太赫兹光谱技术的应用进展

近年来太赫兹（THz）技术快速发展,在安全检测、航空航天、生命科学、化学等领域应用日趋广泛。由于许多炸药及其相关材料在THz波段具有特征吸收,许多非金属、非极性材料对THz波是透明的,且太赫兹波具有低能性,THz光谱技术在安检中具有巨大的应用潜力。本文介绍了太赫兹波的特性和国内外在太赫兹领域的研究进展,详细介绍了太赫兹波在爆炸物、毒品和包装材料检测中的应用,并讨论了在应用中存在的困难和面临的挑战。     

太赫兹波技术在药学上的应用研究

太赫兹(THz)辐射是一种新型的远红外相干辐射源,太赫兹时域光谱技术是利用太赫兹脉冲研究物质物理化学性质的一种新兴光谱技术,具有很多独特的性质。由于很多极性生物大分子的振动和旋转能级都处于在太赫兹波段内,因此利用太赫兹时域光谱技术和太赫兹成像技术研究药品的结构,分析药品的成分,对控制药品的质量稳定性具有重要的意义。综述了近些年来太赫兹技术在药品领域上的应用成果,探讨了存在的问题,并对发展前景进行了展望。     

不同热老化程度的植物绝缘油太赫兹时域光谱特性研究北大核心CSCD

植物绝缘油因其较好的绝缘性能及绿色环保等优势,逐渐成为传统矿物绝缘油替代品研究的热点。太赫兹波段光谱具有独一无二的指纹特征吸收峰,使其成为近年来物质检测热点技术之一。文中利用绝缘油的太赫兹时域光谱快速、准确、稳定的数据采集特性,对植物绝缘油的老化状态进行诊断。首先,利用改进的电磁波传递函数消除了仪器和容器的法布里—珀罗(F-P)效应。然后计算出植物绝缘油的吸收系数、折射率等THz谱参数,分析了植物绝缘油在太赫兹区域的介电性能。最后,与相应老化状态下的糠醛浓度进行对比,结果表明,糠醛浓度与平均折射率有相同的变化趋势。研究结果为THz-TDS技术在植物绝缘油老化状态评估领域的应用提供了很好的参考。     

基于调频连续波的太赫兹透视测距技术

由于太赫兹波能够穿透非金属、非极性材料,太赫兹技术能够弥补激光技术的不足,实现对目标内部的透视测距。研究分析提出基于线性调频连续波的太赫兹透视测距技术,实现了多种材料的厚度以及多层介质材料的介电常数的非接触式测量,进一步拓展了太赫兹线性调频连续波的应用范围,为材料介电常数测量提供了新途径。以3种常见的材料作为检测目标,利用0.11～0.17 THz、0.17～0.22 THz、0.22～0.33 THz、0.33～0.50 THz 4个频段的太赫兹线性调频连续波实验验证方法的有效性,并证明厚度测量和介电常数测量的精度随信号带宽的增加而提高,误差最小均可达到1%以下。此外,以雷达天线罩陶瓷材料作为检测目标,应用太赫兹透视测距的原理,结合二维扫描架获取样品的全部信息,实现了对内部缺陷的透视成像与定位。     

太赫兹反射成像技术在复合绝缘子硅橡胶内部缺陷检测中的评述

由于太赫兹波穿透能力强、成像分辨率高、抗干扰能力强等优点,基于太赫兹反射成像方式的无损检测技术成为绝缘子缺陷检测领域的研究热点。本文首先介绍了介质中太赫兹波的传播特性,构建传播模型分析了存在缺陷时因介质不连续性导致缺陷界面处的太赫兹波折反射现象。然后概述了电磁波的时域有限差分法（FDTD）,基于FDTD理论的电场随时间...     

基于共振隧穿机制的太赫兹波振荡器特性模拟

共振隧穿器件由于其具有高频高速的特点,适用于制作太赫兹波段的振荡源器件。本文主要针对太赫兹波段的共振隧穿二极管(RTD)的振荡特性进行模拟仿真。利用等效电路理论和Pspice软件对共振隧穿振荡器(RTO)的等效电路模型进行振荡频率和功率的模拟计算。在理论计算中将隧穿和渡越时间效应以及寄生元件等制约因素都进行了分析,结果表明通过改进RTD和缝隙天线的结构,共振隧穿振荡器的振荡频率可达1.2THz,输出功率可达到115?W。并且在Pspice仿真环境下进行验证,结果也与理论计算较为相符。     

太赫兹波技术在电网设备绝缘材料检测中的应用

太赫兹波在绝缘介质中具有良好的穿透性、直线性、抗干扰性,且对人体无害,随着太赫兹波发射和探测技术的成熟,在材料无损检测、光谱分析、航空、医学等领域开始广泛应用。文中阐述了太赫兹波的产生、探测原理,以及太赫兹透射波、反射波在绝缘介质检测中的探测方式;分析了基于时域、频域信号的特征参量对被测物体进行太赫兹成像的原理;最后,综合阐述了太赫兹波在电网设备绝缘材料检测中的应用场景和技术可行性。     

太赫兹科学技术在生物医学中的应用研究

介绍了近十年来国内外太赫兹科学技术在生物医学领域的研究与应用进展.重点总结了太赫兹辐射的生物效应、太赫兹光谱技术和太赫兹成像技术,在生物医学领域的研究与应用的3个大类的成果.有关太赫兹辐射的生物效应,分不同频率、不同功率和不同辐射时间下样品的生物学反应来介绍.又根据探测样品属性不同分为生物体、生物组织、生物细胞、生物细胞器和生物大分子等6个层次的内容.充分论证了太赫兹科学技术对生物医学的安全性和适用性.由于太赫兹光谱包含丰富的生物分子及分子间的组成信息和构象信息,在生物医学领域的研究与应用最多.对不同生物大分子的太赫兹特征频谱进行了解读,对太赫兹光谱技术的应用进行了梳理,目的为让更多的人了解太赫兹科学技术的优越性和应用前景.在太赫兹渡成像技术方面,总结了其在癌变组织诊断、皮肤烧伤探测等方面的研究应用.为使迷人的太赫兹波科学与技术更好的服务于人类,尝试较为全面地对太赫兹科学技术在生物医学领域取得的研究成果进行归纳与总结,同时也探讨了现阶段在生物医学领域所存在的不足,以及今后努力的方向.     

基于USB的主动太赫兹成像电路设计

简要介绍了一套针对双波段主动太赫兹无损检测系统研制的基于USB通信的电路系统.该电路系统可通过控制二维扫描机构实现太赫兹无损检测系统的二维扫描,利用双波段太赫兹探测器接收经目标反射的由双波段太赫兹源辐射的太赫兹信号,并对该信号利用过采样方式实现数据采集,通过USB实现数据的上位机传输,并最终利用频域滤波和小波变换等图像处理技术实现主动太赫兹成像.成像结果表明,电路系统符合实际需求,双波段太赫兹无损检测系统可实现分辨率3 mm的无损检测,能很好地满足泡沫等非极性材料的无损检测的应用需求.     

太赫兹技术在电气设备绝缘缺陷检测研究综述

太赫兹波在绝缘介质材料传播中不仅具有衰减小,准直性强,穿透性好等优点,而且在成像可视化方面具有较高的分辨率,深受电气设备绝缘缺陷检测领域学者的喜爱。首先概述了太赫兹波的产生和探测技术,介绍了太赫兹时域光谱技术和基于时域、频域信号的特征参量对绝缘缺陷成像的原理,给出了电气设备绝缘缺陷应用太赫兹波检测的典型案例,探讨了目前存在的探测方式选取、缺陷类型识别、在线监测可行性的相关问题,最后对太赫兹技术在电气设备绝缘缺陷检测领域的前景进行了展望。     

太赫兹科学技术研究的新进展

近年来,太赫兹科学与技术研究得到了巨大的发展,除了传统的太赫兹辐射源、太赫兹探测、太赫兹光谱与太赫兹成像研究以外,太赫兹遥感、太赫兹雷达、太赫兹通信、太赫兹计量、太赫兹无损检测以及太赫兹技术在材料表征、环境监测、石油化工、航空航天、生物医学、军事国防、国家安全等方面的应用都得到了全面的发展。本文在回顾二十多年来太赫兹科学技术研究所取得的一些主要成果的基础上,重点介绍近年来太赫兹科学技术研究的新进展,对太赫兹技术本身的发展及其应用趋势进行展望。     

Focused ion beam nanopatterning for optoelectronic device fabrication

Recent photonic device structures, including distributed Bragg reflectors (DBRs), one-dimensional (1-D) or two-dimensional (2-D) photonic crystals, and surface plasmon devices, often require nanoscale lithography techniques for their device fabrication. Focused ion beam (FIB) etching has been used as a nanolithographic tool for the creation of these nanostructures. We report the use of FIB etching as a lithographic tool that enables sub-100-nm resolution. The FIB patterning of nanoscale holes on an epitaxially grown GaAs layer is characterized. To eliminate redeposition of sputtered materials during FIB patterning, we have developed a process using a dielectric mask and subsequent dry etching. This approach creates patterns with vertical and smooth sidewalls. A thin titanium layer can be deposited on the dielectric layer to avoid surface charging effects during the FIB process. This FIB nanopatterning technique can be applied to fabricate optoelectronic devices, and we show examples of 1-D gratings in optical fibers for sensing applications, photonic crystal vertical cavity lasers, and photonic crystal defect lasers.     

Silicon photonics

The silicon chip has been the mainstay of the electronics industry for the last 40 years and has revolutionized the way the world operates. Today, a silicon chip the size of a fingernail contains nearly 1 billion transistors and has the computing power that only a decade ago would take up an entire room of servers. As the relentless pursuit of Moore's law continues, and Internet-based communication continues to grow, the bandwidth demands needed to feed these devices will continue to increase and push the limits of copper-based signaling technologies. These signaling limitations will necessitate optical-based solutions. However, any optical solution must be based on low-cost technologies if it is to be applied to the mass market. Silicon photonics, mainly based on SOI technology, has recently attracted a great deal of attention. Recent advances and breakthroughs in silicon photonic device performance have shown that silicon can be considered a material onto which one can build optical devices. While significant efforts are needed to improve device performance and commercialize these technologies, progress is moving at a rapid rate. More research in the area of integration, both photonic and electronic, is needed. The future is looking bright. Silicon photonics could provide low-cost opto-electronic solutions for applications ranging from telecommunications down to chip-to-chip interconnects, as well as emerging areas such as optical sensing technology and biomedical applications. The ability to utilize existing CMOS infrastructure and manufacture these silicon photonic devices in the same facilities that today produce electronics could enable low-cost optical devices, and in the future, revolutionize optical communications.     

Active Plasmonics: Surface Plasmon Interaction With Optical Emitters

The interaction between surface plasmons and optical emitters is fundamentally important for engineering applications, especially surface plasmon amplification and controlled spontaneous emission. We investigate these phenomena in an active planar metal-film system comprising InGaN/GaN quantum wells and a silver film. First, we present a detailed study of the propagation and amplification of surface plasmon polaritons (SPPs) at visible frequencies. In doing so, we propose a multiple quantum well structure and present quantum well gain coefficient calculations accounting for SPP polarization, line broadening due to exciton damping, and particularly, the effects of finite temperature. Second, we show that the emission of an optical emitter into various channels (surface plasmons, lossy surface waves, and free radiation) can be precisely controlled by strategically positioning the emitters. Together, these could provide a range of photonic devices (for example, surface plasmon amplifiers, nanolasers, nanoemitters, plasmonic cavities) and a foundation for the study of cavity quantum electrodynamics associated with surface plasmons.      

Modelling surface effects in nano wire optoelectronic devices

Recent research on optoelectronic devices focuses on nano structuring which is expected to improve the performance and reduce the production costs of light emitting diodes for lighting purposes and solar cells, for instance. Structuring on the sub-micrometer scale increases the surface with respect to the active volume so that surface effects become crucial for the device performance. In this work we demonstrate the computational modelling of nano structured optoelectronic devices to complement the experiment. The implementation of the simulation model considers surface effects in these devices using a true area box method discretization. The derived surface models are applied on the self-consistent simulation of nano wire quantum disk light emitting diodes. By the computational study we demonstrate that the surface physical effects are critical for the performance of nano-structured optoelectronic devices and that surface recombination can lead to a low efficiency.     

DWDM技术进展及光复用器

随着科学技术的发展，光纤通信已成为通信领域的一个重要分支。当前，光纤通信技术的研究十分活跃。文中简要介绍了密集波分复用技术(DWDM)的发展、演变及应用情况，并对光复用器原理和特性进行了探讨和比较。     

宽禁带功率电子器件及其应用专辑特邀主编述评

正相较于传统的硅器件,基于宽禁带半导体材料的功率电子器件在很多方面都体现出了优越的性能,符合功率变换器高效率、高工作温度及高功率密度的发展需求。近几年来,碳化硅(SiC)和氮化镓(GaN)功率器件的制造技术发展迅速,多家公司推出了系列商业化产品,宽禁带功率电子器件及其     

What to Expect in Solid-State Industrial Drive Systems

Solid-state control has rapidly replaced conventional electromechanical devices and vacuum tube electronics in its first decade of industrial usage. The growth of solid-state applications has been evolutionary and based on a practical approach to utilizing the optimum available solution, both economically and technologically, to achieve improved control system reliability and performance. The application of solid-state electronic devices is discussed from the input of the operator's commands through a typical industrial control system to the power conversion equipment that supplies the drive motor. Frequency of failures in solid-state devices is so low that maintenance men do not retain familiarity with circuits and device theory. This has necessitated the need for low-level maintainability through the use of functional plug-in printed circuit cards, full-time instrumentation, light-emitting diode logic status indicators, and system engineered diagnostic test circuits built into the system. The future looks promising for further technological developments in solid-state devices. A continued growth in solid-state industrial drive systems is assured with expected trends toward further development of adjustable frequency power conversion systems, and hybrid logic/control systems.     

Terahertz Science and Technology Trends

The recent progress in terahertz science and technology (THz-S&T) opens up a range of potential research opportunities. Historically, THz technologies were mainly used by the astronomy community for searching far-infrared radiation (cosmic background), and by the laser fusion community for the diagnostics of plasmas. Since the first demonstration of THz wave time-domain spectroscopy in the late 1980s, there has been a series of significant advances (particularly in recent years) as intense THz sources and more sensitive detectors provide new opportunities for understanding the basic science in the THz frequency range. THz radiation can penetrate through many nonpolar dielectric materials and can be used for nondestructive/noninvasive sensing and imaging of targets under nonpolar, nonmetallic covers or containers. An immediate application of THz wave technology is in nondestructive testing or inspection. Short-term applications (within three to five years) are expected in spectroscopic sensing and imaging for homeland security. Biomedical applications are expected in the long term (five to ten years). By comparing the publication record trend of THz-S&T related papers with the publication record of proxy fields (laser, microwave, Raman, and infrared), it is possible to anticipate that the number of publications in the THz-S&T arena will increase and also the impact in other research areas. We compare the publication pattern (number of papers versus time) with searching keywords in title or abstract. We found that all the publication trends share a common pattern with four periods defined by discovery, acceptance, adoption, and maturity. From this pattern trend, THz-S&T seems to be in an acceptance period. The unique properties of THz-S&T suggest that its applications will grow.