2,779 research outputs found
‐like defect in the Fano–Anderson model with two Fano defects
No full textWe study theoretically the propagation of waves in a discrete linear chain with two side-coupled Fano defects and one d-like defect, using a modified FanoAnderson model. Two separate cases, where the Fano defects are coupled to the chain by on-site coupling or by inter-site coupling, are considered. We find that the transmission behavior is very sensitive to whether the distance between the Fano defects and the d-like defect, l, is even or odd. In the on-site coupling case, we find that for even values of l, the FanoFeshbach resonance is sustained in the presence of a d-like defect, but the position of the transmission peak is shifted and its shape becomes asymmetric. In the inter-site coupling case, the width of the asymmetric Fano resonance can be tuned by changing the coupling constants. When l is odd in the inter-site coupling case, we find that there exist two resonant transmissions in addition to the perfect reflection. In general, the d-like defect strongly influences on the transmission resonance but does not alter the perfect reflectio
Enhanced localization of waves in one-dimensional random media due to nonlinearity: Fixed input case
No full textWe study the influence of nonlinearity on wave localization in one-dimensional random media. Using a discrete nonlinear Schrodinger equation with a random on-site energy term, we calculate the localization length in a numerically exact manner. Unlike in many previous works, we fix the intensity of the incident wave and calculate quantities as a function of other parameters. We find that localization is enhanced due to nonlinearity for the focusing and defocusing nonlinearities. For small nonlinearity, the localization length is a decreasing function of nonlinearity. For sufficiently large nonlinearity, however, the localization length is found to approach a saturation value. (C) 2011 Elsevier B.V. All rights reserve
Nonreciprocal frequency doubling of electromagnetic waves through double resonance and Bragg reflection in photonic crystals
No full textA computational study of the uni-directional second-harmonic generation in a one-dimensional dual photonic crystal structure made of GaAs, AlAs and SiO(2) with quadratic optical nonlinearity and material dispersion is presented. The computational approach uses a shooting method to solve nonlinear wave equations for coupled fundamental and second-harmonic fields and the invariant imbedding method to obtain the linear transmittance and group index spectra. The dual structure consists of two substructures, the conversion structure creating a strongly enhanced second-harmonic signal and the filter structure blocking the fundamental frequency field by Bragg reflection while permitting the passage of the second-harmonic field. The conversion structure is built with an elementary cell consisting of four sublayers whose thicknesses are systematically varied. Doubly resonant second-harmonic generation with very high conversion efficiency is achieved for light incident from the conversion structure side by choosing the geometrical parameters of the elementary cell optimally and controlling the band structure. A new mechanism to enhance second-harmonic generation by controlling the energy flow between the fundamental frequency and second-harmonic fields has also been found. (C) 2011 Elsevier B. V. All rights reserve
Computational design of one-dimensional nonlinear photonic crystals with material dispersion for efficient second-harmonic generation
No full textA computational study of the second-harmonic generation in one-dimensional photonic crystals made of GaAs and AlAs with quadratic optical nonlinearity and material dispersion is presented. The computational approach uses a shooting method to solve nonlinear wave equations for coupled fundamental and second-harmonic fields and the invariant imbedding method to obtain the linear transmittance and group index spectra. The photonic crystal is built with an elementary cell consisting of four sublayers whose thicknesses are systematically varied. Doubly-resonant second harmonic generation with high conversion efficiency is achieved by choosing the geometrical parameters of the elementary cell optimally and controlling the band structure. (C) 2009 Optical Society of Ameri
Novel Anti-Reflection Technology for GaAs Single-Junction Solar Cells Using Surface Patterning and Au Nanoparticles
No full textSingle-junction GaAs solar cell structures were grown by low-pressure MOCVD on GaAs (100) substrates. Micro-rod arrays with diameters of 2 mu m, 5 mu m, and 10 mu m were fabricated on the surfaces of the GaAs solar cells via photolithography and wet chemical etching. The patterned surfaces were coated with Au nanoparticles using an Au colloidal solution. Characteristics of the GaAs solar cells with and without the micro-rod arrays and Au nanoparticles were investigated. The short-circuit current density of the GaAs solar cell with 2 mu m rod arrays and Au nanoparticles increased up to 34.9% compared to that of the reference cell without micro-rod arrays and Au nanoparticles. The conversion efficiency of the GaAs solar cell that was coated with Au nanoparticles on the patterned surface with micro-rod arrays can be improved from 14.1% to 19.9% under 1 sun AM 1.5G illumination. These results show that micro-rod arrays and Au nanoparticle coating can be applied together in surface patterning to achieve a novel cost-effective anti-reflection technolog
Yves-Heng Lim
No full textYves-Heng Lim est enseignant-chercheur au Département d’Etudes de Sécurité et de Criminologie de l’Université Macquarie, Sydney. Il est l’auteur de China’s Naval Power: An Offensive Realist Approach (Ashgate, 2014). Yves-Heng Lim is a lecturer at the Department of Security Studies and Criminology, Macquarie University. He is the author of China’s Naval Power: An Offensive Realist Approach (Ashgate, 2014)
Off-resonant third-order optical nonlinearities of Au : SiO2 nanocomposite films
No full textMetal nanocomposites containing An nanoparticles embedded in SiO2 were deposited on fused silica substrates by alternating sputtering of SiO2 and An at a substrate temperature of 300 degrees C and a constant volume fraction of 1 %. The nanocomposite films were prepared with different An mean diameters between 2.3 nm and 5.7 nm while the overall thickness was kept constant at 600 nm. The linear absorption peaks induced by surface plasmon resonance were shifted toward longer wavelengths from 500 nm to 560 nm with increasing Au particle sizes. To estimate third-order optical nonlinearities of the Au:SiO2 nanocomposite films, such as nonlinear refraction and nonlinear absorption at off-resonant wavelengths, we applied the z-scan technique by using laser pulses from a Kerr lens mode-locked femtosecond Ti:sapphire laser at 780 nm and 820 nm and its second harmonics at 410 nm. The sign and the magnitude of experimentally obtained off-resonant third-order susceptibilities were compared with the theoretical result
Professional attachment report [with] Chio Lim & Associates.
No full textThis report serves as a summary of the professional attachment. Besides touching on author experiences working with Chio Lim & Associates (CLA), it wil also touch on other issues before, during and after the program
Energetics, timescales, and chemistry of low energy molecular ion-organic surface collisions
No full textEnhanced ultrafast optical nonlinearity of porous anodized aluminum oxide nanostructures
No full textEnhanced ultrafast optical nonlinearities of porous anodized aluminum oxide (AAO) nanostructures, well-known templates for quantum dots fabrication, have been investigated using the differential optical Kerr gate technique at 800 nm. The optical nonlinearity is strongly influenced by the pore number density, the pore size and the shape. Large values of the third-order nonlinear optical susceptibility (chi((3))) of the order of 10(-10) esu are measured. The nonlinear response time is faster than or comparable to the laser pulse width (90 fs) used. The origin and variation of such remarkable optical nonlinearities has been discussed by considering the nanoporous AAO as an effective medium and utilizing the extended Maxwell Garnet theory, and by considering the additional influence from pore diameter, pore shape and surface states. (C) 2009 Optical Society of Ameri
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