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Phase transformation of Er³⁺-doped Al₂O₃ powders prepared by the sol-gel method

JOURNAL OF MATERIALS RESEARCH 2003年第10期18卷 2401-2405页

作者： Wang, XJ Lei, MK Yang, T Yuan, LJ Dalian Univ Technol Dept Mat Engn Surface Engn Lab Dalian 116024 Peoples R China

Er3+-doped Al2O3 powders were prepared by the sol-gel method, using aluminum isopropoxide [AI(OC3H7)(3)]-derived Al2O3 sols. The phase content diagram for the Er-doped Al-O system with the doping concentration up to 20 mol% is presented for sintering temperature from 550 to 1250 degreesC. The different crystalline types of (Al,Er)(2)O-3 phases-gamma, theta, alpha-and two Er-Al-O phases-ErAlO3 and Al10Er6O24-were detected. The Er3+ doping in the Al2O3 phases has a significant effect on phase transformations for gamma --> theta and theta --> alpha, indicating the enhancement for stability of the gamma and theta phases. Compared with the gamma-Al2O3 phase, the gamma-(Al,Er)(2)O-3 phase can be obtained at high temperatures up to about 1100 degreesC. The theta-(Al,Er)(2)O-3 phase, together with the alpha-(Al,Er)(2)O-3 phase, was still observed at 1200 degreesC under the high Er3+ doping concentration. The Er3+ doping suppressed the crystallization of the gamma and theta phases. At a low Er3+ doping concentration from about 2 to 5 mol%, the ErAlO3 phase precipitated out around 1100 degreesC. The Al10Er6O24 phase was observed at all sintering temperatures;the precipitation was carried out to all Er3+ doping concentrations with increasing sintering temperatures up to about 1200 degreesC.

关键词： wave-guides Films Photoluminescence Er3+

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Microfluidics in structural biology: smaller, faster... better

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CURRENT OPINION IN STRUCTURAL BIOLOGY 2003年第5期13卷 538-544页

作者： Hansen, C Quake, SR CALTECH Dept Appl Phys Pasadena CA 91125 USA

Microfluidic technologies promise unprecedented savings in cost and time through the integration of complex chemical and biological assays on a microfabricated chip. Recent advances are making elements of this vision a reality, facilitating the first large-scale integration of microfluidic plumbing with biological assays. The power of miniaturization lies not only in achieving an economy of scale, but also in exploiting the unusual physics of fluid flow and mass transport on small length scales to realize precise and efficient assays that are not accessible with macroscopic tools. Diverse applications ranging from time-resolved studies of protein folding to highly efficient protein crystal growth suggest that microfluidics may become an indispensable tool in biology.

关键词： Protein crystal-growth X-ray crystallography Free interface diffusion Softlithography wave-guides Crystallization Fabrication Systems Microgravity Chemotaxis

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Femtosecond two-photon-absorption-resonant four-wave mixing for time-resolved studies of photochromism in three dimensions

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CHEMICAL PHYSICS LETTERS 2003年第5-6期378卷 630-637页

作者： Konorov, SO Sidorov-Biryukov, DA Bugar, I Chorvat, D Chorvat, D Zheltikov, AM Moscow MV Lomonosov State Univ Dept Phys Moscow 119899 Russia Moscow MV Lomonosov State Univ Ctr Int Laser Moscow 119899 Russia Ctr Int Laser Bratislava 81219 Slovakia

Four-wave mixing (FWM) with two-photon absorption (TPA) resonances is shown to allow time-resolved studies of ultrafast processes involved in photochromism in three-dimensional spiropyran/PMMA samples on the femtosecond time scale. An FWM signal was produced using 130-fs pulses of 800-nm Ti:sapphire-laser radiation as a TPA-resonant pump and frequency-tunable pulses of an optical parametric amplifier as a time-delayed probe. Two-photon resonances allow strong one-photon absorption to be avoided, giving an access to any point inside a 3D photochromic sample. An ultrafast dynamics of photochromic transformations is revealed by comparing the time-resolved FWM signal with the cross-correlation of pump and probe pulses. (C) 2003 Elsevier B.V. All rights reserved.

关键词： Transient absorption-spectroscopy Optical-memory devices wave-guides Spiropyrans Ultrafast Storage Switch

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Measurement of propagation constant in waveguides with wideband coherent terahertz spectroscopy

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2003年第2期20卷 391-401页

作者： Hadjiloucas, S Galvao, RKH Bowen, JW Martini, R Brucherseifer, M Pellemans, HPM Bolívar, PH Kurz, H Digby, J Parkhurst, GM Chamberlain, JM Univ Reading Dept Cybernet Reading RG6 6AY Berks England Inst Tecnol Aeronaut Div Engn Eletron BR-12228900 Sao Jose Dos Campos SP Brazil Rhein Westfal TH Aachen Inst Halbleitertech D-52056 Aachen Germany Univ Nottingham Dept Phys Nottingham NG7 2RD England Univ Leeds Dept Elect & Elect Engn Leeds LS2 9JT W Yorkshire England

A quasi-optical technique for characterizing micromachined waveguides is demonstrated with wideband time-resolved terahertz spectroscopy. A transfer-function representation is adopted for the description of the relation between the signals in the input and output port of the waveguides. The time-domain responses were discretized, and the waveguide transfer function was obtained through a parametric approach in the z domain after describing the system with an autoregressive with exogenous input model. The a priori assumption of the number of modes propagating in the structure was inferred from comparisons of the theoretical with the measured characteristic impedance as well as with parsimony arguments. Measurements for a precision WR-8 waveguide-adjustable short as well as for G-band reduced-height micromachined waveguides are presented. (C) 2003 Optical Society of America.

关键词： Time-domain spectroscopy Automatic network analyzer wave-guides Millimeter-wave Reflectometer Pulses Port Representation Frequencies Calibration

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Nonlinear surface waves along the boundary of magnetic superlattices (LANS)

Nonlinear surface waves along the boundary of magnetic super...

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9th International Symposim on Microwave and Optical Technology (ISMOT 2003)

作者： Mousa, HM Shabat, MM Khalil, H Jäger, D Al Azhar Univ Dept Phys Gaza Palestinian Aut Israel

ISBN: (纸本)0819453684

In this paper, the propagation characteristics of nonlinear surface waves at a lateral antiferromagnetic/nonmagnetic superlattices (LANS) substrate and a nonlinear dielectric cover have been investigated. LANS super-lattices (antiferromagnetic-non magnetic) which are linear frequency-dependent gyromagnetic media, described with an effective medium theory. We found that the nonlinear magnetic waves are reciprocal for H-o = 0 and non reciprocal for H-o not equal 0. We also calculate and illustrate the variation of the wave index with the power flow for various values of the magnetic fraction f(1). We found that the non linearity interface is a very frequency dependent.

关键词： nonlinear waves dispersion relation wave-guides magnetic super-lattices

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Mathematical simulation of nonlinear optical wave guided sensors

Mathematical simulation of nonlinear optical wave guided sen...

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9th International Symposim on Microwave and Optical Technology (ISMOT 2003)

作者： Abadla, MM Shabat, MM Jäger, D Al Aqsa Univ Dept Phys Gaza Palestinian Aut Israel

ISBN: (纸本)0819453684

In this communication, we present an extensive theoretical analysis of nonlinear wave guide structure sensor and derive the conditions of the maximum sensitivity of TE nonlinear surface plasmons The theoretical requirements for reaching high sensitivity of the proposed nonlinear waveguide sensor will be determined. Exact maximum sensitivity expressions for nonlinear surface plasmons in sensing schemes will be obtained, which will allow the designer to find the work basis of maximum sensitivity and to create the right dimensioning of the proposed structure. We believe that the theoretical predictions and numerical modeling could realize future versatile sensors. The above concepts could be experimentally demonstrated and carried out.

关键词： optical sensors wave-guides nonlinear optics plasmons

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High-temperature Bragg grating waveguide sensor

High-temperature Bragg grating waveguide sensor

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International Conference on MEMS, NANO and Smart Systems

作者： Zhang, BW Kahrizi, M Concordia Univ Dept Elect & Comp Engn Montreal PQ H3G 1M8 Canada

ISBN: (纸本)0769519474

Design and analyses of a periodic dielectric Bragg grating waveguide temperatures reported in this work. The sensor is capable to measure temperatures ranging from room temperature to over 1200degreesC By using this sensor combined with a wavelength shifting detector and radiation detection schemes, a wide range thermometer can be built. Temperature can be measured in two steps using our thermal sensor. First step is to detect the wavelength shifting by an optical spectrum analyzer (OSA). The wavelength shifting could be converted to the change of environment temperature. This method is appropriate for the temperatures ranging from 20degreesC to 600degreesC. Another step is to detect the power of the probe radiation for the temperature range of over 600degreesC to the melting point of the probes. This sensor has potential applications in many areas particularly in aerospace industries..

关键词： MEMS wave-guides optical micro sensors temperature sensors integrated Bragg grating

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Wide range periodic waveguide temperature sensor

Wide range periodic waveguide temperature sensor

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15th IEEE Canadian Conference on Electrical and Computer Engineering

作者： Zhang, BW Kahrizi, M Concordia Univ Dept Elect & Comp Engn Montreal PQ H3G 1M8 Canada

ISBN: (纸本)0780377818

In this paper, we design and analyze a periodic dielectric Bragg grating waveguide temperature sensor ranging from room temperature to over 1200degreesC By using this sensor combined with a wavelength shifting detector and radiation detection schemes, a wide range thermometer can be built. Temperature can be measured in two ways using our thermal sensor. One way is to defect the wavelength shifting by an optical spectrum analyzer (OSA). The wavelength shifting could be converted to the change of environment temperature. This method is appropriate for the temperature range from 20degreesC to 600degreesC Another way is to detect the power of the probe radiation for the temperature range of over 600degreesC to the melting point of the probes. This sensor has many applications including in aerospace structures..

关键词： MEMS wave-guides optical micro sensors temperature sensors integrated Bragg grating

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Electronic Textbook of Electromagnetic waves

Electronic Textbook of Electromagnetic Waves

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作者： Raida, Zbyněk Brno University of Technology

Teaching university courses, which deal with the phenomena of the electromagnetic (EM) substantiality and their applications, is rather difficult due to their abstract nature. Therefore, teaching has to be accompanied by clear explanations and by simulations illustrating the examined topics. This is why an electronic textbook (ET) of EM waves and applications was developed. The ET presents theoretical descriptions of selected EM phenomena on two levels - on a bachelor’s one and a master’s one. Descriptive parts of the ET are completed by computer programs, which enable the reader to simulate the studied phenomena. Moreover, the ET explains the practical implementation of simulation routines in MATLAB, which helps students to understand a relationship between rather complicated mathematics and a relatively simple source code of its software implementation. Since the ET is freely accessible on the web, students can use it whenever as a classical textbook, a handbook or a software package. This fact positively influences the students’ knowledge and understanding as proven by our experience.

关键词： Antennas computer software educational methods electromagnetics Internet microwaves optics wave-guides teaching methods computer aided education

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Sol-gel organic-inorganic composites for 3-D holographic lithography of photonic crystals with submicron periodicity

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CHEMISTRY OF MATERIALS 2003年第12期15卷 2301-+页

作者： Saravanamuttu, K Blanford, CF Sharp, DN Dedman, ER Turberfield, AJ Denning, RG Univ Oxford Inorgan Chem Lab Oxford OX1 3QR England Univ Oxford Dept Phys Clarendon Lab Oxford OX1 3PU England

We demonstrate that silica-acrylate materials doped with transition metal (Zr, Ti) oxide nanoparticles are suitable for the three-dimensional holographic lithography of photonic crystals with submicron periodicity and large inorganic contents. By careful choice of inorganic components, such composites could provide a route to the template-free, direct lithography of three-dimensionally ordered structures with high refractive-index contrast, submicron periodicity, and band gaps in the visible and infrared regions.

关键词： wave-guides Infrared wavelengths Light Fabrication Silica Absorption Spectrum Gratings Titania Films

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