光纤腔耦合碳化硅薄膜的理论计算

半导体材料中的自旋色心是量子信息处理的理想载体,引起了人们的广泛兴趣.近几年,研究发现碳化硅材料中的双空位、硅空位等色心具有与金刚石中的氮-空位色心相似的性质,而且其荧光处于更有利于光纤传输的红外波段.然而受限于这类色心的荧光强度和谱线宽度,它们在量子密钥分发和量子网络构建等方面的实际应用依然面临严峻的挑战.利用光学腔耦合自旋色心实现荧光增强和滤波将能有效地解决这些难题.将光纤端面作为腔镜,并与自旋色心耦合可以实现小模式体积的腔耦合,而且天然地避免了需要再次将荧光耦合进光纤而造成损耗的缺点.本文理论计算了耦合碳化硅薄膜的光纤腔的性质和特征.首先通过优化各项参数包括薄膜表面粗糙度、腔镜反射率等,理论分析了存在于光纤腔中的不同模式的特点,以及光纤腔耦合色心的增强效果及相关影响因素.进一步地研究了对开放腔而言最主要的影响因素—振动对腔性质、色心的增强效果以及耦出效率的影响,最终得到在不同振动下的最大增强效果以及对应的耦出透射率.这些结果为今后光纤腔耦合色心的实验设计提供了最直接的理论指导,为实验的发展和优化指明了方向.     

Atomic structure and collision dynamics with highly charged ions

The research progresses on the investigations of atomic structure and collision dynamics with highly charged ions based on the heavy ion storage rings and electron ion beam traps in recent 20 years are reviewed. The structure part covers test of quantum electrodynamics and electron correlation in strong Coulomb field studied through dielectronic recombination spectroscopy and VUV/x-ray spectroscopy. The collision dynamics part includes charge exchange dynamics in ion-atom collisions mainly in Bohr velocity region, ion-induced fragmentation mechanisms of molecules, hydrogen-bound and van de Waals bound clusters, interference, and phase information observed in ion-atom/molecule collisions. With this achievements, two aspects of theoretical studies related to low energy and relativistic energy collisions are presented. The applications of data relevant to key atomic processes like dielectronic recombination and charge exchanges involving highly charged ions are discussed. At the end of this review, some future prospects of research related to highly charged ions are proposed.     

Riemann面上多极点亚纯向量场的代数及其在亚纯λ-微分的实现(Ⅰ)

本文给出球面上亚纯向量场代数的明显构造,并给出这一代数的中心扩充。研究了作为这一代数的实现球面上亚纯λ-微分的性质。     

Pb-Mg-Al合金腐蚀机理的电子理论研究

为了了解Pb-Mg-Al合金腐蚀的物理本质, 本文采用基于第一性原理的赝势平面波方法系统地计算了Pb-Mg-Al合金中各物相的结合能、费米能级和局域态密度等电子结构参数, 分析了合金的电化学腐蚀机理. 计算结果表明：Pb-Mg-Al合金中各主要组成物相稳定性大小关系为 Mg₁₇Al₁₂>Mg₂Pb>Mg;Mg,Mg₂Pb和Mg₁₇Al₁₂的费米能级存在E_f(Mg)>E_f(Mg₂Pb)>E_f(Mg₁₇Al₁₂)的关系, 说明Mg最容易失去电子, Mg₂Pb次之, Mg₁₇Al₁₂最难;局域态密度表明, 在同样的外界条件下, 体系中Mg相和Mg₂Pb相对于Mg₁₇Al₁₂均处于不稳定的状态, 容易失去电子, 即容易发生腐蚀. Pb-Mg-Al合金体系中不同物相的费米能级差构成了电化学腐蚀的电动势, 导致电子从费米能级高的Mg相和Mg₂Pb相流向费米能级低的Mg₁₇Al₁₂相, 使Pb-Mg-Al合金发生腐蚀.     

THE DISENTANGLED-STATE IN THE TWO-PHOTON JAYNES-CUMMING MODEL WITH A KERR-LIKE MEDIUM

The pure state dynamical evolution of the atomic as well as the field states in the two-photon Jaynes Cumming model with a Kerr-like medium for the field initially in the coherent state is investigated under the high-field approximation (\bar{n}＞＞1). Analytic expressions of the disentanglement conditions and the relevant disentangled states are derived, which are closely related to Kerr nonlinear coupling constant. This study also reveals that the initial atomic excited state can be evolved into the atomic dipole squeezed state.     

高速流场对光传输特性的影响

利用一座小型跨超声速风洞进行了高速流场光传输特性试验研究。光束在高速流场中传输时,由于流场密度变化,光波波前会发生畸变。利用风洞提供0.7,2.0和3.0等气流马赫数的流场条件,采用基于夏克-哈特曼波前传感器的光学测量系统,对光束在风洞流场中传输时的波前畸变进行了测量。试验结果表明:随着风洞流场马赫数增加,流场对光波传播的影响增大,光波波前畸变量显著提高。因此,在利用风洞进行气动光学试验研究之前,有必要消除风洞流场本身对光波传输的严重干扰。     

Internal cancellation of spikes using two avalanche photodiodes in series for single photon detection

<正>We propose a method of improving the performance of InGaAs/InP avalanche photodiodes by using two avalanche photodiodes in series as single photon detectors for 1550-nm wavelength.In this method,the raw single photon avalanche signals are not attenuated,thus a high signal-to-noise ratio can be obtained compared with the existing results.The performance of the scheme is investigated and the ratio of the dark count rate to the detection efficiency is obtained to be 1.3×10~(-4) at 213 K.     

PbB_4O_7晶体的太赫兹光谱和软光学声子

对实验测量的PbB4O7晶体样品的太赫兹(1012Hz)光谱、拉曼光谱以及红外—可见—紫外光谱进行了分析.在0.25—2.5THz波段介电函数随频率变化曲线ε(ν)出现共振型尖峰.四方面的分析表明PbB4O7晶体中存在软光学声子:1)介电函数随频率的变化曲线ε(ν)满足LST(Lyddane-Sachs-Teller)关系;2)在共振峰的频率附近(3.10THz)有很强的拉曼散射峰;3)吸收系数随频率的变化曲线α(ν)满足极化激元的特征;4)透过晶体的光子的色散关系ν(k)发生断开的畸变.PbB4O7晶体中存在软光学声子的意义在于,在满足产生极化激元的条件下,透过晶体的光子的频率会发生劈裂,分为升高和降低的两支,有可能利用这种原理来改变光子的频率.     

A Light-Cone QCD Inspired Effective Hamiltonian Model with SU（3） Flavor Mixing

The effective light-cone Harniltonian is extended to include the SU（3） flavor mixing interaction besides the confining potential. Solving the coupled J = 0 mass eigen equations for the up, down, and strange quark components numerically, the masses of π^0 and η, their radial wave functions, and rms radii are obtained in agreement with the experimental data.     

运用RBF径向基神经网络识别基于小波变换的淫羊藿苷红外光谱指纹特征

运用RBF径向基神经网络对基于傅里叶变换红外光谱（FTIR）法、相关系数比对法及多层次小波变换所提取的淫羊藿药材样本有效成分指纹特征进行识别。样品包括药典选用的５个物种（淫羊藿Epimedium brevicornu Maxim.、箭叶淫羊藿E.sagittatum（Sieb. et Zucc.） Maxim.、柔毛淫羊藿E.pubescens Maxim.、朝鲜淫羊藿E.koreanum Nakai和巫山淫羊藿E.wushanense T.S.Ying）和其他物种共计250个样本。淫羊藿指标成分淫羊藿苷在原药材和甲醇提取物的红外光谱图上,具有较明显的1 259 cm-1特征峰,经典的HPLC法的定量分析结果也佐证了淫羊藿苷的含量与1 259 cm-1峰的位置具有很好的一致性。为此该峰可以用来作为判别各物种淫羊藿药材是否含有淫羊藿苷的重要依据。在此基础上,采用相关系数比对法和多层次的小波变换法消除了因淫羊藿苷含量低、吸收峰弱,信号和噪声大的问题,增强了RBF径向基神经网络的识别效果。初步建立了基于小波变换和RBF径向基神经网络淫羊藿原药材红外光谱快速识别淫羊藿苷指标成分的一种新方法。