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Refractive index measurements of planar chalcogenide thin film

JOURNAL OF NON-CRYSTALLINE SOLIDS 2003年第1-3期328卷 183-191页

作者： Laniel, JM Ménard, JM Turcotte, K Villeneuve, A Vallée, R Lopez, C Richardson, KA Univ Laval Ctr Opt Photon & Laser Dept Phys Geneie Phys & Opt Laval PQ G1K 7P4 Canada Univ Cent Florida CREOL Sch Opt Orlando FL 32816 USA

We report on the measurements of the refractive index of As-S-Se chalcogenide glasses near 1.55 mum. The measurements were made on annealed and non-annealed samples of thermally evaporated thin films. The data for two different series of glasses are presented: the compositions As40S60-xSex and the compositions AsxS(100-x)/2Se(100-x)/2 where the ratio of sulfur to selenium is kept constant (1:1). It has been found that replacing sulfur by selenium in the first series increases the refractive index from 2.4 to 2.8 and increasing the arsenic content in the second series increases the refractive index, In all cases, it has been found that annealing the samples increase the refractive index. The accuracy in the refractive index measurement is +/-0.2%. (C) 2003 Elsevier B.V. All rights reserved.

关键词： Optical-properties wave-guides Glasses

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waveguides in three-dimensional layer-by-layer photonic crystals

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2003年第5期20卷 801-809页

作者： Li, ZY Ho, KM Iowa State Univ Ames Lab Ames IA 50011 USA Iowa State Univ Dept Phys & Astron Ames IA 50011 USA

A photonic crystal waveguide network can form in a three-dimensional layer-by-layer photonic crystal along three orthogonal directions. We investigate guided-mode band structures for different waveguide configurations by numerical calculations that combine a plane-wave expansion method with a supercell technique. The in-plane waveguide network composed of waveguides along the (100) and (010) directions of the crystal is located in a single layer of the photonic crystal. This structural design is easy to achieve experimentally. One can create these in-plane waveguides either by removing one single rod or by breaking a segment in each of an array of parallel rods. One produces the off-plane waveguide by removing some segments of rods along the (001) stacking direction of the crystal. Single-mode operation of a waveguide can be achieved by appropriate adjustment of geometrical parameters such as the location and the size of the waveguide. Intrinsic lattice symmetries in these photonic crystal waveguides have been fully employed to reduce the complexity of the numerical solution of guided-mode band structures significantly. (C) 2003 Optical Society of America.

关键词： wave-guides Band-gaps Electromagnetic-waves Infrared wavelengths Bends Transmission Emission Defect Light Slabs

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Low-shrinkage, high-hardness, and transparent hybrid coatings: Poly(methyl methacrylate) cross-linked with silsesquioxane

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CHEMISTRY OF MATERIALS 2003年第18期15卷 3481-3489页

作者： Harreld, JH Esaki, A Stucky, GD Univ Calif Santa Barbara Dept Chem & Biochem Santa Barbara CA 93106 USA Mitsubishi Chem Corp MCC Grp Sci & Technol Res Ctr Precis Coating & Surface Modificat Lab Aoba Ku Yokohama Kanagawa 2278502 Japan

Copolymers of trimethoxysilylpropyl methacrylate (TMSPM) and methyl methacrylate (MMA) with varied composition and molecular weight were prepared as building blocks for transparent organic-inorganic hybrid materials. Thermally and chemically induced condensation of these network precursors after solvent evaporation results in optically clear coatings as thick as 1.0 mm with extremely low lateral shrinkage. Many interacting variables such as acid catalyst concentration, polymer molecular weight, polymer composition, and thermal treatment combine to produce materials having controllable shrinkage, hardness, transparency, and thermal stability. By selectively defining these variables, the syntheses of these materials are optimized such that silsesquioxane-cross-linked acrylic polymers are produced that exhibit desirable properties such as low optical loss in the visible spectrum, low lateral shrinkage, high scratch hardness, and no glass transition temperature. The available combinations, interrelationships, and limitations of these properties are discussed.

关键词： Organic-inorganic nanocomposites Sol-gel materials Mechanical-properties Composite-materials Optical-properties wave-guides Chemistry Trimethoxysilylpropylmethacrylate Tetramethoxysilane Polymerization

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Photoinduced structural relaxation in chalcogenide glasses

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JOURNAL OF NON-CRYSTALLINE SOLIDS 2003年第1-3期332卷 35-42页

作者： Lucas, P Doraiswamy, A King, EA Univ Arizona Dept Mat Sci & Engn Tucson AZ 85721 USA

Measurements of residual entropy were performed on irradiated chalcogenide glasses using a modulated differential scanning calorimeter. We show that glass from the GexSe1-x system can undergo extensive structural relaxation under sub-bandgap, irradiation. This ability to relax is correlated with the strong/fragile character of the glass-forming system. Fragile glassformers experience larger relaxation as expected from the Kauzmann entropy plot. The temperature dependence of this photorelaxation process is also consistent with entropy relaxation. These measurements demonstrate that the glass configurational entropy decreases under irradiation. This can be regarded as a light activated aging process. (C) 2003 Elsevier B.V. All rights reserved.

关键词： Reversible photostructural change Lone-pair semiconductors As2s3 glass Rigidity percolation Valence-alternation Constraint theory Forming liquids Gese2 glass wave-guides Fragility

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New impedance boundary conditions in two-dimensional LTL-FD treatment of scattering problems

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JOURNAL OF ELECTROMAGNETIC waveS AND APPLICATIONS 2003年第9期17卷 1269-1287页

作者： Elkaramany, EMA Cairo Univ Engn Math & Phys Dept Giza 12211 Egypt

In this paper, two approximate and efficient boundary conditions in the two dimensional Long Transmission Line-Frequency Domain (LTL-FD) circuits [1] are introduced. The first is the circuit representation of the symmetry when passing through the centers of nodes. The second is an accurate absorbing impedance boundary condition to represent open boundaries which is proved to be an efficient absorbing boundary. The validity of these conditions is first tested in the problem of radiation by a line source. The method is then applied to the problem of plane wave scattering by conducting scatterers using the null field method. A sparse banded matrix is obtained and is solved for the required scattered field. Results for square and circular conducting scatterers are given and are compared with available analytical and numerical solutions. It is found that accurate results are obtained when the distance d between the source and the outer boundary is as small as kd approximate to 1.0, where k is the wavenumber. This considerably reduces the matrix dimensions and hence the computation time.

关键词： wave-guides

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Protein adsorption kinetics under an applied electric field: An optical waveguide lightmode spectroscopy study

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LANGMUIR 2003年第12期19卷 5089-5097页

作者： Brusatori, MA Tie, Y Van Tassel, PR Wayne State Univ Dept Chem Engn & Mat Sci Detroit MI 48202 USA

The controlled surface placement of protein molecules represents a crucial step toward many new biotechnological devices and processes. A promising means of directing the structure and formation rate of an adsorbed protein layer is through an applied electric potential difference. We present here a method for continuously measuring the protein adsorption under a direct current voltage using optical waveguide lightmode spectroscopy. An indium tin oxide-coated waveguiding sensor chip serves as the anode and adsorbing substrate, and a platinum counter electrode serves as the cathode in a parallel plate arrangement. For (negatively charged) human serum albumin in either pure water or N-[2-hydroxyethyl]piperazine-N'-ethanesulfonic acid (HEPES) buffer, we find the transport-limited and initial surface-limited rates of adsorption to significantly increase with the applied potential. For (positively charged) horse heart cytochrome c, we observe no influence of the voltage on the transport-limited adsorption rate in either solvent and a decrease with the voltage in the initial surface-limited rate in a HEPES (but not a pure water) solvent. Interestingly, we find the rate of adsorption at moderate to high surface density to greatly increase with the voltage for both proteins;this effect is more pronounced in water than in HEPES. We attribute this enhanced adsorption to contact between electrode and protein patches of complementary charge, leading to more oriented and efficiently packed adsorbed molecules and, in the case of high voltage, to multilayer formation.

关键词： Bovine serum-albumin Internal-reflection fluorescence Random sequentialadsorption Assembled polyelectrolyte films wave-guides Brownian dynamics Grating couplers Surface-charge Crystallization conditions Lysozyme adsorption

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Observation of the complex propagation of a femtosecond laser pulse in a dispersive transparent bulk material

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2003年第3期20卷 597-602页

作者： Kumagai, H Cho, SH Ishikawa, K Midorikawa, K Fujimoto, M Aoshima, S Tsuchiya, Y RIKEN Laser Technol Lab Wako Saitama 3510198 Japan Hamamatsu Photon KK Cent Res Lab Shizuoka 4348601 Japan

Pulse shapes in a dispersive transparent material modulated by group-velocity dispersion, self-phase modulation, and self-focusing induced by a femtosecond laser light were observed directly with femtosecond time-resolved optical polarigraphy probing the induced instantaneous birefringence. The first observation of the state of femtosecond laser pulses about the interaction region inside the transparent bulk material indicated that the pulse propagation was accomplished with a multiple conelike structure that was hypothesized from a numerical simulation with an extended nonlinear Schrodinger equation. (C) 2003 Optical Society of America.

关键词： Varying envelope approximation Resolved optical polarigraphy wave-guides Plasma Breakdown Light Generation Dynamics Air

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Micromachined flow cytometers with embedded etched optic fibers for optical detection

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JOURNAL OF MICROMECHANICS AND MICROENGINEERING 2003年第3期13卷 447-453页

作者： Lin, CH Lee, GB So Taiwan Univ Technol Dept Elect Engn Tainan 710 Taiwan Natl Cheng Kung Univ Dept Engn Sci Tainan 701 Taiwan

This paper presents a device that integrates a micromachined flow cytometer with two embedded etched optic fibers in order to carry out on-line detection of particles and cells. A simple and reliable fabrication process is used to fabricate the cytometer on soda-lime glass substrates. It is shown experimentally that particles/cells can be squeezed hydrodynamically into a narrow stream by two neighboring sheath flows such that they flow individually through a detection region. The resulting scattered light is then detected by etched optic fibers downstream. The proposed approach has the advantage that particles/cells can be counted without the need for fluorescent labeling or delicate optical alignment procedures. The current study confirms the success of the proposed microchip in the counting of polystyrene beads and human blood cells. The results also indicate that the intensity of the scattered light is proportional to the size of the particles/cells, which suggests that the proposed device may offer the potential to distinguish between particles/cells of different sizes.

关键词： wave-guides Fabrication

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Optical properties and applications of chalcogenide glasses: a review

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JOURNAL OF NON-CRYSTALLINE SOLIDS 2003年第1-3期330卷 1-12页

作者： Zakery, A Elliott, SR Shiraz Univ Coll Sci Dept Phys Shiraz 71454 Iran Univ Cambridge Dept Chem Cambridge CB2 1EW England

A review of some properties of chalcogenide glasses and the current status of their applications is given. Techniques to characterize the linear and non-linear properties of these glasses are introduced and used to measure the optical constants of chalcogenide glasses in the form of bulk, thin film and fiber. Different techniques for the fabrication of gratings and waveguides in these glasses are described. Achievable efficiencies of gratings, as well as propagation losses of fabricated waveguides, are presented. The possibilities of fabricating active devices, such as fiber amplifiers and lasers, are presented. Finally, a novel application of chalcogenide glasses, namely all-optical switching for the fabrication of efficient femtosecond switches, is introduced. (C) 2003 Elsevier B.V. All rights reserved.

关键词： Pulsed-laser deposition 1 3 mu-m As-s-se wave-guides 2-photonabsorption Fiber amplifiers As2s3 glass Photoinduced anisotropy Nonlinear refraction Quantum-efficiency

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Temporal analysis of open-circuit dark photovoltaic spatial solitons

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2003年第12期20卷 2515-2522页

作者： Chauvet, M Univ Franche Comte UMR CNRS 6603 Inst Microtech Lab Opt PM Duffieux F-25030 Besancon France

A theoretical model and experimental results to characterize the time-dependent formation of one-dimensional dark photovoltaic solitons under open-circuit conditions are presented. According to this theory, quasi-steady-state and steady-state solitons can both be obtained. In the quasi-steady-state regime solitons have intensity-independent widths, whereas their formation time is inversely proportional to the intensity, as confirmed by experimental results obtained with LiNbO3 samples. Theory predicts that the response times of steady-state solitons will be given by the dielectric response in the absence of an illuminating field, T-d. In the samples used in this research, only a trend toward a steady-state regime was observed, because of the prohibitively high value of T-d. (C) 2003 Optical Society of America.

关键词： Photorefractive screening solitons wave-guides Optical beam Bright Media Propagation Crystals Field OPEN CIRCUIT Solitons quasi-steady states light beams temporal analysis High Value PHOTOVOLTAIC Steady state Reaction Time crystals waveguide Device Component BRIGHT

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