基于BWO连续太赫兹波成像系统的无损检测

介绍了一种基于返波管（BWO）的太赫兹波成像系统。BWO连续太赫兹波成像是一种新的无损检测方法。实验过程中把样品放在X-Z二维电控平移台上进行扫描成像,透过样品的太赫兹波强度信息由热释电探测器接收,然后经过电脑成像。给出了应用0.71THz的连续太赫兹波对打孔铝板、公交卡、校园卡的内部结构和对隐藏在信封内硬币等物体和信封内纸片上的铅字迹的成像实验研究事例,并且测知该系统能够分辨出直径最小为1.5mm的小孔。这项工作揭示了使用BWO连续太赫兹波成像系统在无损检测和安全检查领域是有效的。     

太赫兹激励的红外热波检测技术

本文的目的在于探索一种新的适用于红外热波检测技术的热激励方式——太赫兹(THz)热激励. 文中介绍了THz波周期性热激励的热传导理论模型; 尝试利用返波振荡器(返波管backward wave oscillator, BWO)太赫兹源对一块碳纤维基底吸波涂层板进行周期性THz热激励, 红外热像仪连续观测和记录试件表面温场变化, Canny边缘算法处理热图像显示缺陷; 检测结果与闪光灯脉冲激励的结果进行比较, 讨论了太赫兹波激励红外热波检测技术可能的优势. 实现了THz技术与红外热波无损检测技术的结合.     

太赫兹数字全息术的研究进展

随着太赫兹成像技术的不断成熟,其空间分辨率和系统信噪比逐渐提高,成像速度逐渐加快,光学信息获取能力逐渐变强,人们对太赫兹成像在基础研究和工业应用的开发也逐渐深入。本文综述了近年来科研人员利用太赫兹数字全息成像系统进行的部分研究工作,包括对平板太赫兹元件的性能表征、对光控太赫兹元件的功能验证、对衍射太赫兹场中的纵向分量进行观测、以及对金属亚波长器件的太赫兹表面波进行分析。这些工作的完成对于太赫兹集成系统的研究和太赫兹成像技术的应用都具有积极的推动作用。     

TERA-MIR radiation: materials,generation, detection and applications

This special edition is dedicated to original papers covering topics with the areas of interest of COST ACTION MP1204 whose main objective is to advance novel materials, concepts and device designs for generating and detecting THz (0.3–10 THz) and Mid Infrared (10–100 THz) radiation using semiconductor, superconductor, metamaterials and lasers and to beneficially exploit their common aspects within a synergetic approach. The results achieved benefit from the unique networking and capacity-building capabilities provided by the COST framework to unify these two spectral domains from their common aspects of sources, detectors, materials and applications. We are building a platform to investigate interdisciplinary topics in Physics, Electrical Engineering and Technology, Applied Chemistry, Materials Sciences and Biology and Radio Astronomy. In this sense THz and MIR are considered jointly, the driving force for both regimes being applications. The main emphasis of the research presented here is on new fundamental material properties, concepts and device designs that are likely to open the way to new products or to the exploitation of new technologies in the fields of sensing, healthcare, biology, and industrial applications. End users are: research centres, academic, well-established and start-up companies and hospitals. The strong coupling of THz radiation and material excitations has potential to improve the quantum efficiency of THz devices.     

太赫兹液晶材料与器件研究进展

液晶是一种性能优异的可调控光电功能材料,基于液晶的太赫兹器件有着广泛的应用前景,但高性能太赫兹功能器件的研发仍处于初级阶段.本文综述了太赫兹领域液晶材料与器件的研究现状,探讨了液晶技术与太赫兹技术相结合的发展趋势.     

Terahertz sensing and imaging based on nanostructured semiconductors and carbon materials

The advantageous properties of terahertz (THz) waves, such as permeability through objects that are opaque for visible light and the energy spectrum in the microelectron‐volt range that are important in materials research, allow their potential use in various applications of sensing and imaging. However, since the THz region is located between the electronic and photonic bands, even the basic components such as detectors and sources have not been fully developed, unlike in other frequency regions. THz technology also has the problem of low imaging resolution, which results from a considerably longer wavelength than that of the visible light. However, the utilization of nanostructured electronic devices has recently opened up new horizons for THz sensing and imaging. This paper provides an overview of the THz detector and imaging techniques and tracks their recent progress. Specifically, two cutting‐edge techniques, namely, frequency‐selective THz‐photon detection and integrated near‐field THz imaging, are discussed in detail. Finally, the studies of superconductors and semiconductors with high‐resolution THz imaging are described.     

Heterodyne spectrometers

An overview is given on current heterodyne receiver technology and on heterodyne receivers for astronomical and atmospheric science applications. The principle of heterodyne receivers is explained. Technological developments in the fields of THz mixer, local oscillators (LOs) and wideband spectrometers are described. A review on existing airborne and spaceborne heterodyne receivers is given. Finally, possible future THz heterodyne receivers for the ESA-cornerstone FIRST (far-infrared and submillimeter telescope) and the astroplane SOFIA (Stratospheric Observatory for Infrared Astronomy) are outlined.     

Terahertz planar lenses based on plasmonic metasurfaces

Plasmonic planar lenses on silicon substrate are designed to realize terahertz (THz) wave focusing. Super-unit-cells containing eight different resonant units are presented to construct eight concentric rings on the silicon substrate. By controlling of the position distribution of the resonant units, it is shown that focusing at 4.3 THz can be achieved. Moreover, due to that the eight units can steer THz wave and keep phase gradient in frequency range of 4.2 to 4.5 THz, the metalenses can realize broadband THz focusing. The results imply the potential applications in THz wave control devices of light collection and multi-channel optical communication.     

太赫兹波段液晶分子极化率的理论研究

近年来,太赫兹(THz)波段电磁辐射的研究引起科学技术界广泛的关注.液晶(LC)材料具有宽带可调的特性且拥有成熟的工业技术基础,在基于液晶设计的太赫兹可调器件研究中显示了巨大的应用潜力.因此,为了快速发展实用的LC-THz调制器件,对液晶材料在太赫兹频率范围内的光电特性进行系统的了解是至关重要的.分子极化率是表征分子中电荷分布的重要物理量.采用密度泛函理论方法对液晶分子PCH5,5CB和5OCB在太赫兹波段的极化率性质进行计算研究,从电子结构的角度,利用极化率密度分析方法考察了分子不同区域对极化率数值的贡献,详细探讨了尾链、核心结构和极性取代基等不同基团对极化率及其各向异性的影响.     

太赫兹波频域的GaAs材料特性

利用返波振荡器(BWO)系统对不同电阻率的GaAs在太赫兹波段的透射谱进行了测试,并对太赫兹波透射谱进行了计算和分析,得到不同电阻率的GaAs材料在太赫兹波0.23～0.375 THz波段范围的折射率、吸收系数和介电常数实部和虚部等光学特性参数。实验结果表明,不同电阻率的GaAs在整个测试太赫兹波频段内的折射率,吸收系数,介电常数实部和虚部均随着电阻率的增加而增加。高电阻率的GaAs材料对太赫兹波的吸收很小,其最小吸收系数可达到3.87×10-4 cm-1。同时也表明采用返波振荡器系统研究分析GaAs在太赫兹波段特性是可行的。研究不同电阻率的GaAs在太赫兹波段的光学特性,对设计高效率太赫兹波天线具有重要意义。     

Methods of terahertz-subterahertz BWO spectroscopy of conducting materials

This paper considers present spectroscopic methods developed for measurement of dielectric response (conductivity and permittivity spectra) of condensed media in the terahertz-subterahertz spectral regions. The techniques based on the use of BWO spectrometers and designed for direct quantitative measurements (without invoking the Kramers-Kronig relations) in the terahertz-subterahertz frequency range (0.03–1.45 THz) of the conductivity σ(ν) and permittivity ?′(ν) spectra of conducting and absorbing materials are described. The techniques are based on measuring the amplitude and phase of the transmission coefficient of film samples on dielectric substrates and the reflection coefficient of a reference plane-parallel dielectric plate contacting the surface of the sample under study. The use of these techniques in measurement of the σ(ν)) and ?′(ν) spectra of conductors and superconductors is illustrated with examples.     

Terahertz spectroscopy of DNA

The spectra of the degraded DNA of herring are studied using two methods of THz spectroscopy that employ a femtosecond laser and a frequency synthesizer based on a BWO and a high-Q cavity. An interpretation of the experimental results is presented.     

Terahertz band: Next frontier for wireless communications

This paper provides an in-depth view of Terahertz Band (0.1–10 THz) communication, which is envisioned as a key technology to satisfy the increasing demand for higher speed wireless communication. THz Band communication will alleviate the spectrum scarcity and capacity limitations of current wireless systems, and enable new applications both in classical networking domains as well as in novel nanoscale communication paradigms. In this paper, the device design and development challenges for THz Band are surveyed first. The limitations and possible solutions for high-speed transceiver architectures are highlighted. The challenges for the development of new ultra-broadband antennas and very large antenna arrays are explained. When the devices are finally developed, then they need to communicate in the THz band. There exist many novel communication challenges such as propagation modeling, capacity analysis, modulation schemes, and other physical and link layer solutions, in the THz band which can be seen as a new frontier in the communication research. These challenges are treated in depth in this paper explaining the existing plethora of work and what still needs to be tackled.     

可调太赫兹与光学超材料

本文对可调太赫兹与光学超材料的研究进展进行了综述,并对其发展趋势和应用前景进行了展望。可以预见,可调超材料将继续成为超材料研究中的热点课题,并将成为引领光学器件和光学系统变革的潜在技术途径,对光学和太赫兹技术的发展将产生深远的影响。     

Terahertz (THz) Frequency Sources and Antennas - A Brief Review

In this paper we review THz radiation properties, generation methods, and antenna configurations. This paper suggests some new class of antennas that can be used at THz frequency, like optical antennas or Carbon nanotube antennas. THz technology has become attractive due to the low energy content and nonionizing nature of the signal. This property makes them suitable for imaging and sensing applications. But at the same time detection and generation of THz signals has been technologically challenging. This paper presents a comparative study of the generation techniques for THz frequency signals giving emphasis to the some new techniques like Quantum Cascade lasers which has created significant research interest. The main aim for this study is to find out the materials suitable for fabricating THz devices and antennas, a suitable method for generation of high power at THz frequency and an antenna that will make THz communication possible.     

Applications of Terahertz Spectroscopy in the Field of Construction and Building Materials

Abstract: In last two decades, rapid development in the field of terahertz (THz) technology has opened new possibilities for creating innovative imaging and sensing systems. Although the applications of THz technology in different sectors constantly increase, the construction industry lags behind them. The aim of this article is to review the current applications of THz spectroscopy in research and industry related to construction and building materials, along with the key drawbacks of technology and recommendations for future use. The review concludes that THz spectroscopy and imaging have promising potential and provide many opportunities for applications in construction and building materials characterization.     

利用3D打印技术制备太赫兹器件

高性能的太赫兹器件在控制太赫兹波方面起到重要的作用,因此寻求一种简单有效的太赫兹器件加工方案非常必要。本文以太赫兹波导和太赫兹滤波器为例,分别选用Kagome型光子晶体结构的波导和一维光子晶体结构的滤波器,运用商用的3D打印机加工样品,并采用透射式太赫兹时域光谱系统对样品的参数进行测量。实验结果表明:加工的波导在0.2~1.0 THz范围内传输损耗平均值约为0.02 cm~(-1),最小值可达到0.002 cm~(-1),且可运用机械拼接的方式将多个波导进行简单的连接从而获得更长的波导而不引起严重的损耗;滤波器的透射谱在0.1~0.5 THz之间有两个明显高损耗带;这两组实验结果均与理论预计非常接近。本文运用太赫兹波导和滤波器的实例证实了3D打印技术加工太赫兹器件的可行性,将会成为获取性能可控、价格低廉的太赫兹器件的有效途径。     

Review of the Novel Slow-Wave Structures for High-Power Traveling-Wave Tube

All-metal slow-wave structures are being paid great attention because of their advantages, such as good heat dissipation, high power capacity, wide passband, good wholeness of structure and large size etc. The emphases in this paper concentrate on the present state of study of four types of structures: helical groove, ring-plane, folded waveguide and periodically loaded waveguide, including theoretical analyses and practical applications. The problems and directions for future studies of these types of slow-wave circuits are also discussed. It is pointed out that all-metal slow-wave structures are suitable for applications in millimeter wave vacuum devices, like TWT, BWO, Gyro-TWT, and relativistic devices.     

玻璃衬底二氧化钒薄膜的宽频带太赫兹波调制特性

针对二氧化钒（VO2）薄膜在可调谐太赫兹功能器件中的应用, 采用磁控溅射法在K9玻璃衬底上制备了VO2薄膜, 并用X射线衍射（XRD）对薄膜的晶相进行表征。利用配备加热装置的太赫兹时域光谱系统（THz-TDS）研究了薄膜样品在变温过程中的THz反射、透射光谱特性及其变化规律。实验结果表明, 随着加热温度的升高, VO2薄膜发生半导体-金属相变并对宽频段THz波产生显著的调制作用。调制深度明显依赖于THz频率, 薄膜样品对THz波反射功率、透射率的幅度调制深度在0.3~0.5 THz范围波动较大;对THz波的透射率在低频处较大, 高频处较小, 调制深度在35%~65%之间变化。该薄膜制备简单, 质量高, 可应用于太赫兹开关和调制器等功能器件。     

二氧化钒薄膜低温制备及其太赫兹调制特性研究

针对二氧化钒(VO2)薄膜在可调谐太赫兹功能器件中的应用,利用低温磁控溅射技术,在太赫兹和光学频段透明的BK7玻璃上制备出高质量的VO2薄膜.晶体结构和微观形貌分析显示薄膜为单相VO2单斜金红石结构,具有明显的(011)晶面择优取向,结构致密,表面平整.利用四探针技术和太赫兹时域光谱系统分析了薄膜的绝缘体-金属相变特性,发现相变过程中薄膜电阻率变化达到4个数量级,同时对太赫兹透射强度具有强烈的调制作用,调制深度高达89％.通过电学相变和太赫兹光学相变特性的对比研究,证实薄膜的电阻率突变主要与逾渗通路的形成有关,而太赫兹幅度的调制则来源于薄膜中载流子浓度的变化.该薄膜制备简单,成膜质量高,太赫兹调制性能优异,可应用于太赫兹开关和调制器等集成式太赫兹功能器件.