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Design of an integrated optical source of twin photons

Physical Review A 2005年第3期71卷 033812-033812页

作者： Ivan Avrutsky Alexander V. Sergienko Department of Electrical & Computer Engineering and Department of Physics Boston University Boston Massachusetts 02215 USA

The phase matching for the nonlinear process of frequency-degenerated spontaneous parametric downconversion in tunneling-coupled channel waveguides is analyzed. The use of type II nonlinear interaction with individual photons in each pair appearing in different output channels allows for constructing polarization entangled states for quantum information processing applications.

关键词： wave-guides 2ND-HARMONIC GENERATION QUANTUM COMMUNICATION BETA-BBO BORATE PAIRS MODES

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Cadmium telluride bulk crystal as an ultrafast nonlinear optical switch

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APPLIED PHYSICS LETTERS 2005年第25期87卷 51110-1-51110页

作者： Tatsuura, S Matsubara, T Mitsu, H Sato, Y Iwasa, I Tian, MQ Furuki, M Fuji Xerox Co Ltd Corp Res Lab Kanagawa 2590157 Japan

A semiconductor bulk crystal has several advantages as a nonlinear optical material, such as low processing cost, long interaction length, and alleviation of the free-carrier absorption caused by two-photon absorption (TPA). We examine optical properties of semiconductor bulk crystals with different orientations at 1.55 mu m and find that CdTe[111] has favorable capabilities, such as nonlinear refractive index of 5.23x10(-17) (m(2) W), TPA coefficient of 18.3 (mm GW), and consequent figure of merit of 0.54. Optical three-dimensional measurements of reflective material are carried out using CdTe[111] as ultrafast optical Kerr shutter and clear images corresponding to surface steps are obtained. (c) 2005 American Institute of Physics.

关键词： MULTIPLE-QUANTUM WELLS 1.55 MU-M 2-PHOTON ABSORPTION ZINCBLENDESEMICONDUCTORS wave-guides SILICON ANISOTROPY

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Compact strain-sensitive flexible photonic crystals for sensors

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APPLIED PHYSICS LETTERS 2005年第10期87卷 1902-1-1902-3页

作者： Pursiainen, OLJ Baumberg, JJ Ryan, K Bauer, J Winkler, H Viel, B Ruhl, T Univ Southampton Sch Phys & Astron Southampton SO17 1BJ Hants England Merck Chem Southampton SO16 7QD Hants England Merck KGaA D-64291 Darmstadt Germany DKI D-64289 Darmstadt Germany

A promising fabrication route to produce absorbing flexible photonic crystals is presented, which exploits self-assembly during the shear processing of multi-shelled polymer spheres. When absorbing material is incorporated in the interstitial space surrounding high-refractive-index spheres, a dramatic enhancement in the transmission edge on the short-wavelength side of the band gap is observed. This effect originates from the shifting optical field spatial distribution as the incident wavelength is tuned around the band gap, and results in a contrast up to 100 times better than similar but nonabsorbing photonic crystals. An order-of-magnitude improvement in strain sensitivity is shown, suggesting the use of these thin films in photonic sensors. (c) 2005 American Institute of Physics.

关键词： COLLOIDAL SYSTEMS wave-guides OPALS SPHERES

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Dynamical model of coherent circularly polarized optical pulse interactions with two-level quantum systems

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Physical Review A 2005年第5期72卷 053804-053804页

作者： G. Slavcheva O. Hess Advanced Technology Institute School of Electronics and Physical Sciences University of Surrey Guildford GU2 7XH Surrey United Kingdom

We propose and develop a method for theoretical description of circularly (elliptically) polarized optical pulse resonant coherent interactions with two-level atoms. The method is based on the time-evolution equations of a two-level quantum system in the presence of a time-dependent dipole perturbation for electric dipole transitions between states with total angular-momentum projection difference (ΔJz=±1) excited by a circularly polarized electromagnetic field [Feynman et al., J. Appl. Phys. 28, 49 (1957)]. The adopted real-vector representation approach allows for coupling with the vectorial Maxwell’s equations for the optical wave propagation and thus the resulting Maxwell pseudospin equations can be numerically solved in the time domain without any approximations. The model permits a more exact study of the ultrafast coherent pulse propagation effects taking into account the vector nature of the electromagnetic field and hence the polarization state of the optical excitation. We demonstrate self-induced transparency effects and formation of polarized solitons. The model represents a qualitative extension of the well-known optical Maxwell-Bloch equations valid for linearly polarized light and a tool for studying coherent quantum control mechanisms.

关键词： SELF-INDUCED TRANSPARENCY SEMICONDUCTOR MICROCAVITIES wave-guides

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Nonadiabatic dynamics of a Bose-Einstein condensate in an optical lattice

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Physical Review A 2005年第1期72卷 011601(R)-011601(R)页

作者： Lorenzo Isella Janne Ruostekoski Department of Physics Astronomy and Mathematics University of Hertfordshire Hatfield Herts AL10 9AB United Kingdom

We study the nonequilibrium dynamics of a Bose-Einstein condensate that is split in a harmonic trap by turning up a periodic optical lattice potential. We evaluate the dynamical evolution of the phase coherence along the lattice and the number fluctuations in individual lattice sites within the stochastic truncated Wigner approximation when several atoms occupy each site. We show that the saturation of the number squeezing at high lattice strengths, which was observed in recent experiments by Orzel et al. [Science 291, 2386 (2001)] can be explained by the nonadiabaticity of the splitting.

关键词： BOGOLIUBOV APPROACH QUANTUM-NOISE wave-guides ATOMS TRANSITION SUPERFLUID INSULATOR ARRAYS GAS

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Modulational instability and unstable patterns in the discrete complex cubic Ginzburg-Landau equation with first and second neighbor couplings

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Physical Review E 2005年第3期72卷 036220-036220页

作者： Alidou Mohamadou A. Kenfack Jiotsa T. C. Kofané Laboratoire de Mécanique Département de Physique Faculté des Sciences Université de Yaoundé I B.P. 812 Yaoundé Cameroun The Abdus Salam International Centre for Theoretical Physics P.O. Box 586 Strada Costiera 11 I-34014 Trieste Italy

The generation of nonlinear modulated waves is investigated in the framework of hydrodynamics using a model of coupled oscillators. In this model, the separatrices between each pair of vortices may be viewed as individual oscillators and are described by a phenomenological one-dimensional discrete complex Ginzburg-Landau equation involving first- and second-nearest neighbor couplings. A theoretical approach based on the linear stability analysis predicts regions of modulational instability, governed by both the first and second-nearest neighbor couplings. From numerical investigations of different wave patterns that may be driven by the modulational instability, it appears that analytical predictions are correctly verified. For wave number in the unstable regions, an initial condition whose amplitude is slightly modulated breaks into a train of unstable patterns. This phenomenon agrees with the description of amplification of the spectral component of the perturbation and its harmonics, as well.

关键词： SEMICONDUCTOR-LASER ARRAYS BINARY-FLUID CONVECTION LINEAR-ARRAY wave-guides VORTICES SYSTEM ELECTROCONVECTION SELECTION SOLITONS STATES

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Conductance of photons in disordered photonic crystals

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Physical Review E 2005年第3期71卷 036623-036623页

作者： A. A. Asatryan L. C. Botten M. A. Byrne T. N. Langtry N. A. Nicorovici R. C. McPhedran C. Martijn de Sterke P. A. Robinson School of Physics University of Sydney New South Wales 2006 Australia

The conductance of photons in two-dimensional disordered photonic crystals is calculated using an exact multipole–plane wave method that includes all multiple scattering processes. Conductance fluctuations, the universal nature of which has been established for electrons in the diffusive regime, are studied for photons, in both principal polarizations and for varying disorder. Our simulations show that universal conductance fluctuations can be observed in H‖ (TE) polarization for weak and intermediate disorder while, for E‖ (TM) polarization, we show that the conductance variance is essentially independent of sample size but strongly dependent on disorder. The probability distribution of the conductance is also calculated in the diffusive and localized regimes, and also at their transition, for which the distributions for both polarizations are seen to be very similar.

关键词： RANDOM-MATRIX THEORY PROBABILITY-DISTRIBUTION ELECTROMAGNETIC SCATTERING DIELECTRIC CYLINDERS TOTAL TRANSMISSION GRATING STACKS SCALING THEORY MOBILITY EDGE wave-guides FLUCTUATIONS

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Optical microfiber loop resonator

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APPLIED PHYSICS LETTERS 2005年第16期86卷 161108.1-161108.3页

作者： Sumetsky, M Dulashko, Y Fini, JM Hale, A OFS Labs Somerset NJ 08873 USA

We experimentally demonstrate an optical microfiber loop resonator. The resonator was formed in free space by creating a loop from the subwavelength-diameter waist of a short biconical optical fiber taper. The loop length was chosen so that the free spectrum range of the resonator was ∼ 100 GHz at the optical communication wavelengths near 1.5 μ m. In order to change and optimize the spectral characteristics such as the effect of birefringence, the shape of resonances, and the free spectrum range, we manually varied the microfiber self-coupling by alignment of the input and output ends of the loop, which were attached to each other by Van der Waals and electrostatic forces. In particular, we tuned the microfiber loop resonator to exhibit resonances with a Q-factor exceeding 15 000 (finesse ≈ 10) and, also, to the regime of critical coupling with the extinction ratio of transmission oscillations exceeding 34 dB. This paper was in press when we achieved the values of 95 000 and 630 000 for the loaded and intrinsic Q-factor, respectively (see note added in proof). We believe that the demonstrated Q-factor can be significantly enhanced with the more uniform microfiber. © 2005 American Institute of Physics.

关键词： wave-guides DISPERSION COUPLERS FILTERS DELAY

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Rotating photonic crystals: A medium for compact optical gyroscopes

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Physical Review E 2005年第5期71卷 056621-056621页

作者： Ben Zion Steinberg []School of Electrical Engineering Tel Aviv University Ramat-Aviv Tel-Aviv 69978 Israel

The effect of rotation of a photonic crystal that contains a set of microcavities is studied using the formulation of electrodynamics in rotating media. A new manifestation of the Sagnac effect is observed. It is shown that the phase shift or frequency difference between rotation-codirected and rotation-counterdirected propagations depends on a set of parameters not previously reported. The use of the new configuration for designing compact optical gyroscopes is studied and discussed.

关键词： RIGID VIBRATIONS wave-guides SYSTEMS

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Semianalytic approach for analyzing coupling issues in photonic crystal structures

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APPLIED PHYSICS LETTERS 2005年第20期87卷 3107-1-3107-3页

作者： Sanchis, P Marti, J Bienstman, P Baets, R Univ Politecn Valencia Nanophoton Technol Ctr Valencia 46022 Spain Univ Ghent Interuniv Microelect Ctr Dept Informat Technol B-9000 Ghent Belgium

A semianalytic approach based on previously derived closed-form expressions for the transmission and reflection matrices between a dielectric waveguide and a semi-infinite photonic crystal (PhC) waveguide is proposed for analyzing coupling issues in PhC structures. The proposed approach is based on an eigenmode expansion technique and introduces several advantages with respect to other conventional numerical methods such as a shorter computation time and the possibility to calculate parameters, such as the reflection into PhC structures, difficult to obtain with others methods. Two different examples are analyzed and results compared to finite-difference time-domain simulations to prove the usefulness of the proposed approach: (i) An especially designed two-defects configuration placed within a PhC taper to improve the coupling efficiency and (ii) a coupled-cavity waveguide coupled to a single-line defect PhC waveguide. (C) 2005 American Institute of Physics.

关键词： wave-guides CIRCUITS

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