垂直腔面发射激光器中顶层相位对模式特性的影响

研究了垂直腔面发射激光器中不同的顶层厚度对激光器模式特性的影响。结果表明空气界面反射与分布布拉格反射器（ＤＢＲ）的反射率反相时,将导致阈值增益增加几倍,而且模式光场强度在出射端面有反常的增强,但对光场进入分布布拉格反射器的等效厚度影响不大。精确腐蚀顶层厚度可供替调节分布布拉格反射器周期数,以改善器件特性。     

光纤光栅法布里-珀罗腔透射特性的理论研究

推导了光纤光栅法布里－珀罗腔强度透射率的解析表达式,理论上研究了这种腔的透射特性,并同普通法布里－珀罗腔做了比较;讨论了光纤光栅法布里 罗腔单模输出阈值腔长与光纤光栅长度和反射率之间的关系。     

用阈值表达式研究长外腔半导体激光器的双稳特征

利用外腔半导体激光器（ＥＣＬＤ）在不同频率振荡所需的阈值载流子密度的表达式及相关的折射率表达式他它的双稳特性,由此导出了在外腔半导体激光器的ｐ－ｖ（功率－频率）曲线上出现双稳的条件以及双稳环宽度的解析表达式。     

On the Extrapolation of Perturbation Series

We discuss certain special cases of algebraic approximants that are given as zeroes of so-called effective characteristic polynomials and their generalization to a multiseries setting. These approximants are useful for the convergence acceleration or summation of quantum mechanical perturbation series. Examples are given and some properties discussed.     

混合谐振模式宽带长波红外超表面吸收器研究

为了满足红外探测器件集成化和对红外宽光谱范围吸收的需求,设计了一种工作在长波红外波段(8~14μm)的超宽带、高吸收、极化不敏感的超材料吸收器。通过在金属-介质-金属三层异质的超材料吸收器结构的顶部金属周围镶嵌一层介质形成超表面,以增加谐振强度和吸收带宽。在8~13.6μm的带宽范围内,该结构有超过90%的平均吸收率,覆盖了大部分长波红外大气窗口波段,对红外探测领域有着重要意义。研究结果表明:镶嵌的金属-介质组成的介质波导模式和谐振腔模式的结合以及传播型表面等离激元模式的激发是形成宽带高吸收的主要原因,并且谐振模式的谐振波长可以通过相关参数来进行调控。本文的研究结果为可调谐宽带长波红外吸收材料的设计提供参考,该设计方法可推广到中波红外波段、甚至长波红外或其它波段。     

4MV/80kA IVA型脉冲X射线照相装置研制进展

介绍了西北核技术研究院研制的4 MV脉冲X射线闪光照相装置("剑光二号")系统组成和实验结果。装置基于感应电压叠加器(IVA)驱动阳极杆箍缩二极管(RPD)技术,主要由前级脉冲功率源、感应电压叠加器和RPD等组成。前级脉冲功率源由两台3.2 MV低电感Marx发生器和四路同轴水介质线组成。每台Marx同时给两路脉冲形成线(特征阻抗6Ω、电气长度30 ns)充电,充电峰值时间约370 ns。每路水介质线采用两级脉冲压缩,为感应腔馈入约1 MV/160 kA/60 ns电脉冲。电触发SF6气体开关、自击穿水开关分别用作主同步开关和脉冲陡化开关。感应电压叠加器采用四级1.5 MV感应腔串联,每级感应腔采用单点馈入结构。次级采用真空绝缘传输线实现电压叠加和功率传输,特征阻抗由30Ω线性增大至120Ω。采用4 MV电压下综合性能较优的RPD来产生强脉冲X射线。装置目前达到技术指标:输出电压4.3 MV、脉冲前沿(10%~90%)21 ns、半高宽约70 ns、二极管电流85 kA,X射线半高宽约55 ns,整机延时(从Marx触发器输出到X射线产生)约749 ns,标准偏差约7 ns。当RPD阳极采用直径2 mm钨针时,正前方1 m处剂量约15.5 rad(LiF),正向焦斑约1.4 mm。     

Lewis Acid Accelerated Aryl Ether Bond Cleavage with Nickel: Orders of Magnitude Rate Enhancement Using AlMe3

Study of the kinetics of intramolecular aryl ether C?O bond cleavage by Ni was facilitated by access to a family of metal complexes supported by diphosphines with pendant aryl‐methyl ethers. The nature of the aryl substituents was found to have little effect on the rate of cleavage. In contrast, soluble Lewis acidic additives accelerate the aryl ether cleavage dramatically. The effect of AlMe ₃ was studied in detail, and showed an increase in rate by several orders of magnitude. Low temperature NMR spectroscopy studies demonstrate quantitative coordination of ether to Al. From the Lewis acid‐bound precursor, the activation parameters for ether cleavage are significantly lower. These findings provide a mechanistic basis for milder catalyst design for the activation of strong bonds.     

Fast solvers for unsteady thermal fluid structure interaction

We consider time‐dependent thermal fluid structure interaction. The respective models are the compressible Navier–Stokes equations and the nonlinear heat equation. A partitioned coupling approach via a Dirichlet–Neumann method and a fixed point iteration is employed. As a reference solver, a previously developed efficient time‐adaptive higher‐order time integration scheme is used. To improve on this, we work on reducing the number of fixed point coupling iterations. Using the idea of extrapolation based on data given from the time integration by deriving such methods for SDIRK2, it is possible to reduce the number of fixed point iterations further by up to a factor of two with linear extrapolation performing better than quadratic. This leads to schemes that can use less than two iterations per time step. Furthermore, widely used vector extrapolation methods for convergence acceleration of the fixed point iteration are tested, namely Aitken relaxation, minimal polynomial extrapolation and reduced rank extrapolation. These have no beneficial effects. Copyright © 2015 John Wiley & Sons, Ltd.     

带电粒子加速器的基本类型及其技术实现

现代粒子加速器的发展已有100年的历史。给出了粒子加速器主要类型的简单分类图表,从粒子加速器发展过程中相关概念演变和加速器技术逻辑发展的角度,概述了粒子加速器的基本类型、基本工作原理、相应的技术实现途径以及各类加速器的典型的技术特征。