THz辐射的研究和应用新进展

THz频段是一个非常具有科学价值但尚未开发的电磁辐射区域,它的研究涉及物理学、光电子学及材料科学等,它在成像、医学诊断、环境科学、信息通信及基础物理研究领域有着广阔的应用前景和应用价值。当今,获得THz波的方法及THz波的探测研究是THz研究领域的前沿,更是重点。本文综述了THz波的特点、应用领域及发展状况,阐述了THz波的产生方法其探测方法。     

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。     

THz技术及其在军事中的应用研究

为探索THz技术在军事中潜在的应用方向,本文研究了产生及检测THz辐射源的方法,针对THz波的特点,分析了THz技术在隐身飞机、探测弹道导弹及安全检测方面的应用。     

利用真空电子器件产生THz技术的发展

THz波技术在生物医学、材料科学、天文学和军事通信等方面都具有广泛的应用前景.介绍了几种能够产生THz波的真空电子器件的工作机理及其在发展过程中遇到的瓶颈问题,并得出了利用真空电子器件产生THz波的各种优势.介绍了国内外各种太赫兹真空电子器件研究的技术水平及应用现状,并对用真空电子器件产生THz波的技术进行了展望.     

聚乙烯材料的THz吸收特性实验

THz辐射能够穿透很多对可见光不透明的非金属、非极性材料,而用x辐射对这些材料成像的对比度又相对低,因此,THz成像在军事和安全领域日益受到重视.对成像材料的THz特性的实际测量是THz成像技术的重要组成部分.文中利用CO2泵浦THz激光对聚乙烯材料的THz吸收特性进行了实验研究.根据实验数据拟合得出所用聚乙烯材料在70.51、96.5、118.83、122.4、158.51、184.31、214.58 μm波长的吸收系数.     

THz技术在大气探测领域的应用研究进展

THz波的频段范围（0.1~10 THz）及其特性使THz波具有较高的空间分辨率及大气参数灵敏性,同时THz辐射在地球辐射平衡中的重要作用决定了其在大气探测领域有重大的研究价值和广阔的应用前景。介绍了THz技术在大气探测领域的应用现状,重点分析介绍了THz波遥感探测大气水汽廓线、温度廓线、卷云的微物理参数及大气微量气体成分的原理、特性及存在的问题,最后对THz波大气探测技术的研究提出几点建议和展望,并指出了当前THz波大气探测技术的研究前沿和研究热点。     

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。     

铌酸锂强场太赫兹非线性时域光谱系统

强场太赫兹（THz）时域光谱技术在强场THz科学技术与应用中具有重要作用，材料、物理、化学、生物等领域诸多涉及强场THz与物质强非线性相互作用的研究都离不开强场THz时域光谱技术。然而，受限于高效率、高光束质量、高稳定性、高重复频率强场THz辐射源的性能，强场THz时域非线性光谱技术发展缓慢。针对强场THz非线性光谱技术及其潜在应用中存在的难题与挑战，在商用kHz钛宝石激光器的驱动下，笔者设计并实现了一套基于铌酸锂倾斜波前技术产生强场THz的高度集成化时域光谱系统。在3 mJ激光能量泵浦下，利用该系统在室温下实现了单脉冲能量为6.5μJ、峰值场强约为350 kV/cm的THz强场产生，该系统具备强场THz非线性光谱测试、THz泵浦-THz探测、光泵浦-THz探测、THz发射谱测量等多种超快时间分辨测量功能，是研究强场THz非线性效应的有效实验手段。     

THz焦平面探测器及其成像技术发展综述

THz探测器作为THz成像系统的核心器件,一定程度上制约着THz成像技术的发展,鉴于单元/多元探测器的光机扫描成像模式存在的问题,THz焦平面探测器成像成为THz探测技术发展的方向。介绍了近年来国内外在THz焦平面探测器,特别是基于VOx的THz焦平面探测器及其成像技术的研究进展,分析了THz焦平面探测器及其成像模式的发展前景。本文对于研究THz成像技术及应用的发展具有重要的参考意义。     

THz 遥感技术的应用进展

近年来,在射电天文学、大气科学发展的推动作用下,THz 时域光谱技术发展迅速,被广泛地应用于遥感领域。介绍了与THz 遥感相关的技术和应用,包括地球观测系统和射电天文学,突出了THz 遥感技术与其他学科之间的紧密联系,显示出了巨大的应用前景。美国、欧洲、日本在THz 遥感领域起步较早,拥有一些成熟的技术和设备;中国起步较晚,技术上和国际先进水平还有一定差距。     

Electromagnetic Scattering Characteristics of PEC Targets in the Terahertz Regime

Electromagnetic (EM) scattering characteristics of perfectly electrical conducting (PEC) targets in the terahertz (THz) frequency range are investigated through the use of ray-based high-frequency EM techniques. These techniques include the methods of shooting and bouncing rays (SBR), and the truncated-wedge incremental-length diffraction coefficients (TW-ILDCs). The EM fields associated with each ray are tracked and computed, based on the principle of Physical Optics (PO) and/or Geometrical Optics (GO). The total field scattered from the PEC target is then obtained by summing up the EM contributions of each ray and each illuminated edge. In contrast to previously reported applications, these methods are combined together to solve three-dimensional (3D) scattering problems in the THz region. Due to the use of analytical formulas of Physical Optics and the truncated-wedge incremental-length diffraction coefficients method, the consideration of the multi-reflection effect in shooting and bouncing rays, and partially accounting for the second-order edge-diffraction effects in the truncated-wedge incremental-length diffraction coefficients method, we obtain an extremely efficient algorithm for studying THz scattering. It has excellent agreement with an accurate integral solver, the Multilevel Fast Multipole Algorithm (MLFMA), which cannot be used in handling large-scale THz problems. Both mono- and bistatic radar cross sections (RCS) of several PEC objects in the THz band are given to show the correctness and reliability of the asymptotic methods. The EM scattering characteristics of such targets in the THz region are analyzed. Great differences of the target characteristics between the THz and GHz regimes are observed and discussed.     

Invited Review Article: Current State of Research on Biological Effects of Terahertz Radiation

Terahertz (THz) imaging and sensing technologies are increasingly being used in a host of medical, military, and security applications. For example, THz systems are now being tested at international airports for security screening purposes, at major medical centers for cancer and burn diagnosis, and at border patrol checkpoints for identification of concealed explosives, drugs, and weapons. Recent advances in THz applications have stimulated renewed interest regarding the biological effects associated with this frequency range. Biological effects studies are a valuable type of basic science research because they serve to enhance our fundamental understanding of the mechanisms that govern THz interactions with biological systems. Such studies are also important because they often times lay the foundation for the development of future applications. In addition, from a practical standpoint, THz biological effects research is also necessary for accurate health hazard evaluation, the development of empirically-based safety standards, and for the safe use of THz systems. Given the importance and timeliness of THz bioeffects data, the purpose of this review is twofold. First, to provide readers with a common reference, which contains the necessary background concepts in biophysics and THz technology, that are required to both conduct and evaluate THz biological research. Second, to provide a critical review of the scientific literature.     

太赫兹波在Kolmogorov湍流大气中的水平传输特性研究

太赫兹的大气传输特性对太赫兹的空间应用非常重要.对太赫兹波在Kolmogorov湍流大气中的水平传输特性展开了研究.分析了太赫兹平面波在湍流大气中传输时其闪烁指数、饱和距离等参数随频率、空间传输距离和湍流强弱程度等因素的变化.以高斯波束为例,研究了太赫兹波束在湍流大气中传输时闪烁指数、束宽等参数随传输距离等物理量的演化规律.研究结果表明,在太赫兹波段,频率越高,闪烁指数越大,饱和距离就越小.总体上看,太赫兹波在大气中传输时受大气湍流的影响程度介于光波和微波之间;对于太赫兹大气通信和成像等短程应用,太赫兹波在湍流大气中传输时一般都处于弱起伏状态;但对于太赫兹雷达和遥感等应用,由于传输距离较远,可能会出现强起伏.     

THz辐射大气传输研究和展望

THz辐射在大气中的传输特性是THz波空间通信、大气科学及遥感检测等空间应用的基础,掌握不同温度、高度、湿度和压力等条件下THz频段大气透过率窗口的位置和宽度对于促进该频段的应用具有重要意义。本文分析了THz辐射大气传输的研究概况,包括大气传输的基本原理,辐射传输方程的推导以及对各类THz辐射大气传输模型的比较,并指出尚待解决的问题,最后对THz辐射大气传输研究给出若干建议和展望。     

太赫兹波谱与成像

主要介绍太赫兹技术的两大基本应用领域:波谱技术与成像技术。总结了太赫兹波谱学中的时域光谱技术、时间分辨光谱技术和发射光谱技术以及相关的参数提取原理。介绍了太赫兹成像原理及相关的时域扫描成像、实时成像、层析成像、连续波成像和近场成像等太赫兹成像技术。列举了太赫兹光谱和成像技术在国家安全、生物研究、材料研究、无损检测等方面的应用。     

Review of Terahertz Technology Readiness Assessment and Applications

Technological progress in Terahertz (THz) instrumentation in recent years has produced commercial THz systems with excellent performance, smaller footprint, easier to use operation and more reliable than their homemade laboratory predecessors. Form factor, weight, and data rate are, perhaps, the parameters that have shown the highest improvements in recent years. These parameters also have a major impact on practical application outside the laboratory environment. However, gaps still exists between proof of concepts demonstrated in the laboratory and application requirements in a real environment. The readiness of a technology can be assessed using the Technology Readiness Level (TRL) criterion, which considers nine readiness levels starting from basic concepts at TRL=1 up to full deployment at TRL=9. Applications of THz technology in spectroscopic characterization score high in TRL (7-9) because most of the progress of THz technology has been mainly focused in developing THz instrumentation for spectroscopy. Applications of THz for non-destructive evaluation applications score lower (TRL 5-6) due to higher requirements in terms of performance, especially data rate and form factor in imaging applications. Applications in the medical field have been studied with promising results but they are still in early stages of development, thus, TRL is low (1-4). The progress in THz technology is generating systems with better performance (faster acquisition rates, higher signal-to-noise ratio, bandwidth), broader availability of form factors and configurations, and tighter integration with particular applications. This progress will reduce the gap between the capabilities of the technology and the high-demanding requirements of applications in environments such as quality control and in-line production control in the manufacturing industry.     

Terahertz Frequency Sensing and Imaging: A Time of Reckoning Future Applications?

In recent years, the field of terahertz (THz) science and technology has entered a completely new phase of unprecedented expansion that is generating ever growing levels of broad-based international attention. In particular,there have been important advances in state-of-the-art THz technology and very enthusiastic growth in research activities associated with related scientific and industrial applications. One can legitimately argue that the potential payoffs of THz sensing and imaging (THz S&I) to application areas such as defense, security, biology and medicine are the major drivers of this new phenomenon. However, there remain major science and technology "gaps" in the THz regime that must be reconciled before many of the perceived payoffs ever become realizable. Therefore, it is natural to ask the question "Is now the time for THz?" or rather, are these recent events just a repeat of previous cycles in THz overenthusiasm that have been witnessed during the last century? The main goal of this paper is to consider some of the most promising THz S&I applications within the specific context of their particular science and technology challenges in an attempt to credibly judge (or speculate on) their future potential.     

0.2THz连续波近场扫描成像方法及实验研究

太赫兹(Terahertz-THz)电磁波是指频率在0.1THz～10THz(波长在30μm～3mm)之问的电磁波,它的独特性质使得它在许多领域具有重要的应用前景.本文简要地综合了THz信号的产生与检测方法以及THz成像技术的发展概况,基于固态电子学和准光学技术研究了一种0.2THz连续波成像方法,利用搭建的成像系统开展了典型目标的成像实验及其图像处理方法的研究.成像结果表明, 0.2THz电磁波对泡沫塑料、纸盒、皮革等非极性材料具有较好的穿透能力,系统的成像分辨率优于3mm.本文的研究成果在安检、生物医学成像、无损检测等方面具有广阔的应用前景,也为便携式THz成像系统的实现提供了可能.     

Microstructure Functional Devices-Effectively Manipulate Terahertz Waves

Terahertz (THz) technology promises important applications including imaging, spectroscopy, and communications. However, one of limitations at present for advancing THz applications is the lack of efficient devices to manipulate THz waves. Here, our recent important progresses in THz functional devices based on artificial microstructures, such as photonic crystal, metamaterial, and plasmonic structures, have been reviewed in this paper, involving the THz modulator, isolator, and sensor. These THz microstructure functional devices exhibit great promising potential in THz application systems.