Fast Integrated Electro-Optical Switch and Beam Deflector Based on Nematic Liquid Crystal Waveguides

In this paper, the design, the realization, and the experimental characterization of an integrated electro-optical switch and a beam deflector, both based on planar nematic liquid crystal (NLC) waveguides, are reported.

In order to test such devices, a particular waveguide structure consisting of a three-stage device, having a thin nematic LC film as the middle stage and two glass waveguides as the other stages, has been designed and realized. The electro-optical behavior and the response time have been studied for different configurations for both TE and TM polarized light. By a proper choice of the material parameters and because of the presence of an additional constant bias voltage, we got response time in the microsecond range. The experimental results obtained are very promising in the frame of integrated electro-optical devices, even if the effect underlying the results is not yet understood and probably needs some deeper research into liquid crystal physics and surface interactions.     

Fast Integrated Electro-Optical Switch and Beam Deflector Based on Nematic Liquid Crystal Waveguides

In this paper, the design, the realization, and the experimental characterization of an integrated electro-optical switch and a beam deflector, both based on planar nematic liquid crystal (NLC) waveguides, are reported. In order to test such devices, a particular waveguide structure consisting of a three-stage device, having a thin nematic LC film as the middle stage and two glass waveguides as the other stages, has been designed and realized. The electro-optical behavior and the response time have been studied for different configurations for both TE and TM polarized light. By a proper choice of the material parameters and because of the presence of an additional constant bias voltage, we got response time in the microsecond range. The experimental results obtained are very promising in the frame of integrated electro-optical devices, even if the effect underlying the results is not yet understood and probably needs some deeper research into liquid crystal physics and surface interactions.     

弹光调制器准单色光波偏振测量与仿真

弹光调制器(Photoelastic Modulator,PEM)互差频调制的新型偏振测量方法,能够同时实现三个斯托克斯光谱偏振参数测量,克服了现有方法的无法用阵列探测器有效采集,调制频率高的缺点,保留了原有弹光调制器偏振测量的优点。文章以光学系统的准单色光的偏振特性以及常用的偏振分析方法为基础,引入了Stokes矢量来表示入射光波的偏振特性。分析了弹光调制器实现偏振测量新方法的原理,利用三个弹光调制器工作在互相差异的频率上,对偏振光进行差频调制,产生载有偏振信息的低频分量,再通过锁相放大即可得到偏振信息,并给出利用MATLAB模拟仿真实现Stokes参量复原的过程。理论分析及仿真结果证明了该方法在理论上的可行性。     

High-Speed Coplanar Waveguide Based Submount for 40 Gbit/s Electroabsorption Modulator

A high-speed submount has been designed and fabricated for 40 Gb/s electroabsorption (EA) modulators. The submount contains a coplanar waveguide (CPW) for microwave signal feeding and a Ta₂N thin-film resistor for impedance matching. The CPW transmission line is designed to ensure low microwave loss and reflection, and Ti/Cu/Ni/Au metal is adopted for electrode fabrication to guarantee good contact with the Ta₂N thin-film. The typical reflection coefficient of fabricated submount is estimated to be lower than−21 dB up to 40 GHz. As a demonstration, a high-speed EA modulator was chip-level packaged using the high-speed submount, and the measured small-signal modulation bandwidth was over 40 GHz.     

Second Harmonic Generation of Self‐Focused Cosh‐Gaussian Laser Beam in Thermal Quantum Plasma by Excitation of an Electron Plasma Wave

This paper presents a scheme for second harmonic generation (SHG) of an intense Cosh‐Gaussian (ChG) laser beam in thermal quantum plasmas. Moment theory approach in W.K.B approximation has been adopted in deriving the differential equation governing the propagation characteristics of the laser beam with distance of propagation. The effect of relativistic increase in electron mass on propagation dynamics of laser beam has been incorporated. Due to relativistic nonlinearity in the dielectric properties of the plasma, the laser beam gets self‐focused and produces density gradients in the transverse direction. The generated density gradients excite electron plasma wave (EPW) at pump frequency that interacts with the incident laser beam to produce its second harmonics. Numerical simulations have been carried out to investigate the effects of laser parameters on selffocusing of the laser beam and hence on the conversion efficiency of its second harmonics. Simulation results predict that within a specific range of decentered parameter the ChG laser beams show smaller divergence as they propagate and, thus, lead to enhanced conversion efficiency of second harmonics. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

N × N集成光开关阵列模型

报道了由2N个1 × N 多模干涉马赫-曾德尔光开关组成的N × N光开关阵列结构,分析了这种结构的开关阵列优势和局限性.用场传输矩阵方法建立了1 × N多模干涉光开关的光场传输方程.给出了光开关阵列从任一输入端输入、从任一输出端输出时阵列开关的工作条件.在上述原理及理论基础上分析了4×4光开关阵列的结构和工作条件.     

等离子体中的消融激波及其时间发展

本文研究了等离子体消融所造成的激波，找出了位于激波波前及消融波前的各流体动力学参量间的相互依赖关系，对消融激波的生成与时间发展过程进行了描述。     

Comprehensive Study of the Waveguide Polarizer Based on the Resonant Tunneling Effect

We examine the thickness of various layers in terms of the dependence of the loss of various modes in a waveguide polarizer based on the resonant tunneling effect. An improved method is proposed to obtain the optimum design of such a polarizer. Fabrication tolerances of the designed device are also discussed. The study should be very useful in the design of a waveguide polarizer and other devices, such as selective wavelength filters, based on the same principle.     

液晶电视空间光调制器对比度的研究

本文分析了影响液晶显示屏对比度的种种因素,根据偏振光在液晶中传输的性质,提出了一种有效改进液晶电视空间光调制器对比度的新方法。通过实验得到了液晶电视最佳对比度的条件,从而使原来4∶1的最佳对比度提高到19∶1。     

波导等离子体限幅器中气体的选择与触发条件计算

 为保护电子设备不受高功率微波损坏,在矩形波导中嵌入等离子体限幅器。计算了不同气体的微波击穿场强随气体压强以及微波频率的变化规律。在高气压条件下（1 333~133 320 Pa）,气体击穿场强随气压增大而增大,在计算的4种气体中Ne的击穿场强最小;低气压条件下（1.333 2~133.32 Pa）,气体击穿场强随气压增大而减小,且Xe具有最小击穿场强。高气压条件下气体的击穿场强明显高于低气压下的击穿场强。计算结果表明：当填充133.32 Pa的Xe时,限幅器能够在约30 km范围内,有效地防护10 GW级高功率微波对电子设备的损坏。     

Application of the Gyrotron FU II Submillimeter Wave Radiation Source to Plasma Scattering Measurements

Gyrotron FU II has been successfully applied as a submillimeter wave radiation source to plasma scattering measurements on the Compact Helical System (CHS) in National Institute for Fusion Science (NIFS) in Japan. The gyrotron operates in a long pulse mode (the pulse width is about 600 ms) at a frequency of about 350 GHz (the corresponding wavelength is 0.85 mm). The output power is about 110 W. The output power is transmitted along a circular waveguide system and converted to a Gaussian-like beam by a quasi-optical antenna. After that, the beam is directed onto the CHS plasma and the scattered signal is detected by a homodyne detection system. The frequency and the wave number of the scattered signal are analyzed. The results suggest that a broad band low frequency (several tens to several hundreds kHz) density fluctuation is excited in the CHS plasma only during neutral beam injection (NBI) or ion cyclotron resonance (ICR) heating.     

高准确度光纤陀螺中相位调制的控制研究

在相位调制器基础上,提出了围绕干涉型光纤陀螺的闭环控制方案.对高准确度光纤陀螺中Y波导集成光学器件的调制特性及系统测试方法进行了研究,对其应用及光路各环节配合的技术进行了探讨,对该器件在光纤陀螺系统中的特性和测试系统进行讨论.在高准确度光纤陀螺中取得明显效果.目前,工程样机的零偏稳定性已达到0.02°/h.     

一种新型SOI Mach-Zehnder干涉型电光调制器的设计

在超紧缩双曲锥形3dB多模干涉耦合器的基础上,设计了一种新的Silicon-on-insulator (SOI) Mach-Zehnder干涉型电光调制器.与传统的Y分支器相比,双曲锥形3dB耦合器的制作容差大,而长度缩短了近30%,使得整个器件的尺寸大幅减小.调制区采用横向注入的PIN结构,模拟结果表明:当外加偏压为0.86V时,器件的调制深度最大,此时注入电流为13.2mA,对应的器件功耗为11.4mW.     

Efficient Analysis of Millimeter Wave Ferrite Circulators by the GMRES Iterative Algorithm

The finite element method (FEM) combined with the perfectly matched layers (PML) is given for simulation of waveguide ferrite circulators. The generalized minimal residual (GMRES) iterative method is applied to solve such sparse large non-symmetric system of linear equations resulting from the use of edge-based finite element method. The formulation of FEM and the algorithm of GMRES method are described in detail. The reflection and insertion losses of millimeter wave waveguide circulator are analyzed and the results are compared with those obtained from literature.     

微光机电系统滤波器可调谐特性分析

分析了基于法布里-珀罗腔的微光机电系统可调谐滤波器中,空气腔厚度与峰值波长间的关系。微光机电系统中,空气腔的厚度一般在一个波长附近,因此腔的干涉级数较小,两边反射镜的反射相位对峰值波长的影响比较大。从反射相位出发,推导出了基于这种结构的可调谐滤波器中空气腔厚度和谐振波长之间的线性关系,并通过数值计算进行了验证。分析了影响滤波器调谐灵敏度的因素,构成介质反射镜的薄膜材料的高低折射值以及薄膜堆的层数都能改变线性系数的值。最后估算了一定波长范围内这种线性关系的误差。     

太赫兹波光子晶体光纤传输特性分析

利用矢量有限元法分析了太赫兹波光子晶体光纤单模截止频率和波导色散随光纤结构的变化特性．结果表明，太赫兹波光子晶体光纤的单模截止频率随着光纤空气孔占空比的变大而降低，零波导色散点频率随着空气孔占空比变大而增加，约束损耗随着空气孔的圈数增加而降低．     

用于获取大调制度的驻波型电光调制器的设计与制作

设计并制作了一种采用微波驻波电极的电光调制器,该调制器被用于光谱展宽。通过非周期极性反转方法,在１６．２５ＧＨｚ的调制频率下实现了微波驻波与光波的相位匹配,从而获得了大调制度。实验中光谱展宽达到２．５ＴＨｚ。     

150V直流开关调制器模型的计算和测试

为了德国电子同步辐射加速器(DESY)的TESLA测试设备(TTF)研制新型调制器积累一些必要的经验,设计了一种150V的直流开关长脉冲调制器模型.与TESLA测试设备上正在使用的调制器相比,这种新的方案有许多优势.本文给出了这种调制器电路的部分模拟计算结果;同时,完成了调制器模型的建立和实验测试,测试结果显示输出电压波形的平顶抖动仅为±0.53%.     

基于空间光调制器的计算全息成像特性

把基于高分辨空间光调制器(SLM)的动态计算全息波面变换系统看作一个相干光学成像系统,分析并推导了该系统的点扩展函数（PSF）,进而研究了SLM像素结构所引起的固有切趾和展宽效应. 通过计算机模拟考察了SLM填充因子和衍射距离对系统分辨率的影响,给出了满足抽样定理所要求的系统的最小衍射距离. 最后提出了一种消除SLM像素结构影响的物波频谱预处理方法. 这一研究为优化系统设计,完善波面变换系统提供了新的途径.