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Polarized transmission spectra of the fiber-microsphere system

APPLIED PHYSICS LETTERS 2005年第12期86卷 1115-1-1115-3页

作者： Guan, G Vollmer, F Polytech Univ Microparticle Photophys Lab MP3L Brooklyn NY 11201 USA Rockefeller Univ Ctr Studies Phys & Biol New York NY 10021 USA

The polarized transmission spectra of a fiber-microsphere system was investigated. Light from an optical fiber was side coupled into the dielectric microsphere through optical tunneling. It was found that the polarization of some of the light coupled into the microsphere and back into the fiber changed by 90 degrees. The experiments showed a level of high signal-to-noise ratio peaks at the resonant frequencies in the polarized spectra and the possibility of discriminating between TE and TM modes of the microsphere. (C) 2005 American Institute of Physics.

关键词： COUPLED-MODE THEORY wave-guides RESONANCES DEVICES TAPER

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Magnon coherent conductance via atomic nanocontacts

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JOURNAL OF PHYSICS-CONDENSED MATTER 2007年第26期19卷 66208-1-66208-1页

作者： Bourahla, B. Khater, A. Tigrine, R. Rafil, O. Abou Ghantous, M. Univ Maine UMR 6087 Lab Phys Etat Condense F-72085 Le Mans France Univ Mouloud Mammeri Lab Phys & Chim Quant Tizi Ouzou 15000 Algeria Lebanese Amer Univ Sch Sci Byblos Lebanon

A calculation for the coherent scattering and conductance of magnons via atomic nanocontacts is presented. The model system is composed of two groups of semi- infinite magnetically ordered Heisenberg monatomic chains, joined together by the magnetic nanocontact, and the system is supported on a nonmagnetic substrate and considered otherwise free from magnetic interactions. The coherent transmission and reflection coefficients are derived as elements of a Landauer- type scattering matrix. Transmission and reflection scattering cross sections are calculated specifically for three distinct symmetric and asymmetric geometric configurations of the nanocontact. Three cases of local magnetic exchange on the nanocontact domain are analysed for each configuration to investigate the influence of softening and hardening of the magnetic boundary conditions. In analogy with coherent electronic transport, we calculate the magnon coherent transport. The numerical results show the interference effects between the incident scattered magnons and the localized spin states on the nanocontact, with characteristic Fano resonances. The numerical results yield an understanding of the relationship between the coherent magnon conductance and the architecture of the embedded magnetic nanocontact.

关键词： wave-guides MAGNETIC-PROPERTIES CRYSTAL-SURFACES SCATTERING TRANSPORT CHAINS NANOSTRUCTURES RESONANCES BOUNDARIES PHONONS

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Discrete light localization in one-dimensional nonlinear lattices with arbitrary nonlocality

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Physical Review E 2005年第6期72卷 066608-066608页

作者： Andrea Fratalocchi Gaetano Assanto []NooEL-Nonlinear Optics and OptoElectronics Laboratories INFM-CNISM and Department of Electronic Engineering University Roma Tre Via della Vasca Navale 84 00146 Rome Italy

We model discrete spatial solitons in a periodic nonlinear medium encompassing any degree of transverse nonlocality. Making a convenient reference to a widely used material—nematic liquid crystals—we derive a form of the discrete nonlinear Schrödinger equation and find a family of discrete solitons. Such self-localized solutions in optical lattices can exist with an arbitrary degree of imprinted chirp and have breathing character. We verify numerically that both local and nonlocal discrete light propagation and solitons can be observed in liquid crystalline arrays.

关键词： NEMATIC LIQUID-CRYSTALS SCHRODINGER-EQUATION SOLITON DYNAMICS wave-guides BREATHERS ARRAYS

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Symmetry breaking in linearly coupled dynamical lattices

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Physical Review E 2007年第6期76卷 066606-066606页

作者： G. Herring P. G. Kevrekidis B. A. Malomed R. Carretero-González D. J. Frantzeskakis Department of Physics University of Athens Panepistimiopolis Zografos Athens 15784 Greece

We examine one- and two-dimensional models of linearly coupled lattices of the discrete-nonlinear-Schrödinger type. Analyzing ground states of the system with equal powers (norms) in the two components, we find a symmetry-breaking phenomenon beyond a critical value of the total power. Asymmetric states, with unequal powers in their components, emerge through a subcritical pitchfork bifurcation, which, for very weakly coupled lattices, changes into a supercritical one. We identify the stability of various solution branches. Dynamical manifestations of the symmetry breaking are studied by simulating the evolution of the unstable branches. The results present the first example of spontaneous symmetry breaking in two-dimensional lattice solitons. This feature has no counterpart in the continuum limit because of the collapse instability in the latter case.

关键词： NONLINEAR SCHRODINGER-EQUATION BOSE-EINSTEIN CONDENSATE ASYMMETRIC SOLITONS DISCRETE BREATHERS wave-guides FESHBACH RESONANCES OPTICAL LATTICES FIBER COUPLERS PROPAGATION THRESHOLDS

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Self-focusing dynamics of coupled optical beams

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Physical Review A 2007年第2期75卷 023813-023813页

作者： Amiel A. Ishaaya Taylor D. Grow Saikat Ghosh Luat T. Vuong Alexander L. Gaeta School of Applied and Engineering Physics Cornell University Ithaca New York 14853 USA

We theoretically and experimentally investigate the mutual collapse dynamics of two spatially separated optical beams in a Kerr medium. Depending on the initial power, beam separation, and the relative phase, we observe repulsion or attraction, which in the latter case reveals a sharp transition to a single collapsing beam. This transition to fusion of the beams is accompanied by an increase in the collapse distance, indicating the effect of the nonlinear coupling on the individual collapse dynamics. Our results shed light on the basic nonlinear interaction between self-focused beams and provide a mechanism to control the collapse dynamics of such beams.

关键词： SPATIAL SOLITON-INTERACTIONS PHOTOREFRACTIVE SCREENING SOLITONS wave-guides INCOHERENT COLLISIONS DISPERSIVE MEDIA LASER-PULSES AIR FUSION COLLAPSE INSTABILITY

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Variable holographic femtosecond laser processing by use of a spatial light modulator

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APPLIED PHYSICS LETTERS 2005年第3期87卷 1101-1-1101-3页

作者： Hayasaki, Y Sugimoto, T Takita, A Nishida, N Univ Tokushima Fac Engn Dept Opt Sci & Technol Tokushima 7708506 Japan

We propose a holographic femtosecond laser processing system capable of parallel, arbitrary, and variable patterning. These features are achieved by introducing a spatial light modulator displaying a hologram into the femtosecond laser processing system. We demonstrate the variable parallel processing of a glass sample. (c) 2005 American Institute of Physics.

关键词： TRANSPARENT MATERIALS wave-guides PULSES IONIZATION SILICA PHASE GLASS FABRICATION NANOSECOND ABLATION

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Influence of group-velocity mismatch and inertia of optical nonlinearity on slow-light effects in stimulated inelastic scattering of light

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Physical Review A 2007年第3期76卷 033825-033825页

作者： A. M. Zheltikov Physics Department International Laser Center M.V. Lomonosov Moscow State University Vorob’evy gory Moscow 119992 Russia

Group-velocity mismatch between the pump and Stokes pulses and the inertia of optical nonlinearity are shown to modify scenarios of slow-light evolution of laser pulses accompanying stimulated Raman and Brillouin scattering (SRS and SBS) of light. In the transient regime of SRS and SBS, the inertia of nonlinear polarization of a medium shifts the peak of an amplified Stokes field envelope relative to the input Stokes pulse. This shift is sensitive to the shape of input laser pulses and is controlled by the SRS and/or SBS gain, the damping time of the optical phonon wave, and the delay time between the input pump and Stokes pulses. In the regime where both the inertia of nonlinear polarization of an SRS medium and group-delay effects are significant, stationary modes of the Stokes field may exist in the frame of reference propagating with the group velocity of the pump field. The maximum group delay attainable for such modes of the Stokes field is limited, similar to the steady-state regime, by the ratio of the steady-state SRS gain to the Raman gain bandwidth.

关键词： RAMAN SCATTERING wave-guides ATOMIC GAS FIBER PULSES DELAYS CHIP

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THz sideband generation at telecom wavelengths in a GaAs-based quantum cascade laser

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APPLIED PHYSICS LETTERS 2005年第7期87卷 1101-1-1101-3页

作者： Dhillon, SS Sirtori, C Barbieri, S de Rossi, A Calligaro, M Beere, HE Ritchie, DA Univ Paris 07 F-75251 Paris France Thales Res & Technol F-91404 Orsay France TeraView Ltd Cambridge CB4 0WS England Univ Cambridge Cavendish Lab Cambridge CB3 0HE England

Terahertz sideband generation is demonstrated by using the nonlinear intracavity interaction between far-infrared and near-infrared modes in a GaAs waveguide. A low power near-infrared beam at 1.32 mu m is coupled into a quantum cascade laser operating at 104 mu m (2.9 THz), which acts as both the THz source and the nonlinear medium. The conversion efficiency of the resulting sidebands is found to be approximately 4.5x10(-6). (C) 2005 American Institute of Physics.

关键词： SUM-FREQUENCY GENERATION wave-guides

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Helmholtz-Manakov solitons

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Physical Review E 2006年第6期74卷 066612-066612页

作者： J. M. Christian G. S. McDonald P. Chamorro-Posada Departmento de Teoría de la Señal y Comunicaciones e Ingeniería Telemática Universidad de Valladolid ETSI Telecomunicación Campus Miguel Delibes s/n 47011 Valladolid Spain

A different spatial soliton-bearing wave equation is introduced, the Helmholtz-Manakov (HM) equation, for describing the evolution of broad multicomponent self-trapped beams in Kerr-type media. By omitting the slowly varying envelope approximation, the HM equation can describe accurately vector solitons propagating and interacting at arbitrarily large angles with respect to the reference direction. The HM equation is solved using Hirota’s method, yielding four different classes of Helmholtz soliton that are vector generalizations of their scalar counterparts. General and particular forms of the three invariants of the HM system are also reported.

关键词： BIREFRINGENT OPTICAL FIBERS KERR MEDIA SPATIAL SOLITONS DARK SOLITONS wave-guides PROPAGATION STABILITY EQUATION AMPLITUDES BEAM

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Air-gap fabrication using a sacrificial polymeric thin film synthesized via initiated chemical vapor deposition

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JOURNAL OF THE ELECTROCHEMICAL SOCIETY 2006年第4期153卷 C223-C228页

作者： Chan, K Gleason, KK MIT Dept Chem Engn Cambridge MA 02139 USA

Thin films of a sacrificial polymer based on poly(cyclohexyl methacrylate) (PCHMA) were synthesized using initiated chemical vapor deposition (iCVD). iCVD is able to make cross-linked PCHMA in situ on a substrate in one step without using any solvents. Although cross-linked, the polymer was found to decompose cleanly, leaving behind a maximum of 0.3% of residue by thickness upon completion of thermal annealing. Cross-linking renders the polymer stable in practically all solvents, so photoresist used for patterning can be removed by dissolution instead of ashing. The high etch rate (0.35 mu m/min) in oxygen reactive-ion etching in addition to the stability in solvents eliminates the need of a hard mask during etching. This represents an improvement over previously reported spin-on sacrificial materials. Infrared spectroscopy and solubility tests confirm the identity of the iCVD polymer and its stability in solvents. The onset of thermal decomposition is 270 degrees C, allowing the polymer to survive high-temperature processing steps. Fabrication using conventional lithographic, etching, and deposition techniques resulted in void structures having feature sizes of a minimum of 1.5 mu m. This work represents a novel approach for air-gap fabrication using a sacrificial polymer, combining the rationale behind cross-linking and the technique required for thin-film deposition.

关键词： DISTRIBUTED BRAGG REFLECTORS METHYL-METHACRYLATE ELECTRICALINTERCONNECTIONS POLY(METHYL METHACRYLATE) PLASMA POLYMERIZATION THERMAL-DECOMPOSITION SUBSTRATE-TEMPERATURE wave-guides LOW-K POLYCARBONATES

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