In-Band Pumped High Power Ho：YAG Ceramic Laser by a Tm：YLF Laser

High-power 2 μm lasers are promising candidates for a variety of applications including remote sens- ing, wind lidar, and medicine as well as mid- infrared generation via pumping of optical parametric oscillators. Due to the advantages of low quantum defects and high efficiency, resonantly pumped Ho- doped lasers have attracted great attention. Ho：YAG single crystals have also been widely studied to ob- tain cw and Q-switched laser operation in the 2 μm wavelengths range.     

Measuring Carrier-Envelope Phase of Few-Cycle Laser Pulses Using High-Order Above-Threshold Ionization Photoelectrons

We experimentally demonstrate the measurement of carrier-envelope phase of few-cycle laser pulses. We have built a stereo above-threshold ionization setup. The photoelectron energy spectra of high-order above-threshold ionization are measured in both the left and right directions in the linearly polarized laser fields. It is shown that the left-right asymmetry of the spectra is dependent on carrier-envelope phase of few-cycle laser pulses. Two asymmetry parameters from the low-energy and high-energy regions at the above-threshold ionization plateau map a phase ellipse, in which the points indicate the absolute value of carrier-envelope phase. We have calibrated the phase ellipse by comparison with the semiclassical calculation. This setup allows us to determine the value of the absolute phase of few-cycle laser pulses.     

基于氢闸流管感应叠加技术的电磁脉冲源实验

介绍了一种基于感应叠加技术的重复频率脉冲源,分析了同轴屏蔽输出结构磁场的分布。实验时,充电电源工作电压为25 kV,脉冲输出重复频率为20 Hz,2个氢闸流管器件参数相差较大,栅极触发时钟存在约5 ns延时。实验结果表明:氢闸流管触发稳定可靠,输出的脉冲前沿及稳定性仍然不受影响,输出脉冲幅值约为50 kV,证明了感应叠加技术应用于气体开关的可行性。     

缓冲层对LBO晶体上1 064 nm|532 nm二倍频增透膜的激光损伤阈值的影响

采用电子束蒸发方法在LBO晶体上制备了无缓冲层和具有不同缓冲层的1 064 nm,532 nm二倍频增透膜.利用Lambda900分光光度计和调Q脉冲激光装置对样品的光学性能和抗激光损伤性能进行了测试分析.结果表明,所有样品在1 064 nm和532 nm波长的剩余反射率都分别小于0.1％和0.2％.与无缓冲层样品相比,采用SiO2和MgF2缓冲层薄膜的激光损伤阈值分别提高了23.1％和25.8％,而Al2O3缓冲层的插入却导致薄膜的激光损伤阈值降低.通过观察薄膜的激光损伤形貌,分析破斑的深度信息和电场分布,表明LBO晶体上1 064 nm,532 nm二倍频增透膜的激光损伤破坏主要表现为膜层剥落,激光产生的热冲击应力使薄膜应力发生很大变化,超过膜层之间的结合而引起膜层之间的分离.采用SiO2或MgF2缓冲层可改进Al2O3膜层的质量,从而有利于提高薄膜的激光损伤阈值.     

中信银行：现金管理的数字思维

在互联网思维和大数据技术攻势下,银行的现金管理业务也已经形成一个生态圈。随着电子银行的蓬勃发展,它的概念和服务半径越来越大,服务渠道越来越广,商业银行现金管理业务也在不断扩展和跨界融合,逐渐真正形成向交易银行的转型。观念决定行动,“左手技术、右手产品”的战略框架,再加上掌握着交易和行为两组数据的优势,     

A new metric for rotating charged Gaussben Bonnet black holes in AdS space

In this paper, we study a new metric for slowly rotating charged Gauss-Bonnet black holes in higher-dimensional anti-de Sitter space. Taking the angular momentum parameter a up to second order, the slowly rotating charged black hole solutions are obtained by working directly in the action.     

Influence of rotational excitation and collision energy on the stereo dynamics of the reaction： N（4S）＋H2 （v = 0, j = 0, 2, 5, 10） →NH（X3∑-）＋H

The N+H₂ reaction has attracted a great deal of attention from both the experimental and the theoretical community, and most of the attention has been paid to the first excited state N(²D) atoms in collisions with hydrogen molecules and the scalar properties of the reaction. In this paper, we study the stereo dynamical properties and calculate the reaction cross sections of the N(⁴S) + H₂ (v=0, j=0, 2, 5, 10) → NH(X³Σ^-) + H using the quasi-classical trajectory (QCT) method on an accurate NH₂ potential energy surface (PES) reported by Poveda and Varandas [Poveda L A and Varandas A J C 2005 Phys. Chem. Chem. Phys. 7 2867], in a collision energy range of 25 kcal·mol^-1-140 kcal·mol^-1. Results indicate that the reactant rotational excitation and initial collision energy both have a considerable influence on the distributions of the k-j′ correlation, the k-k′-j′ correlation and k-k′ correlation. The differential cross section is found to be sensitive to collision energy.     

Experimental and numerical investigation of a Hall thruster with a chamfered channel wall

A discharge channel with a chamfered wall not only has application in the design of modern Hall thrusters, but also exists where the channel wall is eroded, and so is a common status for these units. In this paper, the laws and mechanisms that govern the effect of the chamfered wall on the performance of a Hall thruster are investigated. By applying both experimental measurement and particle-in-cell simulation, it is determined that there is a moderate chamfer angle that can further improve the optimal performance obtained with a straight channel. This is because the chamfering of the wall near the channel exit can enhance ion acceleration and effectively reduce ion recombination on the wall, which is favorable to the promotion of the thrust and efficiency. However, the chamfer angle should not be too large; otherwise, both the density of the propellant gas and the distribution of the plasma potential in the channel are influenced, which is undesirable for efficient propellant utilization and beam concentration. Therefore, it is suggested that the chamfer shape of the channel wall is an important factor that must be carefully considered in the design of Hall thrusters.     

基于虚拟仪器的高精度Z扫描实验系统设计

设计了一个表征样品非线性特性的基于虚拟仪器的z扫描实验系统。利用Labview控制数字示波器TDS3012采集两路光强信号，并结合对微位移平台的控制实现Z扫描。以Nd：YAG飞秒放大器产生的800nm的飞秒激光作为探测光，经透镜聚焦后通过薄介质样品；用数字示波器测量样品在透镜焦点附近的透射光强，经过数据处理得到样品的非线性折射率和非线性吸收系数。利用该实验系统，对标准非线性吸收样品Rhodamine 6B进行了测量，计算得到其双光子吸收截面为σ^2=6．8GM（GM：10^-50cm4s photon^-1 molecule^-1），该结果与其他文献利用不同测量方法得到的结果接近，证明该实验系统的测量结果是正确的，可满足非线性测量的精度要求。