电解质溶液的太赫兹透射特性研究

许多生物大分子的振动和转动能级都在太赫兹波段,且太赫兹波具有光子能量低,峰值功率高的特点,因此用太赫兹技术进行检测,能够从很大程度上保证生物分子不被破坏.然而,大部分的生物分子只有在水溶液中才能保持其生物活性,且水是极性分子,对太赫兹波有强烈的吸收,因此使用常规的太赫兹技术检测水溶液中生物样品的特性存在一定困难.设计了...     

连续太赫兹激光透射扫描成像实验研究

太赫兹成像可用于安检、反恐和工业生产等领域,已成为研究热点。由于连续太赫兹激光源体积较小、操作简单,因此,近几年对连续太赫兹激光成像的研究越来越多。基于C02激光泵浦甲醇气体生成的118．83μm激光,采用室温单元探测器、二维位移平台、聚乙烯透镜、光阑和计算机等器件组成的扫描透射成像系统对物体进行了成像实验,比较分析了扫描步长分别为1mm和0．5mm的成像结果。实验结果表明,由于增加光阑,实际成像功率下降,但此套成像系统在激光输出功率约为20mW时,仍成像清晰,且步长为0．5mm的成像效果更好。     

亚波长分形结构太赫兹透射增强的机理研究

利用太赫兹时域光谱(terahertz time domain spectroscopy,简称THz-TDS),研究了亚波长金属分形结构在THz波段的透射增强特性.分别从实验和理论两个方面,研究了铜箔上各级分形结构THz透射增强现象的产生机理.结果表明,在低频区的透射增强主要是由低级分形线中电子运动的共振引起的,而高频区的透射增强则主要由高级分形线中电子运动的共振引起的.从而将这种透射增强效应归结为分形结构中电子的共振辐射,即分形结构的局域共振效应. 关键词： 分形 太赫兹 透射 共振峰     

太赫兹波大气传输衰减模型

基于修正的Van-Vleck Weisskopf线型、辐射传输色散理论和水汽连续体吸收模型,结合HITRAN数据库,建立了太赫兹波大气传输衰减模型VVWH,形成了对宽频太赫兹波在真实大气中水平传输衰减的数值模拟能力。同时对太赫兹时域光谱技术（THz-TDS）获取的透射光谱实测数据进行了对比分析。计算结果与实验结果总体变化趋势一致,在吸收谱线处两者吻合良好,但在低频的大气窗口区,实验结果相比计算呈现出更强的传输衰减。考察了相对湿度对太赫兹波大气传输衰减特性的影响变化。     

宽带太赫兹波在大气中的远程探测研究及展望*

宽带太赫兹波由于具有传输容量大、速率高、方向性好、安全性高、散射小及穿透性好等许多特性,使太赫兹技术在高保密卫星通信、短距离无线通信等方面具有独特的优势。但是,如何克服大气中水蒸气的强吸收,找出适合太赫兹通信的频段,是发展宽带太赫兹远程传输亟待解决的问题。文章介绍了宽带太赫兹波在大气中远程探测的一些关键技术和最新研究成果,同时,对太赫兹通信技术的发展趋势和应用前景作了展望。     

光子晶体对太赫兹波的调制特性研究

利用传输矩阵方法研究了掺杂半导体n-GaAs/聚碳酸脂一维光子晶体的太赫兹波透射谱.研究结果发现,与一般由两种介电材料组成的一维光子晶体不同,由于掺杂半导体中自由载流子对太赫兹波存在较强的吸收,所以这种材料组成的一维光子晶体除可形成光子带隙外,还可以增强n-GaAs对太赫兹波的透射.同时还提出了一种基于这种一维光子晶体的太赫兹波调制器,通过外加电压控制半导体中电子浓度的大小可实现对太赫兹透射波幅度的调制. 关键词： 掺杂半导体光子晶体 太赫兹波 太赫兹波的调制     

太赫兹波通信技术研究进展

太赫兹波段位于红外和微波之间,在空间通信、近程战术通信等国防领域有巨大的应用前景。总结了太赫兹通信技术的特点、类别、方案及太赫兹波通信系统涉及的关键技术。介绍了近几年国内外太赫兹通信技术研究现状及取得的成果,在0.14 THz频段通信距离达到20 km,0.3 THz处通信传输速率高达105 Gb/s。分析了全电子学方法、光电子方法、量子级联激光通信等几种通信技术路线,并比较了各系统的优缺点。展望了太赫兹通信技术的发展趋势和应用前景。     

太赫兹大气传输特性实验研究

太赫兹在高速率通信、高分辨力雷达等方面具有广阔的应用前景,而对太赫兹辐射的大气传输特性及其规律进行系统的理论与实验研究则是发展利用该频谱资源的基础条件。对大气作用于太赫兹频段电磁辐射的吸收衰减进行了实验测试研究。通过双光路的差分系统设计,尽可能地减小太赫兹辐射源输出功率不稳定性所产生的系统误差,完成大气模拟环境下太赫兹波段多个频点传输的功率变化测定,以探索大气环境对不同频段THz波衰减的规律性;同时,建立太赫兹大气传输特性动态数据库对海量大气环境数据进行有效地分析,为实验数据处理及理论研究提供支持。收稿日期:; 修订日期:     

太赫兹大气传输特性实验研究

太赫兹在高速率通信、高分辨力雷达等方面具有广阔的应用前景,而对太赫兹辐射的大气传输特性及其规律进行系统的理论与实验研究则是发展利用该频谱资源的基础条件。对大气作用于太赫兹频段电磁辐射的吸收衰减进行了实验测试研究。通过双光路的差分系统设计,尽可能地减小太赫兹辐射源输出功率不稳定性所产生的系统误差,完成大气模拟环境下太赫兹波段多个频点传输的功率变化测定,以探索大气环境对不同频段THz波衰减的规律性;同时,建立太赫兹大气传输特性动态数据库对海量大气环境数据进行有效地分析,为实验数据处理及理论研究提供支持。收稿日期:; 修订日期:     

介质/金属结构太赫兹空芯光纤的传输特性

理论分析了金属、介质/金属结构空芯光纤在THz波段的模式结构和传输特性.金属空芯光纤支持TE11模式,介质/金属空芯光纤的介质膜厚在取最优值时支持HE11模式.对于波长为200μm的太赫兹波,内径为1 mm的两种空芯光纤,TE11和HE11模式的损耗分别为8.4 dB/m和2 dB/m.为优化介质/金属结构宅芯光纤的传输性能,分析了金属和介质材料的光学常数对衰减系数的影响.基于几种已发表的金属在太赫兹波段的光学常数,计算结果表明铝是最好的选择;初步测量结果显示,在各种树脂材料中聚乙烯在THz波段吸收较小,并且其折射率接近介质膜的最优值1.41,为太赫兹波空芯光纤中介质膜材料的理想选择.     

Broadband Terahertz Polarization Converter and Asymmetric Transmission Based on Coupled Dielectric‐Metal Grating

Coupled dielectric‐metal gratings are investigated for broadband terahertz (THz) wave polarization conversion and asymmetric transmission by the experiments and numerical simulations, which are composed of the subwavelength Si grating and metallic wire grating layers. The dielectric grating layer with a large artificial birefringence and low dispersion is employed as a phase engineered waveplate, and the metal wire grating arranged with a 45° angle to the dielectric grating is utilized as a high‐efficiency polarizer. Due to the subwavelength integration, this coupled grating presents a local resonance coupling mechanism between dielectric and metal gratings, which greatly enhances the polarization rotation and expands the bandwidth, not a simple combination with dielectric and metallic gratings. The results demonstrate that a broadband asymmetric transmission with an extinction ratio of 30dB from 0.2 to 1.2 THz is achieved and the highest transmission of 90% can be obtained. It provides a simple way towards practical applications for THz artificial dispersion materials, polarization control and asymmetric transmission.     

Giant Asymmetric Transmission and Circular Dichroism with Angular Tunability in Chiral Terahertz Metamaterials

Inspired by the chiral structure from mode interaction, a chiral terahertz metamaterial and its complementary structure with the coexistence of asymmetric transmission and circular dichroism response are designed. The asymmetric transmission happens in the presence of electric and magnetic modes perpendicular to each other, resulting from intrinsic chirality under normal incidence. Circular dichroism exists in the presence of electric and magnetic modes parallel to each other under oblique incidence because of extrinsic chirality. Both asymmetric transmission and circular dichroism are enhanced by complementary structures, benefitting from the coupling between adjacent units. The maximum of chiral parameter κ can achieve 450, which is one hundred times higher than previously reported. The chiral response can be tuned by the incident angle and is sensitive to the environmental refractive index. The results highlight the potential applications of these metamaterials in chiral sensing and polarization transformation devices.     

Investigation on Transmission Properties of Terahertz Wave Through Semiconductor Aperture

The transmission properties of terahertz （THz） wave passing through semiconductor aperture have been investigated. The dispersion relationship for surface plasmon polariton （SPP） at different temperatures has been numerically calculated. The results show that the dispersion relationship increases with the increasing of frequency and the decreasing of temperature, the thickness of slab has to be taken into consideration because of the large skin depth for semiconductor slab. In addition, the propagation constant increases with the increasing of frequency and the decreasing of temperature.     

Terahertz Transmission Spectroscopy of Nonpolar Materials and Relationship with Composition and Properties

Terahertz time-domain spectroscopy is used to study properties of non-polar materials. Terahertz absorption spectra and refractive indices are measured in a number of glasses, lubricating oils, and types of paper. The results are correlated with material properties.     

用于太赫兹波传输的低损耗、高双折射光纤研究

提出了一种同时具有低吸收损耗、高双折射特性的新型太赫兹传输光纤.光纤由层状的聚四氟乙烯和空气层组成.采用有限元法分析了光纤的结构参数对其吸收损耗和双折射的影响.结果表明:这种光纤的双折射可高达0.08;在保证模式的吸收损耗小于20 dB/m的前提下,其双折射仍可大于0.02. 关键词： 太赫兹传输 吸收损耗 双折射 有限元法     

Characteristic Attributes of Multiple Cascaded Terahertz Metasurfaces with Magnetically Tunable Subwavelength Resonators

The characteristics of multiple cascaded metasurfaces comprising H‐shaped, magnetostatically controllable, subwavelength terahertz (THz) resonators made of InAs were systematically investigated, using a commercial solver based on the finite‐integration method, for the design of tunable filters. Three configurations of the biasing magnetostatic field were compared with each other as well as with the bias‐free configuration for filtering of normally incident linearly polarized plane waves. A close study of only one metasurface was found sufficient to broadly determine the sensitivity to the direction of the magnetostatic field and the bandwidth of a stopband. Furthermore, the effects of metasurface geometry and biasing field can be considered separately for initial design purposes. All features in the transmittance spectra for the bias‐free configuration that are related to the number of cascaded metasurfaces are also observed when the biasing magnetostatic field is applied. The coupling of adjacent metasurfaces in a cascade is strongly affected by the relative permittivity and the thickness of the spacer between the two metasurfaces. The spectral locations of stopbands scale with respect to the spacer's relative permittivity, the scaling rule being different from a classical one. The stopbands are redshifted when the spacer thickness is increased, with the redshift dependent on the polarization of the incident plane wave. Inter‐metasurface coupling and inter‐resonator coupling on the same metasurface affect the spectral location of a stopband in opposite ways. On‐off type switching can be obtained by changing the orientation of magnetostatic field. The elucidated characteristics are expected to be important for not only filters but also other tunable THz devices.     

Simulation Investigation on Optical and Electrical Properties of Carbon Nanotube in Terahertz Region

Under the framework of Maxwell-Garnett （M-G） model, the optical and electrical properties of singlewalled carbon naotube （SWCNT）, double-walled carbon nanotube （DWCNT） and hydrogen-doped carbon nanotube （H-doped GNT） in terahertz （THz） region have been investigated. It has been found that as frequency increases the loss tangent and conductivity show a peak. The loss tangent and conductivity of SWCNT is larger than that of DWCNT and H-doped CNT. The loss tangent and conductivity increase with the increases of filling factor and the decreases of geometrical factor.     

黄曲霉毒素的太赫兹检测研究

为了探索能够快速简便、特异敏感的黄曲霉毒素检测方法,应用太赫兹时域光谱（THz-TDS）技术获得了黄曲霉毒素B1和M1在0．3～2．1THz范围内的吸收光谱,实验结果显示它们在测量波段范围表现出不同的吸收位置和吸收强度,表明THz波对它们结构的变化有灵敏响应。黄曲霉毒素在THz波段的指纹谱的测定显示出太赫兹时域光谱技术作为一种新的光谱研究手段具有用于黄曲霉毒素结构和功能研究的潜力,并为此技术应用于食品中黄曲霉毒素的检测奠定了基础。     

黄曲霉毒素的太赫兹检测研究

为了探索能够快速简便、特异敏感的黄曲霉毒素检测方法,应用太赫兹时域光谱(THz-TDS)技术获得了黄曲霉毒素B1和M1在0.3~2.1 THz范围内的吸收光谱,实验结果显示它们在测量波段范围表现出不同的吸收位置和吸收强度,表明THz波对它们结构的变化有灵敏响应。黄曲霉毒素在THz波段的指纹谱的测定显示出太赫兹时域光谱技术作为一种新的光谱研究手段具有用于黄曲霉毒素结构和功能研究的潜力,并为此技术应用于食品中黄曲霉毒素的检测奠定了基础。