An Optical Parametric Amplifier in Photonic Crystals of Nondispersive Medium with Perfect Bloch Phase Matching

One-dimensional photonic crystal of second-order nonlinearity is studied. Among the three waves of the parametric interaction process of down-conversion with a nondispersive medium, two gap-edge localized modes and one travelling-mode are proposed, and an exact phase matching condition is realized using the periodic condition     

Oxygen Pressure Dependence of Properties of Epitaxial LaAlO3 Films Grown on Si （100）

Heteroepitaxial LaAlO3 films were grown on a SrTiO3/Si (100) substrate by laser molecular beam epitaxy under different oxygen pressures, and their properties such as crystallinity and electrical characteristics were experimentally investigated using the various measurement methods. The results show that most properties depend mainly on the deposition oxygen pressure. The crystallinity and the C-V and I-V characteristics can be greatly improved with the increasing oxygen deposition pressure. Moreover, after annealed at 1050~C in N2 ambient, the C-V and I-V characteristics of LAO films deposited at the lower oxygen pressure are also improved due to the decrease of oxygen vacancies in LAO films.     

Theoretical investigation on near-infrared and visible absorption spectra of nanometallic aluminium with oxide coating in nanoenergetic materials: size and shape effects

The effects of metal core dimension, oxide shell thickness and ellipsoid aspect ratio of Al-Al2O3 core-shell nanoparticles on the near-infrared and visible absorption spectra of nanocomposite Al-Al2O3/nitrocellulose（NC） film are investigated by numerical calculations. Both the size-dependent interband transitions and frequency-dependent free electron damping of the nanometallic aluminium are taken into account in the calculations. Oxidation effect of nanoaluminium is also analysed. It is shown that oxidation may enhance but may also reduce the optical absorption, depending on the excited light energy and initial dimension of nanoparticle. Metal core size and excited light energy dominate the absorption characteristic. The absorption ability of ellipsoidal nanoparticles is larger than that of spheroidal nanoparticles and increases by the square index as the aspect ratio increases. These calculations will provide some significant theoretical guidance for the preparation and laser ignition of nanoenergetic materials.     

平面行波场中多个粒子受到的声辐射力*

从粒子在行波场中的声散射出发,研究当声场中存在稀疏分布的多个粒子时粒子受到的声辐射力,并且给出了适用于声场中任意位置的粒子声辐射力计算公式。由于声辐射力为非线性力,当声场中存在多个粒子时,直接计算粒子受到的声辐射力非常复杂。结果表明,当声场中存在多个稀疏分布的粒子时,这一多粒子系统可以视为多个单独的双粒子系统的叠加,只需要分别计算各个双粒子系统的声辐射力就可以通过叠加得到声场中任意粒子的声辐射力。这一结果有助于利用声辐射力对微小粒子进行精细操控。     

有机材料(EDT-DSDTFVO)FeCl4和(EDT-DSDTFVO)GaCl4的磁电阻分析

有机材料(EDT-DSDTFVO)2FeCl4和(EDT-DSDTFVO)2GaCl4的输送实验结果,显示出这两类盐的电阻率对温度的依赖性以及压力效果十分相似,但是两种盐的磁电阻率却表现出很大的不同,FeCl4盐为负磁电阻,而GaCl4盐为正磁电阻.我们认为这种输送现象的差异性起源于π-d相互作用.我们用EDT-DSDTFVO表示ethylenedithiodiselenadithiafulvalenothioquinone-1,3-dithiole methide.     

菁染料光敏化超氧自由基的产生

本文用自旋捕捉技术研究了青染料在含氧的二甲基亚用溶液中将氧光还原成超氧自由基的反应,在水溶液中光照时产生的羟基自由基来源于是初形成的O₂^·。超氧负离子的形成是由于电子从激发态染料转移至溶解的氧,各种染料的光致ESR信号强度与染料的氧化还原电位有关。     

酰胺化合物于金属修饰的TiO2粒子表面的光催化分解

用ESR方法研究了5种脂肪酰胺化合物在经金属银修饰后的二氧化钛微粒表面光诱导电子转移和有关光催化反应行为。结果发现经修饰过的与未修饰过的TiO₂粒子的光催化特性有极为明显的差别。当体系中无TiO₂存在时,只是甲酰胺有很微弱的反应,加合物(DMPO-CONH₂)·的信号被检出,而其它4种酰胺均无ESR信号。除碳中心自由基外,还有(DMPO-OH)·信号被检出,相同条件下,采用Ag-TiO₂时ESK信号明显增强,银用量为10%时比1%的更强。因此半导体TiO₂粒子表面进行银修饰后可显著提高光催化能力。     

First-Principles Based Model of Spin-state Phase Transition

The nature of spin-state phase transition is investigated with [Fe（C4H4N2）（Pt（CN）4}] that is＂ a novel 3D Hofmann-like compound. The bistability of this system is obtained by the first-principles calculation. It is demonstrated that thermal expansion is the intrinsic force involved in spin-state transition. Based on these results, we suggest a thermal exciting bistable model of spin-state transition with a temperature dependent crystal-field splitting （CFS）. Experimental evidence of spin-state phase transition coincides with our theoretical model. This model approaches something fundamental in the mechanism leading to the transition, and it is important in developing new and practical controllable quantum devices.     

星型低聚物线性和非线性光学性质

利用稳态吸收和发射光谱、瞬态吸收光谱、双光子荧光和z扫描技术,系统地研究了一系列星型芴乙烯撑三聚茚低聚物(Tr-OFV_n,n=1～4)的光物理性质. 结果显示,芴乙烯撑单元的增加会导致吸收光谱和荧光谱的带边发生红移,同时也缩短了激发态物种的寿命. 伴随着π共轭长度的增加,三聚茚低聚物的双光子荧光效率和双光子吸收截面也逐渐增强. 基于态求和方法数值模拟了材料的双光子吸收截面,同实验值吻合较好.     

旋涂法制备KDP晶体减反膜

对KDP晶体旋转涂膜过程中的技术问题进行了探讨,包括元件夹持安全性、膜层均匀性、膜层透射比、膜层疏水性能、膜层激光损伤阈值等。分析了晶体元件加速旋转阶段的受力情况,明确了KDP晶体元件在旋涂操作过程中受力状态的安全性。对不同溶剂体系的膜层均匀性进行了判断,在400 mm尺寸的元件上获得了透射比均匀性为0.3%的减反膜。对溶胶进行稳态剪切流变分析得知,在现有的涂膜转速 (对应剪切速率100~200 s-1)范围内,其粘度随着剪切速率的增加几乎不变,近似牛顿流体。在旋涂过程中,处于基底不同位置的溶胶的粘度大致相等,这是影响膜层均匀性的重要原因之一。膜层疏水性能较好,水接触角测试结果大于152。在SiO2基底上制备的减反膜,1053 nm处透射比大于99.8%。在熔石英基片上制备的三倍频减反膜样品的功能性激光损伤阈值约为10 J/cm2（355 nm, 3 ns）。