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Controlled erbium incorporation and photoluminescence of Er-doped Y₂O₃ -: art. no. 011907

APPLIED PHYSICS LETTERS 2005年第1期87卷 1907-1-1907-3页

作者： Van, TT Chang, JP Univ Calif Los Angeles Dept Chem Engn Los Angeles CA 90095 USA

A high concentration of erbium doping was achieved in Y2O3 thin films on Si (100) by depositing Y2O3 alternatively with Er2O3 using radical-enhanced atomic layer deposition (ALD). Specifically, the erbium doping level was controlled by varying the ratio of Y2O3:Er2O3 cycles during deposition, and a 10:5 ratio yielded similar to 9 at. % erbium incorporation in Y2O3, confirmed by the compositional analysis using x-ray photoelectron spectroscopy. Room-temperature photoluminescence was observed in a 320-A Er-doped (9 at. %) Y2O3 film deposited at 350 degrees C. This result is very promising, since the film was fairly thin and no annealing at high temperature was needed to activate the erbium ions. This suggests that radical-enhanced ALD was able to preserve the optically active trivalent state of the erbium ion from its precursor state. The effective absorption cross section for Er3+ ions incorporated in Y2O3 was estimated to be on the order of 10(-18) cm(2), about three orders of magnitude larger than the direct optical absorption cross section reported for Er3+ ions in a stoichiometric SiO2 host. These results validate Y2O3 as a promising Er3+ host material and demonstrate that radical-enhanced ALD is a viable technique for synthesizing these materials. (c) 2005 American Institute of Physics.

关键词： ATOMIC LAYER DEPOSITION wave-guides FILMS SILICON LUMINESCENCE SI

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Measurement of the phase shift upon reflection from photonic crystals

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APPLIED PHYSICS LETTERS 2005年第15期86卷 1112-1-1112-3页

作者： Istrate, E Sargent, EH Univ Toronto Dept Elect & Comp Engn Toronto ON M5S 3G4 Canada

The phase dependence of light reflected from colloidal photonic crystals is measured using a large resonant cavity and self-assembled colloidal photonic crystals. We measure the expected phase shift upon reflection from the photonic crystal, which varies from 0 to 180 deg across the photonic crystal stop band. These measurements are then fed directly into the design of photonic crystal cavities. We obtain a measure for the precision needed in the fabrication of photonic crystal resonant cavities. (C) 2005 American Institute of Physics.

关键词： wave-guides

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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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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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Hybrid superprism with low insertion losses and suppressed cross-talk

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Physical Review E 2005年第2期71卷 026604-026604页

作者： Jeremy Witzens Thomas Baehr-Jones Axel Scherer Department of Electrical Engineering California Institute of Technology Mail Code 136-93 Pasadena California 91125 USA

We demonstrate with the two-dimensional finite-difference time-domain method that an adiabatic transition in a superprism with an interface along the [12¯] direction enhances the transmission through the superprism to more than 90% (−0.5dB) over the wavelength range 1.47–1.68 μm, including the telecommunication C and L bands. We also show that diffraction governed by a quasinegative index of refraction inside the superprism can be used to obtain nearly transform-limited beam widths at the output of the superprism. The reduction of the beam width at the output suppresses cross-talk and greatly enhances the achievable frequency resolution of the superprism.

关键词： PLANAR-PHOTONIC CRYSTALS SELF-COLLIMATED BEAMS NEGATIVE REFRACTION wave-guides MODE TRANSMISSION PROPAGATION EFFICIENCY

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Quantum scattering in quasi-one-dimensional cylindrical confinement

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Physical Review A 2005年第4期72卷 042711-042711页

作者： J. I. Kim J. Schmiedmayer P. Schmelcher Physikalisches Institut Universität Heidelberg Philosophenweg 12 69120 Heidelberg Germany Theoretische Chemie Institut für Physikalische Chemie Universität Heidelberg Im Neuenheimer Feld 229 69120 Heidelberg Germany

Finite-size effects not only alter the energy levels of small systems, but can also lead to additional effective interactions within these systems. Here the problem of low-energy quantum scattering by a spherically symmetric short-range potential in the presence of a general cylindrical confinement is investigated. A Green’s function formalism is developed which accounts for the full three-dimensional (3D) nature of the scattering potential by incorporating all phase shifts and their couplings. This quasi-1D geometry gives rise to scattering resonances and weakly localized states, whose binding energies and wave functions can be systematically calculated. Possible applications include, e.g., impurity scattering in ballistic quasi-1D quantum wires in mesoscopic systems and in atomic matter-wave guides. In the particular case of parabolic confinement, the present formalism can also be applied to pair collision processes such as two-body interactions. Weakly bound pairs and quasimolecules induced by the confinement and having zero or higher orbital angular momentum can be predicted, such as p- and d-wave pairings.

关键词： TONKS-GIRARDEAU GAS IMPENETRABLE BOSONS NEUTRAL ATOMS TRAPPED GASES wave-guides TRANSMISSION REFLECTION OBSTACLE OPTICS WIRES

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Onset of chaotic symbolic synchronization between population inversions in an array of weakly coupled Bose-Einstein condensates

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Physical Review E 2005年第5期71卷 056201-056201页

作者： C. L. Pando L. E. J. Doedel Concordia University 1455 Boulevard de Maisonneuve West Montreal Quebec Canada H3G 1M8

We investigate the onset of chaotic dynamics of the one-dimensional discrete nonlinear Schrödinger equation with periodic boundary conditions in the presence of a single on-site defect. This model describes a ring of weakly coupled Bose-Einstein condensates with attractive interactions. We focus on the transition to global stochasticity in three different scenarios as the defect is changed. We make use of a suitable Poincaré section and study different families of stationary solutions, where certain bifurcations lead to global stochasticity. The global stochasticity is characterized by chaotic symbolic synchronization between the population inversions of certain pairs of condensates. We have seen that the Poincaré cycles are useful to gain insight in the dynamics of this Hamiltonian system. Indeed, the return maps of the Poincaré cycles have been used succesfully to follow the orbit along the stochastic layers of different resonances in the chaotic self-trapping regime. Moreover, the time series of the Poincaré cycles suggests that in the global stochasticity regime the dynamics is, to some extent, Markovian, in spite of the fact that the condensates are phase locked with almost the same phase. This phase locking induces a peculiar local interference of the matter waves of the condensates.

关键词： NONLINEAR SCHRODINGER-EQUATION SELF-TRAPPING EQUATION wave-guides LATTICES INTERFERENCE TRANSITION BREATHERS DIFFUSION STABILITY EXPONENTS

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Pulse duration dependence of femtosecond-laser-fabricated nanogratings in fused silica

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APPLIED PHYSICS LETTERS 2005年第1期87卷 4104-1-4104-3页

作者： Hnatovsky, C Taylor, RS Rajeev, PP Simova, E Bhardwaj, VR Rayner, DM Corkum, PB Natl Res Council Canada Inst Microstruct Sci Ottawa ON K1A 0R6 Canada Natl Res Council Canada Steacie Inst Mol Sci Ottawa ON K1A 0R6 Canada

Femtosecond laser radiation tightly focused in bulk fused silica is used to generate self-ordered nanogratings when the sample is translated under the lens at constant speed. The nanogratings are preserved over a length scale of millimeters. We demonstrate that nanogratings are formed for all pulse durations tested, ranging from 40 to 500 fs, and that the pulse energy threshold for this phenomenon increases with decreasing pulse duration. We use high spatial resolution diagnostics based upon selective chemical etching followed by atomic force microscopy and scanning electron microscopy to reveal the morphology of the nanogratings. (c) 2005 American Institute of Physics.

关键词： wave-guides TRANSPARENT MATERIALS INDUCED BREAKDOWN DIELECTRICS DAMAGE INDEX GLASS

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Resonator mode in chains of silver spheres and its possible application

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Physical Review E 2005年第6期72卷 066606-066606页

作者： C. R. Simovski A. J. Viitanen S. A. Tretyakov Radio Laboratory/SMARAD Helsinki University of Technology FI-02015 TKK Finland

A transversal mode with zero group velocity and nonzero phase velocity that can exist in chains of silver nanospheres in the optical frequency range is theoretically studied. It is shown that the external source radiating a narrow-band nonmonochromatic signal can excite in the chain a mixture of standing and slowly traveling waves. The standing-wave component (named the resonator mode) is strongly dominating. The physical reason for such a regime is a sign-varying distribution of power flux over the cross section of the chain. A possible application of the resonator mode for evanescent-wave enhancement and for subwavelength imaging in the visible is discussed.

关键词： wave-guides REFRACTION INDEX

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UV-Vis, FT-IR and EPR investigation on multi-component germano-silicate glasses for photonics

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JOURNAL OF NON-CRYSTALLINE SOLIDS 2004年第1-3期347卷 246-253页

作者： Ferraris, M Milanese, D Contardi, C Chen, Q Menke, Y Politecn Torino Dept Mat Sci & Chem Engn I-10129 Turin Italy

Photosensitive multi-component germano-silicate glasses, with or without sodium and boron ions in their composition, were studied by means of UV-Vis, FT-IR, and EPR spectroscopy in order to assess the structural changes occurring in the glasses under UV laser irradiation at 248 nm (KrF excimer UV laser). A new absorption band at 285 nm was found for high sodium containing germano-silicate glasses;this band is bleached after UV laser irradiation at 248 nm. (C) 2004 Elsevier B.V. All rights reserved.

关键词： BRAGG GRATING INSCRIPTION OPTICAL-FIBER PHOTOSENSITIVE GLASS GEO2-SIO2GLASSES EXCIMER-LASER wave-guides CENTERS IRRADIATION GENERATION ABSORPTION

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