电子俘获材料CaS∶Eu,Sm光谱特性研究

研究了电子俘获材料CaS∶Eu,Sm多晶粉末的紫外-可见-红外吸收光谱及红外激励光谱.研究结果表明,CaS∶Eu,Sm中主激活剂Eu和辅助激活剂Sm分别以Eu2 离子和Sm3 离子的形式存在;ETM的吸收差谱及红外激励光谱所反映的光谱特性是不同的.紫外-可见光区的吸收差谱给出了ETM光谱存储灵敏度的信息,而红外光谱区的吸收差谱给出了ETM所俘获电子数量的信息及电子陷阱能级的特征(深度和宽度)信息.红外激励光谱则反映了ETM将不同波长的红外激励光的能量转换为特定波长处的红外辐射光能量的光谱转换灵敏度.二者结合起来可以更完整地描述ETM的光谱特性.     

Semiconductor-Optical-Amplifier-Based Inverted and Non-Inverted Wavelength Conversion at 40 Gb/s Using a Detuning Optical Bandpass Filter

We experimentally demonstrate 40Gb/s semiconductor-optical-amplifier-based tunable wavelength conversion （WC） using a detuning optical bandpass filter. Both inverted and non-inverted WCs are obtained by shifting the filter central wavelength with respect to the probe wavelength. When the filter is red shifted by 0.4nm or blue shifted by 0.3nm, the WC is non-inverted. However, when the filter is blue shifted by 0.1 nm, the WC is inverted. It is experimentally demonstrated that the WC has a tunable range covering the C-band.     

Optimization of Metamorphic InGaAs Quantum Wells on GaAs Grown by Molecular Beam Epitaxy

We investigate the molecular beam epitaxy growth of metamorphic InxGal-xAs materials （x up to 0.5） on GaAs substrates systematically. Optimization of structure design and growth parameters is aimed at obtaining smooth surface and high optical qualdty. The optimized structures have an average surface roughness of 0.9-1.8 nm. It is also proven by PL measurements that the optical properties of high indium content （55%） InGaAs quantum wells are improved apparently by defect reduction technique and by introducing Sb as a surfactant. These provide us new ways for growing device quality metamorphic structures on GaAs substrates with long-wavelength emissions.     

Effects of Different Dispersion Methods on the Microscopical Morphology of TiO2 Film

Nanocrystalline porous TiO2 films were prepared on conducting glass supports （ITO） by processed commercial TiO2 nanometre powder （P25）. Three methods of physical dispersing for TiO2 powder, i.e. grinding, magnetic stirring, sonicleaning, were used to disperse TiO2 nanometre powder. Surface morphologies of TiO2 films were observed by optic-microscope and SEM. It is found that the surface morphologies of TiO2 films are determined not only by the dispersing methods but also by the percentage of TiO2 powder in the dispersing system. Different film morphologies can be obtained under the same preparation condition but with different dispersing methods. A lot of cracks exist on the film surface for which the TiO2 slurry is dispersed by grinding. Magnetic stirring leads to some white points and micro-holes on the film surface. Only a few of micro-holes can be observed on the film surface, in which the TiO2 slurry is dispersed by sonicleaning. Different surface morphologies can also be found with different thicknesses of TiO2 films. Different film thicknesses are due to different percentages of TiO2 powder in the slurry. The related mechanism leading to different features of the surface morphologies for the TiO2 films is discussed.     

杂质对多电子方形量子点系统基态能的影响

根据密度泛函理论,用自洽迭代的方法求解二维方形量子点中有杂质时电子(N=1~12)的薛定谔方程,对绝对零度情况下处于基态电子的总能量进行了数值计算,并讨论了杂质对量子点中电子基态能量的影响,得出了方形量子点中多电子系统基态的一些性质.     

甲硅烷的分解复合的对称性

本文基于原子分子反应静力学证明甲硅烷SiH4的分解方式Ⅱ是对称性允许的,而分解方Ⅰ是对称性不许可的.     

First-Principles Study of Electronic Properties in PbS（1^-00） with Vacancy Defect

Electronic properties of both Pb and S vacancy defects in PbS（1^-00） have been studied using the first-principles density functional theory （DFT） calculations with the plane-wave pseudopotentials. It is found that the density of states （DOS） near the top of the valence band and the bottom of the conduction band is significantly modified by these defects. Our calculation indicates that in the case of S vacancy defects the Fermi energy shifts to the conduction band making it as an n-type PbS （donor）. However, in the case of Pb vacancy, because of the appreciable change of the DOS, the system acts as a p-type PbS （accepter）. In addition, the structural relaxation shows that the defect leads to outward relaxation of the nearest-neighbouring atoms and inward relaxation of the next-nearest neighbouring atoms.     

B0d→φK*0极化反常和Bd→φKs CP不对称的研究

在模型Ⅲ下,仅考虑来自于中性规范玻色子H0,H0和A0产生的树图阶味改变中性流的贡献,并利用QCD因子化方法,对B0d→φK(≠)0衰变过程的极化反常和Bd→φKs衰变过程的CP不对称进行了研究,经过计算发现,在147＜|λbsλss|＜165的参数范围内,这两个过程中存在的反常现象能够同时给予解释.     

应用具有手征流关联函数的光锥求和规则计算B(Bc)→Dlν过程的形状因子

在QCD光锥求和规则(LCSR)框架内应用具有手征流关联函数计算B(B_c)→Dlν衰变过程的弱形状因子. 所获得的形状因子的表达式仅依赖于D介子的主导级分布振幅(DA). 应用了三类D介子的分布振幅计算了形状因子F_B→D(0)和F_Bc→D(0). 在速度迁移1.142=0附近算符乘积展开(OPE)得以有效的情况下所计算的形状因子行为在误差范围内与B(B_c)→Dlν过程实验数据相一致. 在大反冲区域1.35B→D(0)是与微扰QCD(pQCD)结果相一致的. 所以本文的计算在联接格点QCD, 重夸克对称性和pQCD之间起桥梁作用，有助于进一步对B(B_c)→Dlν跃迁过程的理解. 计算 使用了在端点具有指数压低的分布振幅行为, 对F_Bc→D(0)的预言与其他方法获得的结果是可比的, 有利于具有库仑修正的三点求和规则(3PSR)方法所得的结果.     

大能量钕玻璃棒状激光器新型热管理技术

 针对kJ级大能量钕玻璃固体脉冲激光器，对比研究了传统恒温水冷方式和采用加热控制的新型热管理技术下的激光棒温度分布情况。结果表明，采用新型热管理技术可大大降低棒内温度梯度，减小泵浦过程中的热效应，确保大能量激光输出；而且加热循环水的最佳升温值在单泵浦脉冲引起的激光棒平均温升值附近，使得径向温差最小，该最佳升温值与脉冲间隔时间有关,比如脉冲间隔15 s时，循环水在每个脉冲过后的最佳升温值为单泵浦脉冲引起的激光棒平均温升值的0.85倍；采用加热控制后水温和激光棒温度整体升高，因此在工作一个脉冲串后，必须恢复激光棒温度到初始状态，然后再进行下一个脉冲串工作。