Forbidden transition properties of fine-structure 2p~3 ~4S_(3/2)–2p~3 ~2D_(3/2,5/2) for nitrogen-like ions

Based on relativistic wave functions from multiconfiguration Dirac–Hartree–Fock and configuration interaction calculations, E2 and M1 transition probabilities of 2p~3 ~4S_(3/2)–2 p~3 ~2D_(3/2,5/2) are investigated in the nitrogen-like sequence with7 ≤ Z ≤ 16. The contributions of the electron correlations, Breit interaction, and the quantum electrodynamic(QED) effects on the transition properties are analyzed. The present results can be used for diagnosing plasma. In addition, several N-like ions can also be recommended as a promising candidate for a highly charged ion(HCI) clock with a quality factor(Q) of transition as high as 10~(20).     

利用椭圆高斯光束产生266nm紫外连续激光

本文采用商用532 nm激光器作为基频光源,利用偏硼酸钡(β-BBO)晶体进行外腔倍频,实现了266 nm连续激光的高效输出.文中详细模拟了BBO晶体中的束腰形状对倍频效率的影响,仿真和实验结果均表明椭圆高斯光束可以有效改善走离效应,提高倍频转换效率.通过优化蝶形倍频腔,可以使椭圆高斯光束在腔内共振,当1 W基频光输入时可输出约180 mW的266 nm紫外连续激光,倍频转换效率达到18%.     

基于现场可编程门阵列的数字化自动锁相技术研究

基于现场可编程门阵列(FPGA)的高速数据处理能力,介绍了一种采用双比例积分微分(PID)算法的数字化伺服控制系统,在一定程度上改善了数字化锁相中锁定精度与控制范围之间的矛盾,大大提高了单次锁定持续时间.程序采用正弦扫描和积分扫描两种方法分别实现了相位失锁自动搜索功能,并且在实验上得到了验证.前者失锁后的搜索时间更短,...     

Correction of walk-off-induced wavefront distortion for continuous-wave laser

We theoretically and experimentally investigate the wave front distortion in critically phase-matched continuous-wave (CW) second harmonic generation (SHG). Due to the walk-off effect in the nonlinear crystal, the generated second harmonic is extremely elliptical and quite non-Gaussian, which causes a very low matching and coupling efficiency in experiment. Cylindrical lenses and walk-off compensating crystals are adopted to correct distorted wave fronts, and obtain a good TEM₀₀ mode efficiently. Theoretically, we simulate the correction effect of 266-nm laser generated with SHG. The experiment results accord well with the theoretical simulation and an above 80% TEM₀₀ component is obtained for 266-nm continuous-wave laser with a 4.8°-walk-off angle in beta barium borate (BBO) crystal.     

波包入射对共振穿透现象的影响研究

共振穿透是一维量子散射中的一个重要的现象.一般教材中对该现象的阐述都是假定单色平面波入射,对于更加接近于实际情况的波包入射缺乏研究.本文利用解析推导并作图的方法,详细讨论了一维方势阱中波包散射的主要特点,以及入射波包的能量均值及展宽对共振穿透现象的影响.本文的研究内容不仅能加深对共振穿透现象的理解,而且为分析任意分段常势能函数的散射问题提供了一般方法.     

Theoretical calculations of hyperfine splitting,Zeeman shifts,and isotope shifts of 27Al+ and logical ions in Al+ clocks

Based on the multiconfiguration Dirac-Hartree-Fock (MCDHF) method, similar models are employed to simultaneously calculate the first-order and second-order Zeeman coefficients as well as the hyperfine interaction constants of the related energy levels of ²⁷Al⁺ and its logical ions ⁹Be⁺ and ²⁵Mg⁺ in the ²⁷Al⁺ optical clock. With less than 0.34% deviations from experimental values in Zeeman coefficients of ²⁷Al⁺, these calculated parameters will be of great help for better evaluation of the systematic uncertainty. We also calculate the isotope shift parameters of the related energy levels, which could extend our knowledge and understanding of nuclear properties of these ions.     

离散调制连续变量量子密钥分发的安全边界

对一种结合离散调制和反向协调,适用于长距离传输的连续变量量子密钥分发四态协议的安全性进行了严格证明.这种协议中Alice发送的态与高斯调制协议中的有一定差异,这种差异可以等价成信道衰减和额外噪声.另外,由于Alice不可能做到精确调制,这会导致其发送的相干态中含有噪声.把这种调制引起的噪声看作光源的噪声,并推导出了在光源噪声不能被窃听者所利用的条件下的安全码率的下界.为了避免实验上快速、随机的控制本地振荡光的相位,还将无开关协议和四态协议相结合,分析了其安全性.     

线型离子阱中钙离子库仑晶体结构和运动轨迹模拟

离子阱中囚禁的离子在满足库仑耦合条件下,会形成库仑晶体,其结构分布和运动轨迹由离子阱的参数和离子种类决定.本文采用分子动力学模拟软件LAMMPS和(py)LIon程序包,仿真了⁴⁰Ca⁺在线型离子阱中库仑晶体的形成过程,以及不同位置离子的微运动和宏运动轨迹.另外,本文还对混入少量同位素离子(⁴⁴Ca⁺)和氢化钙离子(CaH⁺)后的⁴⁰Ca⁺晶体结构进行了仿真,并对混入前后形成的库仑晶体结构变化进行对比和分析,期望能对离子阱实验中形成的暗离子进行识别和处理.