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Aluminum co-doping of soda-lime silicate glasses: Effect on optical and spectroscopic properties

JOURNAL OF NON-CRYSTALLINE SOLIDS 2005年第21-23期351卷 1747-1753页

作者： Berneschi, S Bettinelli, M Brenci, M Conti, GN Pelli, S Sebastiani, S Siligardi, C Speghini, A Righini, GC IFAC CNR Nello Carrara Inst Appl Phys Optoelect & Photon DeptCNR I-50127 Florence Italy Univ Bologna DEIS I-40100 Bologna Italy Univ Verona Sci & Technol Dept I-37134 Verona Italy Univ Modena DIMA I-41100 Modena Italy

One of the limits of using silicate glasses as a host for Er3+ is the emission bandwidth, which is smaller than in the case of other oxide glasses, such as phosphates and tellurites. The bandwidth can be increased by adding aluminum to the composition. Here we present an experimental investigation of the effect of increasing aluminum content on optical and spectroscopic properties of this glass. Glass samples were prepared by melting at 1550 degrees C reagent grade SiO2, Al2O3, Na2CO3, K2CO3, CaCO3, (NH4)(3)PO4 and Er2O3;Al2O3 concentration ranged from 0.99 to 20 mol%. Both heating and cooling rates were equal to 0.17 degrees C s(-1). Measurements of the fluorescence bandwidth were then made and as a function of alumina content. Judd-Ofelt analysis was performed and calculated radiative lifetimes were compared with experimental ones. Planar waveguides were also fabricated by using ion-exchange technology, and some optical properties measured by the prism coupling technique. These waveguides had losses of the order of 1 dB/cm at 635 nm. (c) 2005 Elsevier B.V. All rights reserved.

关键词： RARE-EARTH IONS wave-guides LOCAL-STRUCTURE DOPED GLASSES AMPLIFIERS AL2O3 INTENSITIES EXCHANGE LASERS TRANSITIONS

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Investigation of the role of silver on spectroscopic features of Er³⁺-activated Ag-exchanged silicate and phosphate glasses

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JOURNAL OF NON-CRYSTALLINE SOLIDS 2005年第21-23期351卷 1738-1742页

作者： Portales, H Mattarelli, M Montagna, M Chiasera, A Ferrari, M Martucci, A Mazzoldi, P Pelli, S Righini, GC Univ Trent Dipartimento Fis I-38050 Povo TN Italy CSMFO INFM I-38050 Povo TN Italy CSMFO Grp Ist Foton & Nanotecnol CNR IFN Povo TN Italy Univ Padua Dip Ingn Meccan S Mat INSTM I-35131 Padua Italy Univ Padua Dipartimento Fis I-35131 Padua Italy INFM I-35131 Padua Italy CNR IFAC Inst Appl Phys Nello Carrara I-50127 Florence Italy

We present a spectroscopic investigation on Er/Ag co-doped platelets of silicate and phosphate glasses with the aim of assessing the effect of silver as a sensitizer for erbium. The silver was added by immersing the samples, at 663 K for 67 h, in a molten salt bath of molar concentration 0.5% AgNO3 and 99.5% NaNO3. Additive heat treatments in air at different temperatures, ranging from 673 K to 773 K for 30 min and cooling in air after each anneal, were performed on both the silver-exchanged and the silver-free plates. The optical and spectroscopic features of the samples were investigated by photoluminescence measurements in the region of the I-4(13/2) -> I-4(15/2) transition of the Er3+ ion, excitation spectra in the range from 360 to 750 nm, and absorption measurements. Increases of the Er 31 luminescence at 1.5 mu m are demonstrated when the excitation is in an absorption band, located at 420 nm, possibly originating from the surface plasmon resonance of silver particles. (c) 2005 Elsevier B.V. All rights reserved.

关键词： wave-guides FLUORESCENCE PARTICLES ERBIUM

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Coherent nonlinear optics with quantum cascade structures

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JOURNAL OF MODERN OPTICS 2005年第16期52卷 2293-2302页

作者： Belyanin, A Xie, F Liu, DB Capasso, F Troccoli, M Texas A&M Univ Dept Phys College Stn TX 77843 USA Harvard Univ Div Engn & Appl Sci Cambridge MA 02138 USA

We discuss several coherent nonlinear optical phenomena that occur in active quantum-cascade (QC) structures that support both laser action and, at the same time, nonlinear self-conversion of laser light into coherent radiation at other frequencies. In other words, the laser field serves as an intracavity optical pump for a desired nonlinear optical process. In such systems, resonant absorption of the pump field is overcome by laser gain, and giant resonant nonlinearities of the intersubband transitions can be fully exploited. The proposed approach holds promise to extend the operating wavelength of QC lasers to the spectral regions where they become less efficient, constrained by material limitations, or operate only at cryogenic temperatures. It may also lead to the development of new broadly tunable injection-pumped sources. We review recent development in this research direction including the demonstration of the Raman injection laser.

关键词： INTERSUBBAND RAMAN LASER 2ND-HARMONIC GENERATION HARMONIC-GENERATION wave-guides WELLS SUSCEPTIBILITY INVERSION

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Quantum theory of Manakov solitons

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Physical Review A 2005年第5期71卷 053805-053805页

作者： Darren Rand Ken Steiglitz Paul R. Prucnal Department of Electrical Engineering Princeton University Princeton NJ 08544 USA Department of Computer Science Princeton University Princeton NJ 08544 USA

A fully quantum mechanical model of two-component Manakov solitons is developed in both the Heisenberg and Schrödinger representations, followed by an analytical, linearized quantum theory of Manakov solitons in the Heisenberg picture. This theory is used to analyze the vacuum-induced fluctuations of Manakov soliton propagation and collision. The vacuum fluctuations induce phase diffusion and dispersion in Manakov soliton propagation. Calculations of the position, polarization angle, and polarization state fluctuations show an increase in collision-induced noise with a decrease in the relative velocity between the two solitons, as expected because of an increase in the interaction length. Fluctuations in both the polarization angle and state are shown to be independent of propagation distance, opening up possibilities for communications, switching, and logic, exploiting these properties of Manakov solitons. Calculations of the phase noise reveal, surprisingly, that the collision-induced fluctuations can be reduced slightly below the level of fluctuations in the absence of collision, due to cross-correlation effects between the collision-induced phase and amplitude fluctuations of the soliton. The squeezing effect of Manakov solitons is also studied and proven, unexpectedly, to have the same theoretical optimum as scalar solitons.

关键词： DEPENDENT HARTREE APPROXIMATION OPTICAL SOLITONS LINEARIZATIONAPPROXIMATION NONDEMOLITION MEASUREMENT PULSE-PROPAGATION NONLINEAR MEDIUM VECTOR SOLITONS wave-guides KERR MEDIUM FIBERS

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Green’s function for photonic crystal slabs

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Physical Review E 2005年第2期72卷 026614-026614页

作者： Li-Ming Zhao Xue-Hua Wang Ben-Yuan Gu Guo-Zhen Yang Institute of Physics Chinese Academy of Sciences P. O. Box 603 Beijing China

Green’s tensors for photonic crystal (PC) slabs are numerically solved by the coupled-dipole approximation (CDA) technique. The obtained components of Green’s tensors satisfy discontinuous or continuous conditions at interfaces of scatterers. This shows that the CDA technique is very applicable to studying the properties of PC slabs. Green’s tensors exhibit obviously periodic oscillation with the increase of the number of scatterers; furthermore, the effect of each scatterer on Green’s tensors displays a localization feature in the sample containing one row of scatterers; on the contrary, this localized effect disappears in the sample consisting of multiple rows of scatterers.

关键词： DISCRETE-DIPOLE APPROXIMATION INHIBITED SPONTANEOUS EMISSION GENERALIZEDFIELD PROPAGATOR BAND-GAP ELECTROMAGNETIC SCATTERING DIELECTRIC STRUCTURES wave-guides LIGHT ATOMS LOCALIZATION

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Out-of-plane dispersion and homogenization in photonic crystal slabs

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APPLIED PHYSICS LETTERS 2005年第19期87卷 191113-1-191113页

作者： Jian, ZP Mittleman, DM Rice Univ Dept Elect & Comp Engn Houston TX 77005 USA

We report a measurement of out-of-plane dispersion in two-dimensional photonic crystal slabs. Using terahertz time-domain spectroscopy, we obtain the complex transmission coefficient over a broad spectrum, ranging from the long wavelength (homogeneous) limit up to beyond the first few guided resonances. Despite the absence of a band gap, the out-of-plane dispersion is significant and in addition exhibits a complicated spectral dependence. Calculations of the effective refractive index which assume translational invariance in the direction perpendicular to the slab are in only approximate agreement with the measured homogeneous effective index and dispersion. In contrast, numerical simulations which accurately account for the finite slab thickness give much more accurate predictions. (C) 2005 American Institute of Physics.

关键词： TIME-DOMAIN SPECTROSCOPY ALL-PASS TRANSMISSION wave-guides MODES PROPAGATION RADIATION RESONANCE

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Codirectional couplers in GaAs-based planar photonic crystals -: art. no. 081108

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APPLIED PHYSICS LETTERS 2005年第8期86卷 1108-1-1108-3页

作者： Leuenberger, D Ferrini, R Dunbar, LA Houdré, R Kamp, M Forchel, A Ecole Polytech Fed Lausanne Inst Photon & Elect Quant CH-1015 Lausanne Switzerland Univ Wurzburg D-97074 Wurzburg Germany

Several designs for codirectional couplers in planar photonic crystals etched into GaAs-based heterostructures were investigated both theoretically and experimentally. Two different numerical techniques, i.e., plane wave expansion and finite difference time domain, were used to calculate the coupling lengths. Both methods are shown to be in good agreement with the experimental results. The measured coupling lengths are in the order of 350 periods, leading to a physical length of the order of 80 Am, much smaller than what is achieved in classical integrated optics couplers. (c) 2005 American Institute of Physics.

关键词： wave-guides DIRECTIONAL-COUPLERS

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Mechanisms supporting long propagation regimes of photorefractive solitons

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Physical Review E 2005年第3期71卷 036610-036610页

作者： Eugenio DelRe Angelo D’Ercole Elia Palange Dipartimento di Fisica Università dell’Aquila 67010 L’Aquila Italy Istituto Nazionale Fisica della Materia Unità di Roma “La Sapienza” 00185 Rome Italy Dipartimento di Ingegneria Elettrica Università dell’Aquila 67040 Monteluco di Roio (L’Aquila) Italy Istituto Nazionale Fisica della Materia Unità dell’Aquila 67010 L’Aquila Italy

We extend investigation of one-dimensional solitons in biased photorefractive crystals to long propagation regimes, where self-trapping over a large number of linear diffraction lengths combines with the progressive growth of generally distortive spatially nonlocal components. Results indicate that saturation halts the radiative misshaping of the soliton, which follows that specific bending trajectory along which its evolution is governed by the same local screening nonlinearity that intervenes in short propagation conditions, where spatial nonlocality has a negligible effect. This finding not only allows the prediction of the curvature and of the relative role of charge displacement and diffusion, but implies a set of interesting observable effects, such as boomerangs, counterpropagating and cavity geometries, quasirectilinear and anomalous collisions, along with specific consequences on soliton arrays and on coupling to bulk gratings.

关键词： SPATIAL SCREENING SOLITONS 2ND-HARMONIC GENERATION OPTICAL BEAMS wave-guides INCOHERENT COLLISIONS SELF-DEFLECTION CRYSTALS MEDIA FIELD MANIPULATION

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Design, fabrication, and characterization of a two-dimensional photonic-crystal symmetric Mach-Zehnder interferometer for optical integrated circuits

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APPLIED PHYSICS LETTERS 2005年第14期86卷 141104-1-141104页

作者： Tanaka, Y Sugimoto, Y Ikeda, N Nakamura, H Kanamoto, K Asakawa, K Inoue, K Femtosecond Technol Res Assoc Tsukuba Ibaraki 3002635 Japan Chitose Inst Sci & Technol Chitose 0668655 Japan Univ Tsukuba Tsukuba Ibaraki 3058577 Japan

We report on the design, fabrication, and optical characterization of a GaAs two-dimensional photonic-crystal-based symmetric Mach-Zehnder interferometer (PC-SMZ) aimed at all-optical switches in planar photonic integrated systems. The directional couplers that constitute the PC-SMZ interferometer prevent the occurrence of ring resonance which degrades the interference, and allow control pulses for the switching operation to be received. We show 50%- and 100%-power couplings from the transmission characteristics of the directional couplers, thus demonstrating their operation as 3-dB dividers in the PC-SMZ. We also show experimentally wavelength selectivity between signal and control pulses with a separation of similar to 7 nm. These results indicate that the structure is promising as an all-optical switch when a nonlinear material such as a quantum dot is introduced into both arms of the interferometer. (C) 2005 American Institute of Physics.

关键词： wave-guides PHASE-SHIFT DEFECT SWITCH BENDS

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Variational approach to spatial optical solitons in bulk cubic-quintic media stabilized by self-induced multiphoton ionization

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Physical Review E 2005年第5期71卷 056615-056615页

作者： C. P. Jisha V. C. Kuriakose K. Porsezian []Department of Physics Cochin University of Science and Technology Cochin 682022 India

Propagation of an optical high-power cylindrically symmetric beam in a material characterized by cubic-quintic nonlinearity is studied both analytically and numerically. In this case we have to consider the self-defocusing effect caused by the presence of free electrons produced due to plasma formation. The variational method is used to study the system analytically. The finite-difference beam propagation method is used for the numerical analysis. Stable (2+1)D spatial solitons are observed. The analytical results are found to be in very good agreement with the numerical results.

关键词： SEMICONDUCTOR-DOPED GLASSES PULSE-PROPAGATION wave-guides LIGHT BEAMS 3RD-ORDER BRIGHT AIR

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