-vanadate(V)/organic hybrids were prepared in high purity using four different N-donor organic ligands (2,6:2',2″-terpyridine = terpy, 2,2'-bipyrimidine = bpym, o-phenanthroline = o-phen, and 4,4'-bipyridine = 4,4'-bpy), and their crystalline structures, thermal stabilities, optical properties, photocatalytic activities and electronic structures were investigated as a function of the organic ligand. Hydrothermal reactions were employed that targeted a 1:2 molar ratio of Mn(II)/V(V), yielding four hybrid solids with the compositions of Mn(terpy)V2O6·H2O (I), Mn2(bpym)V4O12·0.6H2O (II), Mn(H2O)(o-phen)V2O6 (III), and Mn(4,4'-bpy)V2O6·1.16H2O (IV). The inorganic component within these hybrid compounds, that is, [MnV2O6], forms infinite chains in I and layers in II, III, and IV. In each case, the organic ligand preferentially coordinates to the Mn(II) cations within their respective structures, either as chelating and three-coordinate (mer isomer in I) or two-coordinate (cis isomers in II and III), or as bridging and two coordinate (trans isomer in IV). The terminating ligands in I (terpy) and III (o-phen) yield nonbridged "MnV2O6" chains and layers, respectively, while the bridging ligands in II (bpym) and IV (4,4'-bpy) result in three-dimensional, pillared hybrid networks. The coordination number of the ligand, that is, two- or three-coordinate, has the predominant effect on the dimensionality of the inorganic component, while the connectivity of the combined metal-oxide/organic network is determined by the chelating versus bridging ligand coordination modes. Each hybrid compound decomposes into crystalline MnV2O6 upon heating in air with specific surface areas from ∼7 m(2)/g for III to ∼41 m(2)/g for IV, depending on the extent of structural collapse as the lattice water is removed. All hybrid compounds exhibit visible-light bandgap sizes from ∼1.7 to ∼2.0 eV, decreasing with the increased dimensionality of the [MnV2O6] network in the order

  4. Particle-resolved simulation of aerosol size, composition, mixing state, and the associated optical and cloud condensation nuclei activation properties in an evolving urban plume

    SciTech Connect

    Zaveri, Rahul A.; Barnard, James C.; Easter, Richard C.; Riemer, Nicole; West, Matthew

    2010-09-11

    The recently developed particle-resolved aerosol box model PartMC-MOSAIC was used to simulate the evolution of aerosol mixing state and the associated optical and cloud condensation nuclei (CCN) activation properties in an idealized urban plume. The model explicitly resolved the size and composition of individual particles from a number of sources and tracked their evolution due to condensation/evaporation, coagulation, emission, and dilution. The ensemble black carbon (BC) specific absorption cross section increased by 40% over the course of two days as a result of BC aging by condensation and coagulation. Three- and four-fold enhancements in CCN/CN ratios were predicted to occur within 6 hours for 0.2% and 0.5% supersaturations (S), respectively. The particle-resolved results were used to evaluate the errors in the optical and CCN activation properties that would be predicted by a conventional sectional framework that assumes monodisperse, internally-mixed particles within each bin. This assumption artificially increased the ensemble BC specific absorption by 14-30% and decreased the single scattering albedo by 0.03-0.07 while the bin resolution had a negligible effect. In contrast, the errors in CCN/CN ratios were sensitive to the bin resolution, and they depended on the chosen supersaturation. For S = 0.2%, the CCN/CN ratio predicted using 100 internally-mixed bins was up to 25% higher than the particle-resolved results, while it was up to 125% higher using 10 internally-mixed bins. Errors introduced in the predicted optical and CCN properties by neglecting coagulation were also quantified.

  5. 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)

  6. A novel Bi-based oxybromide SrBiO{sub 2}Br: Synthesis, optical property and photocatalytic activity

    SciTech Connect

    He, Ying; Huang, Hongwei Zhang, Yihe Li, Xiaowei; Tian, Na; Guo, Yuxi; Luo, Yi

    2015-04-15

    Highlights: • SrBiO{sub 2}Br was first explored as a novel photocatalyst. • SrBiO{sub 2}Br has been successfully synthesized by a solid state reaction. • We systematically synthesized SrBiO{sub 2}Br in different temperature. • SrBiO{sub 2}Br calcinated at 700 °C exhibited the highest photocatalytic activity. - Abstract: A novel Bi-based photocatalyst SrBiO{sub 2}Br with layered structure was successfully synthesized via a solid state reaction method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectra (DRS). SrBiO{sub 2}Br has an indirect-transition optical band-gap of 2.58 eV. Density functional calculations revealed that conduction band (CB) were composed of the Bi 6p and Br 4s orbitals, and valence band (VB) were occupied by Br 4p and O 2p. The photodecomposition of rhodamine-B (RhB) experiments demonstrated SrBiO{sub 2}Br can be used as photocatalysts under ultraviolet (UV) light and visible light irradiation (λ > 400 nm). The results revealed that SrBiO{sub 2}Br calcinated at 700 °C exhibited the highest photocatalytic activity among the obtained SrBiO{sub 2}Br samples.

  7. DEPENDENCE OF THE OPTICAL/ULTRAVIOLET VARIABILITY ON THE EMISSION-LINE PROPERTIES AND EDDINGTON RATIO IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Ai, Y. L.; Yuan, W.; Wang, J. G.

    2010-06-10

    The dependence of the long-term optical/UV variability on the spectral and fundamental physical parameters for radio-quiet active galactic nuclei (AGNs) is investigated. The multi-epoch-repeated photometric scanning data in the Stripe-82 region of the Sloan Digital Sky Survey (SDSS) are exploited for two comparative AGN samples (mostly quasars) selected therein: a broad-line Seyfert 1 (BLS1) type sample and a narrow-line Seyfert 1 (NLS1) type AGN sample within redshifts 0.3-0.8. Their spectral parameters are derived from the SDSS spectroscopic data. It is found that on rest-frame timescales of several years the NLS1-type AGNs show systematically smaller variability compared to the BLS1-type AGNs. In fact, the variability amplitude is found to correlate, though only moderately, with the eigenvector 1 parameters, i.e., the smaller the H{beta} linewidth, the weaker the [O III] and the stronger the Fe II emission, the smaller the variability amplitude. Moreover, an interesting inverse correlation is found between the variability and the Eddington ratio, which is perhaps more fundamental. The previously known dependence of the variability on luminosity is not significant, and the dependence on black hole mass-as claimed in recent papers and also present in our data-fades out when controlling for the Eddington ratio in the correlation analysis, though these may be partly due to the limited ranges of luminosity and black hole mass of our samples. Our result strongly supports that an accretion disk is likely to play a major role in producing the optical/UV variability.

  8. Surface modification with multiphilic ligands at detectable well defined active positions of nano-object of giant wheel shaped molybdenum blue showing third-order nonlinear optical properties

    NASA Astrophysics Data System (ADS)

    Zhang, Lijuan; Li, Yuhao; Zhou, Yunshan

    2010-04-01

    The reaction of an aqueous solution of sodium molybdate with L-tyrosine in the presence of reducing agent results in the formation of a new compound of the formula of Na 8Co 3[Mo VI126 Mo V28O 462H 14(H 2O) 46(HOC 6H 4CH 2CH( NH3+)COO -) 12]·ca. 200H 2O. The compound contains nanosized ring-shaped clusters with tyrosine ligands possessing different types of functional groups (one -CO 2, one -NH3+ and one -ArOH) coordinated through the carboxylate groups at the active sites of the inner cavity. Importantly, the result demonstrates that not only active sites/areas of the cluster surface under a specified condition can be directly monitored and detected but also novel type surfaces within the cavity of a nano-structured ring-shaped cluster can be generated simultaneously. The nonlinear optical properties of the new cluster are studied using the well-known Z-scan technique at a wavelength of 532 nm with laser pulse duration of 18 ps. The results show that the new cluster exhibits interesting self-focusing nonlinear optical response with the real and imaginary parts of the third-order nonlinear optical susceptibility χ(3) being 1.069 × 10 -13(esu) and 2.529 × 10 -15(esu), respectively, which may find application in material science.

  9. Optical properties of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chen, Gugang

    This thesis addresses the optical properties of novel carbon filamentary nanomaterials: single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), and SWNTs with interior C60 molecules ("peapods"). Optical reflectance spectra of bundled SWNTs are discussed in terms of their electronic energy band structure. An Effective Medium Model for a composite material was found to provide a reasonable description of the spectra. Furthermore, we have learned from optical absorption studies of DWNTs and C60-peapods that the host tube and the encapsulant interact weakly; small shifts in interband absorption structure were observed. Resonant Raman scattering studies on SWNTs synthesized via the HiPCO process show that the "zone-folding" approximation for phonons and electrons works reasonably well, even for small diameter (d < 1 nm) tubes. The energy of optical transitions between van Hove singularities in the electronic density of states computed from the "zone-folding" model (with gamma0 = 2.9 eV) agree well with the resonant conditions for Raman scattering. Small diameter tubes were found to exhibit additional sharp Raman bands in the frequency range 500-1200 cm-1 with an, as yet, undetermined origin. The Raman spectrum of a DWNT was found to be well described by a superposition of the Raman spectra expected for inner and outer tubes, i.e., no charge transfer occurs and the weak van der Waals (vdW) interaction between tubes does not have significant impact on the phonons. A ˜7 cm-1 downshift of the small diameter, inner-tube tangential mode frequency was observed, however, but attributed to a tube wall curvature effect, rather than the vdW interaction. Finally, we studied the chemical doping of DWNTs, where the dopant (Br anions) is chemically bound to the outside of the outer tube. The doped DWNT system is a model for a cylindrical molecular capacitor. We found experimentally that 90% of the positive charge resides on the outer tube, so that most of

  10. 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.

  11. Dielectric and Optical Properties of Sputtered Thin Films.

    DTIC Science & Technology

    1984-07-01

    experimental study of the charge carrier dynamics in the active electrooptic/ photoconductive device layer, and to determine the impact of such exposure...of wavelength beyond the photoconductivity edge for nondestructive readout) via the linear electrooptic effect. Both transmissive and 0 reflective...of properties required of the active electrooptic material. These properties include photoconductivity with high quantum efficiency, optical

  12. Active Faraday optical frequency standard.

    PubMed

    Zhuang, Wei; Chen, Jingbiao

    2014-11-01

    We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 μW. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks.

  13. A theoretical study of molecular structure, optical properties and bond activation of energetic compound FOX-7 under intense electric fields

    NASA Astrophysics Data System (ADS)

    Tao, Zhiqiang; Wang, Xin; Wei, Yuan; Lv, Li; Wu, Deyin; Yang, Mingli

    2017-02-01

    Molecular structure, vibrational and electronic absorption spectra, chemical reactivity of energetic compound FOX-7, one of the most widely used explosives, were studied computationally in presence of an electrostatic field of 0.01-0.05 a.u. The Csbnd N bond, which usually triggers the decomposition of FOX-7, is shortened/elongated under a parallel/antiparallel field. The Csbnd N bond activation energy varies with the external electric field, decreasing remarkably with the field strength in regardless of the field direction. This is attributed to two aspects: the bond weakening by the field parallel to the Csbnd N bond and the stabilization effect on the transition-state structure by the field antiparallel to the bond. The variations in the structure and property of FOX-7 under the electric fields were further analyzed with its distributional polarizability, which is dependent on the charge transfer characteristics through the Csbnd N bond.

  14. Conformational, spectroscopic and nonlinear optical properties of biologically active N,N-dimethyltryptamine molecule: A theoretical study

    NASA Astrophysics Data System (ADS)

    Öner, Nazmiye; Tamer, Ömer; Avcı, Davut; Atalay, Yusuf

    2014-12-01

    The effective psychoactive properties of N,N-dimethyltryptamine (DMT) known as the near-death molecule have encouraged the imagination of many research disciplines for several decades. Although there is no theoretical study, a number of paper composed by experimental techniques have been reported for DMT molecule. In this study, the molecular modeling of DMT was carried out using B3LYP and HSEh1PBE levels of density functional theory (DFT). Our calculations showed that the energy gap between HOMO and LUMO is low, demonstrating that DMT is a biologically active molecule. Large hyperconjugation interaction energies imply that molecular charge transfer occurs in DMT. Moreover, NLO analysis indicates that DMT can be used an effective NLO material.

  15. Conformational, spectroscopic and nonlinear optical properties of biologically active N,N-dimethyltryptamine molecule: a theoretical study.

    PubMed

    Öner, Nazmiye; Tamer, Ömer; Avcı, Davut; Atalay, Yusuf

    2014-12-10

    The effective psychoactive properties of N,N-dimethyltryptamine (DMT) known as the near-death molecule have encouraged the imagination of many research disciplines for several decades. Although there is no theoretical study, a number of paper composed by experimental techniques have been reported for DMT molecule. In this study, the molecular modeling of DMT was carried out using B3LYP and HSEh1PBE levels of density functional theory (DFT). Our calculations showed that the energy gap between HOMO and LUMO is low, demonstrating that DMT is a biologically active molecule. Large hyperconjugation interaction energies imply that molecular charge transfer occurs in DMT. Moreover, NLO analysis indicates that DMT can be used an effective NLO material.

  16. Optical properties of relativistic plasma mirrors

    PubMed Central

    Vincenti, H.; Monchocé, S.; Kahaly, S.; Bonnaud, G.; Martin, Ph.; Quéré, F.

    2014-01-01

    The advent of ultrahigh-power femtosecond lasers creates a need for an entirely new class of optical components based on plasmas. The most promising of these are known as plasma mirrors, formed when an intense femtosecond laser ionizes a solid surface. These mirrors specularly reflect the main part of a laser pulse and can be used as active optical elements to manipulate its temporal and spatial properties. Unfortunately, the considerable pressures exerted by the laser can deform the mirror surface, unfavourably affecting the reflected beam and complicating, or even preventing, the use of plasma mirrors at ultrahigh intensities. Here we derive a simple analytical model of the basic physics involved in laser-induced deformation of a plasma mirror. We validate this model numerically and experimentally, and use it to show how such deformation might be mitigated by appropriate control of the laser phase. PMID:24614748

  17. Optical properties of relativistic plasma mirrors.

    PubMed

    Vincenti, H; Monchocé, S; Kahaly, S; Bonnaud, G; Martin, Ph; Quéré, F

    2014-03-11

    The advent of ultrahigh-power femtosecond lasers creates a need for an entirely new class of optical components based on plasmas. The most promising of these are known as plasma mirrors, formed when an intense femtosecond laser ionizes a solid surface. These mirrors specularly reflect the main part of a laser pulse and can be used as active optical elements to manipulate its temporal and spatial properties. Unfortunately, the considerable pressures exerted by the laser can deform the mirror surface, unfavourably affecting the reflected beam and complicating, or even preventing, the use of plasma mirrors at ultrahigh intensities. Here we derive a simple analytical model of the basic physics involved in laser-induced deformation of a plasma mirror. We validate this model numerically and experimentally, and use it to show how such deformation might be mitigated by appropriate control of the laser phase.

  18. Optical Properties of Non-Crystalline Semiconductors.

    DTIC Science & Technology

    1984-01-01

    Instruments, 1974, unpublished. 42. de Neufville, J.P., Photostructural transformations in amorphous solids, 0 in Optical Properties of Solids --New...semiconductors, in Optical Properties of Solids , Nudelman, S., and Mitra, S.S., eds., Plenum, N.Y., 1969, 123. 52. Cody, G.D., Brooks, B.G., and

  19. Role of nickel doping on structural, optical, magnetic properties and antibacterial activity of ZnO nanoparticles

    SciTech Connect

    Vijayaprasath, G.; Murugan, R.; Palanisamy, S.; Prabhu, N.M.; Mahalingam, T.; Hayakawa, Y.; Ravi, G.

    2016-04-15

    Highlights: • The XRD analyses revealed that the synthesizes nickel doped ZnO (Zn{sub 1−x}Ni{sub x}O, x = 0.0, 0.03, 0.06 and 0.09) nanostructures have hexagonal wurtzite structure. • The photoluminescence measurements revealed that the broad emission was composed of different bands due to zinc and oxygen vacancies. • X-ray photoelectron spectroscopy (XPS) confirmed the Ni incorporation in ZnO lattice as Ni{sup 2+} ions. • Room temperature ferromagnetism was observed due to the oxygen vacancies and zinc interstitials are the main reasons for ferromagnetism in Ni doped ZnO NPs. - Abstract: Zn{sub 1−x}Ni{sub x}O nanoparticles were synthesized by co-precipitation method. The crystallite sizes of the synthesized samples found to decrease from 38 to 26 nm with increase in nickel concentration. FTIR spectra confirmed the presence of Zn−O stretching bands at 577, 573, 569 and 565 cm{sup −1} in the respective ZnO NPs. Optical absorption spectra revealed the red shifted and estimated band gap is found to decrease with increase of Ni doping concentration. The PL spectra of all the samples exhibited a broad emission at 390 nm in the visible range. The carriers (donors) bounded on the Ni sites were observed from the micro Raman spectroscopic studies. Pure and Ni doped ZnO NPs showed significant changes in the M–H loop, especially the diamagnetic behavior changed into ferromagnetic nature for Ni doped samples. The antiferromagnetic super-exchange interactions between Ni{sup 2+} ions is increased in higher Ni doped ZnO NPs and also their antibacterial activity has been studied.

  20. A new multicomponent salt of imidazole and tetrabromoterepthalic acid: Structural, optical, thermal, electrical transport properties and antibacterial activity along with Hirshfeld surface analysis

    NASA Astrophysics Data System (ADS)

    Dey, Sanjoy Kumar; Saha, Rajat; Singha, Soumen; Biswas, Susobhan; Layek, Animesh; Middya, Somnath; Ray, Partha Pratim; Bandhyopadhyay, Debasis; Kumar, Sanjay

    2015-06-01

    Herein, we report the structural, optical, thermal and electrical transport properties of a new multicomponent salt (TBTA2-)·2(IM+)·(water) [TBTA-IM] of tetrabromoterepthalic acid (TBTA) with imidazole (IM). The crystal structure of TBTA-IM is determined by both the single crystal and powder X-ray diffraction techniques. The structural analysis has revealed that the supramolecular charge assisted O-⋯Hsbnd N+ hydrogen bonding and Br⋯π interactions play the most vital role in formation of this multicomponent supramolecular assembly. The Hirshfeld surface analysis has been carried out to investigate supramolecular interactions and associated 2D fingerprint plots reveal the relative contribution of these interactions in the crystal structure quantitatively. According to theoretical analysis the HOMO-LUMO energy gap of the salt is 2.92 eV. The salt has been characterized by IR, UV-vis and photoluminescence spectroscopic studies. It shows direct optical transition with band gaps of 4.1 eV, which indicates that the salt is insulating in nature. The photoluminescence spectrum of the salt is significantly different from that of TBTA. Further, a comparative study on the antibacterial activity of the salt with respect to imidazole, Gatifloxacin and Ciprofloxacin has been performed. Moreover, the current-voltage (I-V) characteristic of ITO/TBTA-IM/Al sandwich structure exhibits good rectifying property and the electron tunneling process governs the electrical transport mechanism of the device.

  1. 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.

  2. γ irradiation induced effects on bismuth active centres and related photoluminescence properties of Bi/Er co-doped optical fibres

    NASA Astrophysics Data System (ADS)

    Sporea, D.; Mihai, L.; Neguţ, D.; Luo, Yanhua; Yan, Binbin; Ding, Mingjie; Wei, Shuen; Peng, Gang-Ding

    2016-07-01

    We investigate the effects of γ irradiation on bismuth active centres (BACs) and related photoluminescence properties of bismuth/erbium co-doped silica fibre (BEDF), [Si] ~28, [Ge] ~1.60, [Al] ~0.10, [Er] ~ <0.10 and [Bi] ~0.10 atom%, fabricated by in-situ solution doping and Modified Chemical Vapor Deposition (MCVD). The samples were irradiated at 1 kGy, 5 kGy, 15 kGy, 30 kGy and 50 kGy doses, and dose rate of 5.5 kGy/h, at room temperature. The optical properties of BEDF samples are tested before and after γ irradiation. We found that high dose γ irradiation could significantly influence the formation and composition of BACs and their photoluminescence performance, as important changes in absorption and emission properties associated with the 830 nm pump produces the direct evidence of γ irradiation effects on BAC-Si. We notice that the saturable to unsaturable absorption ratio at pump wavelength could be increased with high dose γ irradiation, indicating that emission and pump efficiency could be increased by γ irradiation. Our experimental results also reveal good radiation survivability of the BEDF under low and moderate γ irradiation. Our investigation suggests the existence of irradiation related processing available for tailoring the photoluminescence properties and performance of bismuth doped/co-doped fibres.

  3. γ irradiation induced effects on bismuth active centres and related photoluminescence properties of Bi/Er co-doped optical fibres

    PubMed Central

    Sporea, D.; Mihai, L.; Neguţ, D.; Luo, Yanhua; Yan, Binbin; Ding, Mingjie; Wei, Shuen; Peng, Gang-Ding

    2016-01-01

    We investigate the effects of γ irradiation on bismuth active centres (BACs) and related photoluminescence properties of bismuth/erbium co-doped silica fibre (BEDF), [Si] ~28, [Ge] ~1.60, [Al] ~0.10, [Er] ~ <0.10 and [Bi] ~0.10 atom%, fabricated by in-situ solution doping and Modified Chemical Vapor Deposition (MCVD). The samples were irradiated at 1 kGy, 5 kGy, 15 kGy, 30 kGy and 50 kGy doses, and dose rate of 5.5 kGy/h, at room temperature. The optical properties of BEDF samples are tested before and after γ irradiation. We found that high dose γ irradiation could significantly influence the formation and composition of BACs and their photoluminescence performance, as important changes in absorption and emission properties associated with the 830 nm pump produces the direct evidence of γ irradiation effects on BAC-Si. We notice that the saturable to unsaturable absorption ratio at pump wavelength could be increased with high dose γ irradiation, indicating that emission and pump efficiency could be increased by γ irradiation. Our experimental results also reveal good radiation survivability of the BEDF under low and moderate γ irradiation. Our investigation suggests the existence of irradiation related processing available for tailoring the photoluminescence properties and performance of bismuth doped/co-doped fibres. PMID:27440386

  4. BOREAS TE-10 Leaf Optical Properties

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Chan, Stephen S.; Middleton, Elizabeth

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-10 (Terrestrial Ecology) team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, gas exchange, oxygen evolution, and biochemical properties of boreal vegetation. This data set describes the spectral optical properties (reflectance and transmittance) of boreal forest conifers and broadleaf tree leaves as measured with a Spectron Engineering SE590 spectroradiometer at the Southern Study Area Old Black Spruce (SSA OBS), Old Jack Pine (OJP), Young Jack Pine (YJP), Old Aspen (OA), Old Aspen Auxiliary (OA-AUX), Young Aspen Auxiliary (YA-AUX), and Young Aspen (YA) sites. The data were collected during the growing seasons of 1994 and 1996 and are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  5. Properties of long-term optical variability of active galactic nuclei with double-peaked broad low-ionization emission lines

    NASA Astrophysics Data System (ADS)

    Zhang, Xue-Guang; Feng, Long-Long

    2017-01-01

    In this paper, we study properties of the long-term optical variability of a large sample of 106 Sloan Digital Sky Survey (SDSS) spectroscopically confirmed active galactic nuclei (AGN) with double-peaked broad low-ionization emission lines (double-peaked emitters). The long-term optical light curves over 8 yr are collected from the Catalina Sky Surveys Data Release 2, and the Damped Random Walk (DRW) process is applied to describe the long-term variability of the double-peaked emitters. Meanwhile, the same DRW process is applied to long-term optical light curves of more than 7000 spectroscopically confirmed normal quasars in the SDSS Stripe82 Database. Then, we can find that the DRW process determined rest-frame intrinsic variability time-scales ln (τ /d) are about 5.8 and about 4.8 for the double-peaked emitters and for the normal quasars, respectively. The statistically longer intrinsic variability time-scales can be confirmed in the double-peaked emitters, after considerations of necessary effects, such as the effects from different distributions of redshift, black hole mass, and accretion rate between the double-peaked emitters and the normal quasars. Moreover, a radial dependence of the accretion rate dot{m}R ∝ R^β with larger values of β could be an acceptable interpretation of the longer intrinsic variability time-scales in the double-peaked emitters. Therefore, there are different intrinsic properties of emission regions between the double-peaked emitters and the normal quasars. The double-peaked emitters can be well treated as an unique subclass of AGN.

  6. In situ Fabrication of α-Bi2O3/(BiO)2CO3 Nanoplate Heterojunctions with Tunable Optical Property and Photocatalytic Activity

    PubMed Central

    Huang, Yu; Wang, Wei; Zhang, Qian; Cao, Jun-ji; Huang, Ru-jin; Ho, Wingkei; Lee, Shun Cheng

    2016-01-01

    Exploring the full potential use of heterojunction photocatalysts containing bismuth has attracted considerable interest in recent years. Fabrication of well-defined heterojunction photocatalysts with precise modulation of their chemical composition is crucial for tuning their optical properties and photocatalytic activity. In this study, we fabricated nanoplate α-Bi2O3/(BiO)2CO3 heterojunctions through in situ thermal treatment of (BiO)2CO3 nanoplates synthesized using a facile hydrothermal process. Characterization results showed that the as-prepared Bi2O3/(BiO)2CO3 heterojunctions possessed distinct crystal interface and exhibited pronounced structural and optical modulation, resulting in significant improvement of their photocatalytic activity for NO removal under simulated solar light irradiation compared with pristine (BiO)2CO3. Electron spin resonance spectroscopy showed that ⋅OH radicals were the major reactive species involved in NO degradation, which is consistent with the theoretical analysis. The heterojunction formation can not only broaden the light absorption range but also improve the charge separation of photo-induced electron–hole pairs. This study is an important advancement in the development of semiconductor heterojunctions towards achieving functional photocatalysts. PMID:26997545

  7. In situ Fabrication of α-Bi2O3/(BiO)2CO3 Nanoplate Heterojunctions with Tunable Optical Property and Photocatalytic Activity

    NASA Astrophysics Data System (ADS)

    Huang, Yu; Wang, Wei; Zhang, Qian; Cao, Jun-Ji; Huang, Ru-Jin; Ho, Wingkei; Lee, Shun Cheng

    2016-03-01

    Exploring the full potential use of heterojunction photocatalysts containing bismuth has attracted considerable interest in recent years. Fabrication of well-defined heterojunction photocatalysts with precise modulation of their chemical composition is crucial for tuning their optical properties and photocatalytic activity. In this study, we fabricated nanoplate α-Bi2O3/(BiO)2CO3 heterojunctions through in situ thermal treatment of (BiO)2CO3 nanoplates synthesized using a facile hydrothermal process. Characterization results showed that the as-prepared Bi2O3/(BiO)2CO3 heterojunctions possessed distinct crystal interface and exhibited pronounced structural and optical modulation, resulting in significant improvement of their photocatalytic activity for NO removal under simulated solar light irradiation compared with pristine (BiO)2CO3. Electron spin resonance spectroscopy showed that ṡOH radicals were the major reactive species involved in NO degradation, which is consistent with the theoretical analysis. The heterojunction formation can not only broaden the light absorption range but also improve the charge separation of photo-induced electron–hole pairs. This study is an important advancement in the development of semiconductor heterojunctions towards achieving functional photocatalysts.

  8. In situ Fabrication of α-Bi2O3/(BiO)2CO3 Nanoplate Heterojunctions with Tunable Optical Property and Photocatalytic Activity.

    PubMed

    Huang, Yu; Wang, Wei; Zhang, Qian; Cao, Jun-ji; Huang, Ru-jin; Ho, Wingkei; Lee, Shun Cheng

    2016-03-21

    Exploring the full potential use of heterojunction photocatalysts containing bismuth has attracted considerable interest in recent years. Fabrication of well-defined heterojunction photocatalysts with precise modulation of their chemical composition is crucial for tuning their optical properties and photocatalytic activity. In this study, we fabricated nanoplate α-Bi2O3/(BiO)2CO3 heterojunctions through in situ thermal treatment of (BiO)2CO3 nanoplates synthesized using a facile hydrothermal process. Characterization results showed that the as-prepared Bi2O3/(BiO)2CO3 heterojunctions possessed distinct crystal interface and exhibited pronounced structural and optical modulation, resulting in significant improvement of their photocatalytic activity for NO removal under simulated solar light irradiation compared with pristine (BiO)2CO3. Electron spin resonance spectroscopy showed that ⋅OH radicals were the major reactive species involved in NO degradation, which is consistent with the theoretical analysis. The heterojunction formation can not only broaden the light absorption range but also improve the charge separation of photo-induced electron-hole pairs. This study is an important advancement in the development of semiconductor heterojunctions towards achieving functional photocatalysts.

  9. Hybrid germanium iodide perovskite semiconductors: active lone pairs, structural distortions, direct and indirect energy gaps, and strong nonlinear optical properties.

    PubMed

    Stoumpos, Constantinos C; Frazer, Laszlo; Clark, Daniel J; Kim, Yong Soo; Rhim, Sonny H; Freeman, Arthur J; Ketterson, John B; Jang, Joon I; Kanatzidis, Mercouri G

    2015-06-03

    The synthesis and properties of the hybrid organic/inorganic germanium perovskite compounds, AGeI3, are reported (A = Cs, organic cation). The systematic study of this reaction system led to the isolation of 6 new hybrid semiconductors. Using CsGeI3 (1) as the prototype compound, we have prepared methylammonium, CH3NH3GeI3 (2), formamidinium, HC(NH2)2GeI3 (3), acetamidinium, CH3C(NH2)2GeI3 (4), guanidinium, C(NH2)3GeI3 (5), trimethylammonium, (CH3)3NHGeI3 (6), and isopropylammonium, (CH3)2C(H)NH3GeI3 (7) analogues. The crystal structures of the compounds are classified based on their dimensionality with 1–4 forming 3D perovskite frameworks and 5–7 1D infinite chains. Compounds 1–7, with the exception of compounds 5 (centrosymmetric) and 7 (nonpolar acentric), crystallize in polar space groups. The 3D compounds have direct band gaps of 1.6 eV (1), 1.9 eV (2), 2.2 eV (3), and 2.5 eV (4), while the 1D compounds have indirect band gaps of 2.7 eV (5), 2.5 eV (6), and 2.8 eV (7). Herein, we report on the second harmonic generation (SHG) properties of the compounds, which display remarkably strong, type I phase-matchable SHG response with high laser-induced damage thresholds (up to ∼3 GW/cm(2)). The second-order nonlinear susceptibility, χS(2), was determined to be 125.3 ± 10.5 pm/V (1), (161.0 ± 14.5) pm/V (2), 143.0 ± 13.5 pm/V (3), and 57.2 ± 5.5 pm/V (4). First-principles density functional theory electronic structure calculations indicate that the large SHG response is attributed to the high density of states in the valence band due to sp-hybridization of the Ge and I orbitals, a consequence of the lone pair activation.

  10. Quasi-optical active antennas

    NASA Astrophysics Data System (ADS)

    Moussessian, Alina

    Quasi-optical power combiners such as quasi-optical grids provide an efficient means of combining the output power of many solid-state devices in free space. Unlike traditional power combiners no transmission lines are used, therefore, high output powers with less loss can be achieved at higher frequencies. This thesis investigates four different active antenna grids. The first investigation is into X-band High Electron Mobility Transistor (HEMT) grid amplifiers. Modelling and stability issues of these grids are discussed, and gain and power measurements are presented. A grid amplifier with a maximum efficiency of 22.5% at 10 GHz and a peak gain of 11dB is presented. The second grid is a varactor grid used as a positive feedback network for a grid amplifier to construct a tunable grid oscillator. Reflection measurements for the varactor grid show a tuning range of 1.2 GHz. The third grid is a self- complementary grid amplifier. The goal is to design a new amplifier with a unit cell structure that can be directly modelled using CAD tools. The properties of self- complementary structures are studied and used in the design of this new amplifier grid. The fourth grid is a 12 x 12 terahertz Schottky grid frequency doubler with a measured output power of 24 mW at 1 THz for 3.1-μs 500-GHz input pulses with a peak power of 47 W. A passive millimeter-wave travelling-wave antenna built on a dielectric substrate is also presented. Calculations indicate that the antenna has a gain of 15 dB with 3-dB beamwidths of 10o in the H-plane and 64o in the E-plane. Pattern measurements at 90 GHz support the theory. The antenna is expected to have an impedance in the range of 50/Omega to 80/Omega.

  11. Optical and optoelectronic properties of organic nanomaterials

    NASA Astrophysics Data System (ADS)

    Satapathi, Soumitra

    In this dissertation research, organic nanomaterials, such as semiconducting polymer nanoparticles, graphene nanosheets and organic small molecules were successfully utilized for fabrication of organic solar cells, optical sensors and for high contrast imaging of cancer cells. Semiconducting polymer nanoparticles were synthesized by a simple miniemulsion technique. These size controllable polymeric nanoparticles were proven to be able to optimize the morphologies of the bulk heterojunction solar cells and to provide fundamental insight into the evolution of the nanostructures. Highly sensitive optical sensors were fabricated using these polymeric nanoparticles for efficient detection of nitroaromatic explosives, such as 2,4 dinitrotoluene (DNT) and 2,4,6 trinitrotoluene (TNT) in aqueous medium as well as in vapor the phase. Moreover, these water dispersible and fluorescent polymer nanodots were two-photon active and could be internalized by tumor cells as demonstrated by two-photon confocal imaging. In addition to the polymer nanoparticles, the role of the graphene nanosheets in the performance enhancement of dye sensitized solar cells was also investigated. The use of organic small molecules for optical sensing of different nerve gas agents and their potential use in multiphoton imaging of cancer cells were discussed. Controlling material properties at nanoscale for optoelectronics and imaging application as discussed in this dissertation would provide new dimensions in the areas of applied physics and materials science researches.

  12. Optical properties of matrix confined species

    NASA Astrophysics Data System (ADS)

    Lezhnina, M. M.; Kynast, U. H.

    2010-11-01

    A majority of optically functional materials can be perceived as a liaison between ionic or molecular guests and a more or less rigid host. The guests exhibit an optical function, whereas the host provides suitable space, both of them synergistically complementing each other. The embracement of guests and hosts is often very intimate, as e.g. in typical phosphors, where luminescent ions even become part of the host. While the host-guest terminology usually is not applied to such marriages, the term becomes appropriate, if the host grants some degrees of spatial freedom, yet giving order and structure to its guests. Zeolites, clays and inverse opals are porous materials naturally providing hospitable cavities, channels or other compartments, and at the same time the guests are often demanded to occupy preassigned positions within these, or to structurally adapt to the interior host topology. Whereas zeolites and clays are merely patient providers of guest space, inverse opals, can actively turn the light on and off. The present article summarises and highlights recent experimental evidence, ongoing research and some envisaged merits resulting from the interaction of matrix confined luminescent ions, complexes and molecules with a focus on the optical properties of rare earth based materials.

  13. Magnetic field effects on mitochondrion-activity-related optical properties in slime mold and bone forming cells.

    PubMed

    Mizukawa, Yuri; Iwasaka, Masakazu

    2013-01-01

    In the present study, a cellular level response of Cyto-aa3 oxidation was investigated in real time under both time-varying and strong static magnetic fields of 5 T. Two kinds of cells, a slime mold, Physarum polycephalum, and bone forming cells, MC-3T3-E1, were used for the experiments. The oxidation level of the Cyto-aa3 was calculated by optical absorptions at 690 nm, 780 nm and 830 nm. The sample, fiber-optics and an additional optical fiber for light stimulation were set in a solenoidal coil or the bore of a 5-T superconducting magnet. The solenoidal coil for time-varying magnetic fields produced sinusoidal magnetic fields of 6 mT. The slime mold showed a periodic change in Cyto-aa3 oxidation, and the oxidation-reduction cycle of Cyto-aa3 was apparently changed when visible-light irradiated the slime mold. Similarly to the case with light, time-varying magnetic stimulations changed the oxidation-reduction cycle during and after the stimulation for 10 minutes. The same phenomena were observed in the MC-3T3-E1 cell assembly, although their cycle rhythm was comparatively random. Finally, magnetic field exposure of up to 5 T exhibited a distinct suppression of Cyto-aa3 oscillation in the bone forming cells. Exposure up to 5 T was repeated five times, and the change in Cyto-aa3 oxidation reproducibly occurred.

  14. Chiral THz metamaterial with tunable optical activity

    SciTech Connect

    Zhou, Jiangfeng; Taylor, Antoinette; O' Hara, John; Chowdhury, Roy; Zhao, Rongkuo; Soukoullis, Costas M

    2010-01-01

    Optical activity in chiral metamaterials is demonstrated in simulation and shows actively tunable giant polarization rotation at THz frequencies. Electric current distributions show that pure chirality is achieved by our bi-Iayer chiral metamaterial design. The chirality can be optically controlled by illumination with near-infrared light. Optical activity, occurring in chiral materials such as DNA, sugar and many other bio-molecules, is a phenomenon of great importance to many areas of science including molecular biology, analytical chemistry, optoelectronics and display applications. This phenomenon is well understood at an effective medium level as a magnetic/electric moment excited by the electric/magnetic field of the incident electromagnetic (EM) wave. Usually, natural chiral materials exhibit very weak optical activity e.g. a gyrotropic quartz crystal. The optical activity of chiral metamaterials, however, can be five orders of magnitude stronger. Chiral metamaterials are made of sub-wavelength resonators lacking symmetry planes. The asymmetry allows magnetic moments to be excited by the electric field of the incident EM wave and vice versa. Recently, chiral metamaterials have been demonstrated and lead to prospects in giant optical activity, circular dichroism, negative refraction and reversing the Casmir force. These fascinating optical properties require strong chirality, which may be designed through the microscopic structure of chiral metamaterials. However, these metamaterials have a fixed response function, defined by the geometric structuring, which limits their ability to manipulate EM waves. Active metamaterials realize dynamic control of response functions and have produced many influential applications such as ultra-fast switching devices, frequency and phase modulation and memory devices. Introducing active designs to chiral metamaterials will give additional freedom in controlling the optical activity, and therefore enable dynamic manipulation

  15. 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.

  16. Optical properties of ZnO nanostructures.

    PubMed

    Djurisić, Aleksandra B; Leung, Yu Hang

    2006-08-01

    We present a review of current research on the optical properties of ZnO nanostructures. We provide a brief introduction to different fabrication methods for various ZnO nanostructures and some general guidelines on how fabrication parameters (temperature, vapor-phase versus solution-phase deposition, etc.) affect their properties. A detailed discussion of photoluminescence, both in the UV region and in the visible spectral range, is provided. In addition, different gain (excitonic versus electron hole plasma) and feedback (random lasing versus individual nanostructures functioning as Fabry-Perot resonators) mechanisms for achieving stimulated emission are described. The factors affecting the achievement of stimulated emission are discussed, and the results of time-resolved studies of stimulated emission are summarized. Then, results of nonlinear optical studies, such as second-harmonic generation, are presented. Optical properties of doped ZnO nanostructures are also discussed, along with a concluding outlook for research into the optical properties of ZnO.

  17. Active materials for integrated optic applications

    NASA Astrophysics Data System (ADS)

    Hayden, Joseph S.; Funk, David S.; Veasey, David L.; Peters, Philip M.; Sanford, Norman A.

    1999-11-01

    The ability to engineer glass properties through the selection and adjustment of chemical composition continues to make glass a leading material in both active and passive applications. The development of optimal glass compositions for integrated optical applications requires a number of considerations that are often at variance with one another. Of critical importance is that the glass offers compatibility with standard ion exchange technologies, allowing fabrication of guided wave structures. In addition, for application as an active material, the resultant structures must be characterized by absence of inclusions and low absorption at the lasing wavelength, putting demands on both the selection and identity of the raw materials used to prepare the glass. We report on the development of an optimized glass composition for integrated optic applications that combines good laser properties with good chemical durability allowing for a wide range of chemical processing steps to be employed without substrate deterioration. In addition, care was taken during the development of this glass to insure that the selected composition was consistent with manufacturing technology for producing high optical quality glass. We present the properties of the resultant glasses, including results of detailed chemical and laser properties, for use in the design and modeling of active waveguides prepared with these glasses.

  18. 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.

  19. 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

    -style collectors. Sputtering offers considerable flexibility in coating conditions, including a wide variety of metal and dielectric targets. Coating designs range from simple two or three layer coatings to complex coatings that are purposely graded to be metal-rich at their base and oxide-rich at their surface in order to yield the desired solar selective properties. In these cermet coatings, molecular islands of metal are thought to be embedded in a three dimensional matrix of dielectric. Recent work has identified the use of custom made ion beam sputter deposition targets to produce coatings containing molecular mixtures of metal and dielectric. The targets are cylindrical and the surface consists of a gradually changing composition of metal and dielectric. Rotating the cylinder under the beam during ion beam sputter deposition yields a coating that is a molecular mixture of metal and dielectric, with the composition changing through the thickness of the coating. The optical properties of these coatings are not only dependent on their thickness and chemical composition, but are also dependent on the extent of the through thickness gradient established during deposition. This paper presents a summary of the optical properties of several thin film molecular mixtures designed as solar selective coatings. Optical performance is first identified as a function of wavelength, from the ultraviolet to the visible and infrared. Coating composition, thickness, and gradient from metal to dielectric also play an important role. Additional work for future activities is also identified.

  20. Optical properties of a heated cornstarch mixture

    NASA Astrophysics Data System (ADS)

    Vazquez-Landaverde, Pedro A.; Morales Sánchez, Eduardo; Huerta-Ruelas, Jorge A.

    2007-03-01

    In this study, the objective was to evaluate optical properties of a corn starch-water mixture as descriptors of its behavior under processing conditions. A solution of corn starch in water was prepared and heated from 25 to 85°C in a temperature-controlled optical cell. For the measurement of optical properties, a polarized laser beam modulated through a photoelastic modulator and an analyzer, was used as optical probe. It was possible to measure transmitted light, along with optical rotation. Optical measurements showed changes related to temperature dependent phenomena such as starch granule swelling and gelatinization, in the ranges 25 to 60°C, 60 to 85°C. Above 80°C transmission values were higher, due to the solution clarification caused by corn starch gelatinization. Regarding optical rotation, it was difficult to obtain reliable measurements at low temperatures due to the high turbidity of the system. However, once gel was formed at higher temperatures, optical rotation and light transmission increased. This study demonstrated that optical techniques are suitable for the study of the behavior of water-starch mixtures under processing conditions such as heating, revealing a promising future for the monitoring of such phenomena in the production line to lower costs and improve product quality.

  1. The optical properties and photocatalytic activity of CdS-ZnS-TiO{sub 2}/Graphite for isopropanol degradation under visible light irradiation

    SciTech Connect

    Rahmawati, Fitria Wulandari, Rini Murni, Irvinna M. Mudjijono

    2016-02-08

    This research prepared a photocatalyst tablet of CdS-ZnS-TiO{sub 2} on a graphite substrate. The synthesis was conducted through chemical bath deposition method. The graphite substrate used was a waste graphite rod from primary batteries. The aims of this research are studying the crystal structure, the optical properties and the photocatalytic activity of the prepared material. The photocatalytic activity was determined through isopropanol degradation. The result shows that the TiO{sub 2}/Graphite provide direct transition gap energy at 2.91 eV and an indirect transition gap energy at 3.21 eV. Deposition of CdS-ZnS changed the direct transition gap energy to 3.01 eV and the indirect transition gap energy to 3.22 eV. Isopropanol degradation with the prepared catalyst produced new peaks at 223-224 nm and 265-266 nm confirming the production of acetone. The degradation follows first order with rate constant of 2.4 × 10{sup −2} min{sup −1}.

  2. The optical properties and photocatalytic activity of CdS-ZnS-TiO2/Graphite for isopropanol degradation under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Rahmawati, Fitria; Wulandari, Rini; Murni, Irvinna M.; Mudjijono

    2016-02-01

    This research prepared a photocatalyst tablet of CdS-ZnS-TiO2 on a graphite substrate. The synthesis was conducted through chemical bath deposition method. The graphite substrate used was a waste graphite rod from primary batteries. The aims of this research are studying the crystal structure, the optical properties and the photocatalytic activity of the prepared material. The photocatalytic activity was determined through isopropanol degradation. The result shows that the TiO2/Graphite provide direct transition gap energy at 2.91 eV and an indirect transition gap energy at 3.21 eV. Deposition of CdS-ZnS changed the direct transition gap energy to 3.01 eV and the indirect transition gap energy to 3.22 eV. Isopropanol degradation with the prepared catalyst produced new peaks at 223-224 nm and 265-266 nm confirming the production of acetone. The degradation follows first order with rate constant of 2.4 × 10-2 min-1.

  3. Optical property measurement from layered biological media

    NASA Astrophysics Data System (ADS)

    Muller, Matthew R.

    1998-12-01

    Near infrared (NIR) photon reflectance spectroscopy is applied to measurement of blood concentration and its oxygen saturation within biological tissue. The measurement relies upon the changes in photon absorption of hemoglobin in the tissue as changes occur in the hemoglobin concentration and oxygen content. In the present study, NIR light is introduced at the skin surface and the optical properties (absorption and scattering) within the underlying tissue are determined from the resulting surface reflectance. Typically the tissue is modeled as a homogeneous mixture of bloodless tissue and blood, and the model incorporates the physical relationship between the surface reflectance and the optical properties of the tissue. The skin and underlying tissue, although heterogeneous, have a characteristic layered structure. These layers can be differentiated optically. The modeling and the inverse problem of measuring the optical properties in each of the tissue layers from the surface reflectance have been the subject of much attention by a number of investigators. Nonetheless, quantification of the relationship between surface reflectance and the optical properties of layered tissue has not been well understood nor well described. In the forward problem, tissue optical properties yield surface reflectance profiles (SRPs). Surface reflectance profiles, or SRPs, from diffusive media consisting of two layers are calculated using numerical solutions to the Boltzmann equation. Experimental SRPs are also measured in vitro from a test medium and in vivo from the calf of human subjects. This study provides a new approach to solving the inverse problem of determining optical properties from SRPs. To solve the inverse problem, an effective diffusion constant (Ke) is determined for the layered media. The Ke is the diffusion constant of an equivalent homogeneous medium which best fits the SRP of the layered medium. The departure from Ke of the SRP for a layered media is captured

  4. Optical and dosimetric properties of zircon.

    PubMed

    Kristianpoller, N; Weiss, D; Chen, R

    2006-01-01

    Irradiation effects were investigated in zircon crystals by methods of optical absorption and luminescence. Special attention was given to the effects of vacuum ultraviolet (VUV) radiation. The same main thermoluminescence (TL) peaks with the same thermal activation energies appeared after VUV as after X- or beta irradiation, indicating that the same traps were induced by the different irradiations. TL excitation spectra in the VUV showed an increase <220 nm and maxima near 190 and 140 nm. Excitation spectra of phototransferred TL (PTTL) and optically stimulated luminescence (OSL) were also measured. Most TL emission bands also appeared in the X-luminescence, PTTL and OSL. Dosimetric properties such as the TL radiation sensitivity, thermal stability of radiation-induced defects and TL dose dependence were also investigated. The radiation sensitivity of zircon was by an order of magnitude lower than that of TLD-100. The 355 K TL peak showed linear dose dependence only up to approximately 500 Gy and the 520 K peak up to approximately 1800 Gy.

  5. Optical Studies of Active Comets

    NASA Technical Reports Server (NTRS)

    Jewitt, David

    1998-01-01

    This grant was to support optical studies of comets close enough to the sun to be outgassing. The main focus of the observations was drawn to the two extraordinarily bright comets Hyakutake and Hale-Bopp, but other active comets were also studied in detail during the period of funding. Major findings (all fully published) under this grant include: (1) Combined optical and submillimeter observations of the comet/Centaur P/Schwassmann-Wachmann 1 were used to study the nature of mass loss from this object. The submillimeter observations show directly that the optically prominent dust coma is ejected by the sublimation of carbon monoxide. Simultaneous optical-submillimeter observations allowed us to test earlier determinations of the dust mass loss rate. (2) We modelled the rotation of cometary nuclei using time-resolved images of dust jets as the primary constraint. (3) We obtained broad-band optical images of several comets for which we subsequently attempted submillimeter observations, in order to test and update the cometary ephemerides. (4) Broad-band continuum images of a set of weakly active comets and, apparently, inactive asteroids were obtained in BVRI using the University of Hawaii 2.2-m telescope. These images were taken in support of a program to test the paradigm that many near-Earth asteroids might be dead or dormant comets. We measured coma vs. nucleus colors in active comets (finding that coma particle scattering is different from, and cannot be simply related to, nucleus color). We obtained spectroscopic observations of weakly active comets and other small bodies using the HIRES spectrograph on the Keck 10-m telescope. These observation place sensitive limits to outgassing from these bodies, aided by the high (40,000) spectral resolution of HIRES.

  6. The Optical Properties of Ion Implanted Silica

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  7. Models of the optical properties of solids

    NASA Astrophysics Data System (ADS)

    Tropf, William J.; Thomas, Michael E.

    1992-12-01

    Physically-based optical property models of solids are a convenient means of representing the complex index of refraction as a function of frequency and temperature. This modeling approach is especially convenient considering the wide spread use of personal computers and the uncomplicated mathematical form of the models. Models provide a convenient method of cataloging measurements and interpolated between measurements. Several useful models covering absorption and scattering phenomena are presented. Together, these models allow prediction of optical properties over the spectral range from microwaves to the electronic band gap. Temperature dependence of the optical properties cover a more restricted range, but some models predict optical properties from liquid helium to melting temperatures. We have developed an optical properties code incorporating the following models: the classical (one- phonon) oscillator model, our multi-phonon model, the Urbach tail and weak absorption tail models, free-carrier model, and an empirical scatter model. These models require measured parameters which are given for common materials. Comparisons of model calculations of the refractive index, the absorption coefficient, and scattering coefficient to experimental data are presented.

  8. 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.

  9. 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.

  10. 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

  11. Different ways to active optical frequency standards

    NASA Astrophysics Data System (ADS)

    Pan, Duo; Xue, Xiaobo; Zhang, Xiaogang; Chen, Jingbiao

    2016-06-01

    Active optical frequency standard, or active optical clock, is a new concept of optical frequency standard, where a weak feedback with phase coherence information in optical bad-cavity limitation is formed, and the continuous self-sustained coherent stimulated emission between two atomic transition levels with population inversion is realized. Through ten years of both theoretical and experimental exploration, the narrow linewidth and suppression of cavity pulling effect of active optical frequency standard have been initially proved. In this paper, after a simple review, we will mainly present the most recent experimental progresses of active optical frequency standards in Peking University, including 4-level cesium active optical frequency standards and active Faraday optical frequency standards. The future development of active optical frequency standards is also discussed.

  12. Motion field and optical flow: Qualitative properties

    NASA Astrophysics Data System (ADS)

    Verri, Alessandro; Poggio, Tomaso

    1986-12-01

    The optical flow, a 2-D field that can be associated with the variation of the image brightness pattern, and the 2-D motion field, the projection on the image plane of the 3-D velocity field of a moving scene, are in general different, unless very special conditions are satisfied. The optical flow, therefore, is ill suited for computing structure from motion, and for reconstructing the 3-D velocity field, problems that require an accurate estimate of the 2-D motion field. A different use of the optical flow is suggested. Stable field and the 3-D structure of the scene, and they can usually be obtained from the optical flow. The smoothed optical flow and 2-D motion field, interpreted as vector fields tangent to flows of planar dynamical systems, may have the same qualitative properties from the point of view of the theory of structural stability of dynamical systems.

  13. Optical properties of the Dead Sea

    NASA Astrophysics Data System (ADS)

    Boss, Emmanuel; Gildor, Hezi; Slade, Wayne; Sokoletsky, Leonid; Oren, Aharon; Loftin, James

    2013-04-01

    The Dead Sea, located in the rift valley between Jordan and Israel, is a hypersaline lake, resulting in unique biogeochemistry and optical properties. In the spring of 2004 we conducted two days of physical and optical measurements in the lake. Because of the significant effect of dissolved salts on the optical properties of water, our analysis required a novel processing approach to obtain dissolved and total inherent optical properties from the measurements. In addition, we show that the lake's salinity can be estimated from measurements of hyper-spectral absorption or attenuation spectra in the red and infrared parts of the spectrum, using published values of specific absorption of dissolved NaCl, despite the fact that the lake's salt chemistry is complex. In situ observations demonstrated that the lake has a two-layer structure with a warm and more turbid layer at the top 20-30 m and a clearer colder layer below. Both the particulate and dissolved absorption are well approximated by exponentially decreasing functions with the spectral slope of the particulate absorption about half that of the dissolved fraction and consistent with other aquatic environments. Both have relatively low and similar magnitudes in the blue (O(0.15 m-1)). Mean particle size was observed to increase with depth, consistent with precipitating salt crystals (observed in past campaigns) shown here to play a major role in the lake's optical properties.

  14. Optical control of antibacterial activity

    NASA Astrophysics Data System (ADS)

    Velema, Willem A.; van der Berg, Jan Pieter; Hansen, Mickel J.; Szymanski, Wiktor; Driessen, Arnold J. M.; Feringa, Ben L.

    2013-11-01

    Bacterial resistance is a major problem in the modern world, stemming in part from the build-up of antibiotics in the environment. Novel molecular approaches that enable an externally triggered increase in antibiotic activity with high spatiotemporal resolution and auto-inactivation are highly desirable. Here we report a responsive, broad-spectrum, antibacterial agent that can be temporally activated with light, whereupon it auto-inactivates on the scale of hours. The use of such a ‘smart’ antibiotic might prevent the build-up of active antimicrobial material in the environment. Reversible optical control over active drug concentration enables us to obtain pharmacodynamic information. Precisely localized control of activity is achieved, allowing the growth of bacteria to be confined to defined patterns, which has potential for the development of treatments that avoid interference with the endogenous microbial population in other parts of the organism.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  17. Optical Properties of Copper Nanoparticles

    NASA Astrophysics Data System (ADS)

    Kalenskii, A. V.; Zvekov, A. A.; Nikitin, A. P.; Anan'eva, M. V.

    2015-12-01

    Spectral dependences of the light extinction, absorption, and scattering efficiency factors of copper nanoparticles attendant to variations of their radii are calculated. A plasmon maximum is observed on the spectral dependence of the extinction efficiency factor for nanoparticle radii 10-60 nm. The maximum of the absorption efficiency factor is shifted toward red wavelengths with increasing radius of copper nanoparticles. Results are interpreted based on the special features of the spectral dependence of the complex copper refractive index. It is shown that the copper nanoparticles with radius of 35 nm placed into a transparent matrix with refractive index of 1.54 (secondary explosive pentaerythritol tetranitrate) possess a very high value of the absorption efficiency factor (2.9) of the second harmonic of a neodymium laser. Our investigations suggest that the copper nanoparticles are perspective material for application in compositions for optical detonator capsules.

  18. Optical Properties of Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Khosla, Samriti; Lal, Suman; Tripathi, S. K.; Sood, Nitin; Singh, Darshan

    2011-12-01

    The linking of liquid crystals polymer chains together into gel network fixes their topology, and melt becomes an elastic solid. These materials are called liquid crystals elastomers. Liquid crystal elastomers possess properties of soft elasticity and spontaneous shape change. The constituent molecules of LCEs are orientationally ordered and there exist a strong coupling between the orientational order and mechanical strain. In LCEs the molecules start elongate when their component rods orient and reversibly contract when the order is lost (typically by heating). So there is a change of average molecular shape from spherical to spheroidal. These unique properties make these materials suitable for future biological applications. Various research groups have studied different properties of LCEs in which optical properties are predominant. LCE has been synthesized in our laboratory. In this paper, we report on the optical behavior of this material.

  19. Optical Properties of Concentrated Dispersions.

    NASA Astrophysics Data System (ADS)

    Molloy, Peter J.

    Available from UMI in association with The British Library. Apparatus and methods have been developed to measure the diffuse transmittance T and reflectance R of multiple scattering, concentrated, colloidal dispersions. The variation of R and T with pathlength, wavelength, and concentration has been investigated for non-spherical particles in concentrated dispersions, over a range of pH and surfactant concentrations. Measurements of diffuse transmittance and reflectance required large corrections to be made for the presence of any specular interfaces i.e. windows. These corrections were minimised by developing a bifurcated fibre optic bundle reflectance method, which allowed R and T to be measured at volume fractions up to at least 0.3. Using magnetic, acoustic and shear fields to align the non-spherical kaolinite particles changes in R and T were measured at volume fractions upto 0.3. The amplitude of the changes and the relaxation of the changes induced by the applied fields were measured. The amplitude of the change was found to vary strongly with pH and surfactant concentration. For any particular face diameter platelet, the amplitude of the change followed closely the flocculation process, and was sensitive to the mode of particle-particle aggregation, e.g. face-face, or face-edge. The amount of surfactant per unit mass of kaolinite required to stabilise dispersions is found to vary with particle size and concentration. This showed that information about particle orientation can be obtained through multiple scattering systems when subjected to an aligning field. Kubelka-Munk two flux theory was used to relate R and T to the diffuse flux scattering parameter S. A simple theory was developed relating S to the size shape and orientation of the non-spherical particles, hence allowing the particle orientation to be determined for any aligning field. The insight into particle behaviour given by the optical method is superior to that given by rheology alone, which

  20. 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.

  1. Optical properties of cometary grains

    NASA Technical Reports Server (NTRS)

    Mukai, Tadashi

    1988-01-01

    An analysis of visible/near IF polarimetry of Comet Halley leads to a variation of the complex refractive index m = n - i x k of grain material with wavelength, i.e., a slight decrease of n from 1.39 at lambda = 0.37 micrometer to 1.37 at lambda = 2.2 micrometers, in constrast to an increase of k from 0.024 at lambda = 0.37 micrometer to 0.042 at lambda 2.2 micrometers. The mass distribution of grains reported by Mazets et al. from in situ measurements of Vega 2 was applied in the analysis. Combining these optical constants with those of astronomical silicate proposed by Draine, cometary silicate is presented as a candidate for cometary grains. The complex refractive index of the proposed cometary silicate is shown. Based on Mie theory, an emission coefficiency of each of the grains in computed as well as its temperature, as functions of grain radius and sun comet (grain) distance. It is found that the tentative thermal spectrum from these cometary silicates, where the mass distribution of grains reported by Mazets from Vega 2 was applied, fits very well to the IR spectrum of Comet Halley. This means that cometary silicate can explain not only the phase angle and wavelength dependences of visible/near IF polarization, but also the thermal emission.

  2. Optical properties of photochromic and thermochromic materials

    NASA Astrophysics Data System (ADS)

    Mo, Yeon-Gon

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

  3. Comparative properties of optically clear epoxy encapsulants

    NASA Astrophysics Data System (ADS)

    Edwards, Maury; Zhou, Yan

    2001-12-01

    Three epoxy systems were evaluated for physical dn optical properties. The three systems chosen for the study were selected on the basis of their optical clarity, color and chemistry. Three distinctly different chemistries were chosen, aromatic epoxy-amine cured. Aromatic epoxy- anhydride cured and cycloaliphatic epoxy-anhydride cured. All three systems remained optically clear and water-white after full cure. The three selected systems were tested for physical properties, adhesion and light transmission properties. Light transmission was measured after thermal and humidity exposure. Adhesion was measured after humidity exposure only. Both of the epoxy-anhydride systems performed well in optical properties but poorer in adhesion as compared to the epoxy-amine system. The aromatic epoxy- amine system discolored badly during thermal exposure at 100 C. Data generated from this work will be used in selecting clear encapsulating materials for photonics applications. No single system offers optimal performance in all areas. The best compromise material is the aromatic epoxy-anhydride system.

  4. Defect-related properties of optical coatings

    NASA Astrophysics Data System (ADS)

    Cheng, Xinbin; Wang, Zhanshan

    2014-02-01

    Defects in optical coatings are a major factor degrading their performance. Based on the nature of defects, we classified them into two categories: visible defects and non-visible defects. Visible defects result from the replication of substrate imperfections or particulates within the coatings by subsequent layers and can increase scattering loss, produce critical errors in extreme ultraviolet lithography, weaken mechanical and environmental stability, and reduce laser damage resistance. Non-visible defects mainly involve a decrease in laser damage resistance but typically have no influence on other properties of optical coatings. In the case of widely used HfO2/SiO2 dielectric coatings, metallic Hf nano-clusters, off-stoichiometric HfO2 nano-clusters, or areas of high-density electronic defects have been postulated as possible sources for non-visible defects. The emphasis of this review is devoted to discussing localized defect-driven laser-induced damage (LID) in optical coatings used for nanosecond-scale pulsed laser applications, but consideration is also given to other properties of optical coatings such as scattering, environmental stability, etc. The low densities and diverse properties of defects make the systematic study of LID initiating from localized defects time-consuming and very challenging. Experimental and theoretical studies of localized defect-driven LID using artificial defects whose properties can be well controlled are highlighted.

  5. Optical design and active optics methods in astronomy

    NASA Astrophysics Data System (ADS)

    Lemaitre, Gerard R.

    2013-03-01

    Optical designs for astronomy involve implementation of active optics and adaptive optics from X-ray to the infrared. Developments and results of active optics methods for telescopes, spectrographs and coronagraph planet finders are presented. The high accuracy and remarkable smoothness of surfaces generated by active optics methods also allow elaborating new optical design types with high aspheric and/or non-axisymmetric surfaces. Depending on the goal and performance requested for a deformable optical surface analytical investigations are carried out with one of the various facets of elasticity theory: small deformation thin plate theory, large deformation thin plate theory, shallow spherical shell theory, weakly conical shell theory. The resulting thickness distribution and associated bending force boundaries can be refined further with finite element analysis.

  6. Land-use/land-cover drives variation in the specific inherent optical properties of estuaries

    EPA Science Inventory

    Changes in land-use/land-cover (LULC) can impact the exports of optically and biogeochemically active constituents to estuaries. Specific inherent optical properties (SIOPs) of estuarine optically active constituents (OACs) are directly related to the composition of the OACs, and...

  7. Quantum optical properties in plasmonic systems

    NASA Astrophysics Data System (ADS)

    Ooi, C. H. Raymond

    2015-04-01

    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. 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).

  9. Optical and magneto-optical properties of plasma-magnetic metamaterials

    NASA Astrophysics Data System (ADS)

    Mehdian, H.; Mohammadzahery, Z.; Hasanbeigi, A.

    2015-08-01

    We investigate the optical and magneto-optical properties of a tunable left-handed material (LHM) consisting of an array of plasma and ferrite layers. It has been shown that the effective refraction index of a homogeneous composite in certain frequencies is negative. It can also be seen that the magnitude of extremum of the negative effective refraction index changes with frequency, external magnetic field and the electron density of plasma layer. In addition, a theoretical calculation of the faraday optical rotation effect of the proposed metamaterial is presented. From the obtained results, we find that there is a large faraday rotation angle in the frequency range where the system shows the left-handed property. Our outcomes demonstrate the potential applications of the device for tunable perfect lenses and active magneto-optic in micro-wave devices.

  10. 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

  11. Fiber-optic probe design and optical property recovery algorithm for optical biopsy of brain tissue.

    PubMed

    Cappon, Derek J; Farrell, Thomas J; Fang, Qiyin; Hayward, Joseph E

    2013-10-01

    Optical biopsy techniques offer a minimally invasive, real-time alternative to traditional biopsy and pathology during tumor resection surgery. Diffuse reflectance spectroscopy (DRS) is a commonly used technique in optical biopsy. Optical property recovery from spatially resolved DRS data allows quantification of the scattering and absorption properties of tissue. Monte Carlo simulation methods were used to evaluate a unique fiber-optic probe design for a DRS instrument to be used specifically for optical biopsy of the brain. The probe diameter was kept to a minimum to allow usage in small surgical cavities at least 1 cm in diameter. Simulations showed that the close proximity of fibers to the edge of the probe resulted in boundary effects due to reflection of photons from the surrounding air-tissue interface. A new algorithm for rapid optical property recovery was developed that accounts for this reflection and therefore overcomes these effects. The parameters of the algorithm were adjusted for use over the wide range of optical properties encountered in brain tissue, and its precision was evaluated by subjecting it to random noise. This algorithm can be adapted to work with any probe geometry to allow optical property recovery in small surgical cavities.

  12. Influence of stabilizing agent and synthesis temperature on the optical properties of silver nanoparticles as active materials in surface plasmon resonance (SPR) biosensor

    NASA Astrophysics Data System (ADS)

    Mahmudin, Lufsyi; Suharyadi, Edi; Utomo, Agung Bambang Setio; Abraha, Kamsul

    2016-04-01

    It has been successfully carried out the synthesis of colloidal silver nanoparticles by chemical reduction method. Silver nitrate (AgNO3) was used as metal precursors and trisodium citrate as the reducing agent. In the synthesis process, were varied the stabilizing agent of Polyvinyl Alcohol (PVA) and polyvinylpyrrolidone (PVP) and heating temperature. The formation of silver nanoparticles was observed visually with discoloration (yellowish). The formation and the structure of silver nanoparticles in colloidal solution were further examined through their optical properties by using a UV-Vis spectrometer. The wavelength absorption spectrum of colloidal silver nanoparticles shows that maximum surface plasmon absorption for the trisodium citrate-synthesized nanoparticles was at 429.43 nm for temperature of 90°C. The addition of the stabilizer sharpened spectrum curves and caused red shift in the maximum absorption peak of 429.01 nm and 427.09 nm for PVA and PVP respectively. Meanwhile, the addition of the synthesis temperature also sharpened the maximum surface plasmon absorption band and the red shift the maximum absorption peak of 428.79 nm and 428.58 nm for temperature of 110°C and 120°C respectively. Red shift of the maximum absorption peak indicates a smaller particle size. The maximum surface plasmon absorption band in the range of 427.09 nm to 429.43 nm indicates the presence of spherical or roughly spherical silver nanoparticles and TEM imaging confirmed this shape. TEM imaging results show that the diameter size of the silver nanoparticles range of 10 nm to 60 nm as well as the morphology (crystallites) of silver nanoparticles have spherical geometry with particle distribution which quite dispersive. The dispersibility of nanoparticles such as this could potentially be used as an active material of SPR biosensor.

  13. Restframe Optical Properties of Lyman Break Galaxies

    NASA Astrophysics Data System (ADS)

    Shapley, A. E.; Steidel, C. C.; Adelberger, K. L.; Pettini, M.; Dickinson, M. E.; Giavalisco, M.

    2000-12-01

    We review recent results from near-IR studies of z ~ 3 galaxies that have been selected by their broadband optical colors using the Lyman Break technique. Specifically, we discuss the use of near-IR imaging at J and Ks, in combination with previously obtained optical photometry, to untangle the degenerate effects of dust extinction and age on galaxy spectral energy distributions. We use the observed optical-to-infrared colors for a subsample of galaxies from our extensive high-redshift survey to constrain both the amount of dust and the ages of the observed stellar populations. Thus, we hope to learn about distribution of ages, unextincted star-formation rates, and formed stellar masses of these high-redshift galaxies. We also make use of the restframe UV luminosity function of Lyman Break galaxies, in combination with the distribution of restframe UV-to-optical colors (measured with the R-Ks color at z ~ 3), to determine the restframe optical luminosity function of Lyman Break galaxies. Finally, we describe new efforts, using near-infrared spectroscopy, to study familiar restframe optical nebular emission lines redshifted to 1.5 - 2.5 μm in z ~ 3 galaxies. The properties of these emission features should indicate the range of dynamical masses and metallicities of high redshift star-forming galaxies. We also hope to use the velocity offsets measured between restframe optical nebular lines, Lyman-α , and restframe-UV interstellar metal lines, to characterize the starburst-induced outflows present in Lyman Break galaxies, how they depend on other galaxy properties, and what their impact is on the surrounding intergalactic medium.

  14. Engineering optical properties using plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Tamma, Venkata Ananth

    Plasmonic nanostructures can be engineered to take on unusual optical properties not found in natural materials. The optical responses of plasmonic materials are functions of the structural parameters and symmetry of the nanostructures, material parameters of the nanostructure and its surroundings and the incidence angle, frequency and polarization state of light. The scattering and hence the visibility of an object could be reduced by coating it with a plasmonic material. In this thesis, presented is an optical frequency scattering cancelation device composed of a silicon nanorod coated by a plasmonic gold nanostructure. The principle of operation was theoretically analyzed using Mie theory and the device design was verified by extensive numerical simulations. The device was fabricated using a combination of nanofabrication techniques such as electron beam lithography and focused ion beam milling. The optical responses of the scattering cancelation device and a control sample of bare silicon rod were directly visualized using near-field microscopy coupled with heterodyne interferometric detection. The experimental results were analyzed and found to match very well with theoretical prediction from numerical simulations thereby validating the design principles and our implementation. Plasmonic nanostructures could be engineered to exhibit unique optical properties such as Fano resonance characterized by narrow asymmetrical lineshape. We present dynamic tuning and symmetry lowering of Fano resonances in plasmonic nanostructures fabricated on flexible substrates. The tuning of Fano resonance was achieved by application of uniaxial mechanical stress. The design of the nanostructures was facilitated by extensive numerical simulations and the symmetry lowering was analyzed using group theoretical methods. The nanostructures were fabricated using electron beam lithography and optically characterized for various mechanical stress. The experimental results were in good

  15. 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.

  16. Optical properties of {beta}-Sn films

    SciTech Connect

    Takeuchi, Katsuki; Adachi, Sadao

    2009-04-01

    Optical properties of white tin ({beta}-Sn) have been investigated using spectroscopic ellipsometry in the photon-energy range between 0.6 and 6.5 eV at room temperature. The {beta}-Sn films are deposited by vacuum evaporation on Si(001) substrates. The structural properties of the films are evaluated by x-ray diffraction and ex situ atomic force microscopy. The measured {epsilon}(E) spectra reveal distinct structures at several interband critical points in the Brillouin zone of {beta}-Sn. These spectra are analyzed on the basis of a simplified model of the interband transitions, including the free-carrier absorption between the filled and empty electronic states. Dielectric-related optical constants, such as the complex refractive index, absorption coefficient, and normal-incidence reflectivity, of bulk {beta}-Sn films are also presented.

  17. Predicting and Designing Optical Properties of Inorganic Materials

    NASA Astrophysics Data System (ADS)

    Rondinelli, James M.; Kioupakis, Emmanouil

    2015-07-01

    Modern first-principles calculations based on density functional theory and related techniques enable the predictive modeling of the linear and nonlinear optical properties of materials without adjustable or empirical parameters. Today, atomistic calculations are an indispensable tool by which to understand the interrelationship between the underlying structure and the measured optical properties and are particularly suited for the design of new materials with desirable optical responses and performance. In this article, we discuss the first-principles design methodology, and we review recent results from the literature that exemplify the predictive power of the method for numerous inorganic materials and nanostructures. We also discuss topics of active research and future opportunities that will enable the wider adoption of atomistic simulation techniques for predictive materials design.

  18. 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.

  19. 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

  20. Optical and surface properties of oxyfluoride glass

    NASA Astrophysics Data System (ADS)

    Nee, Soe-Mie F.; Johnson, Linda F.; Moran, Mark B.; Pentony, Joni M.; Daigneault, Steven M.; Tran, Danh C.; Billman, Kenneth W.; Siahatgar, Sadegh

    2000-10-01

    Using conventional materials like fused silica and sapphire for critical window components in a high-power laser system can lead to intolerable thermal distortions and optical path difference effects. A new oxyfluoride glass is being developed which has the unique property of possessing a negative thermo-optic coefficient (dn/dT) in the near- and mid-wave infrared. Specifically, the refractive index (n) of oxyfluoride glass decreases as the temperature increases. The distortions caused by thermal expansion of the glass during laser irradiation are partly offset by the negative dn/dT. This paper specifically addresses optical properties and surface finishing of oxyfluoride glass compared to fused silica. Normarski micrographs and surface profiles were measured to inspect the surface quality since smooth surfaces are essential for suppressing surface scattering and absorption. The refractive index and thermo-optic coefficient were measured using null polarimetry near the Brewster angle. Low dn/dT is required for laser windows. Transmittance spectra were measured to deduce the extinction coefficient by comparing with the transmittance calculated from the refractive index and to screen for unwanted absorption from contaminants including hydrocarbon oils, polishing residue, and water or -OH groups. Total integrated scattering was measured for both surface and bulk scattering. All measurements were done on 1.0- and 1.5-inch-diameter witness samples.

  1. Optical properties of RDX and HMX

    SciTech Connect

    Isbell, R.A.; Brewster, M.Q.

    1996-07-01

    Optical properties of RDX (cyclotrimethylene-trinitramine) and HMX (cyclotetramethylene-tetranitramine) were obtained from 2.5 to 18 {micro}m using scattering-corrected KBr pellet-FTIR transmission spectroscopy. Absorption index (k) was measured directly and refractive index (n) was deduced using dispersion theory. At 10.6 {micro}m the absorption coefficients were RDX, 2,800 cm{sup {minus}1} and HMX, 5,670 cm{sup {minus}1}.

  2. 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.

  3. 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.

  4. Preparation, characterization, and infrared emissivity property of optically active polyurethane/TiO{sub 2}/SiO{sub 2} multilayered microspheres

    SciTech Connect

    Yang Yong; Zhou Yuming; Ge Jianhua; Wang Yongjuan; Zhu Yunxia

    2011-10-15

    Optically active polyurethane/titania/silica (LPU/TiO{sub 2}/SiO{sub 2}) multilayered core-shell composite microspheres were prepared by the combination of titania deposition on the surface of silica spheres and subsequent polymer grafting. LPU/TiO{sub 2}/SiO{sub 2} was characterized by FT-IR, UV-vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), SEM and TEM, and the infrared emissivity value (8-14 {mu}m) was investigated in addition. The results indicated that titania and polyurethane had been successfully coated onto the surfaces of silica microspheres. LPU/TiO{sub 2}/SiO{sub 2} exhibited clearly multilayered core-shell construction. The infrared emissivity values reduced along with the increase of covering layers thus proved that the interfacial interactions had direct influence on the infrared emissivity. Besides, LPU/TiO{sub 2}/SiO{sub 2} multilayered microspheres based on the optically active polyurethane took advantages of the orderly secondary structure and strengthened interfacial synergistic actions. Consequently, it possessed the lowest infrared emissivity value. - Graphical Abstract: Optically active polyurethane/titania/silica (LPU/TiO{sub 2}/SiO{sub 2}) multilayered core-shell composite microspheres were prepared by the combination of titania deposition on the surface of silica spheres and subsequent polymer grafting. Highlights: > Optically active polyurethane based on tyrosine was used for the modification of nanoparticles. > LPU/TiO{sub 2}/SiO{sub 2} multilayered core-shell microspheres were prepared and characterized. > Interfacial interactions and secondary structure affected the infrared emissivity of composite.

  5. Optical properties of polyimide/silica nanocomposite

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  6. 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.

  7. 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

  8. Relation between inherent optical properties and land use and land cover across Gulf Coast estuaries

    EPA Science Inventory

    Land use and land cover (LULC) can affect the watershed exports of optically active constituents such as suspended particulate matter and colored dissolved organic matter, and in turn affect estuarine optical properties. We collected optical data from six estuaries in the northea...

  9. Nonlinear optical properties of semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Ricard, Gianpiero Banfi Vittorio Degiorgio Daniel

    1998-05-01

    This review is devoted to the description of recent experimental results concerning the nonlinear optical properties of semiconductor-doped glasses SDGs with particular emphasis on the regime in which the energy of the incident photon is smaller than the energy gap. A considerable theoretical and experimental effort has been devoted in the last 10years to the fundamental aspects of quantumconfined structures, which have properties somewhat intermediate between the bulk crystals and atoms or molecules. From this point of view, SDGs represent an easily available test system, and optical techniques have been a major diagnostic tool. Luminescence and absorption spectroscopy were extensively used to characterize the electronic states. The experiments aimed at the measurement of the real and imaginary parts of the third-order optical susceptibility of SDGs below the bandgap are described in some detail, and the results obtained with different techniques are compared. Besides the intrinsic fast nonlinearity due to bound electrons, SDGs may present a larger but much slower nonlinearity due to the free carriers generated by two-photon absorption. This implies that experiments have to be properly designed for separation of the two effects. In this article we stress the importance of a detailed structural characterization of the samples. Knowledge of the volume fraction occupied by the nanocrystals is necessary in order to derive from the experimental data the intrinsic nonlinearity and to compare it with the bulk nonlinearity. We discuss recent experiments in which the dependence of the intrinsic nonlinearity on the crystal size is derived by performing, on the samples, measurements of the real part and imaginary part of the nonlinear optical susceptibility and measurements of crystal size and volume fraction. Structural characterization is of interest also for a better understanding of the physical processes underlying the growth of crystallites in SDGs. The average size of

  10. 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.

  11. 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.

  12. Linear and nonlinear optical properties of a rotaxane molecule

    NASA Astrophysics Data System (ADS)

    Rau, Ilena; Czaplicki, Robert; Humeau, Adeline; Luc, Jerome; Sahraoui, Bouchta; Boudebs, Georges; Kajzar, François; Leigh, David A.; Berna-Canovas, Jose

    2006-09-01

    In this paper the recent results of our studies of linear and nonlinear optical properties of a selected rotaxane are presented and discussed. The studied rotaxane can be processed into good optical quality thin films by vacuum evaporation. The linear optical properties of rotaxane solutions were studied by the UV-VIS spectroscopy and the nonlinear optical properties by the picosecond degenerate four wave mixing and Z-scan methods. The results show important rotational contribution to the nonlinear index of refraction.

  13. On the optical properties of plasmonic glasses

    NASA Astrophysics Data System (ADS)

    Antosiewicz, Tomasz J.; Langhammer, Christoph; Apell, S. Peter

    2014-12-01

    We report on the optical properties of plasmonic glasses which are metal-dielectric composites composed of metallic inclusions in a host dielectric medium. The investigated structures are of quasi-random nature, described by the pair correlation function, featuring a minimum center-to-center distance between metallic inclusions and long range randomness. Plasmonic glasses exhibiting short-range order only may be fabricated using bottom-up, self-assembly methods and have been utilized in a number of applications such as plasmonic sensing or plasmon-enhanced solar harvesting, and may be also employed for certain non-linear applications. It is therefore important to quantify their properties. Using theoretical methods we investigate optical of 1D, 2D, and 3D structures composed of amorphous distributions of metallic spheres. It is shown, that the response of the constituent element, i.e. the single sphere localized surface plasmon resonance, is modified by the scattered fields of the other spheres in such a way that its peak position, peak amplitude, and full-width at half-maximum exhibit damped oscillations. The oscillation amplitude is set by the particle density and for the peak position may vary by up to 0.3 eV in the optical regime. Using a modified coupled dipole approach we calculate the effective (average) polarizability of plasmonic glasses and discuss their spectra as a function of the dimensionality, angle of incidence and polarization, and the minimum center-to-center distance. The analytical model is complemented and validated by T-Matrix calculations of the optical cross-sections of amorphous arrays of metallic spheres obtained using a modification of the Random Sequential Adsorption algorithm for lines, surfaces, and volumes.

  14. Spin multiplicity dependence of nonlinear optical properties.

    PubMed

    Jha, Prakash Chandra; Rinkevicius, Zilvinas; Agren, Hans

    2009-03-23

    Open-shell spin-restricted time-dependent density functional theory is applied to explore the spin multiplicity dependence of linear and nonlinear optical properties. An open-shell neutral conjugated system, the C(4)H(4)N radical in the doublet X(2)A(2), quartet X(4)A(2), and sextet X(6)A(1) states, is chosen as a model system to illustrate various aspects of the theory. It is found that irrespective of the exchange-correlation functional employed, the components of the polarizability alpha(-omega,omega) and first hyperpolarizability beta(-2 omega,omega,omega) show very different dependency with respect to the multiplicity, with an increasing trend for higher spin states. This is rationalized by the decrease in conjugation and stability of the system with increasing multiplicity, and by the way the interaction between unpaired electrons and the external field is shielded by remaining electrons of the molecule. The study suggests the applicability of open-shell systems for frequency-dependent nonlinear optical properties and for the possibility of spin control for such properties.

  15. Optical properties of aerosols in Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Skorov, Yu. V.; Keller, H. U.; Rodin, A. V.

    2008-04-01

    In the frame of fractal modeling of tholin aggregates we made a systematic analysis of their optical properties. Ballistic particle-cluster aggregation (BPCA) and diffusion-limited aggregation (DLA) of spherical primary particles (monomers) identical in material composition were considered. Aggregates composed of identical particles (monodisperse cluster), as well as of size-distributed particles (polydisperse cluster), were simulated. To calculate the light-scattering models, the code based on the superposition T-matrix method is used. Orientationally averaged properties of light scattering by model particles were extracted, and the normalized phase function and the degree of linear polarization were calculated as functions of scattering angle. We concluded that: (a) aggregation mechanism as well as specific internal structure of the clusters play only a minor role, and for the future it is not necessary to investigate aggregates of different types; (b) the intensity is very sensitive both to the size parameter of forming particles x and to the size parameter of the aggregates X; (c) characterization of the aggregates by the number of monomers is insufficient to retrieve physical properties of aggregates from optical measurement; and (d) it is very desirable to include into the analysis polarization data calculated for the different clusters.

  16. Measurement of optical activity of honey bee

    NASA Astrophysics Data System (ADS)

    Ortiz-Gutiérrez, Mauricio; Olivares-Pérez, Arturo; Salgado-Verduzco, Marco Antonio; Ibarra-Torres, Juan Carlos

    2016-03-01

    Optical activity of some substances, such as chiral molecules, often exhibits circular birefringence. Circular birefringence causes rotation of the vibration plane of the plane polarized light as it passes through the substance. In this work we present optical characterization of honey as function of the optical activity when it is placed in a polariscope that consists of a light source and properly arranged polarizing elements.

  17. Optical properties of cerium doped oxyfluoroborate glass.

    PubMed

    Bahadur, A; Dwivedi, Y; Rai, S B

    2013-06-01

    Cerium doped oxyfluoroborate glasses have been prepared and its spectroscopic properties have been discussed. It is found that the absorption edge shifts towards the lower energy side for the higher concentration of cerium dopant. Optical band gap for these glasses have been calculated and it is found that the number of non-bridging oxygen increases with cerium content. The emission spectra of these glasses have been recorded using UV laser radiations (266 and 355 nm) and it is observed that these glasses show bright blue emission. On the basis of excitation and emission spectra we have reported the existence of at least two different emission centers of Ce(3+)ions.

  18. Excitons and Optical Properties of {alpha} -Quartz

    SciTech Connect

    Chang, Eric K.; Rohlfing, Michael; Louie, Steven G. [Department of Physics, University of California at Berkeley, Berkeley, California 94720

    2000-09-18

    We present an ab initio study of the optical properties of {alpha} -quartz. The absorption spectrum is calculated by solving the Bethe-Salpeter equation for the interacting electron-hole system and found to be in excellent agreement with the measured spectrum up to 10 eV above the absorption threshold. We find that excitonic effects are crucial in understanding the sharp features in the absorption spectrum in this energy range. They are also crucial in the ab initio computation of the static dielectric constant, significantly enhancing its value. (c) 2000 The American Physical Society.

  19. Structural, electronic and optical properties of carbonnitride

    SciTech Connect

    Cohen, Marvin L.

    1996-01-31

    Carbon nitride was proposed as a superhard material and a structural prototype, Beta-C3N4, was examined using several theoretical models. Some reports claiming experimental verifications have been made recently. The current status of the theory and experiment is reviewed, and a detailed discussion is presented of calculations of the electronic and optical properties of this material. These calculations predict that Beta-C3N4 will have a minimum gap which is indirect at 6.4 plus or minus 0.5 eV. A discussion of the possibility of carbon nitride nanotubes is also presented.

  20. Optical properties of lithium niobate single crystals

    NASA Astrophysics Data System (ADS)

    Palatnikov, M. N.; Sidorov, N. V.; Biryukova, I. V.; Kalinnikov, V. T.; Bormanis, K.

    2005-01-01

    Studies of thermal and -irradiation effects on the optical properties in congruous lithium niobate single crystals containing Y, Mg, Gd, B, and Zn dopants including samples with double dopants Y, Mg and Gd, Mg are reported. Formation of defects at irradiation and thermal treatment of the samples is explored by electron absorption spectra. Considerable increase of absorption with the dose of -radiation is observed at 500 nm. The changes of absorption examined under different conditions are explained by creation and destruction of Nb4+ defects.

  1. Studies on optical, mechanical and transport properties of NLO active L-alanine formate single crystal grown by modified Sankaranarayanan Ramasamy (SR) method

    NASA Astrophysics Data System (ADS)

    Justin Raj, C.; Dinakaran, S.; Krishnan, S.; Milton Boaz, B.; Robert, R.; Jerome Das, S.

    2008-04-01

    Bulk single crystals of L-alanine formate of 10 mm diameter and 50 mm length have been grown with an aid of modified Sankaranarayanan-Ramasamy (SR) uniaxial crystal growth method within a period of ten days. The optical properties of the grown crystal were calculated from UV transmission spectral analysis. The second harmonic generation efficiency of the grown crystal was confirmed by Kurtz powder test. In order to determine the mechanical strength of the crystal, Vicker's microhardness test was carried along the growth plane (0 0 1). Dielectric studies reveal that both dielectric constant and dielectric loss decreases with increase in frequency. Photoconductivity study confirms the negative photoconducting nature of the crystal.

  2. Electronic and optical properties of mixed Be-chalcogenides

    NASA Astrophysics Data System (ADS)

    Khan, Imad; Ahmad, Iftikhar; Zhang, D.; Rahnamaye Aliabad, H. A.; Jalali Asadabadi, S.

    2013-02-01

    The electronic and optical properties of BeSxSe1-x, BeSxTe1-x and BeSexTe1-x, (0≤x≤1) are studied using the highly accurate modified Beck and Johnson (mBJ) potential. The binary Be-chalcogenides are wide and indirect band gap semiconductors and hence they are not efficient materials for optoelectronics. In order to modify them into optically active materials, the anion chalcogen atoms are partially replaced by other chalcogen atoms like BeSxSe1-x, BeSxTe1-x and BeSexTe1-x (0≤x≤1). The modified ternary compounds are of direct band gap nature and hence they are optically active. Some of these direct band gap materials are lattice matched with silicon and can possibly replace Si in semiconductor devices. Keeping in view the importance of these materials in optoelectronics, the optical properties of BeSxSe1-x, BeSxTe1-x and BeSexTe1-x in the full composition range are investigated. It is found that these materials are transparent in the IR, visible and near UV spectral regions. The alloys for the most of the concentrations have band gaps larger than 3 eV, so it is expected that they may be efficient materials for blue, green and UV light emitting diodes.

  3. Selectively deuterated and optically active cyclic ethers

    SciTech Connect

    Kawakami, Y.; Asai, T.; Umeyama, K.; Yamashita, Y.

    1982-08-27

    The synthesis of selectively deuterated epihalohydrins (F, Cl, Br, I) and 3,3-bis(chloromethyl)-d/sub 2/)oxetane and some observations on the stereochemistry of each transformation are reported. Further, the synthesis of optically active epihalohydrins, especially the optically active epifluorohydrin, from (S)-glycerol 1,2-acetonide ((S)-2), using mainly KX-18-CR-6 (X = F, Br, I), is reported. This is the first report on the synthesis of optically active epifluorohydrin. The direct halogenation of the presynthesized optically active epichlorohydrin with the same reagents gave the racemized products. The selectively deuterated or optically active compounds reported herein are expected to find a variety of uses in organic chemistry.

  4. Optical properties of a planar turbulent jet.

    PubMed

    Joia, I A; Perkins, R J; Uscinski, B J; Balmer, G; Jordan, D; Jakeman, E

    1995-10-20

    A planar heated air jet was constructed. Its flow properties were characterized and shown to be both reproducible and in good agreement with the results of turbulence theory. The optical properties of the jet were studied with the help of a 632.8-nm He-Ne laser beam. The random phase modulations imposed on the wave front of the beam traversing the jet were measured by interferometric means, and their spectra and variance were determined. The one-dimensional phase fluctuation spectrum obeyed a -8/3 power law as predicted by theory, whereas the phase variance (?(2)) depended on the jet temperature and was studied for values to as high as 0.4 (rad)(2)).

  5. Influence of optical material properties on the perception of liquids.

    PubMed

    van Assen, Jan Jaap R; Fleming, Roland W

    2016-12-01

    In everyday life we encounter a wide range of liquids (e.g., water, custard, toothpaste) with distinctive optical appearances and viscosities. Optical properties (e.g., color, translucency) are physically independent of viscosity, but, based on experience with real liquids, we may associate specific appearances (e.g., water, caramel) with certain viscosities. Conversely, the visual system may discount optical properties, enabling "viscosity constancy" based primarily on the liquid's shape and motion. We investigated whether optical characteristics affect the perception of viscosity and other properties of liquids. We simulated pouring liquids with viscosities ranging from water to molten glass and rendered them with nine different optical characteristics. In Experiment 1, observers (a) adjusted a match stimulus until it had the same perceived viscosity as a test stimulus with different optical properties, and (b) rated six physical properties of the test stimuli (runniness, shininess, sliminess, stickiness, warmth, wetness). We tested moving and static stimuli. In Experiment 2, observers had to associate names with every liquid in the stimulus set. We find that observers' viscosity matches correlated strongly with the true viscosities and that optical properties had almost no effect. However, some ratings of liquid properties did show substantial interactions between viscosity and optical properties. Observers associate liquid names primarily with optical cues, although some materials are associated with a specific viscosity or combination of viscosity and optics. These results suggest viscosity is inferred primarily from shape and motion cues but that optical characteristics influence recognition of specific liquids and inference of other physical properties.

  6. Optical properties of titanium dioxide nanotube arrays

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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.

  7. 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.

  8. 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.

  9. Acousto-Optic and Linear Electro-Optic Properties of Organic Polymeric Materials

    DTIC Science & Technology

    1989-04-27

    Naval Research Laboratory Washington, DC 20375-5000 NRL Memorandum Report 6454 od I3 Acousto - Optic and Linear Electro-Optic Properties of Organic...PROGRAM P1RC;EC7 ASK Arlington, VA 22217-5000 ELEMENT NO NO1 I1I TITLE (Include Security Classification) Acousto - Optic and Linear Electro-Optic...briefly discussing the important molecular properties for enhanced acousto ~ optic and electro-Ooptic ef fects and then relating these to "current

  10. Thermo-optically active planar polymeric components for telecommunication applications

    NASA Astrophysics Data System (ADS)

    Eldada, Louay A.; Beeson, Karl W.; Pant, Deepti; Blomquist, Robert; Shacklette, Lawrence W.; McFarland, Michael J.

    2000-05-01

    A key property that differentiates optical polymers from more conventional optical materials such as glass, is the rapid variation of the refractive index with temperature. This large difference in dn/dT can be leveraged to produce efficient thermo-optically active optical components. An advanced polymeric waveguide technology was developed for affordable thermo-optically active integrated optical devices that address the needs of the telecom industry. We engineered high-performance organic polymers that can be readily made into single-mode waveguide structures of controlled geometries and of modal profiles that closely match standard telecom glass fibers. These materials are formed from highly-crosslinked halogenated acrylate monomers with specific linkages that determined properties such as flexibility, toughness, optical loss, thermal stability, and humidity resistance. These monomers are intermiscible, providing for precise continuous adjustment of the refractive index over a wide range. In polymer form, they exhibit state-of-the-art loss values, suppressed polarization effects, and exceptional environmental stability. The devices we describe include thermally tunable Bragg-grating-based wavelength filters, thermally tunable arrayed-waveguide gratings, and digital optical switches.

  11. Optical properties of silver nano-cubes

    NASA Astrophysics Data System (ADS)

    Das, Ratan; Sarkar, Sumit

    2015-10-01

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

  12. Genetic Engineering of Optical Properties of Biomaterials

    NASA Astrophysics Data System (ADS)

    Gourley, Paul; Naviaux, Robert; Yaffe, Michael

    2008-03-01

    Baker's yeast cells are easily cultured and can be manipulated genetically to produce large numbers of bioparticles (cells and mitochondria) with controllable size and optical properties. We have recently employed nanolaser spectroscopy to study the refractive index of individual cells and isolated mitochondria from two mutant strains. Results show that biomolecular changes induced by mutation can produce bioparticles with radical changes in refractive index. Wild-type mitochondria exhibit a distribution with a well-defined mean and small variance. In striking contrast, mitochondria from one mutant strain produced a histogram that is highly collapsed with a ten-fold decrease in the mean and standard deviation. In a second mutant strain we observed an opposite effect with the mean nearly unchanged but the variance increased nearly a thousand-fold. Both histograms could be self-consistently modeled with a single, log-normal distribution. The strains were further examined by 2-dimensional gel electrophoresis to measure changes in protein composition. All of these data show that genetic manipulation of cells represents a new approach to engineering optical properties of bioparticles.

  13. 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.

  14. Electrical and optical properties of carbon films

    NASA Astrophysics Data System (ADS)

    Kulkarni, Pranita

    Carbon and carbon-based materials, including graphite, diamond, and other thin-film structures, are being intensively researched for a wide range of electronic applications. A variety of graphitic, nano-structured carbon materials can be synthesized that have current or potential applications as thin-film transistors, photovoltaics, and supercapacitors. Diamond has been pursued for many years for electronics that can be used in extreme conditions, such as high temperature, high power, high frequency, and radiation environments. In this research study, electronic properties of diamond and graphitic films with crystallite or grain sizes in the nanometer range were investigated. The nano-structured graphitic carbon films were grown using a previously developed method based on the pyrolysis of poly(acrylonitrile) and poly(n-butyl acrylate) block copolymers (PAN-b-PBA). An important characteristic of these films is that the morphology (and therefore other properties) can be controlled by the compositions and processing of the starting block copolymers. Spherical, cylindrical, lamellar, and branched morphologies have been fabricated. The crystallite sizes, optical absorption, and morphology of PAN-b-PBA (containing 17.8% PAN) pyrolyzed between 400 and 600°C were determined and were compared to those derived by pyrolysis of PAN homopolymers at the same temperatures. Hall-effect measurements on pyrolyzed PAN-b-PBA films with spherical, cylindrical, and branched morphologies and homopolymer PAN films pyrolyzed at the same temperatures revealed that both PAN-b-PBA with different morphologies and PAN homopolymer-derived films had n-type conductivity; differences in carrier concentration and mobility values were correlated with the morphological differences of the films. Optical absorption measurements in the ultra-violet through visible wavelength range were also conducted on these films; measurements of the pseudo band-gaps and absorption coefficients were correlated with

  15. Accurate simulation of optical properties in dyes.

    PubMed

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

    2009-02-17

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

  16. Linear and nonlinear optical properties of chalcogenide microstructured optical fibers

    NASA Astrophysics Data System (ADS)

    Trolès, Johann; Brilland, Laurent; Caillaud, Celine; Renversez, Gilles; Mechin, David; Adam, Jean-Luc

    2015-03-01

    Chalcogenide glasses are known for their large transparency in the mid-infrared and their high linear refractive index (>2). They present also a high non-linear coefficient (n2), 100 to 1000 times larger than for silica, depending on the composition. we have developed a casting method to prepare the microstructured chalcogenide preform. This method allows optical losses as low as 0.4 dB/m at 1.55 µm and less than 0.05 dB/m in the mid IR. Various chalcogenide MOFs operating in the IR range has been fabricated in order to associate the high non-linear properties of these glasses and the original MOF properties. For example, small core fibers have been drawn to enhance the non linearities for telecom applications such as signal regeneration and generation of supercontinuum sources. On another hand, in the 3-12 µm window, single mode fibers and exposed core fibers have been realized for Gaussian beams propagation and sensors applications respectively.

  17. 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.

  18. Active optics in Large Synoptic Survey Telescope

    NASA Astrophysics Data System (ADS)

    Liang, Ming; Krabbendam, Victor; Claver, Charles F.; Chandrasekharan, Srinivasan; Xin, Bo

    2012-09-01

    The Large Synoptic Survey Telescope (LSST) has a 3.5º field of view and F/1.2 focus that makes the performance quite sensitive to the perturbations of misalignments and mirror surface deformations. In order to maintain the image quality, LSST has an active optics system (AOS) to measure and correct those perturbations in a closed loop. The perturbed wavefront errors are measured by the wavefront sensors (WFS) located at the four corners of the focal plane. The perturbations are solved by the non-linear least square algorithm by minimizing the rms variation of the measured and baseline designed wavefront errors. Then the correction is realized by applying the inverse of the perturbations to the optical system. In this paper, we will describe the correction processing in the LSST AOS. We also will discuss the application of the algorithm, the properties of the sensitivity matrix and the stabilities of the correction. A simulation model, using ZEMAX as a ray tracing engine and MATLAB as an analysis platform, is set up to simulate the testing and correction loop of the LSST AOS. Several simulation examples and results are presented.

  19. Detecting eavesdropping activity in fiber optic networks

    NASA Astrophysics Data System (ADS)

    MacDonald, Gregory G.

    The secure transmission of data is critical to governments, military organizations, financial institutions, health care providers and other enterprises. The primary method of securing in-transit data is though data encryption. A number of encryption methods exist but the fundamental approach is to assume an eavesdropper has access to the encrypted message but does not have the computing capability to decrypt the message in a timely fashion. Essentially, the strength of security depends on the complexity of the encryption method and the resources available to the eavesdropper. The development of future technologies, most notably quantum computers and quantum computing, is often cited as a direct threat to traditional encryption schemes. It seems reasonable that additional effort should be placed on prohibiting the eavesdropper from coming into possession of the encrypted message in the first place. One strategy for denying possession of the encrypted message is to secure the physical layer of the communications path. Because the majority of transmitted information is over fiber-optic networks, it seems appropriate to consider ways of enhancing the integrity and security of the fiber-based physical layer. The purpose of this research is to investigate the properties of light, as they are manifested in single mode fiber, as a means of insuring the integrity and security of the physical layer of a fiber-optic based communication link. Specifically, the approach focuses on the behavior of polarization in single mode fiber, as it is shown to be especially sensitive to fiber geometry. Fiber geometry is necessarily modified during the placement of optical taps. The problem of detecting activity associated with the placement of an optical tap is herein approached as a supervised machine learning anomaly identification task. The inputs include raw polarization measurements along with additional features derived from various visualizations of the raw data (the inputs are

  20. Optical properties of vanadium dioxide and vanadium pentoxide thin films.

    PubMed

    Chain, E E

    1991-07-01

    Several oxides of vanadium undergo a transition from a semiconductor or insulating state to a metal phase at a critical temperature. Vanadium dioxide undergoes this transition near 68 degrees C, while V(2)O(5) undergoes a similar phase transition near 257 degrees C. During the transition a change in oxide crystal structure is accompanied by large changes in electrical and optical behavior. Thin films of vanadium oxides are capable of reversibly switching from the semiconductor to the metallic state at high speeds and with high spatial resolution. Therefore, these oxides have potential use, particularly in thin film form, for a wide variety of applications involving thermally activated electronic or optical switching devices. Such films are of considerable technical interest because of applications in chemical sensors, energy-conserving coatings, transparent conductors, and switching materials. The numerous potential electronic, optical, and optoelectronic device applications which have been suggested have stimulated work on the preparation of thin films by a variety of techniques, including chemical vapor deposition, solgel, evaporation, and sputter deposition. This paper reviews the optical properties of vanadium oxide coatings and stresses the dependence of film properties on sample preparation and resultant film microstructure.

  1. Optical and electrical properties of silicon nanopillars

    SciTech Connect

    Golobokova, L. S. Nastaushev, Yu. V.; Dultsev, F. N.; Kryzhanovskaya, N. V.; Moiseev, E. I.; Kozhukhov, A. S.; Latyshev, A. V.

    2015-07-15

    The electrical and optical properties of silicon nanopillars (Si NPs) are studied. Electron-beam lithography and reactive ion etching are used for the formation of ordered Si-NP arrays. The Si NPs with a diameter from 60 to 340 nm and a height from 218 to 685 nm are formed. The Si NPs are coated with a TiON{sup x} layer with a thickness of 8 nm for chemical and electrical passivation of the surface. Scanning electron microscopy and atomic-force microscopy are used to characterize the obtained structures. The Si-NP arrays acquire various colors when exposed to “bright-field” illumination. The spectra of reflection from the Si-NP arrays in the wavelength range 500–1150 nm are obtained.

  2. Electronic and optical properties of Praseodymium trifluoride

    SciTech Connect

    Saini, Sapan Mohan

    2014-10-24

    We report the role of f- states on electronic and optical properties of Praseodymium trifluoride (PrF{sub 3}) compound. Full potential linearized augmented plane wave (FPLAPW) method with the inclusion of spin orbit coupling has been used. We employed the local spin density approximation (LSDA) and Coulomb-corrected local spin density approximation (LSDA+U). LSDA+U is known for treating the highly correlated 4f electrons properly. Our theoretical investigation shows that LSDA+U approximation reproduce the correct insulating ground state of PrF{sub 3}. On the other hand there is no significant difference of reflectivity calculated by LSDA and LSDA+U. We find that the reflectivity for PrF{sub 3} compound stays low till around 7 eV which is consistent with their large energy gaps. Our calculated reflectivity compares well with the experimental data. The results are analyzed in the light of transitions involved.

  3. Optical properties of thin nanosilicon films

    NASA Astrophysics Data System (ADS)

    Buchenko, Viktor V.; Rodionova, Tatiana V.; Sutyagina, Anastasia S.; Goloborodko, Andrey A.; Multian, Volodymyr V.; Uklein, Andrii V.; Gayvoronsky, Volodymyr Ya.

    2016-12-01

    Present paper is devoted to the investigation of the nanosilicon films internal structure effect on optical properties. Atomic force microscopy results reveal that the films with different thickness have fundamentally different grain size distribution (samples with the film thickness less than 50 nm have single-mode grain size distribution, while samples with the film thickness more than 50 nm have multi-mode distribution of grain size). The correlation between grain size of nanosilicon films, photoluminescence and scattering indicatrix was shown. Well-isolated vibronic structures were observed on the ultraviolet-visible photoluminescence spectrum from nanosilicon films with the thickness more than 10 nm. The photoluminescence spectra in the red range correlate with the nanosilicon grain size distribution due to the effect of the quantum confinement. However, due to the complex shape of the grains mathematical modeling of photoluminescence spectrum is complicated. Both scattering indicatrix and photoluminescence reveal the multi-mode grain size distribution of the films with thickness more than 50 nm. The comparative analysis of theoretical results of optical radiation scattering by nanosilicon films with experimental ones is illustrated. Mathematical modeling of the scattering indicatrix shows the correlation of average grain size from scattering and photoluminescence data.

  4. 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.

  5. Optical properties of silicon inverse opals

    NASA Astrophysics Data System (ADS)

    Wei, Hong

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

  6. Synthesis, characterization and optical properties of nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Shoutian

    ZnO, Si, silica, Ge, Ga oxide, W oxide and Mo oxide nanoparticles have been synthesized and characterized, and their optical properties have been investigated. These particles were synthesized by a Laser Vaporization and Controlled Condensation (LVCC) technique in a modified diffusion cloud chamber. The particles deposited on smooth substrates reveal highly organized web-like structures with uniform micrometer size pores. The effect of solvents on the web-like structures was also investigated. ZnO nanoparticles were also prepared by wet chemical methods such as the reversed micelle and sol solutions technique. The photoluminescence quantum yield is enhanced 10 times once the surfaces of the ZnO nanoparticles are coated with a layer of stearate molecules. Many techniques have been used to characterize the nanoparticles. SEM gives information about particle size and morphology; X-ray diffraction and Raman spectroscopy determine the crystallinity and crystal structure; XPS and FTIR reveal the surface chemical composition; UV-vis spectroscopy and photoluminescence measurements characterize the optical properties of nanoparticles. Silica nanoparticles, prepared in an amorphous phase, show bright blue photoluminescence upon irradiation with UV light, but the luminescence has a very short lifetime (less than 20 ns). Si nanoparticles, with a diamond-like crystal phase, acquire oxidized-surfaces on exposure to air. The surface-oxidized Si nanocrystals show a short- lived blue emission characteristic of the SiO2 coating and a longer-lived red emission at room temperature. The lifetime of the red emission depends on the emission wavelength. Some substituted benzene molecules and tungsten oxide nanoparticles can quench the red photoluminescence of the Si nanocrystals. Tungsten oxide and molybdenum oxide nanoparticles show photochromic properties: they change color to blue when irradiated. The photons drive a transition from one chemical state to another. The color change of

  7. Thermo-optical properties of embedded silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Rashidi Huyeh, M.; Shirdel Havar, M.; Palpant, B.

    2012-11-01

    Thermo-optical properties of nanocomposite materials consisting of noble metal nanoparticles dispersed in a dielectric medium are appropriate for many applications as imaging, nonlinear optics, or optical monitoring of local thermal exchanges. Here, we analyze the thermo-optical response of silver nanoparticles. The contribution of inter- and intraband transitions to the thermo-optical index of bulk silver is first extracted using experimental results reported earlier in the literature. The influence of these two contributions on the thermo-optical properties of silver nanoparticles embedded in glass is then investigated. The results show that these properties are essentially due to the intraband thermo-optical contribution in the vicinity of the surface plasmon resonance of the nanoparticles, while they are dominated by the interband contribution close to the interband transition threshold.

  8. Physical and Optical Polarizability and Transport Properties of Bismuthate Glasses

    NASA Astrophysics Data System (ADS)

    Bale, Shashidhar; Rahman, Syed

    Bismuth-based glasses containing ZnO, B2O3 and Li2O are investigated through different physical, polarizability and transport properties. Raman spectroscopy reveals that these glasses are built from [BiO3] and [BiO6] units. Zinc in tetrahedral form is also observed. Density and glass transition temperature increase with the bismuth content. The refractive index, oxide ion polarizability and optical basicity also increase with the Bi2O3 content, whereas the interaction parameter decreases. The DC electrical conductivity increases and the activation energy decreases with the increase in the Li2O content.

  9. Active/Passive Optical Hydrography

    DTIC Science & Technology

    1990-01-01

    existing date Sources,A D -A 230 6 7 )and r ~twn he Colieclio.n of Information. Send comments regarding this burden estimate Of any other aspect 0f ’nog thc...PormEmntN.63704w 1.~ ________________________________________________________________ Prolec I No. 01987 * J 6. Author(s). Task No. l... Stephen P...to 3 optical depths. krey v-iov-Ac - --- ~ H r ~ o~~ surveyj nq 14. Subject Terms. 15. Number of Pages. (u) mutispectral; (U) Hydrographic Surveying

  10. Optical properties of sol-gel-derived PZT thin films

    NASA Astrophysics Data System (ADS)

    Teowee, Gimtong T.; Boulton, J. M.; Motakef, Sharnaz; Uhlmann, Donald R.; Zelinski, Brian J.; Zanoni, Raymond; Moon, M.

    1992-12-01

    A series of sol-gel derived PT-based films, including PT, PZ, PZT, PLT, PLZ and PLZT, was prepared on platinized Si, fused SiO2 and Corning 7059 substrates. These films were fired at 400 - 700 C for 30 mins. The phase assembly and development were dependent on the precursor chemistries, processing and choice of substrates. The presence of Zr impacted significantly on the crystallization behavior, PbO loss and cracking behavior of the films. Crystallization was severely retarded, especially in Zr-containing PZT films when deposited on amorphous substrates compared to crystalline Pt substrates. Amorphous and crystalline PZT films can be utilized for passive and active optical applications. Waveguiding was achieved in an amorphous PZT 53/47 and a crystalline PLT 28 films and gave attenuation losses of 1.0 and 1.4 dB/cm respectively which represent the lowest values reported to date. The optical properties of the films were investigated using ellipsometry, UV-VIS transmission spectroscopy and waveguide loss measurements. Depending on composition and processing conditions, PZT films (2500 A thick) with refractive indices of 1.60 to 2.33 and absorption edges of 2900 - 3100 A can be obtained. It was ascertained that the resulting interfacial reaction layers between the films and substrates affected considerably the optical properties of thinner films (< 2000 A).

  11. Nonlinear optical properties and supercontinuum spectrum of titania-modified carbon quantum dots

    NASA Astrophysics Data System (ADS)

    Kulchin, Yu N.; Mayor, A. Yu; Proschenko, D. Yu; Postnova, I. V.; Shchipunov, Yu A.

    2016-04-01

    We have studied the nonlinear optical properties and supercontinuum spectrum of solutions of carbon quantum dots prepared by a hydrothermal process from chitin and then coated with titania. The titania coating has been shown to have an activating effect on the carbon quantum dots, enhancing supercontinuum generation in the blue-violet spectral region and enabling their nonlinear optical characteristics to be varied.

  12. LDEF active optical system components experiment

    NASA Technical Reports Server (NTRS)

    Blue, M. D.

    1992-01-01

    A preliminary report on the Active Optical System Components Experiment is presented. This experiment contained 136 components in a six inch deep tray including lasers, infrared detectors and arrays, ultraviolet light detectors, light-emitting diodes, a light modulator, flash lamps, optical filters, glasses, and samples of surface finishes. Thermal, mechanical, and structural considerations leading to the design of the tray hardware are discussed. In general, changes in the retested component characteristics appear as much related to the passage of time as to the effects of the space environment, but organic materials, multilayer optical interference filters, and extreme-infrared reflectivity of black paints show unexpected changes.

  13. Dy(3)(+) -, Sm(3)(+) -, Ce(3)(+) - and Tb(3)(+) -activated optical properties of microcrystalline BaMgP2 O7 phosphors.

    PubMed

    Wani, J A; Dhoble, N S; Kokode, N S; Singh, Vijay; Dhoble, S J

    2017-03-01

    Photoluminescence (PL) and thermoluminescence (TL) properties of rare earth (RE) ion (RE = Dy(3)(+) , Sm(3)(+) , Ce(3)(+) , Tb(3)(+) ) activated microcrystalline BaMgP2 O7 phosphors are presented in this work. Non-doped and doped samples of BaMgP2 O7 were prepared using a solid state diffusion method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), PL and TL. The XRD measurement confirmed the phase purity of the BaMgP2 O7 host matrix. The average particle size was found through SEM measurement to be around 2 μm. All activators using the PL technique displayed characteristic excitation and emission spectra that corresponded to their typical f → f and f → d transitions respectively. Thermoluminescence measurements showed that BaMgP2 O7 :RE (RE = Dy(3)(+) , Sm(3)(+) , Tb(3)(+) , Ce(3)(+) ) and co-doped BaMgP2 O7 :Ce(3)(+) ,Tb(3)(+) phosphors have also TL behaviour.

  14. Hygroscopicity and optical properties of alkylaminium sulfates.

    PubMed

    Hu, Dawei; Li, Chunlin; Chen, Hui; Chen, Jianmin; Ye, Xingnan; Li, Ling; Yang, Xin; Wang, Xinming; Mellouki, Abdelwahid; Hu, Zhongyang

    2014-01-01

    The hygroscopicity and optical properties of alkylaminium sulfates (AASs) were investigated using a hygroscopicity tandem differential mobility analyzer coupled to a cavity ring-down spectrometer and a nephelometer. AAS particles do not exhibit a deliquescence phenomenon and show a monotonic increase in diameter as the relative humidity (RH) ascends. Hygroscopic growth factors (GFs) for 40, 100 and 150 nm alkylaminium sulfate particles do not show an apparent Kelvin effect when RH is less than 45%, whereas GFs of the salt aerosols increase with initial particle size when RH is higher than 45%. Calculation using the Zdanovskii-Stokes-Robinson mixing rule suggests that hygroscopic growth of triethylaminium sulfate-ammonium sulfate mixtures is non-deliquescent, occurring at very low RH, implying that the displacement of ammonia by amine will significantly enhance the hygroscopicity of (NH4)2SO4 aerosols. In addition, light extinction of AAS particles is a combined effect of both scattering and absorption under dry conditions, but is dominated by scattering under wet conditions.

  15. Optical properties of GaN pyramids

    SciTech Connect

    Zeng, K.C.; Lin, J.Y.; Jiang, H.X.; Yang, W.

    1999-03-01

    Picosecond time-resolved photoluminescence (PL) spectroscopy has been used to investigate the optical properties of GaN pyramids overgrown on hexagonal-patterned GaN(0001) epilayers on sapphire and silicon substrates with AlN buffer layers. We found that: (i) the release of the biaxial compressive strain in GaN pyramids on GaN/AlN/sapphire substrate led to a 7 meV redshift of the spectral peak position with respect to the strained GaN epilayer grown under identical conditions; (ii) in the GaN pyramids on GaN/AlN/sapphire substrate, strong band edge transitions with much narrower linewidths than those in the GaN epilayer have been observed, indicating the improved crystalline quality of the overgrown pyramids; (iii) PL spectra taken from different parts of the pyramids revealed that the top of the pyramid had the highest crystalline quality; and (iv) the presence of strong band-to-impurity transitions in the pyramids were primarily due to the incorporation of the oxygen and silicon impurities from the SiO{sub 2} mask. {copyright} {ital 1999 American Institute of Physics.}

  16. 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.

  17. Configurational Molecular Glue: One Optically Active Polymer Attracts Two Oppositely Configured Optically Active Polymers

    NASA Astrophysics Data System (ADS)

    Tsuji, Hideto; Noda, Soma; Kimura, Takayuki; Sobue, Tadashi; Arakawa, Yuki

    2017-03-01

    D-configured poly(D-lactic acid) (D-PLA) and poly(D-2-hydroxy-3-methylbutanoic acid) (D-P2H3MB) crystallized separately into their homo-crystallites when crystallized by precipitation or solvent evaporation, whereas incorporation of L-configured poly(L-2-hydroxybutanoic acid) (L-P2HB) in D-configured D-PLA and D-P2H3MB induced co-crystallization or ternary stereocomplex formation between D-configured D-PLA and D-P2H3MB and L-configured L-P2HB. However, incorporation of D-configured poly(D-2-hydroxybutanoic acid) (D-P2HB) in D-configured D-PLA and D-P2H3MB did not cause co-crystallization between D-configured D-PLA and D-P2H3MB and D-configured D-P2HB but separate crystallization of each polymer occurred. These findings strongly suggest that an optically active polymer (L-configured or D-configured polymer) like unsubstituted or substituted optically active poly(lactic acid)s can act as “a configurational or helical molecular glue” for two oppositely configured optically active polymers (two D-configured polymers or two L-configured polymers) to allow their co-crystallization. The increased degree of freedom in polymer combination is expected to assist to pave the way for designing polymeric composites having a wide variety of physical properties, biodegradation rate and behavior in the case of biodegradable polymers.

  18. Configurational Molecular Glue: One Optically Active Polymer Attracts Two Oppositely Configured Optically Active Polymers.

    PubMed

    Tsuji, Hideto; Noda, Soma; Kimura, Takayuki; Sobue, Tadashi; Arakawa, Yuki

    2017-03-24

    D-configured poly(D-lactic acid) (D-PLA) and poly(D-2-hydroxy-3-methylbutanoic acid) (D-P2H3MB) crystallized separately into their homo-crystallites when crystallized by precipitation or solvent evaporation, whereas incorporation of L-configured poly(L-2-hydroxybutanoic acid) (L-P2HB) in D-configured D-PLA and D-P2H3MB induced co-crystallization or ternary stereocomplex formation between D-configured D-PLA and D-P2H3MB and L-configured L-P2HB. However, incorporation of D-configured poly(D-2-hydroxybutanoic acid) (D-P2HB) in D-configured D-PLA and D-P2H3MB did not cause co-crystallization between D-configured D-PLA and D-P2H3MB and D-configured D-P2HB but separate crystallization of each polymer occurred. These findings strongly suggest that an optically active polymer (L-configured or D-configured polymer) like unsubstituted or substituted optically active poly(lactic acid)s can act as "a configurational or helical molecular glue" for two oppositely configured optically active polymers (two D-configured polymers or two L-configured polymers) to allow their co-crystallization. The increased degree of freedom in polymer combination is expected to assist to pave the way for designing polymeric composites having a wide variety of physical properties, biodegradation rate and behavior in the case of biodegradable polymers.

  19. Configurational Molecular Glue: One Optically Active Polymer Attracts Two Oppositely Configured Optically Active Polymers

    PubMed Central

    Tsuji, Hideto; Noda, Soma; Kimura, Takayuki; Sobue, Tadashi; Arakawa, Yuki

    2017-01-01

    D-configured poly(D-lactic acid) (D-PLA) and poly(D-2-hydroxy-3-methylbutanoic acid) (D-P2H3MB) crystallized separately into their homo-crystallites when crystallized by precipitation or solvent evaporation, whereas incorporation of L-configured poly(L-2-hydroxybutanoic acid) (L-P2HB) in D-configured D-PLA and D-P2H3MB induced co-crystallization or ternary stereocomplex formation between D-configured D-PLA and D-P2H3MB and L-configured L-P2HB. However, incorporation of D-configured poly(D-2-hydroxybutanoic acid) (D-P2HB) in D-configured D-PLA and D-P2H3MB did not cause co-crystallization between D-configured D-PLA and D-P2H3MB and D-configured D-P2HB but separate crystallization of each polymer occurred. These findings strongly suggest that an optically active polymer (L-configured or D-configured polymer) like unsubstituted or substituted optically active poly(lactic acid)s can act as “a configurational or helical molecular glue” for two oppositely configured optically active polymers (two D-configured polymers or two L-configured polymers) to allow their co-crystallization. The increased degree of freedom in polymer combination is expected to assist to pave the way for designing polymeric composites having a wide variety of physical properties, biodegradation rate and behavior in the case of biodegradable polymers. PMID:28338051

  20. Photovoltaic concentrator assembly with optically active cover

    DOEpatents

    Plesniak, Adam P

    2014-01-21

    A photovoltaic concentrator assembly that includes a housing that defines an internal volume and includes a rim, wherein the rim defines an opening into the internal volume, a photovoltaic cell positioned in the internal volume, and an optical element that includes an optically active body and a flange extending outward from the body, wherein the flange is sealingly engaged with the rim of the housing to enclose the internal volume.

  1. Active Optical Devices and Applications. Volume 228

    DTIC Science & Technology

    1980-04-01

    obscuration, 5-cm-thick solid, segmented (6 petals) Zerodur . Mirror A is near the limit of what can be fabricated with current technology. The honeycomb...DEW Descriptors, Keywords: Active Optical Device Application Large Optics Adaptive Technology Wavefront Sensor Deformable Mirror Performance...Cuneo, Jr., U.S. Air Force, NASA Headquarters 228-01 Wavefront sensors and deformable mirrors for visible wavelengths 4 Noah Bareket, Lockheed

  2. Recent optical activity of Mrk 421

    NASA Astrophysics Data System (ADS)

    Semkov, E.; Bachev, R.; Strigachev, A.; Ibryamov, S.; Peneva, S.; Gupta, A. C.

    2013-04-01

    Our BVRI optical observations of Mrk 421 were performed within the multiwavelength international campaign (December 2012-June 2013), with the participation of GASP-WEBT, Swift, MAGIC, VLBA, NuSTAR, Fermi, VERITAS, F-GAMMA and other collaborations. Following the reports of enhanced X-ray and gamma activity of Mrk 421 (ATel #4978, ATel #4977, ATel #4976, ATel #4974, ATel #4918), we observed this blazar with the optical telescopes of the National Astronomical Observatory Rozhen and the Astronomical Observatory Belogradchik, Bulgaria.

  3. Active properties of neuronal dendrites.

    PubMed

    Johnston, D; Magee, J C; Colbert, C M; Cristie, B R

    1996-01-01

    Dendrites of neurons in the central nervous system are the principal sites for excitatory synaptic input. Although little is known about their function, two disparate perspectives have arisen to describe the activity patterns inherent to these diverse tree-like structures. Dendrites are thus considered either passive or active in their role in integrating synaptic inputs. This review follows the history of dendritic research from before the turn of the century to the present, with a primary focus on the hippocampus. A number of recent techniques, including high-speed fluorescence imaging and dendritic patch clamping, have provided new information and perspectives about the active properties of dendrites. The results support previous notions about the dendritic propagation of action potentials and also indicate which types of voltage-gated sodium and calcium channels are expressed and functionally active in dendrites. Possible roles for the active properties of dendrites in synaptic plasticity and integration are also discussed.

  4. Optically active quantum-dot molecules.

    PubMed

    Shlykov, Alexander I; Baimuratov, Anvar S; Baranov, Alexander V; Fedorov, Anatoly V; Rukhlenko, Ivan D

    2017-02-20

    Chiral molecules made of coupled achiral semiconductor nanocrystals, also known as quantum dots, show great promise for photonic applications owing to their prospective uses as configurable building blocks for optically active structures, materials, and devices. Here we present a simple model of optically active quantum-dot molecules, in which each of the quantum dots is assigned a dipole moment associated with the fundamental interband transition between the size-quantized states of its confined charge carriers. This model is used to analytically calculate the rotatory strengths of optical transitions occurring upon the excitation of chiral dimers, trimers, and tetramers of general configurations. The rotatory strengths of such quantum-dot molecules are found to exceed the typical rotatory strengths of chiral molecules by five to six orders of magnitude. We also study how the optical activity of quantum-dot molecules shows up in their circular dichroism spectra when the energy gap between the molecular states is much smaller than the states' lifetime, and maximize the strengths of the circular dichroism peaks by optimizing orientations of the quantum dots in the molecules. Our analytical results provide clear design guidelines for quantum-dot molecules and can prove useful in engineering optically active quantum-dot supercrystals and photonic devices.

  5. Optical properties of micromachined polysilicon reflective surfaces with etching holes

    NASA Astrophysics Data System (ADS)

    Zou, Jun; Byrne, Colin; Liu, Chang; Brady, David J.

    1998-08-01

    MUMPS (Multi-User MEMS Process) is receiving increasingly wide use in micro optics. We have investigated the optical properties of the polysilicon reflective surface in a typical MUMPS chip within the visible light spectrum. The effect of etching holes on the reflected laser beam is studied. The reflectivity and diffraction patterns at five different wavelengths have been measured. The optical properties of the polysilicon reflective surface are greatly affected by the surface roughness, the etching holes, as well as the material. The etching holes contribute to diffraction and reduction of reflectivity. This study provides a basis for optimal design of micromachined free-space optical systems.

  6. 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.

  7. Advances in Measuring the Apparent Optical Properties (AOPs) of Optically Complex Waters

    NASA Technical Reports Server (NTRS)

    Morrow, John H.; Hooker, Stanford B.; Booth, Charles R.; Bernhard, Germar; Lind, Randall N.; Brown, James W.

    2010-01-01

    This report documents new technology used to measure the apparent optical properties (AOPs) of optically complex waters. The principal objective is to be prepared for the launch of next-generation ocean color satellites with the most capable commercial off-the-shelf (COTS) instrumentation. An enhanced COTS radiometer was the starting point for designing and testing the new sensors. The follow-on steps were to apply the lessons learned towards a new in-water profiler based on a kite-shaped backplane for mounting the light sensors. The next level of sophistication involved evaluating new radiometers emerging from a development activity based on so-called microradiometers. The exploitation of microradiometers resulted in an in-water profiling system, which includes a sensor networking capability to control ancillary sensors like a shadowband or global positioning system (GPS) device. A principal advantage of microradiometers is their flexibility in producing, interconnecting, and maintaining instruments. The full problem set for collecting sea-truth data--whether in coastal waters or the open ocean-- involves other aspects of data collection that were improved for instruments measuring both AOPs and inherent optical properties (IOPs), if the uncertainty budget is to be minimized. New capabilities associated with deploying solar references were developed as well as a compact solution for recovering in-water instrument systems from small boats.

  8. Femtosecond spectral interferometry of optical activity: Theory

    NASA Astrophysics Data System (ADS)

    Rhee, Hanju; Ha, Jeong-Hyon; Jeon, Seung-Joon; Cho, Minhaeng

    2008-09-01

    Optical activities such as circular dichroism (CD) and optical rotatory dispersion (ORD) are manifested by almost all natural products. However, the CD is an extremely weak effect so that time-resolved CD spectroscopy has been found to be experimentally difficult and even impossible for vibrational CD with current technology. Here, we show that the weak-signal and nonzero background problems can be overcome by heterodyned spectral interferometric detection of the phase and amplitude of optical activity free-induction-decay (OA FID) field. A detailed theoretical description and a cross-polarization scheme for selectively measuring the OA FID are presented and discussed. It is shown that the parallel and perpendicular electric fields when the solution sample contains chiral molecules are coupled to each other. Therefore, simultaneous spectral interferometric measurements of the parallel and perpendicular FID fields can provide the complex susceptibility, which is associated with the circular dichroism and optical rotatory dispersion as its imaginary and real parts, respectively. On the basis of the theoretical results, to examine its experimental possibility, we present numerical simulations for a model system. We anticipate the method discussed here to be a valuable tool for detecting electronic or vibrational optical activity in femtosecond time scale.

  9. Influence of optical activity on rogue waves propagating in chiral optical fibers

    NASA Astrophysics Data System (ADS)

    Temgoua, D. D. Estelle; Kofane, T. C.

    2016-06-01

    We derive the nonlinear Schrödinger (NLS) equation in chiral optical fiber with right- and left-hand nonlinear polarization. We use the similarity transformation to reduce the generalized chiral NLS equation to the higher-order integrable Hirota equation. We present the first- and second-order rational solutions of the chiral NLS equation with variable and constant coefficients, based on the modified Darboux transformation method. For some specific set of parameters, the features of chiral optical rogue waves are analyzed from analytical results, showing the influence of optical activity on waves. We also generate the exact solutions of the two-component coupled nonlinear Schrödinger equations, which describe optical activity effects on the propagation of rogue waves, and their properties in linear and nonlinear coupling cases are investigated. The condition of modulation instability of the background reveals the existence of vector rogue waves and the number of stable and unstable branches. Controllability of chiral optical rogue waves is examined by numerical simulations and may bring potential applications in optical fibers and in many other physical systems.

  10. Influence of optical activity on rogue waves propagating in chiral optical fibers.

    PubMed

    Temgoua, D D Estelle; Kofane, T C

    2016-06-01

    We derive the nonlinear Schrödinger (NLS) equation in chiral optical fiber with right- and left-hand nonlinear polarization. We use the similarity transformation to reduce the generalized chiral NLS equation to the higher-order integrable Hirota equation. We present the first- and second-order rational solutions of the chiral NLS equation with variable and constant coefficients, based on the modified Darboux transformation method. For some specific set of parameters, the features of chiral optical rogue waves are analyzed from analytical results, showing the influence of optical activity on waves. We also generate the exact solutions of the two-component coupled nonlinear Schrödinger equations, which describe optical activity effects on the propagation of rogue waves, and their properties in linear and nonlinear coupling cases are investigated. The condition of modulation instability of the background reveals the existence of vector rogue waves and the number of stable and unstable branches. Controllability of chiral optical rogue waves is examined by numerical simulations and may bring potential applications in optical fibers and in many other physical systems.

  11. Optical properties of mouse brain tissue after optical clearing with FocusClear™

    NASA Astrophysics Data System (ADS)

    Moy, Austin J.; Capulong, Bernard V.; Saager, Rolf B.; Wiersma, Matthew P.; Lo, Patrick C.; Durkin, Anthony J.; Choi, Bernard

    2015-09-01

    Fluorescence microscopy is commonly used to investigate disease progression in biological tissues. Biological tissues, however, are strongly scattering in the visible wavelengths, limiting the application of fluorescence microscopy to superficial (<200 μm) regions. Optical clearing, which involves incubation of the tissue in a chemical bath, reduces the optical scattering in tissue, resulting in increased tissue transparency and optical imaging depth. The goal of this study was to determine the time- and wavelength-resolved dynamics of the optical scattering properties of rodent brain after optical clearing with FocusClear™. Light transmittance and reflectance of 1-mm mouse brain sections were measured using an integrating sphere before and after optical clearing and the inverse adding doubling algorithm used to determine tissue optical scattering. The degree of optical clearing was quantified by calculating the optical clearing potential (OCP), and the effects of differing OCP were demonstrated using the optical histology method, which combines tissue optical clearing with optical imaging to visualize the microvasculature. We observed increased tissue transparency with longer optical clearing time and an analogous increase in OCP. Furthermore, OCP did not vary substantially between 400 and 1000 nm for increasing optical clearing durations, suggesting that optical histology can improve ex vivo visualization of several fluorescent probes.

  12. Optical properties of mouse brain tissue after optical clearing with FocusClear™

    PubMed Central

    Moy, Austin J.; Capulong, Bernard V.; Saager, Rolf B.; Wiersma, Matthew P.; Lo, Patrick C.; Durkin, Anthony J.; Choi, Bernard

    2015-01-01

    Abstract. Fluorescence microscopy is commonly used to investigate disease progression in biological tissues. Biological tissues, however, are strongly scattering in the visible wavelengths, limiting the application of fluorescence microscopy to superficial (<200  μm) regions. Optical clearing, which involves incubation of the tissue in a chemical bath, reduces the optical scattering in tissue, resulting in increased tissue transparency and optical imaging depth. The goal of this study was to determine the time- and wavelength-resolved dynamics of the optical scattering properties of rodent brain after optical clearing with FocusClear™. Light transmittance and reflectance of 1-mm mouse brain sections were measured using an integrating sphere before and after optical clearing and the inverse adding doubling algorithm used to determine tissue optical scattering. The degree of optical clearing was quantified by calculating the optical clearing potential (OCP), and the effects of differing OCP were demonstrated using the optical histology method, which combines tissue optical clearing with optical imaging to visualize the microvasculature. We observed increased tissue transparency with longer optical clearing time and an analogous increase in OCP. Furthermore, OCP did not vary substantially between 400 and 1000 nm for increasing optical clearing durations, suggesting that optical histology can improve ex vivo visualization of several fluorescent probes. PMID:26388460

  13. Science Data Report for the Optical Properties Monitor (OPM) Experiment

    NASA Technical Reports Server (NTRS)

    Wilkes, D. R.; Zwiener, J. M.; Carruth, Ralph (Technical Monitor)

    2001-01-01

    This science data report describes the Optical Properties Monitor (OPM) experiment and the data gathered during its 9-mo exposure on the Mir space station. Three independent optical instruments made up OPM: an integrating sphere spectral reflectometer, vacuum ultraviolet spectrometer, and a total integrated scatter instrument. Selected materials were exposed to the low-Earth orbit, and their performance monitored in situ by the OPM instruments. Coinvestigators from four NASA Centers, five International Space Station contractors, one university, two Department of Defense organizations, and the Russian space company, Energia, contributed samples to this experiment. These materials included a number of thermal control coatings, optical materials, polymeric films, nanocomposites, and other state-of-the-art materials. Degradation of some materials, including aluminum conversion coatings and Beta cloth, was greater than expected. The OPM experiment was launched aboard the Space Shuttle on mission STS-81 in January 1997 and transferred to the Mir space station. An extravehicular activity (EVA) was performed in April 1997 to attach the OPM experiment to the outside of the Mir/Shuttle Docking Module for space environment exposure. OPM was retrieved during an EVA in January 1998 and was returned to Earth on board the Space Shuttle on mission STS-89.

  14. Measurement of Optical Properties of Small Particles

    NASA Technical Reports Server (NTRS)

    Arakawa, E. T.; Tuminello, P. S.; Khare, B. N.; Millham, M. E.; Authier, S.; Pierce, J.

    1997-01-01

    We have measured the optical constants of montmorillonite and the separated coats and cores of B. subtilis spores over the wavelength interval from 200 nm to 2500 nm. The optical constants of kaolin were obtained over the wavelength interval from 130 nm to 2500 nm. Our results are applicable to the development of systems for detection of airborne biological contaminants. Future work will include measurement of the optical constants of B. cereus spores, B. sub tilts vegetative cells, egg albumin, illite, and a mixture (by weight) of one third kaolin, one third montmorillonite, and one third illite.

  15. Measurement of Optical Properties of Small Particles

    SciTech Connect

    Arakawa, E.T.; Tuminello, P.S.; Khare, B.N.; Millham, M.E.; Authier, S.; Pierce, J.

    1997-12-01

    We have measured the optical constants of montmorillonite and the separated coats and cores of B. subtilis spores over the wavelength interval from 200 nm to 2500 nm. The optical constants of kaolin were obtained over the wavelength interval from 130 nm to 2500 nm. Our results are applicable to the development of systems for detection of airborne biological contaminants. Future work will include measurement of the optical constants of B. cereus spores, B. sub tilts vegetative cells, egg albumin, illite, and a mixture (by weight) of one third kaolin, one third montmorillonite, and one third illite.

  16. Active learning in optics and photonics

    NASA Astrophysics Data System (ADS)

    Niemela, Joseph J.

    2016-09-01

    Active learning in optics and photonics (ALOP) is a program of the International Basic Sciences Program at UNESCO, in collaboration with the Abdus Salam International Centre for Theoretical Physics (ICTP) and supported by SPIE, which is designed to help teachers in the developing world attract and retain students in the physical sciences. Using optics and photonics, it naturally attracts the interest of students and can be implemented using relatively low cost technologies, so that it can be more easily reproduced locally. The active learning methodology is student-centered, meaning the teachers give up the role of lecturer in favor of guiding and facilitating a learning process in which students engage in hands-on activities and active peer-peer discussions, and is shown to effectively enhance basic conceptual understanding of physics.

  17. The Optical Properties of Biological Tissue.

    NASA Astrophysics Data System (ADS)

    Bews, Jeffrey Alan

    The ability of light to propagate through biological tissue has found much application in medicine (ie. Photodynamic therapy and Diaphanography). However, a poor understanding of this transport phenomenon has served to limit the effectiveness of those modalities employing it in their operation. This thesis is a study of light propagation through biological tissue, its goal being to improve on the lack of knowledge that presently exists. A spectrophotometer type instrument (DICOM-8) was developed to measure the diffuse spectra extinction of biological tissue. Results were obtained for both normal and diseased breast tissue. Extinction curves for the two tissues exhibited a similar shape (extinction monotonically decreasing with increasing wavelength) but differed in magnitude below 700 nm with carcinoma possessing a higher extinction than normal. Data obtained from these tissue measurements served as the basis for developing a homogeneous liquid (TEM) for simulating the optical properties of tissue over the range 550 to 900 nm. Bench-top Diaphanography studies carried out on a breast phantom constructed of TEM demonstrated the improved tumor visualization attainable with short wavelength light. TEM also functioned as a test medium in which light distributions resulting from highly controlled irradiation geometries (isotropic point and planar sources) were measured and compared with those predicted by Linear Transport (LT) theory. The mean free path (MFP) of TEM ranged from 0.206 mm at 550 nm to 0.495 mm at 900 nm and was found to be directly proportional to the square of the wavelength. The scatter/absorption coefficient (c) was 0.9986459 at 550 nm and 0.9997315 at 850 nm. Agreement between experimental and theoretical distributions was found to be extremely good. Theoretical distributions generated with LT theory revealed the fact that small changes in MFP will have little effect on light transport. Similar changes in c, meanwhile, will drastically alter the

  18. The Adaptive Optics Summer School Laboratory Activities

    NASA Astrophysics Data System (ADS)

    Ammons, S. M.; Severson, S.; Armstrong, J. D.; Crossfield, I.; Do, T.; Fitzgerald, M.; Harrington, D.; Hickenbotham, A.; Hunter, J.; Johnson, J.; Johnson, L.; Li, K.; Lu, J.; Maness, H.; Morzinski, K.; Norton, A.; Putnam, N.; Roorda, A.; Rossi, E.; Yelda, S.

    2010-12-01

    Adaptive Optics (AO) is a new and rapidly expanding field of instrumentation, yet astronomers, vision scientists, and general AO practitioners are largely unfamiliar with the root technologies crucial to AO systems. The AO Summer School (AOSS), sponsored by the Center for Adaptive Optics, is a week-long course for training graduate students and postdoctoral researchers in the underlying theory, design, and use of AO systems. AOSS participants include astronomers who expect to utilize AO data, vision scientists who will use AO instruments to conduct research, opticians and engineers who design AO systems, and users of high-bandwidth laser communication systems. In this article we describe new AOSS laboratory sessions implemented in 2006-2009 for nearly 250 students. The activity goals include boosting familiarity with AO technologies, reinforcing knowledge of optical alignment techniques and the design of optical systems, and encouraging inquiry into critical scientific questions in vision science using AO systems as a research tool. The activities are divided into three stations: Vision Science, Fourier Optics, and the AO Demonstrator. We briefly overview these activities, which are described fully in other articles in these conference proceedings (Putnam et al., Do et al., and Harrington et al., respectively). We devote attention to the unique challenges encountered in the design of these activities, including the marriage of inquiry-like investigation techniques with complex content and the need to tune depth to a graduate- and PhD-level audience. According to before-after surveys conducted in 2008, the vast majority of participants found that all activities were valuable to their careers, although direct experience with integrated, functional AO systems was particularly beneficial.

  19. Airborne LIDAR as a tool for estimating inherent optical properties

    NASA Astrophysics Data System (ADS)

    Trees, Charles; Arnone, Robert

    2012-06-01

    LIght Detection and Ranging (LIDAR) systems have been used most extensively to generate elevation maps of land, ice and coastal bathymetry. There has been space-, airborne- and land-based LIDAR systems. They have also been used in underwater communication. What have not been investigated are the capabilities of LIDARs to measure ocean temperature and optical properties vertically in the water column, individually or simultaneously. The practical use of bathymetric LIDAR as a tool for the estimation of inherent optical properties remains one of the most challenging problems in the field of optical oceanography. LIDARs can retrieve data as deep as 3-4 optical depths (e.g. optical properties can be measured through the thermocline for ~70% of the world's oceans). Similar to AUVs (gliders), UAV-based LIDAR systems will increase temporal and spatial measurements by several orders of magnitude. The LIDAR Observations of Optical and Physical Properties (LOOPP) Conference was held at NURC (2011) to review past, current and future LIDAR research efforts in retrieving water column optical/physical properties. This new observational platform/sensor system is ideally suited for ground truthing hyperspectral/geostationary satellite data in coastal regions and for model data assimilation.

  20. Optical properties of silicon germanium waveguides at telecommunication wavelengths.

    PubMed

    Hammani, Kamal; Ettabib, Mohamed A; Bogris, Adonis; Kapsalis, Alexandros; Syvridis, Dimitris; Brun, Mickael; Labeye, Pierre; Nicoletti, Sergio; Richardson, David J; Petropoulos, Periklis

    2013-07-15

    We present a systematic experimental study of the linear and nonlinear optical properties of silicon-germanium (SiGe) waveguides, conducted on samples of varying cross-sectional dimensions and Ge concentrations. The evolution of the various optical properties for waveguide widths in the range 0.3 to 2 µm and Ge concentrations varying between 10 and 30% is considered. Finally, we comment on the comparative performance of the waveguides, when they are considered for nonlinear applications at telecommunications wavelengths.

  1. LDEF active optical system components experiment

    NASA Technical Reports Server (NTRS)

    Blue, M. D.

    1991-01-01

    A preliminary report on the Active Optical System Components Experiment is presented. This experiment contained 136 components in a six-inch deep tray including lasers, infrared detectors and arrays, ultraviolet light detectors, light-emitting diodes, a light modulator, flash lamps, optical filters, glasses, and samples of surface finishes. The experimental results for those component characteristics appear as much related to the passage of time as to the effects of the space environment, but organic materials and extreme-infrared reflectivity of black paints show unexpected changes.

  2. OPTICAL PROPERTIES OF HOST GALAXIES OF EXTRAGALACTIC NUCLEAR WATER MASERS

    SciTech Connect

    Zhu Guangtun; Zaw, Ingyin; Blanton, Michael R.; Greenhill, Lincoln J.

    2011-12-01

    We study the optical properties of the host galaxies of nuclear 22 GHz ({lambda} = 1.35 cm) water masers. To do so, we cross-match the galaxy sample surveyed for water maser emission (123 detections and 3806 non-detections) with the Sloan Digital Sky Survey (SDSS) low-redshift galaxy sample (z < 0.05). Out of 1636 galaxies with SDSS photometry, we identify 48 detections; out of the 1063 galaxies that also have SDSS spectroscopy, we identify 33 detections. We find that maser detection rate is higher at higher optical luminosity (M{sub B} ), larger velocity dispersion ({sigma}), and higher [O III] {lambda}5007 luminosity, with [O III] {lambda}5007 being the dominant factor. These detection rates are essentially the result of the correlations of isotropic maser luminosity with all three of these variables. These correlations are natural if maser strength increases with central black hole mass and the level of active galactic nucleus (AGN) activity. We also find that the detection rate is higher in galaxies with higher extinction. Based on these results, we propose that maser surveys seeking to efficiently find masers should rank AGN targets by extinction-corrected [O III] {lambda}5007 flux when available. This prioritization would improve maser detection efficiency, from an overall {approx}3% without pre-selection to {approx}16% for the strongest intrinsic [O III] {lambda}5007 emitters, by a factor of {approx}5.

  3. Optical fiber sensor having an active core

    NASA Technical Reports Server (NTRS)

    Egalon, Claudio Oliveira (Inventor); Rogowski, Robert S. (Inventor)

    1993-01-01

    An optical fiber is provided. The fiber is comprised of an active fiber core which produces waves of light upon excitation. A factor ka is identified and increased until a desired improvement in power efficiency is obtained. The variable a is the radius of the active fiber core and k is defined as 2 pi/lambda wherein lambda is the wavelength of the light produced by the active fiber core. In one embodiment, the factor ka is increased until the power efficiency stabilizes. In addition to a bare fiber core embodiment, a two-stage fluorescent fiber is provided wherein an active cladding surrounds a portion of the active fiber core having an improved ka factor. The power efficiency of the embodiment is further improved by increasing a difference between the respective indices of refraction of the active cladding and the active fiber core.

  4. Optical Properties of Volcanic Ash: Improving Remote Sensing Observations

    NASA Astrophysics Data System (ADS)

    Whelley, P.; Colarco, P. R.; Aquila, V.; Krotkov, N. A.; Bleacher, J. E.; Garry, W. B.; Young, K. E.; Lima, A. R.; Martins, J. V.; Carn, S. A.

    2015-12-01

    Many times each year explosive volcanic eruptions loft ash into the atmosphere. Global travel and trade rely on aircraft vulnerable to encounters with airborne ash. Volcanic ash advisory centers (VAACs) rely on dispersion forecasts and satellite data to issue timely warnings. To improve ash forecasts model developers and satellite data providers need realistic information about volcanic ash microphysical and optical properties. In anticipation of future large eruptions we can study smaller events to improve our remote sensing and modeling skills so when the next Pinatubo 1991 or larger eruption occurs, ash can confidently be tracked in a quantitative way. At distances >100km from their sources, drifting ash plumes, often above meteorological clouds, are not easily detected from conventional remote sensing platforms, save deriving their quantitative characteristics, such as mass density. Quantitative interpretation of these observations depends on a priori knowledge of the spectral optical properties of the ash in UV (>0.3μm) and TIR wavelengths (>10μm). Incorrect assumptions about the optical properties result in large errors in inferred column mass loading and size distribution, which misguide operational ash forecasts. Similarly, simulating ash properties in global climate models also requires some knowledge of optical properties to improve aerosol speciation. Recent research has identified a wide range in volcanic ash optical properties among samples collected from the ground after different eruptions. The database of samples investigated remains relatively small, and measurements of optical properties at the relevant particle sizes and spectral channels are far from complete. Generalizing optical properties remains elusive, as does establishing relationships between ash composition and optical properties, which are essential for satellite retrievals. We are building a library of volcanic ash optical and microphysical properties. In this presentation we show

  5. Constitutive Modeling of the Mechanical Properties of Optical Fibers

    NASA Technical Reports Server (NTRS)

    Moeti, L.; Moghazy, S.; Veazie, D.; Cuddihy, E.

    1998-01-01

    Micromechanical modeling of the composite mechanical properties of optical fibers was conducted. Good agreement was obtained between the values of Young's modulus obtained by micromechanics modeling and those determined experimentally for a single mode optical fiber where the wave guide and the jacket are physically coupled. The modeling was also attempted on a polarization-maintaining optical fiber (PANDA) where the wave guide and the jacket are physically decoupled, and found not to applicable since the modeling required perfect bonding at the interface. The modeling utilized constituent physical properties such as the Young's modulus, Poisson's ratio, and shear modulus to establish bounds on the macroscopic behavior of the fiber.

  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. Structural and optical properties for typical solid mirror shapes

    NASA Technical Reports Server (NTRS)

    Cho, Myung K.; Richard, Ralph M.

    1990-01-01

    A method is developed to determine the weight, center of gravity, areal properties, and mass inertial properties for typical mirrors. A number of support conditions were considered to examine optical surface deflections, surface quality, and fundamental natural frequency for single- and double-arch mirror shapes. Structural performance estimates were made with the NASTRAN program, and optical performances were evaluated with the FRINGE program, using an SXA 40-in mirror. To show the behavior of element types from the NASTRAN program, finite element validity and sensitivity studies were performed in optical model applications. Material parameters, contoured back shapes, and support locations are shown to have significant effects on structural and optical performances. Optimal support locations and support points are given. Fundamental natural frequencies for some shapes are found with the closed-form solution. The plate models results may not be acceptable for determining real mirror optical performances.

  8. 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.

  9. 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.

  10. [Preparation and optical properties of tantalum tungsten bronze].

    PubMed

    Mu, Wan-jun; Xie, Xiang; Li, Xing-liang; Zhang, Rui; Lü, Kai; Wei, Hong-yuan

    2015-01-01

    Tantalum tungsten bronze(TaxWO3)nanowires were successfully synthesized via hydrothermal method using TaCl5 and Na2WO4 . 2H20 as raw materials. The morphology, crystal structure and optical properties of synthesized products were characterized by means of XRD, TEM, SEM, UV-Vis and Raman technologies. The XRD results showed that TaxWO3 nanowire exhibited hexagonal structure. By increasing the doping content, the cell parameter was kept increasing gradually till Ta/W= 0. 04, then it remained almost constant. The UV-Vis diffraction spectrum analysis showed that the absorption peaks redshifted, the band gap energy decreased with increasing the doping content. The Raman peaks moved with a downshift, and the peak gradually became broader, which further proved the influence of the tantalum doping for tungsten oxide. The reactions of decomposing liquid rhodamine B solution showed that the nanosized TaxWO3 had a high photo-catalytic activity.

  11. Optical properties of aerosols at Grand Canyon National Park

    NASA Astrophysics Data System (ADS)

    Malm, William C.; Day, Derek E.

    Visibility in the United States is expected to improve over the next few decades because of reduced emissions, especially sulfur dioxide. In the eastern United States, sulfates make up about 60-70% of aerosol extinction, while in the inner mountain west that fraction is only about 30%. In the inner mountain west, carbon aerosols make up about 35% of extinction, while coarse mass contributes between 15 and 25% depending on how absorption is estimated. Although sulfur dioxide emissions are projected to decrease, carbon emissions due to prescribed fire activity will increase by factors of 5-10, and while optical properties of sulfates have been extensively studied, similar properties of carbon and coarse particles are less well understood. The inability to conclusively apportion about 50% of the extinction budget motivated a study to examine aerosol physio-chemical-optical properties at Grand Canyon, Arizona during the months of July and August. Coarse particle mass has usually been assumed to consist primarily of wind-blown dust, with a mass-scattering efficiency between about 0.4 and 0.6 m 2 g -1. Although there were episodes where crustal material made up most of the coarse mass, on the average, organics and crustal material mass were about equal. Furthermore, about one-half of the sampling periods had coarse-mass-scattering efficiencies greater than 0.6 m 2 g -1 and at times coarse-mass-scattering efficiencies were near 1.0 m 2 g -1. It was shown that absorption by coarse- and fine-particle absorption were about equal and that both fine organic and sulfate mass-scattering efficiencies were substantially less than the nominal values of 4.0 and 3.0 m 2 g -1 that have typically been used.

  12. (Bio)hybrid materials based on optically active particles

    NASA Astrophysics Data System (ADS)

    Reitzig, Manuela; Härtling, Thomas; Opitz, Jörg

    2014-03-01

    In this contribution we provide an overview of current investigations on optically active particles (nanodiamonds, upconversion phospors) for biohybrid and sensing applications. Due to their outstanding properties nanodiamonds gain attention in various application elds such as microelectronics, optical monitoring, medicine, and biotechnology. Beyond the typical diamond properties such as high thermal conductivity and extreme hardness, the carbon surface and its various functional groups enable diverse chemical and biological surface functionalization. At Fraunhofer IKTS-MD we develop a customization of material surfaces via integration of chemically modi ed nanodiamonds at variable surfaces, e.g bone implants and pipelines. For the rst purpose, nanodiamonds are covalently modi ed at their surface with amino or phosphate functionalities that are known to increase adhesion to bone or titanium alloys. The second type of surface is approached via mechanical implementation into coatings. Besides nanodiamonds, we also investigate the properties of upconversion phosphors. In our contribution we show how upconversion phosphors are used to verify sterilization processes via a change of optical properties due to sterilizing electron beam exposure.

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

    PubMed Central

    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. Electro-optical and physic-mechanical properties of colored alicyclic polyimide

    NASA Astrophysics Data System (ADS)

    Kravtsova, V.; Umerzakova, M.; Korobova, N.; Timoshenkov, S.; Timoshenkov, V.; Orlov, S.; Iskakov, R.; Prikhodko, O.

    2016-09-01

    Main optical, thermal and mechanical properties of new compositions based on alicyclic polyimide and active bright red 6C synthetic dye have been studied. It was shown that the transmission ratio of the new material in the region of 400-900 nm and 2.0 wt.% dye concentration was around 60-70%. Thermal, mechanical and electrical properties of new colored compositions were comparable with the properties of original polyimide.

  15. Dielectric and Optical Properties of Thin Films.

    DTIC Science & Technology

    1978-08-01

    Is const ructed from a thin slice of bismuth silicon oxlde,~ a cubic crystal exhibiting the Pockels effect. The crystal also is photoconductive when... Photoconductive diameter electro -optical crystal ~~~~~~~~~~~~~~~~~ i12SiO20) Electrode 2 Insulator layer Electrode 1 (paralene) Figure 1-1

  16. Optical properties of direct restorative materials

    SciTech Connect

    Miyagawa, Y.; Powers, J.M.; O'Brien, W.J.

    1981-05-01

    The contrast ratio, light reflectivity, scattering coefficient, and absorption coefficient of four composites and an unfilled resin were calculated algebraically from reflection spectrophotometric data using Kubelka's equations. The correlation coefficient between calculated and experimental values of contrast ratio was 0.9996. Values of infinite optical thickness ranged from 4.19 to 6.70 mm.

  17. Nonlinear optical properties of rigid-rod polymers

    NASA Technical Reports Server (NTRS)

    Trimmer, Mark S.; Wang, Ying

    1992-01-01

    The purpose of this research project was to integrate enhanced third order nonlinear optical (NLO) properties, especially high x(exp (3)) (greater than 10(exp -8) esu), into Maxdem's novel conjugated rigid-rod polymers while retaining their desirable processing, mechanical, and thermal properties. This work primarily involved synthetic approaches to optimized materials.

  18. Estimation of Korean paddy field soil properties using optical reflectance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An optical sensing approach based on diffuse reflectance has shown potential for rapid and reliable on-site estimation of soil properties. Important sensing ranges and the resulting regression models useful for soil property estimation have been reported. In this study, a similar approach was applie...

  19. Region-based diffuse optical tomography with registered atlas: in vivo acquisition of mouse optical properties

    PubMed Central

    Wan, Wenbo; Wang, Yihan; Qi, Jin; Liu, Lingling; Ma, Wenjuan; Li, Jiao; Zhang, Limin; Zhou, Zhongxing; Zhao, Huijuan; Gao, Feng

    2016-01-01

    The reconstruction quality in the model-based optical tomography modalities can greatly benefit from a priori information of accurate tissue optical properties, which are difficult to be obtained in vivo with a conventional diffuse optical tomography (DOT) system alone. One of the solutions is to apply a priori anatomical structures obtained with anatomical imaging systems such as X-ray computed tomography (XCT) to constrain the reconstruction process of DOT. However, since X-ray offers low soft-tissue contrast, segmentation of abdominal organs from sole XCT images can be problematic. In order to overcome the challenges, the current study proposes a novel method of recovering a priori organ-oriented tissue optical properties, where anatomical structures of an in vivo mouse are approximately obtained by registering a standard anatomical atlas, i.e., the Digimouse, to the target XCT volume with the non-rigid image registration, and, in turn, employed to guide DOT for extracting the optical properties of inner organs. Simulative investigations have validated the methodological availability of such atlas-registration-based DOT strategy in revealing both a priori anatomical structures and optical properties. Further experiments have demonstrated the feasibility of the proposed method for acquiring the organ-oriented tissue optical properties of in vivo mice, making it as an efficient way of the reconstruction enhancement. PMID:28018725

  20. Lanthanide upconversion luminescence at the nanoscale: fundamentals and optical properties

    NASA Astrophysics Data System (ADS)

    Nadort, Annemarie; Zhao, Jiangbo; Goldys, Ewa M.

    2016-07-01

    Upconversion photoluminescence is a nonlinear effect where multiple lower energy excitation photons produce higher energy emission photons. This fundamentally interesting process has many applications in biomedical imaging, light source and display technology, and solar energy harvesting. In this review we discuss the underlying physical principles and their modelling using rate equations. We discuss how the understanding of photophysical processes enabled a strategic influence over the optical properties of upconversion especially in rationally designed materials. We subsequently present an overview of recent experimental strategies to control and optimize the optical properties of upconversion nanoparticles, focussing on their emission spectral properties and brightness.

  1. Mechanical And Thermal Properties Of Optical Materials - A Review

    NASA Astrophysics Data System (ADS)

    Ballard, Stanley S.

    1980-02-01

    In selecting an optical material, the instrument designer's first consideration is optical properties, especially transmission region but also homogeneity, freedom from birefringence, perhaps refractive index and dispersion. Next in his hierarchy are the other physical properties: mechanical, thermal, and chemical (solubility, for example). In this review article, the several properties are listed, and data sources are given. No single compilation or handbook contains all the desired data, so many references are quoted. This review covers materials useful in the ultraviolet and esuecially the infrared spectral regions; it does not include the standard glasses used in the visible region.

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

    SciTech Connect

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

    2010-07-16

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

  3. Optical activity of chirally distorted nanocrystals

    NASA Astrophysics Data System (ADS)

    Tepliakov, Nikita V.; Baimuratov, Anvar S.; Baranov, Alexander V.; Fedorov, Anatoly V.; Rukhlenko, Ivan D.

    2016-05-01

    We develop a general theory of optical activity of semiconductor nanocrystals whose chirality is induced by a small perturbation of their otherwise achiral electronic subsystems. The optical activity is described using the quantum-mechanical expressions for the rotatory strengths and dissymmetry factors introduced by Rosenfeld. We show that the rotatory strengths of optically active transitions are decomposed on electric dipole and magnetic dipole contributions, which correspond to the electric dipole and magnetic dipole transitions between the unperturbed quantum states. Remarkably, while the two kinds of rotatory strengths are of the same order of magnitude, the corresponding dissymmetry factors can differ by a factor of 105. By maximizing the dissymmetry of magnetic dipole absorption one can significantly enhance the enantioselectivity in the interaction of semiconductor nanocrystals with circularly polarized light. This feature may advance chiral and analytical methods, which will benefit biophysics, chemistry, and pharmaceutical science. The developed theory is illustrated by an example of intraband transitions inside a semiconductor nanocuboid, whose rotatory strengths and dissymmetry factors are calculated analytically.

  4. Influence of river discharge and ocean currents on coastal optical properties

    NASA Astrophysics Data System (ADS)

    Cherukuru, Nagur; Brando, Vittorio E.; Schroeder, Thomas; Clementson, Lesley A.; Dekker, Arnold G.

    2014-08-01

    The variability in the optical properties of a coastal region influenced by river runoff and multiple ocean currents in a southern hemisphere setting has been studied. The study area, Tasmanian coastal waters, is influenced by subtropical currents such as the East Australian Current (EAC) and the Zeehan Current (ZC) mix with cooler sub-Antarctic water (SAW). Freshwater discharges from rivers around the island and their mixing with the ocean currents also influence Tasmanian coastal waters. This study was performed to understand the influence of hydrodynamic processes on coastal optical properties and underwater light propagation. Physical, biogeochemical and optical properties were measured in Tasmanian coastal water during the austral autumn of 2007. In this study we found that physical properties have a good correlation with optical properties indicating the role played by hydrodynamic processes in distribution of optically active substances, optical properties of the water mass and underwater light propagation. Analysis of in situ salinity and temperature confirmed the presence of relatively cooler ZC in the South-West region, a cooler mixture of the ZC and SAW in the South-East, warm and saline EAC waters along the East coast and relatively cooler and fresh Bass straight waters along the North coast. In Tasmanian coastal waters light absorption in the water column is controlled by Coloured Dissolved Organic Matter (CDOM) with regionally varying contributions from Non-Algal Particulate (NAP) matter and phytoplankton. Absorption due to CDOM and NAP show a conservative mixing behaviour indicating that these biogeochemical components were delivered by the river and diluted in the coastal water. Suspended particulate matter in Tasmanian coastal water are highly scattering in nature and the beam attenuation is mainly due to light scattering. Variability in probability of light backscattering was mainly due to varying availability of non-algal particulate matter in

  5. Optical properties of dielectric films dispersed with metal nanoparticles and applications to optically functional materials

    NASA Astrophysics Data System (ADS)

    Wakaki, Moriaki; Yokoyama, Eisuke

    2010-12-01

    Nanoparticles of noble metals exhibit variety of colors in the visible light region due to a surface plasmon resonance. The size-induced properties of nanoparticles enable addition of flexibility to existing systems in many areas. To design a material with desired electrical and optical properties is the aim in many composite materials. In this paper, we report the preparation and characterization of silver nanoparticles in SiO2, TiO2 and ZrO2 films and gold nanoparticles in TiO2 and ZrO2 films. To analyze the dielectric characteristic of the metal-dielectric nanocomposite film, three kinds of matrices with a different refractive index were compared. Titanium dioxide (TiO2) is one of the most promising photocatalysts and actively used in various practical applications. However, only a narrow band in the ultraviolet region of solar light, about 3-4%, is available for photocatalytic reaction. Therefore, the development of TiO2 photocatalysts with higher photoelectric conversion efficiency for visible light is required. Plasmon-induced photocatalytic activity in the ultraviolet and visible light region was studied for the TiO2 thin film dispersed with gold nanoparticles. Photocatalytic activity of Au/TiO2 film was analyzed by degradation of stearic acid, and compared with non-doped TiO2film.

  6. Optical properties of dielectric films dispersed with metal nanoparticles and applications to optically functional materials

    NASA Astrophysics Data System (ADS)

    Wakaki, Moriaki; Yokoyama, Eisuke

    2011-08-01

    Nanoparticles of noble metals exhibit variety of colors in the visible light region due to a surface plasmon resonance. The size-induced properties of nanoparticles enable addition of flexibility to existing systems in many areas. To design a material with desired electrical and optical properties is the aim in many composite materials. In this paper, we report the preparation and characterization of silver nanoparticles in SiO2, TiO2 and ZrO2 films and gold nanoparticles in TiO2 and ZrO2 films. To analyze the dielectric characteristic of the metal-dielectric nanocomposite film, three kinds of matrices with a different refractive index were compared. Titanium dioxide (TiO2) is one of the most promising photocatalysts and actively used in various practical applications. However, only a narrow band in the ultraviolet region of solar light, about 3-4%, is available for photocatalytic reaction. Therefore, the development of TiO2 photocatalysts with higher photoelectric conversion efficiency for visible light is required. Plasmon-induced photocatalytic activity in the ultraviolet and visible light region was studied for the TiO2 thin film dispersed with gold nanoparticles. Photocatalytic activity of Au/TiO2 film was analyzed by degradation of stearic acid, and compared with non-doped TiO2film.

  7. Optical imaging of neural and hemodynamic brain activity

    NASA Astrophysics Data System (ADS)

    Schei, Jennifer Lynn

    Optical imaging technologies can be used to record neural and hemodynamic activity. Neural activity elicits physiological changes that alter the optical tissue properties. Specifically, changes in polarized light are concomitant with neural depolarization. We measured polarization changes from an isolated lobster nerve during action potential propagation using both reflected and transmitted light. In transmission mode, polarization changes were largest throughout the center of the nerve, suggesting that most of the optical signal arose from the inner nerve bundle. In reflection mode, polarization changes were largest near the edges, suggesting that most of the optical signal arose from the outer sheath. To overcome irregular cell orientation found in the brain, we measured polarization changes from a nerve tied in a knot. Our results show that neural activation produces polarization changes that can be imaged even without regular cell orientations. Neural activation expends energy resources and elicits metabolic delivery through blood vessel dilation, increasing blood flow and volume. We used spectroscopic imaging techniques combined with electrophysiological measurements to record evoked neural and hemodynamic responses from the auditory cortex of the rat. By using implantable optics, we measured responses across natural wake and sleep states, as well as responses following different amounts of sleep deprivation. During quiet sleep, evoked metabolic responses were larger compared to wake, perhaps because blood vessels were more compliant. When animals were sleep deprived, evoked hemodynamic responses were smaller following longer periods of deprivation. These results suggest that prolonged neural activity through sleep deprivation may diminish vascular compliance as indicated by the blunted vascular response. Subsequent sleep may allow vessels to relax, restoring their ability to deliver blood. These results also suggest that severe sleep deprivation or chronic

  8. Designing Optical Properties in DNA-Programmed Nanoparticle Superlattices

    NASA Astrophysics Data System (ADS)

    Ross, Michael Brendan

    A grand challenge of modern science has been the ability to predict and design the properties of new materials. This approach to the a priori design of materials presents a number of challenges including: predictable properties of the material building blocks, a programmable means for arranging such building blocks into well understood architectures, and robust models that can predict the properties of these new materials. In this dissertation, we present a series of studies that describe how optical properties in DNA-programmed nanoparticle superlattices can be predicted prior to their synthesis. The first chapter provides a history and introduction to the study of metal nanoparticle arrays. Chapter 2 surveys and compares several geometric models and electrodynamics simulations with the measured optical properties of DNA-nanoparticle superlattices. Chapter 3 describes silver nanoparticle superlattices (rather than gold) and identifies their promise as plasmonic metamaterials. In chapter 4, the concept of plasmonic metallurgy is introduced, whereby it is demonstrated that concepts from materials science and metallurgy can be applied to the optical properties of mixed metallic plasmonic materials, unveiling rich and tunable optical properties such as color and asymmetric reflectivity. Chapter 5 presents a comprehensive theoretical exploration of anisotropy (non-spherical) in nanoparticle superlattice architectures. The role of anisotropy is discussed both on the nanoscale, where several desirable metamaterial properties can be tuned from the ultraviolet to near-infrared, and on the mesoscale, where the size and shape of a superlattice is demonstrated to have a pronounced effect on the observed far-field optical properties. Chapter 6 builds upon those theoretical data presented in chapter 5, including the experimental realization of size and shape dependent properties in DNA-programmed superlattices. Specifically, nanoparticle spacing is explored as a parameter that

  9. Optical properties of electrochromic vanadium pentoxide

    NASA Astrophysics Data System (ADS)

    Cogan, Stuart F.; Nguyen, Nguyet M.; Perrotti, Stephen J.; Rauh, R. David

    1989-08-01

    Electrochemical and spectroscopic measurements were used to characterize the electrochromic behavior of sputtered V2O5 films. In response to lithium intercalation, the fundamental optical absorption edge of V2O5 shifts to high energies by 0.20-0.31 eV as the lithium concentration increases from Li0.0V2O5 to Li0.86V2O5. 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 cm2/C.

  10. Investigations and Mimicry of the Optical Properties of Butterfly Wings

    NASA Astrophysics Data System (ADS)

    Summers, Christopher J.; Gaillot, Davy P.; Crne, Matija; Blair, John; Park, Jung O.; Srinivasarao, Mohan; Deparis, Olivier; Welch, Victoria; Vigneron, Jean-Pol

    Structural color in Nature has been observed in plants, insects and birds, and has led to a strong interest in these phenomena and a desire to understand the mechanisms responsible. Of particular interest are the optical properties of butterflies. In this paper, we review three investigations inspired by the unique optical properties exhibited in a variety of butterfly wings. In the first investigation, conformal atomic layer depositions (ALDs) were used to exploit biologically defined 2D photonic crystal (PC) templates of Papilio blumei with the purpose of increasing the understanding of the optical effects of naturally formed dielectric architectures, and of exploring any novel optical effects. In the second study, it was demonstrated that faithful mimicry of Papilio palinurus can be achieved by physical fabrication methods through using breath figures to provide templates and ALD routines to enable optical properties. Finally, knowledge of the optical structure properties of the Princeps nireus butterfly has resulted in bioinspired designs to enhanced scintillator designs for radiation detection.

  11. Measurements of Breast Tissue Optical Properties

    DTIC Science & Technology

    2001-10-01

    Sci 1998; vol 838. 3. Heusmann H , Kblzer J, Mitic G. Characterization of female breasts inFurthermore, the use of HRT in postmenopausal women vivo by...troscopy to known biologic processes suggests that optical 5. Moesta KT, Fantini S, Jess H , et al. Contrast features of breast cancer in frequency...breast tissue. Appi Opt 1999; 38:5480-5490. In general, premenopausal breast tissue is more opti- 7. Grosenick D, Wabnitz H , Rinneberg HH, Moesta KT

  12. Nonlinear Optical Properties of Semiconducting Polymers.

    DTIC Science & Technology

    1990-01-01

    D. Moses, K. Akagi and A. J. Heeger, P 3A, 10 724 (1988). Time-Resolved Waveguide Modulation of a Conjugated Polymer, M. Sinclair, D. McBranch, D...Photoinduced Metallic State and for Photoinduced Superconductivity, Solid State Communications (in P irss). b. Papers published in Refereed Journals M...and F. Wudl, Linear and Nonlirear Optical Studies of Poly( p -phenylene- vinylene) Derivatives and Polydiacetylene 4BCMU, Synth. Met. Z2, E85 (1989) M

  13. Nonlinear Optical Properties of Semiconducting Polymers

    DTIC Science & Technology

    1990-10-26

    Materials Science and Engineering. Ed. Michael B. Bever (Pergamon Press, Oxford, 1986), p . 1399. 2 -Nonlinear Excitations and Nonlinear Phenomena in...M. Sinclair, A.J. Heeger, A. 0. Patil, S. Shi, S. Askad and F. Wudl, Linear and Nonlinear Optical Studies of Poly( p -phenylene- vinylene) Derivatives... P . Smith, ICSM 󈨜, Santa Fe, NM (June 1988) P . Smith, Organized ACS Symposium on Processing of Conducting Polymers, ACS Meeting, Dallas (April, 1989

  14. Coastal Benthic Optical Properties of Coral Environments

    DTIC Science & Technology

    1997-09-30

    remotely classify bottom types in varying water depths. APPROACH Transects over coral reef bottoms were laid out and mapped by divers and by the...team, two-ship expedition off Loggerhead Key in July, 1996. Both sites are coral reef environments within Fort Jefferson National Monument, Dry...in situ optical sensing. NOAA Coral Reef Workshop, September 16, 1996, Miami, FL. Invited. Costello, D.K., K.L. Carder and S.M. Smith. 1996

  15. Optical properties of ALON (aluminum oxynitride)

    NASA Astrophysics Data System (ADS)

    Hartnett, Thomas M.; Bernstein, Steven D.; Maguire, Edward A.; Tustison, Randal W.

    1997-06-01

    Aluminum oxynitride or ALON is a transparent polycrystalline ceramic material having high strength (380 MPa) and hardness (1950 kg/mm2). The transmission range of ALON extends from 0.2 micrometer in the UV through the visible to 6.0 micrometer in the infrared. This material is made by conventional powder processing and sintering a powder compact to full density and optical transparency. Powder compacts of near net shape and size are made by conventional dry pressing, by slip casting, and by injection molding methods. This gives the material great latitude in size and shape capabilities not afforded by materials formed by single crystal growth methods. Intrinsic transparency extending from ultraviolet wavelengths (UV) to mid-infrared wavelengths (MID-IR) and low levels of optical scatter have been achieved. In this paper recent measurements of the spectral dependence of forward optical scatter, the spectral emittance from room temperature to 1200 degrees Celsius, and the index of refraction (n) of ALON are presented. Literature values for the changes in refractive index with temperature (dn/dT) are compared.

  16. Test of spectral emission and absorption characteristics of active optical fibers by direct side pumping.

    PubMed

    Zhang, Jianzhong; Luo, Yanhua; Sathi, Zinat M; Azadpeyma, Nilram; Peng, Gang-Ding

    2012-08-27

    Emission and absorption are two main properties of active optical fibers that are important for fiber amplifiers and lasers. We propose a direct side pumping scheme for non-deconstructive evaluation of active optical fibers. This scheme enables a simple in situ test of both emission and absorption characteristics without cutting fiber and produces good accuracy with very low pumping background. A commercial Er-doped fiber and a home-made Bi/Er co-doped optical fiber have been tested to demonstrate that the scheme is a useful alternative technique for characterizing active optical fiber or waveguides.

  17. Diamagnetic Raman Optical Activity of Chlorine, Bromine, and Iodine Gases.

    PubMed

    Šebestík, Jaroslav; Kapitán, Josef; Pačes, Ondřej; Bouř, Petr

    2016-03-01

    Magnetic Raman optical activity of gases provides unique information about their electric and magnetic properties. Magnetic Raman optical activity has recently been observed in a paramagnetic gas (Angew. Chem. Int. Ed. 2012, 51, 11058; Angew. Chem. 2012, 124, 11220). In diamagnetic molecules, it has been considered too weak to be measurable. However, in chlorine, bromine and iodine vapors, we could detect a significant signal as well. Zeeman splitting of electronic ground-state energy levels cannot rationalize the observed circular intensity difference (CID) values of about 10(-4). These are explicable by participation of paramagnetic excited electronic states. Then a simple model including one electronic excited state provides reasonable spectral intensities. The results suggest that this kind of scattering by diamagnetic molecules is a general event observable under resonance conditions. The phenomenon sheds new light on the role of excited states in the Raman scattering, and may be used to probe molecular geometry and electronic structure.

  18. Scattering and Optical Properties of Water Ice

    NASA Technical Reports Server (NTRS)

    Yanamandra-Fisher, P. A.

    2003-01-01

    Light scattering by planetary ices of interest such as water, methane, clathrated species, will provide insight into the nature of the Jovian moons targeted by the JIMO mission - Europa, Callisto and Ganymede - composition, surface properties and thickness of ice mantles. Although much remote sensing data exists, theoretical models lag the data. We highlight the current state of theoretical and experimental models for water ice and highlight areas of study necessary to address the JIMO goals regarding surface and subsurface properties.

  19. Optical properties of vanadium dioxide thin film in nanoparticle structure

    NASA Astrophysics Data System (ADS)

    Fang, Baoying; Li, Yi; Tong, Guoxiang; Wang, Xiaohua; Yan, Meng; Liang, Qian; Wang, Feng; Qin, Yuan; Ding, Jie; Chen, Shaojuan; Chen, Jiankun; Zheng, Hongzhu; Yuan, Wenrui

    2015-09-01

    The thermo-optic effect and infrared optical properties of VO2 nanoparticles were studied to obtain an optical material with special property that can be used in smart windows. The reflectance and transmittance spectra of the VO2 nanoparticles with different duty cycles at different temperatures were simulated with a specific dispersion relation. Vanadium metal nanoparticles were deposited on glass substrate by magnetic reactive sputtering with porous alumina template (AAO) mask, and the VO2 nanoparticles were prepared by thermal oxidation. The nanostructure and optical properties of the VO2 nanoparticles were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and spectrophotometry. The method of preparation of the sample is economical and the phase transition temperature is observed to drop to 43 °C. The transmission at 1700 nm exhibits a variation of 29% between the metallic and semiconducting states. The VO2 nanoparticles exhibit a significant thermochromic property. The transmittance of the VO2 nanoparticles is improved compared with the VO2 film. The decrease in phase transition temperature and the enhancement of optical properties demonstrate that VO2 film in nanoparticle structure is a viable candidate material for smart windows.

  20. Optical Properties of Magnetron sputtered Nickel Thin Films

    NASA Astrophysics Data System (ADS)

    Twagirayezu, Fidele; Geerts, Wilhelmus J.; Cui, Yubo

    2015-03-01

    The study of optical properties of Nickel (Ni) is important, given the pivotal role it plays in the semiconductor and nano-electronics technology. Ni films were made by DC and RF magnetron sputtering in an ATC Orion sputtering system of AJA on various substrates. The optical properties were studied ex situ by variable angle spectroscopic (220-1000 nm) ellipsometry at room temperature. The data were modeled and analyzed using the Woollam CompleteEase Software fitting ellipsometric and transmission data. Films sputtered at low pressure have optical properties similar to that of Palik. Films sputtered at higher pressure however have a lower refraction index and extinction coefficient. It is expected from our results that the density of the sputtered films can be determined from the ellipsometric quantities. Our experiments also revealed that Ni is susceptible to a slow oxidation changing its optical properties over the course of several weeks. The optical properties of the native oxide differ from those of reactive sputtered NiO similar as found by. Furthermore the oxidation process of our samples is characterized by at least two different time constants.

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

    NASA Astrophysics Data System (ADS)

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

    1996-07-01

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

  2. Single-Crystal Silicon: Electrical and Optical Properties

    NASA Astrophysics Data System (ADS)

    Hava, Shlomo; Auslender, Mark

    Electrical and optical properties of crystalline semiconductors are important parts of pure physics and material science research. In addition, knowledge of parameters related to these properties, primarily for silicon and III-V semiconductors, has received a high priority in microelectronics and optoelectronics since the establishment of these industries. For control protocols, emphasis has recently been placed on novel optical measurement techniques, which have proved very promising as nondestructive and even non-contact methods. Earlier they required knowledge of the free-carrier-derived optical constants, related to the electrical conductivity at infrared frequencies, but interest in the optical constants of silicon in the visible, ultraviolet (UV) and soft-X-ray ranges has been revived since the critical dimensions in devices have become smaller.

  3. LSST active optics system software architecture

    NASA Astrophysics Data System (ADS)

    Thomas, Sandrine J.; Chandrasekharan, Srinivasan; Lotz, Paul; Xin, Bo; Claver, Charles; Angeli, George; Sebag, Jacques; Dubois-Felsmann, Gregory P.

    2016-08-01

    The Large Synoptic Survey Telescope (LSST) is an 8-meter class wide-field telescope now under construction on Cerro Pachon, near La Serena, Chile. This ground-based telescope is designed to conduct a decade-long time domain survey of the optical sky. In order to achieve the LSST scientific goals, the telescope requires delivering seeing limited image quality over the 3.5 degree field-of-view. Like many telescopes, LSST will use an Active Optics System (AOS) to correct in near real-time the system aberrations primarily introduced by gravity and temperature gradients. The LSST AOS uses a combination of 4 curvature wavefront sensors (CWS) located on the outside of the LSST field-of-view. The information coming from the 4 CWS is combined to calculate the appropriate corrections to be sent to the 3 different mirrors composing LSST. The AOS software incorporates a wavefront sensor estimation pipeline (WEP) and an active optics control system (AOCS). The WEP estimates the wavefront residual error from the CWS images. The AOCS determines the correction to be sent to the different degrees of freedom every 30 seconds. In this paper, we describe the design and implementation of the AOS. More particularly, we will focus on the software architecture as well as the AOS interactions with the various subsystems within LSST.

  4. Properties and applications of polymers in optics and electro-optics

    NASA Astrophysics Data System (ADS)

    Dubois, Jean-Claude; Robin, Philippe; Dentan, Veronique

    1993-12-01

    This paper describes the properties and applications of some recent polymers in the field of electro-optics. We describe the properties of polyacrylates copolymer with a pending group with large hyperpolarizability. These amorphous copolymers show high optical nonlinear coefficients after poling under an electric field. We have used these copolymers for the manufacture of an electro-optic modulator working at 1.3 micrometers at a frequency of 1 GHz. We also look at the nonlinear absorption of the C60 fullerene for applications in the field of optical limiting. Finally, we deal with ferroelectric polymers and their pyroelectric properties. We describe the realization and performance of an IR pyroelectric sensor using copolymers of poly(vinylidene fluoride-ethylene trifluoride).

  5. Analysis of temperature and thermo-optical properties in optical materials. 1: Cylindrical geometry

    NASA Astrophysics Data System (ADS)

    Tilleman, Michael M.

    2010-11-01

    Modeling of optical and electro-optical devices requires the implementation of material properties over a broad temperature range. Because optical, thermo-optical, elasto-optical and gain properties of solid-state laser materials depend on temperature, their exact magnitude is needed for designing such optical devices. Derived in this paper is a closed form solution to the problems of nonlinear heat transfer and stress field, resulting in expressions for the local temperature, stress and strain, refractive index, trajectories of propagating rays, optical path difference, thermal lensing, tilt and third order aberrations, induced birefringence and depolarization. In the analysis the temperature dependent coefficients were best fitted to existing experimental data. Some examples are presented for thermally induced optical effects in solid-state laser gain-media in the temperature range of 77-770 K. It is found that: for large heat deposition rates the use of the nonlinear solution is uniquely necessary to assess the thermal and optical characteristics, high pumping loads require cryogenic cooling to maintain low thermal lensing and thermally induced dioptric power depends quadratically on the heat rate.

  6. Optical Recording Reveals Novel Properties of GSK1016790A-Induced Vanilloid Transient Receptor Potential Channel TRPV4 Activity in Primary Human Endothelial Cells

    PubMed Central

    Sullivan, Michelle N.; Francis, Michael; Pitts, Natalie L.; Taylor, Mark S.

    2012-01-01

    Critical functions of the vascular endothelium are regulated by changes in intracellular [Ca2+]. Endothelial dysfunction is tightly associated with cardiovascular disease, and improved understanding of Ca2+ entry pathways in these cells will have a significant impact on human health. However, much about Ca2+ influx channels in endothelial cells remains unknown because they are difficult to study using conventional patch-clamp electrophysiology. Here we describe a novel, highly efficient method for recording and analyzing Ca2+-permeable channel activity in primary human endothelial cells using a unique combination of total internal reflection fluorescence microscopy (TIRFM), custom software-based detection, and selective pharmacology. Our findings indicate that activity of the vanilloid (V) transient receptor potential (TRP) channel TRPV4 can be rapidly recorded and characterized at the single-channel level using this method, providing novel insight into channel function. Using this method, we show that although TRPV4 protein is evenly distributed throughout the plasma membrane, most channels are silent even during maximal stimulation with the potent TRPV4 agonist N-((1S)-1-{[4-((2S)-2-{[(2,4-dichlorophenyl)sulfonyl]amino}-3-hydroxypropanoyl)-1-piperazinyl]carbonyl}-3-methylbutyl)-1-benzothiophene-2-carboxamide (GSK1016790A). Furthermore, our findings indicate that GSK1016790A acts by recruiting previously inactive channels, rather than through increasing elevation of basal activity. PMID:22689561

  7. 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.

  8. Structural Stability and Optical Properties of Nanomaterials with Reconstructed Surfaces

    SciTech Connect

    Puzder, A; Williamson, A; Reboredo, F; Galli, G

    2003-10-24

    The authors present density functional and quantum Monte Carlo calculations of the stability and optical properties of semiconductor nanomaterials with reconstructed surfaces. they predict the relative stability of silicon nanostructures with reconstructed and unreconstructed surfaces, and show that surface step geometries unique to highly curved surfaces dramatically reduce the optical gaps and decrease excitonic lifetimes. These predictions provide an explanation of both the variations in the photoluminescence spectra of colloidally synthesized nanoparticles and observed deep gap levels in porous silicon.

  9. Morphology effects on the optical properties of silver nanoparticles.

    PubMed

    Chen, Sihai; Webster, Scott; Czerw, Richard; Xu, Jianfeng; Carroll, David L

    2004-03-01

    Employing methods developed for the control of shape and size in silver nanoparticles, we have compared the optical properties of nanorods, nanoprisms, nanodisks, and nanospheres. Solutions of these particles show distinct surface plasmon resonant absorption signatures that are directly correlated with the symmetries of their morphology. Nonlinear optical behavior for suspensions of these nanostructures, for nanosecond pulses at 532 and 1064 nm, have been correlated to plasmon resonances determined by shape and size.

  10. Study on the creep properties of distributed optical fiber sensors

    NASA Astrophysics Data System (ADS)

    Song, Shiwei; Yang, Caiqian; Wu, Zhishen; Zhang, Yufeng; Shen, Sheng

    2010-04-01

    In this paper, based on the distributed optical fiber strain sensing technology of pulse-pre-pump Brillouin Optical Time Domain Analysis (PPP-BOTDA), the creep properties of two types of optical fiber sensors, i.e. single mode optical fiber with jacket (Type-A) and optical fiber with UV resin coating (Type-B), were studied at different load (60g~600g) amplitudes. Experimental results show that there exists some creep for both types in initial loading period and tend to level off with time. But for Type-B, the strain variation is 5% of initial strain, and the stabilization time is about 48h, both of which are obviously smaller than those of Type-A. As a result, it is revealed that Type-B is characterized by a smaller creep, suitable for the long-term monitoring of infrastructures.

  11. Thermo-optical properties and nonlinear optical response of smectic liquid crystals containing gold nanoparticles.

    PubMed

    de Melo, P B; Nunes, A M; Omena, L; do Nascimento, S M S; da Silva, M G A; Meneghetti, M R; de Oliveira, I N

    2015-10-01

    The present work is devoted to the study of the thermo-optical and nonlinear optical properties of smectic samples containing gold nanoparticles with different shapes. By using the time-resolved Z-scan technique, we determine the effects of nanoparticle addition on the critical behavior of the thermal diffusivity and thermo-optical coefficient at the vicinity of the smectic-A-nematic phase transition. Our results reveal that introduction of gold nanoparticles affects the temperature dependence of thermo-optical parameters, due to the local distortions in the orientational order and heat generation provided by guest particles during the laser exposure. Further, we show that a nonlinear optical response may take place at temperatures where the smectic order is well established. We provide a detailed discussion of the effects associated with the introduction gold nanoparticles on the mechanisms behind the thermal transport and optical nonlinearity in liquid-crystal samples.

  12. An investigation of aerosol optical properties: Atmospheric implications and influences

    NASA Astrophysics Data System (ADS)

    Penaloza-Murillo, Marcos A.

    An experimental, observational, and theoretical investigation of aerosol optical properties has been made in this work to study their implications and influences on the atmosphere. In the laboratory the scientific and instrumental methodology consisted of three parts, namely, aerosol generation, optical and mass concentration measurements, and computational calculations. In particular the optical properties of ammonium sulfate and caffeine aerosol were derived from measurements made with a transmissometer cell-reciprocal- integrating nephelometer (TCRIN), equipped with a laser beam at 632.8 nm, and by applying a Mie theory computer code The aerosol generators, optical equipment and calibration procedures were reviewed. The aerosol shape and size distribution were studied by means of scanning electron microscopy and the Gumprecht- Sliepcevich/Lipofsky-Green extinction-sedimentation method. In particular the spherical and cylindrical shape were considered. During this investigation, an alternative method for obtaining the optical properties of monodisperse spherical non-absorbing aerosol using a cell-transmissometer, which is based on a linearisation of the Lambert-Beer law, was found. In addition, adapting the TCRIN to electrooptical aerosol studies, the optical properties of a circular-cylindrical aerosol of caffeine were undertaken under the condition of random orientation in relation with the laser beam, and perpendicular orientation to it. A theoretical study was conducted to assess the sensitivity of aerosol to a change of shape under different polarisation modes. The aerosol optical properties, obtained previously in the laboratory, were then used to simulate the direct radiative forcing. The calculations and results were obtained by applying a one- dimensional energy-balance box model. The influence of atmospheric aerosol on the sky brightness due to a total solar eclipse was studied using the photometric and meteorological observations made during the

  13. Consequence of doping mediated strain and the activation energy on the structural and optical properties of ZnO:Cr nanoparticles

    SciTech Connect

    Bhargava, Richa; Sharma, Prashant K.; Kumar, Sanjeev; Pandey, Avinash C.; Kumar, Naresh

    2010-06-15

    We report on the sol-gel synthesis of Zn{sub 1-x}Cr{sub x}O (x=0.0, 0.05, 0.10, 0.15 and 0.20) nanoparticles. These nanoparticles were characterized by using thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman and Photoluminescence (PL). Electronegativity of Cr ions (Cr{sup 3+}) reduces the final decomposition temperature by 40 {sup o}C and activation energy of the reaction when Cr is doped into ZnO. Doping of higher Cr concentration (x{>=}0.10) into ZnO shows formation of secondary spinel (ZnCr{sub 2}O{sub 4}) phase along with the hexagonal (ZnO) and is revealed by XRD. Formation of secondary phase changes the activation energy of the reaction and thus the strain in ZnO lattice. In Raman spectra, additional Raman modes have been observed for Zn{sub 1-x}Cr{sub x}O nanoparticles, which can be assigned to the modes generated due to Cr doping. The Cr doping into ZnO is also supported by PL, in which vacancies are formed with Cr ion incorporation and emission band shifts towards higher wavelength. - Graphical abstract: Cr-doped ZnO nanostructures were synthesized by sol-gel. XRD (a) revealed secondary phase of ZnCr{sub 2}O{sub 4} with increase in Cr concentration. The Cr concentration also changes activation energy of the reaction (b).

  14. Plasmonic Biofoam: A Versatile Optically Active Material.

    PubMed

    Tian, Limei; Luan, Jingyi; Liu, Keng-Ku; Jiang, Qisheng; Tadepalli, Sirimuvva; Gupta, Maneesh K; Naik, Rajesh R; Singamaneni, Srikanth

    2016-01-13

    Owing to their ability to confine and manipulate light at the nanoscale, plasmonic nanostructures are highly attractive for a broad range of applications. While tremendous progress has been made in the synthesis of size- and shape-controlled plasmonic nanostructures, their integration with other materials and application in solid-state is primarily through their assembly on rigid two-dimensional (2D) substrates, which limits the plasmonically active space to a few nanometers above the substrate. In this work, we demonstrate a simple method to create plasmonically active three-dimensional biofoams by integrating plasmonic nanostructures with highly porous biomaterial aerogels. We demonstrate that plasmonic biofoam is a versatile optically active platform that can be harnessed for numerous applications including (i) ultrasensitive chemical detection using surface-enhanced Raman scattering; (ii) highly efficient energy harvesting and steam generation through plasmonic photothermal heating; and (iii) optical control of enzymatic activity by triggered release of biomolecules encapsulated within the aerogel. Our results demonstrate that 3D plasmonic biofoam exhibits significantly higher sensing, photothermal, and loading efficiency compared to conventional 2D counterparts. The design principles and processing methodology of plasmonic aerogels demonstrated here can be broadly applied in the fabrication of other functional foams.

  15. Synthesis and Properties of a Novel Pyridineoxazoline Containing Optically Active Helical Polymer as a Catalyst Ligand for Asymmetric Diels-Alder Reaction.

    PubMed

    Wang, Heng; Li, Na; Zhang, Jie; Wan, Xinhua

    2015-08-01

    A novel pyridineoxazoline (PyOx) containing helical polymer, poly{(-)-(S)-4-tert-butyl-2-[5-(4-tert-butylphenyl)-3-vinylpyridin-2-yl]-oxazoline} (PA), was designed and synthesized to approach the effect of chain conformation on the catalytic property. Its complex with Cu(OTf)(2) , i.e., Cu(II)-PA, was employed to catalyze the homogeneous Diels-Alder (D-A) reaction of alkenoyl pyridine N-oxides with cyclopentadiene in tetrahydrofuran. Compared with the previously reported copper complex, Cu(II)-P1 (RSC Advances, 2015, 5, 2882), which was derived from a nonhelical poly[(-)-(S)-4-tert-butyl-2-(3-vinylpyridin-2-yl)-oxazoline], Cu(II)-PA exhibited a remarkably enhanced enantioselectivity and reaction rate. However, its enantioselectivity was lower than the Cu(II) complex of (-)-(S)-4-tert-butyl-2-[5-(4-tert-butylphenyl)-3-vinylpyridin-2-yl]-oxazoline (Cu(II)-A), a low molar mass model compound.

  16. Optical properties of the mouse eye

    PubMed Central

    Geng, Ying; Schery, Lee Anne; Sharma, Robin; Dubra, Alfredo; Ahmad, Kamran; Libby, Richard T.; Williams, David R.

    2011-01-01

    The Shack-Hartmann wavefront sensor (SHWS) spots upon which ocular aberration measurements depend have poor quality in mice due to light reflected from multiple retinal layers. We have designed and implemented a SHWS that can favor light from a specific retinal layer and measured monochromatic aberrations in 20 eyes from 10 anesthetized C57BL/6J mice. Using this instrument, we show that mice are myopic, not hyperopic as is frequently reported. We have also measured longitudinal chromatic aberration (LCA) of the mouse eye and found that it follows predictions of the water-filled schematic mouse eye. Results indicate that the optical quality of the mouse eye assessed by measurement of its aberrations is remarkably good, better for retinal imaging than the human eye. The dilated mouse eye has a much larger numerical aperture (NA) than that of the dilated human eye (0.5 NA vs. 0.2 NA), but it has a similar amount of root mean square (RMS) higher order aberrations compared to the dilated human eye. These measurements predict that adaptive optics based on this method of wavefront sensing will provide improvements in retinal image quality and potentially two times higher lateral resolution than that in the human eye. PMID:21483598

  17. Using electron microscopy to calculate optical properties of biological samples.

    PubMed

    Wu, Wenli; Radosevich, Andrew J; Eshein, Adam; Nguyen, The-Quyen; Yi, Ji; Cherkezyan, Lusik; Roy, Hemant K; Szleifer, Igal; Backman, Vadim

    2016-11-01

    The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy factor g, the phase function and the shape factor D of the nuclei are calculated. The results show strong agreement with an independent study. This method provides a new way to extract the true phase function of biological samples and provides an independent validation for optical property measurement techniques.

  18. Dependence of optical properties of calcium bismuthates on synthesis conditions

    NASA Astrophysics Data System (ADS)

    Shtarev, D. S.; Shtareva, A. V.

    2016-08-01

    The article studies optical properties of calcium bismuthate nanoparticles of different composition. For the first time the synthesis of these compounds was produced by the pyrolysis of organic precursors using an organic solvent. Characterization of particles was made by scanning electron microscopy and X-ray analysis. The optical properties were investigated by diffuse reflectance spectroscopy (DRS). It is shown that the type of crystal lattice of the particles of calcium bismuthate determines the possibility to control the optical properties of nanoparticles by varying their composition. The conclusions about the production process and the composition of calcium bismuthate, the most promising for use as a photocatalyst of visible light and solar cells, were made.

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

    PubMed

    Wilcoxon, Jess

    2009-03-05

    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.

  20. Measuring the optical properties of IceCube drill holes

    NASA Astrophysics Data System (ADS)

    Rongen, Martin

    2016-04-01

    The IceCube Neutrino Observatory consists of 5160 digital optical modules (DOMs) in a cubic kilometer of deep ice below the South Pole. The DOMs record the Cherenkov light from charged particles interacting in the ice. A good understanding of the optical properties of the ice is crucial to the quality of the event reconstruction. While the optical properties of the undisturbed ice are well understood, the properties of the refrozen drill holes still pose a challenge. A new data-acquisition and analysis approach using light originating from LEDs within one DOM detected by the photomultiplier of the same DOM will be described. This method allows us to explore the scattering length in the immediate vicinity of the considered DOMs.

  1. Origin of Interplanetary Dust through Optical Properties of Zodiacal Light

    NASA Astrophysics Data System (ADS)

    Yang, Hongu; Ishiguro, Masateru

    2015-11-01

    This study investigates the origin of interplanetary dust particles (IDPs) through the optical properties, albedo and spectral gradient, of zodiacal light. The optical properties were compared with those of potential parent bodies in the solar system, which include D-type (as analogs of cometary nuclei), C-type, S-type, X-type, and B-type asteroids. We applied Bayesian inference to the mixture model composed of the distribution of these sources, and found that >90% of the IDPs originate from comets (or their spectral analogs, D-type asteroids). Although some classes of asteroids (C-type, X-type, and B-type) may make a moderate contribution, ordinary chondrite-like particles from S-type asteroids occupy a negligible fraction of the interplanetary dust cloud complex. The overall optical properties of the zodiacal light were similar to those of chondritic porous IDPs, supporting the dominance of cometary particles in the zodiacal cloud.

  2. Optical properties of single-layer and bilayer arsenene phases

    NASA Astrophysics Data System (ADS)

    Kecik, D.; Durgun, E.; Ciraci, S.

    2016-11-01

    An extensive investigation of the optical properties of single-layer buckled and washboard arsenene and their bilayers was performed, starting from layered three-dimensional crystalline phase of arsenic using density functional and many-body perturbation theories combined with random phase approximation. Electron-hole interactions were taken into account by solving the Bethe-Salpeter equation, suggesting first bound exciton energies on the order of 0.7 eV. Thus, many-body effects were found to be crucial for altering the optical properties of arsenene. The light absorption of single-layer and bilayer arsenene structures in general falls within the visible-ultraviolet spectral regime. Moreover, directional anisotropy, varying the number of layers, and applying homogeneous or uniaxial in-plane tensile strain were found to modify the optical properties of two-dimensional arsenene phases, which could be useful for diverse photovoltaic and optoelectronic applications.

  3. Using electron microscopy to calculate optical properties of biological samples

    PubMed Central

    Wu, Wenli; Radosevich, Andrew J.; Eshein, Adam; Nguyen, The-Quyen; Yi, Ji; Cherkezyan, Lusik; Roy, Hemant K.; Szleifer, Igal; Backman, Vadim

    2016-01-01

    The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy factor g, the phase function and the shape factor D of the nuclei are calculated. The results show strong agreement with an independent study. This method provides a new way to extract the true phase function of biological samples and provides an independent validation for optical property measurement techniques. PMID:27896013

  4. Optical Writing of Magnetic Properties by Remanent Photostriction.

    PubMed

    Iurchuk, V; Schick, D; Bran, J; Colson, D; Forget, A; Halley, D; Koc, A; Reinhardt, M; Kwamen, C; Morley, N A; Bargheer, M; Viret, M; Gumeniuk, R; Schmerber, G; Doudin, B; Kundys, B

    2016-09-02

    We present an optically induced remanent photostriction in BiFeO_{3}, resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO_{3}/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO_{3}. Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.

  5. Optical Writing of Magnetic Properties by Remanent Photostriction

    NASA Astrophysics Data System (ADS)

    Iurchuk, V.; Schick, D.; Bran, J.; Colson, D.; Forget, A.; Halley, D.; Koc, A.; Reinhardt, M.; Kwamen, C.; Morley, N. A.; Bargheer, M.; Viret, M.; Gumeniuk, R.; Schmerber, G.; Doudin, B.; Kundys, B.

    2016-09-01

    We present an optically induced remanent photostriction in BiFeO3 , resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO3/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO3 . Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.

  6. Shear ordered diblock copolymers with tuneable optical properties.

    PubMed

    Parnell, Andrew J; Tzokova, Nadejda; Pryke, Andrew; Howse, Jonathan R; Mykhaylyk, Oleksandr O; Ryan, Anthony J; Panine, Pierre; Fairclough, J Patrick A

    2011-02-28

    A series of high molecular weight poly(styrene-b-isoprene) block copolymers with optical properties defined by composition in a non-selective solvent were studied using simultaneous ultra small angle X-ray scattering (USAXS) and optical spectrometry. A small magnitude shear produces ordered and oriented states in the copolymer solutions that persist for extended periods of time, and also have superior optical properties that are directly attributable to the mesoscopic block copolymer (BCP) morphology. We have demonstrated that the optical transmission of these materials can be tuned by the addition of low molecular weight poly(isoprene) and poly(styrene) to swell their respective domains within the diblock copolymer. The optical transmission peak for the diblocks could be tuned; from 380 nm-440 nm for the 670k diblock, 425 nm-540 nm for the 850k diblock and 541 nm-625 nm for the 1 million diblock by altering the solution concentration and composition. The full width at half maximum that can be achieved for the optical transmission peaks is as small as 15 nm at 473 nm with a Δλ/λ of 0.03, highlighting the high quality ordering in these systems. Also a small shift in the transmission peak wavelength was observed across a wide angle of view (15 nm at 30°) suggesting that these materials could be used for large area narrow band optical filters.

  7. Optical, magnetic and electronic properties of graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Guclu, A. Devrim

    2011-03-01

    We present a theory of optical, magnetic and electronic properties of graphene quantum dots. We demonstrate that there exists a class of triangular graphene quantum dots with zigzag edges [1-8] which combines magnetic, optical and transport properties in a single-material structure. These dots exhibit robust magnetic moment and optical transitions simultaneously in the THz, visible and UV spectral ranges due to the existence of a band of degenerate states lying at the Fermi level in the middle of the energy gap [1-6]. The magnetic and optical properties[5,7] are determined by strong electron-electron and excitonic interactions in the degenerate band, treated exactly using numerical techniques combining tight-binding, DFT, Hartree-Fock and configuration interactions methods. We show that the spin polarized degenerate band leads to quenching of the absorption spectrum at half-filling, while addition of a single electron fully depolarizes all electron spins and turns the absorption on. It is thus possible to design gate and size tunable graphene quantum dots with desired optical and magnetic properties for optoelectronic and photo-voltaic applications. Collaborators: P. Potasz, O. Voznyy, M. Korkusinski, and P. Hawrylak. The author thanks NRC-CNRS CRP, Canadian Institute for Advanced Research, Institute for Microstructural Sciences, and QuantumWorks for support.

  8. Nonlocal optical properties in periodic lattice of graphene layers.

    PubMed

    Chern, Ruey-Lin; Han, Dezhuan

    2014-02-24

    Based on the effective medium model, nonlocal optical properties in periodic lattice of graphene layers with the period much less than the wavelength are investigated. Strong nonlocal effects are found in a broad frequency range for TM polarization, where the effective permittivity tensor exhibits the Lorentzian resonance. The resonance frequency varies with the wave vector and coincides well with the polaritonic mode. Nonlocal features are manifest on the emergence of additional wave and the occurrence of negative refraction. By examining the characters of the eigenmode, the nonlocal optical properties are attributed to the excitation of plasmons on the graphene surfaces.

  9. Tuning nonlinear optical absorption properties of WS2 nanosheets

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  10. Midinfrared optical properties of petroleum oil aerosols

    NASA Astrophysics Data System (ADS)

    Gurton, K. P.; Bruce, C. W.

    1994-08-01

    The mass normalized absorption and extinction coefficients were measured for fog oil aerosol at 3.4 micrometers with a combined photoacoustic and transmissometer system. An extinction spectral profile was determined over a range of infrared (IR) wavelengths from 2.7 to 4.0 micrometers by an IR scanning transmissometer. The extinction spectrum was mass normalized by referencing it to the photoacoustic portion of the experiment. A corresponding Mie calculation was conducted and compared with the above measurements. Agreement is good for the most recent optical coefficients. An extrapolation of this data to other similar petroleum products such as kerosene or diesel fuel that exhibit similar bulk absorption characteristics were briefly examined.

  11. Simulation of integrated optical network (IPON) properties

    NASA Astrophysics Data System (ADS)

    Siska, Petr; Koudelka, Petr; Latal, Jan; Vitasek, Jan; Kepak, Stanislav; Vašinek, Vladimír.

    2014-09-01

    There is an increasing pressure nowadays on the efficient use of existing ICT infrastructure in order to provide the latest services for corporate customers or end users. With the increase in number of services, requirements for optical networks of all hierarchies are increasing as well. This increase in the requirements, however, involves risks which must be faced by Internet service providers. These include the maximum use of spectral range, bandwidth and reachable distance, suppression of dispersion effect, route planning efficiency, CAPEX and OPEX costs management, or successful combination of technologies of deployed networks. The aim of this article is to present the problems associated with interconnection of WDM-PON and ver.2 EPON (IEEE 802.3ah standard). The entire simulation is based on real parameters, which were provided by the manufacturers of the technologies and then measured in the laboratory. Then we were able to perform simulations based on more realistic features of these technologies.

  12. Development of a noncontact diffuse optical spectroscopy probe for measuring tissue optical properties

    PubMed Central

    Bish, Sheldon F.; Rajaram, Narasimhan; Nichols, Brandon; Tunnell, James W.

    2011-01-01

    Optical reflectance probes are often used as tools to obtain optical spectra from superficial tissues and subsequently determine optical and physiological properties associated with early stage cancer. These probes, when placed directly on the tissue, are known to cause significant pressure-dependent changes in local optical properties. To address this, we fit the probe with an optical device that images the illumination and collection fibers onto the tissue surface, eliminating the influence of contact probe pressure on the sampling area. The noncontact probe addition addresses new optical conditions that may affect its performance such as tissue surface contour, and specular reflections by implementing an autofocusing mechanism and cross polarization. Extracted optical properties of tissue simulating phantoms yield errors of 3.46% in reduced scattering and 8.62% in absorbance. Autofocusing has extended the depth of field from 4 mm to throughout the 12 mm range of autofocus travel, while cross polarization has removed the incidence angle dependent specular reflection component from the collected signal. PMID:22191909

  13. Nickel-doped zinc aluminate oxides: starch-assisted synthesis, structural, optical properties, and their catalytic activity in oxidative coupling of methane

    NASA Astrophysics Data System (ADS)

    Visinescu, Diana; Papa, Florica; Ianculescu, Adelina C.; Balint, Ioan; Carp, Oana

    2013-03-01

    Nanosized nickel-substituted zinc aluminate oxides were obtained by the gradual insertion of nickel cations within the zinc aluminate lattice, using starch as active ingredient. The obtained (Ni x Zn1- x Al2)-starch ( x = 0.1, 0.2, 0.4, 0.6, 0.8, 1) gel precursors were characterized through infrared spectroscopy and thermal analysis. The thermal behavior of the precursors are influenced by the nickel content, the DTA curves for the richer nickel samples revealing stronger, faster and overlapping exothermic reactions, that can be completed at lower temperatures. The corresponding spinelic oxides were obtained after calcination treatments at 800 °C and analyzed by means of NIR-UV-Vis spectroscopy, XRD measurements, SEM, TEM, and HRTEM investigations. The spinelic structure for all oxide samples is confirmed by XRD analysis, although small amounts of NiO cannot be neglected. TEM/HRTEM analysis revealed mesopores embedded in plate-like large (68.8 nm) particles of Ni0.2Zn0.8Al2O4 sample and smaller (15.7 nm) uniform equiaxial particles, with a more pronounced tendency of agglomeration for Ni0.8Zn0.2Al2O4 oxide. A formation mechanism for Ni0.2Zn0.8Al2O4 oxides was proposed based on DTA/TG, XRD, and SEM analyses. NIR-UV-Vis spectra for Ni x Zn1- x Al2O4 showed a significant presence of tetrahedral nickel cations that augments with nickel concentration increase. CIE- L * a * b * color parameters shown a variation of the lightness and also of the green and blue color components with x, the best color characteristics being obtained for x = 0.6. The oxides with a substitution degree x = 0.2 and 0.8 tested in the oxidative coupled of methane reaction (OCM) showed positive catalytic activity and selectivity due to an interesting synergetic effect of Zn(II) and Ni(II) ions.

  14. Optical and vibrational properties of single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kennedy, W. Joshua

    This work is a study of the optical properties of single-wall carbon nanotubes (SWNTs) using continuous wave (CW) modulation spectroscopy and resonant Raman scattering. SWNTs comprise a nanoscale, quasi-1D system in which the electrons are strongly interacting, resulting in the photo-generation of excitons. Our optical studies have revealed the behavior of these excitons under a number of different perturbations to the system. We have used absorption, reflectance, electro-absorption (EA), photo-induced absorption (PA), charge-induced absorption (CIA), and resonant Raman scattering (RRS) on films of SWNTs. Our EA results provide strong evidence for the dominance of excitons in the optical absorption spectra of SWNT films. The absence of Franz-Keldysh oscillations and the presence of a derivative-like structure of the EA spectra indicate that the oscillator strength goes to the generation of excitons and not to interband electronic transitions. Furthermore, some of the photo-generated excitons are long-lived due to charge trapping in individual tubes within bundles, and this leads to a PA spectrum that is extraordinarily similar to the EA signal. When SWNTs are electrochemically doped we see that the exciton absorption is bleached due to k-space filling and screening of the excitons by the modified local dielectric, while there is very little shift in the exciton transition energies due to band-gap renormalization. Simultaneously the infrared absorption, which is due to Drude free-carriers absorption, is enhanced. A similar behavior is observed in the case of direct charge injection. The RRS of doped SWNT samples shows a frequency shift of many of the Raman-active modes that is commensurate with the macroscopic actuation observed in nanotube-based electrochemical devices. This indicates that doping-induced changes in the lattice are connected with softening and stiffening of the vibrational modes. Our results impact many proposed technologies that exploit the unique

  15. Processing, properties, and applications of sol-gel silica optics

    NASA Astrophysics Data System (ADS)

    Nogues, Jean-Luc R.; LaPaglia, Anthony J.

    1989-12-01

    For many years the market share maintained by U.S. optics manufacturers has been declining continuously caused in part by intense competition principally from countries in the Far East, and in part by the lack of a highly trained cadre of opticians to replace the current generation. This fact could place in jeopardy the defense system of the United States in case of international war. For example, in 1987, optical glass component imports accounted for approximately 50 percent of the Department of Defense (DOD) consumption. GELTECH's sol-gel technology is a new process for making a high quality optical glass and components for commercial and military uses. This technology offers in addition to being a local source of optics, the possibility to create new materials for high-tech optical applications, and the elimination of the major part of grinding and polishing for which the skill moved off-shore. This paper presents a summary of the solgel technology for the manufacture of high quality optical glass and components. Properties of pure silica glass made by solgel process (Type V and Type VI silicas) are given and include: ultraviolet, visible and near infrared spectrophotometry, optical homogeneity and thermal expansion. Many applications such as near net shape casting or Fresnel lens surface replication are discussed. Several potential new applications offered by the solgel technology such as organic-inorganic composites for non linear optics or scintillation detection are also reported in this paper.

  16. Optical Activity of Anisotropic Achiral Surfaces

    SciTech Connect

    Verbiest, T.; Kauranen, M.; Van Rompaey, Y.; Persoons, A. |

    1996-08-01

    Anisotropic achiral surfaces respond differently to left- and right-hand circularly polarized light. This occurs when the orientation of the surface with respect to an otherwise achiral experimental setup makes the total geometry chiral. Such optical activity is demonstrated in second-harmonic generation from an anisotropic thin molecular film. The circular-difference response reverses sign as the handedness of the geometry is reversed and vanishes when the setup possesses a mirror plane. The results are explained within the electric-dipole-allowed second-order surface nonlinearity. {copyright} {ital 1996 The American Physical Society.}

  17. Computational Study of Linear and Nonlinear Optical Properties of Single Molecules and Clusters of Organic Electro-Optic Chromophores

    NASA Astrophysics Data System (ADS)

    Garrett, Kerry

    Organic electro-optic (OEO) materials integrated into silicon-organic hybrid (SOH) devices afford significant improvements in size, weight, power, and bandwidth (SWAP) performance of integrated electronic/photonic systems critical for current and next generation telecommunication, computer, sensor, transportation, and defense technologies. Improvement in molecular first hyperpolarizability, and in turn electro-optic activity, is crucial to further improvement in the performance of SOH devices. The timely preparation of new chromophores with improved molecular first hyperpolarizability requires theoretical guidance; however, common density functional theory (DFT) methods often perform poorly for optical properties in systems with substantial intramolecular charge transfer character. The first part of this dissertation describes the careful evaluation of popular long-range correction (LC) and range-separated hybrid (RSH) density functional theory (DFT) for definition of structure/function relationships crucial for the optimization of molecular first hyperpolarizability, beta. In particular, a benchmark set of well-characterized OEO chromophores is used to compare calculated results with the corresponding experimentally measured linear and nonlinear optical properties; respectively, the wavelength of the peak one-photon absorption energy, lambdamax, and beta. A goal of this work is to systematically determine the amount of exact exchange in LC/RSH-DFT methods required for accurately computing these properties for a variety OEO chromophores. High-level electron correlation (post-Hartree-Fock) methods are also investigated and compared with DFT. Included are results for the computation of beta using second-order Moller-Plesset perturbation theory (MP2) and the double-hybrid method, B2PLYP. The second part of this work transitions from single-molecule studies to computing bulk electronic and nonlinear optical properties of molecular crystals and isotropic ensembles of a

  18. Active full-shell grazing-incidence optics

    NASA Astrophysics Data System (ADS)

    Roche, Jacqueline M.; Elsner, Ronald F.; Ramsey, Brian D.; O'Dell, Stephen L.; Kolodziejczak, Jeffrey J.; Weisskopf, Martin C.; Gubarev, Mikhail V.

    2016-09-01

    MSFC has a long history of developing full-shell grazing-incidence x-ray optics for both narrow (pointed) and wide field (surveying) applications. The concept presented in this paper shows the potential to use active optics to switch between narrow and wide-field geometries, while maintaining large effective area and high angular resolution. In addition, active optics has the potential to reduce errors due to mounting and manufacturing lightweight optics. The design presented corrects low spatial frequency error and has significantly fewer actuators than other concepts presented thus far in the field of active x-ray optics. Using a finite element model, influence functions are calculated using active components on a full-shell grazing-incidence optic. Next, the ability of the active optic to effect a change of optical prescription and to correct for errors due to manufacturing and mounting is modeled.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  20. Optical measurement of arterial mechanical properties: from atherosclerotic plaque initiation to rupture

    PubMed Central

    2013-01-01

    Abstract. During the pathogenesis of coronary atherosclerosis, from lesion initiation to rupture, arterial mechanical properties are altered by a number of cellular, molecular, and hemodynamic processes. There is growing recognition that mechanical factors may actively drive vascular cell signaling and regulate atherosclerosis disease progression. In advanced plaques, the mechanical properties of the atheroma influence stress distributions in the fibrous cap and mediate plaque rupture resulting in acute coronary events. This review paper explores current optical technologies that provide information on the mechanical properties of arterial tissue to advance our understanding of the mechanical factors involved in atherosclerosis development leading to plaque rupture. The optical approaches discussed include optical microrheology and traction force microscopy that probe the mechanical behavior of single cell and extracellular matrix components, and intravascular imaging modalities including laser speckle rheology, optical coherence elastography, and polarization-sensitive optical coherence tomography to measure the mechanical properties of advanced coronary lesions. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in elucidating the mechanical aspects of coronary atherosclerosis in the future. PMID:24296995

  1. Optical measurement of arterial mechanical properties: from atherosclerotic plaque initiation to rupture

    NASA Astrophysics Data System (ADS)

    Nadkarni, Seemantini K.

    2013-12-01

    During the pathogenesis of coronary atherosclerosis, from lesion initiation to rupture, arterial mechanical properties are altered by a number of cellular, molecular, and hemodynamic processes. There is growing recognition that mechanical factors may actively drive vascular cell signaling and regulate atherosclerosis disease progression. In advanced plaques, the mechanical properties of the atheroma influence stress distributions in the fibrous cap and mediate plaque rupture resulting in acute coronary events. This review paper explores current optical technologies that provide information on the mechanical properties of arterial tissue to advance our understanding of the mechanical factors involved in atherosclerosis development leading to plaque rupture. The optical approaches discussed include optical microrheology and traction force microscopy that probe the mechanical behavior of single cell and extracellular matrix components, and intravascular imaging modalities including laser speckle rheology, optical coherence elastography, and polarization-sensitive optical coherence tomography to measure the mechanical properties of advanced coronary lesions. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in elucidating the mechanical aspects of coronary atherosclerosis in the future.

  2. Viscoelastic and optical properties of four different PDMS polymers

    NASA Astrophysics Data System (ADS)

    Deguchi, Shinji; Hotta, Junya; Yokoyama, Sho; Matsui, Tsubasa S.

    2015-09-01

    Polydimethylsiloxane (PDMS) is the most commonly used silicone elastomer with a wide range of applications including microfluidics and microcontact printing. Various types of PDMS are currently available, and their bulk material properties have been extensively investigated. However, because the properties are rarely compared in a single study, it is often unclear whether the large disparity of the reported data is attributable to the difference in methodology or to their intrinsic characteristics. Here we report on viscoelastic properties and optical properties of four different PDMS polymers, i.e. Sylgard-184, CY52-276, SIM-360, and KE-1606. Our results show that all the PDMSs are highly elastic rather than viscoelastic at the standard base/curing agent ratios, and their quantified elastic modulus, refractive index, and optical cleanness are similar but distinct in magnitude.

  3. Electrically conductive and optically active porous silicon nanowires.

    PubMed

    Qu, Yongquan; Liao, Lei; Li, Yujing; Zhang, Hua; Huang, Yu; Duan, Xiangfeng

    2009-12-01

    We report the synthesis of vertical silicon nanowire array through a two-step metal-assisted chemical etching of highly doped n-type silicon (100) wafers in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of the as-grown silicon nanowires is tunable from solid nonporous nanowires, nonporous/nanoporous core/shell nanowires, to entirely nanoporous nanowires by controlling the hydrogen peroxide concentration in the etching solution. The porous silicon nanowires retain the single crystalline structure and crystallographic orientation of the starting silicon wafer and are electrically conductive and optically active with visible photoluminescence. The combination of electronic and optical properties in the porous silicon nanowires may provide a platform for novel optoelectronic devices for energy harvesting, conversion, and biosensing.

  4. Optical modelling data for room temperature optical properties of organic–inorganic lead halide perovskites

    PubMed Central

    Jiang, Yajie; Green, Martin A.; Sheng, Rui; Ho-Baillie, Anita

    2015-01-01

    The optical properties of perovskites at ambient temperatures are important both to the design of optimised solar cells as well as in other areas such as the refinement of electronic band structure calculations. Limited previous information on the optical modelling has been published. The experimental fitting parameters for optical constants of CH3NH3PbI3−xClx and CH3NH3PbI3 perovskite films are reported at 297 K as determined by detailed analysis of reflectance and transmittance data. The data in this study is related to the research article “Room temperature optical properties of organic–inorganic lead halide perovskites” in Solar Energy Materials & Solar Cells [1]. PMID:26217745

  5. Nonlinear optical and optical limiting properties of polymeric carboxyl phthalocyanine coordinated with rare earth atom

    NASA Astrophysics Data System (ADS)

    Zhao, Peng; Wang, Zonghua; Chen, Jishi; Zhou, Yu; Zhang, Fushi

    2017-04-01

    The nonlinear optical properties of the polymeric carboxyl phthalocyanine with lanthanum (LaPPc.COOH), holmium (HoPPc.COOH) and ytterbium (YbPPc.COOH) as centric atom, were investigated by the Z-scan method using a picosecond 532 nm laser. The synthesized phthalocyanines had steric polymeric structure and dissolved well in aqueous solution. The nonlinear optical response of them was attributed to the reverse saturable absorption and self-focus refraction. The nonlinear absorption properties decreased with the centric atoms changing from La, Ho to Yb. The largest second-order hyperpolarizability and optical limiting response threshold of LaPPc.COOH were 3.89 × 10-29 esu and 0.32 J/cm2, respectively. The reverse saturable absorption was explained by a three level mode of singlet excited state under the picosecond irradiation. The result indicates the steric structure presented additive stability of these polymeric phthalocyanines for their application as potential optical limiting materials.

  6. Optical techniques for determining dynamic material properties

    SciTech Connect

    Paisley, D.L.; Stahl, D.B.

    1996-12-31

    Miniature plates are laser-launched with a 10-Joule Nd:YAG for one-dimensional (1-D) impacts on to target materials much like gas gun experiments and explosive plane wave plate launch. By making the experiments small, flyer plates (3 mm diameter x 50 micron thick) and targets (10 mm diameter x 200 micron thick), 1-D impact experiments can be performed in a standard laser-optical laboratory with minimum confinement and collateral damage. The laser-launched plates do not require the traditional sabot on gas guns nor the explosives needed for explosive planewave lenses, and as a result are much more amenable to a wide variety of materials and applications. Because of the small size very high pressure gradients can be generated with relative ease. The high pressure gradients result in very high strains and strain rates that are not easily generated by other experimental methods. The small size and short shock duration (1 - 20 ns) are ideal for dynamically measuring bond strengths of micron-thick coatings. Experimental techniques, equipment, and dynamic material results are reported.

  7. Acousto-optical properties of metamaterials

    SciTech Connect

    Pustovoit, V I

    2016-02-28

    The possibility of the effective use of metamaterials in acousto-optics is demonstrated. It is shown that photoelastic constants that determine a change in the dielectric constant of a heterogeneous medium under the action of a sound wave can significantly exceed the corresponding constants for conventional crystals. We have analysed the mechanisms of the dielectric constant variation in a heterogeneous medium consisting of nanoparticles in the form of ellipsoids and have found explicitly the values of the photoelastic constants. It is shown that the mechanism of the dielectric constant variation in a longitudinal sound wave is reduced to a change in the local concentration of nanoparticles in the bulk and in a transverse acoustic wave – to a local rotation of space-oriented nanoellipsoids. It is also shown that the use of metamedia with a nonuniform distribution of nanoparticles provides a unique opportunity for designing qualitatively new instruments and devices that cannot be produced on the basis of conventional crystals. It is noted that metamaterials open ample opportunities for creating devices of the IR region of the spectrum due to the absence of restrictions on the size of such media. (metamaterials)

  8. Crystallization, Optical and Chemical Properties of Fluoride Glasses

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.

    1985-01-01

    Fluoride glasses have great promise as infrared optical components, especially fibers, because they are transparent to 8 micrometers and higher. In order to optimize properties, different glass compositions are needed. Some are hard to form in a container, and may possibly be formable in a containerless furnace. Understanding of crystallization with and without a container could lead to glasses with optimum properties. Chemical durability (attack by water) can limit or extend the applicability of fluoride glasses. Progress to date is given.

  9. Optical properties of hematoporphyrin monomethyl ether (HMME), a PDT photosensitizer.

    PubMed

    Lei, Tim C; Glazner, Gregory F; Duffy, Michael; Scherrer, Larry; Pendyala, Srinivas; Li, Buhong; Wang, Xiuli; Wang, Hongwei; Huang, Zheng

    2012-09-01

    We report on some of the optical properties of Hemoporfin (hematoporphyrin monomethyl ether, HMME), a photodynamic therapy (PDT) photosensitizer that has been in clinical trials in China since the early 1990s. We characterized the photosensitizer on the basis of one- and two-photon absorption and fluorescence emission. The effects of photobleaching were probed to characterize its decay kinetics. Additionally, we determined time resolved fluorescence and thermal effects on fluorescence and absorption properties.

  10. Structural analysis and optical properties of the Bi2–xYxWO6 system

    PubMed Central

    Pasternak, S.; Levy, D.; Paz, Y.

    2016-01-01

    Photocatalytic conversion of solar energy into chemical energy has attracted considerable interest for several decades. One compound already reported as a visible-light-active photocatalyst for water splitting is BiYWO6, a member of the Bi2–xYxWO6 family of compounds. The structural and optical properties of other members of this family have not been reported to date. In this work, we synthesized various compositions of Bi2–xYxWO6, studied their optical properties, and report their structural parameters obtained by utilizing powder diffraction coupled with Rietveld refinement. PMID:28066155

  11. Electronic structures and optical properties of silicon nanowires

    NASA Astrophysics Data System (ADS)

    Li, Jun; Freeman, Arthur

    2006-03-01

    Recent optical spectroscopic and theoretical/computational studies challenge the previous consensus on the nature of the optical properties of Si nanowires (SiNW). Here, we present results of precise theoretical FLAPW determinations of the electronic structures and optical properties of (001) and (111) one nm SiNW. The electronic states at the gaps demonstrate a strong orientation dependent parabolic character in the Brillouin zone and a clear entanglement in real space between 1D and 2D dimensions of the wire. The local symmetry imposed by quantum confinement quenches the transitions around the gap, yielding an optically inactive direct gap. The observed (001) photoluminescence is attributed to a transition rooted in an Si8 ring. The optical structure in the experimental range is well reproduced by our first-principles calculations that include the screened exchange-LDA correction to the well-known failure of the LDA. Our predictions about the anisotropy and orientation dependent optical absorption are easily verified experimentally. Work supported by DARPA B529527//W-7405-Eng-48. Holmes, Johnston, Doty, and Korgel, Science 287, 1471 (2000) Zhao, Wei, Yang, and Chou, Phys. Rev. Lett. 92, 236805 (2004) Wimmer, Krakauer, Weinert, and Freeman, PRB 24, 864 (1981)

  12. 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.

  13. Optical properties and climate forcing of Icelandic dust

    NASA Astrophysics Data System (ADS)

    Dagsson Waldhauserova, Pavla; Olafsson, Haraldur; Arnalds, Olafur; Hladil, Jindrich; Skala, Roman; Navratil, Tomas; Chadimova, Leona; Gritsevich, Maria; Peltoniemi, Jouni; Hakala, Teemu

    2014-05-01

    Iceland is an active source of dust originating from glaciogenic and volcanic sediments. The frequency of days with dust suspension exceeded 34 dust days annually in 1949-2011. This figure represents a minimum value as many dust storms occur without the dust passing the weather stations recording the events. Comparison of meteorological synoptic codes for dust observation and direct particulate matter mass concentration measurements in 2005-2013 showed that the mean number of dust days in Iceland can increase up to135 dust days annually. Dust events in NE Iceland occur mostly in May-September, while almost half of all dust events in SW Iceland were at sub-zero temperatures or in winter. Icelandic dust is different from the crustal dust; it is of volcanic origin and dark in colour. It contains sharp-tipped shards and is often with bubbles. Such physical properties allow large particle suspension and transport to long distances, e.g. towards the Arctic. To estimate the further impacts of dust transport, both laboratory and snow spectropolarimetric measurements were done using the Finnish Geodetic Institute Field Goniospectrometer FIGIFIGO (http://www.polarisation.eu/index.php/list-of-instruments/view-submission/172), an automated portable instrument for multiangular reflectance measurements. The albedo, hemispherical directional reflectance factor (HDRF), polarization, and other snow properties were monitored on the snow and areas affected by the dust deposition through the following melting period in spring 2013 in Lapland during the Soot on Snow (SoS) 2013 campaign. Glaciogenic silt deposited on snow made the snow optically darker. The melting, metamorphose and diffusion processes were fast during the measurement time while the sun heated the particles, snow melted around, and the particles diffused inside the snow. Smaller particles diffused faster than the larger. Fine silt particles tended to form larger grains. Larger volcanic sand particles had lower

  14. Synthesis and optical properties of photochromic perinaphthothioindigo

    NASA Astrophysics Data System (ADS)

    Cherepy, Nerine J.; Sanner, Robert D.

    2006-09-01

    (1,2-naphtho)(1,8-naphtho)thioindigo (PNT) has been synthesized following a simple Friedel-Crafts route and its photochemical properties in toluene and polymethylmethacrylate (PMMA) have been characterized. PNT is a photochromic molecule capable of reversible photoisomerization between a yellow form ( cis-PNT, λmax = 484 nm) and a purple form ( trans-PNT, λmax = 595 nm). The stable purple form converts to the yellow form with a trans-PNT to cis-PNT conversion quantum yield of 0.027 in toluene and 0.062 in PMMA. The unstable yellow form exhibits a cis-PNT to trans-PNT quantum efficiency of conversion of 0.27-0.85 in toluene and 0.17-0.68 PMMA, with highest conversion efficiency occurring in the vicinity of its λmax of 484 nm. trans-PNT has a strong fluorescence quantum yield, 0.14 (toluene) and 0.16 (PMMA). For samples prepared photochemically in the cis-PNT form, slow thermal relaxation to the trans form occurs in the dark, with a half life of about 17 h in toluene (25 °C) and even slower, 168 h, in PMMA. The property of photoswitching between fluorescent and non-fluorescent forms makes this material a candidate for many applications in imaging and data storage.

  15. Optic foramen morphology and activity pattern in birds.

    PubMed

    Hall, Margaret I; Iwaniuk, Andrew N; Gutiérrez-Ibáñez, Cristián

    2009-11-01

    The optic nerve is the sole output of visual information from the ganglion cell layer of the retina to the brain in vertebrates. The size of the optic nerve is predicted to be closely associated with activity pattern, and, in many birds, the size of the optic foramen approximates the size of the optic nerve. Specifically, nocturnal species should have relatively smaller optic foramina than diurnal species because of differences in retinal pooling between activity patterns. If optic foramen morphology varies predictably with activity pattern in birds, this variable may be useful for interpreting activity pattern for birds that do not have soft tissue available for study, specifically for fossils. Across 177 families (from 27 orders), we describe four different optic foramen morphologies, only one of which corresponds well with the size of the optic nerve and is therefore appropriate for activity pattern analyses. Here, we test our hypothesis that nocturnal species will have relatively smaller optic foramina than diurnal species, across all species that we measured that have a discrete optic foramen. Regression analyses using species as independent data points and using comparative methods yielded significant differences in optic foramen size between nocturnal and diurnal species relative to three variables: head length, orbit depth, and sclerotic ring inner diameter. Nocturnal species consistently exhibit significantly smaller relative optic foramen diameters than diurnal species. Our results indicate that optic foramen diameter, in combination with either the sclerotic ring or the orbit diameter, can be used to predict activity pattern.

  16. Active polarimeter optical system laser hazard analysis.

    SciTech Connect

    Augustoni, Arnold L.

    2005-07-01

    A laser hazard analysis was performed for the SNL Active Polarimeter Optical System based on the ANSI Standard Z136.1-2000, American National Standard for Safe Use of Lasers and the ANSI Standard Z136.6-2000, American National Standard for Safe Use of Lasers Outdoors. The Active Polarimeter Optical System (APOS) uses a pulsed, near-infrared, chromium doped lithium strontium aluminum fluoride (Cr:LiSAF) crystal laser in conjunction with a holographic diffuser and lens to illuminate a scene of interest. The APOS is intended for outdoor operations. The system is mounted on a height adjustable platform (6 feet to 40 feet) and sits atop a tripod that points the beam downward. The beam can be pointed from nadir to as much as 60 degrees off of nadir producing an illuminating spot geometry that can vary from circular (at nadir) to elliptical in shape (off of nadir). The JP Innovations crystal Cr:LiSAF laser parameters are presented in section II. The illuminating laser spot size is variable and can be adjusted by adjusting the separation distance between the lens and the holographic diffuser. The system is adjusted while platform is at the lowest level. The laser spot is adjusted for a particular spot size at a particular distance (elevation) from the laser by adjusting the separation distance (d{sub diffuser}) to predetermined values. The downward pointing angle is also adjusted before the platform is raised to the selected operation elevation.

  17. Optical phantoms with variable properties and geometries for diffuse and fluorescence optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Leh, Barbara; Siebert, Rainer; Hamzeh, Hussein; Menard, Laurent; Duval, Marie-Alix; Charon, Yves; Abi Haidar, Darine

    2012-10-01

    Growing interest in optical instruments for biomedical applications has increased the use of optically calibrated phantoms. Often associated with tissue modeling, phantoms allow the characterization of optical devices for clinical purposes. Fluorescent gel phantoms have been developed, mimicking optical properties of healthy and tumorous brain tissues. Specific geometries of dedicated molds offer multiple-layer phantoms with variable thicknesses and monolayer phantoms with cylindrical inclusions at various depths and diameters. Organic chromophores are added to allow fluorescence spectroscopy. These phantoms are designed to be used with 405 nm as the excitation wavelength. This wavelength is then adapted to excite large endogenous molecules. The benefits of these phantoms in understanding fluorescence tissue analysis are then demonstrated. In particular, detectability aspects as a function of geometrical and optical parameters are presented and discussed.

  18. Optical Limiting Properties of Graphene/Polymer Composites.

    PubMed

    Pan, Ruiyi; Guo, Jin; Wang, Tingfeng; Shao, Junfeng; Wang, Dong; Zhang, Qiuping; Wang, Yan; Tang, Jun

    2016-04-01

    Graphene oxide (GO) was doped into four polymers films: Poly(methyl methacrylate) (PMMA), polystyrene (PS), polycarbonate (PC), and polyacrylonitrile (PAN). Following that, their optical limiting properties were investigated at 532 nm. In order to make GO hydrophobic, the lipophilic alkyl chains were connected to GO. The results showed that GO/PAN composite possesses better non-linear response than the other three composites at the same transmission (T ~ 59%). The reason were attributed to the thermal effect coming from high input fluence of laser, which improved the cross link density of PAN and further enhanced the interaction between the GO-ODA and PAN. Meanwhile, GO/PC and GO/PS had similar optical limiting property and GO/PMMA film gave the weakest optical limiting effect in our experiment.

  19. Optical Properties of Astronomical Silicates in the Far-infrared

    NASA Technical Reports Server (NTRS)

    Rinehart, Stephen A,; Benford, Dominic J.; Dwek, Eli; Henry, Ross M.; Nuth, Joseph A., III; Silverberg, Robert f.; Wollack, Edward J.

    2008-01-01

    Correct interpretation of a vast array of astronomical data relies heavily on understanding the properties of silicate dust as a function of wavelength, temperature, and crystallinity. We introduce the QPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project to address the need for high fidelity optical characterization data on the various forms of astronomical dust. We use two spectrometers to provide extinction data for silicate samples across a wide wavelength range (from the near infrared to the millimeter). New experiments are in development that will provide complementary information on the emissivity of our samples, allowing us to complete the optical characterization of these dust materials. In this paper, we present initial results from several materials including amorphous iron silicate, magnesium silicate and silica smokes, over a wide range of temperatures, and discuss the design and operation of our new experiments.

  20. Multiple intersection properties of optical resonance modes in metallic metamaterials

    NASA Astrophysics Data System (ADS)

    Tokuda, Yasunori; Sakaguchi, Koichiro; Yamaguchi, Yuki; Takano, Keisuke

    2017-03-01

    Unusual behavior of Fabry-Perot-like waveguide resonance modes is presented for a quasi-dielectric metamaterial that consists of two metallic sub-wavelength cut-through slit-array slabs separated by an air-gap region. Simulations based on the finite-difference time-domain method were conducted. The unique optical properties were interpreted in terms of multiple intersection of the resonance modes. Depending on the intersection conditions of the optical modes, furthermore, a variety of crossing characteristics, i.e., fade-out crossing with/without an isolated loop, anticrossing with/without intensity reduction, and anticrossing with/without frequency repulsion, were identified for the air-gap dependence of the transmission spectra. These findings, which were obtained by careful observation of the properties of this type of metamaterial, present a novel and interesting aspect of the behavior of the optical resonance modes.

  1. Electronic structure and optical properties of monoclinic clinobisvanite BiVO4.

    PubMed

    Zhao, Zongyan; Li, Zhaosheng; Zou, Zhigang

    2011-03-14

    Monoclinic clinobisvanite bismuth vanadate is an important material with wide applications. However, its electronic structure and optical properties are still not thoroughly understood. Density functional theory calculations were adopted in the present work, to comprehend the band structure, density of states, and projected wave function of BiVO(4). In particular, we put more emphasis upon the intrinsic relationship between its structure and properties. Based on the calculated results, its molecular-orbital bonding structure was proposed. And a significant phenomenon of optical anisotropy was observed in the visible-light region. Furthermore, it was found that its slightly distorted crystal structure enhances the lone-pair impact of Bi 6s states, leading to the special optical properties and excellent photocatalytic activities.

  2. Demonstrations of Some Optical Properties of Liquid Crystals.

    ERIC Educational Resources Information Center

    Nicastro, Anthony J.

    1983-01-01

    Discusses several properties of liquid crystal displays. Includes instructions for demonstrating liquid crystalline phase, ordering of the long axes of molecules along one direction, and electro-optic effects. The latter is accomplished with the use of an overhead projector following preparation of a sandwich cell. (JN)

  3. Comparing optical properties of different species of diatoms

    NASA Astrophysics Data System (ADS)

    Maibohm, C.; Friis, S. M. M.; Su, Y.; Rottwitt, K.

    2015-03-01

    Diatoms are single cellular algae encapsulated in an external wall of micro-structured porous silica called the frustule. Diatoms are present in all water environments and contribute with 20-25 % of the global primary production of oxygen by photosynthesis. The appearance of the frustule is very species dependent with huge variety in size, shape, and microstructure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with common traits, effects and differences between the different frustules. We have observed, when incident light interacts with the micro-structured frustule it is multiple diffracted giving rise to wavelength dependent multiple focal points and other optical effects. Experimental results have been simulated and well confirmed by free space FFT propagation routine analysis software. The software uses parameters which are extracted from experimental images as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule parameters, maybe by altering growth conditions of the diatoms tailor their optical properties.

  4. AlN Bandgap Temperature Dependence from its Optical Properties

    DTIC Science & Technology

    2008-06-07

    In the present work we report on the AlN gap energy temperature dependence studied through the optical properties of high-quality large bulk AlN...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.

  5. Optical properties of bio-inspired peptide nanotubes

    NASA Astrophysics Data System (ADS)

    Handelman, Amir; Apter, Boris; Rosenman, Gil

    2016-04-01

    Supramolecular self-assembled bio-inspired peptide nanostructures are favorable to be implemented in diverse nanophotonics applications due to their superior physical properties such as wideband optical transparency, high second-order nonlinear response, waveguiding properties and more. Here, we focus on the optical properties found in di-phenylalanine peptide nano-architectures, with special emphasize on their linear and nonlinear optical waveguiding effects. Using both simulation and experiments, we show their ability to passively guide light at both fundamental and second-harmonic frequencies. In addition, we show that at elevated temperatures, 140-180°C, these native supramolecular structures undergo irreversible thermally induced transformation via re-assembling into completely new thermodynamically stable phase having nanofiber morphology similar to those of amyloid fibrils. In this new phase, the peptide nanofibers lose their second-order nonlinear response, while exhibit profound modification of optoelectronic properties followed by the appearance of visible (blue and green) photoluminescence (PL). Our study propose a new generation of multifunctional optical waveguides with variety of characteristics, which self-assembled into 1D-elongated nanostructures and could be used as building blocks of many integrated photonic devices.

  6. Calculated optical properties of thorium, protactinium, and uranium metals

    SciTech Connect

    Gasche, T.; Brooks, M.S.; Johansson, B.

    1996-07-01

    We report self-consistent energy band calculations using the linear muffin-tin orbital method and the local-spin-density approximation to exchange and correlation in density-functional theory for the light actinide metals Th, Pa, and U. The optical properties have been calculated and compared with measurements, where possible. The dependence of the optical response functions upon crystal structure was found to be surprisingly large and the dependence upon spin-orbit coupling, less so. Where it was possible to make comparison, agreement with experiment was obtained for the maxima of the optical spectra, the exception being a feature in the optical conductivity at 10 eV measured in both Th and U but not obtained in the calculations. {copyright} {ital 1996 The American Physical Society.}

  7. Optical properties of infrared FELs from the FELI Facility II

    SciTech Connect

    Saeki, K.; Okuma, S.; Oshita, E.

    1995-12-31

    The FELI Facility II has succeeded in infrared FEL oscillation at 1.91 {mu} m using a 68-MeV, 40-A electron beam from the FELI S-band linac in February 27, 1995. The FELI Facility II is composed of a 3-m vertical type undulator ({lambda}u=3.8cm, N=78, Km a x=1.4, gap length {ge}20mm) and a 6.72-m optical cavity. It can cover the wavelength range of 1-5{mu}m. The FELs can be delivered from the optical cavity to the diagnostics room through a 40-m evacuated optical pipeline. Wavelength and cavity length dependences of optical properties such as peak power, average power, spectrum width, FEL macropulse, FEL transverse profile are reported.

  8. Experimental analysis of optical limiting properties of Cu nanoclusters

    NASA Astrophysics Data System (ADS)

    Wang, Y. H.; Wang, Y. M.; Han, C. J.; Lu, J. D.; Ji, L. L.

    2010-06-01

    Optical nonlinearities of Cu nanoclusters prepared by implanting Cu ions into silica at 180 keV with dose of 1×10 17 ions/cm 2 have been studied. The third-order nonlinear optical properties of the nanoclusters were measured at 1064 nm excitations using Z-scan technique. Results of the investigation of nonlinear refraction by the off-axis Z-scan configuration were presented and the mechanisms responsible for the nonlinear response were discussed. Innovative point of this paper is that we carried out curve fitting analysis, which is based on MATLAB features, for Cu optical limiting experiment. Our results showed that Cu nanoclusters have refractive optical limiting effect at 1064 nm.

  9. WIYN active optics: a platform for AO

    NASA Astrophysics Data System (ADS)

    Code, Arthur D.; Claver, Charles F.; Goble, Larry W.; Jacoby, George H.; Sawyer, David G.

    1998-09-01

    The WIYN 3.5 meter telescope is situated on the southwest ridge of Kitt Peak yielding excellent atmosphere seeing conditions. As such, the telescope and enclosure design was directed towards exploiting this feature. The primary mirror was spun cast and figured by the Steward Observatory Mirror Laboratory and the secondary mirror by Contraves. In both cases the performance exceeded the design specifications. The borosilicate primary is actively temperature controlled to within 0.2 C of the desired temperature, typically 0.5 degrees C below the ambient air. The telescope structure is also temperature controlled and the enclosure is opened to the outside ion all sides, which all heat sources are vented to ducts carrying air downwind of the facility. The primary mirror is actively controlled for low order aberrations by 66 axial actuators which are adjusted open loop via force matrix look-up tables and closed loop via real-time wavefront curvature sensing measurements. The active optics also included real-time collimation and focus control. The telescope drive and guider are capable of providing tracking to a few hundredths of a second of arc. By employing active telescope control at this level, it is possible to maintain telescope and local wavefront distortion to a level where atmospheric effects dominate the image quality. Since a significant fraction of the power in the atmospheric disturbances is contained in image motion the first step in adaptive optics control will be simple tip tilt. Studies of higher order AO system are being carried out, as well as additional test characterizing the telescope and site. It is intended to continue such studies in an attempt to establish long term variances.

  10. Synthesis and Optical Properties of Photochromic Perinaphthothioindigo

    SciTech Connect

    Cherepy, N J; Sanner, R D

    2005-02-10

    (1,2-naphtho)(1,8-naphtho)thioindigo (PNT) has been synthesized following a simple Friedel-Crafts route and its photochemical properties in toluene and PMMA characterized. PNT is a photochromic molecule capable of reversible photoisomerization between a yellow form (cis-PNT, {lambda}{sub max} = 484 nm) and a purple form (trans-PNT, {lambda}{sub max} = 595 nm). The stable purple form converts to the yellow form with a trans-PNT to cis-PNT conversion quantum yield of 0.027 in toluene and 0.062 in PMMA. The unstable yellow form exhibits a cis-PNT to trans-PNT quantum efficiency of conversion of 0.27-0.85 in toluene and 0.17-0.68 PMMA, with highest conversion efficiency occurring in the vicinity of its {lambda}{sub max} of 484 nm. Trans-PNT has a strong fluorescence quantum yield, 0.14 (toluene) and 0.16 (PMMA). For samples prepared photochemically in the cis-PNT form, slow thermal relaxation to the trans form occurs in the dark, with a half life of about 17 hours in toluene (25 C) and even slower, 168 hours, in PMMA. The property of photoswitching between fluorescent and non-fluorescent forms makes this material a candidate for many applications in imaging and data storage. An anomalous excitation profile for the fluorescence from trans-PNT, showing a dip at {approx}600 nm, is an agreement with the wavelength-dependent quantum yield of conversion from trans-PNT to cis-PNT, which is highest at the absorbance peak.

  11. Human psychophysiological activity monitoring methods using fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Zyczkowski, M.; Uzieblo-Zyczkowska, B.

    2010-10-01

    The paper presents the concept of fiber optic sensor system for human psycho-physical activity detection. A fiber optic sensor that utilizes optical phase interferometry or intensity in modalmetric to monitor a patient's vital signs such as respiration cardiac activity, blood pressure and body's physical movements. The sensor, which is non-invasive, comprises an optical fiber interferometer that includes an optical fiber proximately situated to the patient so that time varying acusto-mechanical signals from the patient are coupled into the optical fiber. The system can be implemented in embodiments ranging form a low cost in-home to a high end product for in hospital use.

  12. Estimation of aerosol optical properties from all-sky imagers

    NASA Astrophysics Data System (ADS)

    Kazantzidis, Andreas; Tzoumanikas, Panagiotis; Salamalikis, Vasilios; Wilbert, Stefan; Prahl, Christoph

    2015-04-01

    Aerosols are one of the most important constituents in the atmosphere that affect the incoming solar radiation, either directly through absorbing and scattering processes or indirectly by changing the optical properties and lifetime of clouds. Under clear skies, aerosols become the dominant factor that affect the intensity of solar irradiance reaching the ground. It has been shown that the variability in direct normal irradiance (DNI) due to aerosols is more important than the one induced in global horizontal irradiance (GHI), while the uncertainty in its calculation is dominated by uncertainties in the aerosol optical properties. In recent years, all-sky imagers are used for the detection of cloud coverage, type and velocity in a bouquet of applications including solar irradiance resource and forecasting. However, information about the optical properties of aerosols could be derived with the same instrumentation. In this study, the aerosol optical properties are estimated with the synergetic use of all-sky images, complementary data from the Aerosol Robotic Network (AERONET) and calculations from a radiative transfer model. The area of interest is Plataforma Solar de Almería (PSA), Tabernas, Spain and data from a 5 month period are analyzed. The proposed methodology includes look-up-tables (LUTs) of diffuse sky radiance of Red (R), Green (G) and Blue (B) channels at several zenith and azimuth angles and for different atmospheric conditions (Angström α and β, single scattering albedo, precipitable water, solar zenith angle). Based on the LUTS, results from the CIMEL photometer at PSA were used to estimate the RGB radiances for the actual conditions at this site. The methodology is accompanied by a detailed evaluation of its robustness, the development and evaluation of the inversion algorithm (derive aerosol optical properties from RGB image values) and a sensitivity analysis about how the pre-mentioned atmospheric parameters affect the results.

  13. Exploring graphene superlattices: Magneto-optical properties

    NASA Astrophysics Data System (ADS)

    Duque, C. A.; Hernández-Bertrán, M. A.; Morales, A. L.; de Dios-Leyva, M.

    2017-02-01

    We present a detailed study of magnetic subbands, wave functions, and transition strengths for graphene superlattices (SLs) subject to a perpendicular magnetic field. It is shown that, for a weak magnetic field, the flat subbands of a SL exhibiting extra Dirac points are grouped into subsets, each of which consists of a singlet subband and a nearly degenerate doublet subband, and one nearly degenerate triplet subband. It was found that the wave functions corresponding to a singlet or to a doublet are always located around the image in real space of the central or extra Dirac points in k-space. The latter properties were explained by assuming that the electron motion is quasi-classical. Our study revealed that, for an intermediate field, the general characteristics of the wave functions are very similar to those of the pristine graphene, while for weak field, their behavior is drastically different. The latter is characterized by rapid oscillations which were understood using the solutions provided by the formalism of Luttinger-Kohn. The study on transition strengths allows us to obtain, for SLs with extra Dirac points in a weak magnetic field and different polarizations, the conditions under which transitions between multiplets are approximately allowed. It was shown that these conditions correspond to an unusual selection rule that is broken when the magnetic field intensity increases from weak to an intermediate value.

  14. Optical fiber technique for in-reactor mechanical properties measurement

    SciTech Connect

    Schley, R. S.; Hurley, D. H.; Hua, Z. A.

    2013-01-25

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the resonant frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  15. Optical Fiber Technique for In-Reactor Mechanical Properties Measurement

    SciTech Connect

    Robert S. Schley; Zilong Hua; David H. Hurley; Heng Ban

    2012-07-01

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the natural frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  16. Optical fiber technique for in-reactor mechanical properties measurement

    NASA Astrophysics Data System (ADS)

    Schley, R. S.; Hurley, D. H.; Hua, Z. A.

    2013-01-01

    In-reactor measurement of material properties is required for a better understanding of radiation effects on materials. We present an optical fiber based technique for measuring changes in elastic properties which involves exciting and measuring flexural vibrations in a thin cantilever beam. By exciting the beam and measuring the resonant frequency, changes in the modulus of elasticity can be monitored. The technique is demonstrated by monitoring the elastic property changes of a beam fabricated from copper, as the copper undergoes recrystallization at elevated temperature.

  17. Review on optical and electrical properties of oxide semiconductors

    NASA Astrophysics Data System (ADS)

    Kim, Dong Lim; Kim, Hyun Jae

    2010-03-01

    Oxide semiconductors became one of the potential elements for large area electronics such as a channel for thin film transistors. Optical and electrical properties were modified by alloying or doping of several oxide materials; In2O3, ZnO, Ga2O3, and SnO2. The excellent properties achieved at the ternary or quaternary alloys could be explained by the role of each materials as a carrier controller, a conduction path, and etc. The metal oxide semiconductors were generally deposited by vacuum process but recently, alternative ways, like a sol-gel or an ink-jet printing, are suggested. In this review, diverse approaches on oxide semiconductors are shown, and an in-depth discussion of the optical and electrical properties alternation in metal oxide alloy fabricated by various methods is given.

  18. Optical properties of fly ash. Volume 2, Final report

    SciTech Connect

    Self, S.A.

    1994-12-01

    Research performed under this contract was divided into four tasks under the following headings: Task 1, Characterization of fly ash; Task 2, Measurements of the optical constants of slags; Task 3, Calculations of the radiant properties of fly ash dispersions; and Task 4, Measurements of the radiant properties of fly ash dispersions. Tasks 1 and 4 constituted the Ph.D. research topic of Sarbajit Ghosal, while Tasks 2 and 3 constituted the Ph.D. research topic of Jon Ebert. Together their doctoral dissertations give a complete account of the work performed. This final report, issued in two volumes consists of an executive summary of the whole program followed by the dissertation of Ghosal and Ebert. Volume 2 contains the dissertation of Ebert which covers the measurements of the optical constants of slags, and calculations of the radiant properties of fly ash dispersions. A list of publications and conference presentations resulting from the work is also included.

  19. 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.

  20. The electronic and optical properties of Eu/Si-codoped anatase TiO2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Lin, Yanming; Jiang, Zhenyi; Hu, Xiaoyun; Zhang, Xiaodong; Fan, Jun

    2012-03-01

    The electronic and optical properties of Eu/Si-codoped anatase TiO2 are investigated using the density functional theory. The calculated results show that the synergistic effects of Eu/Si codoping can effectively extend the optical absorption edge, which can lead to higher visible-light photocatalytic activities than pure anatase TiO2. To verify the reliability of our calculated results, nanocrystalline Eu/Si-codoped TiO2 is prepared by a sol-gel-solvothermal method, and the experimental results also indicate that the codoping sample exhibits better absorption performance and higher photocatalytic activities than pure TiO2.

  1. Optical properties and emissivities of liquid metals and alloys

    NASA Technical Reports Server (NTRS)

    Krishnan, Shankar; Nordine, Paul C.

    1993-01-01

    This paper presents the results from our on-going program to investigate the optical properties of liquid metals and alloys at elevated temperatures. Ellipsometric and polarimetric techniques have been used to investigate the optical properties of materials in the 1000 - 3000 K temperature range and in the 0.3 - 0.1 mu m wavelength range. The ellipsometric and polarimetric techniques are described and the characteristics of the instruments are presented. The measurements are conducted by reflecting a polarized laser beam from an electromagnetically levitated liquid metal or alloy specimen. A Rotating Analyzer Ellipsometer (RAE) or a four-detector Division-of-Amplitude Photopolarimeter (DOAP) is used to determine the polarimetric properties of the light reflected at an angle of incidence of approximately 68 deg. Optical properties of the specimen which are calculated from these measurements include the index of refraction, extinction coefficient, normal spectral emissivity, and spectral hemispherical emissivity. These properties have been determined at various wavelengths and temperatures for liquid Ag, Al, Au, Cu, Nb, Ni, Pd, Pt, Si, Ti, Ti-Al alloys, U, and Zr. We also describe new experiments using pulsed-dye laser spectroscopic ellipsometry for studies of the wavelength dependence of the emissivities and optical properties of materials at high temperature. Preliminary results are given for liquid Al. The application of four-detector polarimetry for rapid determination of surface emissivity and true temperature is also described. Characteristics of these devices are presented. An example of the accuracy of this instrument in measurements of the melting point of zirconium is illustrated.

  2. Spectral ellipsometry studying of iron's optical and electronic properties

    NASA Astrophysics Data System (ADS)

    Chernukha, Yevheniia; Stashchuk, Vasyl S.; Polianska, Olena; Oshtuk, Olexsandr

    2014-05-01

    Fe's optical and electronic properties were investigated at room temperature in different structural states. The sample's surface was explored in wide spectral range λ = 0,23-17,0 μm (E = 4,96 - 0,07 еV ) by the Beatty's spectral ellipsometry method. While an experiment was carried out ellipsometry parameters Δ and ψ were measure near the principal angle of incidence. The refraction index R , permittivity Ɛ and optical conductivity σ( hν ) , that is proportional to the interband density of electronic states, were calculated using these parameters. Fe's optical conductivities in liquid, amorphous and crystalline states were compared in this work. The optical conductivity was calculated using the published data of the iron's density of electronic states in crystalline, amorphous and liquid states for the comparison of the experimental and theoretical results. It is shown that, at structural transformations "amorphous, liquid state- crystalline state", the optical properties of metallic iron are determined, in the first turn, by the nearest neighborhood, and the electronic structure is not subjected to significant modifications.

  3. Active optics with a minimum number of actuators

    NASA Astrophysics Data System (ADS)

    Lemaitre, Gerard R.

    2014-06-01

    Optics for astronomy implies powerful developments of active and adaptive optics methods applied to instrumentation from X-rays to the near infrared for the design of telescopes, spectrographs, and coronagraph planet finders. This presentation particularly emphasizes the development of active optics methods. Highly accurate and remarkably smooth surfaces from active optics methods allow new optical systems that use highly aspheric and non-axisymmetric - freeform - surfaces. Depending on the goal and performance required for a deformable optical surface, elasticity theory analysis is carried out either with small deformation thin plate theory, large deformation thin plate theory, shallow spherical shell theory, or the weakly conical shell theory. A mirror thickness distribution is then determined as a function of associated bending actuators and boundary conditions. For a given optical shape to generate, one searches for optical solutions with a minimum number of actuators.

  4. System Report for the Optical Properties Monitor (OPM) Experiment

    NASA Technical Reports Server (NTRS)

    Hummer, L.

    2001-01-01

    This systems report describes how the Optical Properties Monitor (OPM) experiment was developed. Pertinent design parameters are discussed, along with mission information and system requirements to successfully complete the mission. Environmental testing was performed on the OPM to certify it for spaceflight. This testing included vibration, thermal vacuum, electromagnetic interference and conductance, and toxicity tests. Instrument and monitor subsystem performances, including the reflectometer, vacuum ultraviolet, total integrated scatter, atomic oxygen monitor, irradiance monitor, and molecular contamination monitor during the mission are discussed. The OPM experiment was launched aboard the Space Shuttle on mission STS-81 in January 1997 and transferred to the Mir space station. An extravehicular activity (EVA) was performed in April 1997 to attach the OPM experiment to the outside of the Mir/Shuttle Docking Module for space environment exposure. The OPM conducted in situ measurements of a number of material samples. These data may be found in the OPM Science Report. OPM was retrieved during an EVA in January 1998 and was returned to Earth on board the Space Shuttle on mission STS-89.

  5. Optical properties of femtosecond laser-treated diamond

    NASA Astrophysics Data System (ADS)

    Calvani, P.; Bellucci, A.; Girolami, M.; Orlando, S.; Valentini, V.; Lettino, A.; Trucchi, D. M.

    2014-10-01

    A laser-induced periodic surface structure (LIPSS) has been fabricated on polycrystalline diamond by an ultrashort Ti:Sapphire pulsed laser source ( λ = 800 nm, P = 3 mJ, 100 fs) in a high vacuum chamber (<10-7 mbar) in order to increase diamond absorption in the visible and infrared wavelength ranges. A horizontally polarized laser beam had been focussed perpendicularly to the diamond surface and diamond target had been moved by an automated X- Y translational stage along the two directions orthogonal to the optical axis. Scanning electron microscopy of samples reveals an LIPSS with a ripple period of about 170 nm, shorter than the laser wavelength. Raman spectra of processed sample do not point out any evident sp 2 content, and diamond peak presents a right shift, indicating a compressive stress. The investigation of optical properties of fs-laser surface textured diamond is reported. Spectral photometry in the range 200/2,000 nm wavelength shows a significant increase of visible and infrared absorption (more than 80 %) compared to untreated specimens (less than 40 %). The analysis of optical characterization data highlights a close relationship between fabricated LIPSS and absorption properties, confirming the optical effectiveness of such a treatment as a light-trapping structure for diamond: these properties, reported for the first time, open the path for new applications of CVD diamond.

  6. Electronic and optical properties of pristine and oxidized borophene

    NASA Astrophysics Data System (ADS)

    Lherbier, Aurélien; Botello-Méndez, Andrés Rafael; Charlier, Jean-Christophe

    2016-12-01

    Borophene, a two-dimensional monolayer of boron atoms, was recently synthesized experimentally and was shown to exhibit polymorphism. In its closed-packed triangular form, borophene is expected to exhibit anisotropic metallic character with relatively high electron velocities. At the same time, very low optical conductivities in the infrared-visible light region were predicted. Based on its promising electronic transport properties and its high transparency, borophene could become a genuine lego piece in the 2D materials assembling game known as the van der Waals heterocrystal approach. However, borophene is naturally degraded in ambient conditions and it is therefore important to assess the mechanisms and the effects of oxidation on borophene monolayers. Optical and electronic properties of pristine and oxidized borophene are here investigated by first-principles approaches. The transparent and conductive properties of borophene are elucidated by analyzing the electronic structure and its interplay with light. Optical response of borophene is found to be strongly affected by oxidation, suggesting that optical measurements can serve as an efficient probe for borophene surface contamination.

  7. 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.

  8. 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.

  9. Temperature-dependent optical properties of Cd(1-x),Zn(x),Te substitute material

    NASA Technical Reports Server (NTRS)

    Quijada, Manuel A.; Russell, Anne Marie; Hill, Robert J.

    2005-01-01

    In this study, we report cryogenic optical properties of Cd(l-x), Zn(x), Te wafers that are used as substrate seed layers in the manufacturing of HgCdTe focal-plane array detectors. These studies are motivated by the fact that the substrate optical properties influence the overall detector performance. The studies consist of measuring the substrate frequency dependent transmittance T(W) and reflectance R(W) above and below the optical band-gap in the UV/Visible and infrared frequency ranges, and with temperature variation of the sample from 5 to 300 K. Determination of the optical absorption from these measurements show that the optical absorption energy gap near 1.6 eV shows a substantial increase as the temperature is reduced from 300 to 5 K. Furthermore, we observe the presence of infrared-active optical phonons whose peak frequency shifts as the temperature of the sample is varied over the measured temperature range. The theoretical frequency dependent optical conductivity, with allowance for redistribution of spectral weight among the interband transition charge carriers, will be discussed.

  10. Optical and electrical properties of bi-layers organic devices

    NASA Astrophysics Data System (ADS)

    Trad, Hager; Rouis, Ahlem; Davenas, Jöel; Majdoub, Mustapha

    2014-10-01

    The influence of interfacial charges on the device characteristics of bi-layers structure LEDs with poly[5-methoxy-2-octyloxy-1,4-phenylenevinylene] (MO-PPV) as active polymer layer is investigated. The concept to improve device performance is presented using: a diacetate cellulose (DAC) and a new synthetized 5-{2-(2-chloroethoxy)ethoxy}-2-{(E)-(2-pyridyl)azo}phenol (PDEG) components. The DAC and mixed (DAC+PDEG) layers were inserted between indium tin oxide (ITO) and MO-PPV polymer. The optical properties (UV-Vis) of MO-PPV, PDEG and mixed (DAC+PDEG) in solutions were studied and compared to those on thin films. Detailed current-voltage measurements of the bi-layers devices showed improvements of the threshold voltage (Vth) of the ITO/(DAC+PDEG)/MO-PPV/Al device attributed to the enhancement of carriers injection and transport resulted from the modified electrode structures. Conduction mechanisms of structure LEDs were matched with space-charge-limited current (SCLC) one. The impedance spectra for all devices can be discussed in terms of an equivalent circuit model designed as a parallel resistor Rp and capacitor Cp network in series with resistor Rs. The ITO/(DAC+PDEG)/MO-PPV/Al device showed the lowest impedance attributed to the removal of contaminants and to changes in the work function of ITO. The frequency-dependent electrical properties of the ITO/(DAC+PDEG)/MO-PPV/Al structure is analyzed by impedance spectroscopy as function of bias. We have extracted numerical values of the equivalent circuit model parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution.

  11. Vibrational Raman optical activity of ketose monosaccharides

    NASA Astrophysics Data System (ADS)

    Bell, Alasdair F.; Hecht, Lutz; Barron, Laurence D.

    1995-07-01

    The vibrational Raman optical activity (ROA) spectra of the four ketose sugars D-fructose, L-sorbose, D-tagatose and D-psicose in aqueous solution, which have been measured in backscattering in the range ≈250-1500 cm -1, are reported. These results are combined with those from a previous ROA study of aldose and pentose sugars in an attempt to establish new vibrational assignments and to verify old ones. The high information content of these spectra provides a new perspective on all the central features of monosaccharide stereochemistry including dominant anomeric configuration, ring conformation, exocyclic CH 2OH group conformation and relative disposition of the hydroxyl groups around the ring.

  12. Electronic and optical properties of CuInTe2

    NASA Astrophysics Data System (ADS)

    Shankar, A.; Thapa, R. K.; Mandal, P. K.

    2016-10-01

    The electronic and optical properties of a ternary chalcopyrite compound CuInTe2 with diamond like structure have been studied. The calculations are carried out using the density functional theory (DFT) based full potential-linearized augmented plane wave (FP- LAPW) method within the framework of GGA and modified Becke Johnson (mBJ) potential approach. The presence of direct energy band gap of 0.8 eV suggests the sample material can be a good material for solar cell application. The study of the optical response of the material against the incident photon energy radiation indicates the material can be an effective candidate for the optoelectronic devices.

  13. Electronic structure and optical properties of solid C 60

    NASA Astrophysics Data System (ADS)

    Mattesini, M.; Ahuja, R.; Sa, L.; Hugosson, H. W.; Johansson, B.; Eriksson, O.

    2009-06-01

    The electronic structure and the optical properties of face-centered-cubic C 60 have been investigated by using an all-electron full-potential method. Our ab initio results show that the imaginary dielectric function for high-energy values looks very similar to that of graphite, revealing close electronic structure similarities between the two systems. We have also identified the origin of different peaks in the dielectric function of fullerene by means of the calculated electronic density of states. The computed optical spectrum compares fairly well with the available experimental data for the Vis-UV absorption spectrum of solid C 60.

  14. Atmospheric Optical Properties and Spectral Analysis of Desert Aerosols

    NASA Astrophysics Data System (ADS)

    Yvgeni, D.; Karnieli, A.; Kaufman, Y. J.; Andreae, M. O.; Holben, B. N.; Maenhaut, W.

    2002-05-01

    Scientific background Aerosols can interact directly with solar and terrestrial radiation by scattering as well as absorption. In addition, they can indirectly alter the planetary albedo by modifying the properties of clouds. Objectives Investigations have been devoted to two main areas: (1) Aerosol climatology situation in the Negev desert, investigations of physical and chemical characteristics of aerosols, and study of the local and long-range transport trajectory of polluted air masses over the Negev desert; and (2) An estimation of the optical properties throughout the atmospheric column by surface measurements via performance of spectral and statistical analysis of the data received from two measurement systems. Results and conclusions Analyzed data from the Sede Boker site, in the Negev Desert of Israel, shows an increase in aerosol optical depth during the summer seasons and a decrease during winter. One of the possible reasons for this characteristic is an increase of the precipitable water (reaches 3.0-3.5 cm) due to a constant wind stream from the Mediterranean Sea in same time. The highest probability distribution of the aerosol optical depth is in the range of 0.15-0.20; and of the Angstrom parameter is in range of 0.83 - 1.07. During dust storm events, the scattering coefficient range at 670 nm and 440 nm wavelengths were inverted. It was discovered that the dust particles in this case had non-spherical character. Comparison between optical depth, measured through all atmospheric column, and scattering coefficient from surface measurements provides correlation coefficient (r) equal to 0.64. The Angstrom parameter, calculated via optical depth and via scattering coefficient, provides a correlation coefficient of 0.66. Thus we can obtain an estimate of the influence of the surface aerosol situation on column optical properties. The combined analysis of dust cloud altitude and optical depth as a function of the time indicates long-term transport and

  15. Theory of the Electronic and Optical Properties of Semiconductor Heterostructures

    DTIC Science & Technology

    1990-01-01

    March, 1990. 2. Theor of Optically-Induced Screening of Piezoelectric Fields in Strained H I I Quntum Wells D. A. Broido, B. V. Shanabrook and D. Gammon, Fall, 1990 Meeting of the Materials Research Society, Boston. 10 ...AD-A231 438 Final Technical Report for ONR Contract #V00014-89-J. 1786 entitled Theory of the Electronic and Optical Properties of Semiconductor... fields in each layer as a consequence of the piezoelectric effect.1 2 It is well known that the strain shifts the conduction and valence band energies

  16. 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).

  17. Method for quantifying optical properties of the human lens

    DOEpatents

    Loree, T.R.; Bigio, I.J.; Zuclich, J.A.; Shimada, Tsutomu; Strobl, K.

    1999-04-13

    A method is disclosed for quantifying optical properties of the human lens. The present invention includes the application of fiberoptic, OMA-based instrumentation as an in vivo diagnostic tool for the human ocular lens. Rapid, noninvasive and comprehensive assessment of the optical characteristics of a lens using very modest levels of exciting light are described. Typically, the backscatter and fluorescence spectra (from about 300- to 900-nm) elicited by each of several exciting wavelengths (from about 300- to 600-nm) are collected within a few seconds. The resulting optical signature of individual lenses is then used to assess the overall optical quality of the lens by comparing the results with a database of similar measurements obtained from a reference set of normal human lenses having various ages. Several metrics have been identified which gauge the optical quality of a given lens relative to the norm for the subject`s chronological age. These metrics may also serve to document accelerated optical aging and/or as early indicators of cataract or other disease processes. 8 figs.

  18. Method for quantifying optical properties of the human lens

    DOEpatents

    Loree, deceased, Thomas R.; Bigio, Irving J.; Zuclich, Joseph A.; Shimada, Tsutomu; Strobl, Karlheinz

    1999-01-01

    Method for quantifying optical properties of the human lens. The present invention includes the application of fiberoptic, OMA-based instrumentation as an in vivo diagnostic tool for the human ocular lens. Rapid, noninvasive and comprehensive assessment of the optical characteristics of a lens using very modest levels of exciting light are described. Typically, the backscatter and fluorescence spectra (from about 300- to 900-nm) elicited by each of several exciting wavelengths (from about 300- to 600-nm) are collected within a few seconds. The resulting optical signature of individual lenses is then used to assess the overall optical quality of the lens by comparing the results with a database of similar measurements obtained from a reference set of normal human lenses having various ages. Several metrics have been identified which gauge the optical quality of a given lens relative to the norm for the subject's chronological age. These metrics may also serve to document accelerated optical aging and/or as early indicators of cataract or other disease processes.

  19. Radiation Pattern and Scattering Properties of Optical Antennas

    NASA Astrophysics Data System (ADS)

    Xu, Zeyan; Messer, Kevin; Yablonovitch, Eli

    When light emitting devices (e.g. LEDs) are coupled with optical antennas of the same resonance frequency, their spontaneous emission rate can be enhanced drastically. The ultimate goal is to have the rate of spontaneous emission faster than the stimulated emission so that the LEDs would be as fast as lasers and enable us to achieve energy efficient interconnects for on-chip communication. In this project, we built multiple optical setups to experimentally measure the far field radiation pattern, light scattering properties and photoluminescence of a series of optical antennas. We also used Lumerical FDTD software to theoretically simulate the structure and found out that the simulated results agree with experimental values. As the longitudinal length increased, the spectrum shifted towards higher wavelengths on the spectrum. Also, by studying the radiation patterns of the optical antennas, we are able to understand their strengths as a function of direction, and how the geometrical shape contribute to the shape of radiation patterns. Understanding the radiation pattern and the scattering spectrum of optical antennas will enable us to design devices with specific requirements on radiational directions and resonance frequencies for optical antennas. This work was funded by National Science Foundation Award ECCS-0939514.

  20. Optical Properties of AC60 Materials

    NASA Astrophysics Data System (ADS)

    Martin, Michael C.

    1996-03-01

    The alkali intercalated fullerene system A_1C_60 (A=K, Rb, or Cs) undergoes a number of structural and electronic phase transitions. At elevated temperatures the structure is fcc, but when cooled below ~ 100 ^circC the structure becomes dependent on the sample's thermal treatment. Infrared and Raman spectroscopic investigations into the various resultant phases will be presented.^1,2 Upon slow cooling, the C_60 molecules form linear conducting polymers^3 which break the icosahedral symmetry of the pure fullerene and thus activate many previously silent vibrational modes. This phase is unexpectedly found to be stable in air.^4 At much lower temperatures (30-60K) a magnetic transition has been observed; we will present IR data obtained in this thermal region showing indications of a gap-like feature. If the samples are cooled very rapidly from high temperatures, an insulating phase is formed where even more symmetry breaking occurs. We argue that a dimerization of C_60, Rb_2(C_60)_2, is the likely structure in accord with the vibrational spectra,^2 and recent x-ray results. Both lower-symmetry phases of AC_60 can also be used to help identify the IR- and Raman-silent modes of unperturbed C_60. Work done at the State University of New York at Stony Brook in collaboration with Daniel Koller, Peter W. Stephens, Laszlo Mihaly (State University of New York at Stony Brook), C. Kendziora and A. Rosenberg (Naval Research Laboratory). Supported by NSF Grant DMR9202528. ^1Michael C. Martin, Daniel Koller, Xiaoqun Du, Peter W. Stephens and Laszlo Mihaly, Phys. Rev. B 49, 10 818 (1994). ^2Michael C. Martin, Daniel Koller, A. Rosenberg, C. Kendziora, and L. Mihaly, Phys. Rev. B 51, 3210 (1995). ^3P.W. Stephens, G. Bortel, G. Faigel, M. Tegze, A. Jánossy, S. Pekker, G. Oszlányi and L. Forro, Nature (London) 370, 636 (1994). ^4Daniel Koller, Michael C. Martin, Peter W. Stephens, Laszlo Mihaly, Sandor Pekker, Andras Jánossy, Olivier Chauvet and Laszlo Forro, Appl. Phys. Lett. 66

  1. Electronic and optical properties of novel carbon allotropes

    SciTech Connect

    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; Jin, Bih -Yaw; Su, Wan -Sheng

    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 the 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.

  2. Electronic and optical properties of novel carbon allotropes

    DOE PAGES

    Wang, Zhanyu; Dong, F.; Shen, B.; ...

    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

  3. Optical properties and ultrafast optical nonlinearity of Yb3+ doped sodium borate and bismuthate glasses

    NASA Astrophysics Data System (ADS)

    Karthikeyan, B.; Suchand Sandeep, C. S.; Cha, Jaemine; Takebe, Hiromichi; Philip, Reji; Mohan, S.

    2008-05-01

    In this paper, we report the optical and ultrafast nonlinear optical properties of Yb3+ doped sodium borate and bismuthate glasses. The glasses have been prepared through the melt quench technique. Optical absorption measurements show compositional dependent absorption spectrum of Yb3+, which is due to the higher crystal field induced by Bi3+ ions. Local structure of the glasses has been identified by using Fourier transform infrared and Raman studies. From open aperture z-scan measurements done by using 100 fs laser pulses, the ultrafast optical nonlinearity in these materials is calculated at the nonresonant excitation wavelength of 800 nm. The measured three-photon absorption originates from the glass host, with contributions from the nonbridging oxygens and the nonlinear electronic polarization of the Bi3+ ions.

  4. 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.

  5. 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.

  6. Optical limiting and nonlinear optical properties of gold-decorated graphene nanocomposites

    NASA Astrophysics Data System (ADS)

    Pradhan, Prabin; Podila, Ramakrishna; Molli, Muralikrishna; Kaniyoor, Adarsh; Sai Muthukumar, V.; Siva Sankara Sai, S.; Ramaprabhu, S.; Rao, A. M.

    2015-01-01

    Metal nanoparticle-decorated low dimensional materials can synergistically combine the nonlinear optical properties of metallic/inorganic nanostructures for enhancing the optical limiting performance. While many materials exhibit excellent optical limiting performance at a relatively higher fluence (>9 J/cm2), there is a still a dearth of optical limiting materials for protecting low damage threshold (<1 J/cm2) photonic devices. Although metal nanoparticle-decorated graphene hybrids are expected to resolve this issue, the rehybridization of metal d-orbitals and graphene p-orbitals often lead to undesirable changes in graphene's electronic structure which adversely affect the nonlinear optical performance. Here, we demonstrate that d-orbitals of Au nanoparticles exhibit little or no rehybridization with graphene and result in an enhanced optical limiting behavior at a low fluence of ∼0.4 J/cm2, which is lower than most metal decorated graphene, carbon nanotube nanocomposites and metal nanoparticles. This optical limiting performance at a lower fluence is attributed to the excellent photo-absorption of Au nanoparticles combined with rapid thermalization of excited carriers by graphene.

  7. Optical properties of functional composite silver nanoparticles and their potential use in reproductive medicine

    NASA Astrophysics Data System (ADS)

    Syrvatka, Vasyl J.; Slyvchuk, Yurij I.; Rozgoni, Ivan I.; Gevkan, Ivan I.; Bilyy, Oleksandr I.

    2013-06-01

    Silver nanoparticles are promising product of nanotechnology with attractive physicochemical and biological properties. The main aim of the study was to investigate optical properties of functional silver nanoparticles with different composite agents: polyvinylpyrrolidone, bovine serum albumin, hyaluronan and to explore their potential using in reproductive medicine. The date obtained in the study showed that surface modification of nanoparticles leads to change of their optical, physicochemical and biological properties. The optical properties of silver nanoparticles display, that AgNPs with PVP and BSA is most stable in PBS than AgNPs with HA. However the absorption curves after 120 hours of storage show, that AgNPs-HA were the most stable in ethanol. Results show, that silver nanoparticles did not effect on sperm viability and motility, but cause a changes of some biochemical parameters of conditioned medium, particular increase the concentration of triglycerides, activity of alkaline phosphatase, lactate dehydrogenase and decrease the activity of aspartate aminotransferase and alanine aminotransferase after 3 h of in vitro cultivation at 37°C. According to our latest data AgNPs with HA have a less toxic effect on biological processes in rabbits sperm compared with AgNPs with PVP and BSA. Nevertheless all functional composites of silver nanoparticles at the concentration of 0.1 μg/mL have no toxic effect on spermatozoa and can be successfully applied in reproductive medicine at low concentrations as signal enhancers, optical sensors, and biomarkers.

  8. Layer number dependent optical properties of multilayer hexagonal BN epilayers

    NASA Astrophysics Data System (ADS)

    Du, X. Z.; Uddin, M. R.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2017-02-01

    Deep ultraviolet photoluminescence emission spectroscopy has been employed to probe the layer number dependent near band-edge transitions above 5 eV in multilayer hexagonal boron nitride (h-BN) epilayers grown by metal-organic chemical vapor deposition. Two emission lines near 5.30 and 5.47 eV were resolved at 10 K. These two emission lines share similar spectroscopic features, and their energy peak separation is nearly independent of the number of layers. The observed energy separation of ˜172 meV coincides well with the in-plane phonon vibration mode, E2g, having an energy of 1370 cm-1 (˜172 meV). The results suggested that the emission line at ˜5.30 eV and ˜5.47 eV are a donor-acceptor-pair transition and its one E2g phonon replica, respectively. When the number of layers decreases from 100 to 8, the emission peak positions (Ep) of both emission lines blueshifted monotonically, indicating the dimensionality effects on the optical properties of h-BN. The layer number dependence of Ep can be described by an empirical formula, which accounts for the variations of the energy bandgap and activation energies of impurities with the number of layers. The results revealed that the impurity activation energies and the carrier-phonon coupling strength increase as the dimensionality of h-BN scales from thick layer to monolayer, suggesting that it is more difficult to achieve conductivity control through doping in monolayer or few-layer h-BN than in thick h-BN.

  9. Solution synthesis, optical properties, and bioimaging applications of silicon nanocrystals.

    PubMed

    McVey, Benjamin F P; Tilley, Richard D

    2014-10-21

    Understanding and unlocking the potential of semiconductor nanocrystals (NCs) is important for future applications ranging from biomedical imaging contrast agents to the next generation of solar cells and LEDs. Silicon NCs (Si NCs) have key advantages compared with other semiconductor NCs due to silicon's high natural abundance, low toxicity and strong biocompatibility, and unique size, and surface dependent optical properties. In this Account, we review and discuss the synthesis, surface modification, purification, optical properties, and applications of Si NCs. The synthetic methods used to make Si NCs have improved considerably in the last 5-10 years; highly monodisperse Si NCs can now be produced on the near gram scale. Scaled-up syntheses have allowed scientists to drive further toward the commercial utilization of Si NCs. The synthesis of doped Si NCs, through addition of a simple elemental precursor to a reaction mixture or by the production of a single source precursor, has shown great promise. Doped Si NCs have demonstrated unique or enhanced properties compared with pure Si NCs, for example, magnetism due to the presence of magnetic metals like Fe and Mn. Surface reactions have reached a new level of sophistication where organic (epoxidation and diol formation) and click (thiol based) chemical reactions can be carried out on attached surface molecules. This has led to a wide range of biocompatible functional groups as well as a degree of emission tuneability. The purification of Si NCs has been improved through the use of size separation columns and size selective precipitation. These purification approaches have yielded highly monodisperse and pure Si NCs previously unachieved. This has allowed scientists to study the size and surface dependent properties and toxicity and enabled the use of Si NCs in biomedical applications. The optical properties of Si NCs are complex. Using a combination of characterization techniques, researchers have explored the

  10. Optical Properties of Alkaline Earth Ions Doped Bismuth Borate Glasses

    SciTech Connect

    Kundu, Virender; Dhiman, R. L.; Maan, A. S.; Goyal, D. R.

    2011-07-15

    The optical properties of glasses with composition xLi{sub 2}O(30-x)Bi{sub 2}O{sub 3}-70B{sub 2}O{sub 3}; x = 0, 5, 10, 15 and 20 mol %, prepared by normal melt quench technique were investigated by means of UV-VIS measurement. It was observed that the optical band gap of the present glass system decreases with increasing Li{sub 2}O content up to 15 mol%, and with further increase in lithium oxide content i.e. x>15 mol% the optical band gap increases. It was also observed that the present glass system behaves as an indirect band gap semiconductor.

  11. 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.

  12. Optical properties of biaxial nanopatterned gold plasmonic nanowired grid polarizer.

    PubMed

    Aas, Lars Martin Sandvik; Kildemo, Morten; Martella, Christian; Giordano, Maria Caterina; Chiappe, Daniele; Buatier de Mongeot, Francesco

    2013-12-16

    Gold nanoparticles deposited on self-organized nano-ripple quartz substrates have been studied by spectroscopic Mueller matrix ellipsometry. The surface was found to have biaxial anisotropic optical properties. For electric field components normal to the ripples the periodic and disconnected nature of the in plane nanowires gives rise to an optical response dominated by the localized plasmon resonance. In the direction parallel to the ripples the gold nanoparticles are aligned closely leading to localized plasmon resonances in the infrared. As Au was deposited at an angle oblique to the surface normal, the gold nanoparticles were formed on the side of the ripples facing the incoming evaporation flux. This makes the gold particles slightly inclined, correspondingly the principal coordinate system of the biaxial dielectric tensor results tilted. The anisotropic plasmonic optical response results in a strong polarizing effect, making it suitable as a plasmonic nanowired grid polarizer.

  13. Optical and transport properties of dense liquid silica

    SciTech Connect

    Qi, Tingting; Millot, Marius; Kraus, Richard G.; Hamel, Sebastien; Root, Seth

    2015-06-15

    Using density-functional-theory based molecular dynamics and the Kubo-Greenwood linear response theory, we evaluated the high-pressure equation of state and the optical and transport properties of quartz and fused silica shock-compressed to 2000 GPa. The computed Hugoniots and corresponding optical reflectivity values are in very good agreement with published data for quartz, and new data that we obtained on fused silica using magnetically launched flyer plate experiments. The rise of optical reflectivity upon shock compression appears to be primarily a temperature-driven mechanism, which is relatively insensitive to small density variation. We observed that the electrical conductivity does not display Drude-like frequency dependence, especially at lower temperatures. In addition, the Wiedemann-Franz relation between electrical and thermal conductivities was found to be invalid. It suggests that even at three-fold compression, warm dense liquid silica on the Hugoniot curve is still far away from the degenerate limit.

  14. Linear and nonlinear magneto-optical properties of monolayer phosphorene

    NASA Astrophysics Data System (ADS)

    Nguyen, Chuong V.; Ngoc Hieu, Nguyen; Duque, C. A.; Quoc Khoa, Doan; Van Hieu, Nguyen; Van Tung, Luong; Vinh Phuc, Huynh

    2017-01-01

    We theoretically study the magneto-optical properties of monolayer phosphorene under a perpendicular magnetic field. We evaluate linear, third-order nonlinear, and total absorption coefficients and relative refractive index changes as functions of the photon energy and the magnetic field, and show that they are strongly influenced by the magnetic field. The magneto-optical absorption coefficients and relative refractive index changes appear in two different regimes: the microwave to THz and the visible frequency. The amplitude of intra-band transition peaks is larger than that of the inter-band transitions. The resonant peaks are blue-shifted with the magnetic field. Our results demonstrate the potential of monolayer phosphorene as a new two-dimensional material for applications in nano-electronic and optical devices as a promising alternative to graphene.

  15. Airborne Lidar Measurements of Aerosol Optical Properties During SAFARI-2000

    NASA Technical Reports Server (NTRS)

    McGill, M. J.; Hlavka, D. L.; Hart, W. D.; Welton, E. J.; Campbell, J. R.; Starr, David OC. (Technical Monitor)

    2002-01-01

    The Cloud Physics Lidar (CPL) operated onboard the NASA ER-2 high altitude aircraft during the SAFARI-2000 field campaign. The CPL provided high spatial resolution measurements of aerosol optical properties at both 1064 nm and 532 nm. We present here results of planetary boundary layer (PBL) aerosol optical depth analysis and profiles of aerosol extinction. Variation of optical depth and extinction are examined as a function of regional location. The wide-scale aerosol mapping obtained by the CPL is a unique data set that will aid in future studies of aerosol transport. Comparisons between the airborne CPL and ground-based MicroPulse Lidar Network (MPL-Net) sites are shown to have good agreement.

  16. Mechanical properties of polyimide coated optical fibers at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Huang, Lei; Dyer, Robert S.; Lago, Ralph J.; Stolov, Andrei A.; Li, Jie

    2016-03-01

    High temperature mechanical strength and reliability of optical fibers have become important subjects as optical fibers are increasingly used for harsher environments. Theories and models of fiber mechanical properties established for traditional telecommunications applications may need to be validated for applications at elevated temperatures. In this paper, we describe the test setup for high temperature tensile strength of fiber and report initial results of dynamic tensile strength of polyimide coated optical fiber at 300 and 350ºC for different heating time intervals. The results are compared with room temperature strength data, data available in the literature, and our earlier work on thermogravimetric analysis (TGA) weight loss of the polyimide coating and the observations on surface morphology at elevated temperatures. Interesting observations are discussed and possible explanations are proposed.

  17. Magneto-optical properties of ABC-stacked trilayer graphene.

    PubMed

    Lin, Yi-Ping; Lin, Chiun-Yan; Ho, Yen-Hung; Do, Thi-Nga; Lin, Ming-Fa

    2015-06-28

    The generalized tight-binding model is developed to investigate the magneto-optical absorption spectra of ABC-stacked trilayer graphene. The absorption peaks can be classified into nine categories of inter-Landau-level optical excitations, including three intra-group and six inter-group ones. Most of them belong to the twin-peak structures because of the asymmetric Landau level spectrum. The threshold absorption peak alone comes from a certain excitation channel, and its frequency is associated with a specific interlayer atomic interaction. The Landau-level anticrossings cause extra absorption peaks. Moreover, a simple relationship between the absorption frequency and the field strength is absent. The magneto-optical properties of ABC-stacked trilayer graphene are totally different from those of AAA- and ABA-stacked ones, such as the number, intensity and frequency of absorption peaks.

  18. Lanthanides-clay nanocomposites: Synthesis, characterization and optical properties

    SciTech Connect

    Celedon, Salvador; Quiroz, Carolina; Gonzalez, Guillermo; Sotomayor Torres, Clivia M.; Benavente, Eglantina

    2009-05-06

    Complexes of Europium(III) and Terbium(III) with 2,2-bipyridine and 1,10-phenanthroline were inserted into Na-bentonite by ion exchange reactions at room temperature. The products display interlaminar distances and stoichiometries in agreement with the ion exchange capacity and the interlayer space available in the clay. The optical properties of the intercalates, being qualitatively similar to those of the free complexes, are additionally improved with respect to exchange processes with the medium, especially in a moist environment. The protection again hydrolysis, together with the intensity of the optical transition {sup 5}D{sub 0}-{sup 5}F{sub 2} observed in the nanocomposite, makes these products promising for the development of novel optical materials.

  19. Optical properties of geometrically optimized graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Bugajny, Paweł; Szulakowska, Ludmiła; Jaworowski, Błazej; Potasz, Paweł

    2017-01-01

    We derive effective tight-binding model for geometrically optimized graphene quantum dots and based on it we investigate corresponding changes in their optical properties in comparison to ideal structures. We consider hexagonal and triangular dots with zigzag and armchair edges. Using density functional theory methods we show that displacement of lattice sites leads to changes in atomic distances and in consequence modifies their energy spectrum. We derive appropriate model within tight-binding method with edge-modified hopping integrals. Using group theoretical analysis, we determine allowed optical transitions and investigate oscillatory strength between bulk-bulk, bulk-edge and edge-edge transitions. We compare optical joint density of states for ideal and geometry optimized structures. We also investigate an enhanced effect of sites displacement which can be designed in artificial graphene-like nanostructures. A shift of absorption peaks is found for small structures, vanishing with increasing system size.

  20. Coastal Benthic Optical Properties (COBOP): Characteristics and Processes Related to Optical Properties of Benthic Marine Organisms and Substrates

    DTIC Science & Technology

    1998-01-01

    coral reef cnidarians in particular. We wish to determine both how biological processes act to determine the optical properties and how optical measurements can be used to provide insight into biological state or process. The objectives for this year’s work were to: (1) Evaluate several methods for separating the fluorescence and reflectance components contributing to spectral signatures under daylight illumination; and (2) Locate specimens that contain only one of each of the coral fluorescent pigments and make excitation and emission measurements for use as

  1. 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.

  2. Active and Passive Coupled-Resonator Optical Waveguides

    NASA Astrophysics Data System (ADS)

    Poon, Joyce Kai See

    Coupled-Resonator Optical Waveguides (CROWs) are chains of resonators in which light propagates by virtue of the coupling between the resonators. The dispersive properties of these waveguides are controllable by the inter-resonator coupling and the geometry of the resonators. If the inter-resonator coupling is weak, light can be engineered to propagate slowly in these structures. The small group velocities possible in CROWs may enable applications in and technologies for optical delay lines, interferometers, buffers, nonlinear optics, and lasers. This thesis reports on achieving and controlling the optical delay in passive and active CROWs. Both theoretical and experimental results are presented. Transfer matrices, tight-binding models, and coupled-mode approaches are developed to analyze and design a variety of coupled resonator systems in the space, frequency, and time domains. Although each analytical method is fundamentally different, in the limit of weak inter-resonator coupling these approaches are consistent with each other. From these formalisms, simple expressions for the delay, loss, bandwidth, and a figure of merit are derived to compare the performance of CROW delay lines. Using a time-domain tight-binding model, we examine the resonant gain enhancement and spontaneous emission noise in amplifying CROWs to find that the net amplification of a propagating wave does not always vary with the group velocity but instead depends on the termination and excitation of the CROW. CROWs in the form of high-order (> 10) weakly coupled passive polymer microring resonators were fabricated and measured. The measured transmission, group delay, and dispersive properties of the CROWs agreed with the theoretical results. Delays in excess of 100 ps and slowing factors of about 25 over bandwidths of about 20 GHz were observed. The main limitation of the passive CROWs was the optical losses. To overcome the losses and to enable electrical integration, we demonstrated active

  3. Optical properties of the ash from El Chichon volcano

    NASA Technical Reports Server (NTRS)

    Patterson, E. M.; Pollard, C. O.; Galindo, I.

    1983-01-01

    The visible wavelength optical properties of the ash from the 1982 El Chichon eruptions are measured using ash samples collected at three surface sites at distances between 12 and 80 km from the volcano. The most distant sample is assumed to be the most representative of the silicate ash injected into the stratosphere. The measured optical properties are presented as a complex refractive index n, while the aerosol absorption is expressed as the imaginary component of the refractive index, n sub IM. Results show that each of these samples exhibited low values of absorption, with n sub IM at 500 nm ranging from 0.0015 for the 12 km sample to 0.001 for the 80 km sample. Based on these measurements, it is estimated that n for the stratospheric silicate ash is given by n = 1.53 - 0.001i.

  4. Optical properties of few layered graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Pratap Choudhary, Raghvendra; Shukla, Shobha; Vaibhav, Kumar; Bhagwan Pawar, Pranav; Saxena, Sumit

    2015-09-01

    Quantum dots provide a unique opportunity to study the confinement effects of electronic wave function on the properties of materials. We have investigated the optical properties of graphene quantum dots synthesized using ultra-fast light-matter interactions followed by one step reduction process. Atomic-scale morphological information suggests the presence of both zigzag and armchair edges in these quantum dots. Optical characterizations were performed using absorption, photoluminescence, and infrared spectroscopy. A shift in the emission spectrum and disappearance of n → π* transition in the absorption spectrum on reduction of the ablated samples confirmed the formation of graphene quantum dots. First principles calculations are in good agreement with the experimentally reported infrared data.

  5. Optical properties of melanin in the skin and skinlike phantoms

    NASA Astrophysics Data System (ADS)

    Bashkatov, Alexey N.; Genina, Elina A.; Kochubey, Vyacheslav I.; Stolnitz, Mikhail M.; Bashkatova, Tatyana A.; Novikova, Olga V.; Peshkova, Anna Y.; Tuchin, Valery V.

    2000-11-01

    Experimental study and computer modeling were used to investigate the optical properties of melanin in the skin and skin-like phantoms. To investigate light scattering by melanosomes in skin we made skin-like phantoms on the base of gelatin with different content of melanin particles. Spectra of total transmittance and diffuse reflectance of the phantoms were obtained in the wavelength range from 400 to 800 nm. Absorption and reduced scattering coefficients of melanin were calculated. Mie theory was used to estimate the optical properties of melanin particles. Wavelength dependence of refractive indices of eumelanin particles (isolated and purified from the ink of the cuttlefish Sepia officinalis) and synthetic melanin particles was estimated.

  6. Research on lunar materials. [optical, chemical, and electrical properties

    NASA Technical Reports Server (NTRS)

    Gold, T.

    1978-01-01

    Abstracts of 14 research reports relating to investigations of lunar samples are presented. The principal topics covered include: (1) optical properties of surface and core samples; (2) chemical composition of the surface layers of lunar grains: Auger electron spectroscopy of lunar soil and ground rock samples; (3) high frequency electrical properties of lunar soil and rock samples and their relevance for the interpretation of lunar radar observations; (4) the electrostatic dust transport process; (5) secondary electron emission characteristics of lunar soil samples and their relevance to the dust transportation process; (6) grain size distribution in surface soil and core samples; and (7) the optical and chemical effects of simulated solar wind (2keV proton and a particle radiation) on lunar material.

  7. Optical modulation of aqueous metamaterial properties at large scale.

    PubMed

    Yang, Sui; Wang, Yuan; Ni, Xingjie; Zhang, Xiang

    2015-11-02

    Dynamical control of metamaterials by adjusting their shape and structures has been developed to achieve desired optical functionalities and to enable modulation and selection of spectra responses. However it is still challenging to realize such a manipulation at large scale. Recently, it has been shown that the desired high (or low) symmetry metamaterials structure in solution can be self-assembled under external light stimuli. Using the this approach, we systematically investiagted the optical controlling process and report here a dynamical manipulation of magnetic properties of metamaterials. Under external laser excitations, we demonstrated that selected magnetic properties of metamaterials can be tuned with the freedom of chosen wavelength ranges. The magnetic dipole selectivity and tunability were further quantified by in situ spectral measurement.

  8. Structural and optical properties of hydrothermally synthesized vanadium oxides nanobelts

    NASA Astrophysics Data System (ADS)

    Derkaoui, I.; Khenfouch, M.; Elmokri, I.; Mothudi, B. M.; Dhlamini, M. S.; Moloi, S. J.; Zorkani, I.; Jorio, A.; Maaza, M.

    2017-03-01

    Nanostructured metal oxides have attracted a lot of attention recently owning to their unique structural advantages, and demonstrated promising chemical and physical properties for various applications. In this study, we report the structural and optical properties of vanadium oxide nanoparticles (VO-NPs) prepared via a hydrothermal method. Our results are revealing that the components of VO-NPs films are having a belt-like shape with a uniform size distribution. The nanobelts with very smooth and flat surfaces have a typical length of up to 1μm and a width of about 9-14 nm. Moreover, The UV-Visible spectroscopy revealed an excellent optical propertiesshowing clearly the good stoichiometry and crystallinity of our VO-NPs films. This synthesis method provides a new simple route to fabricate one-dimensional nanostructured metal oxides which is suitable for a large field of applications.

  9. Critical optical properties of AA-stacked multilayer graphenes

    NASA Astrophysics Data System (ADS)

    Chiu, Chih-Wei; Chen, Szu-Chao; Huang, Yuan-Cheng; Shyu, Feng-Lin; Lin, Ming-Fa

    2013-07-01

    The band structures and optical properties of AA-stacked multilayer graphenes are calculated by the tight-binding model and gradient approximation. For a nL-layer AA-stacked graphene, there are nL peaks at both low and middle frequencies. The threshold energy of odd-layer graphene is much lower than that of even-layer graphene for nL<10. The differences in the electronic structures and optical properties between the odd and even layers are reduced with increasing nL. When nL grows to 30 (200), the spectra of 2D graphene are almost identical to those of 3D graphite at middle (low) frequencies.

  10. Structural and optical properties of distyrylbenzene derivative thin films

    NASA Astrophysics Data System (ADS)

    Ni, J. P.; Ueda, Y.; Hanada, T.; Takada, N.; Ichino, Y.; Yoshida, Y.; Tanigaki, N.; Yase, K.; Wang, D. K.; Wang, F. S.

    1999-12-01

    In order to understand the relationship between the molecular orientation and optical properties of oligophenylenevinylene film, oriented thin films of 1,4-di(p-methoxystyryl)benzene (DSB-1) and 1,4-di(p-methoxystyryl)-2,5-dimethoxybenzene (DSB-2) were fabricated on a potassium bromide (KBr) (001) surface by the vacuum-evaporation method. The structures and optical properties of DSB films have been investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM) and polarized photoluminescence (PL) spectroscopy, respectively. DSB-1 molecules orient obliquely and/or parallel to the substrate surface depending on the substrate temperature. On the other hand, DSB-2 molecules tend to grow epitaxially with the molecular plane parallel to the substrate surface. The anisotropic molecular orientations represent the polarized PL. The epitaxial growth and molecular orientations observed by TEM and AFM at the local and microscopic scale are confirmed by polarized PL measurement on a macroscopic scale.

  11. Homogeneity of material and optical properties in HEM grown sapphire

    NASA Astrophysics Data System (ADS)

    Stout, M.; Hibbard, D.

    2015-09-01

    Sapphire crystal boules, approximately 34 cm in diameter and 22 cm tall, grown by the Heat Exchanger Method (HEM) are currently being sliced, ground and polished for use as window substrates in a variety of aerospace applications. As the need for larger volumes of higher quality material increases, it is necessary to evaluate and understand the homogeneity of optical and material properties within sapphire boules to ensure the needs of the industry can be met. The optical homogeneity throughout the full useable thickness of a representative sapphire boule was evaluated by measuring the transmitted wavefront error of multiple thin slices. This approach allowed the creation of a full-volume three-dimensional homogeneity map. Additionally, the uniformity of other critical characteristics of the material was evaluated at multiple locations within a boule. Specific properties investigated were equibiaxial flexural strength, index of refraction, Knoop hardness, coefficient of thermal expansion and modulus of elasticity. The results of those evaluations will be reported.

  12. Optical properties and electron dynamics in carbon nanodots

    NASA Astrophysics Data System (ADS)

    Wen, Xiaoming; Huang, Shujuan; Conibeer, Gavin; Shrestha, Santosh; Yu, Pyng; Toh, Yon-Rui; Tang, Jau

    2013-12-01

    Carbon nanodots (CNDs) have emerged as fascinating materials with exceptional electronic and optical properties, and thus they offer promising applications in photonics, photovoltaics and photocatalysis. Herein we study the optical properties and electron dynamics in CNDs using steady state and time-resolved spectroscopy. The photoluminescence (PL) is determined to originate from both core and surface. The massive surface fluorophores result in a broad spectral fluorescence. In addition to various synthesis techniques, it is demonstrated that the PL of CNDs can be extended from the blue to the near infrared by thermal assisted growth. Directional electron transfer was observed as fast as femtosecond in CND-graphene oxide nanocomposites from CND into graphene oxide. These results suggest CNDs can be promising in many applications.

  13. Optical properties of non-dilute metal insulator composites

    NASA Astrophysics Data System (ADS)

    Tuncer, Enis; Niklasson, Gunnar A.

    2008-09-01

    The description of the optical properties of metal-insulator composites in the non-dilute region is a long standing problem. In this letter we extract the spectral density function of cobalt-amorphous aluminum oxide composites from optical and near-infrared data. The spectral functions are accurately computed numerically with the help of a recently developed technique. It is observed that the spectral features of the prepared composites change with increasing cobalt content. For low concentrations of cobalt, only one depolarization peak is found that corresponds to the Maxwell Garnett approximation. For concentrations higher than 11% cobalt, three effective depolarization factors are resolved that move towards low spectral parameter values with increasing cobalt content. Such a multi-peak structure arises naturally in fractal equivalent circuit models for the optical properties. A comparison with a deterministic fractal model is presented to illustrate the strength of the spectral density representation and to better comprehend our results. We conclude that the observed behavior gives important information on the relation of the optical characteristics to the composite micro-structure.

  14. 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.

  15. Optical characterization of thermal properties of biological tissue

    NASA Astrophysics Data System (ADS)

    Gutierrez-Arroyo, A.; Sánchez Pérez, C.; Alemán-García, N.; Piña-Barba, C.

    2013-11-01

    In this work we utilize heat conduction measurements trough the photothermal beam deflection technique to characterize thermal properties of biological tissue. We design a heat flux sensor based on the phenomenon of photothermal laser beam deflection within a thermo-optic slab (acrylic), where the deflection is quantified by an optical fiber angle sensor. We analytically model the heat flux sensor response based on heat wave propagation theory that well agree with experimental data. We present heat conduction measurements on different tissues applying a heat pulse. Hence we obtain the thermal effusivity coefficient of bovine tendon and chicken liver and heart. It has been shown that thermal conduction depends on the tissués chemical composition as well on their structural arrangements, so any modification in tissue will affect on heat conduction rendering this method potentially useful as an auxiliary in biomedical studies. Nowadays there are several thermal effusivity and diffusivity measurement techniques with classic calorimetry (using thermistors) for research and industrial applications. However there are only few integrated optical devices already proposed, turning this optical technique in an innovative and alternative sensing system for thermal properties characterization.

  16. Optical properties of transition metal oxide quantum wells

    SciTech Connect

    Lin, Chungwei; Posadas, Agham; Choi, Miri; Demkov, Alexander A.

    2015-01-21

    Fabrication of a quantum well, a structure that confines the electron motion along one or more spatial directions, is a powerful method of controlling the electronic structure and corresponding optical response of a material. For example, semiconductor quantum wells are used to enhance optical properties of laser diodes. The ability to control the growth of transition metal oxide films to atomic precision opens an exciting opportunity of engineering quantum wells in these materials. The wide range of transition metal oxide band gaps offers unprecedented control of confinement while the strong correlation of d-electrons allows for various cooperative phenomena to come into play. Here, we combine density functional theory and tight-binding model Hamiltonian analysis to provide a simple physical picture of transition metal oxide quantum well states using a SrO/SrTiO{sub 3}/SrO heterostructure as an example. The optical properties of the well are investigated by computing the frequency-dependent dielectric functions. The effect of an external electric field, which is essential for electro-optical devices, is also considered.

  17. Optical and electrical properties of nanostructured metallic electrical contacts

    NASA Astrophysics Data System (ADS)

    Toranzos, Victor J.; Ortiz, Guillermo P.; Mochán, W. Luis; Zerbino, Jorge O.

    2017-01-01

    We study the optical and electrical properties of silver films with a graded thickness obtained through metallic evaporation in vacuum on a tilted substrate to evaluate their use as semitransparent electrical contacts. We measure their ellipsometric coefficients, optical transmissions and electrical conductivity for different widths, and we employ an efficient recursive method to calculate their macroscopic dielectric function, their optical properties and their microscopic electric fields. The topology of very thin films corresponds to disconnected islands, while very wide films are simply connected. For intermediate widths the film becomes semicontinuous, multiply connected, and its microscopic electric field develops hotspots at optical resonances which appear near the percolation threshold of the conducting phase, yielding large ohmic losses that increase the absorptance above that of a corresponding homogeneous film. Optimizing the thickness of the film to maximize its transmittance above the percolation threshold of the conductive phase we obtained a film with transmittance T  =  0.41 and a sheet resistance Rs\\text{max}≈ 2.7 Ω . We also analyze the observed emission frequency shift of porous silicon electroluminescent devices when Ag films are used as solid electrical contacts in replacement of electrolytic ones.

  18. Optical properties of transition metal oxide quantum wells

    NASA Astrophysics Data System (ADS)

    Lin, Chungwei; Posadas, Agham; Choi, Miri; Demkov, Alexander A.

    2015-01-01

    Fabrication of a quantum well, a structure that confines the electron motion along one or more spatial directions, is a powerful method of controlling the electronic structure and corresponding optical response of a material. For example, semiconductor quantum wells are used to enhance optical properties of laser diodes. The ability to control the growth of transition metal oxide films to atomic precision opens an exciting opportunity of engineering quantum wells in these materials. The wide range of transition metal oxide band gaps offers unprecedented control of confinement while the strong correlation of d-electrons allows for various cooperative phenomena to come into play. Here, we combine density functional theory and tight-binding model Hamiltonian analysis to provide a simple physical picture of transition metal oxide quantum well states using a SrO/SrTiO3/SrO heterostructure as an example. The optical properties of the well are investigated by computing the frequency-dependent dielectric functions. The effect of an external electric field, which is essential for electro-optical devices, is also considered.

  19. Using DFT Methods to Study Activators in Optical Materials

    DOE PAGES

    Du, Mao-Hua

    2015-08-17

    Density functional theory (DFT) calculations of various activators (ranging from transition metal ions, rare-earth ions, ns2 ions, to self-trapped and dopant-bound excitons) in phosphors and scintillators are reviewed. As a single-particle ground-state theory, DFT calculations cannot reproduce the experimentally observed optical spectra, which involve transitions between multi-electronic states. However, DFT calculations can generally provide sufficiently accurate structural relaxation and distinguish different hybridization strengths between an activator and its ligands in different host compounds. This is important because the activator-ligand interaction often governs the trends in luminescence properties in phosphors and scintillators, and can be used to search for new materials.more » DFT calculations of the electronic structure of the host compound and the positions of the activator levels relative to the host band edges in scintillators are also important for finding optimal host-activator combinations for high light yields and fast scintillation response. Mn4+ activated red phosphors, scintillators activated by Ce3+, Eu2+, Tl+, and excitons are shown as examples of using DFT calculations in phosphor and scintillator research.« less

  20. Using DFT Methods to Study Activators in Optical Materials

    SciTech Connect

    Du, Mao-Hua

    2015-08-17

    Density functional theory (DFT) calculations of various activators (ranging from transition metal ions, rare-earth ions, ns2 ions, to self-trapped and dopant-bound excitons) in phosphors and scintillators are reviewed. As a single-particle ground-state theory, DFT calculations cannot reproduce the experimentally observed optical spectra, which involve transitions between multi-electronic states. However, DFT calculations can generally provide sufficiently accurate structural relaxation and distinguish different hybridization strengths between an activator and its ligands in different host compounds. This is important because the activator-ligand interaction often governs the trends in luminescence properties in phosphors and scintillators, and can be used to search for new materials. DFT calculations of the electronic structure of the host compound and the positions of the activator levels relative to the host band edges in scintillators are also important for finding optimal host-activator combinations for high light yields and fast scintillation response. Mn4+ activated red phosphors, scintillators activated by Ce3+, Eu2+, Tl+, and excitons are shown as examples of using DFT calculations in phosphor and scintillator research.

  1. Microscopic modeling of the effect of phonons on the optical properties of solid-state emitters

    NASA Astrophysics Data System (ADS)

    Norambuena, Ariel; Reyes, Sebastián A.; Mejía-Lopéz, José; Gali, Adam; Maze, Jerónimo R.

    2016-10-01

    Understanding the effect of vibrations in optically active nanosystems is crucial for successfully implementing applications in molecular-based electro-optical devices, quantum information communications, single photon sources, and fluorescent markers for biological measurements. Here, we present a first-principles microscopic description of the role of phonons on the isotopic shift presented in the optical emission spectrum associated to the negatively charged silicon-vacancy color center in diamond. We use the spin-boson model and estimate the electron-phonon interactions using a symmetrized molecular description of the electronic states and a force-constant model to describe molecular vibrations. Group theoretical arguments and dynamical symmetry breaking are presented in order to explain the optical properties of the zero-phonon line and the isotopic shift of the phonon sideband.

  2. Optical properties of natural phenols in aqueous media

    NASA Astrophysics Data System (ADS)

    Vusovich, Olga; Sultimova, Natalia; Tchaikovskaya, Olga; Sokolova, Irina; Vasilieva, Nina

    2015-11-01

    Currently, the study of the photochemistry of natural phenols is relevant as it has a fundamental and a practical importance. The optical properties of natural phenols are studied: 3-methoxy-4-hydroxybenzaldehyde (vanillin) and 3- hydroxy-4-methoxybenzaldehyde (isovanillin), 4-hydroxy-3-methoxybenzoic acid (vanillic acid). The processes of proton transfer in the investigated molecules in ground and excited states under exposure to lamp and laser emissions are presented using the methods of electron spectroscopy and quantum chemistry.

  3. Photoinduced nanocomposites—creation, modification, linear and nonlinear optical properties

    NASA Astrophysics Data System (ADS)

    Bityurin, N.; Alexandrov, A.; Afanasiev, A.; Agareva, N.; Pikulin, A.; Sapogova, N.; Soustov, L.; Salomatina, E.; Gorshkova, E.; Tsverova, N.; Smirnova, L.

    2013-07-01

    UV irradiation of materials consisting of a polymer matrix that possesses precursors of noble metals followed by annealing results in creation of metal nanoparticles within the irradiated domains. Such photoinduced nanocomposites are promising for photonics applications due to the strong alteration of their optical properties compared to initial nonirradiated materials. We report our results on the synthesis and investigation of two kinds of these materials: (a) Photoinduced Au nanocomposites based on PMMA matrices, including bulk materials prepared by means of the polymerization technique;

  4. Optical properties of particles in planetary atmospheres - Laboratory studies

    NASA Technical Reports Server (NTRS)

    Williams, D.

    1974-01-01

    The laboratory techniques employed for the determination of optical constants are discussed briefly. The values obtained for the real n and imaginary k parts of the refractive indices of water, ice, and liquid ammonia are presented graphically. Work currently in progress on solid ammonia and on sulphuric acid is discussed. Other approaches to studies of the properties of aerosols in planetary atmospheres are presented briefly.

  5. Revisiting the optical properties of the FMO protein

    PubMed Central

    Milder, Maaike T. W.; Brüggemann, Ben; van Grondelle, Rienk

    2010-01-01

    We review the optical properties of the FMO complex as found by spectroscopic studies of the Qy band over the last two decades. This article emphasizes the different methods used, both experimental and theoretical, to elucidate the excitonic structure and dynamics of this pigment–protein complex. Electronic supplementary material The online version of this article (doi:10.1007/s11120-010-9540-1) contains supplementary material, which is available to authorized users. PMID:20229036

  6. Tomography and optical properties of silver nano-inukshuk

    SciTech Connect

    Ghosh, Tanmay; Das, Pabitra; Ghosh, Tapas; Satpati, Biswarup

    2015-06-24

    Following a simple dip-and-rinse galvanic displacement reaction silver nano-inukshuks were prepared directly on germanium surfaces. Morphology, 3-dimensional (3D) structure, chemical composition and optical properties of the silver nanostructurs were investigated using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and cathodoluminescence (CL) spectroscopy. Exact 3D morphology was reconstructed in the by tomography mode of TEM.

  7. Determination of optical properties of oxidative bleaching human dental tissue samples using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Ni, Y. R.; Guo, Z. Y.; Shu, S. Y.; Zeng, C. C.; Zhong, H. Q.; Chen, B. L.; Liu, Z. M.; Bao, Y.

    2011-10-01

    Oxidative bleaching changes of human teeth induced changes in the optical properties of dental tissue. We introduced 1310 nm wavelengths of optical coherence tomography (OCT) attenuation coefficient method which is a relatively novel and rarely reported methodology to measure the correlation coefficient during the teeth oxidative bleaching procedure. And the quantitative parameters of enamel optical thickness and disruption of the entrance signal (DES) were extracted from the OCT images. The attenuation coefficient of the bleached tissue is 6.2 mm-1 which is significant (p < 0.001) higher than that unbleached sample is 1.4 mm-1. But attenuation coefficient varied significantly (p < 0.001) between 5.9 and 1.5 mm-1 in dentine which is downtrend. Furthermore, the persistence of bleaching oxidation in 35% hydrogen peroxide-induced optical thickness of enamel is similar with unbleached tissue which may indicate the refractive index of enamel is unchanged. Moreover, disruption of the entrance signal (DES) analysis showed that remarkable difference was appeared at enamel surface. The results indicate that optical properties of oxidative bleaching human dental tissue can be determined by attenuation coefficient using OCT system.

  8. Growth, processing and properties of CVD diamond for optical applications

    NASA Astrophysics Data System (ADS)

    Snail, Keith A.

    1992-11-01

    In recent years there has been an increased need for optical materials for use in adverse chemical, thermal, abrasive, and/or radiation environments. Diamond is a natural candidate for many of these applications because of its radiation hardness, superb resistance to chemical attack and abrasive wear, high thermal conductivity, and low absorption coefficient throughout the visible and much of the infrared. The use of synthetic (high pressure-high temperature) and natural diamond in optical components has been limited by the size and shapesof available crystals, and the inability to coat optical elements. The chemical vapor deposition (CVD) of polycrystalline diamond does not suffer the same limitations, and is therefore the focus of an expanding worldwide research effort. CVD diamond is not without its own shortcomings, however, and in this paper a status report is given on the obstacles and current research related to using CVD diamond as an optical material. Natural diamond's relevant physical properties and the optical applications envisioned for CVD diamond are also discussed.

  9. Automated mineral identification algorithm using optical properties of crystals

    NASA Astrophysics Data System (ADS)

    Aligholi, Saeed; Khajavi, Reza; Razmara, Morteza

    2015-12-01

    A method has been developed to automatically characterize the type of mineral phases by means of digital image analysis using optical properties of crystals. The method relies on microscope automation, digital image acquisition, image processing and analysis. Two hundred series of digital images were taken from 45 standard thin sections using a digital camera mounted on a conventional microscope and then transmitted to a computer. CIELab color space is selected for the processing, in order to effectively employ its well-defined color difference metric for introducing appropriate color-based feature. Seven basic optical properties of minerals (A. color; B. pleochroism; C. interference color; D. birefringence; E. opacity; F. isotropy; G. extinction angle) are redefined. The Local Binary Pattern (LBP) operator and modeling texture is integrated in the Mineral Identification (MI) scheme to identify homogeneous regions in microscopic images of minerals. The accuracy of mineral identification using the method was %99, %98, %96 and %95 for biotite, hornblende, quartz and calcite minerals, respectively. The method is applicable to other minerals and phases for which individual optical properties of crystals do not provide enough discrimination between the relevant phases. On the basis of this research, it can be concluded that if the CIELab color space and the local binary pattern (LBP) are applied, it is possible to recognize the mineral samples with the accuracy of more than 98%.

  10. Optical properties of dielectric thin films including quantum dots

    NASA Astrophysics Data System (ADS)

    Flory, F.; Chen, Y. J.; Lee, C. C.; Escoubas, L.; Simon, J. J.; Torchio, P.; Le Rouzo, J.; Vedraine, S.; Derbal-Habak, Hassina; Ackermann, Jorg; Shupyk, Ivan; Didane, Yahia

    2010-08-01

    Depending on the minimum size of their micro/nano structure, thin films can exhibit very different behaviors and optical properties. From optical waveguides down to artificial anisotropy, through diffractive optics and photonic crystals, the application changes when decreasing the minimum feature size. Rigorous electromagnetic theory can be used to model most of the components but when the size is of a few nanometers, quantum theory has also to be used. These materials including quantum structures are of particular interest for other applications, in particular for solar cells, because of their luminescent and electronic properties. We show that the properties of electrons in multiple quantum wells can be easily modeled with a formalism similar to that used for multilayer waveguides. The effects of different parameters, in particular coupling between wells and well thickness dispersion, on possible discrete energy levels or energy band of electrons and on electron wave functions is given. When such quantum confinement appears the spectral absorption and the extinction coefficient dispersion with wavelength is modified. The dispersion of the real part of the refractive index can then be deduced from the Kramers- Krönig relations. Associated with homogenization theory this approach gives a new model of refractive index for thin films including quantum dots. Absorption spectra of samples composed of ZnO quantum dots in PMMA layers are in preparation are given.

  11. Optical and structural properties of zinc iodine thin films

    NASA Astrophysics Data System (ADS)

    Kariper, İ. A.

    2015-06-01

    Zinc iodide (ZnI2) crystalline thin film is produced with chemical bath deposition on substrates (commercial glass). The pH of chemical bath is scanned with controlled potassium hydroxide. Some properties of films changed with pH and changes of pH were analyzed. The pH values are scanned at 6.01-6.29. Transmittance, absorption, optical band gap and refractive index are investigated by UV/Vis. spectrum. The hexagonal and tetragonal form in structural properties in XRD at pH: 6.01 were seen. The pH of bath was up to 6.01, KZnI3ṡ2H2O (orthorhombic), KZnI3ṡ(H2O)2 (orthorhombic), ZnI2 (tetragonal) and ZnI2 (hexagonal) forms were observed in XRD patterns. The structural and optical properties of ZnI2 thin films analyzed at different pH. SEM analysis studied for surface analysis in films. The SEM analyses were agreed with XRD patterns. The optical band gap increased with pH between 3.4 and 3.6 eV. The film thickness changed with pH at 108-345 nm. Also refractive index and transmission generally increased with pH.

  12. THz - ToF Optical Layer Analysis (OLA) to determine optical properties of dielectric materials

    NASA Astrophysics Data System (ADS)

    Spranger, Holger; Beckmann, Jörg

    2017-02-01

    Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. The knowledge of the base materials shape and optical properties is essential for a proper reconstruction result. To obtain these properties a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric characteristics. The Optical Layer Analysis (OLA) is able to fulfill these requirements. A short description why the optical properties are crucial for meaningful SAFT reconstruction results will be given first. Afterwards the OLA will be derived and applied on representative samples to discuss and evaluate its benefits and limits.

  13. Ocean Optics Protocols for Satellite Ocean Color Sensor Validation. Volume 4; Inherent Optical Properties: Instruments, Characterizations, Field Measurements and Data Analysis Protocols; Revised

    NASA Technical Reports Server (NTRS)

    Mueller, J. L. (Editor); Fargion, Giuletta S. (Editor); McClain, Charles R. (Editor); Pegau, Scott; Zaneveld, J. Ronald V.; Mitchell, B. Gregg; Kahru, Mati; Wieland, John; Stramska, Malgorzat

    2003-01-01

    This document stipulates protocols for measuring bio-optical and radiometric data for the Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project activities and algorithm development. The document is organized into 6 separate volumes as Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 4. Volume I: Introduction, Background and Conventions; Volume II: Instrument Specifications, Characterization and Calibration; Volume III: Radiometric Measurements and Data Analysis Methods; Volume IV: Inherent Optical Properties: Instruments, Characterization, Field Measurements and Data Analysis Protocols; Volume V: Biogeochemical and Bio-Optical Measurements and Data Analysis Methods; Volume VI: Special Topics in Ocean Optics Protocols and Appendices. The earlier version of Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 3 (Mueller and Fargion 2002, Volumes 1 and 2) is entirely superseded by the six volumes of Revision 4 listed above.

  14. Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 4, Volume IV: Inherent Optical Properties: Instruments, Characterizations, Field Measurements and Data Analysis Protocols

    NASA Technical Reports Server (NTRS)

    Mueller, J. L.; Fargion, G. S.; McClain, C. R. (Editor); Pegau, S.; Zanefeld, J. R. V.; Mitchell, B. G.; Kahru, M.; Wieland, J.; Stramska, M.

    2003-01-01

    This document stipulates protocols for measuring bio-optical and radiometric data for the Sensor Intercomparision and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project activities and algorithm development. The document is organized into 6 separate volumes as Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 4. Volume I: Introduction, Background, and Conventions; Volume II: Instrument Specifications, Characterization and Calibration; Volume III: Radiometric Measurements and Data Analysis Methods; Volume IV: Inherent Optical Properties: Instruments, Characterization, Field Measurements and Data Analysis Protocols; Volume V: Biogeochemical and Bio-Optical Measurements and Data Analysis Methods; Volume VI: Special Topics in Ocean Optics Protocols and Appendices. The earlier version of Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 3 is entirely superseded by the six volumes of Revision 4 listed above.

  15. Associations Between the Molecular and Optical Properties of Dissolved Organic Matter in the Florida Everglades, a Model Coastal Wetland System

    PubMed Central

    Wagner, Sasha; Jaffé, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-01-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source, and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial, and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275−295, S350−400, SR, FI, freshness index, and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman's rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance, and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands. PMID:26636070

  16. Associations between the molecular and optical properties of dissolved organic matter in the Florida Everglades, a model coastal wetland system

    NASA Astrophysics Data System (ADS)

    Wagner, Sasha; Jaffe, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-11-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial and marine). As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275-295, S350-400, SR, FI, freshness index and HIX) and ultrahigh resolution mass spectrometry (FTICR-MS). Spearman’s rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands.

  17. Non-linear optical titanyl arsenates: Crystal growth and properties

    NASA Astrophysics Data System (ADS)

    Nordborg, Jenni Eva Louise

    Crystals are appreciated not only for their appearance, but also for their unique physical properties which are utilized by the photonic industry in appliances that we come across every day. An important part of enabling the technical use of optical devices is the manufacture of crystals. This dissertation deals with a specific group of materials called the potassium titanyl phosphate (KIP) family, known for their non-linear optical and ferroelectric properties. The isomorphs vary in their linear optical and dielectric properties, which can be tuned to optimize device performance by forming solid solutions of the different materials. Titanyl arsenates have a wide range of near-infrared transmission which makes them useful for tunable infrared lasers. The isomorphs examined in the present work were primarily RbTiOASO4 (RTA) and CsTiOAsO4 (CTA) together with the mixtures RbxCs 1-xTiOAsO4 (RCTA). Large-scale crystals were grown by top seeding solution growth utilizing a three-zone furnace with excellent temperature control. Sufficiently slow cooling and constant upward lifting produced crystals with large volumes useable for technical applications. Optical quality RTA crystals up to 10 x 12 x 20 mm were grown. The greater difficulty in obtaining good crystals of CTA led to the use of mixed RCTA materials. The mixing of rubidium and cesium in RCTA is more favorable to crystal growth than the single components in pure RTA and CTA. Mixed crystals are rubidium-enriched and contain only 20-30% of the cesium concentration in the flux. The cesium atoms show a preference for the larger cation site. The network structure is very little affected by the cation substitution; consequently, the non-linear optical properties of the Rb-rich isomorphic mixtures of RTA and CTA can be expected to remain intact. Crystallographic methods utilizing conventional X-ray tubes, synchrotron radiation and neutron diffraction have been employed to investigate the properties of the atomic

  18. Cloud optical properties and phase discrimination using transmitted spectral radiance

    NASA Astrophysics Data System (ADS)

    LeBlanc, S. E.; Pilewskie, P.; Schmidt, S.; Coddington, O.

    2013-12-01

    Cloud optical thickness, effective radius, and thermodynamic phase are commonly retrieved from satellite measurements of reflected light. Reflected light is influenced most strongly by droplets and ice crystals near cloud top, whereas transmitted light has interacted with cloud particles throughout the entire layer. This transmitted spectral radiance is used in a new method to retrieve cloud thermodynamic phase, cloud optical thickness, and effective radius. The method uses 15 regions of the shortwave transmittance spectrum that are modulated by the spectral absorption and scattering by liquid water droplets and ice particles. Spectral features in these regions are characterized by their slope, normalized magnitude, spectral derivatives, spectral curvature, and second derivatives. We use an optimal estimation method to find the most likely set of cloud optical thickness, effective radius, and thermodynamic phase that produces the observed spectral features in transmitted radiance spectra. This retrieval's performance is evaluated using the GEneralized Nonlinear Retrieval Analysis (GENRA) with the Shannon information content. Results showed that the normalized Shannon information content for retrieved ice cloud properties was larger on average (84%) than for liquid water cloud properties (78%) in addition to having a smaller bias. The retrieval was applied to zenith spectral radiance measured with the ground-based Solar Spectral Flux Radiometer (SSFR) located at Boulder, Colorado for 10 cases that occurred between May 2012 and January 2013. Retrieved cloud optical thickness, effective radius, and their uncertainties are compared to those retrieved using two other methods. By using several spectral characterizations in a large number of spectral bands, the average uncertainty in retrieved optical thickness and effective radius is reduced below that of any other retrieval method based on cloud transmittance.

  19. Morphology dependence of the optical properties of DALM related materials[Diazoluminomelanin

    SciTech Connect

    Wagner-Brown, K.B.; Ferris, K.F.; Kiel, J.L.; Albanese, R.A.

    1998-07-01

    Diazoluminomelanin (DALM) is an electroluminescent polymer which has shown significant optical activity in response to perturbing fields. The current model for this process features optical excitation of a polymer backbone containing conducting conjugation, with subsequent energy transfer to a luminescent group. In this paper the authors have performed electronic structure calculations using the AM1 Hamiltonian with configuration interaction to estimate the electronic properties of two potential models for the DALM backbone. Contrary to the conventional picture of conjugation, the phenyl groups in the DALM backbone show significant twist angles (42--55{degree}) depending on substitutional group, resulting in localized electronic excitations.

  20. Clinical determination of tissue optical properties by endoscopic spatially resolved reflectometry

    NASA Astrophysics Data System (ADS)

    Bays, Roland; Wagnières, Georges; Robert, Dimitri; Braichotte, Daniel; Savary, Jean-François; Monnier, Philippe; van den Bergh, Hubert

    1996-04-01

    A noninvasive method to measure the optical properties of a diffusing and absorbing medium is described. Based on the spatially resolved measurement of diffuse reflectance at the sample surface, this method is particularly suitable for investigating the in vivo optical properties of biological tissues endoscopically in a clinical context. The sensitivity of the measurement is discussed, and two optical probes for two different clinical applications are presented. Preliminary measurements are performed on a nonbiological medium, which illustrate the possibilities of the proposed method. Finally, we report on in vivo measurements of the optical properties of the human esophageal wall at 630 nm. optical probe, optical properties, scattering.

  1. Vertically Resolved Aerosol Optical Properties over the ARM SGP Site

    NASA Technical Reports Server (NTRS)

    Schmid, B.; Jonsson, H.; Strawa, A.; Provencal, B.; Covert, D.; Arnott, P.; Bucholtz, A.; Pilewskie, P.; Pommier, J.; Rissman, T.

    2003-01-01

    In order to meet one of its goals - to relate observations of radiative fluxes and radiances to the atmospheric composition - the Department of Energy's Atmospheric Radiation Measurement (ARM) program has pursued measurements and modeling activities that attempt to determine how aerosols impact atmospheric radiative transfer, both directly and indirectly. However, significant discrepancies between aerosol properties measured in situ or remotely remain. To this end, the ARM program will conduct an Aerosol Intensive Operational Period (IOP) in May 2003 at the ARM Southern Great Plains (SGP) site in north central Oklahoma. The IOP involves airborne measurements from two airplanes over the heavily instrumented SGP site. We will give an overview of early airborne results obtained aboard Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. The aircraft will carry instrumentation to perform in-situ measurements of aerosol absorption, scattering, extinction and particle size including such novel techniques as the photoacoustic and cavity ring-down methods. Aerosol optical depth and extinction will be measured with the NASA Ames Airborne Tracking 14-channel sunphotometer. Furthermore up- and downwelling solar (broadband and spectral) and infrared radiation will be measured using three different instruments. The up-looking radiation instruments will be mounted on a newly developed stabilized platform, which will keep the instruments level up to aircraft pitch and roll angles of 10 degrees. Additional effort will be directed toward measurement of cloud condensation nucleus concentration as a function of supersaturation and relating CCN concentration to aerosol composition and size distribution. This relation is central to description of the aerosol indirect effect.

  2. Autofluorescence And Other Optical Properties As Tools In Biological Oceanography

    NASA Astrophysics Data System (ADS)

    Cullen, John J.; Yentsch, Clarice M.; Cucci, Terry L.; MacIntyre, Hugh L.

    1988-08-01

    Bulk fluorescence measurements have been popular in algal culture studies and in oceanographic and limnological applications. Usually, fluorescence is interpreted as an indicator of chlorophyll concentration or phytoplankton biomass, but sometimes measurements of fluorescence can be related to physiological properties of phytoplankton, such as responses to light. Now that in situ fluorometers are being deployed routinely with optical packages, there is active interest in interpreting the relationships between fluorescence, beam transmission, diffuse attenuation, and the physiological characteristics of phytoplankton. Flow cytometry offers the potential to extend these interpretations to the scale of individual cells. It may be difficult to compare measurements of fluorescence, however, because instruments differ greatly in excitation irradiance and time scale of measurement. With this in mind, we examined the short-term responses of a marine diatom to bright light, comparing different instruments (SeaTech in situ fluorometer, Turner Designs fluorometer, EPICS flow cytometer, FACS Analyzer, SeaTech beam transmissometer) while making concurrent measurements of photosynthesis vs irradiance and absorption spectra. Each fluorometer yielded somewhat different information, yet all showed a similar pattern of inhibition after exposure. One instrument, the in situ pulsed fluorometer, could show rapid changes of fluorescence immediately after large shifts of irradiance. Beam attenuation did not decline with the bright light treatment, nor did the specific absorption of chlorophyll. Photosynthetic efficiency was reduced after exposure to bright light, but the capacity for photosynthesis in high irradiance increased at the same time. These results are preliminary: nonetheless they support some interpretations of fluorescence/beam attenuation ratios, clarify some aspects of photosynthetic response to bright light, and suggest that flow cytometry may be useful for assessing

  3. Structural Properties of Potexvirus Coat Proteins Detected by Optical Methods.

    PubMed

    Semenyuk, P I; Karpova, O V; Ksenofontov, A L; Kalinina, N O; Dobrov, E N; Makarov, V V

    2016-12-01

    It has been shown by X-ray analysis that cores of coat proteins (CPs) from three potexviruses, flexible helical RNA-containing plant viruses, have similar α-helical structure. However, this similarity cannot explain structural lability of potexvirus virions, which is believed to determine their biological activity. Here, we used circular dichroism (CD) spectroscopy in the far UV region to compare optical properties of CPs from three potexviruses with the same morphology and similar structure. CPs from Alternanthera mosaic virus (AltMV), potato aucuba mosaic virus (PAMV), and potato virus X (PVX) have been studied in a free state and in virions. The CD spectrum of AltMV virions was similar to the previously obtained CD spectrum of papaya mosaic virus (PapMV) virions, but differed significantly from the CD spectrum of PAMV virions. The CD spectrum of PAMV virions resembled in its basic characteristics the CD spectrum of PVX virions characterized by molar ellipticity that is abnormally low for α-helical proteins. Homology modeling of the CP structures in AltMV, PAMV, and PVX virions was based on the known high-resolution structures of CPs from papaya mosaic virus and bamboo mosaic virus and confirmed that the structures of the CP cores in all three viruses were nearly identical. Comparison of amino acid sequences of different potexvirus CPs and prediction of unstructured regions in these proteins revealed a possible correlation between specific features in the virion CD spectra and the presence of disordered N-terminal segments in the CPs.

  4. Determination of tissue optical properties in PDT treated Head & Neck patients

    PubMed Central

    Dimofte, Andreea; Finlay, Jarod C.; Sharikova, Anna V.; Cengel, Keith A.; Ahn, Peter; Busch, Theresa M.; Zhu, Timothy C.

    2015-01-01

    Determination of optical properties (absorption (μa) and scattering (μs′) coefficients) in human tissue is important when it comes to accurate calculation of fluence rate in and around tissue area. ALA application to the tissue induces production of protoporphyrin IX when activated by red light. Changes in the tissue optical properties can send information such as treatment outcome and tissue drug concentration. Patients in this study were treated with PDT for head and neck mucosal dysplasia. They were enrolled in a phase I study of escalating light doses and oral ALA with 60mg/kg. Red light at 630nm was administered to the tumor from a laser. The light dose was escalated from 50–200J/cm2 with a measured fluence rate at tissue surface of 100mW/cm2. We developed a light detection device for the purpose of determining optical properties in vivo using the semi-infinite method. The light detection device consists of two parallel, placed 5mm apart. In one of the catheters a 2 mm long linear diffusing light source is placed while in the second catheter, a calibrated isotropic detector is placed. The detector is scanned along the length of the light source containing catheter. Scans are done with the device placed on the treatment area (tumor) and on the normal tissue. Optical properties were measured in-vivo before and after PDT delivery for both normal tissue and tumor. PMID:25999648

  5. Retrieval of Aerosol Optical Properties under Thin Cirrus from MODIS

    NASA Technical Reports Server (NTRS)

    Lee, Jaehwa; Hsu, Nai-Yung Christina; Bettenhausen, Corey; Sayer, Andrew Mark.

    2014-01-01

    Retrieval of aerosol optical properties using shortwave bands from passive satellite sensors, such as MODIS, is typically limited to cloud-free areas. However, if the clouds are thin enough (i.e. thin cirrus) such that the satellite-observed reflectance contains signals under the cirrus layer, and if the optical properties of this cirrus layer are known, the TOA reflectance can be corrected for the cirrus layer to be used for retrieving aerosol optical properties. To this end, we first correct the TOA reflectances in the aerosol bands (0.47, 0.55, 0.65, 0.86, 1.24, 1.63, and 2.12 micron for ocean algorithm and 0.412, 0.47, and 0.65 micron for deep blue algorithm) for the effects of thin cirrus using 1.38 micron reflectance and conversion factors that convert cirrus reflectance in 1.38 micron band to those in aerosol bands. It was found that the conversion factors can be calculated by using relationships between reflectances in 1.38 micron band and minimum reflectances in the aerosol bands (Gao et al., 2002). Refer to the example in the figure. Then, the cirrus-corrected reflectance can be calculated by subtracting the cirrus reflectance from the TOA reflectance in the optically thin case. A sensitivity study suggested that cloudy-sky TOA reflectances can be calculated with small errors in the form of simple linear addition of cirrus-only reflectances and clear-sky reflectances. In this study, we correct the cirrus signals up to TOA reflectance at 1.38 micron of 0.05 where the simple linear addition is valid without extensive radiative transfer simulations. When each scene passes the set of tests shown in the flowchart, the scene is corrected for cirrus contamination and passed into aerosol retrieval algorithms.

  6. 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

  7. Active Learning Environment with Lenses in Geometric Optics

    ERIC Educational Resources Information Center

    Tural, Güner

    2015-01-01

    Geometric optics is one of the difficult topics for students within physics discipline. Students learn better via student-centered active learning environments than the teacher-centered learning environments. So this study aimed to present a guide for middle school teachers to teach lenses in geometric optics via active learning environment…

  8. Spatial ordering and abnormal optical activity of DNA liquid-crystalline dispersion particles

    NASA Astrophysics Data System (ADS)

    Semenov, S. V.; Yevdokimov, Yu. M.

    2016-12-01

    In our work, we investigate physicochemical and optical properties of double-strand DNA dispersions. The study of these properties is of biological interest, because it allows one to describe the characteristics of certain classes of chromosomes and DNA containing viruses. The package pattern of DNA molecules in the dispersions particles (DP) is examined. The consideration of the DNA liquid-crystalline DP optical activity based on the theory of electromagnetic wave absorption by large molecular aggregates has been performed. The investigation is also focused on various effects induced by the interaction between biological active compounds and DNA in the content of liquid-crystalline DP.

  9. Facile growth of barium oxide nanorods: structural and optical properties.

    PubMed

    Ahmad, Naushad; Wahab, Rizwan; Alam, Manawwer

    2014-07-01

    This paper reports a large-scale synthesis of barium oxide nanorods (BaO-NRs) by simple solution method at a very low-temperature of - 60 degrees C. The as-grown BaO-NRs were characterized in terms of their morphological, structural, compositional, optical and thermal properties. The morphological characterizations of as-synthesized nanorods were done by scanning electron microscopy (SEM) which confirmed that the synthesized products are rod shaped and grown in high density. The nanorods exhibits smooth and clean surfaces throughout their lengths. The crystalline property of the material was analyzed with X-ray diffraction pattern (XRD). The compositional and thermal properties of synthesized nanorods were observed via Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis which confirmed that the synthesized nanorods are pure BaO and showed good thermal stability. The nanorods exhibited good optical properties as was confirmed from the room-temperature UV-vis spectroscopy. Finally, a plausible mechanism for the formation of BaO-NRs is also discussed in this paper.

  10. Optical and Structural Properties of Thin Film Composites.

    NASA Astrophysics Data System (ADS)

    Gibson, Ursula Jane

    This work describes the optical and structural characterization of metal-insulator and bimetallic composite films. Included are experimental details, theoretical descriptions of these systems, and a correlation of the optical response and microstructure of these thin film systems. The films were made by simultaneous or sequential evaporation of the constituents onto either amorphous or single crystal substrates. Two reflectance and one transmittance measurements were combined and inverted to determine the intrinsic optical constants of these materials over the wavelength range 0.2 to 3.0 microns. The metal insulator systems studied were Au-Al(,2)O(,3) and Au-MgO. The optical behavior and transport properties of these materials were measured, and correlated with their disparate microstructures. The optical behavior was compared to the predictions of three effective medium theories, labelled as the Maxwell-Garnett, Bruggeman Self-Consistent and Probabilistic Growth theories. The differing topological assumptions which form the bases of these theories were correlated with microscopic examination of the morphologies of the films, and it was found that the simple theories adequately predicted the optical response of the composites. Bimetallic systems were also studied, to investigate the extension of the Bruggeman theory to symmetric composites of immiscible metal constituents. It was found that the theory adequately predicts the behavior of films which display the symmetric morphology assumed by the theory. Studies of non-symmetric composites, and anisotropic systems (such as epitaxial layered materials (ELMs), showed that the symmetric morphology is necessary in order to model these systems with the Bruggeman theory.

  11. Optical and thermodynamic property measurements of liquid metals and alloys

    NASA Astrophysics Data System (ADS)

    Weber, J. K. Richard; Krishnan, Shankar; Schiffman, Robert A.; Nordine, Paul C.

    Optical properties and spectral emissivities of liquid silicon, titanium, niobium, and zirconium were investigated by HeNe laser polarimetry at λ = 632.8 nm. The metals were of a high purity and, except for zirconium, clean. The more demanding environmental requirements for eliminating oxide or nitride phases from zirconium were not met. Containerless conditions were achieved by electromagnetic levitation and heating. CO2 laser beam heating was also used to extend the temperature range for stable levitation and to heat solid silicon to form the metallic liquid phase. Corrections to previously reported calorimetric measurements of the heat capacity of liquid niobium were derived from the measured temperature dependence of its spectral emissivity. Property measurements were obtained for supercooled liquid silicon and supercooling of liquid zirconium was accomplished. The purification of liquid metals and the extension of this work on liquids to the measurement of thermodynamic properties and phase equilibria are discussed.

  12. Optical properties of fly ash. Volume 1, Final report

    SciTech Connect

    Self, S.A.

    1994-12-01

    Research performed under this contract was divided into four tasks under the following headings: Task 1, Characterization of fly ash; Task 2, Measurements of the optical constants of slags; Task 3, Calculations of the radiant properties of fly ash dispersions; and Task 4, Measurements of the radiant properties of fly ash dispersions. Tasks 1 and 4 constituted the Ph.D. research topic of Sarbajit Ghosal, while Tasks 2 and 3 constituted the Ph.D. research topic of Jon Ebert. Together their doctoral dissertations give a complete account of the work performed. This final report, issued in two volumes consists of an executive summary of the whole program followed by the dissertation of Ghosal. Volume 1 contains the dissertation of Ghosal which covers the characterization of fly ash and the measurements of the radiant properties of fly ash dispersions. A list of publications and conference presentations resulting from the work is also included.

  13. Optical and thermodynamic property measurements of liquid metals and alloys

    NASA Technical Reports Server (NTRS)

    Weber, J. K. R.; Krishnan, Shankar; Schiffman, Robert A.; Nordine, Paul C.

    1991-01-01

    Optical properties and spectral emissivities of liquid silicon, titanium, niobium, and zirconium were investigated by HeNe laser polarimetry at 632.8 nm. The metals were of a high purity and, except for zirconium, clean. The more demanding environmental requirements for eliminating oxide or nitride phases from zirconium were not met. Containerless conditions were achieved by electromagnetic levitation and heating. CO2 laser beam heating was also used to extend the temperature range for stable levitation and to heat solid silicon to form the metallic liquid phase. Corrections to previously reported calorimetric measurements of the heat capacity of liquid niobium were derived from the measured temperature dependence of its spectral emissivity. Property measurements were obtained for supercooled liquid silicon and supercooling of liquid zirconium was accomplished. The purification of liquid metals and the extension of this work on liquids to the measurement of thermodynamic properties and phase equilibria are discussed.

  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. Investigation of Optical Properties of Zinc Oxide Photodetector

    NASA Astrophysics Data System (ADS)

    Chism, Tyler

    UV photodetection devices have many important applications for uses in biological detection, gas sensing, weaponry detection, fire detection, chemical analysis, and many others. Today's photodetectors often utilize semiconductors such as GaAs to achieve high responsivity and sensitivity. Zinc oxide, unlike many other semiconductors, is cheap, abundant, non-toxic, and easy to grow different morphologies at the micro and nano scale. With the proliferation of these devices also comes the impending need to further study optics and photonics in relation to phononics and plasmonics, and the general principles underlying the interaction of photons with solid state matter and, specifically, semiconductors. For this research a metal-semiconductor-metal UV photodetector has been fabricated by using a quartz substrate on top of which was deposited micropatterned gold in an interdigitated electrode design. On this, sparsely coated zinc oxide nano trees were hydrothermally grown. The UV photodetection device showed promise for detection applications, especially because zinc oxide is also very thermally stable, a quality which is highly sought after in today's UV photodetectors. Furthermore, the newly synthesized photodetector was used to investigate optical properties and how they respond to different stimuli. It was discovered that the photons transmitted through the sparsely coated zinc oxide nano trees decreased as the voltage across the device increased. This research is aimed at better understanding photons interaction with matter and also to open the door for new devices with tunable optical properties such as transmission.

  16. Biological glass fibers: Correlation between optical and structural properties

    PubMed Central

    Aizenberg, Joanna; Sundar, Vikram C.; Yablon, Andrew D.; Weaver, James C.; Chen, Gang

    2004-01-01

    Biological systems have, through the course of time, evolved unique solutions for complex optical problems. These solutions are often achieved through a sophisticated control of fine structural features. Here we present a detailed study of the optical properties of basalia spicules from the glass sponge Euplectella aspergillum and reconcile them with structural characteristics. We show these biosilica fibers to have a distinctive layered design with specific compositional variations in the glass/organic composite and a corresponding nonuniform refractive index profile with a high-index core and a low-index cladding. The spicules can function as single-mode, few-mode, or multimode fibers, with spines serving as illumination points along the spicule shaft. The presence of a lens-like structure at the end of the fiber increases its light-collecting efficiency. Although free-space coupling experiments emphasize the similarity of these spicules to commercial optical fibers, the absence of any birefringence, the presence of technologically inaccessible dopants in the fibers, and their improved mechanical properties highlight the advantages of the low-temperature synthesis used by biology to construct these remarkable structures. PMID:14993612

  17. Morphology and optical Properties of InAlN nanobumps.

    NASA Astrophysics Data System (ADS)

    Danylyuk, Yuri; Romanov, Dmitri; Auner, Gregory; Xu, Song

    2002-03-01

    Morphology and Optical Properties of InAlN nanobumps Yu. Danylyuk, D.A. Romanov, and G. Auner Wayne State University, Detroit, MI 48202 and S. Xu Molecular Inaging, Phoenix, AZ 85044 We have grown and thoroughly investigated InxAl1-xN films on a sapphire substrate with thin AlN buffer layer. The films were grown by plasma source molecular beam epitaxy (PSMBE) on c-plane sapphire (0001) substrates with thin (about 100 Å) AlN buffer layer. The value of indium concentration x varied from 0 to 1. High resolution X-ray diffraction scans (XRD) shows monocrystal quality and no face segregation at all values of x. The salient feature of the layers' morphology studied by the atomic force microscopy is the presence of a large number of nanobumps whose characteristic size is about the basic film thickness. We studied optical properties of these nanobump structures by UV/VIS optical absorption and reflection spectroscopy. Both absorption and reflection spectra demonstrate additional peaks that cannot be associated with known crystal defects and impurities. We suggest these additional peaks are due to electrons confined at the nanobump tips by strong electric field of piezoelectric origin.

  18. 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.

  19. Optical properties of mineral dust aerosol in the thermal infrared

    NASA Astrophysics Data System (ADS)

    Köhler, Claas H.

    2017-02-01

    The optical properties of mineral dust and biomass burning aerosol in the thermal infrared (TIR) are examined by means of Fourier Transform Infrared Spectrometer (FTIR) measurements and radiative transfer (RT) simulations. The measurements were conducted within the scope of the Saharan Mineral Dust Experiment 2 (SAMUM-2) at Praia (Cape Verde) in January and February 2008. The aerosol radiative effect in the TIR atmospheric window region 800-1200 cm-1 (8-12 µm) is discussed in two case studies. The first case study employs a combination of IASI measurements and RT simulations to investigate a lofted optically thin biomass burning layer with emphasis on its potential influence on sea surface temperature (SST) retrieval. The second case study uses ground based measurements to establish the importance of particle shape and refractive index for benchmark RT simulations of dust optical properties in the TIR domain. Our research confirms earlier studies suggesting that spheroidal model particles lead to a significantly improved agreement between RT simulations and measurements compared to spheres. However, room for improvement remains, as the uncertainty originating from the refractive index data for many aerosol constituents prohibits more conclusive results.

  20. Optical properties of single-walled carbon nanotube aerogels

    NASA Astrophysics Data System (ADS)

    Ostojic, Gordana

    2012-02-01

    A network of connected single-walled carbon nanotubes (SWNT) is created by a novel DNA-protein complex directed assembly. Due to a point-like nature of connectors, the SWNT aerogel represents a network of self-suspended nanotubes with a record ultra-low density of less 0.75 mg/cm^3. The assembly method and low density enables a direct comparison of optical properties of nanotubes in solvent and air to surfactant solubilized nanotubes. Optical properties of SWNT gels are investigated using optical absorption, photoluminescence and Raman spectroscopy. Gelled nanotubes in water and in the low population regime behave similar to solubilized nanotubes. In contrast, photoluminescence of SWNT aerogels exhibit nonlinear effects and a phonon-induced broadening. In addition, aerogels show a previously unobserved photoluminescence peak at 1.3 eV that corresponds to a phonon-assisted recombination of photoexcited charges. Raman spectra of carbon nanotube aerogels display narrow peaks due to the phonon decoupling of suspended SWNTs in air and a redistribution of G phonon population due to nonlinear effects.

  1. Control of the optical and crystalline properties of TiO{sub 2} in visible-light active TiO{sub 2}/TiN bi-layer thin-film stacks

    SciTech Connect

    Smith, Wilson; Fakhouri, Houssam; Pulpytel, Jerome; Arefi-Khonsari, Farzaneh

    2012-01-15

    Multi-layered thin films of TiO{sub 2} and TiN were created by rf reactive magnetron sputtering, and their crystalline, optical, and photoelectrochemical properties were measured. The overall composition of the films (TiO{sub 2}-to-TiN ratio) was kept constant with the height of each film. The number of layers and thickness of each layer was controlled to create bi-layer thin films that were composed of: 9 bi-layers, 18 bi-layers, 27 bi-layers, 36 bi-layers, and 45 bi-layers. XRD patterns were observed for each film after annealing to measure the grain size and composition of anatase and rutile as a function of temperature. It was found that the phase-transition temperature is able to be substantially controlled (between 550 deg. C and 850 deg. C) for the anatase to rutile transition by varying the number of layers/thickness of each layer. In addition, bi-layer stacking significantly affected the film's optical properties by lowering the bandgap into the visible-light region, and also showed up to three times the improvement in photoelectrochemical performance under uv and visible irradiation. Overall, bi-layer stacking of TiO{sub 2}/TiN films has shown a unique and highly desirable control over several important physical characteristics that can be beneficial for many applications, such as high-temperature sensors and optoelectronic devices.

  2. Optical properties of solids for solar energy conversion

    NASA Astrophysics Data System (ADS)

    Karlsson, B.

    The optical properties of transition metal carbides and nitrides were studied by reflectance measurements between 0.2 and 15 micrometers at room temperature and up to 500 C. An interpretation of the pronounced difference between the nitrides and carbides is made from a model in the electronic density of states distribution. The model is used to explain shifts in the optical constants when carbon or nitrogen-vacancies are introduced in the nitride. Calculations based on the optical constants suggest the nitrides as a new material for transparent heat-mirrors. The refractive index and band-edge of CuO, Cu sub 2O, Fe sub 2O sub 3, Cr sub 2O sub 3, i-C and a-Si have been measured and discussed within the framework of a new model for evaluating their potential use as the absorbing layer on a tandem-selective surface. A number of oxides on copper and steel were prepared by thermal and chemical methods and investigated for use as selectively absorbing surfaces. Thin films of noble and transition metals have been prepared and optically investigated for use as semi-transparent coatings on domestic windows.

  3. Optical properties of polymer microtips investigated with workshop tomographic system

    NASA Astrophysics Data System (ADS)

    Dudek, Michał; Kujawińska, Małgorzata; Makowski, Piotr; Jaroszewicz, Leszek R.; Parat, Vincent

    2016-04-01

    We present a novel methodology for optical fiber polymer microtip manufacturing ant testing, which supports the structure optimization process through utilization of an optical diffraction tomography system based on the lateral shear digital holographic microscope. The most important functional parameter of an optical fiber microtip is the output beam distribution in the far-field region, which depends on geometrical properties and refractive index distribution within the microtip. These factors, in turn, are determined by the optical power distribution of the actinic light and the exposition time during the photopolymerization process. In order to obtain a desired light field distribution we propose to govern the manufacturing process by a hybrid opto-numerical methodology, which constitutes a convenient feedback loop for modification of the fabrication parameters. A single cycle of the proposed scheme includes numerical modeling, tomographic measurements and modifications of fabrication process. We introduced the real values of three-dimensional refractive index distribution of microtips into the finite-difference time-domain (FDTD) simulations, which leaded to controlled modification of technology parameters and finally to improvement of a functional parameter of microtips.

  4. Magneto-optical activity of crude oil and its heavy fractions

    NASA Astrophysics Data System (ADS)

    Sokolov, A. E.; Edelman, I. S.; Zabluda, V. N.; Petrakovskaya, E. A.; Aleksandrovskii, A. S.; Shubin, A. A.; Trukhan, S. N.; Mart'yanov, O. N.

    2012-05-01

    We have experimentally studied optical and magneto-optical spectra of solutions of crude oils of different origin and their heavy fractions in the visible spectral range. Magnetic circular dichroism of oil in the wavelength range ˜550 nm has been revealed. We show that the shape of the spectra of this dichroism depends on the origin of crude oil, with the magnetic dichroism magnitude being proportional to the concentration of the oil in the solution. A comparison of the data of magneto-optical spectroscopy with electron paramagnetic resonance spectra and chemical composition of samples has allowed us to conclude that the observed magneto-optical activity is determined by the occurrence of VO2+ complexes in the oil samples. The revealed magneto-optical activity of crude oil can form the basis of a unique method of analysis of the composition and properties of oils of different origin and heavy fractions thereof.

  5. Determination of petrophysical properties of sedimentary rocks by optical methods

    NASA Astrophysics Data System (ADS)

    Korte, D.; Kaukler, D.; Fanetti, M.; Cabrera, H.; Daubront, E.; Franko, M.

    2017-04-01

    Petrophysical properties of rocks (thermal diffusivity and conductivity, porosity and density) as well as the correlation between them are of great importance for many geoscientific applications. The porosity of the reservoir rocks and their permeability are the most fundamental physical properties with respect to the storage and transmission of fluids, mainly oil characterization. Accurate knowledge of these parameters for any hydrocarbon reservoir is required for efficient development, management, and prediction of future performance of the oilfield. Thus, the porosity and permeability, as well as the chemical composition must be quantified as precisely as possible. This should be done along with the thermal properties, density, conductivity, diffusivity and effusivity that are intimately related with them. For this reason, photothermal Beam Deflection Spectrometry (BDS) technique for determination of materials' thermal properties together with other methods such as Energy Dispersive X-ray Scanning Electron Microscopy (SEM-EDX) for determining the chemical composition and sample structure, as well as optical microscopy to determine the particles size, were applied for characterization of sedimentary rocks. The rocks were obtained from the Andes south flank in the Venezuela's western basin. The validation of BDS applicability for determination of petrophysical properties of three sedimentary rocks of different texture and composition (all from Late Cretaceous associated with the Luna, Capacho and Colón-Mito Juan geological formations) was performed. The rocks' thermal properties were correlated to the microstructures and chemical composition of the examined samples.

  6. Effect of doping on structural and optical properties of ZnO nanoparticles: study of antibacterial properties

    NASA Astrophysics Data System (ADS)

    Maddahi, P.; Shahtahmasebi, N.; Kompany, A.; Mashreghi, M.; Safaee, S.; Roozban, F.

    2014-06-01

    Sol-gel method was successfully used for synthesis of ZnO nanoparticles doped with 10 % Mg or Cu. The structure, morphology and optical properties of the prepared nanoparticles were studied as a function of doping content. The synthesized ZnO:(Mg/Cu) samples were characterized using XRD, TEM, FTIR and UV-Vis spectroscopy techniques. The samples show hexagonal wurtzite structure, and the phase segregation takes place for Cu doping. Optical studies revealed that Mg doping increases the energy band gap while Cu incorporation results in decrease of the band gap. The antibacterial activities of the nanoparticles were tested against Escherichia coli (Gram negative bacteria) cultures. It was found that both pure and doped ZnO nanosuspensions show good antibacterial activity which increases with copper doping, and slightly decreases with adding Mg.

  7. 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.

  8. Structure and Optical Properties of Nanocrystalline Hafnium Oxide Thin Films (PostPrint)

    DTIC Science & Technology

    2014-09-01

    AFRL-RX-WP-JA-2014-0214 STRUCTURE AND OPTICAL PROPERTIES OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILMS (POSTPRINT) Neil R. Murphy AFRL...OPTICAL PROPERTIES OF NANOCRYSTALLINE HAFNIUM OXIDE THIN FILMS (POSTPRINT) 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...microstructure and optical constants is established. 15. SUBJECT TERMS hafnium oxide , sputter-deposition, structure, XRR, optical properties

  9. Magneto-optical Properties of Iron Oxide Nanoclusters

    NASA Astrophysics Data System (ADS)

    Kostopoulou, Athanasia; Tsiaoussis, Ioannis; Lappas, Alexandros

    2010-11-01

    We have developed a modified synthetic protocol for the growth of monodispersed, superparamagnetic, flower-like colloidal nanoclusters (CNCs) with 40-120 nm average diameters. Importantly, these are consisted of smaller iron oxide nanocrystals, also with adjustable size (12.2-7.7 nm). We show that their optical properties can be tuned by applying an external magnetic field. Spectrophotometric measurements under these conditions reveal a diffuse reflectance maximum in the visible range, which is related to the CNCs assembly in ordered structures. The increasing field strength leads to a blue shift in the spectral weight when the size of the CNCs is above a critical diameter. The size-dependent characteristics of the CNCs determine their magneto-optical behavior and their potential in photonic crystal based technologies.

  10. Magneto-electronic and optical properties of zigzag silicene nanoribbons

    NASA Astrophysics Data System (ADS)

    Shyu, Feng-Lin

    2017-03-01

    The tight-binding model including the spin-orbit coupling (SOC) is used to study electronic and optical properties of zigzag silicene nanoribbons (ZSiNRs) in magnetic and electric fields. The SOC affects the low-energy bands and induces new selection rules leading to richer optical spectra. Except an increase in bandgaps, perpendicular magnetic field further exhibits spin-polarized Landau levels, in which electron's probability density of band-edge states distributes like a standing-wave. Landau levels could enhance the DOS and increases absorption frequency and strength. Perpendicular electric field (Fz) increases bandgap and thus absorption frequency, but it does not change band symmetry, edge-states, and selection rules. Moreover, Fz enhances the split of spin-polarized states inducing more absorption peaks. Parallel electric field (Fx) leads to an overlap between conduction and valence bands and destroys band symmetry and Landau levels. Consequently, Fx exhibits new selection rules and enriches absorption spectra.

  11. Optical Properties of Human Cancer and Normal Cells

    NASA Astrophysics Data System (ADS)

    Sander, Christopher; Sun, Nan; Johnson, Jeffrey; Stack, Sharon; Tanner, Carol; Ruggiero, Steven

    2014-03-01

    We have investigated the optical properties of human oral and ovarian cancer and normal cells. Specifically, we have measured the absolute optical extinction for both whole cells and intra-cellular material in aqueous suspension. Measurements were conducted over a wavelength range of 250 to 1000nm with 1 nm resolution using Light Transmission Spectroscopy (LTS). This provides both the absolute extinction of materials under study and, with Mie inversion, the absolute number of particles of a given diameter as a function of diameter in the range of 1 to 3000 nm. Our preliminary studies show significant differences in both the extinction and particle size distributions associated with cancer versus normal cells, which appear to be correlated with differences in the particle size distribution in the range of ~ 50 to 250 nm.

  12. Optical properties and diffraction effects in opal photonic crystals.

    PubMed

    Balestreri, Alessandra; Andreani, Lucio Claudio; Agio, Mario

    2006-09-01

    Optical properties of fcc opals oriented along the [111] direction are calculated by means of a scattering-matrix approach based on approximating each sphere with cylindrical slices. The use of a plane-wave basis in each layer allows distinguishing zero-order reflection and transmission from higher-order (diffraction) spectra. Optical spectra at large values of the angle of incidence indicate the presence of diffraction effects and of polarization mixing along the LW orientation. Reflectance and transmittance in the high-energy region show a rich spectral dependence and compare reasonably well with recent experimental observations on polystyrene opals. Diffraction spectra as a function of the number of layers display an oscillatory behavior, pointing to the existence of a Pendellösung phenomenon, related to the exchange of energy between two propagating modes in the investigated three-dimensional photonic crystal. This phenomenon could be observed in transmittance experiments on high-quality opals with controlled thickness.

  13. Optical properties of a photopolymer film for digital holographic storage

    NASA Astrophysics Data System (ADS)

    Shin, Changwon; Kim, Junghoi; Kim, Nam; Lee, Hyojin; Kim, Eunkyoung

    2005-09-01

    Tir- and mono functional monomers were dispersed in a solution of polysulfone in organic solvent containing a photo initiator and other additives. New photopolymer film was prepared by dispersing acrylic monomer in a polysulfone matrix. The Polysulfone was adopted as a binder since it affords transparent thick films with low dimensional changes during holographic recording. Optical property of the photopolymer showed high diffraction efficiency (>90%) under an optimized optical condition at 532nm laser. The angular selectivity for angular multiplexing page oriented holographic memories (POHMs), the maximum diffraction efficiency of the material during holographic recording, the diffraction efficiency of the films as a function of an incident angle of two beams, exposure energy for saturation of the holographic material and application for holographic data storage will be discussed.

  14. 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.

  15. Effect of impurities on optical properties of pentaerythritol tetranitrate

    NASA Astrophysics Data System (ADS)

    Tsyshevskiy, Roman; Sharia, Onise; Kuklja, Maija M.

    2012-03-01

    Despite numerous efforts, the electronic nature of initiation of high explosives to detonation in general and mechanisms of their sensitivity to laser initiation in particular are far from being completely understood. Recent experiments show that Nd:YAG laser irradiation (at 1064nm) causes resonance explosive decomposition of PETN samples. In an attempt to shed some light on electronic excitations and to develop a rigorous interpretation to these experiments, the electronic structure and optical properties of PETN and a series of common impurities were studied. Band gaps (S0→S1) and optical singlet-triplet (S0→T1) transitions in both an ideal material and PETN containing various defects were simulated by means of state-of-the-art quantum-chemical computational techniques. It was shown that the presence of impurities in the PETN crystal causes significant narrowing of the band gap. The structure and role of molecular excitons in PETN are discussed.

  16. Thermoluminescence and optically stimulated luminescence properties of natural barytes.

    PubMed

    Kitis, G; Kiyak, N G; Polymeris, G S

    2010-12-01

    Heavy, baryte-loaded, concrete is commonly used as radiation shielding material around high energy particle accelerators. Concrete samples received from a shielding block located at CERN cite contain many crystalline inclusions which were identified as barytes by X-ray diffraction analysis and separated by their color, classified as white, orange and green. Basic properties of thermoluminescence (TL) and optically stimulated luminescence (OSL) signals of these barytes samples such as thermal and optical stability, repeatability and mainly the linearity of both their luminescence responses were investigated as a function of beta dose. These results are also discussed regarding detailed investigation on the correlation between TL and OSL signals and their implications for retrospective dosimetry.

  17. Microstructures and Optical Properties of Scales of Butterfly Wings

    NASA Astrophysics Data System (ADS)

    Tabata, Hiroshi; Kumazawa, Kinya; Funakawa, Masami; Takimoto, Jun-Ichi; Akimoto, Makio

    1996-03-01

    This paper describes the mechanism generating the beautiful wing colors of various male butterflies and the relationship between the wing material and the color appearance. The microstructure of the scales covering the upper surface of the wings was analyzed with the aid of a scanning electron microscope. The basic mechanism of color generation of structurally colored scales is determined for the first time in accordance with the theory of optical interference in thin film layers using a model of wing scales. Optical properties were found in relation to the three-dimensional spectral reflectance of the samples, and differences were observed between the brightness perceived in subjective evaluations and calculated values based on the reflective spectra of the structurally colored wings. The results of this study suggest that the microroughness of the upper wing surface may influence the perceived gloss of structurally colored wings.

  18. Optofluidic phantom mimicking optical properties of porcine livers

    SciTech Connect

    Long, Ruiqi; King, Travis; Akl, Tony; Ericson, Milton Nance; Wilson, Mark A.; Cote, Gerard L.; McShane, Michael J.

    2011-01-01

    One strategy for assessing efficacy of a liver transplant is to monitor perfusion and oxygenation after transplantation. An implantable optical sensor is being developed to overcome inadequacies of current monitoring approaches. To facilitate sensor design while minimizing animal use, a polydimethylsiloxane (PDMS)-based liver phantom was developed to mimic the optical properties of porcine liver in the 630-1000 nm wavelength range and the anatomical geometry of liver parenchyma. Using soft lithography to construct microfluidic channels in pigmented elastomer enabled the 2D approximation of hexagonal liver lobules with 15mm sinusoidal channels, which will allow perfusion with blood-mimicking fluids to facilitate the development of the liver perfusion and oxygenation monitoring system.

  19. Climatology of Aerosol Optical Properties in Southern Africa

    NASA Technical Reports Server (NTRS)

    Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

    2011-01-01

    A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with

  20. Studies on Optical and Electrical Properties of Hafnium Oxide Nanoparticles

    NASA Astrophysics Data System (ADS)

    Jayaraman, Venkatachalam; Sagadevan, Suresh; Sudhakar, Rajesh

    2017-03-01

    In this paper, the synthesis and physico-chemical properties of hafnium oxide nanoparticles (HfO2 NPs) are analyzed and reported. The synthesis was carried out by the precipitation route by using hafnium tetrachloride (HfCl4) as precursor material with potassium hydroxide (KOH) dissolved in Millipore water. In the precipitation technique, the chemical reaction is comparatively simple, low-cost and non-toxic compared to other synthetic methods. The synthesized HfO2 NPs were characterized by using powder x-ray diffraction (PXRD), ultraviolet-visible (UV-Vis) spectroscopy, Raman analysis, and high-resolution transmission electron microscopy (HRTEM). The monoclinic structure of the HfO2 NPs was resolved utilizing x-ray diffraction (XRD). The optical properties were studied from the UV-Vis absorption spectrum. The optical band gap of the HfO2NPs was observed to be 5.1 eV. The Raman spectrum shows the presence of HfO2 NPs. The HRTEM image showed that the HfO2 NPs were of spherical shape with an average particle size of around 28 nm. The energy-dispersive x-ray spectroscopy (EDS) spectrum obviously demonstrated the presence of HfO2 NPs. Analysis and studies on the dielectric properties of the HfO2 NPs such as the dielectric constant, the dielectric loss, and alternating current (AC) conductivity were carried out at varying frequencies and temperatures.

  1. Temperature-dependent optical properties of titanium nitride

    NASA Astrophysics Data System (ADS)

    Briggs, Justin A.; Naik, Gururaj V.; Zhao, Yang; Petach, Trevor A.; Sahasrabuddhe, Kunal; Goldhaber-Gordon, David; Melosh, Nicholas A.; Dionne, Jennifer A.

    2017-03-01

    The refractory metal titanium nitride is promising for high-temperature nanophotonic and plasmonic applications, but its optical properties have not been studied at temperatures exceeding 400 °C. Here, we perform in-situ high-temperature ellipsometry to quantify the permittivity of TiN films from room temperature to 1258 °C. We find that the material becomes more absorptive at higher temperatures but maintains its metallic character throughout visible and near infrared frequencies. X-ray diffraction, atomic force microscopy, and mass spectrometry confirm that TiN retains its bulk crystal quality and that thermal cycling increases the surface roughness, reduces the lattice constant, and reduces the carbon and oxygen contaminant concentrations. The changes in the optical properties of the material are highly reproducible upon repeated heating and cooling, and the room-temperature properties are fully recoverable after cooling. Using the measured high-temperature permittivity, we compute the emissivity, surface plasmon polariton propagation length, and two localized surface plasmon resonance figures of merit as functions of temperature. Our results indicate that titanium nitride is a viable plasmonic material throughout the full temperature range explored.

  2. Influence of oxygen on the optical properties of silver nanoparticles.

    PubMed

    Renteria-Tapia, V M; García-Macedo, J

    2008-12-01

    Silver nanoparticles in sol-gel silica films were obtained by annealing in hydrogen atmosphere and subsequently in oxygen atmosphere. Their properties were measured by UV-vis spectroscopy, transmission electron microscopy (TEM), high-resolution transmission electronic microscopy (HRTEM) and X-ray diffraction analysis. Samples prepared in a reducing atmosphere exhibited a surface plasmon resonance (SPR) located at 399 nm. Silver nanoparticles in an oxidizing atmosphere exhibited a red shift and damping of the SPR. These optical properties were explained due to the oxidation on the surface of silver nanoparticles to silver oxide yield in an oxygen atmosphere. Silver core-silver oxide shell nanostructures were observed by HRTEM. The average size of the metallic nanoparticles obtained by TEM was used for modeling the UV-vis spectra by using the Gans theory. Good fits to the spectra under an oxidizing atmosphere were obtained considering variable refractive indexes coming from the silver oxide shells surrounding to the nanoparticles. Therefore, the interaction between oxygen and the metallic surface of the nanoparticles, sensitively alters their optical properties.

  3. Retrieval of aerosol optical properties over land using PMAp

    NASA Astrophysics Data System (ADS)

    Grzegorski, Michael; Munro, Rosemary; Lang, Ruediger; Poli, Gabriele; Holdak, Andriy

    2015-04-01

    The retrieval of aerosol optical properties is an important task for industry and climate forecasting. An ideal instrument should include observations with moderate spectral and high spatial resolutions for a wide range of wavelengths (from the UV to the TIR), measurements of the polarization state at different wavelengths and measurements of the same scene for different observation geometries. As such an ideal instrument is currently unavailable the usage of different instruments on one satellite platform is an alternative choice. Since February 2014, the Polar Multi sensor Aerosol product (PMAp) is delivered as operational GOME product to our customers. The algorithms retrieve aerosol optical properties over ocean (AOD, volcanic ash, aerosol type) using a multi-sensor approach (GOME, AVHRR, IASI). The next releases of PMAp will provide an extended set of aerosol and cloud properties which include AOD over land and an improved volcanic ash retrieval combining AVHRR and IASI. This presentation gives an overview on the existing product and the prototypes in development. The major focus is the discussion of the AOD retrieval over land implemented in the upcoming PMAp2 release. In addition, the results of our current validation studies (e.g. comparisons to AERONET, other satellite platforms and model data) are shown.

  4. Optical Properties of GaN and ZnO

    NASA Astrophysics Data System (ADS)

    Song, J.-H.

    A brief review on the optical properties of wurtzite ZnO and GaN is presented in this chapter with an emphasis on comparison between the materials. The properties of free excitons and impurity-bound excitons, such as their energetic positions and binding energies, are summarized. The localization energy and the ionization energy of the dominant impurities obtained by emission spectroscopy are also presented. Typical aspects of emissions from donor—acceptor pairs, free-to-bound transition, and deep level recombination are discussed. Several experimental characteristics of the relevant heterostructures, InGaN/GaN and MgZnO/ZnO, are also given below. Basic optical methods characterizing the effects of internal electric fields and carrier-localization are summarized. The unique properties of polarization sensitive emissions from nonpolar films are presented. Based on the valence band structures, the polarization selection rules can be obtained in simpler forms. Some recent reports will also be introduced stating that the anisotropic strain in nonpolar films plays an important role in deciding the polarization selectivity. The results of Raman spectroscopy are summarized in the end, with the emphasis on deciding the residual strain and the carrier concentration.

  5. Relation between Oceanographic parameters and Optical properties in 5 coastal areas of Southern Italy

    NASA Astrophysics Data System (ADS)

    Campanelli, Alessandra; Braga, Federica; Betti, Mattia; Cavalli, Rosa Maria; Grilli, Federica; Pascucci, Simone; Marini, Mauro

    2014-05-01

    In the framework of the CLAM-PHYM (Coasts-and-Lake-Assessment-and-Monitoring-by-Prisma-Hyperspectral-Mission) project it was carried out an oceanographic cruise (27/08-13/09/2010) along the coasts of southern Italy in order to analyze the physical, biochemical and optical properties of some coastal areas. The sampling areas are: the Gulf of Taranto, the Policoro area, the Cetraro Bay, the Gulf of Augusta and the Gulf of Gela. CTD profiles and reflectance measurements of the sea surface and along the water column with portable field spectroradiometers were collected. Water samples were also collected for the analysis of nutrients, chlorophyll-a and CDOM. These optically active substances interact with solar radiation along the water column through absorption and scattering phenomena. The collected data were analyzed to identify the relationship between the bio-optical concentrations of optically-active-substances and the surface reflectance spectra measured in situ; this relation, if reversed, can be used to map the concentrations of optically-active-substances from hyperspectral-satellite-data. Results stress high biological activity in the Gulf of Taranto and in the Gulf of Gela showing the highest values of chlorophyll-a and aCDOM440. These areas are characterized by the presence of important industrial and port sites. The Gela's gulf, where we found the highest concentrations of chlorophyll a and CDOM, is also characterized by the runoff of the Salso river increasing the biological activity. The correlations found in the Gulf of Taranto between Kd, chlorophyll a and aCDOM440 indicate that the high concentrations of CDOM are primarily due to phytoplankton rather than from terrestrial source. The Gulf of Taranto shows the best site among those investigated where to identify bio-optical relationships between the concentrations of optically active substances and the surface reflectance spectra measured in situ. The preliminary results encourage the combined use of

  6. Directly observable optical properties of sprites in Central Europe

    NASA Astrophysics Data System (ADS)

    Bór, József

    2013-04-01

    Luminous optical emissions accompanying streamer-based natural electric breakdown processes initiating in the mesosphere are called sprites. 489 sprite events have been observed with a TV frame rate video system in Central Europe from Sopron (47.68N, 16.58E, 230 m MSL), Hungary between 2007 and 2009. On the basis of these observations, characteristic morphological properties of sprites, i.e. basic forms (e.g. column, carrot, angel, etc.) as well as common morphological features (e.g. tendrils, glows, puffs, beads, etc.), have been identified. Probable time sequences of streamer propagation directions were associated with each of the basic sprite forms. It is speculated that different sequences of streamer propagation directions can result in very similar final sprite shapes. The number and type variety of sprite elements appearing in an event as well as the total optical duration of an event was analyzed statistically. Jellyfish and dancing sprite events were considered as special subsets of sprite clusters. It was found that more than 90% of the recorded sprite elements appeared in clusters rather than alone and more than half of the clusters contained more than one basic sprite forms. The analysis showed that jellyfish sprites and clusters of column sprites featuring glows and tendrils do not tend to have optical lifetimes longer than 80 ms. Such very long optical lifetimes have not been observed in sprite clusters containing more than 25 elements of any type, either. In contrast to clusters containing sprite entities of only one form, sprite events showing more sprite forms seem to have extended optical durations more likely. The need for further investigation and for finding theoretical concepts to link these observations to electric conditions ambient for sprite formation is emphasized.

  7. Active learning in optics and photonics: Fraunhofer diffraction

    NASA Astrophysics Data System (ADS)

    Ghalila, H.; Ben Lakhdar, Z.; Lahmar, S.; Dhouaidi, Z.; Majdi, Y.

    2014-07-01

    "Active Learning in Optics and Photonics" (ALOP), funded by UNESCO within its Physics Program framework with the support of ICTP (Abdus Salam International Centre for Theoretical Physics) and SPIE (Society of Photo-Optical Instrumentation Engineers), aimed to helps and promotes a friendly and interactive method in teaching optics using simple and inexpensive equipment. Many workshops were organized since 2005 the year when Z. BenLakhdar, whom is part of the creators of ALOP, proposed this project to STO (Société Tunisienne d'Optique). These workshops address several issues in optics, covering geometrical optics, wave optics, optical communication and they are dedicated to both teachers and students. We focus this lecture on Fraunhofer diffraction emphasizing the facility to achieve this mechanism in classroom, using small laser and operating a slit in a sheet of paper. We accompany this demonstration using mobile phone and numerical modeling to assist in the analysis of the diffraction pattern figure.

  8. Efficient high repetition rate electro-optic Q-switched laser with an optically active langasite crystal

    PubMed Central

    Ma, Shihui; Yu, Haohai; Zhang, Huaijin; Han, Xuekun; Lu, Qingming; Ma, Changqin; Boughton, Robert I.; Wang, Jiyang

    2016-01-01

    With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc. PMID:27461819

  9. Optical properties of polymer/chalcogenide glass composite materials

    NASA Astrophysics Data System (ADS)

    Bormashenko, Edward; Pogreb, Roman; Sutovski, Semion

    2000-06-01

    The novel composite material based on middle density polyethylene on one hand and thermoplastic chalcogenide glass on other hand has been worked out. Both materials used in the research are highly transparent in the middle and far IR but refraction indexes of components differ dramatically. The basic materials, polymer and glass, have close viscosities at the temperature of polyethylene processing. This fact allowed use of the extrusion technique for homogenization purposes. We proved, that the controlled structure of a composite could be derived through the varying of technological parameters of the mixing process. Single- and twin screw extrusion processes obtained compositions, which contain up to 50% particles of chalcogenide glass, which were dispersed in the polymer matrix. The highly homogeneous compositions that contain perfect spherical glass particles of 1-2 micrometers in diameter dispersed into polymer matrix were obtained as well. Highly oriented structures involving chalcogenide glass fibers immersed in the polymer matrix were prepared under high stretch speeds as well. Such fiberlike structures exhibited pronounced polarization properties. We studied the optical properties of the composite and came to the conclusion that the controlled structure of the composite allows variation in its optical properties. It was established that it is possible to produce a composite that is opaque in the visible and near IR, and highly transparent in the 2-25-micrometers wave length band. Light scattering on oriented and disordered structures was studied by the IR spectro-goniometer. The novel composite which was developed by our group is intended for various IR-optics applications.

  10. Multilayer cloud detection and retrieval of cloud physical and optical properties from thermal infrared measurements

    NASA Astrophysics Data System (ADS)

    Iwabuchi, H.; Tokoro, Y.; Saito, M.; Putri, N. S.; Katagiri, S.; Sekiguchi, M.

    2015-12-01

    Recent studies using active remote sensing have revealed significant occurrence of multi-layer cloud. Detection of multi-layer cloud is important in passive remote sensing for quality assessment of cloud property retrieval and identification of uncertain retrievals. An algorithm using several thermal infrared (TIR) bands at 6-13.5 micron wavelengths to detect multilayer cloud and retrieve cloud physical and optical properties including cloud thermodynamic phase is developed. This significantly extends applicability of passive remote sensing and improves accuracy of cloud property retrieval. The method uses the split window bands as well as the carbon dioxide and water vapor absorption bands. The forward model uses the two-stream approximation to solve radiative transfer with gaseous absorption treated by the correlated-k distribution method. Brightness temperature errors are evaluated by model-to-model and model-to-measurement comparisons. Top pressure of lower cloud in multi-layer cloud column can be retrieved if the upper cloud optical thickness is less than 6. The optimal estimation method is used to simultaneously infer several cloud properties including water path, effective particle radius and cloud-top pressure. The method is applied to the Moderate Resolution Imaging Spectroradiometer (MODIS) using 10 TIR bands and compared to MODIS operational product and active remote sensing measurements, showing promising results. The TIR method well detects optically thin clouds and retrieve their properties with relatively high accuracy. Particularly, cloud-top of optically thin cloud is estimated well. Multi-layer cloud detection works usually, while the TIR measurements miss very thin cloud that appears near the tropopause. The algorithm will be applied to frequent observation data from a new Japanese geostationary satellite, Himawari-8.

  11. Annotated bibliography of ellipsometry and optical properties of solids

    NASA Astrophysics Data System (ADS)

    Christensen, T. M.

    1985-05-01

    This bibliography is a partial listing of articles on various aspects of ellipsometry and the optical properties of solids. Additional references can be found in the review articles listed in the first section. The comments about the articles represent the author's particular interest in the article and are by no means intended as complete summaries or even statements of the author's key point in the article. The lack of comments on many of the articles represents the author's inconsistent note-taking or the completeness of the author's title in describing the article. The papers are divided into 10 topical sections and are alphabetized within each section.

  12. Electronic and Optical Properties of Single Wall Carbon Nanotubes.

    PubMed

    Saito, R; Nugraha, A R T; Hasdeo, E H; Hung, N T; Izumida, W

    2017-02-01

    In this article, we overview our recent theoretical works on electronic and optical properties of carbon nanotubes by going from the background to the perspectives. Electronic Raman spectra of metallic carbon nanotubes give a new picture of Raman processes. Thermoelectricity of semiconducting nanotubes gives a general concept of the confinement effect on the thermoelectric power factor. Selective excitation of only a single phonon mode is proposed by the pulsed train technique of coherent phonon spectroscopy. Occurrence of both two and four fold degeneracy in the carbon nanotube quantum dot is explained by difference group velocities and the intra/inter valley scattering near the hexagonal corner of the Brillouin zone.

  13. Acoustical, morphological and optical properties of oral rehydration salts (ORS)

    NASA Astrophysics Data System (ADS)

    George, Preetha Mary; Jayakumar, S.; Divya, P.; Subhashree, N. S.; Ahmed, M. Anees

    2015-06-01

    Ultrasonic velocity, density and viscosity were measured in different concentrations of oral rehydration salts (ORS) at room temperature 303 k. From the experimental data other related thermodynamic parameters, viz adiabatic compressibility, intermolecular free length, acoustic impedence, relaxation time are calculated. The experimental data were discussed in the light of molecular interaction existing in the liquid mixtures. The results have been discussed in terms of solute-solvent interaction between the components. Structural characterization is important for development of new material. The morphology, structure and grain size of the samples are investigated by SEM. The optical properties of the sample have been studied using UV Visible spectroscopy.

  14. Optical properties of drug metabolites in latent fingermarks

    PubMed Central

    Shen, Yao; Ai, Qing

    2016-01-01

    Drug metabolites usually have structures of split-ring resonators (SRRs), which might lead to negative permittivity and permeability in electromagnetic field. As a result, in the UV-vis region, the latent fingermarks images of drug addicts and non drug users are inverse. The optical properties of latent fingermarks are quite different between drug addicts and non-drug users. This is a technic superiority for crime scene investigation to distinguish them. In this paper, we calculate the permittivity and permeability of drug metabolites using tight-binding model. The latent fingermarks of smokers and non-smokers are given as an example. PMID:26838730

  15. Acoustical, morphological and optical properties of oral rehydration salts (ORS)

    SciTech Connect

    George, Preetha Mary E-mail: jayakumars030@gmail.com; Divya, P.; Jayakumar, S. E-mail: jayakumars030@gmail.com; Subhashree, N. S.; Ahmed, M. Anees

    2015-06-24

    Ultrasonic velocity, density and viscosity were measured in different concentrations of oral rehydration salts (ORS) at room temperature 303 k. From the experimental data other related thermodynamic parameters, viz adiabatic compressibility, intermolecular free length, acoustic impedence, relaxation time are calculated. The experimental data were discussed in the light of molecular interaction existing in the liquid mixtures. The results have been discussed in terms of solute-solvent interaction between the components. Structural characterization is important for development of new material. The morphology, structure and grain size of the samples are investigated by SEM. The optical properties of the sample have been studied using UV Visible spectroscopy.

  16. Optical Properties in Non-equilibrium Phase Transitions

    SciTech Connect

    Ao, T; Ping, Y; Widmann, K; Price, D F; Lee, E; Tam, H; Springer, P T; Ng, A

    2006-01-05

    An open question about the dynamical behavior of materials is how phase transition occurs in highly non-equilibrium systems. One important class of study is the excitation of a solid by an ultrafast, intense laser. The preferential heating of electrons by the laser field gives rise to initial states dominated by hot electrons in a cold lattice. Using a femtosecond laser pump-probe approach, we have followed the temporal evolution of the optical properties of such a system. The results show interesting correlation to non-thermal melting and lattice disordering processes. They also reveal a liquid-plasma transition when the lattice energy density reaches a critical value.

  17. Optical properties of drug metabolites in latent fingermarks

    NASA Astrophysics Data System (ADS)

    Shen, Yao; Ai, Qing

    2016-02-01

    Drug metabolites usually have structures of split-ring resonators (SRRs), which might lead to negative permittivity and permeability in electromagnetic field. As a result, in the UV-vis region, the latent fingermarks images of drug addicts and non drug users are inverse. The optical properties of latent fingermarks are quite different between drug addicts and non-drug users. This is a technic superiority for crime scene investigation to distinguish them. In this paper, we calculate the permittivity and permeability of drug metabolites using tight-binding model. The latent fingermarks of smokers and non-smokers are given as an example.

  18. Optical and photocatalytic properties of TiO2 nanoplumes

    PubMed Central

    Scuderi, Viviana; Miritello, Maria; Nicotra, Giuseppe; Impellizzeri, Giuliana; Privitera, Vittorio

    2017-01-01

    Here we report the photocatalytic efficiency of hydrogenated TiO2 nanoplumes studied by measuring dye degradation in water. Nanoplumes were synthesized by peroxide etching of Ti films with different thicknesses. Structural characterization was carried out by scanning electron microscopy and transmission electron microscopy. We investigated in detail the optical properties of the synthesized material and related them to the efficiency of UV photodegradation of methylene blue dye. The obtained results show that TiO2 nanoplumes act as an effective antireflective layer increasing the UV photocatalytic yield of the film. PMID:28243556

  19. Optical properties of Er3 +-doped oxyfluoride glasses

    NASA Astrophysics Data System (ADS)

    Feng, Li; Wu, Yinsu

    2016-02-01

    Er3 +-singly doped and Er3 +/Yb3 +-codoped 50SiO2-(50 - x)BaF2-xZnF2(SBZx) oxyfluoride glasses are prepared and the optical properties of Er3 +-singly doped glasses are investigated by using the Judd-Ofelt theory. Bright green and red upconversion luminescence of Er3 +/Yb3 +-codoped glasses is obtained under 980 nm excitation. Furthermore, factors affecting this phenomenon such as glass composition, doping concentration of Er3 + and Yb3 + ions, and pump power are discussed in details.

  20. The effects of biodegradation and photodegradation on DOM optical properties

    NASA Astrophysics Data System (ADS)

    Hansen, A.; Moll, L.; Kraus, T. E.

    2012-12-01

    In aquatic environments, dissolved organic matter (DOM) plays a central role in ecosystem biogeochemistry and is important because it affects light penetration, food web dynamics, and pollutant transport. While knowing DOM concentration is important, it is also critical to characterize DOM composition because its chemical make-up determines how it reacts in the environment. Furthermore, the ability to determine the origin of DOM can help inform watershed management and predict future trends. The main factors affecting DOM composition include (1) original source material, (2) biodegradation, and (3) photodegradation. Many studies use optical properties (absorbance and fluorescence) to infer DOM composition and source, however there are few controlled laboratory studies using endmember sources. Here DOM optical properties of eight endmember sources-including soil, plant and algal leachates-from San Francisco Bay Delta wetlands were investigated following biological and photochemical degradation during a three month incubation period. The effects of photoexposure were examined at various points along the biodegradation curve to simulate photodegradation occurring as microorganisms consumed and transformed the bioavailable DOM. Samples were analyzed for dissolved organic carbon (DOC) concentration, absorbance, and fluorescence. While our results showed little change in DOC concentration in the soil leachate over the 3 month study period, DOC concentrations in plant and algal leachates decrease by over 70% within the first three days of biodegradation. As expected, biodegradation led to an increase in fluorescence index (FI), humic index (HIX), and specific absorbance (SUVA) values. Carbon-normalized fluorescence values increased for humic-like components associated with Peaks C and A, but decreased for more labile material, which is associated with Peak T. While the initial FI for plant and algal leachates was similar to soil, the FI for both of these sources increased

  1. Excitons and optical properties of alpha-quartz

    SciTech Connect

    Chang, Eric K.; Rohlfing, Michael; Louie, Steven G.

    2000-04-01

    We present an ab initio study of the optical properties of alpa-quartz. The absorption spectrum is calculated by solving the Bethe-Salpeter equation for the interacting electron-hole system and found to be in excellent agreement with the measured spectrum up to 10 eV above the absorption threshold. We find that excitonic effects are crucial in understanding the sharp features in the absorption spectrum in this energy range. The are also crucial in the ab initio computation of the static dielectric constant, significantly enhancing its value.

  2. Excitons and optical properties of alpha-quartz

    PubMed

    Chang; Rohlfing; Louie

    2000-09-18

    We present an ab initio study of the optical properties of alpha-quartz. The absorption spectrum is calculated by solving the Bethe-Salpeter equation for the interacting electron-hole system and found to be in excellent agreement with the measured spectrum up to 10 eV above the absorption threshold. We find that excitonic effects are crucial in understanding the sharp features in the absorption spectrum in this energy range. They are also crucial in the ab initio computation of the static dielectric constant, significantly enhancing its value.

  3. 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.

  4. Electronic Structure of Lanthanum Hydrides with Switchable Optical Properties

    SciTech Connect

    Ng, K.; Zhang, F.; Ng, K.; Zhang, F.; Anisimov, V.; Rice, T.; Anisimov, V.

    1997-02-01

    Recent dramatic changes in the optical properties of LaH{sub 2+x} and YH{sub 2+x} films discovered by Huiberts {ital et al.}[Nature (London) {bold 380}, 231 (1996)] suggest their electronic structure is described best by a local model. Electron correlation is important in H{sup -} centers and in explaining the transparent insulating behavior of LaH{sub 3}. The metal-insulator transition at x{approximately}0.8 takes place in a band of highly localized states centered on the H vacancies in the LaH{sub 3} structure. {copyright} {ital 1997} {ital The American Physical Society}

  5. Optical Properties of Silver Particulate Films on Modified Polymer Substrates

    NASA Astrophysics Data System (ADS)

    Gurumurthy, S. C.; Pattabi, Manjunatha; Sanjeeva, Ganesh

    2011-07-01

    Results of the investigations carried out on the optical properties of particulate films deposited on 8 MeV electron beam irradiated polystyrene (PS) and on blends of PS and Poly (4-vinyl pyridine) (P4VP) are reported. It is observed that absorption maxima shift towards higher wavelength for films deposited on irradiated polystyrene and on blends of PS and P4VP. These results indicate that morphology of the particulate films can be changed by tuning the metal polymer interaction in an inert polymer through electron beam irradiation or by blending it with an interacting polymer like P4VP.

  6. Clinical measurements of tissue optical properties in the esophagus

    NASA Astrophysics Data System (ADS)

    Bays, Roland; Wagnieres, Georges A.; Robert, D.; Mizeret, Jerome C.; Braichotte, Daniel; van den Bergh, Hubert; Savary, Jean-Francois; Monnier, Philippe

    1995-01-01

    A noninvasive probe has been devised and clinically used to perform in vivo measurements of the optical properties of the esophageal wall. The absorption coefficient and the effective scattering coefficient are determined from the observation of the spatial distribution of the diffuse reflectance at the tissue surface. Results, obtained at 514 and 630 nm, i.e. wavelengths of interest in photodynamic therapy with actual clinically used photosensitizers are summarized. An efficient and easily-built isotropic microprobe is also presented which is suitable to measure in situ the radiant energy fluence rate distribution in tissue.

  7. Optical method for determining the mechanical properties of a material

    DOEpatents

    Maris, H.J.; Stoner, R.J.

    1998-12-01

    Disclosed is a method for characterizing a sample, comprising the steps of: (a) acquiring data from the sample using at least one probe beam wavelength to measure, for times less than a few nanoseconds, a change in the reflectivity of the sample induced by a pump beam; (b) analyzing the data to determine at least one material property by comparing a background signal component of the data with data obtained for a similar delay time range from one or more samples prepared under conditions known to give rise to certain physical and chemical material properties; and (c) analyzing a component of the measured time dependent reflectivity caused by ultrasonic waves generated by the pump beam using the at least one determined material property. The first step of analyzing may include a step of interpolating between reference samples to obtain an intermediate set of material properties. The material properties may include sound velocity, density, and optical constants. In one embodiment, only a correlation is made with the background signal, and at least one of the structural phase, grain orientation, and stoichiometry is determined. 14 figs.

  8. Optical method for determining the mechanical properties of a material

    DOEpatents

    Maris, Humphrey J.; Stoner, Robert J.

    1998-01-01

    Disclosed is a method for characterizing a sample, comprising the steps of: (a) acquiring data from the sample using at least one probe beam wavelength to measure, for times less than a few nanoseconds, a change in the reflectivity of the sample induced by a pump beam; (b) analyzing the data to determine at least one material property by comparing a background signal component of the data with data obtained for a similar delay time range from one or more samples prepared under conditions known to give rise to certain physical and chemical material properties; and (c) analyzing a component of the measured time dependent reflectivity caused by ultrasonic waves generated by the pump beam using the at least one determined material property. The first step of analyzing may include a step of interpolating between reference samples to obtain an intermediate set of material properties. The material properties may include sound velocity, density, and optical constants. In one embodiment, only a correlation is made with the background signal, and at least one of the structural phase, grain orientation, and stoichiometry is determined.

  9. The transport properties of activated carbon fibers

    SciTech Connect

    di Vittorio, S.L. . Dept. of Materials Science and Engineering); Dresselhaus, M.S. . Dept. of Electrical Engineering and Computer Science Massachusetts Inst. of Tech., Cambridge, MA . Dept. of Physics); Endo, M. . Dept. of Electrical Engineering); Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons. 19 refs., 4 figs.

  10. The Transport Properties of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons.

  11. Optical Properties of Mixed Black Carbon, Inorganic and Secondary Organic Aerosols

    SciTech Connect

    Paulson, S E

    2012-05-30

    Summarizes the achievements of the project, which are divided into four areas: 1) Optical properties of secondary organic aerosols; 2) Development and of a polar nephelometer to measure aerosol optical properties and theoretical approaches to several optical analysis problems, 3) Studies on the accuracy of measurements of absorbing carbon by several methods, and 4) Environmental impacts of biodiesel.

  12. THE NATURE OF OPTICALLY DULL ACTIVE GALACTIC NUCLEI IN COSMOS

    SciTech Connect

    Trump, Jonathan R.; Impey, Chris D.; Gabor, Jared M.; Taniguchi, Yoshi; Nagao, Tohru; Shioya, Yasuhiro; Brusa, Marcella; Civano, Francesca; Elvis, Martin; Kelly, Brandon C.; Huchra, John P.; Jahnke, Knud; Koekemoer, Anton M.; Salvato, Mara; Capak, Peter; Scoville, Nick Z.; Kartaltepe, Jeyhan S.; Lanzuisi, Giorgio; McCarthy, Patrick J.; Maineri, Vincenzo

    2009-11-20

    We present infrared, optical, and X-ray data of 48 X-ray bright, optically dull active galactic nuclei (AGNs) in the COSMOS field. These objects exhibit the X-ray luminosity of an AGN but lack broad and narrow emission lines in their optical spectrum. We show that despite the lack of optical emission lines, most of these optically dull AGNs are not well described by a typical passive red galaxy spectrum: instead they exhibit weak but significant blue emission like an unobscured AGN. Photometric observations over several years additionally show significant variability in the blue emission of four optically dull AGNs. The nature of the blue and infrared emission suggest that the optically inactive appearance of these AGNs cannot be caused by obscuration intrinsic to the AGNs. Instead, up to approx70% of optically dull AGNs are diluted by their hosts, with bright or simply edge-on hosts lying preferentially within the spectroscopic aperture. The remaining approx30% of optically dull AGNs have anomalously high f{sub X} /f{sub O} ratios and are intrinsically weak, not obscured, in the optical. These optically dull AGNs are best described as a weakly accreting AGN with a truncated accretion disk from a radiatively inefficient accretion flow.

  13. The properties of optical lightning flashes and the clouds they illuminate

    NASA Astrophysics Data System (ADS)

    Peterson, Michael; Deierling, Wiebke; Liu, Chuntao; Mach, Douglas; Kalb, Christina

    2017-01-01

    Optical lightning sensors like the Optical Transient Detector and Lightning Imaging Sensor (LIS) measure total lightning across large swaths of the globe with high detection efficiency. With two upcoming missions that employ these sensors - LIS on the International Space Station and the Geostationary Lightning Mapper on the GOES-R satellite - there has been increased interest in what these measurements can reveal about lightning and thunderstorms in addition to total flash activity. Optical lightning imagers are capable of observing the characteristics of individual flashes that include their sizes, durations, and radiative energies. However, it is important to exercise caution when interpreting trends in optical flash measurements because they can be affected by the scene. This study uses coincident measurements from the Tropical Rainfall Measuring Mission (TRMM) satellite to examine the properties of LIS flashes and the surrounding cloud regions they illuminate. These combined measurements are used to assess to what extent optical flash characteristics can be used to make inferences about flash structure and energetics. Clouds illuminated by lightning over land and ocean regions that are otherwise similar based on TRMM measurements are identified. Even when LIS flashes occur in similar clouds and background radiances, oceanic flashes are still shown to be larger, brighter, longer lasting, more prone to horizontal propagation, and to contain more groups than their land-based counterparts. This suggests that the optical trends noted in literature are not entirely the result of radiative transfer effects but rather stem from physical differences in the flashes.

  14. Optical and field emission properties of Zinc Oxide nanostructures.

    PubMed

    Pan, Hui; Zhu, Yanwu; Ni, Zhenhua; Sun, Han; Poh, Cheekok; Lim, Sanhua; Sow, Chornghaur; Shen, Zexiang; Feng, Yuanping; Lin, Jianyi

    2005-10-01

    Zinc Oxide (ZnO) nano-pikes were produced by oxidative evaporation and condensation of Zn powders. The crystalline structure and optical properties of the ZnO nanostructures (ZnONs) greatly depend on the deposition position of the ZnONs. TEM and XRD indicated that the ZnONs close to the reactor center, ZnON-A, has better crystalline structure than the ZnONs away from the center, ZnON-B. ZnON-A showed the PL and Raman spectra characteristic of perfect ZnO crystals, whereas ZnON-B produced very strong green emission band at 500 nm in the photoluminescence (PL) spectrum and very strong Raman scattering peak at 560 cm(-1), both related to the oxygen deficiency due to insufficient oxidation of zinc vapor. ZnON-B exhibited better field emission properties with higher emission current density and lower turn-on field than ZnON-A.

  15. Synthesis and optical properties of silver nanoparticles and arrays.

    PubMed

    Evanoff, David D; Chumanov, George

    2005-07-11

    This Minireview systematically examines optical properties of silver nanoparticles as a function of size. Extinction, scattering, and absorption cross-sections and distance dependence of the local electromagnetic field, as well as the quadrupolar coupling of 2D assemblies of such particles are experimentally measured for a wide range of particle sizes. Such measurements were possible because of the development of a novel synthetic method for the size-controlled synthesis of chemically clean, highly crystalline silver nanoparticles of narrow size distribution. The method and its unique advantages are compared to other methods for synthesis of metal nanoparticles. Synthesis and properties of nanocomposite materials using these and other nanoparticles are also described. Important highlights in the history of the field of metal nanoparticles as well as an examination of the basic principles of plasmon resonances are included.

  16. DNA-linked nanoparticle materials: optical, electrical, and structural properties

    NASA Astrophysics Data System (ADS)

    Lazarides, A.; Park, S.-J.; Mirkin, C.; Storhoff, J.; Schatz, G.; Brazis, P.; Kannewurf, C.

    2001-03-01

    Novel bioinorganic materials composed of Au nanoparticles linked with DNA have been developed as colorimetric DNA sensors. In the presence of complimentary DNA, particles dressed with one of two oligonucleotide sequences are linked to form binary nanoparticle aggregates. Assemblies linked at 298K have plasmon frequency shifts that decrease with increasing linker length; annealing, however, eliminates the length dependence of the shift. Neither sedimentation rate measurements nor theoretical studies of the optical properties provide unambiguous explanation. However, small-angle X-ray scattering (SAXS) measurements indicate that separations between nanoparticles with or without annealing are proportional to the number of base pairs in the oligonucleotide linkers. DNA is thus shown to offer a means for tuning separations in nanoparticle materials. We have also investigated the electrical and structural properties of dry Au nanoparticle films linked by DNA. The assemblies are semiconducting, which suggests that DNA can be used as a chemically specific scaffolding material for assembly of conductive structures.

  17. Optical properties of quantum-dot-doped liquid scintillators

    PubMed Central

    Aberle, C.; Li, J.J.; Weiss, S.; Winslow, L.

    2014-01-01

    Semiconductor nanoparticles (quantum dots) were studied in the context of liquid scintillator development for upcoming neutrino experiments. The unique optical and chemical properties of quantum dots are particularly promising for the use in neutrinoless double-beta decay experiments. Liquid scintillators for large scale neutrino detectors have to meet specific requirements which are reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper, we report results on laboratory-scale measurements of the attenuation length and the fluorescence properties of three commercial quantum dot samples. The results include absorbance and emission stability measurements, improvement in transparency due to filtering of the quantum dot samples, precipitation tests to isolate the quantum dots from solution and energy transfer studies with quantum dots and the fluorophore PPO. PMID:25392711

  18. Statistical properties of light from optical parametric oscillators

    SciTech Connect

    Vyas, Reeta; Singh, Surendra

    2009-12-15

    Coherence properties of light beams generated by optical parametric oscillators (OPOs) are discussed in the region of threshold. Analytic expressions, that are valid throughout the threshold region, for experimentally measurable quantities such as the mean and variance of photon number fluctuations, squeezing of field quadratures, and photon counting distributions are derived. These expressions describe non-Gaussian fluctuations of light in the region of threshold and reproduce Gaussian fluctuations below and above threshold, thus providing a bridge between below and above threshold regimes of operation. They are used to study the transformation of fluctuation properties of light as the OPOs make a transition from below to above threshold. The results for the OPOs are compared to those for the single-mode and two-mode lasers and their similarities and differences are discussed.

  19. Synthesis, properties, and optical applications of low-dimensional perovskites.

    PubMed

    Zhang, Yupeng; Liu, Jingying; Wang, Ziyu; Xue, Yunzhou; Ou, Qingdong; Polavarapu, Lakshminarayana; Zheng, Jialu; Qi, Xiang; Bao, Qiaoliang

    2016-11-17

    Metal-halide perovskites have been hailed as remarkable materials for photovoltaic devices and, recently, their star has also been on the rise in optoelectronics and photonics. In particular, the optical properties of a metal-halide perovskite can be widely manipulated once its bulk structure has been reduced to a low-dimensional structure, allowing multiple functionalities of light generation, emission, transmission, and detection to be realized in one material. In this paper, we highlight the recent advances in the synthesis of low-dimensional metal-halide perovskites and their unique properties as well as their novel optoelectronic and photonic applications. It is anticipated that this review can serve as an overview and evaluation of state-of-the-art synthesis techniques as well as nanoscale optoelectronics and photonics based on low-dimensional perovskite nanocrystals.

  20. Optical and electronic properties of some semiconductors from energy gaps

    NASA Astrophysics Data System (ADS)

    Tripathy, Sunil K.; Pattanaik, Anup

    2016-03-01

    II-VI and III-V tetrahedral semiconductors have significant potential for novel optoelectronic applications. In the present work, some of the optical and electronic properties of these groups of semiconductors have been studied using a recently proposed empirical relationship for refractive index from energy gap. The calculated values of these properties are also compared with those calculated from some well known relationships. From an analysis of the calculated electronic polarisability of these tetrahedral binary semiconductors from different formulations, we have proposed an empirical relation for its calculation. The predicted values of electronic polarisability of these semiconductors agree fairly well with the known values over a wide range of energy gap. The proposed empirical relation has also been used to calculate the electronic polarisability of some ternary compounds.

  1. Optical and electrical properties of thin superconducting films

    NASA Technical Reports Server (NTRS)

    Covington, Billy C.; Jing, Feng Chen

    1990-01-01

    Infrared spectroscopic techniques can provide a vital probe of the superconducting energy gap which is one of the most fundamental physical properties of superconductors. Currently, the central questions regarding the optical properties of superconductors are how the energy gap can be measured by infrared techniques and at which frequency the gap exists. An effective infrared spectroscopic method to investigate the superconducting energy gap, Eg, was developed by using the Bomem DA 3.01 Fourier Transformation Spectrophotometer. The reflectivity of a superconducting thin film of YBaCuO deposited on SrTiO3 was measured. A shoulder was observed in the superconducting state reflectance R(sub S) at 480/cm. This gives a value of Eg/kT(sub c) = 7.83, where k is the Boltzmann constant and T(sub c) is the superconducting transition temperature, from which, it is suggested that YBaCuO is a very strong coupling superconductor.

  2. Optical properties of quantum-dot-doped liquid scintillators

    NASA Astrophysics Data System (ADS)

    Aberle, C.; Li, J. J.; Weiss, S.; Winslow, L.

    2013-10-01

    Semiconductor nanoparticles (quantum dots) were studied in the context of liquid scintillator development for upcoming neutrino experiments. The unique optical and chemical properties of quantum dots are particularly promising for the use in neutrinoless double-beta decay experiments. Liquid scintillators for large scale neutrino detectors have to meet specific requirements which are reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper, we report results on laboratory-scale measurements of the attenuation length and the fluorescence properties of three commercial quantum dot samples. The results include absorbance and emission stability measurements, improvement in transparency due to filtering of the quantum dot samples, precipitation tests to isolate the quantum dots from solution and energy transfer studies with quantum dots and the fluorophore PPO.

  3. Optical properties of quantum-dot-doped liquid scintillators.

    PubMed

    Aberle, C; Li, J J; Weiss, S; Winslow, L

    2013-10-14

    Semiconductor nanoparticles (quantum dots) were studied in the context of liquid scintillator development for upcoming neutrino experiments. The unique optical and chemical properties of quantum dots are particularly promising for the use in neutrinoless double-beta decay experiments. Liquid scintillators for large scale neutrino detectors have to meet specific requirements which are reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper, we report results on laboratory-scale measurements of the attenuation length and the fluorescence properties of three commercial quantum dot samples. The results include absorbance and emission stability measurements, improvement in transparency due to filtering of the quantum dot samples, precipitation tests to isolate the quantum dots from solution and energy transfer studies with quantum dots and the fluorophore PPO.

  4. Baseline Maritime Aerosol: Methodology to Derive the Optical Thickness and Scattering Properties

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Smirnov, Alexander; Holben, Brent N.; Dubovik, Oleg; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Satellite Measurements of the global distribution of aerosol and their effect on climate should be viewed in respect to a baseline aerosol. In this concept, concentration of fine mode aerosol particles is elevated above the baseline by man-made activities (smoke or urban pollution), while coarse mode by natural processes (e.g. dust or sea-spray). Using 1-3 years of measurements in 10 stations of the Aerosol Robotic network (ACRONET we develop a methodology and derive the optical thickness and properties of this baseline aerosol for the Pacific and Atlantic Oceans. Defined as the median for periods of stable optical thickness (standard deviation < 0.02) during 2-6 days, the median baseline aerosol optical thickness over the Pacific Ocean is 0.052 at 500 am with Angstrom exponent of 0.77, and 0.071 and 1.1 respectively, over the Atlantic Ocean.

  5. 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.

  6. Active Correction of Aberrations of Low-Quality Telescope Optics

    NASA Technical Reports Server (NTRS)

    Hemmati, Hamid; Chen, Yijian

    2007-01-01

    A system of active optics that includes a wavefront sensor and a deformable mirror has been demonstrated to be an effective means of partly correcting wavefront aberrations introduced by fixed optics (lenses and mirrors) in telescopes. It is envisioned that after further development, active optics would be used to reduce wavefront aberrations of about one wave or less in telescopes having aperture diameters of the order of meters or tens of meters. Although this remaining amount of aberration would be considered excessive in scientific applications in which diffraction-limited performance is required, it would be acceptable for free-space optical- communication applications at wavelengths of the order of 1 m. To prevent misunderstanding, it is important to state the following: The technological discipline of active optics, in which the primary or secondary mirror of a telescope is directly and dynamically tilted, distorted, and/or otherwise varied to reduce wavefront aberrations, has existed for decades. The term active optics does not necessarily mean the same thing as does adaptive optics, even though active optics and adaptive optics are related. The term "adaptive optics" is often used to refer to wavefront correction at speeds characterized by frequencies ranging up to between hundreds of hertz and several kilohertz high enough to enable mitigation of adverse effects of fluctuations in atmospheric refraction upon propagation of light beams. The term active optics usually appears in reference to wavefront correction at significantly lower speeds, characterized by times ranging from about 1 second to as long as minutes. Hence, the novelty of the present development lies, not in the basic concept of active or adaptive optics, but in the envisioned application of active optics in conjunction with a deformable mirror to achieve acceptably small wavefront errors in free-space optical communication systems that include multi-meter-diameter telescope mirrors that are

  7. Optical, microphysical and compositional properties of volcanic ash samples

    NASA Astrophysics Data System (ADS)

    Rocha Lima, A.; Martins, J.; Krotkov, N. A.; Tabacniks, M.; Artaxo, P.; Schumann, U.

    2012-12-01

    Volcanoes are one of the most important sources of aerosols in the atmosphere and the chemical and physical properties of these particles are of fundamental importance for better understanding of Earth's climate and weather patterns. One of the main parameters missing in current aerosol models is the complex refractive index of aerosol particles from the UV to the short wave infrared (SWIR) wavelengths. The main objective of this research was to perform a detailed characterization of important optical, microphysical and compositional properties of aerosol particles of the volcanic sample from Eyjafjallajökull (Iceland). Ash from this volcano was collected in the vicinity of the eruption in Iceland. The sample was brought to our laboratory and it was initially sieved to retain particles smaller than 45 um, de-agglomerated, re-suspended and carried out by a flow of air through the use of a Fluidized Bed Aerosol Generator (FBAG). This experimental setup allows us to separate particles into PM10, PM2.5, or PM1.0. Particles were collected on Nuclepore filters and analyzed by different techniques, such as Scanning Electron Microscopy (SEM) for determination of size distribution and shape, spectral reflectance for determination of the optical absorption properties as a function of the wavelength, mass concentration, material density, and X-Ray fluorescence for the elemental composition. The spectral imaginary part of refractive index (from 300 to 2500nm) was derived empirically from the measurements of the mass absorption coefficient, size distribution and density of the material. In this work we are going to show the inter comparison of the microphysical properties between Eyjafjallajökull Icelandic volcano and other volcanoes. Volcanic ash from Eyjafjallajökull shows strong absorption and consequently high imaginary refractive index for UV and visible wavelengths. Also, microphysical optical properties and compositional differences were observed between coarse and

  8. Growth and optical properties of embedded silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Colombo, Luciano

    2009-03-01

    The optoelectronic properties of nanostructured silicon (nc-Si) are governed by the interplay between the local chemical bonding features and the complex overall atomic structure. Interesting enough, a-Si has a larger optical absorption than the c-Si and, therefore, biphasic a-c silicon systems (i.e. nanocrystallites embedded into an amorphous matrix) are currently under investigation for next-generation photovoltaics. Biphasic systems undergo crystallization upon thermal annealing and, therefore, it is quite difficult to predict theoretically their finite-temperature optoelectronic properties. In this talk I will present our ongoing research on the growth and the optoelectronic properties of textured nanocrystalline silicon, here modeled as a distribution of cylindrical grains embedded into an amorphous matrix. As for the growth, I argue that by large-scale atomistic simulations it is possible to infer a continuum model for the crystallinity evolution upon thermal annealing.[1] In particular, at low crystallinity, it is proved that--consistently with the standard Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory--the a-c phase transformation is dominated by the isolated grain evolution; conversely, at later stages deviations from the KJMA theory are observed, mainly due to atomic-scale features. I also prove that such effects can be included by using an improved phenomenological version of the KJMA theory.[2] As for the finite-temperature optoelectronic properties, I present a divide-and-conquer computational procedure, based on a combination of empirical tight-binding and model-potential molecular dynamics. This procedure is applied to investigate local and average optoelectronic properties of very large nanostructured silicon systems and to predict the variation of the optical absorption upon crystallinity.[3] I show that the optical absorption of a nc-Si sample corresponds to a simple linear combination between c-Si and a-Si phases and it is not affected by electron

  9. Laser-ablated silicon nanoparticles: optical properties and perspectives in optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Kirillin, M. Yu; Sergeeva, E. A.; Agrba, P. D.; Krainov, A. D.; Ezhov, A. A.; Shuleiko, D. V.; Kashkarov, P. K.; Zabotnov, S. V.

    2015-07-01

    Due to their biocompatibility silicon nanoparticles have high potential in biomedical applications, especially in optical diagnostics. In this paper we analyze properties of the silicon nanoparticles formed via laser ablation in water and study the possibility of their application as contrasting agents in optical coherence tomography (OCT). The nanoparticles suspension was produced by picosecond laser irradiation of monocrystalline silicon wafers in water. According to transmission electron microcopy analysis the silicon nanoparticles in the obtained suspension vary in size from 2 to 200 nm while concentration of the particles is estimated as 1013cm-3. The optical properties of the suspension in the range from 400 to 1000 nm were studied by spectrophotometry measurements revealing a scattering coefficient of about 0.1 mm-1 and a scattering anisotropy factor in the range of 0.2-0.4. In OCT study a system with a central wavelength of 910 nm was employed. Potential of the silicon nanoparticles as a contrasting agent for OCT is studied in experiments with agarose gel phantoms. Topical application of the nanoparticles suspension allowed the obtaining of the contrast of structural features of phantom up to 14 dB in the OCT image.

  10. Aerosol optical properties over the midcontinental United States

    NASA Technical Reports Server (NTRS)

    Halthore, Rangasayi N.; Markham, Brian L.; Ferrare, Richard A.; Aro, Theo. O.

    1992-01-01

    Solar and sky radiation measurements were analyzed to obtain aerosol properties such as the optical thickness and the size distribution. The measurements were conducted as part of the First International Satellite Land Surface Climatology Project Field Experiment during the second intensive field campaign (IFC) from June 25 to July 14, 1987, and the fifth IFC from July 25 to August 12, 1989, on the Konza Prairie near Manhattan, Kansas. Correlations with climatological and meteorological parameters show that during the period of observations in 1987, two types of air masses dominated the area: an air mass with low optical thickness and low temperature air associated with a northerly breeze, commonly referred to as the continental air, and an air mass with a higher optical thickness and higher temperature air associated with a southerly wind which we call 'Gulf air'. The size distributions show a predominance of the larger size particles in 'Gulf air'. Because of the presence of two contrasting air masses, correlations with parameters such as relative humidity, specific humidity, pressure, temperature, and North Star sky radiance reveal some interesting aspects. In 1989, clear distinctions between continental and Gulf air cannot be made; the reason for this will be discussed.

  11. Effects of fiber manipulation methods on optical fiber properties

    NASA Astrophysics Data System (ADS)

    Reynolds, Robert O.; Bechter, Andrew; Crass, Jonathan

    2016-07-01

    Optical fibers are routinely used to couple high-resolution spectrographs to modern telescopes, enabling important advantages in areas such as the search for extrasolar planets using spectroscopic radial velocity measurements of candidate stars. Optical fibers partially scramble the input illumination, and this feature enables a fiber feed to provide more uniform illumination to the spectrograph optics, thereby reducing systematic errors in radial velocity measurements. However fibers suffer from focal ratio degradation (FRD), a spreading of the beam at the output of the fiber with respect to that at the fiber input, which results in losses in throughput and resolution. Modal noise, a measurement uncertainty caused by inherent fiber properties and evident as a varying spatial intensity at the fiber exit plane, reduces the signal to noise ratio in the data. Devices such as double scramblers are often used to improve scrambling, and better fiber end preparation can mitigate FRD. Many instruments agitate the fiber during an observation to reduce modal noise, and stretching the fiber during use has been shown to offer a greater reduction in that noise. But effects of agitation and stretching on fiber parameters such as total transmission and focal ratio degradation have not been adequately studied. In this paper we present measurements of transmission loss and focal ratio degradation for both agitated and stretched fibers.

  12. Optical properties of anodically degraded ZnO

    SciTech Connect

    Messerschmidt, Daniel Gnehr, Wolf-Michael; Eberhardt, Jens; Bratz, Kathrin; Romanus, Henry; Nicolay, Sylvain; Ballif, Christophe

    2014-03-07

    We discuss the optical properties of non-degraded and anodically degraded boron-doped zinc oxide (ZnO:B) deposited by low-pressure chemical vapour deposition on soda-lime glass. The optical model used to simulate the infrared reflectance in the wavelength range between 1.2 and 25 μm is based on the Maxwell-Garnett effective-medium theory. The model is sensitive to the conditions at the grain boundaries of the investigated polycrystalline ZnO:B films. We confirm that the presence of defect-rich grain boundaries, especially after degradation, causes a highly resistive ZnO:B film. Furthermore, indications of a degraded zinc oxide layer next to the ZnO:B/glass interface with different refractive index are found. We present evidence for the creation of oxygen vacancies, based on Raman investigations, which correlate with a shift of the optical absorption edge of the ZnO:B. Investigations with scanning and transmission electron microscopy show microvoids at the grain boundaries after anodic degradation. This indicates that the grain/grain interfaces are the principle location of defects after degradation.

  13. Design and property study of micro-slot optics

    NASA Astrophysics Data System (ADS)

    Wang, Yuting; Yi, Futing; Zhang, Tianchong; Liu, Jing; Wang, Bo; Zhou, Yue

    2017-03-01

    LIGA (Lithographie Galvanoformung Abformung) as a very useful technique for fabricating devices with micro-scale structures has been reported to make the micro-pore optics (MPO) for years. Light weight is one of the advantages of MPO, making it an alternative for X-ray focusing lenses used on space telescopes. However, researchers seldom considered using the MPO in visible light region. In this article, we designed a micro-slot optics (MSO) similar to MPO and fabricated it by X-ray LIGA technique. The MSO consists of 159 concentric hollow cylinders of nickel with the slot spacings ranging from 59 to 113 μm and the focusing property of MSO is studied by simulations and experiments. Both the simulation and experiment results indicate that MSO is a useful focusing element. The MSO has one focal point when the point source is on the principal optical axis with the size of the focal point equaling to the size of the point source.

  14. Laser optical disk position encoder with active heads

    NASA Technical Reports Server (NTRS)

    Osborne, Eric P.

    1991-01-01

    An angular position encoder that minimizes the effects of eccentricity and other misalignments between the disk and the read stations by employing heads with beam steering optics that actively track the disk in directions along the disk radius and normal to its surface is discussed. The device adapts features prevalent in optical disk technology to the application of angular position sensing.

  15. Nonlinear Optical Properties of Carotenoid and Chlorophyll Harmonophores

    NASA Astrophysics Data System (ADS)

    Tokarz, Danielle Barbara

    Information regarding the structure and function of living tissues and cells is instrumental to the advancement of cell biology and biophysics. Nonlinear optical microscopy can provide such information, but only certain biological structures generate nonlinear optical signals. Therefore, structural specificity can be achieved by introducing labels for nonlinear optical microscopy. Few studies exist in the literature about labels that facilitate harmonic generation, coined "harmonophores". This thesis consists of the first major investigation of harmonophores for third harmonic generation (THG) microscopy. Carotenoids and chlorophylls were investigated as potential harmonophores. Their nonlinear optical properties were studied by the THG ratio technique. In addition, a tunable refractometer was built in order to determine their second hyperpolarizability (gamma). At 830 nm excitation wavelength, carotenoids and chlorophylls were found to have large negative gamma values however, at 1028 nm, the sign of gamma reversed for carotenoids and remained negative for chlorophylls. Consequently, at 1028 nm wavelength, THG signal is canceled with mixtures of carotenoids and chlorophylls. Furthermore, when such molecules are covalently bonded as dyads or interact within photosynthetic pigment-protein complexes, it is found that additive effects with the gamma values still play a role, however, the overall gamma value is also influenced by the intra-pigment and inter-pigment interaction. The nonlinear optical properties of aggregates containing chlorophylls and carotenoids were the target of subsequent investigations. Carotenoid aggregates were imaged with polarization-dependent second harmonic generation and THG microscopy. Both techniques revealed crystallographic information pertaining to H and J aggregates and beta-carotene crystalline aggregates found in orange carrot. In order to demonstrate THG enhancement due to labeling, cultured cells were labeled with carotenoid

  16. Optical resolution of 5-alkyl-delta-valerolactones and synthesis of optically active 5-fluoroalkanols.

    PubMed

    Riswoko, Asep; Aoki, Yoshio; Hirose, Takuji; Nohira, Hiroyuki

    2002-01-01

    Optical resolutions of 5-alkyl-delta-valerolactones were carried out by derivatization to the diastereomeric amides, in which (R)-(+)-1-(1-naphthyl)ethylamine or (S)-(-)-1-phenylethylamine were used as resolving agents. Optically active 5-fluoroalkanols, useful intermediates for fluorinated ferroelectric liquid crystals, were derived from the resolved lactones in four steps without racemization.

  17. Tm3+, Yb3+ activated ANbO4 (A  =  Y, Gd, La) phosphors: a comparative study of optical properties (downshifting and upconversion emission) and laser induced heating effect

    NASA Astrophysics Data System (ADS)

    Dwivedi, Abhishek; Mishra, Kavita; Rai, S. B.

    2017-02-01

    A comparative study of optical properties and laser induced heating effects in Tm3+, Yb3+ doped YNbO4, GdNbO4 and LaNbO4 phosphors is presented in this work. The phosphors were structurally characterized by x-ray diffraction and scanning electron microscopy measurements. The vibrational structures of the phosphors were studied using FTIR measurements. The optical band gaps (E g), calculated from the Wood and Tauc plot, are found to be 3.78, 4.50 and 3.27 eV for YNbO4, GdNbO4 and LaNbO4, respectively. The luminescence property (downshifting (DS) and upconversion (UC)) was studied in the powder and the pellet forms of the phosphor samples. The DS emission of Tm3+ doped ANbO4 phosphors (λ ex  =  265 nm) consists of broad blue emission due to (NbO4)3- group overlapped with sharp peaks due to f-f transition of Tm3+ ion with most prominent emission one in the case of YNbO4 phosphor. The DS emission is comparatively more intense in the pellet form. The NIR excited UC emission spectra of Tm3+, Yb3+ co-doped ANbO4 phosphors contain intense blue and NIR emissions due to the Tm3+ ion. Contrary to the DS study, the best UC result is found for LaNbO4 phosphor in pellet form. Further, the laser induced heating effect in UC emission with respect to laser pump power and irradiation time has also been studied in Tm3+, and Yb3+ co-doped ANbO4 phosphors. It was found to be more effective in the case of the YNbO4 host where the heating effect is more prominent in the powder sample. We discuss the mechanisms involved in these observations in detail.

  18. Reconfigurable Optical Elements Based on Single and Coupled Microdisk Resonators with Quantum DOT Active Media

    DTIC Science & Technology

    2012-06-29

    successfully demonstrated (i) incorporation of CdSe QDs into polymer and dielectric host and realization of devices such as active waveguides , microdisk...14) These values are used as initial approximations for each of the two possible solutions. Results of numerical solution of Eq...between dielectric layers without having detrimental effect on the optical properties of the QDs. Characterization and Modeling By controlling

  19. Linkage between [|#11#|]morphology and optical properties of soot

    NASA Astrophysics Data System (ADS)

    Scarnato, B.; Richard, D. T.; vahidinia, S.; Hillyard, P.; Strawa, A. W.; Kirchstetter, T. W.; Preble, C.; Cuzzi, J. N.

    2011-12-01

    Black Carbon (BC) containing aerosols that are generally hydrophobic upon emission become increasingly mixed with other aerosol material through condensation and coagulation. In polluted urban air, BC becomes internally mixed with organics and sulfate on a time scale of about 12 hours. Recent studies have indicated that the photo-absorption by BC is enhanced as a consequence of the internal mixing of BC with these other aerosol materials. To estimate this absorption enhancement, we have undertaken laboratory studies involving the mixing of initially uncoated BC produced from the combustion of a methane diffusion flame with inorganic and organic compounds. Particle size distributions are used as a first indicator of coating. We use Scanning Electron Microscopy (SEM) to characterize the fractal and shape factors of the generated uncoated and coated BC (see Fig.1 and Fig.2). We create modeled aggregates with the same characteristics as those analyzed at the SEM and we initialize a radiation transfer model (ddscatt) to estimate optical properties of uncoated and coated BC. We quantify absorption enhancement due to coating as a function of aggregate morphology. We use Transmission Electron Microscopy (TEM) to determine the mixing state and to aid in distinguishing between absorption enhancement caused by fractal collapse and surface coating. This paper will show the relationships between soot morphology, coating and optical properties. SEM and TEM imaged of uncoated and coated soot a will be presented.

  20. Optical properties of dielectric plates coated with gapped graphene

    NASA Astrophysics Data System (ADS)

    Klimchitskaya, G. L.; Mostepanenko, V. M.

    2017-01-01

    The optical properties of dielectric plates coated with gapped graphene are investigated on the basis of first principles of quantum electrodynamics. The reflection coefficients and reflectivities of graphene-coated plates are expressed in terms of the polarization tensor of gapped graphene and the dielectric permittivity of plate material. Simple approximate expressions for the required combinations of components of the polarization tensor applicable in the wide frequency region, where the presence of a gap influences the optical properties, are found. Numerical computations of the reflectivities of graphene-coated SiO 2 plates are performed for different values of the mass-gap parameter at different temperatures. It is shown that with an increasing gap width the reflectivity of a graphene-coated plate at the normal incidence decreases by up to a factor of 8 depending on the values of frequency and mass-gap parameter. The angle dependences of reflectivities for both polarizations of the incident electromagnetic waves have been computed for Si and SiO 2 plates coated with gapped graphene. We demonstrate that the TM reflectivity has a minimum value at some angle of incidence depending on the mass-gap parameter, frequency and temperature, whereas the TE reflectivity depends on the angle of incidence monotonously. However, for the graphene coatings with a nonzero mass-gap parameter the reflected light cannot be fully polarized. Possible applications of the obtained results are discussed.