光整流太赫兹源及其研究进展

太赫兹科学技术是近20年来发展起来的一门新学科,其关键技术是太赫兹波的产生和探测.本文介绍了光整流太赫兹源的辐射原理、国内外研究情况、存在的问题等.今后其发展方向主要应为通过掺杂等手段改进光电导材料的光电特性,提高材料的相位匹配能力和减小饱和现象来提高辐射的功率和效率.     

双折射色散阶跃光纤中太赫兹脉冲的提取

根据光脉冲在双折射色散阶跃光纤中调制不稳定性,研究了双折射色散阶跃光纤中调制不稳定性增益谱随传输距离的变化关系.结果表明:在弱双折射色散阶跃光纤和强双折射色散阶跃光纤中,利用调制不稳定性增益谱随传输距离的变化关系可分离和提取THz脉冲.     

FDTD方法分析THz波段金属平板的屏蔽特性

研究了室温下金属平板对THz波的透射屏蔽特性。考虑到THz波段金属电导率的频率色散特征,基于Z变换方法处理频域色散媒质本构关系到时域的转化,使FDTD仿真易于编程实现。仿真表明,对不同金属材料,其屏蔽效应随频率呈现出周期振荡,且金属平板厚度在百nm量级时对THz波的屏蔽效应＞60 dB。对不同厚度的金属平板,其屏蔽效应以dB为单位随厚度线性增大,有望利用此特性实现厚度μ＜m级薄层金属的厚度测量。     

Experimental Confirmation of Design Techniques for Effective Bow-Tie Antenna Lengths at THz Frequencies

We present on the relationship between the bow-tie antenna length and its THz spectral emission response. Three well-known approaches for predicting accurate antenna length for a given central frequency were utilized and their validity was experimentally tested. It is shown that the simple quasi-static approach compare to other approximations is valid for frequencies up to ~1.5 THz. The bow-tie THz photoconcudtive (PC) emitter designed using this approximation exhibits THz radiation having the most accurate central frequency compared to the design frequency. Interestingly, the THz PC emitter utilized from this design technique also possesses the optimum radiation bandwidth.     

太赫兹共焦扫描显微成像研究进展

随着太赫兹(THz)技术的发展,许多改善成像质量和拓展成像维度的方法不断应用到THz成像领域,其中有许多是借鉴了在其他波段已发展成熟的技术手段,这些技术与THz成像的结合,已成为当前研究的一个热点领域,THz共焦扫描显微成像技术即是其中之一。在介绍共焦扫描显微成像原理的基础上,阐述并分析比较了国内外THz共焦扫描显微成像技术的发展状况,这些研究展示了THz共焦扫描显微成像技术广阔的应用及发展前景。     

太赫兹数字全息成像的研究进展

随着太赫兹成像技术的发展,人们对太赫兹成像系统的成像性能如分辨率、成像速率、成像维度等均提出了越来越高的要求。为了消除衍射对太赫兹成像的影响,提高太赫兹成像系统所能达到的性能指标,许多学者已针对太赫兹数字全息技术进行了研究。首先对太赫兹数字全息的基本原理进行了概述,阐述并分析了目前国内外有关太赫兹数字全息成像的研究进展,这些研究显示太赫兹数字全息技术在提高成像分辨率、扩展成像维度等方面具有很大的发展潜力,且具备实时成像的能力,具有十分广阔的应用及发展前景。     

Recent Advances in Long-distance FBG Sensor Systems at UESTC

Recent progress in long-distance in-Fiber Bragg Grating （FBG） sensor systems at University of Electronic Science ＆ Technology of China （UESTC） is reviewed in this paper. Two novel approaches with a 50km transmission distance are proposed and demonstrated. The first one is based on the combination of bidirectional Raman amplification and a dual Erbium-Doped Fiber （EDF） configuration. A good Signal-to-Noise Ratio （SNR） of ～16dB is achieved with only a pump power of ～280 mW, which is ～10 dB higher than that without amplification. The second is based on a novel tunable fiber ring laser configuration with hybrid Raman/EDFA configuration. Experimental results show that an excellent optical SNR of-～60 dB has been achieved for a 50 km transmission distance with a low Raman pump power of ～170 mW and a low EDFA pump power of～40 mW at wavelength of 980 nm. It is anticipated that these long-distance FBG sensing systems could find important applications in health monitoring of large infra-structures, such as oil or gas pipelines, ultra-long bridges and tunnels, river banks, and so on.     

CO2激光抽运太赫兹成像研究新进展

为了研究基于CO2激光抽运的远红外激光源的太赫兹2维成像方法的各自特点和今后的发展方向,在介绍CO2激光抽运的远红外激光源的基本工作原理及美、英两国典型产品SIFlR-50FPL和FIRL100激光器的基础上,重点介绍了国内外近几年的主要成像研究成果,并对其成像特性进行了简要评述。最后总结出CO2激光抽运太赫兹成像研究的发展趋势是大力发展能远距离成3维像的太赫兹雷达、能实时成像的焦平面探测及实时图像处理和目标自动识别系统。     

STN—LCD的新进展

STN-LCD采用新的取向层,消除了残象;采用新的驱动波形,消除了串扰;采用二(口恶)烷、卤化物、链烯基、醚和二苯乙炔,改进了液晶料材的性能,使STN-LCD获得高的对比度、快的响应速度、低的驱动电压;采用有源矩阵驱动方法,消除了帧响应,使STN-LCD获得高的对比度、高的亮度及视频响应速度;使用温度跟踪电路,自动跟踪STN-LCD的阀值电压,使STN-LCD获得宽的工作温度。     

蓝色波段发光和激光二极管的新进展

文章在简要概述了几种适合制备短波长发光器件材料－ＳｉＣ，ＧａＮ和ＺｎＳｅ的晶体结构、掺杂性质及外延技术后，主要介绍了它们在制备蓝色波段发光和激光二极管的新进展。     

THz波微结构器件特性的研究

在电磁波谱中所处的特殊位置使得THz波在在物理、化学、生物医学、电子科学、材料科学、环境监测等领域有着广泛的应用前景。综述了THz波微结构器件特性方面的研究工作。亚波长金属周期微结构器件的THz波谱选择增强透射现象,亚波长环形槽金属线上的THz等效表面等离子体激元,以及THz光子晶体光纤。     

THz时域频谱技术中若干效应的研究

在电磁波谱中所处的特殊位置使得THz波在物理、化学、生物医学、电子科学、材料科学、环境监测等领域有着广泛的应用前景。讨论了THz时域频谱技术的若干关键问题：THz发射晶体的双光子吸收、衍射效应和非线性效应（Kerr效应和类Kerr效应）等对THz产生效率的影响,THz辐射脉冲的载波包络相位差,THz小波变换频谱技术,以及利用光子晶体光纤飞秒激光作为激发源对THz时域频谱系统进行小型化和提高能量的方案。     

Television Broadcasting at Microwave Frequencies

Over 125 Multipoint Distribution Service (MDS) transmitting stations have been constructed over the past seven years. Each of these stations is equivalent to a low power television broadcast station operating on a microwave frequency at approximately 2,150 MHz. The problems encountered in the design and construction of an MDS station differ markedly from a VHF or UHF television station. The propagation characteristics, likewise, are significantly different than for either UHF or VHF frequencies. The solution to the problem of effective coverage and reception throughout a service area requires innovative designs and techniques, and these are described.     

Recent Advances in TWX Mechanization

Equipment is presently being manufactured which permits the TWX subscriber to place his calls directly by dialing into the DDD telephone network. This equipment comprises electronic and electromechanical devices, combined in a simple package for installation at the subscriber's premises. The Data Set, with its associated controlling Subset, provides a number of operating features which make for convenience, speed, and ease of operation, and should assure reliable operation for a great many years.     

零样本图像识别

深度学习在人工智能领域已经取得了非常优秀的成就,在有监督识别任务中,使用深度学习算法训练海量的带标签数据,可以达到前所未有的识别精确度。但是,由于对海量数据的标注工作成本昂贵,对罕见类别获取海量数据难度较大,所以如何识别在训练过程中少见或从未见过的未知类仍然是一个严峻的问题。针对这个问题,该文回顾近年来的零样本图像识别技术研究,从研究背景、模型分析、数据集介绍、实验分析等方面全面阐释零样本图像识别技术。此外,该文还分析了当前研究存在的技术难题,并针对主流问题提出一些解决方案以及对未来研究的展望,为零样本学习的初学者或研究者提供一些参考。

     

氮化铝制品的新进展

综述了AlN制品的某些新进展,包括其原料和处理、填料和坩埚、陶瓷金属化和共烧技术以及作为微波衰减材料等,强调了AlN制品的应用前景.     

计算电磁学的进展与展望

本文对计算电磁学的发展现状作了总结，对常用的电磁计算方法作了必要的分类，重点介绍了目前计算电磁学领域出现的颇有应用前景的新方法和新观点，并以今后该领域的发展方向提出了若干建议。     

微显示技术的进展

简单介绍以微显示为基础的背投影显示系统的技术和市场。着重论述LCoS、DLP/DMD、和多晶硅LCD微显示器这三种主要技术的优缺点及它们的发展前景。     

Recent Advances in Finline Circuits

Detailed studies of transmission properties of the finline coupler have revealed existence of certain phenomena which adversely affect the transmission characteristics. A discussion of the origin and successful elimination of such effects is described. New applications for the finline coupler have been found in the design of hybrid junctions, twists and bends in multimode waveguide, and other polarization selective devices. The paper concludes with a presentation of theoretical and experimental results in the application of finline techniques to low-pass microwave filters.