在具有强非线性效应的离子晶体中光脉冲传播的孤立子特性

从理论上研究了原胞内存在强离子间非线性相互作用的离子晶体,得出光脉冲在其中的传播具有孤立子特性,并分析了当非线性系数g分别为大于0与小于0时形成的亮孤立子与暗孤立子的具体特征.研究表明,不论非线性系数g取正值还是负值,在纵光学模声子频率ωLO以上频区,光脉冲可形成亮孤立子,在g>0时,在横光学模频率ωTO以下频区可形成暗孤立子;值得注意的是在ωTO—ωLO区间,光脉冲可形成超前型暗孤立子;在g<0时,从ωTO往下临近ωTO有一个由超前型亮孤立子向推迟型暗孤立子的转变区 关键词： 孤立子 极化激元 光脉冲     

Numerical analysis of plasmon polarition refractive index fiber sensors with hollow core and a long period grating

The main principle of this design is based on the efficient energy transfer between the waveguide mode (WM) and the co-directional SPP provided by a properly designed fiber long period grating (LPG). This LPG is imprinted into a waveguide fiber layer of a specially designed hollow core optical fiber. The simulations are based on the finite element method (FEM) algorithm in electromagnetics and coupled mode theory for gratings. Compared to the previous proposed structure using a fiber Bragg grating (FBG), this novel kind of sensor can greatly enhance the refractive index sensitivity, e.g., from 5.93 nm/RIU (with FBG) to 817 nm/RIU (with LPG) at the sensing refractive index of 1.40. The other advantage is that the working conditions can be performed for the well-developed telecom wavelength windows 1500-1600 nm.     

Design and analysis of a vertical directional coupler between a three-dimensional plasmonic slot waveguide and a silicon waveguide

The design of a vertical directional coupler between a three-dimensional plasmonic slot waveguide and a silicon waveguide is theoretically investigated in detail. It consists of two steps: the design of isolated plasmonic slot waveguide and silicon waveguide and the determination of the gap between the two waveguides and the length of a coupling region. The designed structure transfers 70.8% of the power carried by the silicon waveguide mode to the plasmonic slot waveguide mode when the gap is 150 nm and the coupling length is 2.14 μm. The wavelength dependence of our vertical directional coupler is also studied. The analysis shows that the amount of the transferred power changes slightly over a very wide wavelength range between 1.40 μm and 1.61 μm. Moreover, if we employ the fabrication technology for silicon photonics, it is quite tolerant to the variation of the length of its coupling section. Finally, the vertical directional coupler is considered for a polarizer.     

损耗对表面等离子体激元压缩态的影响

表面等离子体激元是金属表面电子集体振荡,它以波的形式在金属和介质之间的界面中传播.近期Huck等证明等离子体激元可以处在压缩态,本文利用量子光学的热库理论,研究金波导损耗对表面等离子体激元压缩态的影响,并对Huck等的实验结果给与理论解释. 关键词： 表面等离子体激元 压缩态 热库理论     

Dielectric substrate effect on the metamaterial resonances in terahertz frequency range

We report on the effect of dielectric substrate on the resonance shift of metallic metamaterials operating in the terahertz frequency region. The resonance frequencies for various metamaterials obtained by time-domain spectroscopy agree well with calculations based on the finite-difference time-domain method. The dependencies of the resonance frequency to substrate index are studied, and are systematically determined by introducing an effective substrate index. The relative contributions of the substrate index for various metamaterials are obtained by fitting the numerically obtained effective refractive indices as a function of substrate index, which is found to be ∼0.63 regardless of the metamaterial geometry.     

利用蛾眼结构提高有机太阳能电池光吸收效率的理论研究

为提高有机太阳能电池(OSCs)的能量转换效率,将蛾眼微结构应用于OSCs上.通过理论模拟计算,得出在有机层厚度一定的情况下,带有蛾眼微结构的OSCs相比于普通平板结构的OSCs的光吸收效率有较大的提高.通过对微结构形貌、周期和高度的优化,使蛾眼结构OSCs的光吸收效率比普通平板OSCs提高了11.3％.器件光场分布的模拟计算表明,光吸收效率的提高是由蛾眼结构减反增透的效果和表面等离子体(SPP)增强吸收共同导致的结果.     

Formation and electrochemical desorption of self‐assembled monolayers as studied by ToF‐SIMS

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was used to study a number of processes involving thiol‐based self‐assembled monolayers (SAMs) on nontextured (polycrystalline) gold (Au) films deposited on Si wafers. ToF‐SIMS turned out to be a convenient and versatile semiqualitative technique which readily verified electrochemical desorption of a SAM and formation of another SAM on the same sample via reincubation with another thiol. The technique, allowing one to follow simultaneously more than one species on the surface, showed that any formation of a mixed SAM on surfaces which did not undergo electrolysis was negligible with the applied time scale (minutes). Copyright © 2010 John Wiley & Sons, Ltd.     

采用飞秒激光诱导制备彩色金属

采用脉宽为35～65fs,中心波长为800nm的飞秒脉冲激光对经抛光的镍片进行表面扫描处理,并在金属表面上制备了彩色镍图案;设置不同的激光扫描速度和能量密度扫描处理不锈钢表面,亦制备了彩色图案。介绍了实验过程,分析了实验结果,扫描电子显微镜（SEM）形貌分析显示,经过飞秒激光扫描处理的金属表面出现了纳米量级的激光诱导周期表面结构（NC—LIPSS）,在镍上形成的结构周期约为480—510nm,在不锈钢上形成的结构周期约为480～540nm。