Science.gov

Sample records for optical property enhancement

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  2. Fabrication and optical enhancing properties of discrete supercrystals.

    PubMed

    Tebbe, Moritz; Lentz, Sarah; Guerrini, Luca; Fery, Andreas; Alvarez-Puebla, Ramon A; Pazos-Perez, Nicolas

    2016-07-01

    Discrete gold nanoparticle crystals with tunable size and morphology are fabricated via a fast and inexpensive template-assisted method. The highly precise hierarchical organization of the plasmonic building blocks yields superstructures with outstanding behaviour for surface-enhanced Raman scattering analysis. PMID:26898333

  3. Fabrication and optical enhancing properties of discrete supercrystals

    NASA Astrophysics Data System (ADS)

    Tebbe, Moritz; Lentz, Sarah; Guerrini, Luca; Fery, Andreas; Alvarez-Puebla, Ramon A.; Pazos-Perez, Nicolas

    2016-06-01

    Discrete gold nanoparticle crystals with tunable size and morphology are fabricated via a fast and inexpensive template-assisted method. The highly precise hierarchical organization of the plasmonic building blocks yields superstructures with outstanding behaviour for surface-enhanced Raman scattering analysis.Discrete gold nanoparticle crystals with tunable size and morphology are fabricated via a fast and inexpensive template-assisted method. The highly precise hierarchical organization of the plasmonic building blocks yields superstructures with outstanding behaviour for surface-enhanced Raman scattering analysis. Electronic supplementary information (ESI) available: UV-Vis spectra and TEM and SEM images of different particles and supercrystals. See DOI: 10.1039/c5nr09017b

  4. Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, Xiang; Pu, Shengli; Ji, Hongzhu; Yu, Guojun

    2012-05-01

    Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (Δ n) and figure of merit of optical properties ( Q = Δ n/α, where α is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of Q R exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field.

  5. Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals.

    PubMed

    Wang, Xiang; Pu, Shengli; Ji, Hongzhu; Yu, Guojun

    2012-01-01

    Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (Δn) and figure of merit of optical properties (Q = Δn/α, where α is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field. PMID:22587542

  6. Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals

    PubMed Central

    2012-01-01

    Ferronematic materials composed of 4-cyano-4′-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (Δn) and figure of merit of optical properties (Q = Δn/α, where α is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field. PMID:22587542

  7. Optical Property Enhancement and Durability Evaluation of Heat Receiver Aperture Shield Materials

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Jaworske, Donald A.; Smith, Daniela C.

    1998-01-01

    Under the Solar Dynamic Flight Demonstration (SDFD) program, NASA Lewis Research Center worked with AlliedSignal Aerospace, the heat receiver contractor, on the development, characterization and durability testing of refractory metals to obtain appropriate optical and thermal properties for the SDFD heat receiver aperture shield. Molybdenum and tungsten foils were grit-blasted using silicon carbide or alumina grit under various grit-blasting conditions for optical property enhancement. Black rhenium coated tungsten foil was also evaluated. Tungsten, black rhenium-coated tungsten, and grit-blasted tungsten screens of various mesh sizes were placed over the pristine and grit-blasted foils for optical property characterization. Grit-blasting was found to be effective in decreasing the specular reflectance and the absorptance/emittance ratio of the refractory foils. The placement of a screen further enhanced these optical properties, with a grit-blasted screen over a grit-blasted foil producing the best results. Based on the optical property enhancement results, samples were tested for atomic oxygen and vacuum heat treatment durability. Grit-blasted (Al2O3 grit) 2 mil tungsten foil was chosen for the exterior layer of the SDFD heat receiver aperture shield. A 0.007 in. wire diameter, 20 x 20 mesh tungsten screen was chosen to cover the tungsten foil. Based on these test results, a heat receiver aperture shield test unit has been built with the screen covered grit-blast tungsten foil exterior layers. The aperture shield was tested and verified the thermal and structural durability of the outer foil layers during an off-pointing period.

  8. Long term measurements of the estimated hygroscopic enhancement of aerosol optical properties

    NASA Astrophysics Data System (ADS)

    Hervo, Maxime; Sellegri, Karine; Pichon, Jean Marc; Roger, Jean Claude; Laj, Paolo

    2015-04-01

    Water vapour has a major impact on aerosol optical properties, thus on the Radiative Forcing for aerosol-radiation interaction (RFari). However there is few studies measuring this impact over a large period. Optical properties of aerosols were measured at the GAW Puy de Dôme station (1465m) over a seven year period (2006-2012). The impact of hygroscopicity on aerosol optical properties was calculated over a two year period (2010-2011). The analysis of the spatial and temporal variability of the dry optical properties showed that while no long term trend was found, a clear seasonal and diurnal variation was observed on the extensive parameters (scattering, absorption). Scattering and absorption coefficients were highest during the warm season and daytime, in concordance with the seasonality and diurnal variation of the planetary boundary layer height reaching the site. Intensive parameters (single scattering albedo, asymmetry factor, refractive index) did not show such a strong diurnal variability, but still indicated different values depending on the season. Both extensive and intensive optical parameters were sensitive to the air mass origin. A strong impact of hygroscopicity on aerosol optical properties was calculated, mainly on aerosol scattering, with a dependence on the aerosol type and the season. At 90% humidity, the scattering factor enhancement (fsca) was more than 4.4 for oceanic aerosol that have mixed with a pollution plume. Consequently, the aerosol radiative forcing was estimated to be 2.8 times higher at RH= 90% and 1.75 times higher at ambient RH when hygroscopic growth of the aerosol was considered. The hygroscopicity enhancement factor of the scattering coefficient was parameterized as a function of humidity and air mass type. To our knowledge, these results are one of the first presenting the impact of water vapour on the aerosol optical properties for a long period, and the first for a site at the border between the planetary boundary layer

  9. Host-Guest Carbon Dots for Enhanced Optical Properties and Beyond

    PubMed Central

    Sun, Ya-Ping; Wang, Ping; Lu, Zhuomin; Yang, Fan; Meziani, Mohammed J.; LeCroy, Gregory E.; Liu, Yun; Qian, Haijun

    2015-01-01

    Carbon dots, generally small carbon nanoparticles with various forms of surface passivation, have achieved the performance level of semiconductor quantum dots in the green spectral region, but their absorption and fluorescence in red/near-IR are relatively weaker. Conceptually similar to endofullerenes, host-guest carbon dots were designed and prepared with red/near-IR dyes encapsulated as guest in the carbon nanoparticle core. Beyond the desired enhancement in optical properties, the host-guest configuration may significantly broaden the field of carbon dots. PMID:26196598

  10. Plasmonic Enhancement of Optical Properties by Isolated and Coupled Metal Nanoparticles

    NASA Astrophysics Data System (ADS)

    Sun, Greg; Khurgin, Jacob B.

    2012-12-01

    In this chapter we present a simple and comprehensive explanation of the mechanisms that can so dramatically modify the optical properties of atoms, molecules, or other quantum-size objects placed in the vicinity of metal nanoparticles. We develop a simple model that describes surface plasmon modes supported by the metal nanoparticles and describes them using just three key parameters -- effective volume, Q-factor, and radiative decay rate. We subsequently apply this model to the tasks of estimating the enhancement of optical radiation, electroluminescence, and photoluminescence absorbed or emitted by the optically active objects in the presence of an isolated single nanoparticle. Using the example of gold nanospheres embedded in GaN dielectric, we show that enhancement for each case depends strongly on the nanoparticle size enabling optimization for each combination of absorption cross section, original radiative efficiency, and separation between the object and metal sphere. We then expand the model for single metal nanoparticles to coupled metal nanostructures. We show that complex structures can be treated as coupled multipole modes with highest enhancements obtained due to the superposition of these modes mainly in small particles. This model allows for optimization of the structures for the largest possible field enhancements, which depends on the quality factor Q of the metal and can be as high as Q2 for two spherical particles. The "hot spot" can occur either in the nano-gaps between the particles or near the smaller particles. We trace the optimal field enhancement mechanism to the fact that the extended dipole modes of larger particles act as the efficient antennas while the modes in the gaps or near the smaller particles act as the compact sub-wavelength cavities. The physically-transparent, comprehensive analytical approach developed in this chapter not only offers a quick route for optimization but also can be conveniently extended to incorporate large

  11. Enhanced optical and electrical properties of PEDOT:PSS/Gold nanocomposite system

    NASA Astrophysics Data System (ADS)

    Thappily, Praveen; Shiju, K.

    2014-10-01

    In this paper, we report modification of the electrical and optical properties of widely used transparent conducting polymer, PEDOT:PSS by the incorporation of gold nanoparticles (Au NPs) synthesized using aloe barbadensis leaf extract as reducing agent. The variation of workfunction of the PEDOT:PSS with Au Nanoparticles content is investigated and it has been seen that the work function of PEDOT:PSS can be tuned by incorporating nanoparticles. Further the optical absorption of the composite is found to be increasing considerably in the visible region. It has been demonstrated that there exists an optimum weight percentage of Au NPs for the composite formation with highest workfunction and enhanced light absorption in the visible region than pristine PEDOT:PSS.

  12. Polyaniline/carbon nanotube/CdS quantum dot composites with enhanced optical and electrical properties

    NASA Astrophysics Data System (ADS)

    Goswami, Mrinmoy; Ghosh, Ranajit; Maruyama, Takahiro; Meikap, Ajit Kumar

    2016-02-01

    A new kind of polyaniline/carbon nanotube/CdS quantum dot composites have been developed via in-situ polymerization of aniline monomer in the presence of dispersed CdS quantum dots (size: 2.7-4.8 nm) and multi-walled carbon nanotubes (CNT), which exhibits enhanced optical and electrical properties. The existences of 1st order, 2nd order, and 3rd order longitudinal optical phonon modes, strongly indicate the high quality of synthesized CdS quantum dots. The occurrence of red shift of free exciton energy in photoluminescence is due to size dependent quantum confinement effect of CdS. The conductivity of the composites (for example PANI/CNT/CdS (2 wt.% CdS)) is increased by about 7 of magnitude compared to that of pure PANI indicating a charge transfer between CNT and polymer via CdS quantum dots. This advanced material has a great potential for high-performance of electro-optical applications.

  13. Evidence for enhanced optical properties through plasmon resonance energy transfer in silver silica nanocomposites

    NASA Astrophysics Data System (ADS)

    Mol, Beena; Joy, Lija K.; Thomas, Hysen; Thomas, Vinoy; Joseph, Cyriac; Narayanan, T. N.; Al-Harthi, Salim; Unnikrishnan, N. V.; Anantharaman, M. R.

    2016-02-01

    Silver nanoparticles were dispersed in the pores of monolithic mesoporous silica prepared by a modified sol-gel method. Structural and microstructural analyses were carried out by Fourier transform infrared spectroscopy and transmission electron microscopy. X-ray photoelectron spectroscopy was employed to determine the chemical states of silver in the silica matrix. Optical absorption studies show the evolution absorption band around 300 nm for silver (Ag) in a silica matrix and it was found to be redshifted to 422 nm on annealing. Photoluminescence studies indicate the presence of various luminescent emitting centers corresponding to silver ions and silver dimers in the SiO2 matrix. The enhancement of absorption and photoluminescence properties is attributed to plasmon resonance energy transfer from Ag nanoparticles to luminescent species in the matrix.

  14. Optical properties and electric field enhancement in cholesteric liquid crystal containing different periodicities

    NASA Astrophysics Data System (ADS)

    Ozaki, Ryotaro; Matsuhisa, Yuko; Yoshida, Hiroyuki; Yoshino, Katsumi; Ozaki, Masanori

    2006-07-01

    We study a defect mode in a one-dimensional photonic band gap of a cholesteric liquid crystal (CLC) consisting of two helicoidal periodicities. The optical properties of this CLC are analyzed using 4×4 transfer matrix and finite difference time domain (FDTD) methods. In calculated transmission spectra of this CLC, one of the defect modes always appears at the band edge wavelength of the inner CLC having a different helix to that of two sides of CLCs. Furthermore, the electric field analysis of this CLC has also been demonstrated by the FDTD method. At the defect mode wavelength, the electric field enhancement is found to be significant larger than a normal CLC.

  15. Evidence for enhanced optical properties through plasmon resonance energy transfer in silver silica nanocomposites.

    PubMed

    Mol, Beena; Joy, Lija K; Thomas, Hysen; Thomas, Vinoy; Joseph, Cyriac; Narayanan, T N; Al-Harthi, Salim; Unnikrishnan, N V; Anantharaman, M R

    2016-02-26

    Silver nanoparticles were dispersed in the pores of monolithic mesoporous silica prepared by a modified sol-gel method. Structural and microstructural analyses were carried out by Fourier transform infrared spectroscopy and transmission electron microscopy. X-ray photoelectron spectroscopy was employed to determine the chemical states of silver in the silica matrix. Optical absorption studies show the evolution absorption band around 300 nm for silver (Ag) in a silica matrix and it was found to be redshifted to 422 nm on annealing. Photoluminescence studies indicate the presence of various luminescent emitting centers corresponding to silver ions and silver dimers in the SiO2 matrix. The enhancement of absorption and photoluminescence properties is attributed to plasmon resonance energy transfer from Ag nanoparticles to luminescent species in the matrix. PMID:26808999

  16. Facile synthesis and enhanced nonlinear optical properties of porphyrin-functionalized multi-walled carbon nanotubes.

    PubMed

    Wang, Aijian; Fang, Yu; Long, Lingliang; Song, Yinglin; Yu, Wang; Zhao, Wei; Cifuentes, Marie P; Humphrey, Mark G; Zhang, Chi

    2013-10-11

    Two multi-walled carbon nanotube (MWCNT)-based nanohybrids, MWCNT-ZnTPP and MWCNT-TPP (TPP=5-[4-{2-(4-formylphenoxy)- ethyloxy}phenyl]-10,15,20-triphenylporphyrin, ZnTPP=5-[4-{(4-formylphenyl)ethynyl}phenyl]-10,15,20-triphenylporphinatozinc(II)), were prepared directly from pristine MWCNTs through 1,3-dipolar cycloaddition reactions. Covalent attachment of the porphyrins to the surfaces of the MWCNTs was confirmed by Fourier transform infrared spectroscopy, ultraviolet/visible absorption, fluorescence, Raman, and X-ray photoelectron spectroscopy, elemental analysis, transmission electron microscopy, and thermogravimetric analysis. Attachment of the porphyrin moieties to the surface of the MWCNTs significantly improves the solubility and ease of processing of these MWCNT-porphyrin composite materials. Z-scan studies reveal that these MWCNT-porphyrin nanohybrids exhibit enhanced nonlinear optical properties under both nanosecond and picosecond laser pulses at λ=532 nm in comparison with free MWCNTs and the free porphyrin chromophores, whereas superior optical limiting performance was displayed by MWCNT-porphyrin composite materials rather than MWCNTs/ZnTPP and MWCNTs/TPP blends, which is consistent with a remarkable accumulation effect as a result of the covalent linkage between the porphyrin and the MWCNTs. PMID:24038312

  17. Enhanced optical properties due to indium incorporation in zinc oxide nanowires

    NASA Astrophysics Data System (ADS)

    Farid, S.; Mukherjee, S.; Sarkar, K.; Mazouchi, M.; Stroscio, M. A.; Dutta, M.

    2016-01-01

    Indium-doped zinc oxide nanowires grown by vapor-liquid-solid technique with 1.6 at. % indium content show intense room temperature photoluminescence (PL) that is red shifted to 20 meV from band edge. We report on a combination of nanowires and nanobelts-like structures with enhanced optical properties after indium doping. The near band edge emission shift gives an estimate for the carrier density as high as 5.5 × 1019 cm-3 for doped nanowires according to Mott's critical density theory. Quenching of the visible green peak is seen for doped nanostructures indicating lesser oxygen vacancies and improved quality. PL and transmission electron microscopy measurements confirm indium doping into the ZnO lattice, whereas temperature dependent PL data give an estimation of the donor and acceptor binding energies that agrees well with indium doped nanowires. This provides a non-destructive technique to estimate doping for 1D structures as compared to the traditional FET approach. Furthermore, these indium doped nanowires can be a potential candidate for transparent conducting oxides applications and spintronic devices with controlled growth mechanism.

  18. Enhancement of nonlinear optical (NLO) properties of indigo through modification of auxiliary donor, donor and acceptor

    NASA Astrophysics Data System (ADS)

    Mahmood, Asif; Abdullah, Muhammad Imran; Khan, Salah Ud-Din

    2015-03-01

    In this study, indigo based dyes with high non-linear optical response have been investigated. Density functional theory (DFT) was used to study non-linear optical properties of indigo and newly designed dyes (IM-Dye-0, IM-Dye-1, IM-Dye-2 and IM-Dye-3). The time dependant density functional theory (TDDFT) was used to calculate the excitation energies. The HOMO-LUMO energy gaps of newly designed dyes were smaller as compare with indigo dye. Absorption maxima of newly designed dyes strongly red shifted as compare with indigo dye. High non-linear optical (NLO) response of newly designed dyes revealed that these materials would be excellent for NLO applications. This theoretical approach of designing will pave the way for experimentalists to synthesize high response NLO compound.

  19. Enhanced microscopic nonlinear optical properties of novel Y-type chromophores with dual electron donor groups

    NASA Astrophysics Data System (ADS)

    Tang, Xiang; Pan, Lin; Jia, Kun; Tang, Xianzhong

    2016-03-01

    In this Letter, novel Y-type chromophores with dual electron donor groups, containing either styryl or azobenzene based π-conjugated bridge structures, were synthesized and their chemical structures, molecular configuration, microscopic optical properties as well as thermal properties were systematically characterized. The experimental results indicated that eight times increasing of second-order molecular hyperpolarizability as well as 50-100 nm blue shift of maximum absorption band for azobenzene based chromophore were observed by introducing Y-type dual electron donor groups, which was derived from the highly efficient 'total charge transfer' in this kind of chromophore as confirmed by the density functional theory calculation.

  20. Zn1-xCoxO nanoparticles: Synthesis and study of enhanced optical and structural properties

    NASA Astrophysics Data System (ADS)

    Ahad, Abdul; Majid, Suhail; Rahman, F.

    2016-05-01

    We have synthesized the Zn1-xCoxO (x= 0, 0.01, 0.03 and 0.05) using Sol-gel method. The structural properties were characterized using X-ray diffraction. Optical properties were characterized using UV-VIS and FT-IR spectroscopy. The lattice parameters were refined using Reitveld refinement which also reveals that all the peaks in XRD patterns were indexed in the wurtzite type hexagonal structure with space group P 63 mc. The FT-IR spectra confirmed the presence of functional groups and chemical bonding. The band gap of each sample was calculated by adopting Kubelka-Munk transformed reflectance spectra and effect of doping on band gap is also studied.

  1. Optical limiting by chemically enhanced bacteriorhodopsin films

    NASA Astrophysics Data System (ADS)

    Song, Q. Wang; Zhang, Chungping; Gross, Richard; Birge, Robert

    1993-05-01

    Measurements of effective nonlinearity of a chemically enhanced bacteriorhodopsin film are presented, using 2-scan method. Optical limiting properties and the film's nonlinear transmission properties of the film are also studied.

  2. Enhancing micro-electromechanical and tuning optical properties in Nd-doped BIT thin film

    NASA Astrophysics Data System (ADS)

    Zhang, Yunjie; Chen, Changle; Wang, Jing; Luo, Bingcheng; Duan, Mengmeng; Jin, Kexin

    2016-03-01

    Bi4Ti3O12 (BIT) and Bi3.25Nd0.75Ti3O12 (BNT) thin films were deposited on Pt/Ti/SiO2/Si (100) substrates using pulsed laser deposition. The surface morphologies, ferroelectric domain structures and polarization switching were investigated by atomic force microscopy (AFM) and piezoelectric force microscopy (PFM). The phase and amplitude images of PFM show that the BIT and BNT thin films have clear domain structures. Comparison of the surface morphologies and domain structures indicates that the grain boundaries limit the shape of domain and affect the domain structure. The micro-electromechanical performance was characterized by the effective piezoelectric coefficient d33,f of the thin films. The result shows that the maximum effective d33,f value (100 pm/V) of BNT thin film is larger than that of BIT thin film (30 pm/V). This can be ascribed to BNT thin film with a preferred growth direction of a-axis, resulting in effective enhancement of d33,f. Besides, all the thin films exhibit good optical transmittance in the range of 500-800 nm and the optical band gaps increase from 3.43 eV to 3.52 eV due to Nd doping.

  3. Design and synthesis of comonomers to enhance the optical, physical, and thermal properties of poly(ethylene terephthalate)

    NASA Astrophysics Data System (ADS)

    Connor, Daniel Martin

    Poly(ethylene terephthalate) (PET) is one of the world's most important commodity plastics. The largest volume applications of PET include textile fiber, tire cord, and packaging materials. There are many opportunities for improving the properties of PET that are associated with its various applications. We address three of the major application driven issues in PET: Increasing the optical brightness, increasing the crystallization rate, and enhancing the optical clarity through inhibition of crystallization. Each of the projects is summarized below. A new class of monomeric fused aromatic fluorescent brightening agents based on pyrene and anthracene have been designed and synthesized. The monomers: dimethyl 1,6-pyrene dicarboxylate, dimethyl 1,8-pyrenedicarboxylate, dimethyl 2,7-pyrenedicarboxylate, 1,9-bis(2-carboxybenzoyl)pyrene dimethyl ester, dimethyl 2,6-anthracenedicarboxylate, dimethyl 2,7-anthracenedicarboxylate and dimethyl 9,10-anthracenedicarboxylate were copolymerized with poly(ethylene terephthalate) and their optical properties were assessed. All of the polymers gave blue fluorescence with the copolymer containing dimethyl 1,6-pyrenedicarboxylate being the brightest. The synthesis of 2,7-substituted pyrene derivatives needed for the optical brightening project and for the crystallization rate enhancement project posed unique challenges. Optimized synthetic procedures for these compounds were developed. Pyrenes derivatized in the 2- and 7-positions were prepared by reduction of pyrene to 4,5,9,10-tetrahydropyrene followed by electrophilic aromatic substitution and re-aromatization. An optimized procedure is presented for hydrogenation of pyrene to provide 4,5,9,10-tetrahydropyene in high yield, which facilitates a convenient synthesis of dimethyl 2,7-pyrenedicarboxylate.

  4. Enhanced Optical Properties of Chemical Vapor Deposited Single Crystal Diamond by Low-Pressure/High-Temperature Annealing

    SciTech Connect

    Meng, Y.; Yan, C; Lai, Y; Krasnicki, S; Shu, H; Yu, T; Liang, Q; Mao, H; Hemley, R

    2008-01-01

    Single crystal diamond produced by chemical vapor deposition (CVD) at very high growth rates (up to 150 em/h) has been successfully annealed without graphitization at temperatures up to 2200 C and pressures <300 torr. Crystals were annealed in a hydrogen environment by using microwave plasma techniques for periods of time ranging from a fraction of minute to a few hours. This low-pressure/high-temperature (LPHT) annealing enhances the optical properties of this high-growth rate CVD single crystal diamond. Significant decreases are observed in UV, visible, and infrared absorption and photoluminescence spectra. The decrease in optical absorption after the LPHT annealing arises from the changes in defect structure associated with hydrogen incorporation during CVD growth. There is a decrease in sharp line spectral features indicating a reduction in nitrogen-vacancy-hydrogen (NVH-) defects. These measurements indicate an increase in relative concentration of nitrogen-vacancy (NV) centers in nitrogen-containing LPHT-annealed diamond as compared with as-grown CVD material. The large overall changes in optical properties and the specific types of alterations in defect structure induced by this facile LPHT processing of high-growth rate single-crystal CVD diamond will be useful in the creation of diamond for a variety of scientific and technological applications.

  5. Controlling electron trap depth to enhance optical properties of persistent luminescence nanoparticles for in vivo imaging.

    PubMed

    Maldiney, Thomas; Lecointre, Aurélie; Viana, Bruno; Bessière, Aurélie; Bessodes, Michel; Gourier, Didier; Richard, Cyrille; Scherman, Daniel

    2011-08-01

    Focusing on the use of nanophosphors for in vivo imaging and diagnosis applications, we used thermally stimulated luminescence (TSL) measurements to study the influence of trivalent lanthanide Ln(3+) (Ln = Dy, Pr, Ce, Nd) electron traps on the optical properties of Mn(2+)-doped diopside-based persistent luminescence nanoparticles. This work reveals that Pr(3+) is the most suitable Ln(3+) electron trap in the diopside lattice, providing optimal trap depth for room temperature afterglow and resulting in the most intense luminescence decay curve after X-ray irradiation. This luminescence dependency toward the electron trap is maintained through additional doping with Eu(2+), allowing UV-light excitation, critical for bioimaging applications in living animals. We finally identify a novel composition (CaMgSi(2)O(6):Eu(2+),Mn(2+),Pr(3+)) for in vivo imaging, displaying a strong near-infrared afterglow centered on 685 nm, and present evidence that intravenous injection of such persistent luminescence nanoparticles in mice allows not only improved but highly sensitive detection through living tissues. PMID:21702453

  6. A fiber optic probe design to measure depth- limited optical properties in-vivo with Low-coherence Enhanced Backscattering (LEBS) Spectroscopy

    PubMed Central

    Mutyal, Nikhil N.; Radosevich, Andrew; Gould, Bradley; Rogers, Jeremy D.; Gomes, Andrew; Turzhitsky, Vladimir; Backman, Vadim

    2012-01-01

    Low-coherence enhanced backscattering (LEBS) spectroscopy is an angular resolved backscattering technique that is sensitive to sub-diffusion light transport length scales in which information about scattering phase function is preserved. Our group has shown the ability to measure the spatial backscattering impulse response function along with depth-selective optical properties in tissue ex-vivo using LEBS. Here we report the design and implementation of a lens-free fiber optic LEBS probe capable of providing depth-limited measurements of the reduced scattering coefficient in-vivo. Experimental measurements combined with Monte Carlo simulation of scattering phantoms consisting of polystyrene microspheres in water are used to validate the performance of the probe. Additionally, depth-limited capabilities are demonstrated using Monte Carlo modeling and experimental measurements from a two-layered phantom. PMID:23037017

  7. Ethylenediamine-modified graphene oxide covalently functionalized with a tetracarboxylic Zn(ii) phthalocyanine hybrid for enhanced nonlinear optical properties.

    PubMed

    Li, Zongle; He, Chunying; Wang, Zhao; Gao, Yachen; Dong, Yongli; Zhao, Cheng; Chen, Zhimin; Wu, Yiqun; Song, Weina

    2016-07-01

    Tetracarboxylic Zn(ii) phthalocyanine-amino functionalized graphene oxide (ZnPcC4-NGO) hybrid materials have been prepared by a covalent functionalization method. The characterizations indicate that the amino-functionalization of GO has an important influence on the structure and photophysical properties of the ZnPcC4-NGO hybrid. The ZnPcC4-NGO hybrid exhibits enhanced photo-induced electron transfer or energy transfer (PET/ET), compared to the ZnPcC4 covalent functionalized GO (ZnPcC4-GO), owing to the presence of the extended sp(2) carbon configurations, along with the partial reduction of the NGO nanosheets and the introduction of electron-donating ethylenediamine. The nonlinear optical (NLO) properties of the hybrids were investigated using the Z-scan technique at 532 nm with 4 ns laser pulses. The results show that the efficient covalent functionalization and partial reduction of NGO cause the ZnPcC4-NGO hybrid to possess evidently larger NLO properties than the individual NGO, ZnPcC4 and the ZnPcC4-GO hybrid. The enhanced NLO performance can be attributed to the increased excited state absorption from the extended sp(2) carbon configurations of the NGO moiety, reverse saturable absorption arising from ZnPcC4 moiety, and the contribution of the efficient PET/ET process between the ZnPcC4 and NGO moieties in the hybrid. PMID:27296527

  8. On the optical and morphological properties of microstructured Black Silicon obtained by cryogenic-enhanced plasma reactive ion etching

    NASA Astrophysics Data System (ADS)

    Nguyen, K. N.; Basset, P.; Marty, F.; Leprince-Wang, Y.; Bourouina, T.

    2013-05-01

    Motivated by the need for obtaining low reflectivity silicon surfaces, we report on (sub-) micro-texturing of silicon using a high throughput fabrication process involving SF6/O2 reactive ion etching at cryogenic temperatures, leading to Black Silicon (BS). The corresponding high aspect ratio conical spikes of the microstructured surface give rise to multiple reflections and hence, enhanced absorption under electromagnetic radiation. Aiming a better understanding of this mechanism, we performed a systematic study by varying several plasma process parameters: O2/SF6 gas flow rate ratio, silicon temperature, bias voltage, and etching time. We determined the process window which leads to BS formation and we studied the influence of the process parameters on the surface morphology of the obtained BS samples, through analysis of scanning electron microscopy images. The measured optical reflectance of BS is in the order of 1% in the visible and near infrared ranges (400-950 nm). We noticed that the lowest reflectance is obtained close to the threshold parameters of BS formation. Absorptance spectral response of BS is measured from 1.3 to 17 μm, and we observed a great enhancement of absorptance up to about 75% compared to flat silicon. We also obtained through these experiments, a clear evidence of a correlation between the excellent optical properties and the aspect ratio of the BS conical microstructures in the measured wavelength ranges.

  9. Monodisperse spindle-like FeWO{sub 4} nanoparticles: Controlled hydrothermal synthesis and enhanced optical properties

    SciTech Connect

    Guo, Jinxue; Zhou, Xiaoyu; Lu, Yibin; Zhang, Xiao; Kuang, Shaoping; Hou, Wanguo

    2012-12-15

    Monodisperse FeWO{sub 4} nanoparticles with specific spindle-like morphology have been synthesized in the presence of citric acid through hydrothermal process. In the synthesis route, citric acid played four roles such as the reducing agent, chelating regents, structure-directing agent and stabilizing agents. In addition, the morphology of FeWO{sub 4} was dramatically tuned by the pH value of the precursor medium. The optical properties of FeWO{sub 4} were investigated with UV-Vis spectra and photoluminescence spectroscopy. The photocatalytic experiments demonstrated that the decomposition efficiency of the monodisperse spindle-like FeWO{sub 4} nanoparticles is 74% after 30 min of UV irradiation, which displayed remarkable enhanced photodegradation activity compared with ordinary FeWO{sub 4} sample (57%) and normal TiO{sub 2} photocatalysts P-25 (56%). - Monodisperse spindle-like FeWO{sub 4} nanoparticles with enhanced photocatalytic activities. Highlights: Black-Right-Pointing-Pointer Monodisperse spindle-like FeWO{sub 4} were synthesized with hydrothermal method. Black-Right-Pointing-Pointer Citric acid plays key roles in the hydrothermal synthesis. Black-Right-Pointing-Pointer Their morphology can be tuned with pH value of the precursor medium. Black-Right-Pointing-Pointer They show enhanced photocatalytic activities with irradiation of UV light.

  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. Nonlinear optical properties and surface-plasmon enhanced optical limiting in Ag-Cu nanoclusters co-doped in SiO{sub 2} Sol-Gel films

    SciTech Connect

    Kiran, P. Prem; Shivakiran Bhaktha, B.N.; Rao, D. Narayana; De, Goutam

    2004-12-01

    The nonlinear optical properties and the role of the surface-plasmon resonance (SPR) on optical limiting (OL) properties of Ag-Cu nanoclusters co-doped in SiO{sub 2} matrix prepared using the sol-gel technique with a Cu/Ag molar ratio of 1, 2 and 3, respectively, are presented. The studies were made using the second harmonic of high-power nanosecond and picosecond Nd:YAG lasers. These films show a self-defocusing nonlinearity with both nanosecond and picosecond pulses and a good nonlinear absorption behavior with the nanosecond pulse excitation. The nonlinear refractive index decreased with decreasing particle size, whereas the nonlinear absorption increased with an increase in Cu concentration. The observed nonlinear absorption is explained by taking into account the cumulative effect of both the intraband and interband mechanisms. The excitation near the SPR of Cu resulted in an enhanced OL behavior with increasing Cu concentration. No such concentration dependence is observed when the excitation is near the SPR of Ag, however, the limiting threshold is reduced approximately 10-17 times. Excitation at wavelengths far below the SPR of Ag and Cu has not shown any OL behavior. The major contribution toward OL is observed to be from the interband absorption and from a possible energy transfer within the higher unoccupied states of Cu and Ag. Although nonlinear scattering is observed at higher intensities, its contribution is found to be much less than that of the nonlinear absorption assisted by an energy transfer.

  12. Optical and surface enhanced Raman scattering properties of Au nanoparticles embedded in and located on a carbonaceous matrix.

    PubMed

    Prakash, Jai; Kumar, Vinod; Kroon, R E; Asokan, K; Rigato, V; Chae, K H; Gautam, S; Swart, H C

    2016-01-28

    Au nanoparticles (NPs) on the surface and embedded in a matrix have been the subject of studies dealing with a variety of spectroscopic and sensing applications. Here, we report on low energy Ar ion induced evolution of the morphology of a thin Au film on a polyethylene terephthalate (PET) substrate along with thermodynamic interpretations, and corresponding unique surface plasmon resonance (SPR) and photoluminescence (PL) properties. These properties are linked to the variation of surface nanostructures and the surface enhanced Raman scattering (SERS) effect of methyl orange (MO) dye molecules adsorbed on the surface. Ion induced thermal spike and sputtering resulted in dewetting of the film with subsequent formation of spherical NPs. This was followed by embedding of the NPs in the modified PET due to the thermodynamic driving forces involved. The surface and interface morphologies were studied using atomic force microscopy and cross-sectional transmission electron microscopy. X-ray photoelectron spectroscopy was used to study the chemical changes in the system upon irradiation. The optical properties were studied by diffuse reflectance UV-Vis spectroscopy and PL using a 325 nm He-Cd laser. The red shift of the SPR absorption and the blue shift of the PL emission have been correlated with the surface morphology. The blue PL emission bands at around 3.0 eV are in good agreement with the literature with respect to the morphological changes and the blue shift is attributed to compressive strain on the embedded Au NPs. Enhancement of the SERS signals is observed and found to be correlated with the SPR response of the Au nanostructures. The SERS analyses indicate that MO molecules may be adsorbed with different orientations on these surfaces i.e. Au NPs located on the surface or embedded in the modified PET. These polymeric substrates modified by NPs can have a potential application in solid-state light emitting devices and can be applied in SERS based sensors for the

  13. Enhanced optical properties of TiO2 nanoceramic films by oxygen atmosphere.

    PubMed

    Lin, Su-Shia; Wu, Ding-Kun

    2010-02-01

    TiO2 nanoceramic films were deposited on glasses by rf magnetron sputtering and corresponded to nanocrystalline anatase. The porosity and surface roughness decreased with the oxygen pressure. The optical transmission of TiO2 nanoceramic films obviously increased with the decrease of film thickness or the increase of oxygen pressure, especially in the visible region. Moiré deflectometry was used to measure the nonlinear refractive indices of TiO2 films deposited in a mixed Ar-O2 atmosphere. The nonlinear refractive index was measured to be of the order of 10(-8) cm2 W(-1) and the change in refractive index was of the order of 10(-5). As the oxygen pressure increased, the transparent TiO2 film exhibited a high linear refractive index, a low stress and a low stress-optical coefficient. PMID:20352762

  14. Optical properties of ITO/ZnO Schottky diode with enhanced UV Photoresponse

    NASA Astrophysics Data System (ADS)

    Lee, Hsin-Yen; Chern, Ming-Yau

    2015-11-01

    Photoluminescence (PL) spectra of zinc oxide (ZnO) samples with different hydrogen peroxide (H2O2) treatment durations were measured to examine several point defects on the surfaces of the films. The results suggest successful oxidation through the reaction between oxygen radicals dissociated from H2O2 and the ZnO surface. To further confirm the defect-induced gain mechanism, we fabricated highly transparent indium-tin-oxide (ITO)/ZnO Schottky diodes and measured the key diode characteristics. Photocurrents were measured at different wavelengths, and possible explanations for the high optical gain within the ultraviolet (UV) region are provided.

  15. Enhanced optical property in quaternary GaInAsSb/AlGaAsSb quantum wells

    SciTech Connect

    Lin, Chien-Hung Lee, Chien-Ping

    2014-10-21

    High quality GaInAsSb/AlGaAsSb quantum wells (QWs) have been grown by molecular beam epitaxy using proper interface treatments. By controlling the group-V elements at interfaces, we obtained excellent optical quality QWs, which were free from undesired localized trap states, which may otherwise severely affect the exciton recombination. Strong and highly efficient exciton emissions up to room temperature with a wavelength of 2.2 μm were observed. A comprehensive investigation on the QW quality was carried out using temperature dependent and power dependent photoluminescence (PL) measurements. The PL emission intensity remains nearly constant at low temperatures and is free from the PL quenching from the defect induced localized states. The temperature dependent emission energy had a bulk-like behavior, indicating high quality well/barrier interfaces. Because of the uniformity of the QWs and smooth interfaces, the low temperature limit of inhomogeneous line width broadening is as small as 5 meV.

  16. Enhanced solid-phase immunoassay using gold nanoshells: effect of nanoparticle optical properties

    NASA Astrophysics Data System (ADS)

    Khlebtsov, Boris; Khlebtsov, Nikolai

    2008-10-01

    Plasmon-resonant nanoparticle-labeled immunoassays provide a simple, low-cost and effective way of detecting target molecules in solutions. The optical mechanisms behind their efficiency, however, have not been addressed until now. We present the first theoretical description of nanoparticle-labeled dot immunoassay and its experimental verification with functionalized 15 nm colloidal gold nanospheres and silica/gold nanoshells (GNs). Three types of GNs, with silica core diameters of 100, 140 and 180 nm and a gold shell thickness of about 15 nm, were studied in our experiments. The fabricated markers were characterized by electron and atomic-force microscopy, UV-vis spectroscopy and dynamic light scattering. A normal rabbit serum (the target IgG molecules) and sheep antirabbit antibodies (the probing molecules) were used as a biospecific model. The minimal detection limit for IgG target molecules was about 15 ng in the case of a standard dot-assay protocol based on 15 nm colloidal gold particles conjugated with probing molecules. In contrast to this observation, a simple replacement of 15 nm gold labels by GN conjugates resulted in a drastic increase in detection sensitivity of up to 0.25 ng in the case of 180/15 nm GNs and of up to 0.5-1 ng for 100/15 and 140/15 GNs. By using the theory developed, we explained the dependences of the low detection limit, the maximal-color intensity and the probe-load saturation limit on the particle parameters.

  17. Enhanced solid-phase immunoassay using gold nanoshells: effect of nanoparticle optical properties.

    PubMed

    Khlebtsov, Boris; Khlebtsov, Nikolai

    2008-10-29

    Plasmon-resonant nanoparticle-labeled immunoassays provide a simple, low-cost and effective way of detecting target molecules in solutions. The optical mechanisms behind their efficiency, however, have not been addressed until now. We present the first theoretical description of nanoparticle-labeled dot immunoassay and its experimental verification with functionalized 15 nm colloidal gold nanospheres and silica/gold nanoshells (GNs). Three types of GNs, with silica core diameters of 100, 140 and 180 nm and a gold shell thickness of about 15 nm, were studied in our experiments. The fabricated markers were characterized by electron and atomic-force microscopy, UV-vis spectroscopy and dynamic light scattering. A normal rabbit serum (the target IgG molecules) and sheep antirabbit antibodies (the probing molecules) were used as a biospecific model. The minimal detection limit for IgG target molecules was about 15 ng in the case of a standard dot-assay protocol based on 15 nm colloidal gold particles conjugated with probing molecules. In contrast to this observation, a simple replacement of 15 nm gold labels by GN conjugates resulted in a drastic increase in detection sensitivity of up to 0.25 ng in the case of 180/15 nm GNs and of up to 0.5-1 ng for 100/15 and 140/15 GNs. By using the theory developed, we explained the dependences of the low detection limit, the maximal-color intensity and the probe-load saturation limit on the particle parameters. PMID:21832707

  18. 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.

  19. Formation of oxygen vacancies and Ti3+ state in TiO2 thin film and enhanced optical properties by air plasma treatment

    PubMed Central

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-01-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2−, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift. PMID:27572095

  20. Formation of oxygen vacancies and Ti(3+) state in TiO2 thin film and enhanced optical properties by air plasma treatment.

    PubMed

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-01-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti(3+), Ti(4+), O(2-), oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti(3+) and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti(3+) and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift. PMID:27572095

  1. Efficient Donor Impurities in ZnO Nanorods by Polyethylene Glycol for Enhanced Optical and Glutamate Sensing Properties.

    PubMed

    Elhag, Sami; Khun, Kimleang; Khranovskyy, Volodymyr; Liu, Xianjie; Willander, Magnus; Nur, Omer

    2016-01-01

    In this paper, we show that the possibility of using polyethylene glycol (EG) as a hydrogen source and it is used to assist the hydrothermal synthesis of ZnO nanorods (ZNRs). EG doping in ZNRs has been found to significantly improve their optical and chemical sensing characteristics toward glutamate. The EG was found to have no role on the structural properties of the ZNRs. However, the x-ray photoelectron spectroscopy (XPS) suggests that the EG could induce donor impurities effect in ZnO. Photoluminescence (PL) and UV-Vis. spectra demonstrated this doping effect. Mott-Schottky analysis at the ZNRs/electrolyte interface was used to investigate the charge density for the doped ZNRs and showed comparable dependence on the used amount of EG. Moreover, the doped ZNRs were used in potentiometric measurements for glutamate for a range from 10(-6) M to 10(-3) M and the potential response of the sensor electrode was linear with a slope of 91.15 mV/decade. The wide range and high sensitivity of the modified ZNRs based glutamate biosensor is attributed to the doping effect on the ZNRs that is dictated by the EG along with the high surface area-to-volume ratio. The findings in the present study suggest new avenues to control the growth of n-ZnO nanostructures and enhance the performance of their sensing devices. PMID:26861342

  2. Efficient Donor Impurities in ZnO Nanorods by Polyethylene Glycol for Enhanced Optical and Glutamate Sensing Properties

    PubMed Central

    Elhag, Sami; Khun, Kimleang; Khranovskyy, Volodymyr; Liu, Xianjie; Willander, Magnus; Nur, Omer

    2016-01-01

    In this paper, we show that the possibility of using polyethylene glycol (EG) as a hydrogen source and it is used to assist the hydrothermal synthesis of ZnO nanorods (ZNRs). EG doping in ZNRs has been found to significantly improve their optical and chemical sensing characteristics toward glutamate. The EG was found to have no role on the structural properties of the ZNRs. However, the x-ray photoelectron spectroscopy (XPS) suggests that the EG could induce donor impurities effect in ZnO. Photoluminescence (PL) and UV-Vis. spectra demonstrated this doping effect. Mott-Schottky analysis at the ZNRs/electrolyte interface was used to investigate the charge density for the doped ZNRs and showed comparable dependence on the used amount of EG. Moreover, the doped ZNRs were used in potentiometric measurements for glutamate for a range from 10−6 M to 10−3 M and the potential response of the sensor electrode was linear with a slope of 91.15 mV/decade. The wide range and high sensitivity of the modified ZNRs based glutamate biosensor is attributed to the doping effect on the ZNRs that is dictated by the EG along with the high surface area-to-volume ratio. The findings in the present study suggest new avenues to control the growth of n-ZnO nanostructures and enhance the performance of their sensing devices. PMID:26861342

  3. Nonlinear optical properties of composite materials

    NASA Technical Reports Server (NTRS)

    Haus, Joseph W.; Inguva, Ramarao

    1991-01-01

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

  4. Addition of Hetero-Atoms to the Polymer Film by Plasma Enhanced Polymerization and its Optical Properties

    NASA Astrophysics Data System (ADS)

    Moriki, Kazunori; Yumoto, Motoshige

    Plasma enhanced polymerization is an attractive technology to fabricate an optical polymer waveguide, because it has capability to provide an uniform thickness film on a substrate with various surface geometry, and to provide change of refractive index by controlling a proportion of source monomer mixing. In the present paper we discuss optical constants and molecule structures of the films added hetero-atoms, O, N and F in the CHx network of polymer. Refractive index of those films changes from 1.52 to 1.63 at 1.0 μm wavelength, depending on the variety of hetero-atoms. Fluorine atoms added into a film decreases refractive index of the film. Oxygen atoms added into a film, which form ester structure (- COO-), decrease refractive index of the film, and some O atoms token into a film as OH base will increase optical absorption in inferred region for optical communication. Nitrogen atoms added increase optical absorption due to forming NH2 base. Finally, sp3/sp2 fraction controlling in the film will be a suitable to control refractive index of the film for an optical waveguide, for example by using mixed monomer of C6H6 and C6H10.

  5. Nanoplasmonics: Enhancement of optical radiation

    NASA Astrophysics Data System (ADS)

    Alzaim, Safa

    The way a fluorophore behaves in free space is very different from the way that it behaves in the presence of a metal nanosphere. This change is because the fluorophore, in its excited state, interacts with the free electrons in the metal. The charge density of the free electrons oscillate as surface plasmons, and when an electric field is applied, the surface plasmons couple to the field to produce surface plasmon polaritons. The resulting resonance modifies the optical properties of the fluorophore. The behaviors of nanoplasmonics systems derive from the interaction of light with conduction electrons, which means that understanding nanoplasmonics requires understanding the Drude Model and Maxwell's Equations. The Drude Model gives a basis for understanding free electron behavior, in order to investigate the dielectric function and electrodynamics in the context of a nanoplasmonic system. Thisstudy offers a mathematical model for the enhancement of the fluorescence in the presence of a silver nanosphere.

  6. Optical properties of chitin: surface-enhanced Raman scattering substrates based on antireflection structures on cicada wings

    NASA Astrophysics Data System (ADS)

    Stoddart, P. R.; Cadusch, P. J.; Boyce, T. M.; Erasmus, R. M.; Comins, J. D.

    2006-02-01

    The transparent wings of some cicada species present ordered arrays of papillary structures with a spacing of approximately 200 nm. These structures serve an antireflection function, with optical transmission peaking at a value of approximately 98% and rising above 90% over a broad band from 450 to 2500 nm. The dimensions of the papillae are comparable to the roughness scale of surface-enhanced Raman scattering (SERS) substrates. SERS measurements performed on silver- and gold-coated wings display enhancement factors of approximately 106 with no apparent background contribution from the wing.

  7. Enhanced radiation resistant fiber optics

    DOEpatents

    Lyons, P.B.; Looney, L.D.

    1993-11-30

    A process for producing an optical fiber having enhanced radiation resistance is provided, the process including maintaining an optical fiber within a hydrogen-containing atmosphere for sufficient time to yield a hydrogen-permeated optical fiber having an elevated internal hydrogen concentration, and irradiating the hydrogen-permeated optical fiber at a time while the optical fiber has an elevated internal hydrogen concentration with a source of ionizing radiation. The radiation source is typically a cobalt-60 source and the fiber is pre-irradiated with a dose level up to about 1000 kilorads of radiation. 4 figures.

  8. Enhanced radiation resistant fiber optics

    DOEpatents

    Lyons, Peter B.; Looney, Larry D.

    1993-01-01

    A process for producing an optical fiber having enhanced radiation resitance is provided, the process including maintaining an optical fiber within a hydrogen-containing atmosphere for sufficient time to yield a hydrogen-permeated optical fiber having an elevated internal hydrogen concentration, and irradiating the hydrogen-permeated optical fiber at a time while the optical fiber has an elevated internal hydrogen concentration with a source of ionizing radiation. The radiation source is typically a cobalt-60 source and the fiber is pre-irradiated with a dose level up to about 1000 kilorads of radiation.

  9. Radio frequency sputtered Al:ZnO-Ag transparent conductor: A plasmonic nanostructure with enhanced optical and electrical properties

    NASA Astrophysics Data System (ADS)

    Sytchkova, Anna; Luisa Grilli, Maria; Rinaldi, Antonio; Vedraine, Sylvain; Torchio, Philippe; Piegari, Angela; Flory, François

    2013-09-01

    Optimization of metal-based transparent conductors (MTCs) made of silver and aluminium-doped zinc oxide (AZO) prepared by radio-frequency (r.f.) sputtering has been carried out through tuning of metal film properties. The influence of morphology and related plasmonic features of AZO/Ag/AZO MTCs on their optical and electrical performance is demonstrated and it is shown that the nominal thickness of the silver layer itself is not the most crucial value determining the MTC performance. The MTC performance has been optimized by a search of deposition conditions ensuring fractal-type metal layer formation up to a certain coalescence state that enables full gaining from silver optical properties, including its plasmonic features. For 150 W- and 200 W-deposited silver, MTCs with maximum transmittance as high as 83.6% have been obtained. These coatings have a figure of merit as good as 0.01 Ω-1 and a remarkably wide spectral transparency region: transmittance higher than 70% down to 1200 nm for 200W-samples. Modelling of the MTC coatings is proposed additionally, based on variable angle spectroscopic ellipsometric measurements, which takes into account the variation of the optical properties of silver when deposited in various conditions and embedded in a semiconductor stack.

  10. Optical limiting by chemically enhanced bacteriorhodopsin films

    NASA Astrophysics Data System (ADS)

    Song, Q. W.; Zhang, Chungping; Gross, Richard; Birge, Robert

    1993-05-01

    The optical limiting properties of a thin film (about 150 microns) of chemically enhanced bacteriorhodopsin under CW laser illumination is investigated. The effective nonlinearity n2 of the film is measured with the z-scan method. Anomalous absorption at different wavelengths as a function of illumination intensity is observed.

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

    PubMed

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

    2016-04-01

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

  12. Measurement of food optical properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  13. Electronic structures and enhanced optical properties of blue phosphorene/transition metal dichalcogenides van der Waals heterostructures

    PubMed Central

    Peng, Qiong; Wang, Zhenyu; Sa, Baisheng; Wu, Bo; Sun, Zhimei

    2016-01-01

    As a fast emerging topic, van der Waals (vdW) heterostructures have been proposed to modify two-dimensional layered materials with desired properties, thus greatly extending the applications of these materials. In this work, the stacking characteristics, electronic structures, band edge alignments, charge density distributions and optical properties of blue phosphorene/transition metal dichalcogenides (BlueP/TMDs) vdW heterostructures were systematically studied based on vdW corrected density functional theory. Interestingly, the valence band maximum and conduction band minimum are located in different parts of BlueP/MoSe2, BlueP/WS2 and BlueP/WSe2 heterostructures. The MoSe2, WS2 or WSe2 layer can be used as the electron donor and the BlueP layer can be used as the electron acceptor. We further found that the optical properties under visible-light irradiation of BlueP/TMDs vdW heterostructures are significantly improved. In particular, the predicted upper limit energy conversion efficiencies of BlueP/MoS2 and BlueP/MoSe2 heterostructures reach as large as 1.16% and 0.98%, respectively, suggesting their potential applications in efficient thin-film solar cells and optoelectronic devices. PMID:27553787

  14. Electronic structures and enhanced optical properties of blue phosphorene/transition metal dichalcogenides van der Waals heterostructures.

    PubMed

    Peng, Qiong; Wang, Zhenyu; Sa, Baisheng; Wu, Bo; Sun, Zhimei

    2016-01-01

    As a fast emerging topic, van der Waals (vdW) heterostructures have been proposed to modify two-dimensional layered materials with desired properties, thus greatly extending the applications of these materials. In this work, the stacking characteristics, electronic structures, band edge alignments, charge density distributions and optical properties of blue phosphorene/transition metal dichalcogenides (BlueP/TMDs) vdW heterostructures were systematically studied based on vdW corrected density functional theory. Interestingly, the valence band maximum and conduction band minimum are located in different parts of BlueP/MoSe2, BlueP/WS2 and BlueP/WSe2 heterostructures. The MoSe2, WS2 or WSe2 layer can be used as the electron donor and the BlueP layer can be used as the electron acceptor. We further found that the optical properties under visible-light irradiation of BlueP/TMDs vdW heterostructures are significantly improved. In particular, the predicted upper limit energy conversion efficiencies of BlueP/MoS2 and BlueP/MoSe2 heterostructures reach as large as 1.16% and 0.98%, respectively, suggesting their potential applications in efficient thin-film solar cells and optoelectronic devices. PMID:27553787

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  16. Synthesis of reduced graphene oxide and enhancement of its electrical and optical properties by attaching Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Khan, Sunny; Ali, Javid; Harsh; Husain, M.; Zulfequar, M.

    2016-07-01

    Graphene has attracted the attention of the scientists and researchers because of its peculiar properties. Because of various unique properties, graphene can be used in sensing device applications, solar cells and liquid crystal display devices etc. In this research paper, we present a chemical route towards bulk production of r-GO (reduced graphene oxide). We have employed a modified method to achieve better results which is often termed as modified Hummer's and Offeman method. It is modified in terms of filtration technique. We have also attached silver nanoparticles (Ag-NP) to as synthesised r-GO. After successful growth, silver nanoparticles have been attached to r-GO by suitable treatment with AgNO3 (aq.) N/50 solution. The as grown samples were characterised by FESEM, Raman Spectroscopy and EDS to make sure that r-GO and r-GO-Ag-NP have been successfully synthesised. The electrical and optical studies of the as grown samples were performed by dc conductivity measurements and UV visible spectroscopy. The conductivity was found to have increased with attachment of Ag-NP. The optical transmittance also improved to 90% as against 70% before Ag-NP attachment. The reduced graphene oxide attached with silver nanoparticles could find promising applications in synthesis of transparent electrode materials and optoelectronic devices.

  17. Enhanced optical tracking

    NASA Astrophysics Data System (ADS)

    McSheery, Tracy

    2008-04-01

    Enhanced tracking is accomplished by increasing the resolution, frame rate and processing capabilities in tracking dynamic regions of interest for vision applications. In many proven algorithms, the ability to distinguish an object and track it is dependent on the system performance in more than one attribute. We have conducted studies on proven techniques such as Active Appearance Models, Principle Component Analysis and Eigen tracking. All perform better as the camera resolution increases, and camera frame rate increases. Additional opportunities have been observed by combining these techniques, taking advantage of Multicore CPUs, and GPU graphic card processing. Results from an 8 Megapixel commercial sensor combined with a Field Programmable Gate array are presented, and algorithm performance compared with down scaled images of the same scenes, and simulated typical 30 hertz frame rates verses the 120 hertz to 300 hertz typical of this smart camera.

  18. Revealing nanoscale optical properties and morphology in perfluoropentacene films by confocal and tip-enhanced near-field optical microscopy and spectroscopy.

    PubMed

    Wang, Xiao; Broch, Katharina; Schreiber, Frank; Meixner, Alfred J; Zhang, Dai

    2016-06-21

    Combining high resolution optical microscopy and spectroscopy, we propose a novel, generally applicable and highly sensitive method for determining the local morphology in organic semiconductor thin films (e.g. perfluoropentacene (PFP)). An azimuthally or radially polarized doughnut mode (APDM or RPDM) laser beam is focused by a high numerical aperture parabolic-mirror to excite a diffraction limited volume of the PFP film with an electric field polarized either exclusively in-plane or dominantly out-of-plane (relative to the substrate). We find two distinct morphologies of thin PFP films: molecular aggregates and crystalline terraces. The well-defined dipole emission patterns observed from the molecular aggregates strongly suggest the presence of localized excitations. For both laser modes, we observe that for the PFP aggregates, the photoluminescence (PL) emission from the main electronic transition is blue-shifted by about 10 meV, as compared to that from the molecular terraces. For the C-C bending modes, the B3g at 1581 cm(-1) (ν1) and the Ag at 1316 cm(-1) (ν0), we observe a decrease of the intensity ratio (Iν1/Iν0) from 0.6 (terrace) to 0.15 (aggregate). Furthermore, the intensity ratios (IAPDM/IRPDM) of ν1 excited by different polarizations increase from 0.12 (terrace) to 0.73 (aggregate). These results indicate that the PFP molecules orient rather parallel to the substrate in the aggregates, whilst more upright in the terraces. Benefiting from the nanometer scale optical resolution offered by the tip-enhanced near-field optical method, we observe clear optical contrasts between the molecular aggregate and the terrace as well as individual layers within a terrace. Tip-enhanced optical spectra locally taken from the molecular terrace and the aggregate show similar blue-shift of the main PL peak and change in the Raman intensity with different polarizations as from the far-field assemble-measurements, which further confirms the different molecular

  19. 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

  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 antenna enhanced spontaneous emission.

    PubMed

    Eggleston, Michael S; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C

    2015-02-10

    Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼ 200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ∼ 115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼ 2,500 × spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d(2). Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency. PMID:25624503

  2. Optical antenna enhanced spontaneous emission

    PubMed Central

    Eggleston, Michael S.; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C.

    2015-01-01

    Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼200 THz optical frequency show a spontaneous emission intensity enhancement of 35× corresponding to a spontaneous emission rate speedup ∼115×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼2,500× spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d2. Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, Io = qω|xo|/d, feeding the antenna-enhanced spontaneous emission, where q|xo| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency. PMID:25624503

  3. Electrical and Optical Properties of Si-Incorporated a-C:H Films via the Radio Frequency Plasma-Enhanced Chemical Vapor Deposition Method.

    PubMed

    Kim, In Jun; Choi, Won Seok; Hong, Byungyou

    2016-05-01

    The optical and electrical properties of silicon-incorporated hydrogenated amorphous carbon (a-C:H:Si) films deposited via the radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) method using a mixture of CH4, H2, and SiH4 were observed. The silane gas whose ranged from 0 to 25 vol.% [SiH4/(SiH4 + CH4) was fed into the reactor while the other deposition parameters were kept constant. The basic properties of these films were investigated via Raman spectroscopy, UV-visible spectrometry, I-V measurement, and surface profiling. The experiment results showed that the film thickness increased from 300 nm to 800 nm for the same deposition time as the silane gas increased. The Raman spectrum obtained from the silicon-incorporated a-C:H films suggested that the film property changed from graphitic-like to more diamond-like. As the silane gas increased, the optical gap, E04, slightly increased from 1.98 eV to 2.62 eV. It was shown that the Si atoms incorporated into the a-C:H films reduced the size of the sp2 clusters. As for the I-V characteristics, the Si-incorporated a-C:H films had a lower leakage current than the a-C:H films without Si. PMID:27483937

  4. Enhanced optical phase conjugation in nonlinear metamaterials.

    PubMed

    Kim, Kihong

    2014-12-15

    Optical phase conjugation by degenerate four-wave mixing in nonlinear metamaterials is studied theoretically by solving the coupled wave equations using a generalized version of the invariant imbedding method. The phase-conjugate reflectance and the lateral shift of the phase-conjugate reflected beams are calculated and their dependencies on the frequency, the polarization, the incident angle, the material properties and the structure are investigated in detail. It is found that the efficiency of phase conjugation can be significantly enhanced due to the enhancement of electromagnetic fields in various metamaterial structures. PMID:25607488

  5. Boron doping of diamond powder by enhanced diffusion and forced diffusion: Diffusion concentrations, mechanical, chemical and optical properties

    NASA Astrophysics Data System (ADS)

    Golshani, Fariborz

    Diamond, with its unique mechanical properties, is an excellent material for a wide range of applications. However, there exist some problems. One such problem is integration of diamond of diamond into tool's (usually tungsten-carbide) lattice matrix for the purpose of increasing its performance. The presence of cobalt in the matrix, which acts as a poison for diamond, causes graphitization and degradation of diamond. In addition, diamond graphitizes at sintering temperatures (1770 K). The results of this work suggest that boron has produced a protective layer for diamond, thus reducing the effects of annealing at high temperatures. Boron has been introduced into single crystal high pressure, high temperature diamond powder by enhanced diffusion and forced diffusion techniques. Enhanced diffusion resulted in higher concentrations of boron in diamond powder. Total boron concentrations of 500 to 600 ppm, and 10sp{20} cmsp{-3} at a depth of 0.5 micrometer, have been achieved. Hardness tests performed on doped samples reveal that diamond did not lose its strength due to diffusion at elevated temperatures. Raman spectroscopy and X-ray diffraction analysis did not show any change in the "quality" of diamond due to doping. Oxidation experiments performed on doped and undoped samples revealed that the samples with the highest boron concentrations had superior performance and resistance to oxidation. Final weight loss in these samples was much less than in undoped samples and samples with low boron concentrations. Scanning electron microscopy of these samples showed that degradation due to oxidation of heavily doped diamond samples was significantly less than other samples.

  6. 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.

  7. Nanoparticles for enhanced contrast optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Maule, César D.; Quaresma, Pedro; Carvalho, Patrícia A.; Jorge, Pedro; Pereira, Eulália; Rosa, Carla C.

    2008-09-01

    Recently the area of bioimaging has benefited from new types of image enhancing agents such as quantum dots, carbon nanotubes and other nanoparticles. Cellular or even molecular level resolution has been achieved with different techniques during these last years (i.a. Fluorescence microscopy, PET/CT scan, AFM). Optical Coherence Tomography (OCT) as an imaging technique should also profit from newly developed probes. In this work we explored the tunable properties of different types of nanoparticles as contrast enhancers in OCT applications. We mainly studied the development and characteristics of metallic nanoparticles with tunable properties: gold nanoshells made of a silica core coated with a gold shell. Nanoshell and nanoparticles processing techniques are discussed, as well as their optimization for designing particles with specific absorption and scattering characteristics, and its use in OCT imaging.

  8. Optical Properties Of Ceramic Fabrics

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  9. Nonlinearly enhanced sensing in coupled optical microresonators

    NASA Astrophysics Data System (ADS)

    Wang, Chao

    Optical microresonators that confine photons to micron dimensions with low loss at telecommunication wavelengths play an important role in building modern all-optical integrated circuit. Such systems attract a considerable amount of interest because of the compact size and easy fabrication with state-of-art technologies. One can use the microresonators as sensors, optical delay lines, filters, interferometers, and lasers. In this thesis, we investigate nonlinear effects for sensing application in microring resonators. We theoretically analyze the effect of the Kerr index, two-photon absorption, free-carrier absorption, and free-carrier dispersion. In particular, selfphase and cross-phase modulations caused by the Kerr index are shown to lead to a bifurcation of degenerate resonator mode intensities. Using coupled mode equations, we present the transmission properties of our resonator system with nonlinear effects included. New sensing mechanisms based on the nonlinear bistability and bifurcation are proposed to enhance the transmission's sensitivity to perturbations of the resonance frequency of the resonators. This is used to develop models of ultra-sensitive gyroscopes and refractive index sensors for detection of chemical analytes. The bifurcation dramatically enhances the Sagnac phase shift and therefore substantially lowers the minimum detectable rotation rate (< 1deg/hour) in a micro-resonator gyroscope. For index sensing, nonlinearities enhance the resonance frequency shift and a theoretical detection limit of 10-11 RIU is derived assuming common noises in micro-optical systems. In this work, we focus on silicon-on-insulator resonators but we also consider different platforms, including silicon oxynitride, Hydex, and chalcogenide glasses, and discuss the advantages of each. The results we show here highlight novel mechanisms that can be used in practical applications to improve the performance of a microresonator based optical sensor.

  10. Optical properties of human hair

    NASA Astrophysics Data System (ADS)

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

    1995-01-01

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

  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. Growth of monodisperse nanospheres of MnFe2O4 with enhanced magnetic and optical properties

    NASA Astrophysics Data System (ADS)

    Yasir, Rafique M.; Pan, Li-Qing; Qurat-ul-ain, Javed; Zubair, Iqbal M.; Qiu, Hong-Mei; Hassan, Farooq M.; Guo, Zhen-Gang; Tanveer, M.

    2013-10-01

    Highly dispersive nanospheres of MnFe2O4 are prepared by template free hydrothermal method. The nanospheres have 47.3-nm average diameter, narrow size distribution, and good crystallinity with average crystallite size about 22 nm. The reaction temperature strongly affects the morphology, and high temperature is found to be responsible for growth of uniform nanospheres. Raman spectroscopy reveals high purity of prepared nanospheres. High saturation magnetization (78.3 emu/g), low coercivity (45 Oe, 1 Oe = 79.5775 A·cm-1), low remanence (5.32 emu/g), and high anisotropy constant 2.84 × 104 J/m3 (10 times larger than bulk) are observed at room temperatures. The nearly superparamagnetic behavior is due to comparable size of nanospheres with superparamagnetic critical diameter Dcrspam. The high value of Keff may be due to coupling between the pinned moment in the amorphous shell and the magnetic moment in the core of the nanospheres. The nanospheres show prominent optical absorption in the visible region, and the indirect band gap is estimated to be 0.98 eV from the transmission spectrum. The prepared Mn ferrite has potential applications in biomedicine and photocatalysis.

  13. Multifunctional g-C(3)N(4) nanofibers: a template-free fabrication and enhanced optical, electrochemical, and photocatalyst properties.

    PubMed

    Tahir, Muhammad; Cao, Chuanbao; Mahmood, Nasir; Butt, Faheem K; Mahmood, Asif; Idrees, Faryal; Hussain, Sajad; Tanveer, M; Ali, Zulfiqar; Aslam, Imran

    2014-01-22

    We have developed a facile, scale up, and efficient method for the preparation of graphitic-C3N4 nanofibers (GCNNFs) as electrodes for supercapacitors and photocatalysts. The as-synthesized GCNNFs have 1D structure with higher concentration of nitrogen that is favorable for higher conductivity and electrochemical performance. Secondly, the high surface area of GCNNF provides a large electrode-electrolyte contact area, sufficient light harvesting and mass transfer, as well as increased redox potential. Thus, the GCNNF supercapacitor electrode shows high capacitance of 263.75 F g(-1) and excellent cyclic stability in 0.1 M Na2SO4 aqueous electrolyte with the capacitance retention of 93.6% after 2000 cycles at 1 A g(-1) current density. GCNNFs exhibit high capacitance of 208 F g(-1) even at 10 A g(-1), with the appreciable capacitance retention of 89.5%, which proves its better rate capability. Moreover, the GCNNF shows enhanced photocatalytic activity in the photodegradation of RhB in comparison to the bulk graphitic-C3N4 (GCN). The degradation rate constant of GCNNF photocatalyst is almost 4 times higher than GCN. The enhanced photocatalytic activity of GCNNF is mainly due to the higher surface area, appropriate bandgap, and fewer defects in GCNNF as compared to GCN. As an economical precursor (melamine) and harmless, facile, and template-free synthesis method with excellent performance both in supercapacitors and in photodegradation, GCNNF is a strong candidate for energy storage and environment protection applications. PMID:24354285

  14. Enhanced electrical and optical properties of room temperature deposited Aluminium doped Zinc Oxide (AZO) thin films by excimer laser annealing

    NASA Astrophysics Data System (ADS)

    El hamali, S. O.; Cranton, W. M.; Kalfagiannis, N.; Hou, X.; Ranson, R.; Koutsogeorgis, D. C.

    2016-05-01

    High quality transparent conductive oxides (TCOs) often require a high thermal budget fabrication process. In this study, Excimer Laser Annealing (ELA) at a wavelength of 248 nm has been explored as a processing mechanism to facilitate low thermal budget fabrication of high quality aluminium doped zinc oxide (AZO) thin films. 180 nm thick AZO films were prepared by radio frequency magnetron sputtering at room temperature on fused silica substrates. The effects of the applied RF power and the sputtering pressure on the outcome of ELA at different laser energy densities and number of pulses have been investigated. AZO films deposited with no intentional heating at 180 W, and at 2 mTorr of 0.2% oxygen in argon were selected as the optimum as-deposited films in this work, with a resistivity of 1×10-3 Ω.cm, and an average visible transmission of 85%. ELA was found to result in noticeably reduced resistivity of 5×10-4 Ω.cm, and enhancing the average visible transmission to 90% when AZO is processed with 5 pulses at 125 mJ/cm2. Therefore, the combination of RF magnetron sputtering and ELA, both low thermal budget and scalable techniques, can provide a viable fabrication route of high quality AZO films for use as transparent electrodes.

  15. Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties.

    PubMed

    Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

    2015-01-01

    Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells. PMID:25852401

  16. Nonlinear optical properties of bacteriorhodopsin

    NASA Astrophysics Data System (ADS)

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

    1993-04-01

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

  17. Two-Photon Optical Properties of AIE-active D-TPE-A Molecules: Aggregation Enhancement and Structure-Property Relationships

    NASA Astrophysics Data System (ADS)

    Zhang, Yilin; Li, Jie; Tang, Ben Zhong; Wong, Kam Sing

    We present an aggregation enhancement in two-photon-excited fluorescence (TPEF) of about two orders of magnitude in a series of novel non-centrosymmetric D- π-A molecules. Aggregation-induced emission characteristics are introduced into these D- π-A molecules via tetraphenylethylene (TPE), which is used as their π-bridge. Detailed analysis shows that the TPEF of these molecules are enhanced in aggregation environment with both fluorescence quantum efficiency and two-photon absorptivity concomitantly. The two-photon absorption (TPA) transition bands of these branched- or butterfly-configured molecules are similar to those in their linear absorption. The molecular TPA cross sections in aggregation environment reach around 50-130 GM, and peak within the available wavelength ranges of a Ti:Sapphire femtosecond oscillator. We also observe that two-photon absorptivity increases progressively with the addition of donor/acceptor moieties on the TPE backbone. This phenomenon is presumably attributed to the improved conjugation length and enhanced intramolecular charge transfer, hence better delocalization of π-electrons. For each compound, the aggregation enhancement in TPA may also offers clues of aggregation effect on the molecular electronic structure.

  18. 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.

  19. Optical Properties of Semiconductor Nanocrystals

    NASA Astrophysics Data System (ADS)

    Gaponenko, S. V.

    1998-10-01

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

  20. Enhancement in optical and structural properties of Zn0.85Mg0.15O nanorods over thin films synthesized by hydrothermal chemical treatment

    NASA Astrophysics Data System (ADS)

    Murkute, P.; Sehara, N.; Ghadi, H.; Pandey, S. K.; Maity, S.; Chakrabarti, S.

    2016-02-01

    We are reporting an enhancement in optical properties by changing the structure of Zn0.85Mg0.15O thin films through formation of crystalline hexagonal nanorods. Zn0.85Mg0.15O thin films were deposited on Si (100) substrate using dielectric sputter followed by annealing in oxygen ambient at temperatures of 700, 800 and 900° C for 10 seconds to reduce oxygen vacancies defects. Deposited thin film annealed at 900 °C (sample A) measured highest peak intensity and it was subjected to controlled the hydrothermal bath conditioning for forming hexagonal nanorods. Four samples were dipped in 2 different solutions with variable molar ratio of zinc nitrate hexahydrate and hexamethylentetramine for 2 and 3 hours, respectively. Samples processed in solution 1 (1:1) ratio for 2 and 3 hours were named B and C and those in solution 2 (2:1) were D and E, respectively. Photoluminescence measurement at 18K demonstrates exciton near-band-edge (NBE) emission peak at 3.61eV from Zn0.85Mg0.15O sample A whereas other samples exhibited slight blue shift along with bimodal peaks. The other peak observed at lower energy 3.43eV corresponds to transitions due to presence of ZnO phase in Zn0.85Mg0.15O. All samples compared to sample A exhibited more than 10 times increment in peak intensities with sample B producing the highest (~ 20 times). Nanorods formation was confirmed using crosssectional SEM imaging. X-ray diffraction measurements revealed that all Zn0.85Mg0.15O samples had (002) preferred crystal orientation with peak position at 34.7°. All nanorods samples measured lower reflectance compared to sample A, indicating high absorption in nanorods due to high scattering of light at the nanorods surface.

  1. 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)

  2. Enhancement of optical properties of hydrothermally synthesized TiO2/ZrO2 nanoparticles by Al, Ce Co-doping

    NASA Astrophysics Data System (ADS)

    Tomar, Laxmi J.; Bhatt, Piyush J.; Desai, Rahul K.; Chakrabarty, Bishwajit S.

    2015-06-01

    Al, Ce co-doped TiO2/ZrO2 (TZ) nano composites have been prepared by hydrothermal method. The structural and optical properties of the obtained samples were investigated by X -ray diffraction (XRD) and UV-Visible spectroscopy respectively. It has been found that the crystallite size of all the samples was distributed in the range 9.19 to 17.41 nm. The content of anatase phase varied in the range 48.71 to 100% depending on doping. The dopant produced lattice strain in material and it was found between 0.027 - 0.069. A clear shift of absorption edge for different dopant has been observed from UV-Visible absorption spectra. The change in optical bandgap, refractive index, absorption co efficient and optical conductivity was also evaluated from absorption spectra.

  3. Enhancement of optical properties of hydrothermally synthesized TiO{sub 2}/ZrO{sub 2} nanoparticles by Al, Ce Co-doping

    SciTech Connect

    Tomar, Laxmi J.; Bhatt, Piyush J. Desai, Rahul K.; Chakrabarty, Bishwajit S.

    2015-06-24

    Al, Ce co-doped TiO{sub 2}/ZrO{sub 2} (TZ) nano composites have been prepared by hydrothermal method. The structural and optical properties of the obtained samples were investigated by X –ray diffraction (XRD) and UV-Visible spectroscopy respectively. It has been found that the crystallite size of all the samples was distributed in the range 9.19 to 17.41 nm. The content of anatase phase varied in the range 48.71 to 100% depending on doping. The dopant produced lattice strain in material and it was found between 0.027 - 0.069. A clear shift of absorption edge for different dopant has been observed from UV-Visible absorption spectra. The change in optical bandgap, refractive index, absorption co efficient and optical conductivity was also evaluated from absorption spectra.

  4. Tailored synthesis of superparamagnetic gold nanoshells with tunable optical properties.

    SciTech Connect

    Zhang, Q.; Ge, J.; Goebl, J.; Hu, Y.; Sun, Y.; Yin, Y.; Center for Nanoscale Materials; Univ. of California at Riverside

    2010-05-04

    Multifunctional Au nanoshells with tunable optical properties and fast magnetic response have been fabricated through a sequence of sol-gel, surface-protected etching, and seed-mediated growth processes. The use of a porous silica layer enhances the uniformity of nanoshell growth, the reproducibility of the synthesis, and the structural and optical stability of the products.

  5. Optical Properties of Ferromagnetic Semiconductors

    NASA Astrophysics Data System (ADS)

    Burch, Kenneth

    2006-03-01

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

  6. 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].

  7. Plasmon-enhanced optical sensors: a review.

    PubMed

    Li, Ming; Cushing, Scott K; Wu, Nianqiang

    2015-01-21

    Surface plasmon resonance (SPR) has found extensive applications in chemi-sensors and biosensors. Plasmons play different roles in different types of optical sensors. SPR transduces a signal in a colorimetric sensor through shifts in the spectral position and intensity in response to external stimuli. SPR can also concentrate the incident electromagnetic field in a nanostructure, modulating fluorescence emission and enabling plasmon-enhanced fluorescence to be used for ultrasensitive detection. Furthermore, plasmons have been extensively used for amplifying a Raman signal in a surface-enhanced Raman scattering sensor. This paper presents a review of recent research progress in plasmon-enhanced optical sensing, giving emphasis on the physical basis of plasmon-enhanced sensors and how these principles guide the design of sensors. In particular, this paper discusses the design strategies for nanomaterials and nanostructures to plasmonically enhance optical sensing signals, also highlighting the applications of plasmon-enhanced optical sensors in healthcare, homeland security, food safety and environmental monitoring. PMID:25365823

  8. Plasmon-Enhanced Optical Sensors: A Review

    PubMed Central

    Li, Ming; Cushing, Scott K

    2014-01-01

    Surface plasmon resonance (SPR) has found extensive applications in chemi-sensors and biosensors. Plasmons play different roles in different types of optical sensors. SPR transduces a signal in a colorimetric sensor through shifts in the spectral position and intensity in response to external stimuli. SPR can also concentrate the incident electromagnetic field in a nanostructure, modulating fluorescence emission and enabling plasmon-enhanced fluorescence to be used for ultrasensitive detection. Furthermore, plasmons have been extensively used for amplifying a Raman signal in a surface-enhanced Raman scattering sensor. This paper presents a review of recent research progress in plasmon-enhanced optical sensing, giving an emphasis on the physical basis of plasmon-enhanced sensors and how these principles guide the design of sensors. In particular, this paper discusses the design strategies for nanomaterials and nanostructures to plasmonically enhance optical sensing signals, also highlighting the applications of plasmon-enhanced optical sensors in health care, homeland security, food safety and environmental monitoring. PMID:25365823

  9. Saccharide sensing molecules having enhanced fluorescent properties

    DOEpatents

    Satcher Jr., Joe H.; Lane, Stephen M.; Darrow, Christopher B.; Cary, Douglas R.; Tran, Joe Anh

    2004-01-06

    The present invention provides formulae for fluorescent compounds that have a number of properties which make them uniquely suited for use in sensors of analytes such as saccharides. The advantageous fluorescent properties include favorable excitation wavelengths, emission wavelengths, fluorescence lifetimes, and photostability. Additional advantageous properties include enhanced aqueous solubility, as well as temperature and pH sensitivity. The compound comprises an aryl or a substituted phenyl botonic acid that acts as a substrate recognition component, a fluorescence switch component, and a fluorophore. Fluorescent compounds are described that are excited at wavelengths greater than 400 nm and emit at wavelengths greater than 450 nm, which is advantageous for optical transmission through skin. The fluorophore is typically selected from transition metal-ligand complexes and thiazine, oxazine, oxazone, or oxazine-one as well as anthracene compounds. The fluorescent compound can be immobilized in a glucose permeable biocompatible polymer matrix that is implantable below the skin.

  10. Optical nanogap matrices for plasmonic enhancement applications

    NASA Astrophysics Data System (ADS)

    Bauman, Stephen J.; Debu, Desalegn T.; Hill, Avery M.; Novak, Eric C.; Natelson, Douglas; Herzog, Joseph B.

    2014-09-01

    Plasmonic structures can be used to enhance electromagnetic radiation, and nanoscale (<5 nm) gaps can increase this enhancement even further. Fabrication of these desired structures involves using a relatively new, previously developed self-aligned process to overcome typical electron beam lithography resolution limits. The resulting nanogap structures have been shown to exhibit enhanced optical emission. This technique enables the fabrication of a large-area two-dimensional matrix of such nanostructures which could prove useful for photovoltaics, plasmonically enhanced Raman spectroscopy, biosensing, and other optoelectronic applications. Computational electromagnetic simulations of the structures will prove useful for predicting behavior upon interaction with light and for experimental comparison.

  11. 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.

  12. 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.

  13. 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.

  14. Optical properties of fluids in microfabricated channels

    SciTech Connect

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

    1997-03-01

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

  15. In situ annealing enhancement of the optical properties and laser device performance of InAs quantum dots grown on Si substrates.

    PubMed

    Orchard, Jonathan R; Shutts, Samuel; Sobiesierski, Angela; Wu, Jiang; Tang, Mingchu; Chen, Siming; Jiang, Qi; Elliott, Stella; Beanland, Richard; Liu, Huiyun; Smowton, Peter M; Mowbray, David J

    2016-03-21

    The addition of elevated temperature steps (annealing) during the growth of InAs/GaAs quantum dot (QD) structures on Si substrates results in significant improvements in their structural and optical properties and laser device performance. This is shown to result from an increased efficacy of the dislocation filter layers (DFLs); reducing the density of dislocations that arise at the Si/III-V interface which reach the active region. The addition of two annealing steps gives a greater than three reduction in the room temperature threshold current of a 1.3 μm emitting QD laser on Si. The active region of structures grown on Si have a room temperature residual tensile strain of 0.17%, consistent with cool down from the growth temperature and the different Si and GaAs thermal expansion coefficients. This strain limits the amount of III-V material that can be grown before relaxation occurs. PMID:27136813

  16. Highly enhanced optical properties of indocyanine green/perfluorocarbon nanoemulsions for efficient lymph node mapping using near-infrared and magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Bae, Pan Kee; Jung, Juyeon; Chung, Bong Hyun

    2014-03-01

    The near-infrared (NIR) fluorescence probe has better tissue penetration and lower autofluorescence. Indocyanine green (ICG) is an NIR organic dye for extensive biological application, and it has been clinically approved for human medical imaging and diagnosis. However, application of this dye is limited by its numerous disadvantageous properties in aqueous solution, including its concentration-dependent aggregation, poor aqueous stability in vitro, and low quantum yield. Its use in molecular imaging probes is limited because it loses fluorescence after binding to nonspecific plasma proteins, leading to rapid elimination from the body with a half-life of 2 - 4 min. In this study, the multifunctional perfluorocarbon (PFC)/ICG nanoemulsions were investigated with the aim of overcoming these limitations. The PFC/ICG nanoemulsions as a new type of delivery vehicle for contrast agents have both NIR optical imaging and 19 F-MR imaging moieties. These nanoemulsions exhibited less aggregation, increased fluorescence intensity, long-term stability, and physicochemical stability against external light and temperature compared to free aqueous ICG. Also, the PFC/ICG bimodal nanoemulsions allow excellent detection of lymph nodes in vivo through NIR optical imaging and 19 F-MR imaging. This result showed the suitability of the proposed nanoemulsions for non-invasive lymph node mapping as they enable long-time detection of lymph nodes.

  17. 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.

  18. Enhanced optical constants of nanocrystalline yttrium oxide thin films

    SciTech Connect

    Ramana, C. V.; Mudavakkat, V. H.; Bharathi, K. Kamala; Atuchin, V. V.; Pokrovsky, L. D.; Kruchinin, V. N.

    2011-01-17

    Yttrium oxide (Y{sub 2}O{sub 3}) films with an average crystallite-size (L) ranging from 5 to 40 nm were grown by sputter-deposition onto Si(100) substrates. The optical properties of grown Y{sub 2}O{sub 3} films were evaluated using spectroscopic ellipsometry measurements. The size-effects were significant on the optical constants and their dispersion profiles of Y{sub 2}O{sub 3} films. A significant enhancement in the index of refraction (n) is observed in well-defined Y{sub 2}O{sub 3} nanocrystalline films compared to that of amorphous Y{sub 2}O{sub 3}. A direct, linear L-n relationship found for Y{sub 2}O{sub 3} films suggests that tuning optical properties for desired applications can be achieved by controlling the size at the nanoscale dimensions.

  19. Optical properties of liquids for fluidic optics.

    PubMed

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

    2013-05-10

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

  20. Preactivated thiomers: Permeation enhancing properties

    PubMed Central

    Wang, Xueqing; Iqbal, Javed; Rahmat, Deni; Bernkop-Schnürch, Andreas

    2012-01-01

    The study was aimed to prepare a series of poly(acrylic acid)-cysteine-2-mercaptonicotinic acid conjugates (preactivated thiomers) and to evaluate the influence of molecular mass or degree of preactivation with 2-mercaptonicotinic acid (2MNA) on their permeation enhancing properties. Preactivated thiomers with different molecular mass and different degree of preactivation were synthesized and categorized on the basis of their molecular mass and degree of preactivation as PAA100-Cys-2MNA (h), PAA250-Cys-2MNA (h), PAA450-Cys-2MNA (h), PAA450-Cys-2MNA (m) and PAA450-Cys-2MNA (l). In vitro permeation studies, the permeation enhancement ability for preactivated thiomers was ranked as PAA450-Cys-2MNA (h) > PAA250-Cys-2MNA (h) > PAA100-Cys-2MNA (h) on both Caco-2 cell monolayers and rat intestinal mucosa. Comparing the influence of degree of preactivation with 2MNA on permeation enhancement, the following order PAA450-Cys-2MNA (h) > PAA450-Cys-2MNA (m) ≈ PAA450-Cys-2MNA (l) on Caco-2 cell monolayers and PAA450-Cys-2MNA (m) > PAA450-Cys-2MNA (h) > PAA450-Cys-2MNA (l) on intestinal mucosa was observed. The Papp of sodium fluorescein was 5.08-fold improved on Caco-2 cell monolayers for PAA450-Cys-2MNA (h) and 2.46-fold improved on intestinal mucosa for PAA450-Cys-2MNA (m), respectively, in comparison to sodium fluorescein in buffer only. These results indicated that preactivated thiomers could be considered as a promising macromolecular permeation enhancing polymer for non-invasive drug administration. PMID:22960503

  1. Prediction of Apple Quality by Optical Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  2. Optical Properties of Black Silicon: An Analysis

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  3. Enhanced optical and electrical properties of boron-doped zinc-oxide thin films prepared by using the sol-gel dip-coating method

    NASA Astrophysics Data System (ADS)

    Lee, Sang-heon; Kim, MinSu; Jung, YuJin; Jung, Jae Hak; Kim, Soaram; Leem, Jae-Young; Kim, Howoon

    2013-11-01

    Undoped ZnO and B-dopoed ZnO (BZO) thin films with 0 to 2.5 at.% B were prepared by using sol-gel synthesis. Their optical and electrical properties and surface morphology were investigated using scanning electron microscopy, photoluminescence (PL), and van der Pauw Hall-effect measurements. All of the thin films were deposited appropriately onto quartz substrates; they exhibited a fibrous root morphology, with structures that changed in size with increasing B concentration. The PL spectra showed near-band-edge (NBE) emissions and deep-level emissions (DLE). The NBE emission and the DLE for the BZO thin films were more blue-shifted than those for the undoped ZnO thin film, and the blue shift increased the efficiency of the NBE emission of the BZO thin films. The Hall-effect data suggested that B doping also improved the electrical properties, such as the carrier concentration, Hall mobility, and resistivity, of the thin films. The resistivity and the Hall mobility decreased with increasing B concentration and were inversely proportional to the carrier concentration.

  4. Plasmon enhanced optical tweezers with gold-coated black silicon

    NASA Astrophysics Data System (ADS)

    Kotsifaki, D. G.; Kandyla, M.; Lagoudakis, P. G.

    2016-05-01

    Plasmonic optical tweezers are a ubiquitous tool for the precise manipulation of nanoparticles and biomolecules at low photon flux, while femtosecond-laser optical tweezers can probe the nonlinear optical properties of the trapped species with applications in biological diagnostics. In order to adopt plasmonic optical tweezers in real-world applications, it is essential to develop large-scale fabrication processes without compromising the trapping efficiency. Here, we develop a novel platform for continuous wave (CW) and femtosecond plasmonic optical tweezers, based on gold-coated black silicon. In contrast with traditional lithographic methods, the fabrication method relies on simple, single-step, maskless tabletop laser processing of silicon in water that facilitates scalability. Gold-coated black silicon supports repeatable trapping efficiencies comparable to the highest ones reported to date. From a more fundamental aspect, a plasmon-mediated efficiency enhancement is a resonant effect, and therefore, dependent on the wavelength of the trapping beam. Surprisingly, a wavelength characterization of plasmon-enhanced trapping efficiencies has evaded the literature. Here, we exploit the repeatability of the recorded trapping efficiency, offered by the gold-coated black silicon platform, and perform a wavelength-dependent characterization of the trapping process, revealing the resonant character of the trapping efficiency maxima. Gold-coated black silicon is a promising platform for large-scale parallel trapping applications that will broaden the range of optical manipulation in nanoengineering, biology, and the study of collective biophotonic effects.

  5. Plasmon enhanced optical tweezers with gold-coated black silicon.

    PubMed

    Kotsifaki, D G; Kandyla, M; Lagoudakis, P G

    2016-01-01

    Plasmonic optical tweezers are a ubiquitous tool for the precise manipulation of nanoparticles and biomolecules at low photon flux, while femtosecond-laser optical tweezers can probe the nonlinear optical properties of the trapped species with applications in biological diagnostics. In order to adopt plasmonic optical tweezers in real-world applications, it is essential to develop large-scale fabrication processes without compromising the trapping efficiency. Here, we develop a novel platform for continuous wave (CW) and femtosecond plasmonic optical tweezers, based on gold-coated black silicon. In contrast with traditional lithographic methods, the fabrication method relies on simple, single-step, maskless tabletop laser processing of silicon in water that facilitates scalability. Gold-coated black silicon supports repeatable trapping efficiencies comparable to the highest ones reported to date. From a more fundamental aspect, a plasmon-mediated efficiency enhancement is a resonant effect, and therefore, dependent on the wavelength of the trapping beam. Surprisingly, a wavelength characterization of plasmon-enhanced trapping efficiencies has evaded the literature. Here, we exploit the repeatability of the recorded trapping efficiency, offered by the gold-coated black silicon platform, and perform a wavelength-dependent characterization of the trapping process, revealing the resonant character of the trapping efficiency maxima. Gold-coated black silicon is a promising platform for large-scale parallel trapping applications that will broaden the range of optical manipulation in nanoengineering, biology, and the study of collective biophotonic effects. PMID:27195446

  6. Plasmon enhanced optical tweezers with gold-coated black silicon

    PubMed Central

    Kotsifaki, D. G.; Kandyla, M.; Lagoudakis, P. G.

    2016-01-01

    Plasmonic optical tweezers are a ubiquitous tool for the precise manipulation of nanoparticles and biomolecules at low photon flux, while femtosecond-laser optical tweezers can probe the nonlinear optical properties of the trapped species with applications in biological diagnostics. In order to adopt plasmonic optical tweezers in real-world applications, it is essential to develop large-scale fabrication processes without compromising the trapping efficiency. Here, we develop a novel platform for continuous wave (CW) and femtosecond plasmonic optical tweezers, based on gold-coated black silicon. In contrast with traditional lithographic methods, the fabrication method relies on simple, single-step, maskless tabletop laser processing of silicon in water that facilitates scalability. Gold-coated black silicon supports repeatable trapping efficiencies comparable to the highest ones reported to date. From a more fundamental aspect, a plasmon-mediated efficiency enhancement is a resonant effect, and therefore, dependent on the wavelength of the trapping beam. Surprisingly, a wavelength characterization of plasmon-enhanced trapping efficiencies has evaded the literature. Here, we exploit the repeatability of the recorded trapping efficiency, offered by the gold-coated black silicon platform, and perform a wavelength-dependent characterization of the trapping process, revealing the resonant character of the trapping efficiency maxima. Gold-coated black silicon is a promising platform for large-scale parallel trapping applications that will broaden the range of optical manipulation in nanoengineering, biology, and the study of collective biophotonic effects. PMID:27195446

  7. Enhanced quantum communication via optical refocusing

    NASA Astrophysics Data System (ADS)

    Lupo, Cosmo; Giovannetti, Vittorio; Pirandola, Stefano; Mancini, Stefano; Lloyd, Seth

    2011-07-01

    We consider the problem of quantum communication mediated by a passive optical refocusing system. The model captures the basic features of all those situations in which a signal is either refocused by a repeater for long-distance communication, or it is focused on a detector prior to the information decoding process. Introducing a general method for linear passive optical systems, we determine the conditions under which optical refocusing implies information transmission gain. Although the finite aperture of the repeater may cause loss of information, we show that the presence of the refocusing system can substantially enhance the rate of reliable communication with respect to the free-space propagation. We explicitly address the transferring of classical messages over the quantum channel, but the results can be easily extended to include the case of transferring quantum messages as well.

  8. Elegant Gaussian beams for enhanced optical manipulation

    SciTech Connect

    Alpmann, Christina Schöler, Christoph; Denz, Cornelia

    2015-06-15

    Generation of micro- and nanostructured complex light beams attains increasing impact in photonics and laser applications. In this contribution, we demonstrate the implementation and experimental realization of the relatively unknown, but highly versatile class of complex-valued Elegant Hermite- and Laguerre-Gaussian beams. These beams create higher trapping forces compared to standard Gaussian light fields due to their propagation changing properties. We demonstrate optical trapping and alignment of complex functional particles as nanocontainers with standard and Elegant Gaussian light beams. Elegant Gaussian beams will inspire manifold applications in optical manipulation, direct laser writing, or microscopy, where the design of the point-spread function is relevant.

  9. 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.

  10. Enhanced neutron imaging detector using optical processing

    SciTech Connect

    Hutchinson, D.P.; McElhaney, S.A.

    1992-08-01

    Existing neutron imaging detectors have limited count rates due to inherent property and electronic limitations. The popular multiwire proportional counter is qualified by gas recombination to a count rate of less than 10{sup 5} n/s over the entire array and the neutron Anger camera, even though improved with new fiber optic encoding methods, can only achieve 10{sup 6} cps over a limited array. We present a preliminary design for a new type of neutron imaging detector with a resolution of 2--5 mm and a count rate capability of 10{sup 6} cps pixel element. We propose to combine optical and electronic processing to economically increase the throughput of advanced detector systems while simplifying computing requirements. By placing a scintillator screen ahead of an optical image processor followed by a detector array, a high throughput imaging detector may be constructed.

  11. Enhanced Faraday effect and its application to optical communication.

    PubMed

    Bomke, H A; Harmatz, M

    1977-03-01

    This paper shows that the enhanced Faraday effect of optical resonance lines can be applied to optical communication. A secure optical communication system was designed and successfully tested. It used the integrated enhanced Faraday effect at low fields to produce polarization modulation and the high dispersion of the enhanced effect at high fields to scramble and unscramble the transmitted messages. PMID:20168574

  12. Optical Properties of Nanosatellite Hardware

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  13. Skin optical clearing enhancement with penetration enhancer azone using spectroscopy and optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Xu, Xiangqun; Zhu, Qiuhong

    2008-06-01

    In order to find a non-invasive way to improve the efficacy of skin optical clearing with topically applied optical clearing agents (OCA), we evaluated the effect of azone ® (epsilon-Laurocapram) as a chemical penetration enhancer on optical clearing of intact skin in vitro. Fresh porcine skin with topical application of glycerol (G) mixed with water-soluble azone (A) was investigated using near-infrared spectroscopy and optical coherence tomography (OCT). Light transmittance at 1276 nm increased by 41% and diffuse reflectance at 1066 nm decreased by 29% at 60 min after treatment with 40%G5%A on a spectrophotometer with an internal integrating sphere. 40% glycerol with addition of azone was a more effective optical clearing agent than 40% and 80% glycerol. 60%G/5%A led to a 2-fold increase in achievable OCT imaging depth and a 2.2-fold increase in light intensity reflected off the underneath needle surface after 60 minutes in the OCT in-depth reflectance profiles. In conclusion, skin optical clearing with the topical application of glycerol was markedly enhanced by water-soluble azone. Skin permeation enhancing effect of azone accounts probably for the skin clearing enhancement.

  14. Optical properties of graphite oxide and reduced graphite oxide

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  15. The properties of RE-TM magneto-optical films

    NASA Astrophysics Data System (ADS)

    Lee, Z. Y.; Miao, X. S.; Zhu, P.; Hu, Y. S.; Wan, D. F.; Dai, D. W.; Chen, S. B.; Lin, G. Q.

    1992-09-01

    In this paper, the magnetic, magneto-optical and galvonomagnetic properties, and their temperature dependence for LRE-TM SmCo, SmCoDy and HRE-TM TbFeCo magneto-optical films as high density recording media prepared by rf magnetron sputtering or evaporation are reported. By adding Dy to SmCo thin film, the SmCoDy thin film is more suitable for magneto-optical recording, its domain size being below 0.63 μm. The Kerr enhancement and corrosion protective effects of AIN and AlSiN for optimum design of the multi-layer structure of magneto-optical disk are described. The instruments of measuring the magneto-optical Kerr effect and magneto-optical recording domain characteristics of thin films are reviewed.

  16. Plasmonic nanogels with robustly tunable optical properties

    NASA Astrophysics Data System (ADS)

    Cong, Tao; Wani, Satvik N.; Zhou, Georo; Baszczuk, Elia; Sureshkumar, Radhakrishna

    2011-10-01

    Low viscosity fluids with tunable optical properties can be processed to manufacture thin film and interfaces for molecular detection, light trapping in photovoltaics and reconfigurable optofluidic devices. In this work, self-assembly in wormlike micelle solutions is used to uniformly distribute various metallic nanoparticles to produce stable suspensions with localized, multiple wavelength or broad-band optical properties. Their spectral response can be robustly modified by varying the species, concentration, size and/or shape of the nanoparticles. Structure, rheology and optical properties of these plasmonic nanogels as well as their potential applications to efficient photovoltaics design are discussed.

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

    NASA Astrophysics Data System (ADS)

    He, Geping; Fan, Huiqing; Wang, Zhiwei

    2014-12-01

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

  18. Optical coherence tomography image enhancement by using gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Ponce-de-Leon, Y. R.; Lopez-Rios, J. A.; Pichardo-Molina, J. L.; Alcalá Ochoa, N.

    2011-08-01

    Optical Coherence Tomography (OCT) is an imaging technique to get cross-sectional images with resolutions of a few microns and deep penetration in tissue of some millimeters. For many years OCT has been applied to analyze different human tissues like eyes, skin, teeth, urinary bladders, gastrointestinal, respiratory or genitourinary tracts and recently breast cancer tissues have been studied. Many of these tissues are composed specially of lipids and collagen, proteins which cause multiple light scattering (MLS) reducing significantly the optical depth and the contrast of OCT imaging. So, one of the big challenges of this technique is to acquire images with good contrast. Gold nanoparticles (NPs) exhibit interesting optical properties due to its plasmon resonance frequency. Optical absorbance is strong when gold NPs have dimension under 50 nm, but over this size optical scattering becomes dominant. In this work we show the preliminary results of the use of gold NPs as a contrast medium to enhance the OCT images quality. Our experimental results show which type of particles (morphology and size) present the best enhancement in the region of 1325 nm which corresponds to the central wavelength source excitation. All our experiments were carried out with a commercial OCT (thorlabs) system and our NPs were tested in water and gel phantoms.

  19. 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.

  20. Optical and Electrical Properties of Ar+ Implanted PET

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  1. Synthesizing Diacetylenes With Nonlinear Optical Properties

    NASA Technical Reports Server (NTRS)

    Mcmanus, Samuel P.; Frazier, Donald P.; Paley, Mark S.

    1993-01-01

    Diacetylene compounds being investigated to determine whether they have nonlinear optical properties making them useful for four-wave mixing, generation of third harmonics, phase conjugation, and like. Diacetylene monomers synthesized by sequences of chemical reactions. Monomers polymerized by ultraviolet light, forming potentially useful nonlinear optical materials.

  2. Optical amplification enhancement in photonic crystals

    SciTech Connect

    Sapienza, R.; Leonetti, M.; Froufe-Perez, L. S.; Galisteo-Lopez, J. F.; Lopez, C.; Conti, C.

    2011-02-15

    Improving and controlling the efficiency of a gain medium is one of the most challenging problems of laser research. By measuring the gain length in an opal-based photonic crystal doped with laser dye, we demonstrate that optical amplification is more than twenty-fold enhanced along the {Gamma}-K symmetry directions of the face-centered-cubic photonic crystal. These results are theoretically explained by directional variations of the density of states, providing a quantitative connection between density of the states and light amplification.

  3. Thermal optical nonlinearity enhanced by gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Souza, Rogério F.; Alencar, Márcio A. R. C.; Nascimento, César M.; da Silva, Monique G. A.; Meneghetti, Mario R.; Hickmann, Jandir M.

    2006-08-01

    We report on the observation of a large thermal nonlinearity of an organic material enhanced by the presence of gold nanoparticles. The studied system consisted of a colloid of castor oil and gold particles with average diameter of 10 nm, with filling factor of 4.0x10 -5. Z-scan measurements were performed for an excitation wavelength tuned at 810 nm in the CW regime. It was observed that this colloidal system presents a large thermal nonlinear refractive index, which was equal to -7.4x10 -8 cm2/W. This value is about 41 times larger than the n II of the host material. The thermo-optic coefficient of the colloid was also evaluated, and a large enhancement was observed in its value owing to the presence of the gold nanoparticles in the organic material.

  4. Optical properties of a hurricane

    NASA Astrophysics Data System (ADS)

    Kokhanovsky, Alexander A.; von Hoyningen-Huene, W.

    2004-01-01

    This paper is devoted to study of the distribution of the reflection function, spherical albedo, and optical thickness for a hurricane Erin, located in the western Atlantic (39.3°N, 60.4°W) on September 13th, 2001(16:21 UTC). The limitations and possibilities of using SeaWiFS imagery for remote sensing of hurricanes are discussed. In particular, it is found that the mode of the hurricane spherical albedo spatial distribution is equal to 0.86 and the transport optical thickness is in the range 4-10 on average for the central core of a hurricane. A simple analytical method to derive the hurricane optical thickness distribution is proposed.

  5. Cavity-Enhanced Optical Frequency Comb Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ye, Jun; Thorpe, Michael J.; Adler, Florian; Cossel, Kevin C.

    2009-06-01

    Cavity-enhanced optical frequency comb spectroscopy is a new technique that realizes simultaneously broad spectral coverage and high spectral resolution provided by an optical frequency comb as well as ultrahigh detection sensitivities enabled with a high-finesse optical cavity [1]. These powerful capabilities have been demonstrated in a series of experiments where real-time detection and identification of many different molecular states or species are achieved in a massively parallel fashion [2,3]. We will discuss the principle, technical requirements, and various implementations for this spectroscopic approach, as well as applications that include trace gas detections, human breath analysis, and characterization of cold and ultracold molecules [4,5,6]. References: [1] M. J. Thorpe, K. D. Moll, B. Safdi, and J. Ye, Science 311, 1595 (2006). [2] M. J. Thorpe, D. D. Hudson, K. D. Moll, J. Lasri, and J. Ye, Opt. Lett. 32, 307 (2007). [3] C. Gohle, B. Stein, A. Schliesser, T. Udem, and T. W. Hänsch, Phys. Rev. Lett. 99, 263902 (2007). [4] M. J. Thorpe, D. Balslev-Clausen, M. Kirchner, and J. Ye, Opt. Express. 16, 2387 (2008). [5] M. J. Thorpe and J. Ye, Appl. Phys. B 91, 397 (2008). [6] M. J. Thorpe, F. Adler, K. C. Cossel, M. H. G. de Miranda, and J. Ye, Chem. Phys. Lett. 468, 1 (2009).

  6. Fiber optical sensors for enhanced battery safety

    NASA Astrophysics Data System (ADS)

    Meyer, Jan; Nedjalkov, Antonio; Doering, Alexander; Angelmahr, Martin; Schade, Wolfgang

    2015-05-01

    Over the last years, battery safety becomes more and more important due to the wide spread of high-capacity lithium ion batteries applied in e.g. consumer electronics and electrical power storages for vehicles or stationary energy storage systems. However, for these types of batteries, malfunctions could be highly dangerous and all aspects of safety issues are not sufficiently considered, yet. Therefore, the improvement of the battery safety behavior is one of the most important issues discussed in actual research projects. In this paper the application of fiber optical sensors for enhanced battery safety is presented. The temperature is one of the most critical parameters indicating a failure of the cell, but even state-to-the-art battery management systems (BMS) are not able to monitor and interpret the distributed temperature field of a total battery storage system sufficiently. Furthermore, the volume expansion of the battery cell, which could be monitored by the strain on the cells' surfaces, is one additional parameter not considered up to now. Both parameters could be simultaneous monitored by fiber optical sensor arrays, consisting of discrete fiber Bragg grating (FBG) elements. The FBG sensors are directly attached on the surface of the cell, recording the temperature as well as the strain distribution highly accurate and close-meshed. Failures and malfunction such as overcharging, gassing, and thermal runaway can be early predicted and avoided to extend the battery lifetime and enhance the operational battery safety. Moreover, battery aging effects lead to variations in the volume change behavior which can be detected additionally. Hence, a battery fully equipped with fiber optical sensor arrays in combination with an appropriate BMS enables a safe and continuous utilization of the energy storage system even under harsh conditions like rapid charging.

  7. Optical properties of actinide and lanthanide ions

    SciTech Connect

    Hessler, J.P.; Carnall, W.T.

    1980-01-01

    This paper reviews some of the recent developments in this area of spectroscopy, emphasizing the optical properties of the tripositive lanthanide and actinide ions. In particular, the single ion properties of line positon, intensity, width, and fluorescence lifetime are discussed. 53 reference, 3 figures, 4 tables.

  8. 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

  9. 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.

  10. 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.

  11. 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

  12. Microstructure Related Properties of Optical Thin Films.

    NASA Astrophysics Data System (ADS)

    Wharton, John James, Jr.

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

  13. 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.

  14. 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.

  15. Enhancement of optical detectability with polarization

    NASA Astrophysics Data System (ADS)

    Egan, Walter G.

    1999-07-01

    Low detectability is a major consideration for combat platforms. Exposed surfaces are painted or coated black to minimize optical or near infrared detectability; this is a fallacy in regard to polarization. The percent polarization of a diffuse (non specular) surface is inversely proportional to the surface reflectance (also known as albedo). Thus a dark surface with a reflectance of 2% can have a percent polarization of approximately 100%. (The percent polarization is the ratio of the difference between two orthogonal polarized measurements ratioed to the sum multiplied by 100). Experimental measurements of diffuse surfaces with albedos between 2% and 90% show this inverse relationship to be obeyed from the ultraviolet to the near infrared. Imagery has been obtained on various aircraft coatings that verify the inverse relationship between surface albedo and percent polarization in the green, red and near infrared wavelength bands. The imagery was obtained in the three bands with the Kodak digital cameras, which downloaded on to CD ROMs. Imagery has also been obtained on laboratory samples that verify the inverse relationship between albedo and polarization. The conclusion is that very high polarization of a dark aircraft enhances the detectability such that it is easily recognized optically using polarization. This effect has not been recognized in signature reduction. Imagery will be presented and the inverse relationship between surface albedo and percent polarization will be demonstrated.

  16. Magnetically Responsive Nanostructures with Tunable Optical Properties.

    PubMed

    Wang, Mingsheng; Yin, Yadong

    2016-05-25

    Stimuli-responsive materials can sense specific environmental changes and adjust their physical properties in a predictable manner, making them highly desired components for designing novel sensors, intelligent systems, and adaptive structures. Magnetically responsive structures have unique advantages in applications, as external magnetic stimuli can be applied in a contactless manner and cause rapid and reversible responses. In this Perspective, we discuss our recent progress in the design and fabrication of nanostructured materials with various optical responses to externally applied magnetic fields. We demonstrate tuning of the optical properties by taking advantage of the magnetic fields' abilities to induce magnetic dipole-dipole interactions or control the orientation of the colloidal magnetic nanostructures. The design strategies are expected to be extendable to the fabrication of novel responsive materials with new optical effects and many other physical properties. PMID:27115174

  17. Enhanced optical properties of InAs/InAlGaAs/InP quantum dots grown by metal-organic chemical vapor deposition using a double-cap technique

    NASA Astrophysics Data System (ADS)

    Shi, Bei; Lau, Kei May

    2016-01-01

    The effects of a double-cap procedure on the optical properties of an InAs/InAlGaAs quantum dots (QDs) system grown by metal-organic chemical vapor deposition (MOCVD) have been investigated by atomic force microscopy (AFM) and room temperature photoluminescence (RT-PL) spectroscopy. An optimized QD growth condition has been achieved, with an areal density of 4.6×1010 cm-2. It was found that the thickness and lattice constant of the high temperature second cap layer (SCL) were crucial for improving the integrated PL intensity and line-width of the 1.55 μm emission from the InAs/InAlGaAs QD system grown on a semi-insulating InP (100) substrate. With fine-tuned SCL thickness and lattice constant, the optical performance of the five-stack QDs was enhanced. The improvements can be attributed to the smooth growth front, observed from the AFM images, and the well-balanced stress engineering.

  18. Enhancement of Optical Nonlinearities in Composite Media and Structures via Local Fields and Electromagnetic Coupling Effects

    NASA Technical Reports Server (NTRS)

    Smith, David D.

    2002-01-01

    This talk will review the linear and nonlinear optical properties of metal nanoparticles and dielectric microparticles, with an emphasis on local field effects, and whispering gallery modes (WGMs), as well as the conjunction of these two effects for enhanced Raman. In particular, enhanced optical properties that result from electromagnetic coupling effects will be discussed in the context of Mie scattering from concentric spheres and bispheres. Predictions of mode splitting and photonic bandgaps in micro-spheres will be presented and will be shown to be analogous to effects that occur in coupled resonator optical waveguides (CROW). Slow and fast light in SCISSOR / CROW configurations will also be discussed.

  19. Ovarian tissue characterization using bulk optical properties

    NASA Astrophysics Data System (ADS)

    Tavakoli, B.; Xu, Y.; Zhu, Q.

    2013-03-01

    Ovarian cancer, the deadliest of all gynecologic cancers, is not often found in its early stages due to few symptoms and no reliable screening test. Optical imaging has a great potential to improve the ovarian cancer detection and diagnosis. In this study we have characterized the bulk optical properties of 26 ex-vivo human ovaries using a Diffuse Optical Tomography system. The quantitative values indicated that, in the postmenopausal group, malignant ovaries showed significantly lower scattering coefficient than normal ones. The scattering parameter is largely related to the collagen content that has shown a strong correlation with the cancer development.

  20. Availability of thiazone as an enhancer for optical clearing of skin tissue in vitro

    NASA Astrophysics Data System (ADS)

    Jiang, Jingying; Chen, Wei; Wang, Ruikang K.; Xu, Kexin

    2008-02-01

    Dimethyl sulfoxside (DMSO) has been used as enhancer for tissue optical clearing technique. However, due to its potential toxicity and possible side effects, taking clearing effects and clinical availability into accounts, a new enhancer will be needed in order to facilitate practical application of tissue optical clearing technique to non-invasive light-based diagnostic and imaging technique. In this talk, it is our aim to introduce a new skin penetration promoter, thiazone, used in the fields of pharmaceutic industry, cosmetic, etc and investigate its availability as a new enhancer for tissue optical clearing technique. Firstly, we analyzed its structure, physical and chemical properties. And then we performed experimental investigation of the effect of DMSO and thiazone as enhancers mixed with polyethylene glycol (PEG) respectively on optical clearing of porcine skin tissue in vitro. Results of direct observation from camera reveal that thiazone has a higher penetration enhancing effect when compared with DMSO as an enhancer when porcine skin was topically impregnated by different mixed-solutions. Optical property parameters, obtained by using double integrating-spheres system and Inverse Adding-Doubling (IAD) method, showed that thiazone led to almost similar reduction in scattering to DMSO did during the same time period. Therefore, in terms of optical application and clinical safety, thiazone could be a better choice than DMSO as an enhancer for optical clearing of skin tissue.

  1. Optical properties of carbon microcoils

    SciTech Connect

    Hikita, Muneaki; Cao, Li E-mail: klafdi1@udayton.edu; Lafdi, Khalid E-mail: klafdi1@udayton.edu

    2014-01-27

    Carbon microcoils (CMCs) have emerged as versatile material artifacts for a variety of applications due to their helical and spiral structures. Embedded in matrix, CMCs have already been demonstrated for their potential tactile/proximity sensor application. In this study, CMCs were prepared using a conventional chemical vapor deposition method, and then were functionalized with octadecylamine. Upon photoexcitation, the functionalized CMCs exhibited photoluminescence in the visible region, which has never been found before. Similar to carbon based nanoparticles, the photoluminescence of CMCs was attributed to electron-hole radiative recombination after surface passivation. The results suggested that this kind of fluorescent functionalized CMCs might be used as a promising class of optical agents for biological applications.

  2. Optical Properties Of Turbidity Standards

    NASA Astrophysics Data System (ADS)

    Ronald, J.; Zaneveld, V.; Spinrad, Richard W.; Bartz, Robert

    1980-03-01

    Measurements of light scattering and light attenuation were made for suspensions of formazin and diatomaceous earth. Light scattering was measured for light of wavelength 632.8 nm at angles from 0.1° to 1.0° and for light of wavelengths 400, 500, 550, 600, 650, and 700 nm at 45°. Light attenuation was measured over a 25 cm pathlength for light of 660 nm. These measurements were made for suspensions which varied from 0 to 40 Jackson Turbidity Units of formazin and 0 to 40 mg/1 of diatomaceous earth. The results indicate the necessity for multiple optical measurements for determinations of turbidity of water. In addition the tables and curves presented may be used in the calibration of light scattering meters and transmissometers which are used for turbidity studies.

  3. Quantitative contrast-enhanced optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Winetraub, Yonatan; SoRelle, Elliott D.; Liba, Orly; de la Zerda, Adam

    2016-01-01

    We have developed a model to accurately quantify the signals produced by exogenous scattering agents used for contrast-enhanced Optical Coherence Tomography (OCT). This model predicts distinct concentration-dependent signal trends that arise from the underlying physics of OCT detection. Accordingly, we show that real scattering particles can be described as simplified ideal scatterers with modified scattering intensity and concentration. The relation between OCT signal and particle concentration is approximately linear at concentrations lower than 0.8 particle per imaging voxel. However, at higher concentrations, interference effects cause signal to increase with a square root dependence on the number of particles within a voxel. Finally, high particle concentrations cause enough light attenuation to saturate the detected signal. Predictions were validated by comparison with measured OCT signals from gold nanorods (GNRs) prepared in water at concentrations ranging over five orders of magnitude (50 fM to 5 nM). In addition, we validated that our model accurately predicts the signal responses of GNRs in highly heterogeneous scattering environments including whole blood and living animals. By enabling particle quantification, this work provides a valuable tool for current and future contrast-enhanced in vivo OCT studies. More generally, the model described herein may inform the interpretation of detected signals in modalities that rely on coherence-based detection or are susceptible to interference effects.

  4. 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. PMID:27451679

  5. Optical properties of KD*P modulators

    NASA Technical Reports Server (NTRS)

    West, E. A.; Bhatia, S. S.

    1990-01-01

    Longitudinal KD*P modulators are used in ground-based solar magnetographs to eliminate seeing effects. Although the modulators can be used as variable retarders, the optical properties when zero voltage is applied influences the performance on instruments requiring very accurate polarization measurements. Measurements at the Marshall Space Flight Center are discussed in terms of the optical properties of KD*P modulators when zero voltage is applied. The measurements can be used to predict the modulation characteristics of the devices and to determine the polarization accuracy that can be expected from the vector magnetograph.

  6. Single snapshot imaging of optical properties

    PubMed Central

    Vervandier, Jean; Gioux, Sylvain

    2013-01-01

    A novel acquisition and processing method that enables single snapshot wide field imaging of optical properties in the Spatial Frequency Domain (SFD) is described. This method makes use of a Fourier transform performed on a single image and processing in the frequency space to extract two spatial frequency images at once. The performance of the method is compared to the standard six image SFD acquisition method, assessed on tissue mimicking phantoms and in vivo. Overall both methods perform similarly in extracting optical properties. PMID:24409392

  7. 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.

  8. Nanometre-scale germanium photodetector enhanced by optical antennas

    NASA Astrophysics Data System (ADS)

    Tang, Liang

    2008-10-01

    The use of optics to make connections within and between electronic chips has been the subject of research for over 20 years because it could solve many of the problems experienced in electrical systems. A critical challenge for the convergence of optics and electronics is that the micrometre scale of optics is significantly larger than the nanometre scale of modern electronic devices. In the conversion from photons to electrons by photodetectors, this size incompatibility often leads to substantial penalties in power dissipation, area, latency and noise. A photodetector can be made smaller by using a subwavelength active region which, however, could result in very low responsivity because of the diffraction limit of the light. In our first approach to tackle this problem, we use a C-shaped nano-aperture antenna in a thin metal layer to enhance the photocurrent response of a subwavelength photodetector. The single C-shaped aperture, without any other supporting surface structures, can collect light from a large area and concentrate it into a tiny volume of semiconductor. We demonstrated the first antenna-enhanced photodetector at near-infrared wavelengths. In our second approach, we exploit the idea of a dipole antenna from radio waves, but at near infrared wavelengths (˜ 1.3 mum), to concentrate radiation into a nanometre-scale Ge photodetector. Despite the small antenna size (˜ 380 nm long) and the different properties of metals at such high frequencies (˜ 230 THz), the antenna has qualitatively similar behavior to the common radio-frequency half-wave (i.e., half wavelength long) Hertz dipole. It gives a relative enhancement of 20 times in the resulting photocurrent in the subwavelength Ge detector element, which has an active volume of 0.00072 mum 3, two orders of magnitude smaller than previously demonstrated detectors at such wavelengths. Photodetectors are one of the most critical components in optoelectronic integration, and decreasing their size may

  9. Directional field enhancement of dielectric nano optical disc antenna arrays

    NASA Astrophysics Data System (ADS)

    Wang, Ivan; Du, Y.

    2011-11-01

    This paper presents a discussion on the directive field enhancement of dielectric disc antenna arrays in optical band. The property of dielectric material is addressed, and field modes in a cylindrical resonator are discussed. It is identified that the fundamental mode of HE 11δ generates the far field with a higher directivity than other modes. More effective field enhancement in the radiation direction could be achieved by using multiple-disc antenna arrays. Simulation examples indicate that the directivity of a disc antenna array varies with the disc spacing. The maximum directivity is observed when the disc spacing is approximately equal to the half of the vacuum wavelength. The maximum directivity can be improved significantly when the disc number is increased.

  10. Optical properties of graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Karimi, Farhad; Knezevic, Irena

    We calculate the dielectric function and optical conductivity of ultra-narrow armchair graphene nanoribbons (AGNRs) and zigzag graphene nanoribbons (ZGNRs) by a self- consistent-field approach within a Markovian master-equation formalism (SCF-MMEF) coupled with full-wave electromagnetic equations. Based on third-nearest-neighbor tight-binding, with appropriate modifications for AGNRs and ZGNRs, we calculate electron dispersions and Bloch wave functions in excellent agreement with the local spin-density approximation (LSDA) results. A generalized Markovian master equation of the Lindblad form, which maintains the positivity of the density matrix, is derived to describe the interaction of the electronic system with an external electromagnetic field (to first order) and with a dissipative environment (to second order). Not only does the SCF-MMEF capture the interband electron-hole-pair generation, but it also accurately accounts for concurrent interband and intraband electron scattering with phonons and impurities. We employ the SCF-MMEF to calculate the dielectric function, complex conductivity, and loss function for both suspended and supported AGNRs and ZGNRs with different widths. Then, we obtain the plasmon dispersion and propagation length from the loss-function maximum. Support by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0008712.

  11. Optical Properties of Suspended and Substrate Graphene

    NASA Astrophysics Data System (ADS)

    Meera, V.

    2010-03-01

    Graphene, a two-dimensional material made purely of carbon atoms arranged in a hexagonal lattice has attracted the attention of scientific community since it was first produced in 2004. Due to the peculiarity in its band structure and various striking characteristics (eg. high electrical conductivity, mechanical robustness, large thermal conductivity, tunable carrier type and mobility etc.) this has become significant both technologically as well as for fundamental research. Both experimental and theoretical investigations have been taking place to study its various properties viz. transport, electronic, thermal and optical properties. In this work, optical properties of suspended monolayer-graphene and monolayer-graphene deposited on dielectric substrates are studied by calculating the optical quantities such as coefficient of reflection and reflected polarization analytically with the help of Maxwell's equations for the respective systems. Behavior of above mentioned optical quantities with respect to various parameters are studied to compare the two systems. This study can be used to obtain the conductivity tensor of graphene with its anisotropic behavior obtained from the azimuthal angle dependence of the optical quantities. The substrate-graphene is also interesting due to the observation of Brewster's phenomena with Brewster's angle varying with respect to the azimuthal angle (an oscillation with a period of 180 degrees).

  12. 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

  13. Nonlinear Optical Properties and Applications of Polydiacetylene

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  14. Optical properties of Apollo 12 moon samples.

    NASA Technical Reports Server (NTRS)

    O'Leary, B.; Briggs, F.

    1973-01-01

    We present the photometric phase function, color, normal albedo, polarimetric phase function, and spectrophotometry of the Apollo 12 soil. With a few minor exceptions, the optical properties of the Apollo 12 soil are very similar to those of the Apollo 11 soil and of lunar mare surfaces.

  15. Optical Properties of Bruised Apple Tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the optical properties of apple tissue, especially bruised tissue, can help us prevent or mitigate bruise occurrence during harvest and postharvest operations, and develop an effective method for detecting bruises during sorting and grading. This research was aimed at determining the o...

  16. Nonlinear optical properties and nonlinear optical probes of organic materials

    NASA Astrophysics Data System (ADS)

    Meredith, Gerald R.

    1992-02-01

    Nonlinear optical processes and electro-optical effects are expected to have increasing importance as the information age matures and photonics augment electronics in various high density and high bandwidth technologies. Whereas for electronics the emphasis is in construction of smaller device structures from a few parent materials, for organic materials the direction of materials research has been reversed. For some time it's been known that some molecular structures engender exceptionally large molecular nonlinear-polarization responses. If such molecules could be assembled in convenient, versatile, and reliable ways, the resulting materials would be very useful or even enabling in various photonics applications. The mature science and art of chemistry allows very good control over molecular composition and structure and, as will be illustrated in this talk, our knowledge of hyperpolarizability structure- property relationships is advancing rapidly. However, the science of fabrication and arrangement in molecular ensembles and polymers is rather primitive. Thus the goal to develop the appropriately structured materials for utilization in nonlinear and electro-optics has fostered the widespread use of nonlinear optical processes to probe the nature of supramolecular order and assembly. Examples of intrinsic and artificially assembled structures of crystals, molecular aggregates, polymeric orientational electrets and molecular mono- and multi-layer thin films will be shown. Nonlinear optical processes, primarily second-harmonic generation, provide unique probes of these structures, their assembly, and evolution.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Zheng, Zebo; Zhu, Liang; Zhao, Fuli

    2014-08-01

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

  19. Optical properties of thin graphitic nanopetal arrays

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  20. Quantum optical properties in plasmonic systems

    SciTech Connect

    Ooi, C. H. Raymond

    2015-04-24

    Plasmonic metallic particle (MP) can affect the optical properties of a quantum system (QS) in a remarkable way. We develop a general quantum nonlinear formalism with exact vectorial description for the scattered photons by the QS. The formalism enables us to study the variations of the dielectric function and photon spectrum of the QS with the particle distance between QS and MP, exciting laser direction, polarization and phase in the presence of surface plasmon resonance (SPR) in the MP. The quantum formalism also serves as a powerful tool for studying the effects of these parameters on the nonclassical properties of the scattered photons. The plasmonic effect of nanoparticles has promising possibilities as it provides a new way for manipulating quantum optical properties of light in nanophotonic systems.

  1. Optical Properties of Nanoporous Germanium Thin Films.

    PubMed

    Cavalcoli, Daniela; Impellizzeri, Giuliana; Romano, Lucia; Miritello, Maria; Grimaldi, Maria Grazia; Fraboni, Beatrice

    2015-08-12

    In the present article we report enhanced light absorption, tunable size-dependent blue shift, and efficient electron-hole pairs generation in Ge nanoporous films (np-Ge) grown on Si. The Ge films are grown by sputtering and molecular beam epitaxy; subsequently, the nanoporous structure is obtained by Ge+ self-implantation. We show, by surface photovoltage spectroscopy measurements, blue shift of the optical energy gap and strong signal enhancement effects in the np-Ge films. The blue shift is related to quantum confinement effects at the wall separating the pore in the structure, the signal enhancement to multiple light-scattering events, which result in enhanced absorption. All these characteristics are highly stable with time. These findings demonstrate that nanoporous Ge films can be very promising for photovoltaic applications. PMID:26177652

  2. Enhancing some functional properties of viscose fabric.

    PubMed

    Fahmy, H M; Eid, R A A; Hashem, S S; Amr, A

    2013-02-15

    To enhance the functional properties of viscose fabrics, Tinosan(®) CEL (TC), Ag, and TiO(2) nano-particles were incorporated as functional additives in different easy care finishing formulations alone and in admixtures. Results indicated that padding viscose fabrics in finishing bath containing 10 g/l TC and 60 g/l dimethyloldihydroxyethylene urea (DMDHEU) enhances some performance as well as antibacterial properties of the treated fabrics. Moreover, incorporation of Ag or TiO(2) nano-particles in the DMDHEU or DMDHEU/TC finishing baths enhances the functional properties of the treated samples such as antibacterial properties, UV-blocking properties, and/or self cleaning performance. Incorporation of poly (N-vinyl-2-pyrrolidone) in the aforementioned finishing formulations enhances these functional properties along with durability to wash. On the other hand, incorporation of Silicon(®)-SLH softener in finishing baths along with TC affects the performance and antibacterial properties of the treated fabrics. PMID:23399186

  3. 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

  4. Plasmonic nanoantennas for multipurpose particle manipulation and enhanced optical magnetism

    NASA Astrophysics Data System (ADS)

    Roxworthy, Brian James

    This dissertation explores the near-field enhancement and confinement properties of arrays of Au bowtie nanoantennas (BNAs) for plasmonic optical trapping. Using BNAs as a model system, the delicate interplay between optical and thermally induced forces in plasmonic nanotweezers is investigated over a broad parameter spacing including bowtie array spacing, adhesion layer materials, nanostructure orientation, composition of the fluid trapping media, optical polarization, input optical power, and trapped-particle diameter. Using theoretical modeling, it is shown that plasmon-induced convection drives experimentally observed phase-like behavior in plasmonic nanotweezers, and further, that this process can be used to engineer trapping tasks including dexterous single-particle trapping, trapping and manipulation of large self-assembled particle clusters using a single input beam, and particle sorting. The crucial role of an optically-absorptive substrate material for developing the requisite micron-per-second fluid flows for these phenomena is confirmed both theoretically and experimentally. In addition, this dissertation details the first experimental demonstration of plasmonic nanotweezers using an ultrafast, femtosecond (fs) pulsed input source. The fs pulses are shown to increase trapping performance in both the Rayleigh and Mie size regimes, where particle diameters are much smaller and greater than the incident illumination wavelength, respectively. This augmentation of forces enables plasmonic trapping of 80 nm to 1.2 mum diameter, metallic and dielectric particles with as little as 50 muW of input optical power. Moreover, the nonlinear optical response of trapped species can be probed during the trapping event, which opens doors for increased particle diagnostics in plasmonic optical trapping. An interesting particle fusing behavior is described whereby above a 60--75 muW power threshold, both metallic and dielectric particles spontaneously fuse to the BNA

  5. Purcell-enhanced optical spin readout of nitrogen-vacancy centers in diamond

    NASA Astrophysics Data System (ADS)

    Wolf, S. A.; Rosenberg, I.; Rapaport, R.; Bar-Gill, N.

    2015-12-01

    Nitrogen-vacancy (NV) color centers in diamond have emerged as promising quantum solid-state systems, with applications ranging from quantum information processing to magnetic sensing. One of the most useful properties of NVs is the ability to read their ground-state spin projection optically at room temperature. Using theoretical analysis of Purcell-enhanced NV optical coupling, we identify parameters for a significantly enhanced single-to-noise ratio (SNR) of the optical spin-state readout. We then demonstrate that a combined increase in spontaneous emission (through Purcell enhancement) and in optical excitation could significantly increase the readout SNR. Our combined analytical and numerical analysis, which is relevant for various optically active solid-state systems, differentiates between state-mixing processes and provides insights into the optimal light-matter coupling design.

  6. Enhanced optical gradient forces between coupled graphene sheets

    PubMed Central

    Xu, Xinbiao; Shi, Lei; Liu, Yang; Wang, Zheqi; Zhang, Xinliang

    2016-01-01

    Optical gradient forces between monolayer infinite-width graphene sheets as well as single-mode graphene nanoribbon pairs of graphene surface plasmons (GSPs) at mid-infrared frequencies were theoretically investigated. Although owing to the strongly enhanced optical field, the normalized optical force, fn, can reach 50 nN/μm/mW, which is the largest fn as we know, the propagation loss is also large. But we found that by changing the chemical potential of graphene, fn and the optical propagation loss can be balanced. The total optical force acted on the nanoribbon waveguides can thus enhance more than 1 order of magnitude than that in metallic surface plasmons (MSPs) waveguides with the same length and the loss can be lower. Owing to the enhanced optical force and the significant neff tuning by varying the chemical potential of graphene, we also propose an ultra-compact phase shifter. PMID:27338252

  7. Optical Relaxation Time Enhancement in Graphene-Passivated Metal Films

    PubMed Central

    Chugh, Sunny; Mehta, Ruchit; Man, Mengren; Chen, Zhihong

    2016-01-01

    Due to the small skin depth in metals at optical frequencies, their plasmonic response is strongly dictated by their surface properties. Copper (Cu) is one of the standard materials of choice for plasmonic applications, because of its high conductivity and CMOS compatibility. However, being a chemically active material, it gets easily oxidized when left in ambient environment, causing an inevitable degradation in its plasmonic resonance. Here, for the first time, we report a strong enhancement in the optical relaxation time in Cu by direct growth of few-layer graphene that is shown to act as an excellent passivation layer protecting Cu surface from any deterioration. Spectroscopic ellipsometry measurements reveal a 40–50% reduction in the total scattering rate in Cu itself, which is attributed to an improvement in its surface properties. We also study the impact of graphene quality and show that high quality graphene leads to an even larger improvement in electron scattering rate. These findings are expected to provide a big push towards graphene-protected Cu plasmonics. PMID:27461968

  8. Optical Relaxation Time Enhancement in Graphene-Passivated Metal Films

    NASA Astrophysics Data System (ADS)

    Chugh, Sunny; Mehta, Ruchit; Man, Mengren; Chen, Zhihong

    2016-07-01

    Due to the small skin depth in metals at optical frequencies, their plasmonic response is strongly dictated by their surface properties. Copper (Cu) is one of the standard materials of choice for plasmonic applications, because of its high conductivity and CMOS compatibility. However, being a chemically active material, it gets easily oxidized when left in ambient environment, causing an inevitable degradation in its plasmonic resonance. Here, for the first time, we report a strong enhancement in the optical relaxation time in Cu by direct growth of few-layer graphene that is shown to act as an excellent passivation layer protecting Cu surface from any deterioration. Spectroscopic ellipsometry measurements reveal a 40–50% reduction in the total scattering rate in Cu itself, which is attributed to an improvement in its surface properties. We also study the impact of graphene quality and show that high quality graphene leads to an even larger improvement in electron scattering rate. These findings are expected to provide a big push towards graphene-protected Cu plasmonics.

  9. A method which can enhance the optical-centering accuracy

    NASA Astrophysics Data System (ADS)

    Zhang, Xue-min; Zhang, Xue-jun; Dai, Yi-dan; Yu, Tao; Duan, Jia-you; Li, Hua

    2014-09-01

    Optical alignment machining is an effective method to ensure the co-axiality of optical system. The co-axiality accuracy is determined by optical-centering accuracy of single optical unit, which is determined by the rotating accuracy of lathe and the optical-centering judgment accuracy. When the rotating accuracy of 0.2um can be achieved, the leading error can be ignored. An axis-determination tool which is based on the principle of auto-collimation can be used to determine the only position of centerscope is designed. The only position is the position where the optical axis of centerscope is coincided with the rotating axis of the lathe. Also a new optical-centering judgment method is presented. A system which includes the axis-determination tool and the new optical-centering judgment method can enhance the optical-centering accuracy to 0.003mm.

  10. Optical Properties of Plasmonic Mirror-Image Nanoepsilon.

    PubMed

    Lin, Jia-Yu; Tsai, Chia-Yang; Lin, Pin-Tso; Hsu, Tse-En; Hsiao, Chi-Fan; Lee, Po-Tsung

    2016-12-01

    We propose a novel mirror-image nanoepsilon (MINE) structure to achieve highly localized and enhanced near field at its gap and systematically investigate its plasmonic behaviors. The MINE can be regarded as a combination of two fundamental plasmonic nanostructures: a nanorod dimer and nanoring. By adapting a nanoring surrounding a nanorod dimer structure, the nanorod is regarded as a bridge pulling the charges from the nanoring to the nanorod, which induces stronger plasmon coupling in the gap to boost local near-field enhancement. Two resonance peaks are identified as the symmetric and anti-symmetric modes according to the symmetries of the charge distributions on the ring and rod dimer in the MINE. The symmetric mode in the MINE structure is preferred because its charge distribution leads to stronger near-field enhancement with a concentrated distribution around the gap. In addition, we investigate the influence of geometry on the optical properties of MINE structures by performing experiments and simulations. These results indicate that the MINE possesses highly tunable optical properties and that significant near-field enhancement at the gap region and rod tips can be realized by the gap and lightning-rod effects. The results improve understanding of such complex systems, and it is expected to guide and facilitate the design of optimum MINE structures for various plasmonic applications. PMID:27405466

  11. Optical Properties of Plasmonic Mirror-Image Nanoepsilon

    NASA Astrophysics Data System (ADS)

    Lin, Jia-Yu; Tsai, Chia-Yang; Lin, Pin-Tso; Hsu, Tse-En; Hsiao, Chi-Fan; Lee, Po-Tsung

    2016-07-01

    We propose a novel mirror-image nanoepsilon (MINE) structure to achieve highly localized and enhanced near field at its gap and systematically investigate its plasmonic behaviors. The MINE can be regarded as a combination of two fundamental plasmonic nanostructures: a nanorod dimer and nanoring. By adapting a nanoring surrounding a nanorod dimer structure, the nanorod is regarded as a bridge pulling the charges from the nanoring to the nanorod, which induces stronger plasmon coupling in the gap to boost local near-field enhancement. Two resonance peaks are identified as the symmetric and anti-symmetric modes according to the symmetries of the charge distributions on the ring and rod dimer in the MINE. The symmetric mode in the MINE structure is preferred because its charge distribution leads to stronger near-field enhancement with a concentrated distribution around the gap. In addition, we investigate the influence of geometry on the optical properties of MINE structures by performing experiments and simulations. These results indicate that the MINE possesses highly tunable optical properties and that significant near-field enhancement at the gap region and rod tips can be realized by the gap and lightning-rod effects. The results improve understanding of such complex systems, and it is expected to guide and facilitate the design of optimum MINE structures for various plasmonic applications.

  12. 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

  13. 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.

  14. 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.

  15. Terahertz optical properties of the cornea

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  16. Multi-wavelength optical measurement to enhance thermal/optical analysis for carbonaceous aerosol

    NASA Astrophysics Data System (ADS)

    Chen, L.-W. A.; Chow, J. C.; Wang, X. L.; Robles, J. A.; Sumlin, B.; Lowenthal, D. H.; Zimmermann, R.; Watson, J. G.

    2014-09-01

    A thermal/optical carbon analyzer equipped with seven-wavelength light source/detector (405-980 nm) for monitoring spectral reflectance (R) and transmittance (T) of filter samples allows "thermal spectral analysis (TSA)" and wavelength (λ)-dependent organic carbon (OC)-elemental carbon (EC) measurements. Optical sensing is calibrated with transfer standards traceable to absolute R and T measurements and adjusted for loading effects to determine spectral light absorption (as absorption optical depth [τa, λ]) using diesel exhaust samples as a reference. Tests on ambient and source samples show OC and EC concentrations equivalent to those from conventional carbon analysis when based on the same wavelength (~635 nm) for pyrolysis adjustment. TSA provides additional information that evaluates black carbon (BC) and brown carbon (BrC) contributions and their optical properties in the near-IR to the near-UV parts of the solar spectrum. The enhanced carbon analyzer can add value to current aerosol monitoring programs and provide insight into more accurate OC and EC measurements for climate, visibility, or health studies.

  17. Multi-wavelength optical measurement to enhance thermal/optical analysis for carbonaceous aerosol

    NASA Astrophysics Data System (ADS)

    Chen, L.-W. A.; Chow, J. C.; Wang, X. L.; Robles, J. A.; Sumlin, B. J.; Lowenthal, D. H.; Zimmermann, R.; Watson, J. G.

    2015-01-01

    A thermal/optical carbon analyzer equipped with seven-wavelength light source/detector (405-980 nm) for monitoring spectral reflectance (R) and transmittance (T) of filter samples allowed "thermal spectral analysis (TSA)" and wavelength (λ)-dependent organic-carbon (OC)-elemental-carbon (EC) measurements. Optical sensing was calibrated with transfer standards traceable to absolute R and T measurements, adjusted for loading effects to report spectral light absorption (as absorption optical depth (τa, λ)), and verified using diesel exhaust samples. Tests on ambient and source samples show OC and EC concentrations equivalent to those from conventional carbon analysis when based on the same wavelength (~ 635 nm) for pyrolysis adjustment. TSA provides additional information that evaluates black-carbon (BC) and brown-carbon (BrC) contributions and their optical properties in the near infrared to the near ultraviolet parts of the solar spectrum. The enhanced carbon analyzer can add value to current aerosol monitoring programs and provide insight into more accurate OC and EC measurements for climate, visibility, or health studies.

  18. Optical and electrical properties of niobium carbide

    SciTech Connect

    Allison, C.Y.; Modine, F.A.; French, R.H.

    1987-02-15

    The optical and electrical properties were measured for single crystals of NbC/sub x/ for x = 0.98, 0.87, and 0.76, and for one hot-isostatically-pressed sample of NbC/sub 0.88/. Specular reflectance was measured between 0.025 and 11 eV, and ellipsometry measurements were made at 1.96 eV. By using the phase obtained from ellipsometry data to correct the Kramers-Kronig analyses of the reflectances, we were able to improve the accuracy of the resulting optical functions. For energies below 6.5 eV, there are differences in the reflectance and optical functions of the samples which are due to differences in x. We interpret the low-energy optical data in terms of intraband transitions, which allows us to calculate the dc conductivity as well as other electronic transport parameters. These parameters agree well with the electrical conductivities and the Hall coefficients obtained by the van der Pauw technique. The higher-energy optical data are interpreted in light of recent electronic-structure calculations, which suggest that most interband transitions occur near the square face of the Brillouin zone.

  19. 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.

  20. 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.

  1. Enhancing the mechanical properties of single-crystal CVD diamond.

    PubMed

    Liang, Qi; Yan, Chih-Shiue; Meng, Yufei; Lai, Joseph; Krasnicki, Szczesny; Mao, Ho-Kwang; Hemley, Russell J

    2009-09-01

    Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness (∼78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond. PMID:21832321

  2. Nonlinear quantum optical properties of graphene

    NASA Astrophysics Data System (ADS)

    Semnani, Behrooz; Hamed Majedi, Amir; Safavi-Naeini, Safieddin

    2016-03-01

    We present a semiclassical theory of the linear and nonlinear optical response of graphene. The emphasis is placed on the nonlinear optical response of graphene from the standpoint of the underlying chiral symmetry. The Bloch quasiparticles in the low-energy limit around the degeneracy points are dominantly chiral. It is shown that this chiral behavior in conjunction with scale invariance in graphene around the Dirac points results in the strong nonlinear optical response. Explicit expressions for the linear and nonlinear conductivity tensors are derived based on semiconductor Bloch equations (SBEs). The linear terms agree with the result of Kubo formulation. The three main additive mechanisms contribute in the nonlinear optical response of graphene: pure intraband, pure interband and the interplay between them. For each contribution, an explicit response function is derived. The Kerr-type nonlinearity of graphene is then numerically studied and it is demonstrated that the nonlinear refractive index of graphene can be tuned and enhanced by applying a gate voltage. It is also discussed that a strong Kerr nonlinearity can be achieved in a gated graphene monolayer. However, this nonlinearity is accompanied with a significant amount of absorption loss.

  3. Laser Scanning-Assisted Tip-Enhanced Optical Microscopy for Robust Optical Nanospectroscopy.

    PubMed

    Yano, Taka-Aki; Tsuchimoto, Yuta; Mochizuki, Masahito; Hayashi, Tomohiro; Hara, Masahiko

    2016-07-01

    Laser-scanning-assisted tip-enhanced optical microscopy was developed for robust optical nanospectroscopy. The laser-scanning system was utilized to automatically set and keep the center of a tight laser-focusing spot in the proximity of a metallic tip with around 10 nm precision. This enabled us to efficiently and stably induce plasmon-coupled field enhancement at the apex of the metallic probe tip. The laser-scanning technique was also applied to tracking and compensating the thermal drift of the metallic tip in the spot. This technique is usable for long-term tip-enhanced optical spectroscopy without any optical degradation. PMID:27412187

  4. 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

  5. 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.

  6. Coupling single quantum dots to plasmonic nanocones: optical properties.

    PubMed

    Meixner, Alfred J; Jäger, Regina; Jäger, Sebastian; Bräuer, Annika; Scherzinger, Kerstin; Fulmes, Julia; Krockhaus, Sven zur Oven; Gollmer, Dominik A; Kern, Dieter P; Fleischer, Monika

    2015-01-01

    Coupling a single quantum emitter, such as a fluorescent molecule or a quantum dot (QD), to a plasmonic nanostructure is an important issue in nano-optics and nano-spectroscopy, relevant for a wide range of applications, including tip-enhanced near-field optical microscopy, plasmon enhanced molecular sensing and spectroscopy, and nanophotonic amplifiers or nanolasers, to mention only a few. While the field enhancement of a sharp nanoantenna increasing the excitation rate of a very closely positioned single molecule or QD has been well investigated, the detailed physical mechanisms involved in the emission of a photon from such a system are, by far, less investigated. In one of our ongoing research projects, we try to address these issues by constructing and spectroscopically analysing geometrically simple hybrid heterostructures consisting of sharp gold cones with single quantum dots attached to the very tip apex. An important goal of this work is to tune the longitudinal plasmon resonance by adjusting the cones' geometry to the emission maximum of the core-shell CdSe/ZnS QDs at nominally 650 nm. Luminescence spectra of the bare cones, pure QDs and hybrid systems were distinguished successfully. In the next steps we will further investigate, experimentally and theoretically, the optical properties of the coupled systems in more detail, such as the fluorescence spectra, blinking statistics, and the current results on the fluorescence lifetimes, and compare them with uncoupled QDs to obtain a clearer picture of the radiative and non-radiative processes. PMID:26404008

  7. Optical Tissue Clearing to Enhance Imaging Performance for OCT

    NASA Astrophysics Data System (ADS)

    Wang, Ruikang K.; Tuchin, Valery V.

    Optical clearing technology for OCT needs is a growing field of investigations and biomedical applications. This chapter describes basic principles of optical clearing in enhancing the OCT imaging performances through biological tissue. We mainly focus on the use of biocompatible and osmotically active chemical agents to impregnate the tissue, leading to the reduction of tissue scattering, thus enhancing the OCT imaging performances. The mechanisms for such improvements, for example, imaging depth and contrast, were discussed, primarily through the experimental examples.

  8. Tailoring the Spectroscopic Properties of Semiconductor Nanowires via Surface-Plasmon-Based Optical Engineering

    PubMed Central

    2014-01-01

    Semiconductor nanowires, due to their unique electronic, optical, and chemical properties, are firmly placed at the forefront of nanotechnology research. The rich physics of semiconductor nanowire optics arises due to the enhanced light–matter interactions at the nanoscale and coupling of optical modes to electronic resonances. Furthermore, confinement of light can be taken to new extremes via coupling to the surface plasmon modes of metal nanostructures integrated with nanowires, leading to interesting physical phenomena. This Perspective will examine how the optical properties of semiconductor nanowires can be altered via their integration with highly confined plasmonic nanocavities that have resulted in properties such as orders of magnitude faster and more efficient light emission and lasing. The use of plasmonic nanocavities for tailored optical absorption will also be discussed in order to understand and engineer fundamental optical properties of these hybrid systems along with their potential for novel applications, which may not be possible with purely dielectric cavities. PMID:25396030

  9. Optical properties monitor: Experiment definition phase

    NASA Technical Reports Server (NTRS)

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

    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.

  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

    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.

  11. Designing Ligand-Enhanced Optical Absorption of Thiolated Gold Nanoclusters

    SciTech Connect

    Sementa, Luca; Barcaro, Giovanni; Dass, Amala; Stener, Mauro; Fortunelli, Alessandro

    2015-05-07

    The optical spectra of thiolated Au25(SR)18/Au23(SR)16 clusters with different R residues are investigated via TDDFT simulations. Significant enhancements in the optical region and effective electron delocalization are simultaneously achieved by tuning the ligands' steric hindrance and electronic conjugating features, producing a resonance phenomenon between the Au–S core motif and the ligand fragments.

  12. 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.

  13. 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.

  14. Time-delay concealment and complexity enhancement of an external-cavity laser through optical injection.

    PubMed

    Li, Nianqiang; Pan, Wei; Locquet, A; Citrin, D S

    2015-10-01

    The concealment of the time-delay signature (TDS) of chaotic external-cavity lasers is necessary to ensure the security of optical chaos-based cryptosystems. We show that this signature can be removed simply by optically injecting an external-cavity laser with a large linewidth-enhancement factor into a second, noninjection-locked, semiconductor laser. Concealment is ensured both in the amplitude and in the phase of the optical field, satisfying a sought-after property of optical chaos-based communications. Meanwhile, enhancement of the dynamical complexity, characterized by permutation entropy, coincides with strong TDS suppression over a wide range of parameters, the area for which depends sensitively on the linewidth-enhancement factor. PMID:26421545

  15. Nonlinear optical enhancement induced by synergistic effect of graphene nanosheets and CdS nanocrystals

    NASA Astrophysics Data System (ADS)

    Zhu, Baohua; Wang, Fangfang; Cao, Yawan; Wang, Chong; Wang, Ji; Gu, Yuzong

    2016-06-01

    CdS nanocrystals are attached on graphene nanosheets and their nonlinear optical properties are investigated by picosecond Z-scan technique at 532 nm. We found that synergistic effect between the graphene and CdS makes a major enhancement on the nonlinear optical absorption of graphene/CdS nanohybrid in comparison with cooperative effect, and the synergistic improvement is restricted by nonradiative defects in hybrid. The synergistic mechanism involving the local field theory and charge transfer evolution is proposed.

  16. Optical fiber solitons, their properties and uses

    NASA Astrophysics Data System (ADS)

    Haus, Hermann A.

    1993-07-01

    The history and mathematical formulation of the solitons are briefly reviewed. Solitons of the nonlinear Schroedinger equation are studied in greater detail because they describe nonlinear pulse propagation on dispersive optical fibers. The proposal by A. Hasegawa and the experiments of L.F. Mollenauer on long distance soliton propagation for use in repeaterless transoceanic fiber transmission cables are described. In 1986, limitations on the distance that can be spanned by a repeaterless link for a given bit-rate were shown to exist. It has been shown recently that by proper design these limitations can be overcome, so that newer transoceanic cable designs are likely to utilize solitons. The special properties of solitons make them particularly suited for all optical switching and logic operations. Some recent experiments with such switches are described.

  17. Femtosecond nonlinear optical properties of carbon nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2002-09-01

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

  18. 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

  19. Optical properties of relativistic plasma mirrors.

    PubMed

    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

  20. Quantum Plasmonics: Optical Properties and Tunability of Metallic Nanorods

    SciTech Connect

    Zuloaga, Jorge; Prodan, Emil; Nordlander, Peter

    2010-09-28

    The plasmon resonances in metallic nanorods are investigated using fully quantum mechanical time-dependent density functional theory. The computed optical absorption curves display well-defined longitudinal and transverse plasmon resonances whose energies depend on the aspect ratio of the rods, in excellent agreement with classical electromagnetic modeling. The field enhancements obtained from the quantum mechanical calculations, however, differ significantly from classical predictions for distances shorter than 0.5 nm from the nanoparticle surfaces. These deviations can be understood as arising from the nonlocal screening properties of the conduction electrons at the nanoparticle surface.

  1. Optical properties of silver nanocube surfaces obtained by silane immobilization

    NASA Astrophysics Data System (ADS)

    Merk, Virginia; Nerz, Alexander; Fredrich, Sebastian; Gernert, Ulrich; Selve, Sören; Kneipp, Janina

    2015-01-01

    Silver nanocubes were synthesized by the polyol method and immobilized on a surface in a simple approach using an aminopropyltriethoxysilane (APTES). The optical and structural properties of the polyvinylpyrrolidone (PVP) stabilized nanocubes were investigated in solution and on glass surfaces. The SERS enhancement factors at two excitation wavelengths for crystal violet were compared with electric fields arising in different nano¬particle configurations using finite-difference time-domain simulations. They are in agreement with the preferred face-to-face orientation in the nanoaggregates on the surfaces. The facile immobilization enables on-demand preparation and use of the nanocubes in real analytical applications.

  2. Theoretical study of nonlinear optical properties of oxocarbon derivatives

    NASA Astrophysics Data System (ADS)

    Junqueira, G. M. A.; Faria, M. S.; da Silva, A. M.; Dos Santos, H. F.

    In this work, first hyperpolarizability (β) and electronic spectra were obtained at ab initio and semiempirical levels of theory for mono- and bi-squarate derivatives. The results from our calculations suggest the investigated compounds as potential molecules for nonlinear optics (NLO). By means of the employed theoretical methodology, it was possible to identify structural aspects leading to enhancement of the NLO properties of the studied oxocarbons. Furthermore, a correlation between Hammett parameters of the substituents (∑σp) and ln (βtot) was established.

  3. Melamine sensing based on evanescent field enhanced optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Luo, Ji; Yao, Jun; Wang, Wei-min; Zhuang, Xu-ye; Ma, Wen-ying; Lin, Qiao

    2013-08-01

    Melamine is an insalubrious chemical, and has been frequently added into milk products illegally, to make the products more protein-rich. However, it can cause some various diseases, such as kidney stones and bladder cancer. In this paper, a novel optical fiber sensor with high sensitivity based on absorption of the evanescent field for melamine detection is successfully proposed and developed. Different concentrations of melamine changing from 0 to 10mg/mL have been detected using the micro/nano-sensing fiber decorated with silver nanoparticles cluster layer. As the concentration increases, the sensing fiber's output intensity gradually deceases and the absorption of the analyte becomes large. The concentration changing of 1mg/ml can cause the absorbance varying 0.664 and the limit of the melamine detectable concentration is 1ug/mL. Besides, the coupling properties between silver nanoparticles have also been analyzed by the FDTD method. Overall, this evanescent field enhanced optical fiber sensor has potential to be used in oligo-analyte detection and will promote the development of biomolecular and chemical sensing applications.

  4. Composite structures for the enhancement of nonlinear optical materials.

    PubMed

    Neeves, A E; Birnboim, M H

    1988-12-01

    Calculations of the nonlinear optical behavior are developed for model composites consisting of nanospheres with a metallic core and a nonlinear shell suspended in a nonlinear medium. The concept for the enhancement of optical phase conjugation from all these nonlinear regions is that the optical field can be concentrated both inside and in the neighborhood of the metallic core, aided by surface-mediated plasmon resonance. Calculations for gold cores and aluminum cores indicate that phase-conjugate reflectivity enhancements of 10(8) may be possible. PMID:19746133

  5. Few-Cycle and Cavity-Enhanced Optical Parametric Amplification

    NASA Astrophysics Data System (ADS)

    Siddiqui, Aleem Mohammad

    Optical parametric amplifiers have emerged as important optical sources by extending the properties of few-cycle laser sources, which exist only in materials with sufficiently large gain bandwidths, to wide array of spectral ranges. The work reported in this thesis relates to two areas for the continued development of optical parametric amplification based sources. First, we present a white light seeded, carrier-envelope stable, degenerately pumped OPA producing near tranform-limited sub 7 fs, 3 microJ pulses at the driver wavelength from a long pulse, non-CEP stable Ti:sapphire regenerative amplifier. Problems to the spectral phase jump at the driver wavelength, 800 nm, were avoided by using a near infrared OPA to produce white light continuum down to 800 nm where the spectral phase is smooth. Secondly, enhancement cavities are used in conjunction with parametric amplifiers resulting in a new technique entitled, cavity-enhanced optical parametric chirped-pulse amplification (C-OPCPA). C-OPCPA increases the capabilities of nonlinear crystals and can allow continued scaling of parametric amplifier systems to high repetition rate. This work contains the first theoretical and experimental investigation of C-OPCPA. Numerically, passive pump pulse shaping of the intracavity pump power is shown to enable octave spanning gain. Experimentally, a first proof-of-principle experiment demonstrates a 78 MHz C-OPCPA with more than 50% conversion with under 1 W of incident pump power. A comparison to a single pass system shows improvements in the C-OPCPA of orders of magnitude in conversion efficiency and 3 fold increase in phase matching bandwidth in 10 and 20 mm periodically poled lithium niobate phase matched for parametric amplification with 1030 nm pump wavelength and a 1550 nm signal wavelength. A Yb-fiber laser based CPA system producing up to 5 W of 500 fs pulses comprises the pump source, and a Er-fiber laser the signal. (Copies available exclusively from MIT Libraries

  6. Adhesion enhancement of indium tin oxide (ITO) coated quartz optical fibers

    NASA Astrophysics Data System (ADS)

    Wang, Yihua; Liu, Jing; Wu, Xu; Yang, Bin

    2014-07-01

    Transparent conductive indium tin oxide (ITO) film was prepared on optical fiber through a multi-step sol-gel process. The influence of annealing temperature on the adhesion of ITO coated optical fibers was studied. Different surface treatments were applied to improve the adhesion between ITO film and quartz optical fiber. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction analysis (XRD), UV-vis spectrophotometer and Avometer were used to characterize the morphology, crystal structure and photo-electric properties. A thermal shock test was used to evaluate the adhesion. The result shows that the adhesion between ITO film and quartz optical fiber can be strongly influenced by the annealing process, and optimal adhesion can be acquired when annealing temperature is 500 °C. Surface treatments of ultrasonic cleaning and the application of surface-active agent have effectively enhanced the adhesion and photo-electric properties of indium tin oxide film coated quartz optical fiber.

  7. Optical and thermal properties of doped semiconductor

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

  8. Electronic structure and optical properties of resin

    NASA Astrophysics Data System (ADS)

    Rao, Zhi-Fan; Zhou, Rong-Feng

    2013-03-01

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

  9. Optical properties of irregular interstellar grains

    NASA Technical Reports Server (NTRS)

    Perrin, J. M.; Lamy, P. L.

    1989-01-01

    In order to study the interaction of light with interstellar grains, the authors represent an irregular particle by a network of interacting dipoles whose polarizability is determined in a first approach by the Clausius-Mossoti relationship. Typically, 10,000 dipoles are considered. In the case of spherical particles, the results from Mie theory are fully recovered. The main interest of this method is to study with good accuracy the implications of surface roughness and/or inhomogeneities on optical properties in the infrared spectral range, particularly of the silicate emission features.

  10. Bioferroelectricity and optical properties of biological systems

    NASA Astrophysics Data System (ADS)

    Bystrov, Vladimir; Bystrova, Natalia

    2003-08-01

    A bioferroelectric approach to analysis of ferroelectric behavior of biological systems is presented. The optical properties of nerve fibers, biomembrane ion channels, and purple membrane films containing bacteriorhodopsin are analyzed. The features, influence of the proton subsystem and proton transfer on the hydrogen-bonded biomolecular structures are analyzed within the ferroelectric liquid-crystal model and possible biomedical applications discussed. The ferroelectric behavior of biological systems and the set of various bioferroelectric effects are considered within the limits of phenomenological theory of ferroelectrics. The nonlinear response to weak actions under conditions critical to human organism is one of specific features characterizing biological objects on molecular, cell and organism levels.

  11. Optical properties of graphene nanoflakes: Shape matters

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  12. Simulations of atomic resolution tip-enhanced optical microscopy

    NASA Astrophysics Data System (ADS)

    Downes, Andrew; Salter, Donald; Elfick, Alistair

    2006-11-01

    Optical techniques can access a wealth of information but traditionally their resolution has been restricted by the diffraction limit. Near-field techniques, which used nanoscale apertures or nanotip electric field enhancement, have succeeded in circumventing Abbe’s law. We show that atomic resolution is theoretically achievable for tip enhanced optical microscopy. Using finite element analysis of the electromagnetic field around a small radius metallic scanning probe microscopy tip, we modeled various tip radii and materials, and an aqueous environment as well as ambient air. For a 1 nm gold tip we predict a strong red shift, and surprisingly high values for the enhancement of the intensity of scattered light over 107. For this tip, we predict that 0.2 nm lateral resolution in optical imaging is achievable good enough to resolve individual atomic bonds. The promise of optical data at these spatial scales offers great potential for nanometrology and nanotechnology applications.

  13. 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

  14. Sensitivity of optical mass sensor enhanced by optomechanical coupling

    SciTech Connect

    He, Yong

    2015-03-23

    Optical mass sensors based on cavity optomechanics employ radiation pressure force to drive mechanical resonator whose mechanical susceptibility can be described by nonlinear optical transmission spectrum. In this paper, we present an optical mass sensor based on a two-cavity optomechanical system where the mechanical damping rate can be decreased by adjusting a pump power so that the mass sensitivity which depends on the mechanical quality factor has been enhanced greatly. Compared with that of an optical mass sensor based on single-cavity optomechanics, the mass sensitivity of the optical mass sensor is improved by three orders of magnitude. This is an approach to enhance the mass sensitivity by means of optomechanical coupling, which is suitable for all mass sensor based on cavity optomechanics. Finally, we illustrate the accurate measurement for the mass of a few chromosomes, which can be achieved based on the current experimental conditions.

  15. 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).

  16. Nonlinear optical properties of multipyrrole dyes

    PubMed Central

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

    2014-01-01

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

  17. Indium sulfide microflowers: Fabrication and optical properties

    SciTech Connect

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

    2009-10-15

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

  18. Nonlinear optical properties of lead sulfide nanocrystals in polymeric coatings

    NASA Astrophysics Data System (ADS)

    Lu, S. W.; Sohling, U.; Mennig, M.; Schmidt, H.

    2002-10-01

    Lead sulfide (PbS) nanocrystals with a particle size of 3.3 +/- 0.7 nm have been synthesized in a poly vinyl alcohol (PVA) coating on fused silica glass substrates. The coating was dip-coated from a PVA aqueous solution, in which PbS nanocrystals were precipitated and stabilized in the polymer matrix. Third-order nonlinear optical susceptibility of PbS nanocrystals is dependent on the wavelength with its maximum located near the first excitonic absorption peak resulting from the quantum confinement effect, according to the results of degenerate four wave-mixing. This suggests an enhancement of the nonlinear optical property by excitonic resonance. The maximum figure of merit, χ(3) /α, is as high as 2.91 × 10-12 esu m as measured at 595 nm.

  19. Aerosol optical properties of the free troposphere: Tropospheric backscatter climatology

    NASA Astrophysics Data System (ADS)

    Rosen, James M.

    1994-12-01

    A unique ensemble of aerosol sensors (backscattersondes, nephelometers and particle counters) has been assembled during the course of this research to obtain new measurements relating to the optical properties of aerosols in the atmosphere, especially in the free troposphere. A knowledge of the aerosol extinction-to-backscatter ratio has been greatly enhanced as a result of this project and the inference of representative values along with the range of variation is now possible. Agreement between the optical model results and actual measurements appears to be quite satisfactory. An initial climatology of aerosol backscatter in the free troposphere has been developed and is in general agreement with results and inferences from global remote sensing instruments. However, the data from remote sensors may indicate a larger influence of volcanic aerosols on the upper troposphere than actually exists. Further work with high resolution soundings is needed to fully resolve this issue.

  20. Optical Properties of Thin Film Molecular Mixtures

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  1. Optical vs. electronic enhancement of remote sensing imagery

    NASA Technical Reports Server (NTRS)

    Colwell, R. N.; Katibah, E. F.

    1976-01-01

    Basic aspects of remote sensing are considered and a description is provided of the methods which are employed in connection with the optical or electronic enhancement of remote sensing imagery. The advantages and limitations of various image enhancement methods and techniques are evaluated. It is pointed out that optical enhancement methods and techniques are currently superior to electronic ones with respect to spatial resolution and equipment cost considerations. Advantages of electronic procedures, on the other hand, are related to a greater flexibility regarding the presentation of the information as an aid for the interpretation by the image analyst.

  2. Enhanced thermal properties of nanodiamond nanofluids

    NASA Astrophysics Data System (ADS)

    Sundar, L. Syam; Singh, Manoj K.; Sousa, Antonio C. M.

    2016-01-01

    Nanodiamond (ND) particles dispersed in ethylene glycol/water mixtures have been reported for their thermal properties and potential heat transfer applications. Commercially available ultra-dispersed diamond soot was treated with sulfuric acid-nitric acids to form single ND particles - characterized by various techniques - then prepared ND nanofluids and then measured thermal conductivity and viscosity by experimentally. The enhanced thermal conductivity for 1.0% of ND/20:80, ND/40:60 and ND/60:40 nanofluids is 17.8%, 14.2% and 11.4%; enhanced viscosity is 2.74-times, 1.73-times and 1.92-times at temperature of 60 °C, respectively. The heat transfer benefits of ND nanofluids in laminar to turbulent flow have been analyzed theoretically by using thermal properties.

  3. Thermo-optical Properties of Nanofluids

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

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

  4. 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.

  5. 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.

  6. 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.

  7. Enhanced optical clearing of skin in vivo and optical coherence tomography in-depth imaging

    NASA Astrophysics Data System (ADS)

    Wen, Xiang; Jacques, Steven L.; Tuchin, Valery V.; Zhu, Dan

    2012-06-01

    The strong optical scattering of skin tissue makes it very difficult for optical coherence tomography (OCT) to achieve deep imaging in skin. Significant optical clearing of in vivo rat skin sites was achieved within 15 min by topical application of an optical clearing agent PEG-400, a chemical enhancer (thiazone or propanediol), and physical massage. Only when all three components were applied together could a 15 min treatment achieve a three fold increase in the OCT reflectance from a 300 μm depth and 31% enhancement in image depth Zthreshold.

  8. Nonlinear optical properties of methyl red under CW irradiation

    NASA Astrophysics Data System (ADS)

    Zheng, Yu; Ye, Qing; Wang, Chen; Wang, Jin; Deng, Zhichao; Mei, Jianchun; Zhou, Wenyuan; Zhang, Chunping; Tian, Jianguo

    2015-12-01

    Organic materials have wide potential application in nonlinear optical devices. The nonlinear optical (NLO) properties of methyl red (MR) doped polymethyl methacrylate (MR-PMMA) are investigated under CW laser irradiation at 473 nm, 532 nm and 632.8 nm, respectively. By combining Kramers-Kronig (K-K) relation and CW Z-scan technique, the effective refractive index n2 and the change of refractive index Δn are obtained under different scanning speed at 473 nm and 532 nm. Δn is positive at 473 nm, while Δn is negative at 532 nm. The experimental result is consistent with that of K-K relation. With the scanning speed decreasing, the NLO properties of MR-PMMA are enhanced. With different laser powers at 632.8 nm, MR-PMMA has only nonlinear absorption rather than nonlinear refraction. Meanwhile, the sample is investigated under pulse laser irradiation at 532 nm. Through the comparison of results of CW Z-scan and pulse Z-scan, the influence of the cumulative thermal effect on NLO properties of material is investigated. The results indicate that, under CW irradiation near the absorption peak wavelength, the cumulative thermal effect has great influence to the NLO properties of MR-PMMA.

  9. 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.

  10. 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.

  11. Birefringence, the Lost and Forgotten Optical Property

    NASA Astrophysics Data System (ADS)

    Nicholls, J.

    2009-05-01

    Petrologists and mineralogists could more effectively exploit birefringence and its derivative properties, retardation and interference color, to characterize minerals in thin section. Mineralogy texts and courses largely confine their treatments to the principal birefringences: γ - α, β - α, and γ - β in biaxial crystals and |ɛ - ω| in uniaxial crystals. Each section through a biaxial or uniaxial crystal has a birefringence and the birefringences range from zero to a maximum value for the substance under examination. The distribution of birefringence values on the indicatrix is not random; rather it follows a regular pattern. The pattern reveals itself in stereographic projection and it can be quantitatively depicted if the principal refractive indices are known. This pattern, when combined with the optical orientation of the crystal, places limits on the crystallographic orientation of the crystal plate in thin section. Birefringence can be used to estimate the composition of binary solid solutions displaying moderate to high interference colors if the optical orientation can be established. Computer color management techniques provide estimation of retardation values derived from interference colors to within a few nanometres in the range 250 to 1650 nanometres. These color management techniques can also be used to create charts and diagrams with retardation values as one variable and other mineral properties and compositions as the other variable. On such diagrams, interference colors can be painted, the color bands normal to the retardation axis like Michel-Levy charts.

  12. Accurate simulation of optical properties in dyes.

    PubMed

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

    2009-02-17

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

  13. Enhanced optical trapping via structured scattering

    NASA Astrophysics Data System (ADS)

    Taylor, Michael A.; Waleed, Muhammad; Stilgoe, Alexander B.; Rubinsztein-Dunlop, Halina; Bowen, Warwick P.

    2015-10-01

    Interferometry can completely redirect light, providing the potential for strong and controllable optical forces. However, small particles do not naturally act like interferometric beamsplitters and the optical scattering from them is not generally thought to allow efficient interference. Instead, optical trapping is typically achieved via deflection of the incident field. Here, we show that a suitably structured incident field can achieve beamsplitter-like interactions with scattering particles. The resulting trap offers order-of-magnitude higher stiffness than the usual Gaussian trap in one axis, even when constrained to phase-only structuring. We demonstrate trapping of 3.5-10.0 μm silica spheres, achieving a stiffness up to 27.5 ± 4.1 times higher than was possible using Gaussian traps as well as a two-orders-of-magnitude higher measured signal-to-noise ratio. These results are highly relevant to many applications, including cellular manipulation, fluid dynamics, micro-robotics and tests of fundamental physics.

  14. Double optical spring enhancement for gravitational-wave detectors

    NASA Astrophysics Data System (ADS)

    Rehbein, Henning; Müller-Ebhardt, Helge; Somiya, Kentaro; Danilishin, Stefan L.; Schnabel, Roman; Danzmann, Karsten; Chen, Yanbei

    2008-09-01

    Currently planned second-generation gravitational-wave laser interferometers such as Advanced LIGO exploit the extensively investigated signal-recycling technique. Candidate Advanced LIGO configurations are usually designed to have two resonances within the detection band, around which the sensitivity is enhanced: a stable optical resonance and an unstable optomechanical resonance—which is upshifted from the pendulum frequency due to the so-called optical-spring effect. As an alternative to a feedback control system, we propose an all-optical stabilization scheme, in which a second optical spring is employed, and the test mass is trapped by a stable ponderomotive potential well induced by two carrier light fields whose detunings have opposite signs. The double optical spring also brings additional flexibility in reshaping the noise spectral density and optimizing toward specific gravitational-wave sources. The presented scheme can be extended easily to a multi-optical-spring system that allows further optimization.

  15. Double optical spring enhancement for gravitational-wave detectors

    SciTech Connect

    Rehbein, Henning; Mueller-Ebhardt, Helge; Schnabel, Roman; Danzmann, Karsten; Somiya, Kentaro; Chen Yanbei; Danilishin, Stefan L.

    2008-09-15

    Currently planned second-generation gravitational-wave laser interferometers such as Advanced LIGO exploit the extensively investigated signal-recycling technique. Candidate Advanced LIGO configurations are usually designed to have two resonances within the detection band, around which the sensitivity is enhanced: a stable optical resonance and an unstable optomechanical resonance--which is upshifted from the pendulum frequency due to the so-called optical-spring effect. As an alternative to a feedback control system, we propose an all-optical stabilization scheme, in which a second optical spring is employed, and the test mass is trapped by a stable ponderomotive potential well induced by two carrier light fields whose detunings have opposite signs. The double optical spring also brings additional flexibility in reshaping the noise spectral density and optimizing toward specific gravitational-wave sources. The presented scheme can be extended easily to a multi-optical-spring system that allows further optimization.

  16. Transurethral fiber optics for in-vivo optical property determination: human and animal trials

    NASA Astrophysics Data System (ADS)

    Kim, Beop-Min; Ostermeyer, Martin R.; Jacques, Steven L.; Levy, David A.; Chakrabarti, Pradip; Torres, Jorge H.; von Eschenbach, Andrew C.; Rastegar, Sohi; Motamedi, Massoud

    1996-05-01

    A new optical probe which enables rapid and noninvasive measurement of the in vivo optical properties of tissues over a broad range of wavelengths is presented. The device was initially tested and calibrated in tissue-simulating phantoms whose optical properties were known to be similar to those of biological media. The technique was then applied in vivo to measure the optical properties of canine and human prostates.

  17. Nonlinear Optical Properties of Organic and Polymeric Thin Film Materials of Potential for Microgravity Processing Studies

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossin; Frazier, Donald O.; Paley, Mark S.; Penn, Benjamin; Witherow, William K.; Bank, Curtis; Shields, Angela; Hicks, Rosline; Ashley, Paul R.

    1996-01-01

    In this paper, we will take a closer look at the state of the art of polydiacetylene, and metal-free phthalocyanine films, in view of the microgravity impact on their optical properties, their nonlinear optical properties and their potential advantages for integrated optics. These materials have many attractive features with regard to their use in integrated optical circuits and optical switching. Thin films of these materials processed in microgravity environment show enhanced optical quality and better molecular alignment than those processed in unit gravity. Our studies of these materials indicate that microgravity can play a major role in integrated optics technology. Polydiacetylene films are produced by UV irradiation of monomer solution through an optical window. This novel technique of forming polydiacetylene thin films has been modified for constructing sophisticated micro-structure integrated optical patterns using a pre-programmed UV-Laser beam. Wave guiding through these thin films by the prism coupler technique has been demonstrated. The third order nonlinear parameters of these films have been evaluated. Metal-free phthalocyanine films of good optical quality are processed in our laboratories by vapor deposition technique. Initial studies on these films indicate that they have excellent chemical, laser, and environmental stability. They have large nonlinear optical parameters and show intrinsic optical bistability. This bistability is essential for optical logic gates and optical switching applications. Waveguiding and device making investigations of these materials are underway.

  18. Time-resolved chirp properties of semiconductor optical amplifiers in high-speed all-optical switches

    NASA Astrophysics Data System (ADS)

    Chen, Ligong; Lu, Rongguo; Zhang, Shangjian; Li, Jianfeng; Liu, Yong

    2013-03-01

    The chirp properties of semiconductor optical amplifiers in all-optical switches are numerically investigated using a field propagation model. The chirp dynamics in the blue-shift and red-shift sideband are analyzed under the injection of random optical pump pulses. We also analyze the impact of the blue-detuned filtering scheme that is used to eliminate the pattern effect and enhance the operating speed of the optical switching. The reason for overshoots in eye diagrams in the blue-detuned filtering scheme is explained. We find that overshoots result from the ultrafast blue chirp induced by carrier heating and two-phonon absorption. These results are very useful for semiconductor optical amplifier-based ultrafast all-optical signal processing.

  19. Fabrication, characterization, and optical properties of gold nanobowl submonolayer structures.

    PubMed

    Ye, Jian; Van Dorpe, Pol; Van Roy, Willem; Borghs, Gustaaf; Maes, Guido

    2009-02-01

    We report on a versatile method to fabricate hollow gold nanobowls and complex gold nanobowls (with a core) based on an ion milling and a vapor HF etching technique. Two different sized hollow gold nanobowls are fabricated by milling and etching submonolayers of gold nanoshells deposited on a substrate, and their sizes and morphologies are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Optical properties of hollow gold nanobowls with different sizes are investigated experimentally and theoretically, showing highly tunable plasmon resonance ranging from the visible to the near-infrared region. Additionally, finite difference time domain (FDTD) calculations show an enhanced localized electromagnetic field around hollow gold nanobowl structures, which indicates a potential application in surface-enhanced Raman scattering (SERS) spectroscopy for biomolecular detection. Finally, we demonstrate the fabrication of complex gold nanobowls with a gold nanoparticle core which offers the capability to create plasmon hybridized nanostructures. PMID:19125593

  20. Beyond optical enhancement due to embedded metal nanoparticles in thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Murthy Mopurisetty, Sundara; Bajaj, Mohit; Ganguly, Swaroop

    2016-03-01

    Metal nanoparticles (MNPs) inside the active layer of thin-film solar cells are considered promising for light trapping, but they have also engendered concerns over their adverse impact on transport properties. Contrary to expectations, coupled optical and electrical simulations indicate that a purely electrical effect due to MNPs might result in an enhancement of the cell performance in addition to the gain from optical (plasmonic) effects. This electrical enhancement strongly depends on the MNP/semiconductor barrier height. On the other hand, the anticipated degradation due to trap states and surface recombination at the MNP/semiconductor interface may in fact be negligible.

  1. 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.

  2. Electro-optic properties of organic nanotubes.

    PubMed

    Stoylov, Stoyl P; Stoilova-McPhie, Svetla

    2011-08-10

    In this review article the theoretical and experimental possibilities of applying EO-methods for estimation of the physico-chemical properties of the organic nanotubes (ONTs) are studied. The ONTs are highly organized nanostructures of strongly elongated, anysometric, and hollow cylinders with a size range of 1 nm to 10,000 nm, e.g. in aqueous solutions they could behave as colloid (disperse) particles. They have high interaction ability due to their extremely large curved, rolled-up external surfaces (bilayers of membrane walls) and unique properties because of their specific electric charge distribution and dynamics that make possible the functionalization of their surfaces. Thus they could template guestsubstances such as membrane proteins and protein complexes on the exterior surfaces and in the membrane. We performed our investigations for the case of ONT aqueous colloid suspension. Following our earlier proposition of the general expression for the electro-optic (EO) effect we derived equations for the evaluation of the electric properties of ONT particles such as mechanism of electric polarization and identification of their most important electric Dipole Moments (DM), permanent (pDM) and induced (iDMs). Further we recommend ways for the calculation of their magnitude and direction. Also we evaluated some geometrical properties such as length of the ONT particles and their polydispersity. The knowledge that we provided about the ONT properties may enable us to elucidate and predict their biological activity. Templating biological active ligands (such as membrane proteins and protein complexes) on the inner and outer surfaces as well as in the surface membrane creates their potential usefulness as carrier and deliverer of biopharmaceuticals in bio-nanodevices. The theoretical equations were compared with the experimental data for ONTs such as (lipid) LNT, Tobacco Mosaic Virus (TMV) and microtubules (MT). Comparison of EO methods with other methods used till

  3. Optically generated ultrasound for enhanced drug delivery

    DOEpatents

    Visuri, Steven R.; Campbell, Heather L.; Da Silva, Luiz

    2002-01-01

    High frequency acoustic waves, analogous to ultrasound, can enhance the delivery of therapeutic compounds into cells. The compounds delivered may be chemotherapeutic drugs, antibiotics, photodynamic drugs or gene therapies. The therapeutic compounds are administered systemically, or preferably locally to the targeted site. Local delivery can be accomplished through a needle, cannula, or through a variety of vascular catheters, depending on the location of routes of access. To enhance the systemic or local delivery of the therapeutic compounds, high frequency acoustic waves are generated locally near the target site, and preferably near the site of compound administration. The acoustic waves are produced via laser radiation interaction with an absorbing media and can be produced via thermoelastic expansion, thermodynamic vaporization, material ablation, or plasma formation. Acoustic waves have the effect of temporarily permeabilizing the membranes of local cells, increasing the diffusion of the therapeutic compound into the cells, allowing for decreased total body dosages, decreased side effects, and enabling new therapies.

  4. Size-Dependent Optical Properties of VO2 Nanoparticle Arrays

    SciTech Connect

    Lopez, R.; Feldman, Leonard C; Haglund, Jr, Richard F

    2004-01-01

    The size effects on the optical properties of vanadium dioxide nanoparticles in ordered arrays have been studied. Contrary to previous VO{sub 2} studies, we observe that the optical contrast between the semiconducting and metallic phases is dramatically enhanced in the visible region, presenting size-dependent optical resonances and size-dependent transition temperatures. The collective optical response as a function of temperature presents an enhanced scattering state during the evolving phase transition. The effects appear to arise because of the underlying VO{sub 2} mesoscale optical properties, the heterogeneous nucleation behind the phase transition, and the incoherent coupling between the nanoparticles undergoing an order-disorder-order transition. Calculations that support these interpretations are presented.

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

    SciTech Connect

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

    1997-07-01

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

  6. Optical properties of melting first-year Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Light, Bonnie; Perovich, Donald K.; Webster, Melinda A.; Polashenski, Christopher; Dadic, Ruzica

    2015-11-01

    The albedo and transmittance of melting, first-year Arctic sea ice were measured during two cruises of the Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment (ICESCAPE) project during the summers of 2010 and 2011. Spectral measurements were made for both bare and ponded ice types at a total of 19 ice stations in the Chukchi and Beaufort Seas. These data, along with irradiance profiles taken within boreholes, laboratory measurements of the optical properties of core samples, ice physical property observations, and radiative transfer model simulations are employed to describe representative optical properties for melting first-year Arctic sea ice. Ponded ice was found to transmit roughly 4.4 times more total energy into the ocean, relative to nearby bare ice. The ubiquitous surface-scattering layer and drained layer present on bare, melting sea ice are responsible for its relatively high albedo and relatively low transmittance. Light transmittance through ponded ice depends on the physical thickness of the ice and the magnitude of the scattering coefficient in the ice interior. Bare ice reflects nearly three-quarters of the incident sunlight, enhancing its resiliency to absorption by solar insolation. In contrast, ponded ice absorbs or transmits to the ocean more than three-quarters of the incident sunlight. Characterization of the heat balance of a summertime ice cover is largely dictated by its pond coverage, and light transmittance through ponded ice shows strong contrast between first-year and multiyear Arctic ice covers.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  8. Structural and optical properties of nanostructured nickel

    NASA Astrophysics Data System (ADS)

    Singh, J.; Pandey, J.; Gupta, R.; Kaurav, N.; Tripathi, J.

    2016-05-01

    Metal nanoparticles are attractive because of their special structure and better optical properties. Nickel nanoparticles (Ni-Np) have been synthesized successfully by thermal decomposition method in the presence of trioctyl phosphine (TOP) and oleylamine (OAm). The samples were characterized by X-ray diffraction (XRD), Zetapotential measurement and Fourier transforms infrared (FTIR) spectroscopy. The size of Ni nanoparticles can be readily tuned from 13.86 nm. As-synthesized Ni nanoparticles have hexagonal closed pack (hcp) cubic structure as characterized by power X-ray diffraction (XRD) prepared at 280°C. The possible formation mechanism has also been phenomenological proposed for as synthesized Ni-Np. The value of Zeta potential was found 12.25 mV.

  9. 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.

  10. 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.

  11. Enhancement of optical skin clearing efficacy using a microneedle roller.

    PubMed

    Yoon, Jinhee; Son, Taeyoon; Choi, Eung-Ho; Choi, Bernard; Nelson, J Stuart; Jung, Byungjo

    2008-01-01

    Light scattering in biological tissues can be reduced by using optical clearing agents. Various physical methods in conjunction with agents have been studied to enhance the optical clearing efficacy of skin for diagnostic and therapeutic applications. In this study, we propose a new physical method to enhance the optical clearing potential of topically applied glycerol. A microneedle roller is used to easily create numerous transdermal microchannels prior to glycerol application. The optical clearing efficacy of skin is quantitatively evaluated with the use of a modulation transfer function target placed underneath ex vivo porcine skin samples. From cross-polarized images acquired at various time points after glycerol application, we find that samples treated with the microneedle roller resulted in an approximately two-fold increase in contrast compared to control samples 30 min after glycerol application. In conclusion, our data suggest that the microneedle roller can be a good physical method to enhance transdermal delivery of optical clearing agents, and hence their optical clearing potential over large regions of skin. PMID:18465952

  12. Enhancement of optical skin clearing efficacy using a microneedle roller

    PubMed Central

    Yoon, Jinhee; Son, Taeyoon; Choi, Eung-ho; Choi, Bernard; Nelson, J. Stuart; Jung, Byungjo

    2009-01-01

    Light scattering in biological tissues can be reduced by using optical clearing agents. Various physical methods in conjunction with agents have been studied to enhance the optical clearing efficacy of skin for diagnostic and therapeutic applications. In this study, we propose a new physical method to enhance the optical clearing potential of topically applied glycerol. A microneedle roller is used to easily create numerous transdermal microchannels prior to glycerol application. The optical clearing efficacy of skin is quantitatively evaluated with the use of a modulation transfer function target placed underneath ex vivo porcine skin samples. From cross-polarized images acquired at various time points after glycerol application, we find that samples treated with the microneedle roller resulted in an approximately two-fold increase in contrast compared to control samples 30 min after glycerol application. In conclusion, our data suggest that the microneedle roller can be a good physical method to enhance transdermal delivery of optical clearing agents, and hence their optical clearing potential over large regions of skin. PMID:18465952

  13. Tip-enhanced near-field optical microscopy

    PubMed Central

    Mauser, Nina; Hartschuh, Achim

    2013-01-01

    Tip-enhanced near-field optical microscopy (TENOM) is a scanning probe technique capable of providing a broad range of spectroscopic information on single objects and structured surfaces at nanometer spatial resolution and with highest detection sensitivity. In this review, we first illustrate the physical principle of TENOM that utilizes the antenna function of a sharp probe to efficiently couple light to excitations on nanometer length scales. We then discuss the antenna-induced enhancement of different optical sample responses including Raman scattering, fluorescence, generation of photocurrent and electroluminescence. Different experimental realizations are presented and several recent examples that demonstrate the capabilities of the technique are reviewed. PMID:24100541

  14. Computational Electromagnetic Modeling of Optical Responses in Plasmonically Enhanced Nanoscale Devices Fabricated with Nanomasking Technique

    NASA Astrophysics Data System (ADS)

    Novak, Eric; Debu, Desalegn; Saylor, Cameron; Herzog, Joseph

    2015-03-01

    This work computationally explores plasmonic nanoscale devices fabricated with a recently developed nanomasking technique that is based on the self-aligned process. Computational electromagnetic modeling has determined enhancement factors and the plasmonic and optical properties of these structures. The nanomasking technique is a new process that is employed to overcome the resolution limits of traditional electron beam lithography and can also be used to increase resolution in photolithography fabrication as well. This technique can consistently produce accurate features with nanostructures and gaps smaller than 10 nm. These smaller dimensions can allow for increased and more localized plasmonically enhanced electric fields. These unique metal devices encompass tunable, enhanced plasmonic and optical properties that can be useful in a wide range of applications. Finite element methods are used to approximate the electromagnetic responses, giving the ability to alter the designs and dimensions in order to optimize the enhancement. Ultimately, we will fabricate devices and characterize the plasmonic properties with optical techniques, including dark-field spectroscopy, to confirm the properties with the goal of generating more efficient devices.

  15. Optical real-time defect-enhancement diagnostic system.

    PubMed

    Gaeta, C J; Mitchell, P V; Pepper, D M

    1992-12-15

    We have demonstrated an all-optical diagnostic system that enhances the observation of defects in periodic structures. This real-time technique employs a spatial light modulator as a smart-pixel array for information processing in the Fourier transform plane of a lens. The system also includes a phase-conjugate mirror for autoalignment and for correction of optical wave-front aberrations that are imparted on the object light by the smart-pixel processor and its associated optical train. PMID:19798320

  16. Analysis of nonlinear optical properties in donor–acceptor materials

    SciTech Connect

    Day, Paul N.; Pachter, Ruth; Nguyen, Kiet A.

    2014-05-14

    Time-dependent density functional theory has been used to calculate nonlinear optical (NLO) properties, including the first and second hyperpolarizabilities as well as the two-photon absorption cross-section, for the donor-acceptor molecules p-nitroaniline and dimethylamino nitrostilbene, and for respective materials attached to a gold dimer. The CAMB3LYP, B3LYP, PBE0, and PBE exchange-correlation functionals all had fair but variable performance when compared to higher-level theory and to experiment. The CAMB3LYP functional had the best performance on these compounds of the functionals tested. However, our comprehensive analysis has shown that quantitative prediction of hyperpolarizabilities is still a challenge, hampered by inadequate functionals, basis sets, and solvation models, requiring further experimental characterization. Attachment of the Au{sub 2}S group to molecules already known for their relatively large NLO properties was found to further enhance the response. While our calculations show a modest enhancement for the first hyperpolarizability, the enhancement of the second hyperpolarizability is predicted to be more than an order of magnitude.

  17. Enhancement of surface properties for coal beneficiation

    SciTech Connect

    Chander, S.; Aplan, F.F.

    1990-01-01

    The main objective of this research project is to study ways to modify surface properties of coal, pyrite and ash-forming mineral matter for beneficiation of fine coal. Since the differences in surface properties of coal and mineral matter are utilized in several oil based preparation technologies, such as: froth flotation, emulsion flotation, spherical agglomeration and liquid-liquid separation, another objective is to delineate the role of oil. The following studies are behind carried out to achieve the objectives: Investigation of the natural hydrophobicity of coal and pyrite; development and evaluation of enhanced coal hydrophobicity; development and evaluation of reagents xanthates which modulate the hydrophobicity of pyrite; and development and evaluation of emulsion processes and their underlying principles.

  18. 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.

  19. 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.

  20. Optical coherence tomography monitoring of enhanced skin optical clearing in rats in vivo.

    PubMed

    Genina, Elina A; Bashkatov, Alexey N; Kolesnikova, Ekaterina A; Basko, Marina V; Terentyuk, Georgy S; Tuchin, Valery V

    2014-02-01

    A comparative study of physical, chemical, and combined enhancement of transdermal transport of optical clearing agents (OCAs) is presented. As a physical enhancer of diffusivity, ultrasound (US) with a frequency 1 MHz and a power 1.1 W in the continuous mode was used, and dimethyl sulfoxide (DMSO) was used as a chemical enhancer. OCA (glycerol and polyethylene glycol-400 in equal proportion) was topically applied to the rat skin in vivo as alone or as together with the enhancers. Monitoring of skin optical clearing was implemented using an optical coherence tomography. The results have shown that the attenuation coefficient of intact skin dermis after the application of US-DMSO-OCA, US-OCA (both for 4 min), and DMSO-OCA (for 20 min) combinations decreased approximately by 31%, 19%, and 5%, respectively, while OCA alone did not induce a noticeable clearing effect for 20 min. Control skin sites with removed epidermis were used for modeling the upper limit of dermis optical clearing, i.e., maximal degree of optical clearing, by using the studied enhancers. They demonstrated that the attenuation coefficient decreases by 32%, 30%, 17%, and 16% at the action of US-DMSO-OCA, US-OCA, DMSO-OCA, and OCA, respectively. It can be concluded that US-DMSO-OCA combination only allowed reaching the upper limit of skin optical clearing. PMID:24105426

  1. Evaluation of skin optical clearing enhancement with Azone as a penetration enhancer

    NASA Astrophysics Data System (ADS)

    Xu, Xiangqun; Zhu, Qiuhong

    2007-11-01

    In order to find a non-invasive way to improve the efficacy of skin optical clearing with topically applied optical clearing agents (OCA), we evaluated the effect of Azone as a chemical penetration enhancer on optical clearing of intact skin in vitro. Fresh porcine skin with topical application of glycerol (G) mixed with various concentrations of water-soluble Azone (A w) or propylene glycol (PG) mixed with oil-soluble Azone (A o) was investigated. We measured changes in optical transmittance and diffuse reflectance of the skin under treatment with a near-infrared spectrophotometer. Light transmittance at 1276 nm increased by 37.3% and 41.1% at 60 min after the treatment in the cases with 40%PG5%A o and 40%G5%A w, respectively. Diffuse reflectance at 1066 nm decreased by 20.6% and 29.3% at 60 min after the treatment with 40%PG5%A o and 40%G5%A w, respectively. Forty percent glycerol or propylene glycol with the addition of Azone could achieve the same optical clearing effect as 80% glycerol. The results indicated that skin optical clearing with the topical application of glycerol and propylene glycol was markedly enhanced by both water-soluble and oil-soluble Azone. Skin penetration enhancing effect of Azone accounts probably for the skin clearing enhancement. In addition, Azone itself has shown optical clearing capability.

  2. Enhanced luminescence excitation via efficient optical energy transfer (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Aad, Roy; Nomenyo, Komla D.; Bercu, Bogdan; Couteau, Christophe; Sallet, Vincent; Rogers, David J.; Molinari, Michael; Lérondel, Gilles

    2015-10-01

    Luminescent nanoscale materials (LNMs) have received widespread interest in sensing and lighting applications due to their enhanced emissive properties. For sensing applications, LNMs offer improved sensitivity and fast response time which allow for lower limits of detection. Meanwhile, for lighting applications, LNMs, such as quantum dots, offer an improved internal quantum efficiency and controlled color rendering which allow for better lighting performances. Nevertheless, due to their nanometric dimensions, nanoscale materials suffer from extremely weak luminescence excitation (i.e. optical absorption) limiting their luminescence intensity, which in turn results in a downgrade in the limits of detection and external quantum efficiencies. Therefore, enhancing the luminescence excitation is a major issue for sensing and lighting applications. In this work, we report on a novel photonic approach to increase the luminescence excitation of nanoscale materials. Efficient luminescence excitation increase is achieved via a gain-assisted waveguided energy transfer (G-WET). The G-WET concept consists on placing nanoscale materials atop of a waveguiding active (i.e. luminescent) layer with optical gain. Efficient energy transfer is thus achieved by exciting the nanoscale material via the tail of the waveguided mode of the active layer emission. The G-WET concept is demonstrated on both a nanothin layer of fluorescent sensitive polymer and on CdSe/ZnS quantum dots coated on ZnO thin film, experimentally proving up to an 8-fold increase in the fluorescence of the polymer and a 3-fold increase in the luminescence of the CdSe/ZnS depending of the active layer emission regime (stimulated vs spontaneous emission). Furthermore, we will discuss on the extended G-WET concept which consists on coating nanoscale materials on a nanostructured active layer. The nanostructured active layer offers the necessary photonic modulation and a high specific surface which can presumably lead to

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  4. Optical and chemical properties of tholins

    NASA Astrophysics Data System (ADS)

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

    2008-10-01

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

  5. Optically Stimulated Luminescence Properties Of Natural Schist

    NASA Astrophysics Data System (ADS)

    Stefanaki, E. C.; Afouxenidis, D.; Polymeris, G. S.; Sakalis, A.; Tsirliganis, N. C.; Kitis, G.

    Schist is a common siliciclastic geological material that has been extensively used in buildings as brick, tile and roofing slates. Its use, especially in the Mediterranean sea is widespread through the centuries. There are various examples from the ancient Greece, such as monuments from Knossos, Karthaia, as well as from modern Greece, such as traditional houses, etc. Schist is a metamorphic crystalline rock composed largely of silicon minerals, such as quartz, muscovite mica and feldspars. The type and composition of schists, as well as, the concentration of each mineral depends strongly on the type and the origin of the schist. Its past and modern use makes it a suitable candidate form archaeological dating, as well as, for retrospective dosimetry purposes. In the present work a preliminary characterization of schist is performed in order to investigate if some basic properties required for dating applications can be found in this material. The preliminary study concerns the optical stability, the sensitization and linearity of the Infrared Stimulated Luminescence (IRSL) resulting from feldspars, as well as the post IR Blue Optically Stimulated Luminescence (post - IR Blue OSL) resulting mostly from quartz. The results indicate that both signals are rapidly bleached when the sample is exposed to sunlight. The dose response was found to be linear for radiation doses at least up to 75 Gy for the IRSL signal and at least up to 25 Gy in the case of post - IR Blue OSL. The use of a single aliquot measurement protocol, due to the lack of sensitisation, extends the latter dose response linearity region up to 75 Gy for the post - IR Blue OSL signal of schist. Finally, the application of the double single-aliquot regenerative-dose protocol to schist was investigated, in order to recover,successfully, the equivalent dose in 4 - 11 μm grains of the compound.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  7. Enhancement of the bentonite sorption properties.

    PubMed

    Mockovciaková, Annamária; Orolínová, Zuzana; Skvarla, Jirí

    2010-08-15

    The almost monomineral fraction of bentonite rock-montmorillonite was modified by magnetic particles to enhance its sorption properties. The method of clay modification consists in the precipitation of magnetic nanoparticles, often used in preparing of ferrofluids, on the surface of clay. The influence of the synthesis temperature (20 and 85 degrees C) and the weight ratio of bentonite/iron oxides (1:1 and 5:1) on the composite materials properties were investigated. The obtained materials were characterized by the X-ray diffraction method and Mössbauer spectroscopy. Changes in the surface and pore properties of the magnetic composites were studied by the low nitrogen adsorption method and the electrokinetic measurements. The natural bentonite and magnetic composites were used in sorption experiments. The sorption of toxic metals (zinc, cadmium and nickel) from the model solutions was well described by the linearized Langmuir and Freundlich sorption model. The results show that the magnetic bentonite is better sorbent than the unmodified bentonite if the initial concentration of studied metals is very low. PMID:20435410

  8. Nonreciprocal optical properties in resonant hybrid photonic crystals

    NASA Astrophysics Data System (ADS)

    D'Andrea, A.; Tomassini, N.

    2016-07-01

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

  9. Light Localization and Magneto-Optic Enhancement in Ni Antidot Arrays.

    PubMed

    Rollinger, Markus; Thielen, Philip; Melander, Emil; Östman, Erik; Kapaklis, Vassilios; Obry, Björn; Cinchetti, Mirko; García-Martín, Antonio; Aeschlimann, Martin; Papaioannou, Evangelos Th

    2016-04-13

    We reveal an explicit strategy to design the magneto-optic response of a magneto-plasmonic crystal by correlating near- and far-fields effects. We use photoemission electron microscopy to map the spatial distribution of the electric near-field on a nanopatterned magnetic surface that supports plasmon polaritons. By using different photon energies and polarization states of the incident light we reveal that the electric near-field is either concentrated in spots forming a hexagonal lattice with the same symmetry as the Ni nanopattern or in stripes oriented along the Γ-K direction of the lattice and perpendicular to the polarization direction. We show that the polarization-dependent near-field enhancement on the patterned surface is directly correlated to both the excitation of surface plasmon polaritons on the patterned surface as well as the enhancement of the polar magneto-optical Kerr effect. We obtain a relationship between the size of the enhanced magneto-optical behavior and the polarization and wavelength of optical excitation. The engineering of the magneto-optic response based on the plasmon-induced modification of the optical properties introduces the concept of a magneto-plasmonic meta-structure. PMID:27018661

  10. Enhanced electrochromic properties of a polypyrrole-indigo carmine-gold nanoparticles nanocomposite.

    PubMed

    Loguercio, L F; Alves, C C; Thesing, A; Ferreira, J

    2015-01-14

    An indigo carmine doped polypyrrole embedded with gold nanoparticles nanocomposite (PPy-IC-Aunanop) was synthesized by in situ electrochemical polymerization of polypyrrole in the presence of HAuCl4. The nanocomposite was characterized by in situ spectroelectrochemical experiments to study the effect of embedded gold nanoparticles on the electrochromic properties of the material. The results show the formation of a nanocomposite presenting enhanced electrochromic and optical properties, higher electroactivity and 10% lower band-gap energies. The PPy-IC-Aunanop presented a two-fold increase in optical contrast when compared to PPy-IC, in addition to better optical stability. PMID:25418577

  11. MBE growth and magneto-optic properties of magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Falco, Charles M.; Engel, Brad N.

    Recent interest in the magnetic and magneto-optic properties of transition metal/transition metal multilayers has been stimulated by the discovery of perpendicular magnetism in particular systems such as Co/Pd and Co/Pt. Due to their favorable magneto-optic wavelength dependence and enhanced corrosion resistance, these materials show promise as future data storage media. However, partially due to the large variety of thin-film deposition methods and growth conditions, it has been difficult to obtain a clear understanding of the mechanisms of magnetic anisotropy in these systems. In order to create controlled and well characterized model systems, we have grown a series of epitaxial Co/Pd superlattices oriented along the three high-symmetry crystal directions [001], [110], and [111] on single-crystal GaAs substrates by molecular beam epitaxy [MBE]. Simultaneously, we have deposited polycrystalline Co/Pd multilayers on Si substrates mounted alongside the GaAs for direct comparisons of epitaxial and non-epitaxial films produced under identical conditions. The structural properties of these multilayers were determined by low-and reflection high-energy electron diffraction (LEED and RHEED), low- and high-angle X-ray diffraction, and scanning tunneling microscopy (STM). The dependence of the uniaxial magnetic anisotropy energy on the Co thickness in these superlattices showed significant systematic differences for each of the three crystal orientations. A review of our work on the structural influences responsible for these differences is presented.

  12. Gain-enhanced optical cooling in cavity optomechanics

    NASA Astrophysics Data System (ADS)

    Ge, Li; Faez, Sanli; Marquardt, Florian; Tureci, Hakan

    2013-03-01

    We study the optical cooling of the mechanical motion of the resonator mirror in a cavity-optomechanical system that contains an optical gain medium. We find that the optical damping caused by radiation pressure force is vanishingly small if the active medium is pumped incoherently above its lasing threshold. In addition, we find that the spontaneous emission of the active medium always tends to increase the final effective temperature of the mechanical motion. In the presence of an additional seeding signal, i.e. a coherent drive of fixed frequency within the width of the gain curve however, we find that the cooling rate can be enhanced significantly with respect to that of a passive cavity. We attribute this effect to a reduced effective optical damping in the presence of incoherent pumping.

  13. Optical Klystron Enhancement to SASE X-ray FELs

    SciTech Connect

    Ding, Yuantao; Emma, Paul; Huang, Zhirong; Kumar, Vinit

    2006-04-07

    The optical klystron enhancement to self-amplified spontaneous emission (SASE) free electron lasers (FELs) is studied in theory and in simulations. In contrast to a seeded FEL, the optical klystron gain in a SASE FEL is not sensitive to any phase mismatch between the radiation and the microbunched electron beam. The FEL performance with the addition of four optical klystrons located at the undulator long breaks in the Linac Coherent Light Source (LCLS) shows significant improvement if the uncorrelated energy spread at the undulator entrance can be controlled to a very small level. In addition, FEL saturation at shorter x-ray wavelengths (around 1.0 A) within the LCLS undulator length becomes possible. We also discuss the application of the optical klystron in a compact x-ray FEL design that employs relatively low electron beam energy together with a shorter-period undulator.

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

    SciTech Connect

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

    2012-04-01

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

  15. Crystal ion slicing of optical oxides and plasmon-enhanced optical applications

    NASA Astrophysics Data System (ADS)

    Roth, Ryan M.

    The past three decades have been witness to rapid growth in the microelectronics and optoelectronic industries. A principal reason for this growth is the emergence and development of new materials, concepts and techniques for integrated device technologies that allow devices with complex functionalities to be miniaturized and combined on the chip-scale. In particular, technologies that allow for the fabrication of heterogeneous thin film structures have been especially valuable. One such technology, Crystal Ion Slicing (CIS), was developed at Columbia University and has been refined in recent years. CIS uses high-energy ion bombardment to exfoliate or 'slice' a thin, high-quality layer from the top surface of a parent optical crystal. Because the fabricated films produced by this technique share the physical, optical and electrical properties of the parent crystal, they are often superior to films achievable through other methods. In addition to thin oxide-film technology advances, there has been in recent years considerable interest in the emerging field of plasmonics. Plasmonics refers to the collection of integrated optical devices that utilize surface plasmon-polaritons generated at the interface of a metal and a dielectric, and the theories of their operation. The plasmons used in these devices may either be propagating or 'localized' plasmon resonances, are characterized by the exceptionally large electric field they carry, and in many cases demonstrate non-intuitive and startling physical behavior. Plasmonic device geometries have been intently studied because they possess great potential for nanoscale optical components, including devices whose principal feature sizes are smaller than the wavelength of light that they manipulate. This would in turn allow for hereto-unachievable levels of miniaturization and integration, reducing operational power and unit costs while increasing functionality. Unfortunately, the physics that govern plasmon interactions with

  16. Harmonic demodulation and minimum enhancement factors in field-enhanced near-field optical microscopy.

    PubMed

    Scarpettini, A F; Bragas, A V

    2015-01-01

    Field-enhanced scanning optical microscopy relies on the design and fabrication of plasmonic probes which had to provide optical and chemical contrast at the nanoscale. In order to do so, the scattering containing the near-field information recorded in a field-enhanced scanning optical microscopy experiment, has to surpass the background light, always present due to multiple interferences between the macroscopic probe and sample. In this work, we show that when the probe-sample distance is modulated with very low amplitude, the higher the harmonic demodulation is, the better the ratio between the near-field signal and the interferometric background results. The choice of working at a given n harmonic is dictated by the experiment when the signal at the n + 1 harmonic goes below the experimental noise. We demonstrate that the optical contrast comes from the nth derivative of the near-field scattering, amplified by the interferometric background. By modelling the far and near field we calculate the probe-sample approach curves, which fit very well the experimental ones. After taking a great amount of experimental data for different probes and samples, we conclude with a table of the minimum enhancement factors needed to have optical contrast with field-enhanced scanning optical microscopy. PMID:25231792

  17. Nonlinear optical properties of bismuth selenide

    NASA Astrophysics Data System (ADS)

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

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

  18. Enhanced thermoelectric properties in silicon nanowires

    NASA Astrophysics Data System (ADS)

    Mitrovic, Slobodan; Yu, Jen-Kan; Boukai, Akram; Tahir-Kheli, Jamil; Goddard, William A., III; Heath, James R.

    2008-03-01

    Recently, we demonstrated that silicon nanowires can be designed and fabricated to achieve an approximately 100-fold enhancement in thermoelectric efficiency compared to bulk silicon. Independent measurements of thermoelectric power, and thermal and electrical conductivities suggest that this improvement is due to phonon effects rather than quantum confinement. Here, we present the study of the scaling laws (i.e. nanowire length/width dependence) for the phonon dynamics and transport. We investigate the influence of the phonon drag, carrier mobility and doping on the thermoelectric properties, and the universality of these findings. This work is supported by the Office of Naval Research, the Department of Energy, the National Science Foundation, and the Defense Advanced Research Projects Agency.

  19. Exposure effects on the optical properties of building materials

    NASA Astrophysics Data System (ADS)

    Lane, Sarah; Cathcart, J. Michael; Harrell, J. Timothy

    2008-04-01

    Georgia Tech recently initiated a weathering effects measurement program to monitor the optical properties of several common building materials. A set of common building materials were placed outdoors and optical property measurements made over a series of weeks to assess the impact of exposure on these properties. Both reflectivity and emissivity measurements were made. Materials in this program included aluminum flashing, plastic sheets, bricks, roof shingles, and tarps. This paper will discuss the measurement approach, experimental setup, and present preliminary results from the optical property measurements.

  20. Theory of Anomalous Optical Properties of Bulk Rashba Conductor

    NASA Astrophysics Data System (ADS)

    Shibata, Junya; Takeuchi, Akihito; Kohno, Hiroshi; Tatara, Gen

    2016-03-01

    We theoretically explore the optical properties of a bulk Rashba conductor by calculating the transport coefficients at finite frequencies. It is demonstrated that the combination of direct and inverse Edelstein effects leads to a softening of the plasma frequency for the electric field perpendicular to the Rashba field, resulting in a hyperbolic electromagnetic metamaterial. In the presence of magnetization, a significant enhancement of anisotropic propagation (directional dichroism) is predicted because of the interband transition edge singularity. On the basis of an effective Hamiltonian analysis, the dichroism is demonstrated to be driven by toroidal and quadratic moments of the magnetic Rashba system. The effective theory of the cross-correlation effects has the same mathematical structure as that of insulating multiferroics.

  1. Structural, optical, and magnetic properties of FeVO3

    NASA Astrophysics Data System (ADS)

    Singh, Pooja; Gupta, Anurag; Dogra, Anjana

    2016-05-01

    We report the structural, optical, and magnetic properties of polycrystalline FeVO3 synthesized by solid state reaction technique.While FeVO3 has rhombohedral crystal structure with space group R-3c (167) identical to the parentα-Fe2O3, the lattice volume reduces due to the replacement of Fe3+ with V3+ having smaller ionic radii. The most remarkable outcome of doping is reduction in band gap from 2.1 (α-Fe2O3) to 1.5 eV (FeVO3), which is favorable for photo-electrochemical applications. Although the canted ferromagnetism persists in FeVO3, an enhancement in magnetic moment is observed as compared to the parent compound.

  2. Optical properties of mouse biotissues and their optical phantoms

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

  3. Enhancement of Anion Binding in Lanthanide Optical Sensors

    PubMed Central

    Cable, Morgan L.; Kirby, James P.; Gray, Harry B.; Ponce, Adrian

    2013-01-01

    be established from the ionization energy of Ln3+ → Ln4+. These results account for the order Tb3+ > Dy3+ > Eu3+ ≈ Sm3+. As with many lanthanide properties, ranging from hydration enthalpy to vaporization energy, this AL-induced enhancement shows a large discrepancy between Tb3+ and Eu3+ despite their similarity in size, a phenomenon known as the ‘gadolinium break.’ This discrepancy, based on the unusual stabilities of the Eu2+ and Tb4+ oxidation states, results from the half-shell effect, as both of these ions have half-filled 4f-shells. The high polarizability of Tb3+ explains the extraordinarily large increase in the binding affinity of anions for terbium compared to other lanthanides. We recommend that researchers consider this AL-induced enhancement when designing lanthanide-macrocycle optical sensors. Ancillary ligands also can reduce the impact of interfering species such as phosphate) commonly found in environmental and physiological samples. PMID:24032446

  4. Method for enhancing signals transmitted over optical fibers

    DOEpatents

    Ogle, J.W.; Lyons, P.B.

    1981-02-11

    A method for spectral equalization of high frequency spectrally broadband signals transmitted through an optical fiber is disclosed. The broadband signal input is first dispersed by a grating. Narrow spectral components are collected into an array of equalizing fibers. The fibers serve as optical delay lines compensating for material dispersion of each spectral component during transmission. The relative lengths of the individual equalizing fibers are selected to compensate for such prior dispersion. The output of the equalizing fibers couple the spectrally equalized light onto a suitable detector for subsequent electronic processing of the enhanced broadband signal.

  5. Method for enhancing signals transmitted over optical fibers

    DOEpatents

    Ogle, James W.; Lyons, Peter B.

    1983-01-01

    A method for spectral equalization of high frequency spectrally broadband signals transmitted through an optical fiber. The broadband signal input is first dispersed by a grating. Narrow spectral components are collected into an array of equalizing fibers. The fibers serve as optical delay lines compensating for material dispersion of each spectral component during transmission. The relative lengths of the individual equalizing fibers are selected to compensate for such prior dispersion. The output of the equalizing fibers couple the spectrally equalized light onto a suitable detector for subsequent electronic processing of the enhanced broadband signal.

  6. Plasmonic enhancement of direct optical initiation of explosives

    SciTech Connect

    Moore, David Steven; Clarke, Steven A; Glambra, Anna M

    2010-01-01

    Current Direct Optical Initiation (DOI) detonators use a laser focused onto a thin metal layer to drive a hot plasma and/or fragments into PETN powder. Previous studies showed a dramatic decrease in laser energies required to initiate the detonation using this approach over direct laser illumination of the PETN powder. Plasmonic metal nanostructures have been shown capable of strongly coupling laser energy into adjacent materials. We have incorporated gold nanospheres into PETN powder and are investigating their plasmonic enhancement of direct optical initiation via measurements of threshold laser energies and streak camera measurements for calculation of run to detonation distances compared to other DOI schemes.

  7. PLASMONIC ENHANCEMENT OF DIRECT OPTICAL INITIATION OF EXPLOSIVES

    SciTech Connect

    Moore, D. S.; Akinci, A. A.; Giambra, A. M.; Clarke, S. A.

    2009-12-28

    Current Direct Optical Initiation (DOI) detonators use a laser focused onto a thin metal layer to drive a hot plasma and/or fragments into PETN powder. Previous studies showed a dramatic decrease in laser energies required to initiate the detonation using this approach over direct laser illumination of the PETN powder. Plasmonic metal nanostructures have been shown capable of strongly coupling laser energy into adjacent materials. We have incorporated gold nanospheres into PETN powder and are investigating their plasmonic enhancement of direct optical initiation via measurements of threshold laser energies and streak camera measurements for calculation of run to detonation distances compared to other DOI schemes.

  8. Plasmonic enhancement of direct optical initiation of explosives

    SciTech Connect

    Moore, David Steven; Akinci, Adrian A; Giambra, Anna M; Clarke, Steven A

    2009-01-01

    Current Direct Optical Initiation (DOI) detonators use a laser focused onto a thin metal layer to drive a hot plasma and/or fragments into PETN powder. Previous studies showed a dramatic decrease in laser energies required to initiate the detonation using this approach over direct laser illumination of the PETN powder. Plasmonic metal nanostructures have been shown capable of strongly coupling laser energy into adjacent materials. We have incorporated gold nanospheres into PETN powder and are investigating their plasmonic enhancement of direct optical initiation via measurements of threshold laser energies and streak camera measurements for calculation of run to detonation distances compared to other DOI schemes.

  9. Differentiation of optical isomers through enhanced weak-field interactions

    NASA Technical Reports Server (NTRS)

    Aronowitz, S.

    1980-01-01

    The influence of weak field interaction terms due to the cooperative effects which arise from a macroscopic assemblage of interacting sites is studied. Differential adsorption of optical isomers onto an achiral surface is predicted to occur if the surface was continuous and sufficiently large. However, the quantity of discontinuous crystal surfaces did not enhance the percentage of differentiation and thus the procedure of using large quantities of small particles was not a viable technique for obtaining a detectable differentiation of optical isomers on an achiral surface.

  10. Enhanced third-order nonlinear optical properties determined in thin films using the Z-scan technique: bis(μ-4,4'-oxydibenzoato)bis[(4'-phenyl-2,2':6',2''-terpyridine)cobalt(II)].

    PubMed

    Liu, Runqiang; Zhao, Ning; Liu, Ping; An, Caixia; Lian, Zhaoxun

    2016-05-01

    π-Conjugated organic materials exhibit high and tunable nonlinear optical (NLO) properties, and fast response times. 4'-Phenyl-2,2':6',2''-terpyridine (PTP) is an important N-heterocyclic ligand involving π-conjugated systems, however, studies concerning the third-order NLO properties of terpyridine transition metal complexes are limited. The title binuclear terpyridine Co(II) complex, bis(μ-4,4'-oxydibenzoato)-κ(3)O,O':O'';κ(3)O'':O,O'-bis[(4'-phenyl-2,2':6',2''-terpyridine-κ(3)N,N',N'')cobalt(II)], [Co2(C14H8O5)2(C21H15N3)2], (1), has been synthesized under hydrothermal conditions. In the crystal structure, each Co(II) cation is surrounded by three N atoms of a PTP ligand and three O atoms, two from a bidentate and one from a symmetry-related monodentate 4,4'-oxydibenzoate (ODA(2-)) ligand, completing a distorted octahedral coordination geometry. Neighbouring [Co(PTP)](2+) units are bridged by ODA(2-) ligands to form a ring-like structure. The third-order nonlinear optical (NLO) properties of (1) and PTP were determined in thin films using the Z-scan technique. The title compound shows a strong third-order NLO saturable absorption (SA), while PTP exhibits a third-order NLO reverse saturable absorption (RSA). The absorptive coefficient β of (1) is -37.3 × 10(-7) m W(-1), which is larger than that (8.96 × 10(-7) m W(-1)) of PTP. The third-order NLO susceptibility χ((3)) values are calculated as 6.01 × 10(-8) e.s.u. for (1) and 1.44 × 10(-8) e.s.u. for PTP. PMID:27146576

  11. Lasing effect enhanced by optical Tamm state with in-plane lattice plasmon

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenqing; Li, Yunhui; Liu, Wenxing; Sun, Yong; Jiang, Haitao; Chen, Hong

    2016-02-01

    A new type of surface-emitting laser based on in-plane lattice plasmons (LPs) and optical Tamm states (OTSs) is proposed, with arrays of metallic micro-disks followed by a photonic crystal. Due to the presence of LP modes, the reflection properties of the combined LP-OTS structure, including the spectrum linewidth, Q-factor and electromagnetic field, can be optimized for better lasing behavior. When the combined LP-OTS structure with a gain medium is optically pumped, a much lower lasing threshold and higher emission intensity can be achieved simultaneously, compared with the individual LP structure. This phenomenon successfully demonstrates the enhancement of the lasing efficiency.

  12. 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

  13. Optical switching and contrast enhancement in intense laser systems by cascaded optical parametric amplification

    SciTech Connect

    Jovanovic, I; Haefner, C; Wattellier, B; Barty, C J

    2005-09-06

    Optical parametric chirped-pulse amplification (OPCPA) can be used to improve the prepulse contrast in chirped-pulse amplification systems by amplifying the main pulse with a total saturated OPCPA gain, while not affecting the preceding prepulses of the seed oscillator mode-locked pulse train. We show that a simple modification of a multistage OPCPA system into a cascaded optical parametric amplifier (COPA) results in an optical switch and extreme contrast enhancement which can completely eliminate the preceding and trailing oscillator pulses. Instrument-limited measurement of prepulse contrast ratio of 1.4 x 10{sup 11} is demonstrated from COPA at a 30-mJ level.

  14. 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.

  15. Structural, optical and electrical properties of CdS–polyaniline Langmuir–Blodgett films

    SciTech Connect

    Das, Nayan Mani Roy, Dhrubojyoti Gupta, P. S.; Gupta, M.; Ganesan, V.

    2014-04-24

    Structural, optical and electrical properties study of the cadmium sulphide (CdS) incorporated polyaniline (PANI) thin films with varying layers have been carried out. It is seen that layer variation enhances the particle mean sizes with quenching of photoluminescence and an increase in rectifying nature of current-voltage measurements.

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

    SciTech Connect

    Gharbavi, K.; Badehian, H.

    2015-07-15

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

  17. Determines the Thermal and Optical Properties of Fenestration Systems

    Energy Science and Technology Software Center (ESTSC)

    1995-01-27

    WINDOW4.1 computes the thermal properties of windows and other fenestration elements used in typical residential and commercial buildings. Manufactures, specifiers, architects, consumers, and the energy code specialists all need to know these properties (U-values, Solar Heat Gain Coefficients, optical properties). The use of this program to calculate these properties is typically much more cost effective than laboratory test procedures. Properties of complete window systems are based on libraries (or user input) component data.

  18. Core-shell potassium niobate nanowires for enhanced nonlinear optical effects.

    PubMed

    Richter, J; Steinbrück, A; Zilk, M; Sergeyev, A; Pertsch, T; Tünnermann, A; Grange, R

    2014-05-21

    We demonstrate the synthesis as well as the optical characterization of core-shell nanowires. The wires consist of a potassium niobate (KNbO3) core and a gold shell. The nonlinear optical properties of the core are combined with the plasmonic resonance of the shell and offer an enhanced optical signal in the near infrared spectral range. We compare two different functionalization schemes of the core material prior to the shell growth process: silanization and polyelectrolyte. We show that the latter leads to a smoother and complete core-shell nanostructure and an easier-to-use synthesis process. A Mie-theory based theoretical approach is presented to model the enhanced second-harmonic generated (SHG) signal of the core-shell wires, illustrating the influence of the fabrication-induced varying geometrical factors of wire radius and shell thickness. A spectroscopic measurement on a core-shell nanowire shows a strong localized surface plasmon resonance close to 900 nm, which matches with the SHG resonance obtained from nonlinear optical experiments with the same nanowire. According to the simulation, this corresponds to a wire radius of 35 nm and a shell thickness of 7.5 nm. By comparing SHG signals measured from an uncoated nanowire and the coated one, we obtain a 250 times enhancement factor. This is less than the calculated enhancement, which considers a cylindrical nanowire with a perfectly smooth shell. Thus, we explain this discrepancy mainly with the roughness of the synthesized gold shell. PMID:24675780

  19. Skull Optical Clearing Solution for Enhancing Ultrasonic and Photoacoustic Imaging.

    PubMed

    Yang, Xiaoquan; Zhang, Yang; Zhao, Kai; Zhao, Yanjie; Liu, Yanyan; Gong, Hui; Luo, Qingming; Zhu, Dan

    2016-08-01

    The performance of photoacoustic microscopy (PAM) degrades due to the turbidity of the skull that introduces attenuation and distortion of both laser and stimulated ultrasound. In this manuscript, we demonstrated that a newly developed skull optical clearing solution (SOCS) could enhance not only the transmittance of light, but also that of ultrasound in the skull in vitro. Thus the photoacoustic signal was effectively elevated, and the relative strength of the artifacts induced by the skull could be suppressed. Furthermore in vivo studies demonstrated that SOCS could drastically enhance the performance of photoacoustic microscopy for cerebral microvasculature imaging. PMID:26886977

  20. Real-time edge-enhanced optical correlator

    NASA Technical Reports Server (NTRS)

    Liu, Tsuen-Hsi (Inventor); Cheng, Li-Jen (Inventor)

    1992-01-01

    Edge enhancement of an input image by four-wave mixing a first write beam with a second write beam in a photorefractive crystal, GaAs, was achieved for VanderLugt optical correlation with an edge enhanced reference image by optimizing the power ratio of a second write beam to the first write beam (70:1) and optimizing the power ratio of a read beam, which carries the reference image to the first write beam (100:701). Liquid crystal TV panels are employed as spatial light modulators to change the input and reference images in real time.

  1. Enhancing and redirecting carbon nanotube photoluminescence by an optical antenna.

    PubMed

    Böhmler, Miriam; Hartmann, Nicolai; Georgi, Carsten; Hennrich, Frank; Green, Alexander A; Hersam, Mark C; Hartschuh, Achim

    2010-08-01

    We observe the angular radiation pattern of single carbon nanotubes' photoluminescence in the back focal plane of a microscope objective and show that the emitting nanotube can be described by a single in-plane point dipole. The near-field interaction between a nanotube and an optical antenna modifies the radiation pattern that is now dominated by the antenna characteristics. We quantify the antenna induced excitation and radiation enhancement and show that the radiative rate enhancement is connected to a directional redistribution of the emission. PMID:20721031

  2. Bulk nuclear polarization enhanced at room temperature by optical pumping.

    PubMed

    Fischer, Ran; Bretschneider, Christian O; London, Paz; Budker, Dmitry; Gershoni, David; Frydman, Lucio

    2013-08-01

    Bulk (13)C polarization can be strongly enhanced in diamond at room temperature based on the optical pumping of nitrogen-vacancy color centers. This effect was confirmed by irradiating single crystals at a ~50 mT field promoting anticrossings between electronic excited-state levels, followed by shuttling of the sample into an NMR setup and by subsequent (13)C detection. A nuclear polarization of ~0.5%--equivalent to the (13)C polarization achievable by thermal polarization at room temperature at fields of ~2000 T--was measured, and its bulk nature determined based on line shape and relaxation measurements. Positive and negative enhanced polarizations were obtained, with a generally complex but predictable dependence on the magnetic field during optical pumping. Owing to its simplicity, this (13)C room temperature polarizing strategy provides a promising new addition to existing nuclear hyperpolarization techniques. PMID:23952444

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

    SciTech Connect

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

    2015-01-26

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

  4. Optical detection of nanoparticle-enhanced human papillomavirus genotyping microarrays.

    PubMed

    Li, Xue Zhe; Kim, Sookyung; Cho, Wonhyung; Lee, Seung-Yop

    2013-02-01

    In this study, we propose a new detection method of nanoparticle-enhanced human papillomavirus genotyping microarrays using a DVD optical pick-up with a photodiode. The HPV genotyping DNA chip was labeled using Au/Ag core-shell nanoparticles, prepared on a treatment glass substrate. Then, the bio information of the HPV genotyping target DNA was detected by measuring the difference of the optical signals between the DNA spots and the background parts for cervical cancer diagnosis. Moreover the approximate linear relationship between the concentration of the HPV genotyping target DNA and the optical signal depending on the density of Au/Ag core-shell nanoparticles was obtained by performing a spot finding algorithm. It is shown that the nanoparticle-labeled HPV genotyping target DNA can be measured and quantified by collecting the low-cost photodiode signal on the treatment glass chip, replacing high-cost fluorescence microarray scanners using a photomultiplier tube. PMID:23413051

  5. Enhancements in Magnesium Die Casting Impact Properties

    SciTech Connect

    David Schwam; John F. Wallace; Yulong Zhu; Srinath Viswanathan; Shafik Iskander

    2000-06-30

    The need to produce lighter components in transportation equipment is the main driver in the increasing demand for magnesium castings. In many automotive applications, components can be made of magnesium or aluminum. While being lighter, often times the magnesium parts have lower impact and fatigue properties than the aluminum. The main objective of this study was to identify potential improvements in the impact resistance of magnesium alloys. The most common magnesium alloys in automotive applications are AZ91D, AM50 and AM60. Accordingly, these alloys were selected as the main candidates for the study. Experimental quantities of these alloys were melted in an electrical furnace under a protective atmosphere comprising sulfur hexafluoride, carbon dioxide and dry air. The alloys were cast both in a permanent mold and in a UBE 315 Ton squeeze caster. Extensive evaluation of tensile, impact and fatigue properties was conducted at CWRU on permanent mold and squeeze cast test bars of AZ91, AM60 and AM50. Ultimate tensile strength values between 20ksi and 30ksi were obtained. The respective elongations varied between 25 and 115. the Charpy V-notch impact strength varied between 1.6 ft-lb and 5 ft-lb depending on the alloy and processing conditions. Preliminary bending fatigue evaluation indicates a fatigue limit of 11-12 ksi for AM50 and AM60. This is about 0.4 of the UTS, typical for these alloys. The microstructures of the cast specimens were investigated with optical and scanning electron microscopy. Concomitantly, a study of the fracture toughness in AM60 was conducted at ORNL as part of the study. The results are in line with values published in the literature and are representative of current state of the art in casting magnesium alloys. The experimental results confirm the strong relationship between aluminum content of the alloys and the mechanical properties, in particular the impact strength and the elongation. As the aluminum content increases from about 5

  6. Iron nanoparticles embedded in carbon films: structural and optical properties

    NASA Astrophysics Data System (ADS)

    Mashayekhi, Fatemeh; Shafiekhani, Azizollah; Sebt, Seyed Ali

    2016-06-01

    In the present work amorphous hydrogenated carbon films with sputtered iron nanoparticles (Fe NPs @ a-C:H) were deposited by co-deposition of RF-sputtering and RF-plasma enhanced chemical vapor deposition methods using acetylene gas and iron target on quartz and silicon substrates. Samples were prepared in different initial pressures and during constant deposition time. The crystalline structure of Fe NPs @ a-C:H was studied using X-ray diffraction and selected area electron diffraction patterns. The X-ray photoelectron spectroscopy analysis presents that increasing the initial pressure decreases the atomic ratio of Fe/C and the sp3-hybridized carbon content in prepared samples. The transmission electron microscope image shows the encapsulated Fe NPs in carbon films. The optical properties and localized surface plasmon resonance (LSPR) of samples were studied using UV-visible spectrophotometry, which is shown that increasing of Fe content decreases the intensity of LSPR peak and increases the optical band gap.

  7. Electronic structure and optical properties of graphene/stanene heterobilayer.

    PubMed

    Chen, Xianping; Meng, Ruishen; Jiang, Junke; Liang, Qiuhua; Yang, Qun; Tan, Chunjian; Sun, Xiang; Zhang, Shengli; Ren, Tianling

    2016-06-28

    The structural, electronic and optical properties of the graphene hybrid with stanene, the tin counterpart of graphene, are investigated by means of density functional calculation with the observation of band gap opening and enhanced visible light response. The lattice mismatch between graphene and stanene is taken into consideration and several stacking methods for model construction are proposed to study the possible effects. The Dirac feature can be observed in this bilayer system with relatively stronger interlayer interaction than weak van der Waals forces, which is ascribed to the unsaturated p orbital of stanene. Despite the mutual semi-metal nature of graphene and stanene, it is significant to note a band gap opening and the electrical neutrality of the bilayer. The combination of high carrier mobility of graphene and the excellent spin Hall effect of stanene is expected to coexist in the bilayer structure. In addition, we found that the stanene monolayer has a relatively lower work function than graphene and more importantly, it exhibits more pronounced optical absorption than graphene. The results indicate that a graphene/stanene heterobilayer will facilitate the performance of stanene related spintronic devices and is therefore a good candidate for photoelectronic devices. PMID:27253913

  8. 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

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

    NASA Astrophysics Data System (ADS)

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

    1998-05-01

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

  10. Enhanced optical squeezing from a degenerate parametric amplifier via time-delayed coherent feedback

    NASA Astrophysics Data System (ADS)

    Német, Nikolett; Parkins, Scott

    2016-08-01

    A particularly simple setup is introduced to study the influence of time-delayed coherent feedback on the optical squeezing properties of the degenerate parametric amplifier. The possibility for significantly enhanced squeezing is demonstrated both on resonance and in sidebands, at a reduced pump power compared to the case without feedback. We study a broad range of operating parameters and their influence on the characteristic squeezing of the system. A classical analysis of the system dynamics reveals the connection between the feedback-modified landscape of stability and enhanced squeezing.

  11. Optical Properties of Multi-Layered Insulation

    NASA Astrophysics Data System (ADS)

    Rodriguez, H.; Abercromby, K.; Mulrooney, M.; Barker, E.

    spectral measurements were acquired for each MLI sample. Spectral data will be combined to match the wavelength region of photometric data to establish a fiduciary reference for the photometric measurements. Not only will this help validate the color photometry, but it will also assist interpretation and analysis of telescopic data. As an example, copper-colored Kapton shows a strong absorption feature near 4800 angstroms. If the observed debris is MLI and the outer layer of copper coloring of Kapton is present, evidence of this material should be seen spectroscopically by the specific absorption feature as well as photometrically (eg. by using R-B (red-blue) light curves). Using laboratory photometric and spectroscopic measurements an optical property database is provided for a representative high A/m object. These results should directly aid the accurate interpretation of telescopically acquired optical orbital debris photometry of both high A/m targets as well as satellites and spacecraft that incorporate MLI.

  12. 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.

  13. 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.

  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. Optical properties of porphyrin: graphene oxide composites

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  16. Engineer-able optical properties of trilayer graphene nanoribbon

    NASA Astrophysics Data System (ADS)

    Meshginqalam, Bahar; T, Hamid Toloue A.; Taghi Ahmadi, Mohammad; Sabatyan, Arash

    2016-03-01

    Graphene with a single atomic layer of carbon indicates two-dimensional behavior which plays an important role in sensor application, because of its high surface-to-volume ratio. Its interesting optical properties lead to low-cost and accurate optical devices as well. In the presented work trilayer graphene nanoribbon (TGN) with focus on its optical property for different incident wave lengths in the presence of applied voltage is explored. In low bias condition the optical conductance is modeled and dielectric constant and refractive index based on the estimated conductance are calculated theoretically; finally the obtained results are investigated numerically. Controllable optical properties supported by applied voltage on TGN are proved. Consequently, the proposed model indicates TGN as a possible candidate on surface plasmon based sensors, which needs to be explored.

  17. Detection of optical properties in small region by diffuse reflectance

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Li, Shengcai; Wang, Kai; Zhu, Zongping; Wang, Wei

    2015-11-01

    The optical properties of small and highly absorbing tissues can be determined by measurement of spatially resolved diffuse reflectance at short source-detector separations. Spatial resolution and number of measuring point influence the inverting precision of optical property directly from the experimental diffuse reflectance. To increase spatial resolution and number of measuring point, a high-resolution and multiple points detection system is designed. A special optical fiber array probe is employed. Its spatial resolution is 0.125mm. The system is proved to be reliable by comparing the experimental result of diffuse reflectance from small region 0.125mm-1.25mm with that of numerical simulation. The inverting method based on Monte Carlo simulation is designed, by which optical properties can be achieved by building optical parameter date base and training artificial neural network (ANN).

  18. Enhancement of optical coherence microscopy in turbid media by an optical parametric amplifier.

    PubMed

    Zhao, Youbo; Tu, Haohua; Liu, Yuan; Bower, Andrew J; Boppart, Stephen A

    2015-06-01

    We report the enhancement in imaging performance of a spectral-domain optical coherence microscope (OCM) in turbid media by incorporating an optical parametric amplifier (OPA). The OPA provides a high level of optical gain to the sample arm, thereby improving the signal-to-noise ratio of the OCM by a factor of up to 15 dB. A unique nonlinear confocal gate is automatically formed in the OPA, which enables selective amplification of singly scattered (ballistic) photons against the multiply-scattered light background. Simultaneous enhancement in both imaging depth and spatial resolution in imaging microstructures in highly light-scattering media are demonstrated with the combined OPA-OCM setup. Typical OCM inteferograms (left) and images (right) without and with OPA. PMID:25196251

  19. Magneto-optical properties of one-dimensional orderly nanocorrugation made from magnetic quadrilayer films.

    PubMed

    Zhang, Shaoyin; Xia, Wenbin; Li, Daoyong; Gao, Jinlong; Tang, Zhixiong; Tang, Shaolong; Du, Youwei

    2015-06-29

    Magneto-optical (MO) Kerr effect and optical reflectance are investigated in the visible light region for one-dimensional orderly nanocorrugation of magnetic quadrilayer films. We find that the MO enhancement originates from the combined action between cavity effect and surface plasmon resonance. The coupling between surface plasmon polaritions and localized surface plasmons cannot only enhance the magnitude of Kerr angle, but also alter the sign of Kerr rotation. In addition, the MO properties on the nanocomposite films can be tuned by the thickness of the intermediate HfO2 layer due to the cavity effect in multilayer. PMID:26191760

  20. Enhanced photocoagulation with catheter-based diffusing optical device

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Kim, Jeehyun; Oh, Jungwhan

    2012-11-01

    A novel balloon catheter-based diffusing optical device was designed and evaluated to assist in treating excessive menstrual bleeding. A synthetic fused-silica fiber was micro-machined precisely to create scattering segments on a 25 mm long fiber tip for uniform light distribution. A visible wavelength (λ=532 nm) was used to specifically target the endometrium due to the high vascularity of the uterine wall. Optical simulation presented 30% wider distribution of photons along with approximately 40% higher irradiance induced by addition of a glass cap to the diffuser tip. Incorporation of the optical diffuser with a polyurethane balloon catheter considerably enhanced coagulation depth and area (i.e., 3.5 mm and 18.9 cm2 at 1 min irradiation) in tissue in vitro. The prototype device demonstrated the coagulation necrosis of 2.8±1.2 mm (n=18) and no thermal damage to myometrium in in vivo caprine models. A prototype 5 cm long balloon catheter-assisted optical diffuser was also evaluated with a cadaveric human uterus to confirm the coagulative response of the uterine tissue as well as to identify the further design improvement and clinical applicability. The proposed catheter-based diffusing optical device can be a feasible therapeutic tool to photocoagulate endometrial cell layers in an efficient and safe manner.

  1. 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

  2. The optical properties of crystalline melilite

    NASA Astrophysics Data System (ADS)

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

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

  3. Optical and magnetic properties of hexagonal arrays of subwavelength holes in optically thin cobalt films.

    PubMed

    Ctistis, G; Papaioannou, E; Patoka, P; Gutek, J; Fumagalli, P; Giersig, M

    2009-01-01

    In this study, we present our experimental results on the optical, magnetic, as well as magneto-optic properties of hexagonal arrays of subwavelength holes in optically thin cobalt films. Different meshes were used with hole diameters ranging between 220 and 330 nm while the interhole distance has been kept constant at 470 nm. The hole pattern modifies completely the magnetic behavior of the cobalt films; it gives rise to an increase of the coercive field of the in-plane magnetization with increasing hole diameter and to the appearance of out-of-plane magnetization components. Magneto-optic measurements show a spectacular magneto-optic response at wavelengths where surface plasmon-polaritons are supported by the structure as deduced in optical measurements. The experiments demonstrate the ability to artificially control the magnetic and thus the magneto-optic properties in hole array structures. PMID:19072720

  4. Nonlinear Optical Properties of Triphenylalanine-based Peptide Nanostructures

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, A. V.; Mishina, E. D.; Sigov, A. S.

    2016-05-01

    Nonlinear optical properties of peptide nanobelts and peptide nanospheres, the two types of self-assembled triphenylalanine-based peptide nanostructures, are studied. Nanobelts nonlinear susceptibility tensor components are evaluated, and nanobelts crystal structure and crystallographic orientation are defined on the basis of nonlinear optical mapping and polarization dependences of the second harmonic signal. The results obtained suggest that it is possible to use these materials as biologically compatible nonlinear optical converters.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  6. Size- and dimensionality-dependent optical, magnetic and magneto-optical properties of binary europium-based nanocrystals: EuX (X = O, S, Se, Te)

    NASA Astrophysics Data System (ADS)

    Zhou, Xingzhi; Zhang, Kelvin HL; Xiong, Jie; Park, Ju-Hyun; Dickerson, James H.; He, Weidong

    2016-05-01

    Europium chalcogenides (EuX, X = O, S, Se, Te), a class of prototypical Heisenberg magnetic semiconductors, exhibit intriguing properties in optics, magnetism, and magneto-optics at the nanoscale, and have broad application potential in optical/magnetic sensors, spintronics, optical isolators, etc. EuX nanocrystals (NCs) exhibit enhanced properties, such as high saturation magnetization, a strong magneto-optic effect (Faraday rotation), and high magneto resistance, which are all unanimously dependent on the NC’s size, shape, and surface information. In this report, we give an overview of the fundamental properties of bulk EuX, and illustrate the quantum confinement effects on the optical, magnetic and magneto-optical properties of EuX nanostructures. We then focus on doping and self-assembly—two efficient methods that enhance magnetic properties by manipulating magnetic coupling in EuX nanostructures. In particular, we look towards future research on Eu2+ NCs, which along with the overview provides an up-to-date platform for evaluating the fundamental properties and application potential of Eu-based semiconductors.

  7. Size- and dimensionality-dependent optical, magnetic and magneto-optical properties of binary europium-based nanocrystals: EuX (X = O, S, Se, Te).

    PubMed

    Zhou, Xingzhi; Zhang, Kelvin H L; Xiong, Jie; Park, Ju-Hyun; Dickerson, James H; He, Weidong

    2016-05-13

    Europium chalcogenides (EuX, X = O, S, Se, Te), a class of prototypical Heisenberg magnetic semiconductors, exhibit intriguing properties in optics, magnetism, and magneto-optics at the nanoscale, and have broad application potential in optical/magnetic sensors, spintronics, optical isolators, etc. EuX nanocrystals (NCs) exhibit enhanced properties, such as high saturation magnetization, a strong magneto-optic effect (Faraday rotation), and high magneto resistance, which are all unanimously dependent on the NC's size, shape, and surface information. In this report, we give an overview of the fundamental properties of bulk EuX, and illustrate the quantum confinement effects on the optical, magnetic and magneto-optical properties of EuX nanostructures. We then focus on doping and self-assembly-two efficient methods that enhance magnetic properties by manipulating magnetic coupling in EuX nanostructures. In particular, we look towards future research on Eu(2+) NCs, which along with the overview provides an up-to-date platform for evaluating the fundamental properties and application potential of Eu-based semiconductors. PMID:27023644

  8. Optical properties of arrays of five-pointed nanostars

    NASA Astrophysics Data System (ADS)

    Zhu, Shaoli; Cortie, Michael

    2015-12-01

    The optical properties of nanostructures control the performance of applications that are based on localized surface plasmon resonances. Here we use finite-difference time-domain calculations to explore the effect of geometry and material-of-construction on the transmission and near-field optical intensity of arrays of closely-spaced five-pointed nano-star shapes. We compared isolated solid star shapes to star-shaped nano-gaps set within a surrounding square metal shape. The materials investigated were silver, gold, copper and aluminum. The study showed that both the geometry and material chosen had a significant effect on the resulting transmittance spectra. Transmittance spectra of arrays of solid five-pointed nano-stars did not show any strong absorption peaks in the visible region whereas, in contrast, the arrays of star-shaped nano-gaps set within the metal squares did show strong absorption peaks. However, on closer examination it became obvious that the enhanced electric field of the latter was mostly on the corners of the square metal domains and not actually in or on the star-shaped nano-gaps. Therefore we deduce that arrays of simple metal squares will be more suitable as substrates for surface enhanced Raman spectroscopy than arrays of stars or star-shaped nano-gaps. Gold, silver and copper were suitable choices for the latter type of array. Aluminum was unsuitable, at least for applications in the visible part of the spectrum, because it was associated with relatively weak electric fields.

  9. 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.

  10. Optical properties of monodisperse gold nanoshells on silica cores

    NASA Astrophysics Data System (ADS)

    Khanadeev, Vitaly; Khlebtsov, Boris; Khlebtsov, Nikolai

    2016-04-01

    Gold nanoshells are promising nanoparticles for biomedical applications such as biosensing, photothermal therapy, and surface enhanced Raman scattering. However, existing synthesis protocols produce polydisperse samples with extinction plasmonic spectrum much broader than that predicted by electromagnetic Mie simulations. Here we report on improved synthesis of gold nanoshells using monodisperse silica cores with very narrow size distributions of separated samples. As a result we were able to fabricate high quality silica/gold nanoshells with very narrow plasmon resonance peak, which is in good agreement with Mie calculations based on polydisperse TEM models. TEM images revealed a presence of dimers and trimers in as-prepared nonseparated samples. We performed extensive finite difference time-domain (FDTD) simulations to show that the plasmonic response of aggregated nanoshells results in enhanced extinction across NIR spectral band and in a minor broadening of the main plasmonic peak. To summarize, the improved synthetic technology produces high quality monodisperse silica/gold nanoshells which optical properties are in excellent agreement with electromagnetic simulations based on TEM size distributions.

  11. Cooling enhancement in optical refrigeration by non-resonant optical cavities

    NASA Astrophysics Data System (ADS)

    Farfan, B. G.; Gragossian, A.; Symonds, G.; Ghasemkhani, M. R.; Albrecht, A. R.; Sheik-Bahae, M.; Epstein, R. I.

    2016-05-01

    We present a study of cooling enhancement in optical refrigerators by the implementation of advanced non-resonant optical cavities. Cavity designs have been studied to maximize pump light-trapping to improve absorption and thereby increase the efficiency of optical refrigeration. The approaches of non-resonant optical cavities by Herriott-cell and totalinternal- reflection were studied. Ray-tracing simulations and experiments were performed to analyze and optimize the different light-trapping configurations. Light trapping was studied for laser sources with high quality beams and for beams with large divergences, roughly corresponding to the output from fiber lasers and from diode lasers, respectively. We present a trade-off analysis between performance, reliability, and manufacturability.

  12. Use of laser radar imagery in optical pattern recognition: the Optical Processor Enhanced Ladar (OPEL) Program

    NASA Astrophysics Data System (ADS)

    Goldstein, Dennis H.; Mills, Stuart A.; Dydyk, Robert B.

    1998-03-01

    The Optical Processor Enhanced Ladar (OPEL) program is designed to evaluate the capabilities of a seeker obtained by integrating two state-of-the-art technologies, laser radar, or ladar, and optical correlation. The program is a thirty-two month effort to build, optimize, and test a breadboard seeker system (the OPEL System) that incorporates these two promising technologies. Laser radars produce both range and intensity image information. Use of this information in an optical correlator is described. A correlator with binary phase input and ternary amplitude and phase filter capability is assumed. Laser radar imagery was collected on five targets over 360 degrees of azimuth from 3 elevation angles. This imagery was then processed to provide training sets in preparation for filter construction. This paper reviews the ladar and optical correlator technologies used, outlines the OPEL program, and describes the OPEL system.

  13. Optical properties of nanowire dimers with a spatially nonlocal dielectric function.

    SciTech Connect

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

    2010-09-01

    We study the optical spectra and electromagnetic field enhancements around cylindrical and triangular Ag nanowire dimers, allowing for a spatially nonlocal dielectric function that partially accounts for quantum mechanical effects. For the triangular structures, we pay particular attention to how these properties depend on the sharpness of the nanowire's tips. We demonstrate that significant differences exist from classical electrodynamics that employs a more common, spatially local dielectric function. These differences are shown to arise from the optical excitation of volume plasmons inside of the structures, analogous to one-particle quantum mechanical states, which lead to complex and striking patterns of material polarization. These results are important for further understanding the optical properties of structures at the nanoscale and have implications for numerous physical processes, such as surface-enhanced Raman scattering.

  14. Optical Properties of Nanoscale Bismuth Selenide and Its Heterocrystals

    NASA Astrophysics Data System (ADS)

    Vargas, Anthony

    Over the past 12 years since the groundbreaking work on graphene, the field of 2D layered materials has grown by leaps and bounds as more materials are theoretically predicted and experimentically verified. These materials and their unique electronic, optical, and mechanical properties have inspired the scientific community to explore and investigate novel, fundamental physical phenomena as well create and refine technological devices which leverage the host of unique benefits which these materials possess. In the past few years, this burgeoning field has heavily moved towards combining layers of various materials into novel heterostructures. These heterostructures are an exciting area of research because of the plethora of exciting possibilities and results which arise due to the large number of heterostructure combinations and configurations. Particularly, the research into the optical properties of these layered materials and their heterostructures under confinement provides another exciting avenue for developing optoelectric devices. In this dissertation, I present work on the synthesis of Bi2Se 3 nanostructures via chemical vapor deposition (CVD) and the study of the optical properties of these nanostructures and their heterostructures with MoS2. The bulk of the current published work on Bi2Se 3 has focused on the exotic topological properties of its surface states, both interesting fundamental physics purposes as well as for studying avenues for spintronics. In contrast, the work presented here focuses on studying the optical properties of Bi2Se3 nanostructures and how these properties evolve when subjected to confinement. Specifically, the absorbance of singlecrystal Bi2Se3 with sizes tailored down to a few nanometers in diameter and a few quintuple layers (QLs) in thickness. We find a dramatically large bandgap, Eg ≥ 2.5 eV, in the smallest particles which is much higher than that seen in 1QL measurements taken with ARPES. Additionally, utilizing

  15. Quantum analysis of polarization properties of optical beams

    SciTech Connect

    Lahiri, Mayukh; Wolf, Emil

    2010-10-15

    We present a quantum treatment of polarization of optical beams and discuss some properties of beams of any state of polarization. The analysis is based on quantum-mechanical interpretation of a canonical experiment that is used to elucidate polarization properties of stochastic fields in classical optics. Our work shows how to apply some ideas and techniques, commonly used in the classical theory, for fields that cannot be treated classically.

  16. Electronic, Optical, and Thermal Properties of Reduced-Dimensional Semiconductors

    NASA Astrophysics Data System (ADS)

    Huang, Shouting

    Reduced-dimensional materials have attracted tremendous attention because of their new physics and exotic properties, which are of great interests for fundamental science. More importantly, the manipulation and engineering of matter on an atomic scale yield promising applications for many fields including nanoelectronics, nanobiotechnology, environments, and renewable energy. Because of the unusual quantum confinement and enhanced surface effect of reduced-dimensional materials, traditional empirical models suffer from necessary but unreliable parameters extracted from previously-studied bulk materials. In this sense, quantitative, parameter-free approaches are highly useful for understanding properties of reduced-dimensional materials and, furthermore, predicting their novel applications. The first-principles density functional theory (DFT) is proven to be a reliable and convenient tool. In particular, recent progress in many-body perturbation theory (MBPT) makes it possible to calculate excited-state properties, e.g., quasiparticle (QP) band gap and optical excitations, by the first-principles approach based on DFT. Therefore, during my PhD study, I employed first-principles calculations based on DFT and MBPT to systematically study fundamental properties of typical reduced-dimensional semiconductors, i.e., the electronic structure, phonons, and optical excitations of core-shell nanowires (NWs) and graphene-like two-dimensional (2D) structures of current interests. First, I present first-principles studies on how to engineer band alignments of nano-sized radial heterojunctions, Si/Ge core-shell NWs. Our calculation reveals that band offsets in these one-dimensional (1D) nanostructures can be tailored by applying axial strain or varying core-shell sizes. In particular, the valence band offset can be efficiently tuned across a wide range and even be diminished via applied strain. Two mechanisms contribute to this tuning of band offsets. Furthermore, varying the

  17. Optical Enhancement in Optoelectronic Devices Using Refractive Index Grading Layers.

    PubMed

    Lee, Illhwan; Park, Jae Yong; Gim, Seungo; Kim, Kisoo; Cho, Sang-Hwan; Choi, Chung Sock; Song, Seung-Yong; Lee, Jong-Lam

    2016-02-10

    We enhanced the optical transmittance of a multilayer barrier film by inserting a refractive index grading layer (RIGL). The result indicates that the Fresnel reflection, induced by the difference of refractive indices between Si(x)N(y) and SiO2, is reduced by the RIGL. To eliminate the Fresnel reflection while maintaining high transmittance, the optimized design of grading structures with the RIGL was conducted using an optical simulator. With the RIGL, we achieved averaged transmittance in the visible wavelength region by 89.6%. It is found that the optimized grading structure inserting the multilayer barrier film has a higher optical transmittance (89.6%) in the visible region than that of a no grading sample (82.6%). Furthermore, luminance is enhanced by 14.5% (from 10,190 to 11,670 cd m(-2) at 30 mA cm(-2)) when the grading structure is applied to organic light-emitting diodes. Finally, the results offer new opportunities in development of multilayer barrier films, which assist industrialization of very cost-effective flexible organic electronic devices. PMID:26800204

  18. Tailoring nonlinear optical properties of Bi2Se3 through ion irradiation.

    PubMed

    Tan, Yang; Guo, Zhinan; Shang, Zhen; Liu, Fang; Böttger, Roman; Zhou, Shengqiang; Shao, Jundong; Yu, Xuefeng; Zhang, Han; Chen, Feng

    2016-01-01

    The nonlinear optical property of topological insulator bismuth selenide (Bi2Se3) is found to be well-tailored through ion irradiation by intentionally introducing defects. The increase of the optical modulation depth sensitively depends on the careful selection of the irradiation condition. By implementing the ion irradiated Bi2Se3 film as an optical saturable absorber device for the Q-switched wave-guide laser, an enhanced laser performance has been obtained including narrower pulse duration and higher peak power. Our work provides a new approach of tailoring the nonlinear optical properties of materials through ion irradiation, a well-developed chip-technology, which could find wider applicability to other layered two-dimensional materials beyond topological insulators, such as graphene, MoS2, black phosphours etc. PMID:26888223

  19. Tailoring nonlinear optical properties of Bi2Se3 through ion irradiation

    PubMed Central

    Tan, Yang; Guo, Zhinan; Shang, Zhen; Liu, Fang; Böttger, Roman; Zhou, Shengqiang; Shao, Jundong; Yu, Xuefeng; Zhang, Han; Chen, Feng

    2016-01-01

    The nonlinear optical property of topological insulator bismuth selenide (Bi2Se3) is found to be well-tailored through ion irradiation by intentionally introducing defects. The increase of the optical modulation depth sensitively depends on the careful selection of the irradiation condition. By implementing the ion irradiated Bi2Se3 film as an optical saturable absorber device for the Q-switched wave-guide laser, an enhanced laser performance has been obtained including narrower pulse duration and higher peak power. Our work provides a new approach of tailoring the nonlinear optical properties of materials through ion irradiation, a well-developed chip-technology, which could find wider applicability to other layered two-dimensional materials beyond topological insulators, such as graphene, MoS2, black phosphours etc. PMID:26888223

  20. Tailoring nonlinear optical properties of Bi2Se3 through ion irradiation

    NASA Astrophysics Data System (ADS)

    Tan, Yang; Guo, Zhinan; Shang, Zhen; Liu, Fang; Böttger, Roman; Zhou, Shengqiang; Shao, Jundong; Yu, Xuefeng; Zhang, Han; Chen, Feng

    2016-02-01

    The nonlinear optical property of topological insulator bismuth selenide (Bi2Se3) is found to be well-tailored through ion irradiation by intentionally introducing defects. The increase of the optical modulation depth sensitively depends on the careful selection of the irradiation condition. By implementing the ion irradiated Bi2Se3 film as an optical saturable absorber device for the Q-switched wave-guide laser, an enhanced laser performance has been obtained including narrower pulse duration and higher peak power. Our work provides a new approach of tailoring the nonlinear optical properties of materials through ion irradiation, a well-developed chip-technology, which could find wider applicability to other layered two-dimensional materials beyond topological insulators, such as graphene, MoS2, black phosphours etc.

  1. 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

  2. Polarisation properties of pulsars at optical wavelengths

    NASA Astrophysics Data System (ADS)

    Mignani, Roberto; Marelli, Martino; Shearer, Andrew; Slowikowska, Agnieszka

    2016-07-01

    Polarisation measurements of pulsars offer unique insights into their highly-magnetised relativistic environments and represent a primary test for neutron star magnetosphere models and radiation emission mechanisms. Besides the radio band, optical observations have been, so far, best suited to these goals, with polarisation measurements in the X-rays becoming possible in the near future thanks to missions, such as XIPE and IXPE. In this talk, we review the status of the optical polarisation measurements of pulsars and we foresee possible synergies between X-ray polarimetry observations of selected pulsars with, e.g XIPE and IXPE, and optical observations with the next generation of extremely large telescope, such as the E-ELT.

  3. Optical properties of blood in motion

    NASA Astrophysics Data System (ADS)

    Lindberg, Lars-Goeran; Sveider, Per; Oberg, P. Ake

    1992-08-01

    An in vitro model was developed for application in studies of the optical and physical characteristics of flowing blood in rigid and flexible tubes (artificial vessels). The results indicate that both transmission and reflection of light are dependent on blood volume changes, orientation as well as deformability of the red blood cells. Light transmission and reflection in human blood showed a parabolic behavior at hematocrit levels. > 38% when plotted against blood flow. At both a low and high flow rate, the light transmission increased when compared to an intermediate flow where the transmission showed a minimum. The optical wavelength used also affected the light transmission and reflection in moving blood. The results from studies of blood in flow-through models are of importance for the understanding of the optical mechanisms behind the signal generation in photometrical measurement techniques.

  4. Optical properties of blood in motion

    NASA Astrophysics Data System (ADS)

    Lindberg, Lars-Goran; Oberg, P. Ake

    1993-02-01

    An in vitro model is developed for application in studies of the optical and physical characteristics of flowing blood in rigid and flexible tubes (artificial vessels). The results indicate that both transmission and reflection of light are dependent on blood volume changes and orientation as well as the deformability of the red blood cells. Light transmission and reflection in human blood shows a parabolic behavior at hematocrit levels greater than 40%, when plotted against blood flow. At both low and high flow rates, the light transmission increases when compared to an intermediate flow where the transmission shows a minimum. The optical wavelength used also affects the light transmission and reflection in moving blood. The results of studies of blood in flow-through models are important for the understanding of the optical mechanisms behind the signal generation in photometrical measurement techniques.

  5. Optical Properties of Bismuth Germanate (BGO)

    SciTech Connect

    Jellison Jr, Gerald Earle; Auluck, S.; Singh, David J; Boatner, Lynn A

    2010-01-01

    The optical dielectric function of bismuth germanate Bi4Ge3O12 has been measured using spectroscopic ellipsometry and optical transmission. Analysis near the direct band edge indicates that there are at least three critical points at 4.44 low intensity and at 4.75 and 4.91 high intensity. Using transmission measurements, the band gap is determined to be 4.20 eV, which is likely determined by the defects in the material. Comparisons are made with relativistic electronic structure and optical calculations based on the Engel Vosko generalized gradient approximation. The near-absorption-edge critical points are associated with spin-orbit-split bands which significantly modify the conduction bands.

  6. Optical Properties of Small Ice Crystals with Black Carbon Inclusions

    NASA Astrophysics Data System (ADS)

    Yang, X.; Geier, M.; Arienti, M.

    2013-12-01

    The optical properties of ice crystals play a fundamental role in modeling atmospheric radiation and hydrological cycle, which are critical in monitoring climate change. While Black Carbon (BC) is recognized as the dominant absorber with positive radiative forcing (warming) (Ramanathan & Carmichael, 2008), in-situ observations (Cappa, et al, 2012) indicate that the characterization of the mixing state of BC with ice crystals and other non-BC particles in global climate models (Ghan & Schwartz, 2007) needs further investigation. The limitation in the available mixing models is due to the drastically different absorbing properties of BC compared to other aerosols. We explore the scattering properties of ice crystals (in shapes commonly found in cirrus clouds and contrails - Yang, et al. 2012) with the inclusion of BC particles. The Discrete Dipole Approximation (DDA) (Yurkin & Hoekstra, 2011) is utilized to directly calculate the optical properties of the crystals with multiple BC inclusions, modeled as a distribution of spheres. The results are then compared with the most popular models of internal and external mixing (Liou, et al. 2011). The DDA calculations are carried out over a broad range of BC particle sizes and volume fractions within the crystal at the 532 nm wavelength and for ice crystals smaller than 50 μm. The computationally intensive database generated in this study is critical for understanding the effect of different types of BC inclusions on the atmosphere radiative forcing. Examples will be discussed to illustrate the modification of BC optical properties by encapsulation in ice crystals and how the parameterization of the BC mixing state in global climate models can be improved. Acknowledgements Support by Sandia National Laboratories' LDRD (Laboratory Directed Research and Development) is gratefully acknowledged. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

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

    SciTech Connect

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

    2015-07-06

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

  10. Optical contrast enhancement of high-resolution ocular fundus imaging in vivo using polarimetry

    NASA Astrophysics Data System (ADS)

    Yang, Hansheng; Rao, Xuejun; Zhang, Yudong

    2007-11-01

    The adaptive optics (AO) retina imaging was performed with contrast enhancement by characterizing polarization parameters of the living retina. A removable pair of polarization state generating unit near the optical source and analysis unit near the CCD camera was incorporated into the basic 37-channle deformable mirror AO microscopic ophthalmoscope. Double-pass imaging polarimetry of the human eye was carried out, then incomplete Mueller matrix was calculated and analyzed to optimize the retina imaging condition using polarized light, which caused the subretinal structures with different polarization properties to emerge from the scattering light background, so the contrast of the image can be substantially enhanced. This method is demonstrated briefly and its validity was tested in the laboratory. The high-resolution images of ocular fundus are compared with 8-frame-averaging images we obtained prior to this method. The experiment results now show improved visualization of fundus structures to some extent without greatly sacrificing image resolution.

  11. Modification of alkali metals on silicon-based nanoclusters: An enhanced nonlinear optical response

    NASA Astrophysics Data System (ADS)

    Li, Xiaojun; Han, Quan; Yang, Xiaohui; Song, Ruijuan; Song, Limei

    2016-08-01

    Structures, chemical stabilities and nonlinear optical properties of alkali metals-adsorbed niobium-doped silicon (M@SinNb+) clusters are investigated using the DFT methods. The alkali metals prefer energetically to be attached as bridged bond rather than M-Si single bond in most of optimized structures. Adsorption of alkali metals on doped silicon clusters gradually enhances their chemical stabilities with increasing cluster size. Noteworthily, the first hyperpolarizabilities (βtot) of the M@SinNb+ clusters, obtained by using the long-range corrected CAM-B3LYP functional, are large enough to establish their strong nonlinear optical behavior, especially for M@Si9Nb+ (M = Li, Na, and K), and the enhanced βtot ordering by alkali metals is Na > K > Li.

  12. In-vivo local determination of tissue optical properties

    NASA Astrophysics Data System (ADS)

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

    1997-12-01

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

  13. In-vivo local determination of tissue optical properties

    NASA Astrophysics Data System (ADS)

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

    1998-01-01

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

  14. Tunable nonreciprocal terahertz transmission and enhancement based on metal/magneto-optic plasmonic lens.

    PubMed

    Fan, Fei; Chen, Sai; Wang, Xiang-Hui; Chang, Sheng-Jiang

    2013-04-01

    A tunable metal/magneto-optic plasmonic lens for terahertz isolator is demonstrated. Based on the magneto-optical effect of the semiconductor material and non-symmetrical structure, this plasmonic lens has not only the focusing feature but also nonreciprocal transmission property. Moreover, a transmission enhancement through this device greatly larger than that of the ordinary metallic slit arrays is contributed by the extraordinary optical transmission effect of the magneto surface plasmon polaritons. The results show that the proposed isolator has an isolation bandwidth of larger than 0.4THz and the maximum isolation of higher than 110dB, and its operating frequency also can be broadly tuned by changing the external magnetic field or temperature. This low-loss, high isolation, broadband tunable nonreciprocal terahertz transmission mechanism has a great potential for terahertz application systems. PMID:23571951

  15. Functionality Enhancement of Industrialized Optical Fiber Sensors and System Developed for Full-Scale Pavement Monitoring

    PubMed Central

    Wang, Huaping; Liu, Wanqiu; He, Jianping; Xing, Xiaoying; Cao, Dandan; Gao, Xipeng; Hao, Xiaowei; Cheng, Hongwei; Zhou, Zhi

    2014-01-01

    Pavements always play a predominant role in transportation. Health monitoring of pavements is becoming more and more significant, as frequently suffering from cracks, rutting, and slippage renders them prematurely out of service. Effective and reliable sensing elements are thus in high demand to make prognosis on the mechanical properties and occurrence of damage to pavements. Therefore, in this paper, various types of functionality enhancement of industrialized optical fiber sensors for pavement monitoring are developed, with the corresponding operational principles clarified in theory and the performance double checked by basic experiments. Furthermore, a self-healing optical fiber sensing network system is adopted to accomplish full-scale monitoring of pavements. The application of optical fiber sensors assembly and self-healing network system in pavement has been carried out to validate the feasibility. It has been proved that the research in this article provides a valuable method and meaningful guidance for the integrity monitoring of civil structures, especially pavements. PMID:24854060

  16. 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.

  17. 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.

  18. Optomechanical Enhancement of Doubly Resonant 2D Optical Nonlinearity.

    PubMed

    Yi, Fei; Ren, Mingliang; Reed, Jason C; Zhu, Hai; Hou, Jiechang; Naylor, Carl H; Johnson, A T Charlie; Agarwal, Ritesh; Cubukcu, Ertugrul

    2016-03-01

    Emerging two-dimensional semiconductor materials possess a giant second order nonlinear response due to excitonic effects while the monolayer thickness of such active materials limits their use in practical nonlinear devices. Here, we report 3300 times optomechanical enhancement of second harmonic generation from a MoS2 monolayer in a doubly resonant on-chip optical cavity. We achieve this by engineering the nonlinear light-matter interaction in a microelectro-mechanical system enabled optical frequency doubling device based on an electrostatically tunable Fabry-Perot microresonator. Our versatile optomechanical approach will pave the way for next generation efficient on-chip tunable light sources, sensors, and systems based on molecularly thin materials. PMID:26854706

  19. Enhancement of upconversion deep-tissue imaging using optical clearing

    NASA Astrophysics Data System (ADS)

    Popov, A. P.; Khaydukov, E. V.; Bykov, A. V.; Semchishen, V. A.; Tuchin, V. V.

    2015-07-01

    We report on the deep-tissue imaging using novel upconversion nanoparticles (UCNPs) β-NaYF4:Yb3+ ,Tm3+ (excitation wavelength: 975 nm, detection wavelength: 800 nm) and glycerol as an optical clearing agent to enhance imaging from under 6-mm-thick porcine muscle tissue samples. We show that improvement of luminescent label visualization is caused by transforming of the diffuse label-emitted light into the direct component. This results in the increase in visibility (ratio of the sum and difference of the maximal and minimal intensity) of the label and increase in maximal signal intensity thus making the combination of the phosphors and optical clearing promising for precise detection of tissue-embedded labelled inhomogeneities.

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

    PubMed

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

    2016-01-01

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

  1. Silver nanoparticles grown in organic solvent PGMEA by pulsed laser ablation and their nonlinear optical properties.

    PubMed

    Shi, Hongfei; Wang, Can; Zhou, Yueliang; Jin, Kuijuan; Yang, Guozhen

    2012-10-01

    Well dispersed silver nanoparticles (AgNPs) with narrow size distribution have been grown in organic solvent propylene glycol monomethyl ether acetate (PGMEA) by pulsed laser ablation techniques. The presence of AgNPs in PGMEA solvent gives rise to an enhancement of the absorption and nonlinear optical properties due to the surface plasmon resonance induced by AgNPs. The shape and density of the AgNPs have been estimated by fitting the absorption spectra with a given model, and the results also show that an additional laser irradiation treatment can improve the monodispersity of the AgNPs and their nonlinear optical properties. The synthesis of AgNPs in PGMEA will facilitate adding AgNPs into organic functional materials especially for photoresist to modify their optical properties. PMID:23421153

  2. Distinct optical properties of relativistically degenerate matter

    NASA Astrophysics Data System (ADS)

    Akbari-Moghanjoughi, M.

    2014-06-01

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

  3. Distinct optical properties of relativistically degenerate matter

    SciTech Connect

    Akbari-Moghanjoughi, M.

    2014-06-15

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

  4. Optically enhanced nuclear cross polarization in acridine-doped fluorene

    SciTech Connect

    Oshiro, C.M.

    1982-06-01

    The objective of this work has been to create large polarizations of the dilute /sup 13/C nuclei in the solid state. The idea was to create /sup 1/H polarizations larger than Boltzmann and to use the proton enhanced nuclear induction spectroscopy cross polarization technique to then transfer this large polarization to the /sup 13/C spin system. Optical Nuclear Polarization (ONP) of acridine-doped fluorene single crystals was studied. In addition, ONP of powdered samples of the acridine-doped fluorene was studied. In general, many compounds do not crystallize easily or do not form large crystals suitable for NMR experiments. Powdered, amorphous and randomly dispersed samples are generally far more readily available than single crystals. One objective of this work has been to (first) create large /sup 1/H polarizations. Although large optical proton polarizations in single crystals have been reported previously, optically generated polarizations in powdered samples have not been reported. For these reasons, ONP studies of powdered samples of the acridine-doped fluorene were also undertaken. Using ONP in combination with the proton enhanced nuclear induction spectroscopy experiment, large /sup 13/C polarizations have been created in fluorene single crystals. These large /sup 13/C polarizations have permitted the determination of the seven incongruent chemical shielding tensors of the fluorene molecule. Part 2 of this thesis describes the proton enhanced nuclear induction spectroscopy experiment. Part 3 describes the ONP experiment. Part 4 is a description of the experimental set-up. Part 5 describes the data analysis for the determination of the chemical shielding tensors. Part 6 presents the results of the ONP experiments performed in this work and the chemical shielding tensors determined.

  5. Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Siller, Brian; Mills, Andrew; Porambo, Michael; McCall, Benjamin

    2011-06-01

    The technique of Cavity Enhanced Velocity Modulation Spectroscopy (CEVMS) has recently been developed. By demodulating the detector signal at twice the plasma modulation frequency (2f), the velocity-modulated ionic absorption signal can be extracted. Although the concentration-modulated excited neutral molecules are also observed at 2f, the ion and neutral signals can be distinguished and separated with phase-sensitive demodulation. The optical cavity provides two major benefits. It increases both the optical path length and the intracavity laser power by a factor of 2×Finesse/π. The multipass advantage allows for much longer path length than was previously possible with unidirectional multipass White cells. The power enhancement combined with perfectly overlapped counterpropagating beams within the cavity allows for sub-Doppler spectroscopy. Although CEVMS showed much potential, its sensitivity was ultimately limited by electronic noise from the plasma interfering with the cavity-locking electronics. We have further improved upon CEVMS by combining it with Noise Immune Cavity Enhanced Optical Heterodyne Molecular Spectroscopy (NICE-OHMS). The laser is frequency modulated at precisely an integer multiple of the free spectral range of the optical cavity; this allows the heterodyne sidebands to be coupled into the optical cavity. Heterodyne detection of the cavity leak-out is immune to noise in the laser-cavity lock, and 2f demodulation further decreases electronic noise in the system and retains ion-neutral discrimination. The additional level of modulation beyond ordinary CEVMS has the added advantage of enabling the observation of both absorption and dispersion signals simultaneously by using two RF mixers, each driving its own lock-in amplifier. In a single scan, four distinct signals can be obtained: absorption and dispersion for ions and excited neutrals. The technique has been demonstrated in the near-IR for N_2^+. B. M. Siller, A. A. Mills and B. J. Mc

  6. Optical and Transport Properties of Organic Molecules: Methods and Applications

    NASA Astrophysics Data System (ADS)

    Strubbe, David Alan

    -harmonic generation with TDDFT with a real-space grid, finding good agreement with calculations using localized bases and with experimental measurements, and that the response is very long-ranged in space. 5. N C 60 is an endohedral fullerene, a sphere of carbon containing a single N atom inside, which is weakly coupled electronically. I show with TDDFT calculations that a laser pulse can excite the vibrational mode of this N atom, transiently turning on and off the system's ability to undergo second-harmonic generation. The calculated susceptibility is as large as some commercially used frequency-doubling materials. 6. A crucial question in understanding experimental measurements of nonlinear optics and their relation to device performance is the effect of the solution environment on the properties of the isolated molecules. I will consider possible explanations for the large enhancement of the hyperpolarizability of chloroform in solution, demonstrate an ab initio method of calculating electrostatic effects with local-field factors, and derive the equations necessary for a full calculation of liquid chloroform. 7. Many-body perturbation theory, in the GW approximation for quasiparticle band-structure and Bethe-Salpeter equation for optical properties, is a powerful method for calculations in solids, nanostructures, and molecules. The BerkeleyGW code is a freely available implementation of this methodology which has been extensively tested and efficiently parallelized for use on large systems. 8. Molecular junctions, in which a single molecule is contacted to two metallic leads, are interesting systems for studying nanoscale transport. I will present a method called DFT+Sigma which approximates many-body perturbation theory to enable accurate and efficient calculations of the conductance of these systems. 9. Azobenzene is a molecule with the unusual property that it can switch reversible between two different geometries, cis and trans, upon absorption of light. I have calculated the

  7. 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...

  8. 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...

  9. Optical enhancement of photoluminescence with colloidal quantum dots

    NASA Astrophysics Data System (ADS)

    Abraham, Gabrielle; French, David A.; Bajwa, Pooja; Heyes, Colin D.; Herzog, Joseph B.

    2015-08-01

    This work investigates colloidal, semiconductor Cadmium Selenide (CdSe) QDs with optical spectroscopy measurements. A custom-built microscope has been used for photoluminescence spectroscopy and has collected images, videos, and spectra of samples to study the effects of substrates, sample density, uniformity, and QD aging with time. This set up will be used to detect single to a few molecules, shown by fluorescent intermittency, or QD blinking. Differences in the spectrum will be noted as related to the age of samples, the density of the quantum dots, and the concentration of samples. Further experiments include the potential plasmonic enhancement of QD photoluminescence by gold nanoparticles or nanostructures.

  10. Nonlinear-optical, optical, and crystallographic properties of methyl p-hydroxybenzoate

    NASA Astrophysics Data System (ADS)

    Li, Zhengdong; Wu, Baichang; Su, Genbo

    1997-07-01

    Bulk crystals of methyl p-hydroxybenzoate were grown from organic solution. The crystal structure was determined by X-ray analysis. The refractive indices were determined by the method of prism minimum deviation. The nonlinear-optical coefficients dij and deff were measured. The nonlinear-optical properties are discussed in terms of crystalline structure.

  11. Growth, Optical Properties, and Optimization of Infrared Optoelectronic Materials

    NASA Astrophysics Data System (ADS)

    Webster, Preston Thomas

    High-performance III-V semiconductors based on ternary alloys and superlattice systems are fabricated, studied, and compared for infrared optoelectronic applications. InAsBi is a ternary alloy near the GaSb lattice constant that is not as thoroughly investigated as other III-V alloys and that is challenging to produce as Bi has a tendency to surface segregate and form droplets during growth rather than incorporate. A growth window is identified within which high-quality droplet-free bulk InAsBi is produced and Bi mole fractions up to 6.4% are obtained. Photoluminescence with high internal quantum efficiency is observed from InAs/InAsBi quantum wells. The high structural and optical quality of the InAsBi materials examined demonstrates that bulk, quantum well, and superlattice structures utilizing InAsBi are an important design option for efficient infrared coverage. Another important infrared material system is InAsSb and the strain-balanced InAs/InAsSb superlattice on GaSb. Detailed examination of X-ray diffraction, photoluminescence, and spectroscopic ellipsometry data provides the temperature and composition dependent bandgap of bulk InAsSb. The unintentional incorporation of approximately 1% Sb into the InAs layers of the superlattice is measured and found to significantly impact the analysis of the InAs/InAsSb band alignment. In the analysis of the absorption spectra, the ground state absorption coefficient and transition strength of the superlattice are proportional to the square of the electron-hole wavefunction overlap; wavefunction overlap is therefore a major design parameter in terms of optimizing absorption in these materials. Furthermore in addition to improvements through design optimization, the optical quality of the materials studied is found to be positively enhanced with the use of Bi as a surfactant during molecular beam epitaxy growth. A software tool is developed that calculates and optimizes the miniband structure of semiconductor

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

    PubMed

    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. PMID:26986473

  13. 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.

  14. Multiparameter fiber optic sensing system for monitoring enhanced geothermal systems

    SciTech Connect

    Challener, William A

    2014-12-04

    The goal of this project was to design, fabricate and test an optical fiber cable which supports multiple sensing modalities for measurements in the harsh environment of enhanced geothermal systems. To accomplish this task, optical fiber was tested at both high temperatures and strains for mechanical integrity, and in the presence of hydrogen for resistance to darkening. Both single mode (SM) and multimode (MM) commercially available optical fiber were identified and selected for the cable based on the results of these tests. The cable was designed and fabricated using a tube-within-tube construction containing two MM fibers and one SM fiber, and without supporting gel that is not suitable for high temperature environments. Commercial fiber optic sensing instruments using Raman DTS (distributed temperature sensing), Brillouin DTSS (distributed temperature and strain sensing), and Raleigh COTDR (coherent optical time domain reflectometry) were selected for field testing. A microelectromechanical systems (MEMS) pressure sensor was designed, fabricated, packaged, and calibrated for high pressure measurements at high temperatures and spliced to the cable. A fiber Bragg grating (FBG) temperature sensor was also spliced to the cable. A geothermal well was selected and its temperature and pressure were logged. The cable was then deployed in the well in two separate field tests and measurements were made on these different sensing modalities. Raman DTS measurements were found to be accurate to ±5°C, even with some residual hydrogen darkening. Brillouin DTSS measurements were in good agreement with the Raman results. The Rayleigh COTDR instrument was able to detect some acoustic signatures, but was generally disappointing. The FBG sensor was used to determine the effects of hydrogen darkening, but drift over time made it unreliable as a temperature or pressure sensor. The MEMS sensor was found to be highly stable and accurate to better than its 0.1% calibration.

  15. Enhanced optical chromatography in a PDMS microfluidic system

    NASA Astrophysics Data System (ADS)

    Terray, A.; Arnold, J.; Hart, S. J.

    2005-12-01

    The purely refractive index driven separation of uniformly sized polystyrene, n = 1.59 and poly(methylmethacrylate), n = 1.49 in an optical chromatography system has been enhanced through the incorporation of a custom poly(dimethysiloxane) (PDMS) microfluidic system. A customized channel geometry was used to create separate regions with different linear flow velocities tailored to the specific application. These separate flow regions were then used to expose the entities in the separation to different linear flow velocities thus enhancing their separation relative to the same separation in a constant velocity flow environment. A microbiological sample containing spores of the biological warfare agent, Bacillus anthracis, and a common environmental interferent, mulberry pollen, was investigated to test the use of tailored velocity regions. These very different samples were analyzed simultaneously only through the use of tailored velocity regions.

  16. Surface-Enhanced Raman Optical Data Storage system

    DOEpatents

    Vo-Dinh, T.

    1991-03-12

    A method and apparatus for a Surface-Enhanced Raman Optical Data Storage (SERODS) System are disclosed. A medium which exhibits the Surface Enhanced Raman Scattering (SERS) phenomenon has data written onto its surface of microenvironment by means of a write-on procedure which disturbs the surface or microenvironment of the medium and results in the medium having a changed SERS emission when excited. The write-on procedure is controlled by a signal that corresponds to the data to be stored so that the disturbed regions on the storage device (e.g., disk) represent the data. After the data is written onto the storage device it is read by exciting the surface of the storage device with an appropriate radiation source and detecting changes in the SERS emission to produce a detection signal. The data is then reproduced from the detection signal. 5 figures.

  17. Surface-enhanced raman optical data storage system

    DOEpatents

    Vo-Dinh, Tuan

    1991-01-01

    A method and apparatus for a Surface-Enhanced Raman Optical Data Storage (SERODS) System is disclosed. A medium which exhibits the Surface Enhanced Raman Scattering (SERS) phenomenon has data written onto its surface of microenvironment by means of a write-on procedure which disturbs the surface or microenvironment of the medium and results in the medium having a changed SERS emission when excited. The write-on procedure is controlled by a signal that corresponds to the data to be stored so that the disturbed regions on the storage device (e.g., disk) represent the data. After the data is written onto the storage device it is read by exciting the surface of the storage device with an appropriate radiation source and detecting changes in the SERS emission to produce a detection signal. The data is then reproduced from the detection signal.

  18. Optical communication technology. II - Properties of optical fibers

    NASA Astrophysics Data System (ADS)

    1980-07-01

    The pulse dispersion of short light impulses is examined with respect to mode, waveguides, and material and profile dispersion. Impulse expansions of up to 50 ns/km are measured and equations for calculating light impulses from fiber length and light speed in vacuum are presented, together with equations of refraction profiles and profile patterns. Attention is given to multimode-step index fibers, gradient fibers, and monomode fibers as well as to their differing properties. Diagrams of numerical aperture, light dispersion (of the above mentioned fiber types), and interference of two waveguides are given.

  19. Magneto-Optical Properties of Paramagnetic Superrotors

    NASA Astrophysics Data System (ADS)

    Milner, A. A.; Korobenko, A.; Floß, J.; Averbukh, I. Sh.; Milner, V.

    2015-07-01

    We study the dynamics of paramagnetic molecular superrotors in an external magnetic field. An optical centrifuge is used to create dense ensembles of oxygen molecules in ultrahigh rotational states. In is shown, for the first time, that the gas of rotating molecules becomes optically birefringent in the presence of a magnetic field. The discovered effect of "magneto-rotational birefringence" indicates the preferential alignment of molecular axes along the field direction. We provide an intuitive qualitative model, in which the influence of the applied magnetic field on the molecular orientation is mediated by the spin-rotation coupling. This model is supported by the direct imaging of the distribution of molecular axes, the demonstration of the magnetic reversal of the rotational Raman signal, and by numerical calculations.

  20. Magneto-Optical Properties of Paramagnetic Superrotors.

    PubMed

    Milner, A A; Korobenko, A; Floß, J; Averbukh, I Sh; Milner, V

    2015-07-17

    We study the dynamics of paramagnetic molecular superrotors in an external magnetic field. An optical centrifuge is used to create dense ensembles of oxygen molecules in ultrahigh rotational states. In is shown, for the first time, that the gas of rotating molecules becomes optically birefringent in the presence of a magnetic field. The discovered effect of "magneto-rotational birefringence" indicates the preferential alignment of molecular axes along the field direction. We provide an intuitive qualitative model, in which the influence of the applied magnetic field on the molecular orientation is mediated by the spin-rotation coupling. This model is supported by the direct imaging of the distribution of molecular axes, the demonstration of the magnetic reversal of the rotational Raman signal, and by numerical calculations. PMID:26230789

  1. Optical properties of Rydberg excitons and polaritons

    NASA Astrophysics Data System (ADS)

    Zielińska-Raczyńska, Sylwia; Czajkowski, Gerard; Ziemkiewicz, David

    2016-02-01

    We show how to compute the optical functions when Rydberg excitons appear, including the effect of the coherence between the electron-hole pair and the electromagnetic field. We use the real density matrix approach (RDMA), which, combined with the Green's function method, enables one to derive analytical expressions for the optical functions. Choosing the susceptibility, we performed numerical calculations appropriate to a Cu20 crystal, being a semiconductor with an indirect gap. The effect of the coherence is displayed in the line shape. We also examine in detail and explain the dependence of the oscillator strength and the resonance placement on the state number. We report good agreement with recently published experimental data. We also show that the presented method can be applied to semiconductors with a direct gap.

  2. Plastic optical fibers: properties and practical applications

    NASA Astrophysics Data System (ADS)

    Loch, Manfred, Jr.

    2004-10-01

    Driven by the increasing data traffic and the increasing demand for bandwidth optical fiber technologies play a greater role in todays and future data-communication networks. Although the well-known silica fiber have the potential of achieving very large bandwidth, this fiber is not the ideal medium for high bit rate data-communication for office and home applications because its small dimension requires well sophisticated components as well as installation technologies. This increases the total system cost, inevitably. However, the technologies of plastic (polymer) optical fibers (POF) and the devices for POF nowadays show rapid process /2/. So, we could benefit from the special advantages of these fibers over a wide field of applications, from decoration to local networks, including lighting, image guides and sensor technique. Today, inexpensive and robust POF transmission systems are available on the market with high bit rate capacity. Bus-systems, e.g. MOST and Byteflight, are applied in the rough automotive environment.

  3. Enhanced optical limiting effects of graphene materials in polyimide

    SciTech Connect

    Gan, Yao; Feng, Miao; Zhan, Hongbing

    2014-04-28

    Three different graphene nanostructure suspensions of graphene oxide nanosheets (GONSs), graphene oxide nanoribbons (GONRs), and graphene oxide quantum dots (GOQDs) are prepared and characterized. Using a typical two-step method, the GONSs, GONRs, and GOQDs are incorporated into a polyimide (PI) matrix to synthesize graphene/PI composite films, whose nonlinear optical (NLO) and optical limiting (OL) properties are investigated at 532 nm in the nanosecond regime. The GONR suspension exhibits superior NLO and OL effects compared with those of GONSs and GOQDs because of its stronger nonlinear scattering and excited-state absorption. The graphene/PI composite films exhibit NLO and OL performance superior to that of their corresponding suspensions, which is attributed primarily to a combination of nonlinear mechanisms, charge transfer between graphene materials and PI, and the matrix effect.

  4. Optical diffusion property of chicken tissue

    NASA Astrophysics Data System (ADS)

    Schneider, Patricia S.; Flamholz, Alex; Wong, Peter K.; Lieberman, David H.; Cheung, Tak D.; Itoka, Harriet; Minott, Troy; Quizhpi, Janie; Rodriguez, Jacquelin

    2004-11-01

    Chicken tissue acts as a turbid medium in optical wavelength. Optical characterization data of fresh chicken dark and white meat were studied using the theory of light diffusion. The gaussian-like transmission profile was used to determine the transport mean free path and absorption. The refractive index, a fundamental parameter, was extracted via transmission correlation function analysis without using index-matching fluid. The variation in refractive index also produced various small shifts in the oscillatory feature of the intensity spatial correlation function at distance shorter than the transport mean free path. The optical system was calibrated with porous silicate slabs containing different water contents and also with a solid alumina slab. The result suggested that the selective scattering/absorption of myoglobin and mitochondria in the dark tissues is consistent with the transmission data. The refractive index was similar for dark and white tissues at the He-Ne wavelength and suggested that the index could serve as a marker for quality control. Application to chicken lunchmeat samples revealed that higher protein and lower carbohydrate would shift the correlation toward smaller distance. The pure fat refractive index was different from that of the meat tissue. Application of refractive index as a fat marker is also discussed

  5. Core-shell potassium niobate nanowires for enhanced nonlinear optical effects

    NASA Astrophysics Data System (ADS)

    Richter, J.; Steinbrück, A.; Zilk, M.; Sergeyev, A.; Pertsch, T.; Tünnermann, A.; Grange, R.

    2014-04-01

    We demonstrate the synthesis as well as the optical characterization of core-shell nanowires. The wires consist of a potassium niobate (KNbO3) core and a gold shell. The nonlinear optical properties of the core are combined with the plasmonic resonance of the shell and offer an enhanced optical signal in the near infrared spectral range. We compare two different functionalization schemes of the core material prior to the shell growth process: silanization and polyelectrolyte. We show that the latter leads to a smoother and complete core-shell nanostructure and an easier-to-use synthesis process. A Mie-theory based theoretical approach is presented to model the enhanced second-harmonic generated (SHG) signal of the core-shell wires, illustrating the influence of the fabrication-induced varying geometrical factors of wire radius and shell thickness. A spectroscopic measurement on a core-shell nanowire shows a strong localized surface plasmon resonance close to 900 nm, which matches with the SHG resonance obtained from nonlinear optical experiments with the same nanowire. According to the simulation, this corresponds to a wire radius of 35 nm and a shell thickness of 7.5 nm. By comparing SHG signals measured from an uncoated nanowire and the coated one, we obtain a 250 times enhancement factor. This is less than the calculated enhancement, which considers a cylindrical nanowire with a perfectly smooth shell. Thus, we explain this discrepancy mainly with the roughness of the synthesized gold shell.We demonstrate the synthesis as well as the optical characterization of core-shell nanowires. The wires consist of a potassium niobate (KNbO3) core and a gold shell. The nonlinear optical properties of the core are combined with the plasmonic resonance of the shell and offer an enhanced optical signal in the near infrared spectral range. We compare two different functionalization schemes of the core material prior to the shell growth process: silanization and polyelectrolyte

  6. Optical properties of Li-doped ZnO films

    NASA Astrophysics Data System (ADS)

    Valentini, Antonio; Quaranta, Fabio; Vasanelli, Lorenzo; Piccolo, R.

    1991-03-01

    The difficulty to achieve a refractive index matching between active substrate and active layer grown on, is one of the main problem in integrated optical devices based on gallium arsenide, because of its high refractive index value. One possible solution could be an active layer whose refractive index is variable during the grown. Zinc oxide is a very interesting material because of its electro-optic and acousto- optic properties. It has a low cost and can be prepared by a variety of techniques. In this paper deposition of lithium doped zinc oxide films by reactive sputtering has been investigated in order to study the dependence of optical properties on lithium content and deposition parameters. A ZnO:Li target was used. The film depositions were performed varying the oxygen content in sputtering gas. For comparison undoped ZnO films were also prepared. We have performed optical and electrical measurement on films relating the results to Li contents and O/Zn ratio obtained by nuclear reaction and Rutherford backscattering measurements respectively. The film analysis has shown that dopant concentration is mainly controlled by gas mixture. The optical properties are dependent on deposition conditions. Optical waveguides have been prepared and characterized. The results are presented and discussed.

  7. 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

  8. Magnetic and optical properties of nanocorrugated Co films

    SciTech Connect

    Sapozhnikov, M. V.; Gusev, S. A.; Rogov, V. V.; Ermolaeva, O. L.; Troitskii, B. B.; Khokhlova, L. V.; Smirnov, D. A.

    2010-03-22

    Nanostructured Co films were prepared on the top of a polymethyl methacrylate (PMMA) colloidal crystals by magnetron sputtering. Optical reflectance spectra were studied in the range of near UV, IR, and visible light for p- and s-polarizations. Valleys were observed in the spectra and their positions scaled with the PMMA sphere diameter. Both the surface plasmon resonance and the dipole resonance of single Co nanocaps should be considered to explain the obtained results. Magneto-optic measurements showed the qualitative change of the magnetization curve and the enhancement of magneto-optic rotation at wavelength lambda=632 nm in comparison with the control Co film.

  9. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, Uthamalingam

    1995-01-01

    A composition and method of preparing YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T.sub.c. About 5-20% additions give rise to substantially improved mechanical properties.

  10. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, U.

    1995-04-25

    A composition and method are disclosed of preparing YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T{sub c}. About 5-20% additions give rise to substantially improved mechanical properties.

  11. REVIEW ARTICLE: Slow light enhanced nonlinear optics in periodic structures

    NASA Astrophysics Data System (ADS)

    Monat, C.; de Sterke, M.; Eggleton, B. J.

    2010-10-01

    We review recent advances related to slow light in periodic structures, where the refractive index varies along one or two directions, i.e. gratings and planar photonic crystals. We focus on how these geometries are conducive to enhancing the nonlinear interaction between light and matter. We describe the underlying theory developed for shallow gratings, but whose conclusions can be extended to planar photonic crystal waveguides, in particular the enhancement of third-order nonlinear processes with slow light. We review some experiments showing how gratings have been used for pulse compression and the generation of slow gap solitons. We then present recent nonlinear experiments performed in photonic crystal waveguides that demonstrate the strong reinforcement of nonlinear third-order optical phenomena with slow light. We discuss the challenges associated with slow light in these 2D structures and their unique advantage—dispersion engineering—for creating broadband nonlinear devices for all-optical signal processing. By breaking down the relation between dispersion and group velocity imposed in gratings, these structures also offer new opportunities for generating soliton-like effects over short length scales, at low powers and with short pulses.

  12. Optical cavity integrated surface ion trap for enhanced light collection

    NASA Astrophysics Data System (ADS)

    Benito, Francisco M.

    Ion trap systems allow the faithful storage and manipulation of qubits encoded in the energy levels of the ions, and can be interfaced with photonic qubits that can be transmitted to connect remote quantum systems. Single photons transmitted from two remote sites, each entangled with one quantum memory, can be used to entangle distant quantum memories by interfering on a beam splitter. Efficient remote entanglement generation relies upon efficient light collection from single ions into a single mode fiber. This can be realized by integrating an ion trap with an optical cavity and employing the Purcell effect for enhancing the light collection. Remote entanglement can be used as a resource for a quantum repeater for provably secure long-distance communication or as a method for communicating within a distributed quantum information processor. We present the integration of a 1 mm optical cavity with a micro-fabricated surface ion trap. The plano-concave cavity is oriented normal to the chip surface where the planar mirror is attached underneath the trap chip. The cavity is locked using a 780 nm laser which is stabilized to Rubidium and shifted to match the 369 nm Doppler transition in Ytterbium. The linear ion trap allows ions to be shuttled in and out of the cavity mode. The Purcell enhancement of spontaneous emission into the cavity mode would then allow efficient collection of the emitted photons, enabling faster remote entanglement generation.

  13. Nano-enhanced optical delivery into targeted cells (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wright, Weldon; Pradhan, Sanjay

    2016-03-01

    Nano-enhanced optical field of gold nanoparticles allowed the use of a continuous wave (cw) laser beam for efficient delivery of exogenous impermeable materials into targeted cells. Using this Nano-enhanced Optical Delivery (NOD) method, we show that large molecules could be delivered with low power cw laser with exposure time ~ 1sec. At such low power (and exposure), the non-targeted cells (not bound to gold nanoparticles) were not adversely affected by the laser beam. Further, by varying the size of the gold nanoparticles, cells could be exclusively sensitized to selective wavelengths of laser beam. In contrast other nanoparticles, gold nanoparticles were found to have lower cytotoxicity, making it better suited for clinical NOD. Further, as compared with pulsed lasers, cw (diode) lasers are compact, easy-to-use and therefore, NOD using cw laser beam has significant translational potential for delivery of impermeable bio-molecules to tissues in different organs. We will present optimization of NOD parameters for delivering different molecules to different cells. Success of this NOD method may lead to a new clinical approach for treating AMD and RP patients with geographic atrophy in retina.

  14. Structural elucidation, optical, magnetic and nonlinear optical properties of oxystyryl dyes.

    PubMed

    Koleva, Bojidarka B; Stoyanov, Stanimir; Kolev, Tsonko; Petkov, Ivan; Spiteller, Michael

    2009-01-01

    Structure, magnetic and optical properties of tetraphenylborate salts of 2,5-[1-methyl-4-[2-(4-hydroxyphenyl)ethenyl]piridinium]-propane and butane are performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV-vis and fluorescence methods, HPLC tandem ESI mess spectrometry (MS/MS), (1)H, (13)C and (1)H-(1)H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are used for performing of the structures, optical and nonlinear optical properties of the studied compounds. PMID:18722806

  15. Structural elucidation, optical, magnetic and nonlinear optical properties of oxystyryl dyes

    NASA Astrophysics Data System (ADS)

    Koleva, Bojidarka B.; Stoyanov, Stanimir; Kolev, Tsonko; Petkov, Ivan; Spiteller, Michael

    2009-01-01

    Structure, magnetic and optical properties of tetraphenylborate salts of 2,5-[1-methyl-4-[2-(4-hydroxyphenyl)ethenyl]piridinium]-propane and butane are performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV-vis and fluorescence methods, HPLC tandem ESI mess spectrometry (MS/MS), 1H, 13C and 1H- 1H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are used for performing of the structures, optical and nonlinear optical properties of the studied compounds.

  16. 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.

  17. Electrodeposited CdTe{emdash}optical properties

    SciTech Connect

    Rakhshani, A.E.

    1997-06-01

    For the measurement of optical constants, the electrodeposited films of CdTe were lifted off their opaque substrates and transferred onto glass slides using a transparent liquid adhesive. This technique proved to give results more reliable than those obtained on samples in which CdTe is deposited on CdS-coated conducting glass. The measured optical dispersion in the photon energy range of E{lt}1.5eV is in excellent agreement with that for the single crystal. The optical absorption coefficient was determined in the E{lt}3.5eV range and was compared with that for the single crystal. The results revealed two direct allowed transitions at 1.50 eV [{Gamma}{sub 8}valenceband(VB){r_arrow}{Gamma}{sub 6}conductionband(CB)] and 2.43 eV [{Gamma}{sub 7}(VB){r_arrow}{Gamma}{sub 6}(CB)] and three indirect allowed transitions at 1.27 eV [L{sub 4,5}(VB){r_arrow}{Gamma}{sub d}], 1.83 eV [L{sub 6}(VB){r_arrow}{Gamma}{sub d}], and 2.84 eV [{Gamma}{sub 8}(VB){r_arrow}L{sub 6}(CB)]. The 1.27 and the 1.83 eV transitions, which have not been reported previously and were not detected in single-crystal data, are attributed to the transitions to a grain-boundary-related defect energy band {Gamma}{sub d}, 0.65 eV above {Gamma}{sub 8} (VB). The indirect transitions at 1.83 and 2.84 eV are assisted by phonons having energies of 80 and 84 meV, respectively. {copyright} {ital 1997 American Institute of Physics.}

  18. 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.

  19. Optical Properties and Aggregation of Graphene Nanoplatelets.

    PubMed

    Melezhyk, A V; Kotov, V A; Tkachev, A G

    2016-01-01

    In the present paper, the optical density of dispersions of randomly oriented multilayer graphene nanoplatelets (GNPs) was estimated. Calculated and experimental data were compared for aqueous GNP dispersions stabilized with various surfactants. It was shown that the sonication of an expanded graphite compound (EGC) in aqueous surfactant solutions leads to the transformation of EGC worm-like particles into weak GNP aggregates which are able to pass into solution upon dilution and agitation of the system. They may be filtered and washed out of surfactants. The concentrated GNP dispersions containing these weak aggregates can be used to synthesize different graphene-based nanostructures and obtain novel composite materials. PMID:27398570

  20. 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.

  1. The optical properties of YBCO thin films

    NASA Astrophysics Data System (ADS)

    Wallace, Roger James

    We present strong evidence that there is no specific mid- infrared absorption band in YBCO and a generalised Drude model can be used to explain all of the observed features in the optical spectrum. A high vacuum, low temperature ATR experiment has been used to excite surface plasmons (SPP) on YBCO thin films at different temperatures. We have found that the SPP resonance condition varies systematically with temperature. The temperature dependent dielectric function and optical conductivity of YBCO at 2984nm have been determined. We have shown that the renal and imaginary dielectric function of YBCO, ~ɛ= ɛ1 + iɛ2, at 2984nm, are linearly dependent on temperature: ɛ1(T) = -52 + 0.008T and ɛ1(T) = 4 + 0.1T. We have calculated the optical conductivity, σ(T), and the normal reflectance, ℜ(T): σ(T) = 196 + 4.9T and ℜ(T) = 0.99-7.4 × 10-4T, where temperature is in kelvin and the conductivity is in Ω-1 cm-1. A generalised Drude model has been used to analyse our results. The generalised Drude memory function, M = 1//tau + i/omega/lambda, has been calculated as a function of temperature. The parameters 1/τ and λ can be approximated by 1/τ(T) = 50 + 6.6T and 1 + λ(T) ≅ 1.48 - 0.003T +.35 × 10-5T. These expressions are valid between 100K and 300K. An optical technique for determining the thickness of YBCO thin films has been developed. It has been used in an investigation of laser ablated plasmas. We have observed that the limit of material in the plasma plume is not the same as the limit of the luminosity of the plume. The angular distribution of material can be modelled by a cos n/Theta function over much of the range but a combined cos n/Theta + cos m/Theta function is required to describe the distribution near the visible tip of the plume.

  2. Optical properties of Chern-Simons systems

    NASA Astrophysics Data System (ADS)

    Huerta, Luis

    2016-05-01

    Chern-Simons (CS) systems interacting with electromagnetic radiation are described by a term f FɅF added to the Maxwell action. In (3+1)D, this CS term is a boundary term affecting the system behaviour in its borders. We study the consequences of the above in the properties of electromagnetic radiation, in particular, by considering the interplay between magneto-electric properties and topology. Apart from a modified Kerr polarization rotation, compared to that found for the particular case of topological insulators, we also found two Brewster angles, for s and p polarization of reflected radiation, respectively. Energy distribution between reflected and transmitted radiation is also studied in terms of the magneto-electric properties and topological condition of the system.

  3. Electronic, optical and bonding properties of MgCO 3

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  5. Monte Carlo method for photon heating using temperature-dependent optical properties.

    PubMed

    Slade, Adam Broadbent; Aguilar, Guillermo

    2015-02-01

    The Monte Carlo method for photon transport is often used to predict the volumetric heating that an optical source will induce inside a tissue or material. This method relies on constant (with respect to temperature) optical properties, specifically the coefficients of scattering and absorption. In reality, optical coefficients are typically temperature-dependent, leading to error in simulation results. The purpose of this study is to develop a method that can incorporate variable properties and accurately simulate systems where the temperature will greatly vary, such as in the case of laser-thawing of frozen tissues. A numerical simulation was developed that utilizes the Monte Carlo method for photon transport to simulate the thermal response of a system that allows temperature-dependent optical and thermal properties. This was done by combining traditional Monte Carlo photon transport with a heat transfer simulation to provide a feedback loop that selects local properties based on current temperatures, for each moment in time. Additionally, photon steps are segmented to accurately obtain path lengths within a homogenous (but not isothermal) material. Validation of the simulation was done using comparisons to established Monte Carlo simulations using constant properties, and a comparison to the Beer-Lambert law for temperature-variable properties. The simulation is able to accurately predict the thermal response of a system whose properties can vary with temperature. The difference in results between variable-property and constant property methods for the representative system of laser-heated silicon can become larger than 100K. This simulation will return more accurate results of optical irradiation absorption in a material which undergoes a large change in temperature. This increased accuracy in simulated results leads to better thermal predictions in living tissues and can provide enhanced planning and improved experimental and procedural outcomes. PMID

  6. 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

  7. Enhancing and quenching luminescence with gold nanoparticle films: the influence of substrate on the luminescent properties

    NASA Astrophysics Data System (ADS)

    José Guidelli, Eder; Ramos, Ana Paula; Baffa, Oswaldo

    2016-01-01

    Gold nanoparticle (AuNP) films were sputtered over glass and aluminum substrates to enhance optically stimulated luminescence (OSL), a luminescent technique employed for radiation detection, from x-ray irradiated NaCl nanocrystals. The AuNP films deposited over glass led to enhanced-OSL emission, whereas the AuNP films deposited on aluminum substrates quenched the OSL emission. The enhanced-OSL intensity is proportional to the optical density of the film's plasmon resonance band at the stimulation wavelength. For the case of the AuNP/aluminum films, the luminescence quenching diminishes, and OSL intensity partially recovers upon increasing the distance between the AuNPs and the aluminum substrates, and between the luminescent nanocrystals and the AuNP films. These results suggest that plasmonic interactions between the emitter nanocrystals, the localized surface plasmons (LSP) of the AuNPs, and the substrate are responsible for the OSL enhancement and quenching. In this sense, the substrate dictates whether LSP relaxation occurs by radiative or non-radiative transisitions, leading to enhanced or quenched OSL, respectively. Therefore, besides showing that AuNP films can enhance and/or tune the sensitivity of luminescent radiation detectors, and demonstrating OSL as a new technique to investigate mechanisms of plasmon-enhanced luminescence, these results bring insights on how substrates strongly modify the optical properties of AuNP films.

  8. Enhancing and quenching luminescence with gold nanoparticle films: the influence of substrate on the luminescent properties.

    PubMed

    Guidelli, Eder José; Ramos, Ana Paula; Baffa, Oswaldo

    2016-01-01

    Gold nanoparticle (AuNP) films were sputtered over glass and aluminum substrates to enhance optically stimulated luminescence (OSL), a luminescent technique employed for radiation detection, from x-ray irradiated NaCl nanocrystals. The AuNP films deposited over glass led to enhanced-OSL emission, whereas the AuNP films deposited on aluminum substrates quenched the OSL emission. The enhanced-OSL intensity is proportional to the optical density of the film's plasmon resonance band at the stimulation wavelength. For the case of the AuNP/aluminum films, the luminescence quenching diminishes, and OSL intensity partially recovers upon increasing the distance between the AuNPs and the aluminum substrates, and between the luminescent nanocrystals and the AuNP films. These results suggest that plasmonic interactions between the emitter nanocrystals, the localized surface plasmons (LSP) of the AuNPs, and the substrate are responsible for the OSL enhancement and quenching. In this sense, the substrate dictates whether LSP relaxation occurs by radiative or non-radiative transisitions, leading to enhanced or quenched OSL, respectively. Therefore, besides showing that AuNP films can enhance and/or tune the sensitivity of luminescent radiation detectors, and demonstrating OSL as a new technique to investigate mechanisms of plasmon-enhanced luminescence, these results bring insights on how substrates strongly modify the optical properties of AuNP films. PMID:26606392

  9. Optical coherence tomography angiography offers comprehensive evaluation of skin optical clearing in vivo by quantifying optical properties and blood flow imaging simultaneously.

    PubMed

    Guo, Li; Shi, Rui; Zhang, Chao; Zhu, Dan; Ding, Zhihua; Li, Peng

    2016-08-01

    Tissue optical clearing (TOC) is helpful for reducing scattering and enhancing the penetration depth of light, and shows promising potential in optimizing optical imaging performances. A mixture of fructose with PEG-400 and thiazone (FPT) is used as an optical clearing agent in mouse dorsal skin and evaluated with OCT angiography (Angio-OCT) by quantifying optical properties and blood flow imaging simultaneously. It is observed that FPT leads to an improved imaging performance for the deeper tissues. The imaging performance improvement is most likely caused by the FPT-induced dehydration of skin, and the reduction of scattering coefficient (more than ∼ 40.5%) and refractive-index mismatching (more than ∼ 25.3%) in the superficial (epidermal, dermal, and hypodermal) layers. A high correlation (up to ∼ 90%) between the relative changes in refractive-index mismatching and Angio-OCT signal strength is measured. The optical clearing rate is ∼ 5.83 × 10(-5) cm/s. In addition, Angio-OCT demonstrates enhanced performance in imaging cutaneous hemodynamics with satisfactory spatiotemporal resolution and contrast when combined with TOC, which exhibits a powerful practical application in studying microcirculation. PMID:26950927

  10. Enhanced optical output and reduction of the quantum-confined Stark effect in surface plasmon-enhanced green light-emitting diodes with gold nanoparticles.

    PubMed

    Cho, Chu-Young; Park, Seong-Ju

    2016-04-01

    We report the optical properties of localized surface plasmon (LSP)-enhanced green light-emitting diodes (LEDs) containing gold (Au) nanoparticles embedded in a p-GaN layer. The photoluminescence (PL) and electroluminescence (EL) intensities of a green LED with Au nanoparticles were enhanced by the coupling between excitons and LSPs. Excitation power-dependent PL and injection current-dependent EL measurements revealed that the blue-shift of PL and EL peaks with increasing carrier density was smaller for the LSP-enhanced LED compared with that for a conventional LED. The increased optical output power and decrease in blue-shift of the LED with Au nanoparticles were attributed to the increased radiative recombination efficiency of carriers induced by the LSP-coupling process and the compensation of the polarization-induced electric fields with LSP-enhanced local fields, both of which suppressed the quantum-confined Stark effect. PMID:27137038

  11. Lithium niobate nanoparticle-coated Y-coupler optical fiber for enhanced electro-optic sensitivity.

    PubMed

    Rao, Ch N; Sagar, S B; Harshitha, N G; Aepuru, Radhamanohar; Premkumar, S; Panda, H S; Choubey, R K; Kale, S N

    2015-02-15

    Single crystals of lithium niobate (LiNbO3), possessing high birefringence and anisotropic properties have been explored, for a long time, to harness their excellent electro-optic properties. However, their nanoforms are comparatively less explored. In this context, dielectric constant and polarization (P) versus electric-field (E) characteristics of LiNbO3 nanomaterials have been studied. A nonideal P-E loop and a dielectric constant of 20 at the onset of 1 kHz were seen. The electro-optic sensitivity was found to be 4 times as compared to the bulk LiNbO3 crystals. The results are attributed to oxygen vacancies, antisite defects, and grain boundary effects in an already congruent structural matrix of LiNbO3. PMID:25680132

  12. Optical properties of magnetron-sputtered and rolled aluminum

    SciTech Connect

    Van Gils, S.; Dimogerontakis, Th.; Buytaert, G.; Stijns, E.; Terryn, H.; Skeldon, P.; Thompson, G.E.; Alexander, M.R.

    2005-10-15

    The optical properties of magnetron-sputtered aluminum and AA1050 aluminum alloy sheet have been examined qualitatively using total reflectance and quantitatively by means of visible spectroscopic ellipsometry (VISSE). Significant changes in reflectance and optical constants are observed, which are related to the incorporation of oxide in the aluminum bulk. The role of such oxide was determined by VISSE using the Bruggeman effective-medium approximation, with the findings validated by x-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy.

  13. Electronic and optical properties of carbon supracrystalline sp 2 nanoallotropes

    NASA Astrophysics Data System (ADS)

    Brazhe, R. A.; Meftakhutdinov, R. M.

    2016-05-01

    Electronic and optical properties of 2D conducting carbon supracrystals are studied. The band structure is calculated using the tight-binding method. One sample is classified as semimetal, and the remaining samples are classified as narrow-band-gap semiconductors. The optical conductivity of the supracrystalline structures is calculated. It is demonstrated that the conductivity of semimetal supracrystals may be substantially higher than the grapheme conductivity. Complex refractive indices of the supracrystals are estimated.

  14. Nonlinear optical properties of potential sensitive styryl dyes.

    PubMed Central

    Huang, J Y; Lewis, A; Loew, L

    1988-01-01

    The nonlinear optical properties of dyes that alter their optical characteristics rapidly with membrane potential are described. The second harmonic signals from these dyes characterized in this paper are among the largest that have been detected to date. Structural conclusions are drawn from the second harmonic signals generated by the Langmuir Blodgett monolayers used in these measurements. Our results indicate that with appropriate instrumentation second harmonic signals could readily be detected from living cells stained with these dyes. PMID:3390517

  15. Enhancement of wall jet transport properties

    DOEpatents

    Claunch, Scott D.; Farrington, Robert B.

    1997-01-01

    By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.

  16. Enhancement of wall jet transport properties

    DOEpatents

    Claunch, S.D.; Farrington, R.B.

    1997-02-04

    By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct. 17 figs.

  17. Complex fluids with robustly tunable optical properties: experiments and theory

    NASA Astrophysics Data System (ADS)

    Cong, T.; Wani, S. N.; Sangani, A. S.; Sureshkumar, R.; Syracuse University Team

    2011-03-01

    Fluids with tunable optical properties are of fundamental and practical interest. They can be easily processed to manufacture thin films and interfaces for applications such as molecular detection and light trapping in photovoltaics. We use solution phase self-assembly to uniformly distribute various metallic nanoparticles to produce stable suspensions with localized, multiple wavelength or broad-band optical properties. Their spectral response can be robustly modified by varying the species, concentration, size and/or shape of the nanoparticles. Spectral behavior for finite particle concentrations can be predicted by an effective medium theory developed in this work. Structure, rheology and optical properties of these plasmonic suspensions as well as their potential application to high efficiency photovoltaics design will be discussed. NSF Grant 1049454.

  18. Photoconductive and nonlinear optical properties of composites based on metallophthalocyanines

    NASA Astrophysics Data System (ADS)

    Vannikov, A. V.; Grishina, A. D.; Gorbunova, Yu. G.; Tsivadze, A. Yu.

    2015-08-01

    The photoconductive, photorefractive and nonlinear optical properties of composites from polyvinylcarbazole or aromatic polyimide containing supramolecular ensembles of (tetra-15-crown-5) - phthalocyaninato gallium, indium, - phthalocyaninateacetato yttrium, - phthalocyaninato ruthenium with axially coordinated pyrazine molecules were investigated at 633, 1030 and 1064nmusing continuous and pulsed lasers. Supramolecular ensembles (SE) were prepared through dissolution of molecular metallophthalocyanines in tetrachloroethane (TCE) and subsequent treatment via three cycles of heating to 90∘C and slow cooling to room temperature. The zscan method in femtosecond and nanosecond regimeswas used for measuring nonlinear optical properties phthalocyaninato indium and yttrium in TCE solutions and polymer films. It was established that effect of heavy metallic atom is basic factor which determines the quantum yield, photorefractive amplification of laser object beam, dielectric susceptibility of third order and nonlinear optical properties of metallophthalocyanines.

  19. 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.

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

    PubMed

    Wilcoxon, Jess

    2009-03-01

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

  2. 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. PMID:26565262

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

    NASA Astrophysics Data System (ADS)

    de Melo, P. B.; Nunes, A. M.; Omena, L.; Nascimento, S. M. S. do; 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.

  4. Enhancement of the transverse magneto-optical Kerr effect via resonant tunneling in trilayers containing magneto-optical metals

    NASA Astrophysics Data System (ADS)

    Girón-Sedas, J. A.; Mejía-Salazar, J. R.; Moncada-Villa, E.; Porras-Montenegro, N.

    2016-07-01

    We propose a way to enhance the transverse magneto-optical Kerr effect, by the excitation of resonant tunneling modes, in subwavelength trilayer structures featuring a dielectric slab sandwiched between two magneto-optical metallic layers. Depending on the magneto-optical layer widths, the proposed system may exhibit an extraordinary transverse magneto-optical Kerr effect, which makes it very attractive for the design and engineering of thin-film magneto-optical-based devices for future photonic circuits or fiber optical-communication systems.

  5. Linear and nonlinear optical properties of Sb-doped GeSe2 thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen-Ying; Chen, Fen; Lu, Shun-Bin; Wang, Yong-Hui; Shen, Xiang; Dai, Shi-Xun; Nie, Qiu-Hua

    2015-06-01

    Sb-doped GeSe2 chalcogenide thin films are prepared by the magnetron co-sputtering method. The linear optical properties of as-deposited films are derived by analyzing transmission spectra. The refractive index rises and the optical band gap decreases from 2.08 eV to 1.41 eV with increasing the Sb content. X-ray photoelectron spectra further confirm the formation of a covalent Sb-Se bond. The third-order nonlinear optical properties of thin films are investigated under femtosecond laser excitation at 800 nm. The results show that the third-order nonlinear optical properties are enhanced with increasing the concentration of Sb. The nonlinear refraction indices of these thin films are measured to be on the order of 10-18 m2/W with a positive sign and the nonlinear absorption coefficients are obtained to be on the order of 10-10 m/W. These excellent properties indicate that Sb-doped Ge-Se films have a good prospect in the applications of nonlinear optical devices. Project supported by the National Key Basic Research Program of China (Grant No. 2012CB722703), the National Natural Science Foundation of China (Grant No. 61377061), the Young Leaders of Academic Climbing Project of the Education Department of Zhejiang Province, China (Grant No. pd2013092), the Program for Innovative Research Team of Ningbo City, China (Grant No. 2009B217), and the K. C. Wong Magna Fund in Ningbo University, China.

  6. Multifunctional organic thin films and their electronic/optical properties

    NASA Astrophysics Data System (ADS)

    Shao, Yan

    The concept of multifunctional organic thin films and their electronic/optical properties has been applied to organic functional device design, fabrication, and characterization. The organic devices involve organic light-emitting diodes (OLEDs) and organic photovoltaic devices (OPV) in this dissertation. In the research of graded junction structure of OLEDs, two kinds of naturally-formed graded junction (NFGJ) structures, sharp and shallow graded junctions, can be formed using single thermal evaporation boat loaded with uniformly mixed charge transport and light-emitting materials. OLEDs with NFGJ have been demonstrated in Chapter 3; the performance is comparable to the heterojunction OLEDs, but with better device lifetime. A novel method to prepare highly uniform mixed organic solid solutions through a high temperature and high-pressure fusion process has been demonstrated in Chapter 4. A series of fused organic solid solution (FOSS) compounds with NPD doped with different organic emitting dopants were prepared and DSC technique was utilized to determine the thermal characteristics. For the first time, the schematic phase diagram for this binary system has been obtained. High performance OLEDs of single color and white emission were fabricated and the device properties were characterized. In Chapter 5, an efficient photovoltaic heterojunction of tetracene and fullerene has been investigated and high performance organic solar cells have been demonstrated by thermal deposition and successive heat treatment. The preliminary conclusion for this enhancement is discussed and supported by atomic force microscopy images, absorption spectra and x-ray diffraction analysis. Additionally, an effective organic photovoltaic heterojunction based on the typical triplet material PtOEP was demonstrated. It is believed that introducing appropriate organic materials with long exciton lifetime is a very promising way to improve photovoltaic performance.

  7. 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.

  8. Electro-optical properties investigation of a series of hydroxylphenylporphyrins

    NASA Astrophysics Data System (ADS)

    Shi, Yingyan; Zheng, Wenqi; Li, Ziheng; Wang, Xingqiao; Wang, Dejun; Qiu, Shilun; Li, Xiangqing

    2006-07-01

    A one-step method was used to synthesize five hydroxylphenylporphyrin monomers with different structures [R.G. Little, J. Heterocyclic Chem. 18 (1981) 129]. They were confirmed by means of different spectroscopic analysis methods. The effects of the number and the position of the peripheral hydroxylphenyl groups of the porphyrin ring and solvents on their fluorescence spectra were discussed according to the change of the UV spectra. It was found that the fluorescence intensity was enhanced with an increase in the number of the peripheral hydroxylphenyl groups of the porphyrin ring. It was also found that the fluorescence intensity at 430 nm was very weak for tetrahydroxylphenylporphyrin (TPP) and tetraphenylporphyrin (5). This phenomenon is related to the structural symmetry. The red shift of the fluorescence spectra in polar solvent DMF relative to that in CH 2Cl 2 can be explained on the basis of the effect of solvation. The fluorescence intensity of hydroxylphenylporphyrin 2 in DMF at 430 nm is much stronger than that in CH 2Cl 2. The surface photovoltaic property of TPP and hydroxylphenylporphyrins 1-5 was studied by means of surface photovoltage spectra (SPS) and field induced surface photovoltage spectra (FISPS), which reveals that all the hydroxylphenylporphyrin are P-type semiconductors. The SPV spectral bands of all the hydroxylphenylporphyrins correspond to the π → π* transition. The SPS was similar to the UV-Vis spectra. It has also been found that the stronger the fluorescence intensity is, the weaker the surface photovoltage intensity is. For all the hydroxylphenylporphyrins and TPP, the surface photovoltage (SPV) of TPP is the weakest, that of hydroxylphenylporphyrin 1 is the strongest, then the SPV of the other hydroxylphenylporphyrins are gradually weakened with an increase in the number of the peripheral hydroxylphenyl groups of the porphyrin ring. This result indicates that controlling the number and position of the peripheral hydroxylphenyl

  9. The Electrical and Optical Properties of Doped Yttrium Aluminum Garnets

    NASA Astrophysics Data System (ADS)

    Chen, Jimmy Kuo-Wei

    The electrical and optical properties of YAG, Nd:YAG, Ti:YAG, and Zr:YAG were studied and quantitatively correlated to determine defect models for the defect structure of these systems. Correlations of these independent measurements were essential, as defect models derived from electrical or optical measurements alone were inconclusive. The correlated defect model provided a new interpretation for the electrical and optical properties of Ti:YAG. This defect model was then tested by checking its predicted dependence of Ti:YAG's optical properties with PO_2. This prediction was experimentally verified. Most of the systems were found to have a defect structure controlled by inadvertent background acceptors compensated by oxygen vacancies. This structure led to a characteristic conductivity isotherm where the conductivity varied as PO_2^{-1/4} for reduced PO_2's, and approached PO_2 independence for oxidizing PO_2's. Only for a heavily doped Zr:YAG sample was a new defect structure encountered. For this sample, an extrinsically compensated defect structure was detected, with the Zr^{+4} ions compensating the background acceptors. The conductivity isotherm for this sample had a n-type like component that varied as PO_2^{ -1/6}.. Quantitative correlations of the electrical and optical properties also provided a deep insight into the nature of the optical properties, and how these properties change as a function of oxidizing and reducing anneals. Correlations of this type were used to locate the energy level positions of rm Fe^{+2}, Ti ^{+3}, Zr^{+3}, and rm V_{o}^ {cdotcdot} in the YAG bandgap. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).

  10. 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.

  11. Mixed metal films with switchable optical properties

    NASA Astrophysics Data System (ADS)

    Richardson, T. J.; Slack, J. L.; Farangis, B.; Rubin, M. D.

    2002-02-01

    Thin, Pd-capped metallic films containing magnesium and first-row transition metals (Mn, Fe, Co) switch reversibly from their initial reflecting state to visually transparent states when exposed to gaseous hydrogen or following cathodic polarization in an alkaline electrolyte. Reversion to the reflecting state is achieved by exposure to air or by anodic polarization. The films were prepared by cosputtering from one magnesium target and one manganese, iron, or cobalt target. Both the dynamic optical switching range and the speed of the transition depend on the magnesium-transition metal ratio. Infrared spectra of films in the transparent, hydrided (deuterided) states support the presence of the intermetallic hydride phases Mg3MnH7, Mg2FeH6, and Mg2CoH5.

  12. Linear electro-optical properties of zincite

    NASA Astrophysics Data System (ADS)

    Shaldin, Yu. V.

    2004-09-01

    Orientational, dispersion, and temperature dependences of electro-optical coefficients of Li-doped ZnO single crystals are investigated. According to the data on the orientational dependences obtained far from the electronic absorption band, the values of all linearly independent components of the Pockels tensor are specified. In the range from 2 eV to E g , at both 100 and 300 K, the dispersion obeys a power law with m=2, which indicates a two-dimensional character of the van Hove singularity. The anomalies in the temperature dependences in the range from 15 to 700 K are explained by the competing contributions of the anharmonicities of the electron and lattice subsystems, which lead to anomalous behavior of the coefficients at both low ( T < 100 K) and high ( T > 100 K) temperatures. In the low-temperature range, the identified anomalies correlate with data of independent measurements of birefringence, spontaneous polarization, and dilatometry.

  13. Optical limiting properties of silver nanoparticles fabricated by laser ablation

    NASA Astrophysics Data System (ADS)

    Ong, T. S.; Lee, S. S.; Van, L. H.; Hong, Ming Hui; Chong, Tow Chong

    2004-10-01

    Silver nanoparticles have been fabricated by laser ablation of a silver metal foil in solution. The presence of sodium bis(2-ethylhexyl) sulfosuccinate increases the yield of the nanoparticles and enhances their stability. The optical limiting performance of the silver nanoparticles embedded in a PMMA film is compared to that in an aqueous solution.

  14. Controlling the morphological, structural, and optical properties of one-dimensional PCDTBT nanotubes by template wetting

    PubMed Central

    2014-01-01

    In this study, the synthesis of poly [N-9′-heptadecanyl-2, 7-carbazole-alt-5, 5-(4′, 7′-di-2-thienyl-2′, 1′, 3′-benzothiadiazole)] (PCDTBT) nanotubes via a templating method is reported. PCDTBT nanotubes were successfully grown by immersing the porous alumina template into 15 mg/ml of solution concentration for 2- and 24-h periods and annealed at 50°C. Changes in morphological and optical properties between nanotubes of different infiltration times (2 and 24 h) as well as its thin films are observed. The longer infiltration time of 24 h produced nanotubes with enhanced morphological, structural, and optical properties. Nanotubes that are formed between 2 and 24 h of infiltration show enhancement in absorption, photoluminescence, and shift in Raman peak if compared to their thin films. PMID:25392707

  15. Controlling the morphological, structural, and optical properties of one-dimensional PCDTBT nanotubes by template wetting

    NASA Astrophysics Data System (ADS)

    Bakar, Nor Asmaliza; Supangat, Azzuliani; Sulaiman, Khaulah

    2014-11-01

    In this study, the synthesis of poly [N-9'-heptadecanyl-2, 7-carbazole-alt-5, 5-(4', 7'-di-2-thienyl-2', 1', 3'-benzothiadiazole)] (PCDTBT) nanotubes via a templating method is reported. PCDTBT nanotubes were successfully grown by immersing the porous alumina template into 15 mg/ml of solution concentration for 2- and 24-h periods and annealed at 50°C. Changes in morphological and optical properties between nanotubes of different infiltration times (2 and 24 h) as well as its thin films are observed. The longer infiltration time of 24 h produced nanotubes with enhanced morphological, structural, and optical properties. Nanotubes that are formed between 2 and 24 h of infiltration show enhancement in absorption, photoluminescence, and shift in Raman peak if compared to their thin films.

  16. Enhanced environmental performance of fiber optic gyroscope by an adhesive potting technology.

    PubMed

    Chen, Jun; Ding, Nengwen; Li, Zhifeng; Wang, Wei

    2015-09-10

    An adhesive potting technology for fiber coils of a fiber optic gyroscope (FOG) is proposed. The fiber coil is immersed in liquid adhesive with superior mechanical properties. The internal air is first removed completely by vacuum pumping, and the adhesive is then evenly pressed into the fiber coil under pressure. The potted fiber core is prepared by ladder-type temperature curing and a stress-release process. With this potting technology, the vibration performance of an FOG is greatly improved and, at the same time, will not lead to degradation of its temperature performance. Using this potting technique of adhesive impregnation, the adaptability of FOGs will be enhanced. PMID:26368951

  17. Synthesis and study of optical properties of transition metals doped ZnS nanoparticles.

    PubMed

    Ramasamy, V; Praba, K; Murugadoss, G

    2012-10-01

    ZnS and transition metal (Mn, Co, Ni, Cu, Ag and Cd) doped ZnS were synthesized using chemical precipitation method in an air atmosphere. The structural and optical properties were studied using various techniques. The X-ray diffraction (XRD) analysis show that the particles are in cubic structure. The mean size of the nanoparticles calculated through Scherrer equation is in the range of 4-6.1 nm. Elemental dispersive (EDX) analysis of doped samples reveals the presence of doping ions. The scanning electron microscopic (SEM) and transmission electron microscopic (TEM) studies show that the synthesized particles are in spherical shape. Optical characterization of both undoped and doped samples was carried out by ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The absorption spectra of all the samples are blue shifted from the bulk ZnS. An optimum doping level of the transition metals for enhanced PL properties are found through optical study. PMID:22938741

  18. 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

  19. Prediction of nonlinear optical properties of large organic molecules

    NASA Technical Reports Server (NTRS)

    Cardelino, Beatriz H.

    1992-01-01

    The preparation of materials with large nonlinear responses usually requires involved synthetic processes. Thus, it is very advantageous for materials scientists to have a means of predicting nonlinear optical properties. The prediction of nonlinear optical properties has to be addressed first at the molecular level and then as bulk material. For relatively large molecules, two types of calculations may be used, which are the sum-over-states and the finite-field approach. The finite-field method was selected for this research, because this approach is better suited for larger molecules.

  20. Impact of phytoplankton community structure and function on marine particulate optical properties

    NASA Astrophysics Data System (ADS)

    McFarland, Malcolm Neil

    Phytoplankton are an ecologically important and diverse group of organisms whose distribution, abundance, and population dynamics vary significantly over small spatial (cm) and temporal (minutes) scales in the coastal ocean. Our inability to observe phytoplankton community structure and function at these small scales has severely limited our understanding of the fundamental ecological and evolutionary mechanisms that drive phytoplankton growth, mortality, adaptation and speciation. The goal of this dissertation was to enhance our understanding of phytoplankton ecology by improving in situ observational techniques based on the optical properties of cells, colonies, populations, and communities. Field and laboratory studies were used to determine the effects of phytoplankton species composition, morphology, and physiology on the inherent optical properties of communities and to explore the adaptive significance of bio-optically important cellular characteristics. Initial field studies found a strong association between species composition and the relative magnitude and shape of particulate absorption, scattering, and attenuation coefficient spectra. Subsequent field studies using scanning flow cytometry to directly measure optically important phytoplankton and non-algal particle characteristics demonstrated that the size and pigment content of large (>20 microm) phytoplankton cells and colonies vary significantly with the slope of particulate attenuation and absorption spectra, and with the ratio of particulate scattering to absorption. These relationships enabled visualization of phytoplankton community composition and mortality over small spatial and temporal scales derived from high resolution optical measurements acquired with an autonomous profiling system. Laboratory studies with diverse uni-algal cultures showed that morphological and physiological characteristics of cells and colonies can account for ˜30% of the optical variation observed in natural

  1. Surface structured optical coatings with near-perfect broadband and wide-angle antireflective properties.

    PubMed

    Perl, Emmett E; McMahon, William E; Farrell, Robert M; DenBaars, Steven P; Speck, James S; Bowers, John E

    2014-10-01

    Optical thin-film coatings are typically limited to designs where the refractive index varies in only a single dimension. However, additional control over the propagation of incoming light is possible by structuring the other two dimensions. In this work, we demonstrate a three-dimensional surface structured optical coating that combines the principles of thin-film optical design with bio-inspired nanostructures to yield near-perfect antireflection. Using this hybrid approach, we attain average reflection losses of 0.2% on sapphire and 0.6% on gallium nitride for 300-1800 nm light. This performance is maintained to very wide incidence angles, achieving less than 1% reflection at all measured wavelengths out to 45° for sapphire. This hybrid design has the potential to significantly enhance the broadband and wide-angle properties for a number of optical systems that require high transparency. PMID:25238041

  2. Functionality of bismuth sulfide quantum dots/wires-glass nanocomposite as an optical current sensor with enhanced Verdet constant

    NASA Astrophysics Data System (ADS)

    Panmand, Rajendra P.; Kumar, Ganapathy; Mahajan, Satish M.; Kulkarni, Milind V.; Amalnerkar, D. P.; Kale, Bharat B.; Gosavi, Suresh. W.

    2011-02-01

    We report optical studies with magneto-optic properties of Bi2S3 quantum dot/wires-glass nanocomposite. The size of the Q-dot was observed to be in the range 3-15 nm along with 11 nm Q-wires. Optical study clearly demonstrated the size quantization effect with drastic band gap variation with size. Faraday rotation tests on the glass nanocomposites show variation in Verdet constant with Q-dot size. Bi2S3 Q-dot/wires glass nanocomposite demonstrated 190 times enhanced Verdet constant compared to the host glass. Prima facie observations exemplify the significant enhancement in Verdet constant of Q-dot glass nanocomposites and will have potential application in magneto-optical devices.

  3. Optical properties of volcanic ash: improving remote sensing observations.

    NASA Astrophysics Data System (ADS)

    Whelley, Patrick; Colarco, Peter; Aquila, Valentina; Krotkov, Nickolay; Bleacher, Jake; Garry, Brent; Young, Kelsey; Rocha Lima, Adriana; Martins, Vanderlei; Carn, Simon

    2016-04-01

    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.

  4. Synthesis and optical properties of three-dimensional porous core-shell nanoarchitectures.

    PubMed

    Qian, Li-Hua; Ding, Yi; Fujita, Takeshi; Chen, Ming-Wei

    2008-05-01

    Three-dimensional porous core-shell nanostructures consisting of gold skeletons and silver shells were fabricated by controllable electroless plating. Optical properties of the 3D nanocomposite with a heterogeneous interface exhibit a significant shell-thickness dependence. The porous core-shell structure with an optimized shell thickness of approximately 3-5 nm exhibits a considerable improvement in surface-enhanced Raman scattering. This study has important implications in the functionalization of nanoporous metals by surface modification. PMID:18355096

  5. Optical clearing of human skin for the enhancement of optical imaging of proximal interphalangeal joints

    NASA Astrophysics Data System (ADS)

    Kolesnikova, Ekaterina A.; Kolesnikov, Aleksandr S.; Zabarylo, Urszula; Minet, Olaf; Genina, Elina A.; Bashkatov, Alexey N.; Tuchin, Valery V.

    2014-01-01

    We are proposing a new method for enhancement of optical imaging of proximal interphalangeal (PIP) joints in humans at skin using optical clearing technique. A set of illuminating laser diodes with the wavelengths 670, 820, and 904 nm were used as a light source. The laser diodes, monochromatic digital CCD camera and specific software allowed for detection of the finger joint image in a transillumination mode. The experiments were carried out in vivo with human fingers. Dehydrated glycerol and hand cream with urea (5%) were used as optical clearing agents (OCAs). The contrast of the obtained images was analyzed to determine the effect of the OCA. It was found that glycerol application to the human skin during 60 min caused the decrease of contrast in 1.4 folds for 670 nm and the increase of contrast in 1.5 and 1.7 folds for 820 nm and 904 nm, respectively. At the same time, the hand cream application to the human skin during 60 min caused the decrease of contrast in 1.1 folds for 670 nm and the increase of contrast in 1.3 and 1.1 folds for 820 nm and 904 nm, respectively. The results have shown that glycerol and the hand cream with 5% urea allow for obtaining of more distinct image of finger joint in the NIR. Obtained data can be used for development of optical diagnostic methods of rheumatoid arthritis.

  6. Optical Properties of Silver Nanoparticulate Glasses

    NASA Astrophysics Data System (ADS)

    Evans, Rachel N.; Cannavino, Sarah A.; King, Christy A.; Lamartina, Joseph A.; Magruder, Robert H.; Ferrara, Davon W.

    The ion exchange method of embedding metal nanoparticles (NPs) into float glass is an often used technique of fabricating colored glasses and graded-index waveguides. The depth and size of NP formation in the glass depends on the concentration and temperature of metal ions in the molten bath. In this study we explore the dichroic properties of silver metal ion exchange restricted to only one side of a glass microscope slide using reflection and transmission spectroscopy and its dependence on temperature, concentration of silver ions, and length of time in the molten bath.

  7. Acousto-optical properties of metamaterials

    NASA Astrophysics Data System (ADS)

    Pustovoit, V. I.

    2016-02-01

    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.

  8. Optical properties of colloidal germanium nanocrystals

    SciTech Connect

    WILCOXON,JESS P.; PROVENCIO,PAULA P.; SAMARA,GEORGE A.

    2000-05-01

    Highly crystalline germanium (Ge) nanocrystals in the size range 2--10 nm were grown in inverse micelles and purified and size-separated by high pressure liquid chromatography with on-line optical and electrical diagnostics. The nanocrystals retain the diamond structure of bulk Ge down to at least 2.0 nm (containing about 150 Ge atoms). The background- and impurity-free extinction and photoluminescence (PL) spectra of these nanocrystals revealed rich structure which was interpreted in terms of the bandstructure of Ge shifted to higher energies by quantum confinement. The shifts ranged from {minus}0.1 eV to over 1 eV for the various transitions. PL in the range 350--700 nm was observed from nanocrystals 2--5 nm in size. The 2.0 nm nanocrystals yielded the most intense PL (at 420 nm) which is believed to be intrinsic and attributed to direct recombination at {Gamma}. Excitation at high energy (250 nm) populates most of the conduction bands resulting in competing recombination channels and the observed broad PL spectra.

  9. 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.

  10. Electrical and optical properties of dense composites

    NASA Astrophysics Data System (ADS)

    Doyle, William T.

    1999-02-01

    Effective cluster models have been developed that treat disordered suspensions of monodisperse metal spheres as mixtures of isolated spheres and compact clusters of spheres using the Clausius-Mossotti equation [Phys. Rev. B 42, 9319 (1990); J. Appl. Phys. 71, 3926 (1992)] and the Bruggeman equation [J. Appl. Phys. 78, 6165 (1995)]. These effective cluster models are adapted to suspensions of dielectric particles with arbitrary complex permittivity. The models are compared with the coated sphere model of Sheng [Phys. Rev. Lett. 45, 60 (1980); J. Opt. Soc. Am. B 15, 1022 (1998)]. Model calculations are compared with the measurements of the optical transmission spectra and low frequency electrical conductivity of Au-SiO2 films by Cohen, Cody, Coutts, and Abeles [Phys. Rev. B 8, 3689 (1973)], and with the low frequency permittivity measurements on suspensions of Ag spheres in KCl of Grannan, Garland, and Tanner [Phys. Rev. Lett. 46, 375 (1981)]. The models accurately predict the percolation thresholds seen in the electrical measurements and are in good agreement with all of the experiments over the entire range of volume loading.

  11. Bipolar optical pulse coding for performance enhancement in BOTDA sensors.

    PubMed

    Soto, Marcelo A; Le Floch, Sébastien; Thévenaz, Luc

    2013-07-15

    A pump signal based on bipolar pulse coding and single-sideband suppressed-carried (SSB-SC) modulation is proposed for Brillouin optical time-domain analysis (BOTDA) sensors. Making a sequential use of the Brillouin gain and loss spectra, the technique is experimentally validated using bipolar complementary-correlation Golay codes along a 100 km-long fiber and 2 m spatial resolution, fully resolving a 2 m hot-spot at the end of the sensing fiber with no distortion introduced by the decoding algorithm. Experimental results, in good agreement with the theory, indicate that bipolar Golay codes provide a higher signal-to-noise ratio enhancement and stronger robustness to pump depletion in comparison to optimum unipolar pulse codes known for BOTDA sensing. PMID:23938490

  12. Microvascular contrast enhancement in optical coherence tomography using microbubbles

    NASA Astrophysics Data System (ADS)

    Assadi, Homa; Demidov, Valentin; Karshafian, Raffi; Douplik, Alexandre; Vitkin, I. Alex

    2016-07-01

    Gas microbubbles (MBs) are investigated as intravascular optical coherence tomography (OCT) contrast agents. Agar + intralipid scattering tissue phantoms with two embedded microtubes were fabricated to model vascular blood flow. One was filled with human blood, and the other with a mixture of human blood + MB. Swept-source structural and speckle variance (sv) OCT images, as well as speckle decorrelation times, were evaluated under both no-flow and varying flow conditions. Faster decorrelation times and higher structural and svOCT image contrasts were detected in the presence of MB in all experiments. The effects were largest in the svOCT imaging mode, and uniformly diminished with increasing flow velocity. These findings suggest the feasibility of utilizing MB for tissue hemodynamic investigations and for microvasculature contrast enhancement in OCT angiography.

  13. Nonlinear optical properties of nitrogen-doped bilayer graphene

    NASA Astrophysics Data System (ADS)

    Anand, Benoy; Podila, Ramakrishna; Rao, Apparao M.; Philip, Reji; Sai, S. Siva Sankara

    2013-06-01

    The electronic properties of graphene can be controlled by substitutional doping to obtain p-type or n-type characteristics. To this end, bilayer graphene films are synthesized using CVD method and substitutionally doped with Nitrogen (N). Previously, XPS measurements done in tandem with Raman spectroscopy revealed that the rich chemistry between carbon and nitrogen can result in pyridinic, pyrrolic, or graphitic configurations. The nonlinear optical properties (NLO) of both pristine and N-doped graphene samples are studied in both nanosecond and femtosecond excitation regimes using open aperture Z-scan method. Similar to the previous observations with Raman spectroscopy, we see that the NLO properties are more sensitive to the local bonding environments which determine the defect density in the graphene lattice, rather than just the dopant percentage. Our results give more insights into the effect of defects on the NLO properties of doped graphene which help in tailor making graphene samples for applications like modelocking and optical switching.

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

    EPA Science Inventory

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

  15. Theory of electronic and optical properties of nanostructures

    NASA Astrophysics Data System (ADS)

    Hewageegana, Prabath S.

    "There is plenty of room at the bottom." This bold and prophetic statement from Nobel laureate Richard Feynman back in 1950s at Cal Tech launched the Nano Age and predicted, quite accurately, the explosion in nanoscience and nanotechnology. Now this is a fast developing area in both science and technology. Many think this would bring the greatest technological revolution in the history of mankind. To understand electronic and optical properties of nanostructures, the following problems have been studied. In particular, intensity of mid-infrared light transmitted through a metallic diffraction grating has been theoretically studied. It has been shown that for s-polarized light the enhancement of the transmitted light is much stronger than for p-polarized light. By tuning the parameters of the diffraction grating enhancement can be increased by a few orders of magnitude. The spatial distribution of the transmitted light is highly nonuniform with very sharp peaks, which have the spatial widths about 10 nm. Furthermore, under the ultra fast response in nanostructures, the following two related goals have been proved: (a) the two-photon coherent control allows one to dynamically control electron emission from randomly rough surfaces, which is localized within a few nanometers. (b) the photoelectron emission from metal nanostructures in the strong-field (quasistationary) regime allows coherent control with extremely high contrast, suitable for nanoelectronics applications. To investigate the electron transport properties of two dimensional carbon called graphene, a localization of an electron in a graphene quantum dot with a sharp boundary has been considered. It has been found that if the parameters of the confinement potential satisfy a special condition then the electron can be strongly localized in such quantum dot. Also the energy spectra of an electron in a graphene quantum ring has been analyzed. Furthermore, it has been shown that in a double dot system some

  16. Optical Properties of waste derived carbon dots

    NASA Astrophysics Data System (ADS)

    Sarswat, Prashant; Free, Michael

    Carbon dots (CDs) have been extensively examined recently, mainly due to their luminescence and excitation wavelength dependent emission behavior. These dots can be derived from a variety of carbonaceous sources. Some of the possible sources are carbonaceous waste materials. Although it is possible to synthesize CDs using waste and their applications in light source, few steps such as to purification of starting material and removal of other impurities during solvothermal processing can enhance the performance of CDs and associated devices. Our primary results suggest that carbonaceous waste in liquid form is easy to process. In contrast the solid carbonaceous wastes are relatively difficult to process, but their availability is higher. In this regard, a detailed study has been performed to formulate the appropriate processing parameters for best performing CDs.

  17. 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.

  18. Compact fiber optic immunosensor using tapered fibers and acoustic enhancement

    NASA Astrophysics Data System (ADS)

    Zhou, Chonghua; Pivarnik, Philip E.; Auger, Steven; Rand, Arthur G.; Letcher, Stephen V.

    1997-06-01

    A compact fiber-optic sensing system that features all-fiber optical design and semiconductor-laser excitation has been developed and tested. A 2X2 fiber coupler directs the input light to the SMA connected sensing fiber tip and the fluorescent signal back to a CCD fiber spectrophotometer. In this system, the fluorescent signal is confined in the fiber system so the signal-to-noise ratio is greatly improved and the system can be operate in ambient light conditions. The utilization of a red laser diode has reduced the background signal of non-essential biomolecules. The fluorescent dye used is Cy5, which has an excitation wavelength of 650 nm and a fluorescent center wavelength of 680 nm. To illustrate the biosensor's diagnostic capabilities, a sandwich immunoassay to detect Salmonella is presented. Tapered fiber tips with different shapes and treatments were studied and optimized. An enhancement system employing ultrasonic concentration of target particles has also been developed and applied to the detection of Salmonella. The immunoassay was conducted in a test chamber that also serves as an ultrasonic standing-wave cell and allows microspheres to be concentrated in a column along the fiber probe. The system demonstrates broad promise in future biomedical application.

  19. 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.

  20. Structure, Electronic and Nonlinear Optical Properties of Furyloxazoles and Thienyloxazoles

    NASA Astrophysics Data System (ADS)

    Dagli, Ozlem; Gok, Rabia; Bahat, Mehmet; Ozbay, Akif

    2016-04-01

    Geometry optimization, electronic and nonlinear optical properties of isomers of furyloxazole and thienyloxazole molecules are carried out at the B3LYP/6-311++G(2d,p) level. The conformational analysis of 12 compounds have been studied as a function of torsional angle between rings. Electronic and NLO properties such as dipole moment, energy gap, polarizability and first hyperpolarizability were also calculated.

  1. Optical properties of Hg(1-x)Cd(x)Te

    NASA Astrophysics Data System (ADS)

    Tong, Fei-Ming; Ravindra, N. M.

    1993-04-01

    Optical properties of Hg(1-x)Cd(x)Te are summarized. Based on Penn-type (1962) models, the Moss (1950) relation, and the Wemple and DiDomenico (1971) approach, calculations of energy gap, plasmon energy, Fermi energy, oscillator strength and electronic polarizability have been made. Comparisons are made with the data available in the literature. Details of the dependency of the properties on composition are presented.

  2. Silicon oxide deposition for enhanced optical switching in polydimethylsiloxane-liquid crystal hybrids.

    PubMed

    De Sio, Luciano; Vasdekis, Andreas E; Cuennet, Julien G; De Luca, Antonio; Pane, Alfredo; Psaltis, Demetri

    2011-11-01

    We report an optical switch based on a diffraction grating by combining PDMS microstructures with a photo-responsive Nematic Liquid Crystal (NLC). The grating was realized via replica molding and was subsequently coated with a thin SiO layer. SiO induced a full planar alignment of the liquid crystal. The induced parallel alignment of the LC reduces the response time of the structure by approximately an order of magnitude compared to the same structures without SiO. We explored the effect of the pump intensity on the transmission properties and time response of the switch and identified a strong dependence on the probe polarization, due to the full planar alignment in this structure. The aforementioned inclusion of the SiO layer enables enhanced performance of optical devices based on the fusion of nematogens with soft and flexible substrates. PMID:22109231

  3. 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

  4. 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.

  5. Beam optical properties of the NSLS dipoles

    SciTech Connect

    Galayda, J.N.; Blumberg, L.N.; Heese, R.N.; Hsieh, H.C.H.

    1981-01-01

    Presently there is much interest in low energy (<1 GeV) electron storage rings as sources of synchrotron radiation and for studies of the free electron laser. The economics and physics of these storage rings favor the use of bending magnets with small radius of curvature and large bend angle. Some general features of such magnets and the results of magnetic measurements of the dipole magnets of the NSLS booster and storage rings are discussed. The magnetic measurements are interpreted in terms of the magnet geometry and saturation characteristics. Transport functions describing the linear and nonlinear focusing properties of the magnets, parametrized in terms of their curvature and fringe field length are discussed.

  6. Synthesis, field emission properties and optical properties of ZnSe nanoflowers

    NASA Astrophysics Data System (ADS)

    Xue, S. L.; Wu, S. X.; Zeng, Q. Z.; Xie, P.; Gan, K. X.; Wei, J.; Bu, S. Y.; Ye, X. N.; Xie, L.; Zou, R. J.; Zhang, C. M.; Zhu, P. F.

    2016-03-01

    ZnSe nanoflowers have been synthesized by reaction of Se powder with Zn substrates at low temperature. The as-prepared ZnSe nanoflowers were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray energy dispersive spectroscope (EDS) and Raman spectroscopy measurements. It was found that the morphologies of the as-prepared samples highly depended on reaction time. ZnSe nanoclusters and nanoflowers formed at 573 K when the reaction time was 20 and 60 min, respectively. The as-prepared ZnSe nanoflowers were composed of radically aligned ZnSe nanorods with smooth surfaces. The results of XRD, XPS, EDS, TEM and Raman showed that the as-prepared ZnSe nanocrystals were single crystals with cubic zinc blende (ZB) structure. The formation mechanism of the as-prepared ZnSe nanoflowers was also discussed. In addition, the as-prepared ZnSe nanoflowers had excellent electron emission properties. The turn-on field of the as-prepared ZnSe nanoflowers was 3.5 V/μm and the enhancement factor was 3499. The optical properties of the as-prepared ZnSe nanoflowers were also investigated. The results demonstrated that the as-prepared ZnSe nanoflowers were potential candidates for optoelectronic devices.

  7. Laminar Tendon Composites with Enhanced Mechanical Properties

    PubMed Central

    Alberti, Kyle A.; Sun, Jeong-Yun; Illeperuma, Widusha R.; Suo, Zhigang; Xu, Qiaobing

    2015-01-01

    Purpose A strong isotropic material that is both biocompatible and biodegradable is desired for many biomedical applications, including rotator cuff repair, tendon and ligament repair, vascular grafting, among others. Recently, we developed a technique, called “bioskiving” to create novel 2D and 3D constructs from decellularized tendon, using a combination of mechanical sectioning, and layered stacking and rolling. The unidirectionally aligned collagen nanofibers (derived from sections of decellularized tendon) offer good mechanical properties to the constructs compared with those fabricated from reconstituted collagen. Methods In this paper, we studied the effect that several variables have on the mechanical properties of structures fabricated from tendon slices, including crosslinking density and the orientation in which the fibers are stacked. Results We observed that following stacking and crosslinking, the strength of the constructs is significantly improved, with crosslinked sections having an ultimate tens ile strength over 20 times greater than non-crosslinked samples, and a modulus nearly 50 times higher. The mechanism of the mechanical failure mode of the tendon constructs with or without crosslinking was also investigated. Conclusions The strength and fiber organization, combined with the ability to introduce transversely isotropic mechanical properties makes the laminar tendon composites a biocompatiable material that may find future use in a number of biomedical and tissue engineering applications. PMID:25691802

  8. 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.

  9. Optical properties of plasmonic nanostructures: Theory & experiments

    NASA Astrophysics Data System (ADS)

    Bala Krishna, Juluri

    Metal nanoparticles and thin films enable localization of electromagnetic energy in the form of localized surface plasmon resonances (LSPR) and propagating surface plasmons respectively. This research field, also known as plasmonics, involves understanding and fabricating innovative nanostructures designed to manage and utilize localized light in the nanoscale. Advances in plasmonics will facilitate innovation in sensing, biomedical engineering, energy harvesting and nanophotonic devices. In this thesis, three aspects of plasmonics are studied: 1) active plasmonic systems using charge-induced plasmon shifts (CIPS) and plasmon-molecule resonant coupling; 2) scalable solutions to fabricate large electric field plasmonic nanostructures; and 3) controlling the propagation of designer surface plasmons (DSPs) using parabolic graded media. The full potential of plasmonics can be realized with active plasmonic devices which provide tunable plasmon resonances. The work reported here develops both an understanding for and realization of various mechanisms to achieve tunable plasmonic systems. First, we show that certain nanoparticle geometries and material compositions enable large CIPS. Second, we propose and investigate systems which exhibit coupling between molecular and plasmonic resonances where energy splitting is observed due to interactions between plasmons and molecules. Large electric field nanostructures have many promising applications in the areas of surface enhanced Raman spectroscopy, higher harmonic light generation, and enhanced uorescence. High throughput techniques that utilize simple nanofabrication are essential their advancement. We contribute to this effort by using a salting-out quenching technique and colloidal lithography to fabricate nanodisc dimers and cusp nanostructures that allow localization of large electric fields, and are comparable to structures fabricated by conventional lithography/milling techniques. Designer surface plasmons (DSPs) are

  10. 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.

  11. Optical properties of epitaxial YAG:Yb films

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

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

  13. Noise-Immune Cavity-Enhanced Optical Frequency Comb Spectroscopy

    NASA Astrophysics Data System (ADS)

    Rutkowski, Lucile; Khodabakhsh, Amir; Johanssson, Alexandra C.; Foltynowicz, Aleksandra

    2015-06-01

    We present noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), a recently developed technique for sensitive, broadband, and high resolution spectroscopy. In NICE-OFCS an optical frequency comb (OFC) is locked to a high finesse cavity and phase-modulated at a frequency precisely equal to (a multiple of) the cavity free spectral range. Since each comb line and sideband is transmitted through a separate cavity mode in exactly the same way, any residual frequency noise on the OFC relative to the cavity affects each component in an identical manner. The transmitted intensity contains a beat signal at the modulation frequency that is immune to frequency-to-amplitude noise conversion by the cavity, in a way similar to continuous wave noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS). The light transmitted through the cavity is detected with a fast-scanning Fourier-transform spectrometer (FTS) and the NICE-OFCS signal is obtained by fast Fourier transform of the synchronously demodulated interferogram. Our NICE-OFCS system is based on an Er:fiber femtosecond laser locked to a cavity with a finesse of ˜9000 and a fast-scanning FTS equipped with a high-bandwidth commercial detector. We measured NICE-OFCS signals from the 3νb{1}+νb{3} overtone band of CO_2 around 1.57 μm and achieved absorption sensitivity 6.4×10-11cm-1 Hz-1/2 per spectral element, corresponding to a minimum detectable CO_2 concentration of 25 ppb after 330 s integration time. We will describe the principles of the technique and its technical implementation, and discuss the spectral lineshapes of the NICE-OFCS signals. A. Khodabakhsh, C. Abd Alrahman, and A. Foltynowicz, Opt. Lett. 39, 5034-5037 (2014). J. Ye, L. S. Ma, and J. L. Hall, J. Opt. Soc. Am. B 15, 6-15 (1998). A. Khodabakhsh, A. C. Johansson, and A. Foltynowicz, Appl. Phys. B (2015) doi:10.1007/s00340-015-6010-7.

  14. 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.

  15. Mechanical Properties of Irradiated Polarization-Maintaining Optical Fibers

    NASA Technical Reports Server (NTRS)

    Moeti, L.; Moghazy, S.; Ally, A.; Barnes, S.; Watkins, L.; Cuddihy, E.

    1996-01-01

    Polarization-maintaining optical fibers, referred to as PANDA fibers, were subjected to Cobalt 60 radiation (300,000 Rad). The mechanical properties of the PANDA fibers were measured after exposure to gamma radiation and compared to non-irradiated PANDA fibers.

  16. Optical Properties of PbTe and PbSe

    SciTech Connect

    Ekuma, Chinedu E; Singh, David J; Moreno, Juana; Jarrell, Mark

    2012-01-01

    We report optical properties of PbTe and PbSe as obtained from first-principles calculations with the Tran-Blaha modified Becke-Johnson potential. The results are discussed in relation to existing experimental data, particularly in relation to the temperature dependence of the band gap.

  17. Polyurethane phantoms with homogeneous and nearly homogeneous optical properties

    NASA Astrophysics Data System (ADS)

    Keränen, Ville T.; Mäkynen, Anssi J.; Dayton, Amanda L.; Prahl, Scott A.

    2010-02-01

    Phantoms with controlled optical properties are often used for calibration and standardization. The phantoms are typically prepared by adding absorbers and scatterers to a clear host material. It is usually assumed that the scatterers and absorbers are uniformly dispersed within the medium. To explore the effects of this assumption, we prepared paired sets of polyurethane phantoms (both with identical masses of absorber, India ink and scatterer, titanium dioxide). Polyurethane phantoms were made by mixing two polyurethane parts (a and b) together and letting them cure in a polypropylene container. The mixture was degassed before curing to ensure a sample without bubbles. The optical properties were controlled by mixing titanium dioxide or India ink into polyurethane part (a or b) before blending the parts together. By changing the mixing sequence, we could change the aggregation of the scattering and absorbing particles. Each set had one sample with homogeneously dispersed scatterers and absorbers, and a second sample with slightly aggregated scatterers or absorbers. We found that the measured transmittance could easily vary by a factor of twenty. The estimated optical properties (using the inverse adding-doubling method) indicate that when aggregation is present, the optical properties are no longer proportional to the concentrations of absorbers or scatterers.

  18. 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)

  19. Tuning nonlinear optical absorption properties of WS₂ nanosheets.

    PubMed

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

    2015-11-14

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

  20. Electronic and optical properties of spodumene gemstone: A theoretical study

    NASA Astrophysics Data System (ADS)

    de Lima, A. F.; Souza, S. O.; Lalic, M. V.

    2008-03-01

    The spodumene (LiAlSi 2O 6) is a natural silicate with monoclinic structure, interesting for a jewel industry and possible application as a scintillator. In this paper we present the electronic structure and some of the basic optical properties of the pure spodumene crystal, as calculated by the first-principles, density functional based, full potential linear augmented plane wave method.

  1. Physical and optical properties of lead doped tellurite glasses

    NASA Astrophysics Data System (ADS)

    Riyatun; Rahmasari, Lita; Marzuki, Ahmad

    2016-02-01

    Physical and optical properties of lead telluride (Pb:TZBN) glasses with composition 55TeO2-(41-x)ZnO-2Bi2O3-2Na2O-xPbO where x = 1.0, 1.5, 2.0, 2.5% mol are presented. UV-VIS-NIR spectra of the glasses in the range of 300 - 800 nm along with their densities and refractive indices at 746 nm were recorded at room temperature. The optical bandgap energy (Eg) has been calculated from the fitting of Tauc plot. On the basis of these results we found that with the increase of Pb2+ content, their refractive indices are increased while their optical bandgaps are decreased. From this experiment, no distinct relationship between the Pb2+ content variation and the electronic polarizability (αO2-) as well as their optical basicity values (A) were observed.

  2. 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.}

  3. Third order nonlinear optical property of Bi₂Se₃.

    PubMed

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

    2013-01-28

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

  4. Optical and electrical properties of single-crystalline zirconium carbide

    SciTech Connect

    Modine, F.A.; Haywood, T.W.; Allison, C.Y.

    1985-12-15

    Optical and electrical properties are reported for single-crystalline ZrC/sub 0.89/. The specular reflectance was measured between 0.025 and 6.5 eV, and ellipsometry measurements were made between 1.2 and 4.5 eV. The combination of ellipsometry with reflectance allows optical functions to be computed reliably between 0 and 6.5 eV and also provides a check on the consistency of the measurements. The van der Pauw technique was used to measure the electrical resistivity of the samples at temperatures between 4.2 and 300 K and the Hall coefficient at room temperature. Drude parameters obtained from the electrical measurements are in good agreement with those obtained from the optical data. Both the optical and electrical results are compared to other experimental results and to theory.

  5. 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.

  6. Surface-enhanced raman optical data storage system

    DOEpatents

    Vo-Dinh, Tuan

    1994-01-01

    An improved Surface-Enhanced Raman Optical Data Storage System (SERODS) is disclosed. In the improved system, entities capable of existing in multiple reversible states are present on the storage device. Such entities result in changed Surface-Enhanced Raman Scattering (SERS) when localized state changes are effected in less than all of the entities. Therefore, by changing the state of entities in localized regions of a storage device, the SERS emissions in such regions will be changed. When a write-on device is controlled by a data signal, such a localized regions of changed SERS emissions will correspond to the data written on the device. The data may be read by illuminating the surface of the storage device with electromagnetic radiation of an appropriate frequency and detecting the corresponding SERS emissions. Data may be deleted by reversing the state changes of entities in regions where the data was initially written. In application, entities may be individual molecules which allows for the writing of data at the molecular level. A read/write/delete head utilizing near-field quantum techniques can provide for a write/read/delete device capable of effecting state changes in individual molecules, thus providing for the effective storage of data at the molecular level.

  7. Surface-Enhanced Raman Optical Data Storage system

    DOEpatents

    Vo-Dinh, T.

    1994-06-28

    An improved Surface-Enhanced Raman Optical Data Storage System (SERODS) is disclosed. In the improved system, entities capable of existing in multiple reversible states are present on the storage device. Such entities result in changed Surface-Enhanced Raman Scattering (SERS) when localized state changes are effected in less than all of the entities. Therefore, by changing the state of entities in localized regions of a storage device, the SERS emissions in such regions will be changed. When a write-on device is controlled by a data signal, such a localized regions of changed SERS emissions will correspond to the data written on the device. The data may be read by illuminating the surface of the storage device with electromagnetic radiation of an appropriate frequency and detecting the corresponding SERS emissions. Data may be deleted by reversing the state changes of entities in regions where the data was initially written. In application, entities may be individual molecules which allows for the writing of data at the molecular level. A read/write/delete head utilizing near-field quantum techniques can provide for a write/read/delete device capable of effecting state changes in individual molecules, thus providing for the effective storage of data at the molecular level. 18 figures.

  8. Far- and near-field optical properties of gold nanoparticle ensembles

    SciTech Connect

    Nedyalkov, N N; Dikovska, A O; Dimitrov, I; Nikov, Ru; Atanasov, P A; Toshkova, R A; Gardeva, E G; Yossifova, L S; Alexandrov, M T

    2012-12-31

    The optical properties of gold nanoparticle clusters are presented from the point of view of their applications in biophotonics, where the absorption and scattering spectra are crucial. Generalised multiparticle Mie theory and finite difference time domain (FDTD) technique are used for theoretical description of the far- and nearfield optical properties of two dimensional nanoparticle ensembles. The system under consideration consists of spherical gold nanoparticles from 20 to 200 nm in diameter, forming 2D clusters in water. The properties of the far-field absorption and scattering spectra as a function of the cluster size, particle dimensions, and interparticle distance are investigated for ordered hexagonal structure of the particle arrays. It is found that the absorption efficiency can be shifted to the IR spectral range by increasing array size and decreasing interparticle distance. The increase in the array size also results in enhancement of the scattering efficiency while the absorption is reduced. The near-field intensity distribution is inhomogeneous over the array, as formation of zones with intensity enhancement of about two orders of magnitude is observed in specific areas. The optical properties of an ensemble whose configuration is reproduced from real experiments of gold nanoparticle deposition onto cancer cells are also presented. The results obtained can be used in designing of nanoparticle arrays with applications in biophotonics, bioimaging and photothermal therapy. (nanosystems)

  9. The Optical Properties Monitor (OPM): a Multipurpose Optical Laboratory in Space

    NASA Technical Reports Server (NTRS)

    Wilkes, Donald R.

    1992-01-01

    The Optical Properties Monitor (OPM) is a multifunction in-flight laboratory for in-situ optical studies of materials. Many independent and related studies can be carried out on EURECA with the OPM instruments to address the experiment objectives. Test samples will be selected to address the materials and issues of the greatest interest to NASA, ESA, DoD, and the aerospace community. The objective of the OPM program is to study the effects of the space environment, both natural and induced, on optical, thermal control, solar array, and other materials.

  10. X-ray properties of optically selected QSOs

    NASA Technical Reports Server (NTRS)

    Avni, Y.; Tananbaum, H.

    1986-01-01

    The dependence of the X-ray-to-optical luminosity ratio on optical luminosity and redshift for optically selected QSOs is studied, largely on the basis of two, complete, magnitude-limited samples (Bright Quasar Survey /1983/ and Braccesi Faint /1984/) which were observed with the Einstein Observatory. Heterogeneous samples are established as adequate for the study of that dependence. Optimal choices for increasing the size of the data set for such a study are pointed out. The previous results of Avni and Tananbaum for alpha sub 0, x(z, L sub opt) are confirmed and strengthened, and the numerical sensitivity to changes in the values of q sub 0 and of the optical spectral index is evaluated. It is shown that the large majority, probably all, of optically selected QSOs are X-ray loud; no more than a few percent can be X-ray quiet. Thus X-ray emission appears to be a universal property of QSOs. It is shown that comparisons of optically selected QSOs with X-ray selected QSOs are numerically sensitive to the details of the input ingredients. A residual discrepancy of about a factor of 2 between calculated and observed X-ray number counts is found. Directions for further research that are important for understanding the full bivariate optical-X-ray evolution and luminosity function for QSOs are discussed.

  11. Experimental and theoretical optical properties of methylammonium lead halide perovskites

    NASA Astrophysics Data System (ADS)

    Leguy, Aurélien M. A.; Azarhoosh, Pooya; Alonso, M. Isabel; Campoy-Quiles, Mariano; Weber, Oliver J.; Yao, Jizhong; Bryant, Daniel; Weller, Mark T.; Nelson, Jenny; Walsh, Aron; van Schilfgaarde, Mark; Barnes, Piers R. F.

    2016-03-01

    The optical constants of methylammonium lead halide single crystals CH3NH3PbX3 (X = I, Br, Cl) are interpreted with high level ab initio calculations using the relativistic quasiparticle self-consistent GW approximation (QSGW). Good agreement between the optical constants derived from QSGW and those obtained from spectroscopic ellipsometry enables the assignment of the spectral features to their respective inter-band transitions. We show that the transition from the highest valence band (VB) to the lowest conduction band (CB) is responsible for almost all the optical response of MAPbI3 between 1.2 and 5.5 eV (with minor contributions from the second highest VB and the second lowest CB). The calculations indicate that the orientation of [CH3NH3]+ cations has a significant influence on the position of the bandgap suggesting that collective orientation of the organic moieties could result in significant local variations of the optical properties. The optical constants and energy band diagram of CH3NH3PbI3 are then used to simulate the contributions from different optical transitions to a typical transient absorption spectrum (TAS).The optical constants of methylammonium lead halide single crystals CH3NH3PbX3 (X = I, Br, Cl) are interpreted with high level ab initio calculations using the relativistic quasiparticle self-consistent GW approximation (QSGW). Good agreement between the optical constants derived from QSGW and those obtained from spectroscopic ellipsometry enables the assignment of the spectral features to their respective inter-band transitions. We show that the transition from the highest valence band (VB) to the lowest conduction band (CB) is responsible for almost all the optical response of MAPbI3 between 1.2 and 5.5 eV (with minor contributions from the second highest VB and the second lowest CB). The calculations indicate that the orientation of [CH3NH3]+ cations has a significant influence on the position of the bandgap suggesting that collective

  12. Enhancement of surface properties for coal beneficiation

    SciTech Connect

    Chander, S.; Aplan, F.F.

    1992-01-30

    This report will focus on means of pyrite removal from coal using surface-based coal cleaning technologies. The major subjects being addressed in this study are the natural and modulated surface properties of coal and pyrite and how they may best be utilized to facilitate their separation using advanced surface-based coal cleaning technology. Emphasis is based on modified flotation and oil agglomerative processes and the basic principles involved. The four areas being addressed are: (1) Collectorless flotation of pyrite; (2) Modulation of pyrite and coal hydrophobicity; (3) Emulsion processes and principles; (4) Evaluation of coal hydrophobicity.

  13. Enhanced gelation properties of purified gellan gum.

    PubMed

    Kirchmajer, Damian Martin; Steinhoff, Benedikt; Warren, Holly; Clark, Ross; in het Panhuis, Marc

    2014-03-31

    Gellan gum is a hydrogel-forming polysaccharide when combined with monovalent or divalent cations such as sodium, magnesium, potassium or calcium. Commercially, gellan gums are sold with trace amounts of these cations, which have been proven to affect the gelation and mechanical properties of the resultant hydrogels. A new method based on impedance analysis for determining the gel transition temperature of purified and un-purified gellan gum is presented. The sodium salt form of gellan gum is shown to have lower dissolution and gel transition temperatures. PMID:24637048

  14. Unconventional ratiometric-enhanced optical sensing of oxygen by mixed-phase TiO2

    NASA Astrophysics Data System (ADS)

    Lettieri, S.; Pallotti, D. K.; Gesuele, F.; Maddalena, P.

    2016-07-01

    We show that mixed-phase titanium dioxide (TiO2) can be effectively employed as an unconventional, inorganic, dual-emitting, and ratiometric optical sensor of O2. Simultaneous availability of rutile and anatase TiO2 photoluminescence (PL) and their peculiar "anti-correlated" PL responses to O2 allow using their ratio as a measurement parameter associated with the O2 concentration, leading to an experimental responsivity being by construction larger than the one obtainable for single-phase PL detection. A proof of this concept is given, showing a two-fold enhancement of the optical responsivity provided by the ratiometric approach. Besides the peculiar ratiometric-enhanced responsivity, other characteristics of mixed phase TiO2 can be envisaged as favorable for O2 optical probing, namely (a) low production costs, (b) absence of heterogeneous components, and (c) self-supporting properties. These characteristics encourage experimenting with its use for applications requiring high indicator quantities at a competitive price, possibly also tackling the need to develop supporting matrixes that carry the luminescent probes and avoiding issues related to the use of different components for ratiometric sensing.

  15. 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.

  16. Composite Materials with Magnetically Aligned Carbon Nanoparticles Having Enhanced Electrical Properties and Methods of Preparation

    NASA Technical Reports Server (NTRS)

    Hong, Haiping (Inventor); Peterson, G.P. (Bud) (Inventor); Salem, David R. (Inventor)

    2016-01-01

    Magnetically aligned carbon nanoparticle composites have enhanced electrical properties. The composites comprise carbon nanoparticles, a host material, magnetically sensitive nanoparticles and a surfactant. In addition to enhanced electrical properties, the composites can have enhanced mechanical and thermal properties.

  17. The Effects of Mineral Dust on the Hygroscopic and Optical Properties of Inorganic Salt Aerosols

    NASA Astrophysics Data System (ADS)

    Attwood, A. R.; Greenslade, M. E.

    2011-12-01

    Mineral dust particles are a significant fraction of the total aerosol mass, thus they play an important role in the Earth's radiative budget by direct scattering and absorption of radiation. Assessing this impact is complicated by the variability of optical properties resulting from water uptake and changes in chemical composition due to atmospheric mixing. Internal mixtures of montmorillonite, a clay component of mineral dust, with sodium chloride and ammonium sulfate were studied optically using cavity ring down spectroscopy. The effects of the addition of the clay to the optically observed deliquescence relative humidity (DRH) and water uptake of these salts was considered by investigating a series of different salt mass fractions. In most cases, montmorillonite alters the hygroscopic properties and causes the DRH to occur at a lower relative humidity. For ammonium sulfate, optical properties can be approximated by volume weighted mixing rules with some minor deviations around the DRH. For sodium chloride, this approximation is only accurate below the DRH with enhanced water uptake at higher relative humidities. Our results show that salt particles may transition from solid to liquid at a lower relative humidity than is expected based on the salt alone, as observed with changes in optical properties. Further, they contradict current measurements in the literature that suggest little change in the hygroscopic behavior of salts when insoluble mineral dust components are added and should continue to be investigated. Accurate, direct measurements of the effect of the addition of clays to the optical properties of common aerosol species will allow for improvements in the prediction of the aerosol direct effect.

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

    PubMed

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

    2015-12-01

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

  19. 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.

  20. 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.