太赫兹扩频测试系统的测试与分析

基于低频段的矢量网络分析系统,利用扩频模块进行频段扩展是现阶段实现太赫兹元器件有效测试的主要方法。本文针对太赫兹扩频测试系统的构成,结合测试结果进行了分析与评估,提出了改善太赫兹倍频测试系统性能的方法,并提高了测试系统的可检测动态范围。     

Soft Computing for Terahertz Metamaterial Absorber Design for Biomedical Application

The terahertz region of the electromagnetic spectrum plays a vital role in biomedical imaging because of its sensitivity to vibrational modes of biomolecules. Advances in broadband terahertz imaging have been emerging in the field of biomedical spectroscopy. Biomedical imaging is used to distinguish between the infected (cancer) and the non-infected tissue, which requires broad band and highly efficient radar absorbing material (RAM) designs (to obtain high resolution image of the tissue). In this paper, a metamaterial broadband RAM design is proposed towards biomedical spectroscopy applications in the THz region. The particle swarm optimization (PSO) algorithm is used for the design and optimization of the RAM, which enhances the absorption to nearly 99.32% at the required operational frequency.     

太赫兹近场光学亚表面检测技术研究

研究了太赫兹散射式扫描近场光学显微镜（Terahertz scattering-type scanning near-field optical microscopy,THz s-SNOM）对亚表面金属微纳结构的显微成像检测。首次采用自主搭建的THz s-SNOM系统对表面覆盖了六方氮化硼薄膜的金微米线进行太赫兹近场显微测量,获得了具有纳米量级空间分辨率和较高对比度的近场显微图。结合全波数值模拟,分析了THz s-SNOM探测亚表面金属微纳结构的空间分辨率、近场散射信号强度和成像对比度。研究表明,THz s-SNOM具有优良的亚表面显微成像检测能力,可应用于微纳电子器件的亚表面结构表征和缺陷检测。     

毫米波扩展互作用器件

扩展互作用器件是一种采用慢波谐振系统作为高频互作用电路的真空电子器件,是目前能够在毫米波亚毫米波段提供大功率输出的重要器件之一。本文给出了目前国内外毫米波亚毫米波段扩展互作用器件（EIK和EIO）技术的发展情况,并介绍了扩展互作用器件在毫米波亚毫米波段的技术特点和最新研究趋势。     

不断发展中的行波管技术

自从上世纪40年代第一支行波管改进以来,行波管技术不断发展,成为真空器件最重要的一个分支,并在各类军事与民用系统中发挥了重要的作用。目前行波管正朝着微/小型化、大功率和高频率三个方向发展。近年来,随着化学物半导体技术的发展,行波管受到固态器件的挑战,但是由于行波管所具有的宽频带、高功率、高效率及高频率工作的优点,在竞争中仍然具有生命力,还是军事和类似商业应用的主要产品。     

FDTD Simulation on Terahertz Waves Propagation Through a Dusty Plasma

The frequency dependent permittivity for dusty plasmas is provided by introducing the charging response factor and charge relaxation rate of airborne particles. The field equations that describe the characteristics of Terahertz(THz) waves propagation in a dusty plasma sheath are derived and discretized on the basis of the auxiliary differential equation(ADE) in the finite difference time domain(FDTD) method. Compared with numerical solutions in reference, the accuracy for the ADE FDTD method is validated. The reflection property of the metal Aluminum interlayer of the sheath at THz frequencies is discussed. The effects of the thickness, effective collision frequency, airborne particle density, and charge relaxation rate of airborne particles on the electromagnetic properties of Terahertz waves through a dusty plasma slab are investigated.Finally, some potential applications for Terahertz waves in information and communication are analyzed.     

太赫兹技术在水泥基材料研究中的应用

本文介绍了太赫兹波的特性以及太赫兹技术的工作原理及其应用,重点介绍了太赫兹时域光谱技术和太赫兹成像技术在水泥水化过程、水泥基材料的微观结构检测和水泥基材料耐久性能三方面的研究进展.利用太赫兹光谱技术可跟踪硅酸三钙、硅酸二钙以及主要水化产物水化硅酸钙、氢氧化钙在水化过程中的变化情况;利用水分对太赫兹波强烈吸收的特性,能够...     

Electrical and optical properties of MWNTs/HDPE composites in Terahertz region

Optical and electrical properties of composites,prepared by filling of high density polyethylene(HDPE) with two kinds of multi-walled carbon nanotubes(MWNTs) differing in diameters,were explored by terahertz time-domain spectroscopy(THz-TDS) in the frequency range from 0.2 to 1.6 THz.It is found that composite with larger-diameter MWNTs possesses larger absorption coefficient and conductivity at the same concentration.The real part of the ac conductivity of the composites follows a power law dependence on frequency.And the power index is around 0.75 regardless of the MWNT concentration and diameter.The experimental data were analyzed with Cole-Cole equation under the assumption that the conductive clusters dispersed in the polymer matrix behave like dipoles and contribute mainly to the dielectric loss.It is found that both of the composites have similar values of relaxation time and distribution parameter.With increase of the MWNTs concentration,the relaxation time increases and tends to saturate at 0.7 ps after passing through the percolation threshold.     

Terahertz Schottky barrier diodes with various isolation designs for advanced radio frequency applications

High performance nanometer NiSi2-Si Schottky barrier diode arrays (SBDA) with various isolation designs, including poly Si gate (PSG) and resist protection oxide (RPO), are developed for advanced radio frequency applications. Radio frequency performances of these developed SBDAs are investigated and compared to that with the conventional shallow trench isolation. All of the SBDAs are fabricated with a foundry state-of-the -art 45 nm complementary metal oxide semiconductor technology. Both of PSG and RPO insulated SBDAs have higher cutoff frequency and a simpler preparation process. Specifically, the PSG insulted SBDA could achieve a cutoff frequency of up to 4.6 THz.     

Techniques for cancellation of interfering multiple reflections in terahertz time-domain measurements

Algorithms are described which allow a significant reduction of the effects of multiple pulses, which originate from pulse reflections within terahertz (THz) emitters. The algorithms are based on models for the pulse propagation inside the emitter. Model parameters can be estimated from a calibration experiment using a reference signal in the absence of a sample. The parameters once estimated for a particular emitter device, can then be used to suppress the effects of multiple pulses in all measurements performed with the same emitter. The application of this method is demonstrated in the investigation of a disc sample and in the investigation of a paint layer.