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Phase Effect on Guided Resonance in Photonic Crystal Slabs

Chinese Physics Letters 2005年第9期22卷 2294-2297页

作者：刘肯 Research Center of Photonic Crystals College of Optoelectronic Engineering National University of Defense Technology Changsha 410073

Phase effect on the guided resonances in photonic crystal slabs is analysed. We present an analysis in the case of a mirror symmetric system and an asymmetric system irradiated from both sides, as well as the more realistic and interesting case of a system bounded from one side by a perfect mirror. Gain is incorporated in the system, mainly to exemplify the results. Finally we find that phase effects persist in the asymmetric system resulting in a periodic response for the reflectivity versus the distance from the mirror, which is the main parameter controlling the phase relationship between the two incident waves.

关键词： BANDGAP STRUCTURES wave-guides

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Resonant Transmission of Narrow Metallic Slit with Imperfect Inner Face

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Chinese Physics Letters 2005年第7期22卷 1784-1786页

作者：刘诚闫长春刘莹陈浩 DepartmentofPhysics XuzhouNormalUniversityXuzhou221116

We numerically analyse the spectral properties of resonant transmission oflight through a sub-wavelength metal slit with imperfect inner face. It is found that slight defectson the inner face of the slit can remarkably increase the spectrum shift of its resonanttransmission, and this spectra-shift enhancement can be attributed to the induced evanescent wavesby the defects. This finding reveals the relationship between the spectrum shift of resonanttransmission and the evanescent waves and is potentially useful to explain some extraordinaryphenomena in practical experiments, in which the metallic slit is always not ideally smooth.

关键词： SUBwaveLENGTH APERTURE wave-guides GRATINGS LIGHT

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Subwavelength microwave resonators exhibiting strong coupling to radiation modes

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APPLIED PHYSICS LETTERS 2005年第15期87卷 151108-1-151108页

作者： Stuart, HR Tran, C Bell Labs Lucent Technol Whippany NJ 07981 USA Bell Labs Lucent Technol Holmdel NJ 07733 USA

We demonstrate a subwavelength spherical resonator at microwave frequencies designed to mimic the electromagnetic behavior of a negative permittivity sphere. The structure, which has a radius of similar to lambda/12 (where lambda is the resonant wavelength), consists of an axially symmetric array of noninterconnected conducting elements forming a resonant spherical object. The structure exhibits many of the properties inherent to negative permittivity spherical resonators, the most notable being a very strong coupling to radiation modes despite being much smaller than the wavelength. This characteristic is quantified by the radiation Q-factor, which was observed to be near 1.5 times the theoretical limit in some of the measured samples, matching the performance achievable in a negative permittivity sphere of comparable electrical size. These resonators may find application in the design of electrically small antennas, as well as in the experimental "simulation," at microwave frequencies, of nanophotonic device concepts based upon localized plasmon resonances in metal nanoparticles. (C) 2005 American Institute of Physics.

关键词： SMALL ANTENNAS wave-guides PLASMONS

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Microstructural and defect population change in electron beam irradiated Ge:SiO₂ MCVD glasses in the conditions of refractive index change writing

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JOURNAL OF NON-CRYSTALLINE SOLIDS 2005年第14-15期351卷 1196-1201页

作者： Jacqueline, AS Poumellec, B Univ Paris 11 Lab Physicochim Etat Solide UMR 8648 CNRS F-91405 Orsay France

Electron spin resonance (ESR) and ultra violet (UV) optical absorption spectra are measured in Ge:SiO2, glasses elaborated by modified chemical vapor deposition (MCVD) and irradiated by an electron beam of medium energy (10-50 keV). The doses (a few Gem 2) like the electron energy used, correspond to conditions for writing refractive index change for optical applications. These data yielded information on defect population changes. Raman spectroscopy was used for correlating these changes to microstructural changes. We point out a 5.1 eV absorption bleaching like surprisingly the one occurring under 5 eV laser irradiation correlated to an absorption increases around (4.4 and 5.8 eV). E ' centres are also produced. More specifically, we found in a previous work two domains of irradiation parameters for samples with large Ge content for which specific volume increases or decreases. We thus precise in this paper that (1) when compaction occurs, detectable by surface topography depression and D2 peak intensity increase, Si E ' centres are produced and a diamagnetic component absorbing strongly at 6.1 eV that may arise from sixfold coordinated Ge, (2) when expansion dominates, D2 peak does not decrease at all but long range order changes, detectable by modification of transverse optical (TO) and longitudinal optical (LO) mode intensity. In this case, Ge E ' and Ge(l) dominate and the previous absorption at 6.1 eV disappears. In addition, an absorption peak appears at 3.1 eV from an unknown defect. (c) 2005 Elsevier B.V. All rights reserved.

关键词： SILICA-ON-SILICON GE DOPED SILICA EXCIMER-LASER OPTICAL-FIBER wave-guides SIO2 DEPENDENCE ABSORPTION PRESSURE SPECTRA

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Integrated twin-photon sources for the silicon absorption band: a numerical study

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2005年第11期22卷 2331-2337页

作者： Ducci, S Leo, G Berger, V De Rossi, A Assanto, G Université Paris 7-Denis Diderot Route Départementale University “Roma Tre ”

We numerically study a narrowband semiconductor integrated source of counterpropagating twin photons for line-of-sight experiments in quantum key distribution. Considering the air transparency and the availability of silicon avalanche photodiodes to be around 770 nm, we focus on GaN- and ZnSe-based quadratically nonlinear multilayer waveguides. The design of a quasi-phase-matched chi((2)) profile in the growth direction allows us to generate 3 X 10(5) guided photon pairs per second for a pump power around 300 mW. (c) 2005 Optical Society of America.

关键词： PARAMETRIC FLUORESCENCE wave-guides QUANTUM ENTANGLEMENT THIN-FILMS GENERATION INDEXES

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Analysis of microwave cavities using LTL-FD method

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JOURNAL OF ELECTROMAGNETIC waveS AND APPLICATIONS 2005年第2期19卷 145-162页

作者： Mohsen, AA Elkaramany, EMA El-Hadeed, FGA Cairo Univ Dept Engn Math & Phys Giza 12211 Egypt

In this paper, improved three dimensional long transmission line-frequency domain (LTL-FD) circuits are used to determine cutoff wavenumbers of microwave resonators. The Pi-form of long transmission line representation [1] is used to construct the model. Consequently, treatment of boundaries and interfaces between different media is shown to be a simple procedure. The resonance frequencies of the resulting circuits are the required cutoff frequencies of the resonator. The problem is reduced to an eigenvalue problem, which gives the required solution. The models ensure the satisfaction of field divergence equations and, so, results are free from spurious modes. Results for homogeneous cavities and partially dielectric-filled cavities are given and are compared with available analytical solutions as well as those given by other methods.

关键词： wave-guides EQUATIONS TIME

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Space-selective precipitation of non-linear optical crystals inside silicate glasses using near-infrared femtosecond laser

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JOURNAL OF NON-CRYSTALLINE SOLIDS 2005年第10-11期351卷 885-892页

作者： Yonesaki, Y Miura, K Araki, R Fujita, K Hirao, K Univ Yamanashi Ctr Crystal Sci & Technol Kofu Yamanashi 4008511 Japan Cent Glass Corp Opt Device Dev Dept Ube Yamaguchi 7550001 Japan Kyoto Univ Grad Sch Engn Dept Chem Mat Nishikyo Ku Kyoto 6158510 Japan

Tightly focused laser pulses with approximately 120 fs duration and with a wavelength of 800 nm have been used to induce spaceselective precipitation of crystals with large second-order non-linear optical susceptibilities for BaO-TiO2-SiO2, Na2O-BaO-TiO2SiO2- and Li2O-Nb2O5-SiO2 glass systems. During the laser irradiation, blue light due to the second harmonic generation is observed at 400 nm in response to the precipitation of the crystals in the vicinity of the focal point of the laser beam. X-ray diffraction analysis indicates that only a single phase of LiNbO3 is observed for Li2O-Nb2O5-SiO2 glass system, while BaTiO3 and Ba2TiSi2O8 phases are precipitated for Na2O-BaO-TiO2-SiO2 and BaO-TiO2-SiO2 glass systems. The elemental analysis around the irradiated area using an electron probe microanalyzer reveals that the laser irradiation allows glass-constituting cations to migrate to bring about the precipitation of a ring-shaped crystalline phase. (c) 2005 Published by Elsevier B.V.

关键词： TRANSPARENT MATERIALS TELLURITE GLASSES FUSED-SILICA wave-guides PULSES SURFACE EXPOSURE

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Cascaded fourth-harmonic generation in a single nonlinear crystal

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2005年第8期22卷 1691-1698页

作者： Ivanov, R Saltiel, S Univ Sofia Fac Phys Dept Quantum Elect Sofia 1164 Bulgaria

We investigate theoretically the process of phase-matched fourth-harmonic generation in a single quadratic crystal. In the case of a plane-wave fundamental or weak focusing, the results have an analytical form. The optimal focusing position of the fundamental beam depends on the values of the mismatches for each of the two steps of the second-order cascading: doubling of the fundamental frequency and doubling of the frequency of the generated second-harmonic wave. It is shown that the optimized scheme for the cascaded single-crystal fourth-harmonic generation requires specially chosen mismatches of the two steps and focusing into the center of the nonlinear media. (c) 2005 Optical Society of America.

关键词： PERIODIC OPTICAL SUPERLATTICE HARMONIC-GENERATION 3RD-HARMONIC GENERATION LITHIUM-NIOBATE 2ND-HARMONIC GENERATION LASER-RADIATION POLED CRYSTALS wave-guides BLUE-LIGHT TEMPERATURE

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Guided propagation of terahertz pulses on metal wires

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2005年第9期22卷 2001-2008页

作者： Wang, KL Mittleman, DM Rice Univ Dept Elect & Comp Engn Houston TX 77251 USA

We demonstrate a new waveguiding structure for terahertz (THz) radiation in which broadband THz pulses are confined and guided along a bare metal wire. The propagation of THz pulses on such a waveguide is characterized with a fiber-coupled terahertz time-domain spectroscopy system. Free-space THz radiation is coupled onto the waveguide at different positions along the wire, and spatially resolved detection of the electric field of the guided wave is performed at the end of the wire. This waveguide exhibits the lowest attenuation of any waveguide for broadband THz pulses reported so far because of the minimal exposed metallic surface area. It also supports propagation of broadband radiation with negligible group-velocity dispersion, making it especially suitable for use in THz sensing and diagnostic systems. In addition, the structural simplicity lends itself naturally to the facile manipulation of the guided pulses, including coupling, directing, and beam splitting. These results can be described in terms of a model developed by Sommerfeld for waves propagating along the surface of a cylindrical conductor. (C) 2005 Optical Society of America.

关键词： FIELD OPTICAL MICROSCOPY PHOTONIC CRYSTAL FIBER wave-guides ANTENNAS INTERCONNECT RADIATION SYSTEM DOMAIN TIME

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Frequency-resolved optical gating in the 1.55 μm band via cascaded _χ⁽²⁾ processes

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2005年第9期22卷 1985-1993页

作者： Prawiharjo, J Gallo, K Broderick, NGR Richardson, DJ Univ Southampton Optoelect Res Ctr Southampton SO17 1BJ Hants England

We investigate ultrashort-pulse interactions based on cascaded second-harmonic generation and difference-frequency generation and propose their use for frequency-resolved optical gating (FROG) at telecom wavelengths in a waveguide configuration. We show how a chi((2))-chi((2)) FROG device could allow the efficient characterization of ultrashort pulses, with time resolutions well beyond the limits normally imposed by walk-off effects on single-step chi((2)) FROG devices. (C) 2005 Optical Society of America.

关键词： ULTRASHORT LASER-PULSES POLED LITHIUM-NIOBATE wave-guides 2ND-HARMONICGENERATION PHASE CHARACTERIZATION AMPLIFICATION NONLINEARITY TRANSMISSION COMPRESSION AMPLITUDE

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