基于衍射对称性的多程光路腔镜准直算法

腔镜准直是多程放大光路准直中的基础,针对高功率固体激光装置多束组并行准直对腔镜准直的要求,提出一套基于衍射对称性的腔镜准直算法,可以避免腔镜准直受到图像质量的影响而导致精度偏低。在神光Ⅲ主机装置上进行了该腔镜准直算法的实验验证,实验结果表明,相对于传统算法,采用基于衍射对称性的腔镜准直算法,可以将腔镜准直精度由8μrad提升至3.96μrad。     

光纤技术在光路自动准直中的应用

光路自动准直系统用于惯性约束聚变的高功率激光装置的光束精密自动准直调整.针对神光Ⅲ原型装置四程放大光路对自动准直系统的调整时间和调整精度的要求,考虑到光路总体结构的要求,利用光纤像传递和光纤耦合技术,结合近场远场像传递原理,使用插入式光纤点光源实现了后腔镜的准直调整,充分考虑了四程放大的光路像传递特点,设计出一套优化合理的四程放大准直方案,并且在神光Ⅲ原型装置模拟实验平台上得到了充分的验证和考核.实验结果表明光路自动准直系统能够在15 min之内顺利完成系统的光路调整,光束近场调整精度优于近场光斑的±0.5%,光束远场调整精度≤±0.3",满足了原型装置总体的要求.     

大型激光系统光路的自动准直

提出利用伺服控制系统调整大型激光系统的光束的思想,由此编排的计算机程序能使激光系统光路自动准直,准直精度达到预期要求.     

基于叉丝阵列的准分子激光MOPA系统多路光束自动准直

为了实现激光在放大器多程放大及靶面高指向精度,介绍了高效准分子激光系统多路光束自动准直技术的研究工作。提出利用双叉丝阵列像传递光路,分别在输入光路和输出光路上设置叉丝阵列作为近远场基准,解决了光路中无天然准直基准及多路并行准直等问题。搭建了预放大器II的三路双程激光自动准直系统,验证了该方法的可行性,并利用成像系统和反馈控制结构实现了自动准直系统的联调实验。     

一种高精度激光光路自动准直系统的实现

对高精度激光光路自动准直系统,提出了一种更加精准的四象限探测器的信号处理算法,采用四象限硅光电二极管代替传统的CCD探测光线指向,运用DSP技术处理探测信号,控制惯性压电陶瓷电动调节架快速自动准直,精度可达1μrad.该系统很好地解决了传统的CCD探测光线方法中的处理速度慢、校正精度低、占用资源大的问题.飞秒激光实验应用证明,系统能够实现激光光路的快速自动准直.     

高功率准分子激光MOPA系统中的三路激光准直技术研究

光束自动准直是大型激光装置中的重要组成部分。以准分子(XeCl)激光主振荡功率放大(MOPA)系统中一个典型的像传递单元为例,着重介绍了准直基准的建立、3路激光自动准直的原理、电荷耦合元件(CCD)图像采集与分析处理。通过实验验证,该准直单元准直效率高,准直精度能够满足MPOA系统的光束准直要求。     

光路自动准直中腔镜及反射镜控制算法

激光装置光路准直系统通过多块腔镜及反射镜的角度调整,使光路的指向和位置达到物理指标要求。为提高远近场光路准直的效率,减少电机调整次数,提出一套准直算法,腔镜准直使用正圆调整算法,反射镜准直将关联系数矩阵由传统的2维改进为4维。通过准直光学实验平台,验证了该算法收敛速度快,电机调整步数更精确,移动次数更少,小于3次就满足准直精密度要求。     

利用Pro/E族表进行靶区光路参数化设计的方法介绍

惯性约束聚变(ICF)物理实验要求大型激光装置靶区光路按照一定角度对称入射靶的两端,利用Pro/E族表对相同特征的光束进行参数化设计,实现了靶区等光程光路排布,满足了物理实验要求.     

基于机器视觉的激光焊接焊缝智能检测研究

为了优化激光焊接质量,设计了基于机器视觉的激光焊接焊缝智能检测方法。首先利用机器视觉技术设计扫描成像单元,在获得基础的激光焊接焊缝图像后,对图像实施离焦误差校正处理。然后在补偿图像缺陷的基础上,对激光焊接焊缝图像作放大处理,设计扩束准直光路与动态聚焦光路识别焊缝特征信息,从而完成对焊缝的智能检测。实验结果表明：该方法可以能够获得更有效的焊缝信息,有利于提高激光焊接质量。     

基于同轴照明和光栅取样的激光束准直远场监测系统

利用高功率激光装置空间滤波器小孔成像和取样光栅的衍射,结合插入的负透镜发散激光来同轴照明小孔,设计出一套新型光路远场监测方案.该方案利用光栅衍射可以灵活取样激光远场,并且在实验平台上进行了实验验证.实验结果表明,其远场监测系统的准直精度达到小孔直径的1.42%,能够满足准直系统远场调整精度(小于小孔直径5%)的要求.     

基于时域调制反射阵列的波束赋形技术

传统的反射阵利用相控器件与微带线实现波束赋形。为了降低相控成本与系统复杂度,提出基于时域调制阵列波束赋形技术。时域调制反射阵列是一种基于简单可重构反射单元的反射阵,它利用控制可重构反射单元的开与关,达到控制阵列输出,实现旁瓣抑制、波束赋形等功能。通过理论推导及仿真,结果表明,时域调制反射阵可以在不采用传统阵列中的相控器件及馈电网络的前提下,采用最小方差无失真响应波束赋形方法与时间调制法,生成理想的方向图,实现波束赋形功能。此特性将有利于推广波束赋形技术在毫米波频段反射阵的应用。     

Gallium phosphide beam lead electroluminescent devices

Beam lead GaP electroluminescent diodes have been developed using a quasi-planar configuration. This new structure couples the advantages of beam lead technology to the high-efficiency GaP p-n junctions prepared by liquid phase epitaxial (LPE) growth. The devices consist of a p-type (Zn, O-doped) LPE mesa formed on an n-type (Te-doped) LPE layer grown on an n-type Czochralski-grown substrate. A deposited insulator film covers the entire mesa surface and passivates the exposed junction perimeter. Ohmic contacts are made to both the p- and n-regions through holes in the insulating layer and beam leads are applied by conventional technology. The finished devices are shaped into domed structures during the final separation of the wafer into individual devices. Complete devices bonded to substrates were operated at 10 mA with typical forward voltages of 1.95 ± 0.05 V with external quantum efficiencies of 2-2.25 per cent (unencapsulated). This beam lead quasi-planar structure takes advantage of the inherently large size of the individual devices dictated by optical considerations and allows a number of improvements in device design. The areas where advantages over existing GaP diodes can be realized are as follows, 1) Optimization of external efficiency by contact design and diode configuration is possible. 2) Planar beam lead processing and junction passivation methods can be used, 3) Array fabrication in discrete or monolithic forms is feasible.     

Optoelectronic materials and devices

The development of epitaxial growth techniques, such as molecular beam epitaxy and metal-organic vapour phase epitaxy, allows us to control the growth of individual semiconductor layers on an atomic scale. These achievements provide a strong basis for fabricating new forms of active device with ‘tailor made’ characteristics. Novel electronic devices have been proposed and demonstrated in various fields. These include HBTs, HEMTs and RTDs. As well as these devices there has been enormous development in photonic and optoelectronic devices.     

高功率激光系统数字在线操控关键技术研究

在惯性约束聚变(ICF)精确打靶中,对激光束变换、整形和控制要求苛刻,通过数字在线操控技术能够在线实现激光系统的自动校准。对数字在线操控的关键技术如非线性宽带传输、宽带放大和频率转换等模型及其算法进行详细分析。同时还对激光系统中不可或缺的辅助性技术开展了研究,具体包括基于傍轴光线追迹方程(PRTE)的光线追迹、光场的矢量衍射传输、基于迭代算法的相位恢复、光栅分析以及微纳米器件的时域有限差分(FDTD)分析等。在建模及算法分析过程中,给出了相应的模拟计算结果,并用来验证理论的正确性和算法的稳定性。     

MEM's the word for optical beam manipulation

The best way to switch the direction of an optical beam is simply to rotate a mirror, focus an optical beam by mechanically translating a lens, or extinguish an unwanted optical beam by physically blocking its path. Recent, independent developments in microelectromechanical (MEM) devices promise to remedy the issue of high cost and unreliability associated with the “moving parts” needed for these optical functions. This article describes some aspects of these recent developments undertaken in the “microphotonics” group at U.C. Berkeley on building MEM-based optical systems on a silicon chip     

大气激光通信中一种新的光束自动捕获方法

提出了一种适合大气激光通信特点的光束自动捕获系统,详细分析了光束自动捕获系统的工作原理。该方法可以省去专门的光束捕获系统,以角反射器等光学元件作为光束检测器件,用位置检测器件检测光束的偏离程度,对发射/接收系统进行自动调整。这种方法比较简单而切实可行。     

电子束直写技术制作GHz频带声表面波器件

电子束具有刻写微细图形尺寸的能力，容易实现亚微米宽格栅的声表面波器件制造，因此可达到器件的高频化和在设计上更具灵活性。该文介绍了器件图形的数据处理策略，基片的制备和工艺过程。描述了在电子束曝光过程中采取的一些独特方法，生产了性能良好的吉赫兹频带滤波器、谐振器和延迟线等声表面波器件。     

Electron pulse generation at 64 GHz in scanning electron microscope

An electron beam chopping technique has been developed which enables the generation of electron pulses at tens of GHz in an SEM. This is effected by deflecting the beam in a circle and chopping it with a multislot aperture. Electron pulses have been produced at 64 GHz and measured, and a waveform measurement at 18 GHz demonstrates its potential application to electron beam characterisation of very high speed devices and MMICs.<>     

The limits of high-speed e-beam testing

The development of new types of very high-speed integrated circuits, such as those based on GaAs, makes extremely high demands on electron beam measuring technology. The limits of this measurement method for the time, voltage and spatial resolution were theoretically investigated. It is found that these parameters are mutually dependent on each other and that improvements in the time resolution can be made only at the expense of the voltage or spatial resolution. The theory allows specific optimization of the electron beam measuring devices inclusive of their electron-optical properties. An experimental system was realized for high speed measurements on GaAs devices. Electron pulse widths of 15 ps were experimentally attained with measuring probes of 0.5 μm diameter and an effective noise voltage of 30 mV. This device was used to investigate various components in the GHz range.     

Compact, High-Power Electron Beam Based Terahertz Sources

Although terahertz (THz) radiation was first observed about 100 years ago, this portion of the electromagnetic spectrum at the boundary between the microwaves and the infrared has been, for a long time, rather poorly explored. This situation changed with the rapid development of coherent THz sources such as solid-state oscillators, quantum cascade lasers, optically pumped solid-state devices, and novel coherent radiator devices. These in turn have stimulated a wide variety of applications from material science to telecommunications, from biology to biomedicine. Recently, there have been two related compact coherent radiation devices invented able to produce up to megawatts of peak THz power by inducing a ballistic bunching effect on the electron beam, forcing the beam to radiate coherently. An introduction to the two systems and the corresponding output photon beam characteristics will be provided.