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Radial Bragg lasers: optimal design for minimal threshold levels and enhanced mode discrimination

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2007年第9期24卷 2178-2184页

作者： Scheuer, Jacob Tel Aviv Univ Sch Elect Engn Ramat Aviv Israel

Radial Bragg distributed-feedback (DFB) lasers are designed and studied using the transfer matrix method, allowing an accurate analysis beyond the coupled-mode equations approach (small perturbations). Compared with conventional circular grating DFB lasers, incorporating periodic gratings, lower threshold levels, and enhanced mode discrimination are achieved by employing an optimal design strategy for the radial Bragg reflector. (c) 2007 Optical Society of America.

关键词： CIRCULAR-GRATING DFB PHOTONIC CRYSTAL SEMICONDUCTOR-LASERS wave-guides DBR LASERS RESONATORS NANOCAVITY EQUATIONS VOLUME GAIN

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HYBRID QUASI-STATIC ANALYSIS FOR MULTILAYER COPLANAR LINES

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IEE PROCEEDINGS-H MICROwaveS ANTENNAS AND PROPAGATION 1991年第4期138卷 307-312页

作者： CHANG, CN WONG, YC CHEN, CH Department of Electrical Engineering National Taiwan University Taipei Republic of China

A new quasistatic analysis of a coplanar waveguiding structure with multidielectric layers is presented, using a hybrid approach that combines the Galerkin finite-element method and the conformal-mapping technique. In the study, Wen's mapping function is adopted, which not only transforms the infinity problem domain into a finite region, but also overcomes the field singularity difficulty around the strip edges. Numerical results for effective dielectric constants, characteristic impedances, charge distributions and field distributions for various multilayer coplanar line structures are presented and the magnetic wall assumption over the slot is also investigated.

关键词： wave-guides TRANSMISSION LINES

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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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Photorefractive charge compensation in α-phase proton-exchanged LiNbO₃ waveguides

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2000年第8期17卷 1412-1419页

作者： Méndez, A García-Cabañes, A Carrascosa, M Cabrera, JM Univ Autonoma Madrid Dept Fis Mat E-28049 Madrid Spain

Photorefractive recording and light and dark erasures have been measured in unannealed alpha-phase proton-exchanged LiNbO3 waveguides. The saturation index change, Delta n(s) congruent to 9 x 10(-6), is independent of the light intensity within the studied range, 0.3-50 W/cm(2). The time dependencies are well represented by the sum of two exponential components. After complete optical erasure, diffraction efficiency eta increases in the dark (i.e., dark developing) up to similar to 17% of the saturation value eta(s) congruent to 0.12 and then decays to zero in similar to 4 h. All experimental results are reasonably well simulated by a model in which the Fe2+/Fe3+ light-induced charge distribution is compensated for by a light-insensitive species (ionic charges or holes) that is mobile at room temperature. (C) 2000 Optical Society of America [S0740-3224(00)01908-1] OCIS codes: 190.4400, 190.5330, 130.3130, 130.3730.

关键词： Benzoic-acid vapor wave-guides Holographic gratings Lithium-niobate Crystals Erasure Congruent compensated Lithium niobate crystals CHARGE DISTRIBUTION waveguide Device Component holographic gratings darkness

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PRACTICAL USE OF THE SPATIAL COHERENCE FUNCTION FOR DETERMINING LASER TRANSVERSE-MODE STRUCTURE

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OPTICAL ENGINEERING 1995年第11期34卷 3323-3328页

作者： PELZ, LJ ANDERSON, BL Univ. of Dayton (USA) Ohio State Univ. (USA)

The spatial coherence function of a beam exiting from a waveguiding device can be used to determine the transverse modal composition of the fields which are supported within the structure. The strength of the spatial coherence technique is that it directly yields the relative modal weights which exist within the cavity. While this technique has received little attention in the past due to the experimental difficulties in measuring spatial coherence, a recently developed technique overcomes several of these problems. We demonstrate how the relative modal amplitudes may be extracted from the spatial coherence function for the case where the field distribution is described by Hermite-Gaussian polynomials, We point out some limitations of this method and discuss how these may be circumvented.

关键词： SPATIAL COHERENCE TRANSVERSE MODES LASERS wave-guides

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Transmission through photonic crystals with multiple line defects at oblique incidence

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2008年第3期25卷 286-296页

作者： Serebryannikov, A. E. Magath, T. Tech Univ Hamburg D-21073 Hamburg Germany Panasonic Elect Devices Europe GmbH European Technol Ctr D-21337 Luneburg Germany

Transmission through two-dimensional photonic crystals (PhCs) with several (non)periodic line defects, each being created by removing a single row of rods, are studied with the emphasis put on angular selectivity. Most of the observed features appear due to a hybrid mechanism, which is realized as a common effect of the splitting of a transmission peak being the result of peculiar coupling of individual defect-mode resonators, and the angle-dependent guided-wave cavity effect, which depends on the chosen dispersion. In the case of zero-order propagation, the role of periodic location of line defects is demonstrated. A rich variety of effects can be obtained in the angle domain within a rather narrow frequency range, which contains eigenfrequencies of defect modes. Peculiarities of the transmission peaks arising in the case of first-order propagation are considered in both angle and frequency domains. It is shown that the defect-mode related peaks can be close by to the peaks, which appear due to resonances within the pieces of PhC separated by line defects and their coupling. For the effects observed while two beams are propagating, the presence of multiple defects is rather critical than the periodicity of their location. (C) 2008 Optical Society of America.

关键词： wave-guides BAND-STRUCTURE FILTERS REFLECTION MODES PROPAGATION RESONATOR LATTICES SLABS

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Counterpropagating quasi-phase matching: a generalized analysis

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2004年第8期21卷 1509-1521页

作者： Landry, GD Maldonado, TA Texas A&M Univ College Stn TX 77843 USA

The system of four differential equations governing counterpropagating quasi-phase matching are recast in a Hamiltonian form that leads to immediate insight into the nonlinear mixing process by inspection for all possible boundary conditions. A reduced Hamiltonian is found using conservation relations that are dependent on only two normalized field efficiencies and two aggregate phases. Hamiltonian contours are plotted in a series of phase-space cross sections to provide insight into the generalized behavior. The nonlinear eigenmodes are found, and their stability is examined. Finally, two specific counterpropagating quasi-phasematching configurations, i.e., mirrored and mirrorless, are analyzed using this general Hamiltonian with the appropriate boundary conditions. (C) 2004 Optical Society of America.

关键词： CASCADED 2ND-ORDER PROCESSES POLED LITHIUM-NIOBATE BACKWARD 2ND-HARMONICGENERATION wave-guides FREQUENCY-GENERATION NONLINEAR MEDIUM BULK LINBO3 CONFIGURATION CHI((2)) LIGHT

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Second-order optical nonlinearity and accompanying near-surface structural modifications in thermally poled soda-lime silicate glasses

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS 2006年第11期23卷 2303-2309页

作者： An, Honglin Fleming, Simon Univ Sydney Australian Photon Cooperat Res Ctr Opt Fibre Technol Ctr Sydney NSW 2006 Australia

Soda-lime silicate (SLS) glasses were thermally poled at 230 degrees C-280 degrees C with de voltages up to 2 kV applied to induce a second-order optical nonlinearity. Accompanying structural modifications to the thermally poled SLS glasses were investigated with scanning electron microscopy. On the cathode surface, sodium metasilicate crystals were formed through the reduction of migrating sodium ions at the cathode. At the anode, intense phase separation occurred within several micrometers beneath the anode surface during the thermal poling process. These structural modifications are attributed to the electric field enhancement effect. The second-order nonlinearity induced in such poled samples was found to still be present after a long period of high-temperature annealing, perhaps mainly due to a hindering effect from the phase separation and/or accumulated calcium ions to the recombination of space charges. (c) 2006 Optical Society of America.

关键词： FUSED-SILICA ELECTRIC-FIELD 2ND-HARMONIC GENERATION DEPLETION REGION wave-guides PROFILES SAMPLES VISUALIZATION FIBERS

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Evolution with the annealing treatments of the photoluminescence mechanisms in a-SiN_x:H alloys prepared by reactive evaporation

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JOURNAL OF APPLIED PHYSICS 2007年第12期101卷 123532-1-123532-1页

作者： Molinari, M. Rinnert, H. Vergnat, M. Univ Reims UFR Sci EA3799 Lab Microscopies & Etud Nanostruct F-51685 Reims 2 France Univ Nancy 1 UMR CNRS 7556 Lab Phys Mat F-54506 Vandoeuvre Les Nancy France

A wide range of amorphous hydrogenated silicon nitride thin films with an excess of silicon was prepared by evaporation of silicon under a flow of nitrogen and hydrogen ions. A strong visible photoluminescence at room temperature was observed for the as-deposited films as well as for films annealed up to 1100 degrees C. The chemical composition and the structure of the films were investigated using x-ray photoelectron, thermal desorption, and Raman spectroscopies, infrared absorption measurements, grazing incidence x-ray diffraction experiments, and transmission electron microscopy. Two luminescence mechanisms were identified for the films depending on the annealing temperature. For annealing temperatures below 650 degrees C, the films are made of amorphous silicon-rich phases mixed with nitrogen-rich phases. These inhomogeneities in the chemical composition, coupled with the evolution of the photoluminescence energies and intensities with the hydrogen content, suggest that the emission is due to the recombination process of the photogenerated carriers within the band-tail states. For temperatures higher than 800 degrees C, a phase separation occurs and the films could be described as silicon nanoclusters embedded in an insulating amorphous silicon nitride matrix. The clusters are amorphous, and then crystallized when the annealing temperature is high enough. The correlation between the clusters sizes and the photoluminescence results suggests that the emission observed after annealing treatments at temperature higher than 900 degrees C is due to the quantum confinement of the carriers inside the silicon clusters. By carefully choosing the preparation and the annealing conditions, it is possible to tune the photoluminescence energy in the visible range. (c) 2007 American Institute of Physics.

关键词： SILICON QUANTUM DOTS AMORPHOUS-SILICON ELECTRONIC-STRUCTURE OPTICAL GAIN THIN-FILMS VISIBLE PHOTOLUMINESCENCE POROUS SILICON wave-guides LUMINESCENCE NITRIDE

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SCATTERING PROPERTIES OF DISCONTINUITIES IN NRD GUIDE

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IEE PROCEEDINGS-MICROwaveS ANTENNAS AND PROPAGATION 1994年第3期141卷 205-210页

作者： XU, S WU, X YONEYAMA, T TOHOKU UNIV ELECT COMMUN RES INSTAOBA KUSENDAIMIYAGI 980JAPAN

The scattering characteristics of a guided wave by a class of discontinuities in a non-radiative dielectric (NRD) guide are systematically investigated by a method which combines the building block approach of multimode network theory with a rigorous mode-matching procedure. Some experimental data justify the effectiveness and accuracy of the present method. Extensive numerical results are obtained to develop useful guidelines for the design of NRD guide components.

关键词： wave-guides SCATTERING PROPERTIES DIELECTRIC MATERIALS

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