皮秒光导开关的研制及其应用

本文介绍了研制ＧａＡｓ：Ｃｒ，ＩｎＰ：Ｆｅ光导形状的过程，实验显示了形状对光的响应特性，利用光导开关来探测皮秒光脉冲的波形，并且利用光导开关的原理研制成新型的超宽带雷达实验室模型。实验显示了它的脉冲辐射和接收波形。     

光电子技术

TNZ 94060160皮秒光导开关的研制及其应用/袁乃昌,阮成礼,林为干(电子科技大学)//电子科学学刊一1994,’16(5).一518~522 介绍了研制GaAs: Cr,InP:Fe光导开关的过程.实验显示了开关对光的响应特性,利用光导开关来探测皮秒光脉冲的波形,并且利用光导开关的原理研制成新型的超宽带雷达实验室模型.实验显示了它的脉冲辐射和接收波形.图7表l参7(文)TN204,丁N24 94060161二元光学波面变形器件的研究/包红春,部敏贤,金国藩,严瑛白(清华大学)11光学学报一1994,14(9).一习88一991基于计算全息原理设计了二元光学波面变形器件,一块二元光学器件…     

新型超宽带脉冲源

研制出ＧａＡｓ：Ｃｒ，Ｆｅｐ：Ｆｅ光导开关，利用光导开关产生高功率皮秒脉冲，实验显示了所产生的皮秒脉冲波形，此种新型超宽带脉冲为研制超宽带雷达提供新型的脉冲源。     

触发光脉冲对光电导开关响应速度的影响

实验测试了触发光脉冲对光电导开关响应速度的影响;建立了满足光导开关触发光脉冲参量的光生载流子速率方程,并模拟出光生载流子浓度随触发光脉冲、脉冲宽度的变化规律,分析了光脉冲对光电导开关响应速度的影响及引起输出电脉冲上升沿变化的原因.     

不同激光二极管能量触发下GaAs 光导开关研究

GaAs 光导开关在较高的场强下可工作于雪崩模式,为此设计了异面体结构的GaAs 光导开关以提高开关场强。 设计的开关芯片厚度为2mm,电极间隙为3mm,利用半导体激光二极管对开关进行了触发实验。当开关充电电压超过 8kV 后,开关输出脉冲幅度显著增强,输出脉冲前沿快于光脉冲,开关开始了雪崩工作模式,且随着开关电场不断增加, 开关输出电压幅值也线性增加。在不同触发能量下,开关输出电压幅值和波形基本没有改变,但在较高的触发能量和高 的偏置电场下,开关抖动较小,实验中开关获得的最小抖动约500ps。     

基于光导开关和平板线的固态脉冲功率技术

紧凑型固态化是脉冲功率技术发展的趋势,研究了基于 GaAs光导开关和陶瓷平板传输线的固态脉冲功率技术。紧凑型固态脉冲功率系统的关键部件主要包括固态陶瓷平板传输线,高功率 GaAs光导开关以及激光二极管触发系统。研究了单路 Blumlein脉冲形成线输出特性,分析了 GaAs光导开关非线性导通带来的损伤,并开展了单路 Blumlein脉冲形成线实验。结果表明：研制基于固态平板传输线、光导开关以及激光二极管触发系统的紧凑型脉冲功率具有可行性,负载上获得了超过20 kV的高压脉冲输出。     

半导体激光二极管触发GaAs光导开关

半导体激光二极管触发下砷化镓（GaAs）光导开关工作于雪崩模式,为此设计了异面体结构的GaAs 光导开关以提高开关场强.设计的开关芯片厚度为2 mm,电极间隙为3 mm,利用半导体激光二极管对开关进行触发实验.当开关充电电压超过8 kV 后,开关输出脉冲幅度显著增强,输出脉冲前沿快于光脉冲,开关开始雪崩工作模式.随着开关电场不断增加,开关输出电压幅值也线性增加,但开关输出波形没有改变.对开关抖动进行测试,其测试结果显示开关偏压对抖动影响很大,随着开关偏压增加,开关抖动减小,当开关偏压升至15 kV 时,开关获得最小抖动约500 ps.     

激光触发光导开关产生超短电磁脉冲的实验研究

本文介绍了用光导开关和微带线结构产生电脉冲的实验装置,研究了激光能量和偏置电压对光导开关输出超短电脉冲的影响和三种尺寸光导开关的特性,测得了一种低掺杂Cr:GaAs材料的载流子寿命约为1.8ns,显示了这种装置用作高速光探测器的可能性。     

利用光导开关产生瞬态电脉冲研究

介绍了利用高阻特性的GaAsI、nP:Fe材料研制光导开关的方法,并得出光导开关在产生低功率皮秒电脉冲、高功率纳秒电脉冲及产生电脉冲的稳定性与输入、输出电压比等性能参数测试的实验结果。最后,介绍了光导开关处于线性与非线性临界状态下的几个重要实验新现象。     

雪崩模式下的体结构GaAs光导开关

利用能量较低的脉冲激光二极管,在较高场强下触发GaAs光导开关,使其工作于雪崩模式,从而产生纳秒上升前沿的快脉冲电压。GaAs光导开关采用垂直体结构设计,芯片厚度为2 mm,电极形状分别为圆环和圆面,触发光脉冲从圆环穿过。快脉冲产生由同轴Blumlein脉冲形成线完成。对基于GaAs光导开关的同轴Blumlein脉冲线进行了模拟仿真和实验,当充电电压超过8 kV(40 kV/cm)后,开关开始了雪崩工作模式。当充电电压约为15 kV(75 kV/cm)时,在50 Ω负载上获得了约11 kV的脉冲电压,实验波形与仿真波形一致。对开关抖动进行了测试,其测试结果显示开关充电电压对抖动影响很大,随着开关偏压增加,开关抖动减小,开关获得了最小抖动约700 ps。     

DEVELOPMENT OF PHOTOCONDUCTIVE SWITCH AND ITS APPLICATIONS

The picosecond photoconductive switches are developed and used to detect the pulse laser waveform. By using the photoconductive switches, an novel lab model of ultra-wide band(UWB) radar is also developed. The experimental results are given to show the performances of the switches and the UWB radar.     

高功率超宽带电磁脉冲技术

高功率超宽带电磁脉冲源对许多应用 ,如冲击脉冲雷达、探测地雷、微波武器等是十分重要的。本文评述在快速高压开关和超宽带天线发展中的最新进展 ,讨论了未来这类超宽带源研究的技术挑战和发展前景     

高倍增超快高压GaAs光电导开关触发瞬态特性分析

首次提出"发光畴"模型对强电场下GaAs光电导开关高倍增工作模式的物理机制进行解释.其要点是:光注入载流子引起开关电场畸变,开关偏置在触发电场阈值下因负阻效应产生高场畴,畴内发生碰撞电离引起载流子的雪崩倍增,相伴而生的辐射复合发射光子替代了已消失的触发光脉冲,畴的运动与发光使载流子以10⁸cm/s的速度穿越电极间隙,畴生存条件决定Lock-on电场,当外电路的控制使开关电场不能维持畴的生存时,开关电阻恢复.     

Ultrafast pulse generation in photoconductive switches

Carrier and field dynamics in photoconductive switches are investigated by electrooptic sampling and voltage-dependent reflectivity measurements. We show that the nonuniform field distribution due to the two-dimensional nature of coplanar photoconductive switches, in combination with the large difference in the mobilities of holes and electrons, determine the pronounced polarity dependence. Our measurements indicate that the pulse generation mechanism is a rapid voltage breakdown across the photoconductive switch and not a local field breakdown     

Ultra-wideband radar using Fourier synthesized waveforms

Traditional methods of ultra-wideband (UWB) radar signal generation suffer from several disadvantages such as low antenna radiation efficiency and lack of accurate control of signal parameters like pulse shape, pulse repetition interval (PRI), and its spectrum. UWB signals can be generated by expanding the desired radar waveform in a Fourier series and then synthesizing the waveform by generating the individual terms in the expansion from harmonically related oscillators. Signals thus produced overcome the disadvantages of traditional methods of UWB signal generation. Fourier series based method for generation of complex amplitude coded waveforms is developed which can be used to generate time domain equivalent of Barker and other codes for application in radar and communication areas. In radar applications, these coded waveforms, with accurate and stable waveform parameters, shall allow pulse compression and coherent integration. The additional processing gain provided by these operations reduces the need for high peak power in radar transmitters which is one of the bottlenecks in the implementation of operational UWB radars. This paper also describes a UWB radar concept which incorporates Fourier synthesized waveforms. Related digital signal processing issues are also discussed     

激光触发GaAs光电导开关非线性现象的实验研究

实验研究了光电导开关的非线性现象,结果表明用半导体激光脉冲串触发光电导开关,在保持激光触发GaAs光电导开关实验条件不变的情况下,产生非线性的电阚值会不断降低.测量和比较试验前后光电导开关暗电阻,初步表明产生非线性的电阈值降低,是光电导开关因光照和产生非线性引起内部材料物理机制发生变化所致.     

Characteristics of a photoconductive detector as an optoelectronic switch

Measurements of the wavelength, signal frequency, and position sensitivities of GaAs field effect transistors used as photoconductive detectors are presented. Switching of the optical sensitivity by means of both the drain and gate voltages are demonstrated. The former method can provide the basis for employing such photoconductive detectors as optoelectronic wide-band switches. The observed properties of the field effect transistor (FET) devices studied shows that the design of photoconductive optoelectronic switches will involve compromises between sensitivity and isolation in choosing the operating wavelength, and among frequency response, power consumption, and physical size in choosing the physical layout of the device.     

利用光触发产生超短电磁脉冲及其应用前景

本文对利用超短激光脉冲触发半导体光导开关产生超短电磁脉冲的装置、器件、材料以及应用方面的研究状况进行了介绍。     

Code-Division Multiple Transmission for High-Speed UWB Radar Imaging With an Antenna Array

The ultrawideband (UWB) radar is a promising high-resolution 3-D imaging technique for near targets. We have developed a high-speed imaging algorithm, SEABED, for a UWB pulse radar, a key real-time imaging technology. When the algorithm is applied to UWB, antenna scanning for data acquisition takes significantly longer than calculating the SEABED algorithm itself. This presents a serious problem for the real-time application of UWB radar. In this paper, we use pseudonoise (PN) sequences as the transmitting waveforms, while the original work on the SEABED algorithm assumed impulsive short-wave pulses. Using PN sequences enables us to simultaneously transmit signals with multiple antennas, eliminating the need to scan antennas. We demonstrate that the proposed radar system works well using random sequences to suppress direct waves, which is critical in achieving high speeds for imaging.